Ricki Lewis, PhD

Cell phones came to the United States in 1984, and they're here to stay. By 1999, 86 million of them were in use; by 2000, 92 million were; and by 2005, nearly 195 million were in use, according to the Washington, DC-based Cellular Telecommunication Industry Association. A half billion of the gadgets are used worldwide.With such pervasive use of a radiation-emitting device-and considering the length of time some people spend with phone to ear-it isn't surprising that health concerns that focus on the impact of cell phones on the brain have arisen. Cell phone safety has become a field unto itself and has generated many published studies. "To my mind, it was clear from the very beginning that the introduction of a new technology has to be accompanied by research to identify potential health risks," said Joachim Schuz, PhD, head of the Department of Biostatistics and Epidemiology at the Institute of Cancer Epidemiology in Copenhagen.Cell phones emit radiofrequency signals of 850 to 1900 megahertz, which does not damage DNA or other cellular structures because it is not ionizing radiation. Although high-powered radiofrequency waves can heat tissue, as they do in microwave ovens with 600 to 1100 watts of power, the 0.6 wattage of the average cell phone poses little danger. Still, the hypothesis that extended cell phone use increases the risk of a brain tumor has been extensively examined.A prominent example of research into cell phone safety is the Interphone Project. This project, of international scope and including 13 nations that are conducting large-scale population-based case-control studies that follow the same design, is comparing cell phone use among people who have malignant or benign brain tumors with matched controls. Odds ratios are being examined to see whether a relationship exists between cell phone use and tumorigenesis.A CNN report on a 1993 lawsuit catalyzed current concern over cell phone use. "The initial event was a Larry King interview with a Florida man named David Reynard, who alleged that his wife's brain tumor was due to cell phone use," said Joshua E. Muscat, PhD, MPH, an associate professor in the Department of Health Evaluation Sciences at the Pennsylvania State Cancer Institute. Reynard sued several phone companies but could not amass enough evidence to win. Three years later, the first large study of cell phone safety emerged, finding no increase in overall mortality.1 As cell phone use became pervasive, investigations continued.Studies show no elevated risks for glioma or meningioma among cell phone users,2,3 but risk of acoustic neuroma is slightly higher among such persons.4,5 However, researchers urge caution in interpreting data. "Acoustic neuromas and gliomas and meningiomas are different histopathologically and anatomically and are likely to have different causes. Therefore, it is not remarkable that the risk patterns differ for the different tumor types," said Patricia McKinney, PhD, a professor of pediatric epidemiology at the Leeds Institute of Genetics, Health, and Therapeutics, University of Leeds, United Kingdom. In addition, acoustic neuromas are closer to the radiation source than the other types of tumors, she added. Peter Inskip, ScD, senior investigator at the National Cancer Institute's Division of Cancer Epidemiology and Genetics, agrees. "I am not convinced of an increase in risk for acoustic neuroma. Because the radiofrequency energy drops off very quickly with depth in tissue, the deeper parts of the brain receive very little exposure."Some of the studies also stratified participants by duration of cell phone use because of the long latency for cancer. The already-published German Interphone investigation3 indicates an elevated risk for glioma and meningioma after 10 years of cell phone use but found no overall increase in risk. The researchers, therefore, are calling for confirmation of their findings. Nevertheless, ongoing investigations may be required to uncover long-term effects of cell phone use and cancer risk. "There is no biological basis to predict how long it takes for a hypothetical effect of cell phone radiation to cause brain cancer. So studies with limited exposure periods-less than 10 years-provide empirical data that limited exposures do not increase the risk," said Muscat. "I think it is justified to establish a monitoring system for long-term effects for a technology that is used by virtually everyone in most developed countries," Schuz agreed.RICKI LEWIS, PHD, a geneticist, textbook author, and freelance writer in Scotia, NY, is a contributing editor for Applied Neurology.REFERENCES1. Rothman KJ, Loughlin JE, Furch DP, Dreyer NA. Overall mortality of cellular telephone customers. Epidemiology. 1996;7:302-305.2. Hepworth SJ, Schoemaker MJ, Muir KR, et al. Mobile phone use and risk of glioma in adults: case-control study. BMJ. 2006 Jan 20; [Epub ahead of print].3. Schuz J, Bohler E, Berg G, et al. Cellular phones, cordless phones, and the risks of glioma and meningioma (Interphone Study Group, Germany). Am J Epidemiol. 2006;163:512-520.4. Inskip PD, Tarone RE, Hatch EE, et al. Cellular-telephone use and brain tumors. N Engl J Med. 2006;344:79-86.5. Lonn S, Ahlbom A, Hall P, et al. Long-term mobile phone use and brain tumor risk. Am J Epidemiol. 2006;161:526-535.

Articles

brain tumor, neuroma, tumorigenesis, cell phone use

Cell Phones vs Brain Tumors: Can You Hear Me Now?

Selective serotonin reuptake inhibitors, SSRIs, Suicidality, Depression, Major depressive disorder, Neonatal abstinence syndrome

Antidepressants: The Risk/Benefit Saga Continues

cognitive enhancement, cosmetic neurology

Neural Enhancement: A Slippery Slope for Neurologists

Rigidity and dystonia in Huntington disease (HD) are associated with atrophy of the caudate nucleus and putamen (B). Extensive neuronal loss and gliosis in the cerebral cortex (A,C) in both HD and Alzheimer disease (AD) are responsible for varying degrees of cognitive impairment (however, neurofibrillary tangles and senile plaques are seen only in AD).

Understanding a rare genetic disorder can lead to treatments for more common conditions. The one-in-a-million children with familial hypercholesterolemia, for example, spearheaded development of the blockbuster statins. In neurology, study of rare familial variants of Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis (ALS), and even prion disorders revealed molecular targets for drug discovery.

For HD, however, the genes-as-a-guidepost strategy fails, because HD has no common counterpart. It is a disorder of information overload--a gene too long, a complex cellular derangement with many entangled and interacting components. "Parkinson disease is a deficiency of 1 chemical that can be replaced--we can increase availability of dopamine or mimic its effects. HD isn't that simple," said Kathleen M. Shannon, MD, director of the Huntington's Disease Center of Excellence at Rush University Medical Center in Chicago.

HD stands out even among the single-gene disorders in its strangeness. Unlike the others, homozygotes for the HD mutation are no worse off than the more common heterozygotes. Also highly unusual, penetrance approaches 100%--if you inherit the gene and live long enough, you get the disease. Yet its rarity stymies progress.

"There's no easy answer, at least for now, to the question of why HD has been so difficult to understand and treat," said Allan J. Tobin, PhD, professor of neurology at University of California, Los Angeles, and senior scientific advisor to the High Q Foundation, a New York City-based private philanthropic organization that coordinates academic, industrial, government, and private efforts to develop treatments for HD. "High Q" refers to the high numbers of glutamine (symbolized as "Q") repeats in the abnormal huntingtin (htt) protein in HD (Table 1 lists polyQ diseases.) "The question is whether there's a single pathogenic cascade, or many parallel, interacting ones," Tobin added.

The goal of disentangling the mechanistic threads that weave the fabric of HD is to identify drug targets--and that's already happening. Two drugs are in clinical trials: tetrabenazine (marketed in Canada and Europe as Nitoman by Prestwick Pharmaceuticals) and ethyl-eicosapentaenoate (ethyl-EPA; Miraxion, Amarin Neuroscience). Two are commonly used to manage symptoms: haloperidol and clonazepam. 

A project called Systematic Evaluation of Treatments for Huntington's Disease (SET-HD) has identified 40 initial candidates from the existing pharmacopeia and has evaluated 24 (see www. huntingtonproject.org and Table 2). And the European Rare Diseases Therapeutic Initiative (ERDITI; www.erditi.org) is seeking new treatments among drug candidates for common disorders that never made it to market. With 10 research institutions and 4 large pharmaceutical companies on board, ERDITI is matching basic researchers with big pharma's stockpile.

Meanwhile, the role of the neurologist in treating HD isn't restricted to the prescription pad. A neurologist can do "a lot," said Karl Kieburtz, MD, MPH, professor of neurology and community and preventive medicine at the University of Rochester in New York. Information can help, such as stressing the variability of the disease. "Some people see their parents and think that they will suffer in the same exact way. Explain that, between members of a family, the disease can look very different," he added. In one family, age at onset across 3 generations varied by 50 years. Also within families, motor, cognitive, and behavioral symptoms can occur in different orders and to different degrees.

Other specialists can help too. Genetic counseling is critical in presymptomatic testing. A speech pathologist can teach caregivers to recognize the distinct limitations in mechanical speech and cognitive processing in HD and provide practical ways for patients to communicate, even past when the patient would otherwise be able to do so, suggested Jeff Searle, MS, of the Department of Hearing and Speech at Kansas State University Medical Center. Caregivers can find creative ways to ease suffering (see accompanying article, "HD and Music").

The Huntington's Disease Society of America has designated 21 Centers of Excellence, where patients and their families can receive multidisciplinary care and support. "The center is a place where HD patients and families can go for one-stop shopping--a neurologist, psychiatrist, psychologist, social worker, speech therapist, physical therapist. A lot of different services in 1 place is valuable because it is difficult to move people with HD around," said Shannon.

Shannon calls HD "a triple barrel disease," with its motor, behavioral, and cognitive components. In the 1970s, "disease" replaced "chorea" in recognition of the more subtle nonmotor symptoms. HD often begins gradually, and almost imperceptibly, as fidgeting becomes more frequent and progresses to larger movements. Hands wave, feet tap, in endless, apparently purposeless patterns. As the person loses the sense of the body in space, clumsiness sets in, with frequent bumping into things. The symptoms change as neurons die.

At first, a person may drop items as the brain cuts short a grasping movement. Later on, such a movement can't be willfully stopped and a sudden kick may inflict damage. The paradox continues when movement ceases in the final months.

Joe Klein vividly captured the motor decline of HD in his biography, 

. The famed folksinger died in 1967. Wrote Klein, "The little twitches and shakes had become gross, unpredictable lurches of his arms and legs and torso. Despite heavy medication, he was in constant motion. The worst of it seemed to be his right arm, which would fly up and strike his forehead with such force that sometimes, when they hadn't clipped his nails at the hospital, he'd gash himself with his thumb and blood would pour down his face."

Behavioral and emotional changes are highly individual. They may include mood swings, depression, anxiety, antisocial behavior, or aggression or abusiveness. Perhaps the frustration about waning cognitive skills catalyzes the emotional changes. Before and if dementia occurs, the intellect is intact, but mentation is compromised. Multitasking is nearly impossible. Organizing thoughts well enough to initiate or sustain conversations becomes difficult. For example, changing the topic during conversation can provoke utter confusion. Also, short-term memories fade fast.

"Horse and buggy doctor" George Sumner Huntington first described the disorder that would take his name in 1872.

 As a boy in eastern Long Island, George accompanied his father and grandfather, both physicians, as they visited patients, including 2 skinny women who were contorted grotesquely and various men who walked as if drunk.

After moving to Ohio, Huntington presented his thoughts and observations about these patients at a medical meeting, calling the condition "hereditary chorea" and noting the late onset and associated mental disturbance. In stating that the "thread is broken" after a generation thrives without the manifestation of the disease, Huntington displayed an intuitive grasp of autosomal dominant inheritance 3 decades before Mendel's laws were rediscovered. 

His report drew attention, and others continued to study the extended families of Huntington's affected patients from Long Island. Eventually, more than 1000 cases over 12 generations were identified, and the hereditary disease was traced back to 2 brothers from Suffolk, England.

Studies of other large families would prove crucial to current understanding of HD. In 1979, Columbia University psychologist and Hereditary Disease Foundation president Nancy Wexler, PhD, began yearly treks to the shores of Lake Maracaibo, Venezuela, where HD affected so many members of a 10-generation family of 18,149 that HD-HD marriages occurred. Offspring of these pairings provided the clue that the mutation caused a "gain-of-function" rather than disrupted function, because individuals with 2 copies of the mutant gene were no worse off than those with 1 copy. Plus, the mutant gene was altered, not absent. Wexler regularly exchanged blue jeans and M&M candies for blood samples from members of this family, who grew to love her, and these samples led directly to discovery of a genetic marker. A large family from Iowa added key data.

The marker was a tightly linked single nucleotide polymorphism that within certain families traveled exclusively with the sick individuals.

 The test required the participation of several family members to track the inheritance pattern. The test became commercially available in 1986, ushering in the era of presymptomatic testing and its bioethical implications.

Wexler, whose family has HD, compared the dilemma with the blind seer in 

 who says, "It is but sorrow to be wise when wisdom profits not."

 The genetic marker became instantly obsolete with the discovery of the disease-causing gene. This took a decade because the repeat-riddled gene lies out on the tip of the long arm of chromosome 4, complicating genetic analysis.

 With a direct gene test, anyone could be tested.

Today, neurologists dominate the annual pilgrimage to Lake Maracaibo. They are tracking the subtleties of variations in disease onset and progression.

A disease pathology is usually clarified by the discovery of a protein, the absence or aberration of which underlies the disease, but HD presents a more complicated picture. The HD mutation is an expanding triplet repeat. At one end of the gene, the DNA sequence CAG repeats fewer than 34 to 37 times in persons without HD and more than 37 to 40 times in those with the disease. Individuals in the gray area have mild symptoms. In general, the longer the repeat, the earlier the onset, but it isn't yet possible to predict age at onset based on repeat number.

Normal-length htt binds brain-derived neurotrophic factor (BDNF) by interacting with htt-associated protein (HAP-1) and dynactin, a motor molecule. When BDNF cannot travel along nerve fibers, neurons die. Because embryos of a mouse model of HD die when normal htt is inactivated, the disease develops from lack of the normal protein as well as accumulation of abnormal htt.

The actions of mutant htt, however, are many and complex. It binds a host of other proteins and, in so doing, wreaks havoc on a cell, disrupting transcription factors, impairing endocytosis and axonal transport, and hampering the ubiquitin-proteasome system, thereby clogging the cell with bits of aggregated protein. Levels of neurotrophins fall as glutamate excitotoxicity rises. Mitochondria leak calcium, presaging apoptosis.

Given such a convoluted etiology, with cause and effect blurred in a cascade of malfunction, research often glimpses parts of the big picture. For example, Ilya Bezprozvanny, PhD, associate professor of physiology at the University of Texas Southwestern Medical Center at Dallas, showed, using mouse models of HD, that the toxic gain of function could be binding of mutant htt to InsP3R1 (a receptor for the signaling molecule inositol) and NR2B (a glutamate receptor) on mitochondria.

"The connection between glutamate signaling and calcium overload is specific for HD. I think the expanded htt adapts a conformation that stimulates InsP3R1 and NR2B, leading to calcium overload," he said. His group is studying drugs that affect calcium release from mitochondria, including the anticoagulant enoxaparin (Lovenox, Sanofi  Aventis), the antidepressants nortriptyline and desipramine, and the antipsychotic trifluoperazine.

Much effort is directed at another puzzle, the protein aggregates found in the brains of people who inherited the mutant gene but died of other causes before symptoms began. "We don't know if the protein aggregates are pathological or protective. That is a raging debate," said Mark Forman, MD, PhD, assistant professor of pathology and laboratory medicine at the University of Pennsylvania. As for connecting all the mechanistic dots, "Nobody is even close to putting it all together," he added.

The complexity of HD continues macroscopically. Mutant htt is widely synthesized throughout the brain and even in the skin. Yet only some cells die. The "selectively vulnerable" areas are the g-aminobutyric acid-producing medium-sized spiny neurons in the putamen and caudate and cortical pyramidal neurons. Studies with a mouse model that can turn the polyQ part of the mutant gene on or off suggested that this widespread expression is necessary for disease: restricting the damage leads to protein aggregation, but not the motor symptoms or cortical pathology.

 Full-fledged disease occurred only with global brain expression. The restricted response to global insult reverberates at higher levels. "There are defensive responses, both of cells and systems, so by the time someone gets sick, there have been lots of changes and something just gives," Tobin explained.

Perhaps the best news about HD comes at the population level. Recent research on the Venezuelan families has focused on the shades of gray of the illness--variability in age at onset and course of the symptoms.

 Statistical analyses reveal that the mutant gene exerts only a partial effect. For people with the longest repeats, the gene accounts for 72% of the variance in the age at onset, but for those with shorter repeats, the gene accounts for 44%. The implication is that other genes or environmental factors influence how many disease-free years a person will have. The same may be true of symptom severity and the pace of pathogenesis. Further evidence for an environmental connection comes from comparing populations. The average ages at onset in Venezuela, the United States, and Canada are 34.35, 37.47, and 40.36 years, respectively.

A source of intense worry to HD family members is anticipating when and how the disease will start, whether tapping a foot or twisting a lock of hair is the beginning of the end, particularly for people who know they have inherited the mutant gene. Biomarkers are measurements that can detect the first inklings of illness and monitor progression. Biomarkers include following patterns of gene expression and small molecules in plasma, urine, and cerebrospinal fluid; cognitive tests; brain imaging; eye tracking; and motor studies.

Several biomarker investigations are under way. Researchers at Harvard Medical School have correlated cortical thinning among patients with presymptomatic HD with cognitive decline

 and identified a dozen genes whose expression is significantly elevated in HD patients and increases as the disease progresses.

 Expression of these genes fell after patients took sodium phenylbutyrate for 4 weeks. This drug is an inhibitor of histone deacetylase, the enzyme that enables DNA to be transcribed, a process that mutant htt represses.

Several large-scale investigations are identifying early signs and are tracking the course of the illness. The Prospective Huntington At Risk Observational Study (PHAROS) is tracking first signs among 1001 at-risk individuals, aged 26 to 55 years, at 43 clinical sites. Participants do not know their HD status. The National Institute of Neurological Disorders and Stroke and the National Human Genome Research Institute fund PHAROS. The High Q Foundation supports the Huntington Study Group's Cohort project and the European HD Network's Registry, which will collect clinical data and biological samples from HD patients yearly for longitudinal assessments.

At the San Francisco VA Medical Center, Clinical Assistant Professor of Neurology Stephen Massa, MD, PhD, and his group are looking at the effects of clioquinol on mice and human cells in culture (see also, "Controversial Antibiotic Shows Utility in Treating Huntington Disease, 

November 2005, page 42). This antibiotic is a copper/zinc chelator that has been banned for internal use in the United States since 1971 because its use resulted in subacute myelo-opticoneuropathy among thousands of Japanese in the 1960s.

 supplementation prevent this side effect, and because the drug chelates amyloid b, the researchers decided to try it for HD. Treated mice lived 20% longer, had better motor coordination, lost less weight, and had a 4-fold decrease in protein aggregation compared with controls. Cells in culture stayed alive longer and accumulated less protein.

The selective serotonin reuptake inhibitors may smooth mood in HD patients. Paroxetine (Paxil, GlaxoSmithKline) made it to SET-HD's first list of drug candidates after mouse experiments showed delayed symptoms and improved motor skills and survival. Fluoxetine (Prozac, Eli Lilly) demonstrated similar effects in a mouse model.

, part of the electron transport chain in mitochondria, is still in the running after a study that showed a "favorable though not statistically significant trend toward slowing disease progression" at 600 mg/d.

 Transient decreases in lactic acid in the cortex supported the rationale that the compound improves mitochondrial function. Current investigations are testing higher doses. "Coenzyme Q

 is useful for modifying the course of the illness, as opposed to improving symptoms in the short term," said Kieburtz.

Surveying existing drugs also has led to disappointments. Negative results for riluzole (Rilutek, Sanofi Aventis), which moderates glutamate toxicity and is used to treat ALS, were just announced at the World Congress on Huntington's Disease in Manchester, UK.

Top on many lists for most promising drug is tetrabenazine, which has been marketed in Europe for years. The drug binds the type-2 vesicular monoamine transporter and improves chorea. "It has a high likelihood of success, but no one has ever picked it up here because it's a small market," said Kieburtz.

A candidate with mixed success is ultra-pure ethyl-EPA, a semisynthetic derivative of the fatty acid EPA, being developed as Miraxion at Amarin Neuroscience in Stirling, UK.

 Ethyl-EPA lowers levels of caspases in mitochondria and thus could prevent neuronal apoptosis. It is effective in mitochondrial disorders and seems promising in case reports and pilot studies. However, a phase 3 clinical trial found improved motor skills on one scale but not another, and use of the compound actually worsened behavioral symptoms in a subset of patients.

Perhaps the strangest new approach to treating HD is what its inventors call "choroid plexus sushi." NeurotrophinCell, from Living Cell Technologies in Providence, RI, consists of pig cells wrapped in seaweed, the effects of which have been studied in the striatum of a primate model. The pig cells, from the choroid plexus, secrete a protein "protection cocktail" that the researchers said decreased cell death from 50% to 10%. "We are working in conjunction with Mother Nature," said Chief Scientific Officer Dwaine Emerich, PhD.

A little over half a century ago, Woody Guthrie, who lent a name and voice to HD, began to recognize in himself the signs he knew all too well from his mother. Wrote he, "Huntington's chorea means there's no help in the science of medicine for me, and all you Choreanites like me . . . there is just not no hope nor not no treatment known to man to cure me."

Guthrie's mother, Nora Belle, had taught Woody and his 4 siblings the songs of their home, Oklahoma, singing often of dust storms and tornadoes. More recently, a caregiver evoked a telling comparison of the disease to a tornado: like the storm, HD strikes seemingly at random, felling one individual but not the next, cutting a swath of twisted destruction through a brain, and through a family. Although the current state of HD research may seem like a maelstrom of effects and derangements, perhaps when the pieces are assembled, in place and time within the cell, a way to halt the pathology triggered by the triplet repeats will emerge.	*

2. Gusella JF, Wexler NS, Conneally PM, et al. A polymorphic DNA marker genetically linked to Huntington's disease. 

3. Wexler NS. The Tiresias complex: Huntington's disease as a paradigm of testing for late-onset disorders. 

4. A novel gene containing a trinucleotide repeat that is expanded and unstable on Huntington's disease chromosomes. Huntington's Disease Collaborative Research Group. 

5. Gu X, Li C, Wei W, et al. Pathological cell-cell interactions elicited by a neuropathogenic form of mutant huntingtin contribute to cortical pathogenesis in HD mice. 

6. Wexler NS, Lorimer J, Porter J, et al. Venezuelan kindreds reveal that genetic and environmental factors modulate Huntington's disease age of onset. 

7. Rosas HD, Hevelone ND, Zaleta AK, et al. Regional cortical thinning in preclinical Huntington disease and its relationship to cognition. 

8. Borovecki F, Lovrecic L, Zhou J, et al. Genome-wide expression profiling of human blood reveals biomarkers for Huntington's disease. 

9. Nguyen T, Hamby A, Massa SM. Clioquinol down-regulates mutant huntingtin expression in vitro and mitigates pathology in a Huntington's disease mouse model. 

10. Grote HE, Bull ND, Howard ML, et al. Cognitive disorders and neurogenesis deficits in Huntington's disease mice are rescued by fluoxetine. 

11. Huntington Study Group. A randomized, placebo-controlled trial of coenzyme Q

 and remacemide in Huntington's disease. 

12. Hockly E, Tse J, Barker AL, et al. Evaluation of the benzothiazole aggregation inhibitors riluzole and PGL-135 as therapeutics for Huntington's disease. 

13. Puri BK, Leavitt BR, Hayden MR, et al. Ethyl-EPA in Huntington disease: a double-blind, randomized, placebo-controlled trial. 

Huntington disease, neurogenetics, George Sumner Huntington, Systematic Evaluation of Treatments for Huntington's Disease, Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis

Huntington Disease: The Orphan Enigma

Glial cell line­derived neurotrophic factor (GDNF) for the treatment of Parkinson disease continues its roller-coaster trajectory (see Parkinson Disease: The Ups and Downs of Developing Therapies, 

 April 2005, page 11). Evidence of dopamine production and nerve fiber sprouting in the brain of a deceased clinical trial participant

 came hot on the heels of a legal setback for 2 other trial participants who are suing Amgen Inc in an effort to continue receiving the controversial treatment.

In April, Richard Suthers of Greenlawn, NY, and Niwana Martin of Harpers Ferry, WV, filed suit, seeking a preliminary injunction to obtain GDNF from Amgen while legal proceedings continue. But on June 6, a judge in a US district court in Manhattan ruled against the patients, writing that their relationship was with New York University, which ran the clinical trial, and not the company.

Just 1 month after the judge's preliminary ruling, the autopsy report was released of a 62-year-old man treated for 43 months with continuous direct-brain infusions of GDNF. The man had died of a heart attack 3 months after Amgen halted clinical trials in September 2004 in response to lack of effect in treated monkeys. The man had been 1 of 5 patients in an open- label trial begun in 2001 by Steven S. Gill, FRCS, and colleagues at the University of Bristol Institute of Clinical Neuroscience at Frenchay Hospital in the United Kingdom. This trial

 was the inspiration for the larger trial in which Suthers and Martin had participated. All of the initial 5 patients improved.

Seth Love, MBBCh, PhD, a neuropathologist at Frenchay Hospital, led a team that analyzed the brain of the patient who died of a heart attack. Because the man had left hemiparkinsonism, GDNF had been delivered to his right posterodorsal putamen. He therefore served as his own control. At and until 24 months, the Unified Parkinson's Disease Rating Scale showed a 38% improvement during the "off" medication period for both sides, as well as an 18% increase in uptake of 18F-dopa in the entire putamen and 91% in the posterior one third of the putamen. In the uninfused side, a 7.4% decrease in uptake in the entire putamen was seen, and related motor scores declined after 24 months.

Autopsy revealed the catheter track, with some clustering of astrocytes but inflammation only at the tip, amid histologic hallmarks of Parkinson disease. Labeled antibodies to tyrosine hydroxylase, the rate-limiting enzyme in the dopamine biosynthetic pathway, were 5-fold more concentrated in the right posterior putamen than in the corresponding, nontreated region on the left. Strong expression of growth-associated protein 43 on the right side of the posterior putamen suggested nerve fiber sprouting in the substantia nigra.

"This report is of great interest to neurologists and scientists who work in this field because it does demonstrate that GDNF is having an effect on the dopamine system in the brain of a patient with Parkinson disease. But as the authors point out, it is unclear what the finding actually means in terms of whether or not GDNF promotes neuronal growth in humans," said William J. Weiner, MD, director of the Maryland Parkinson's Disease and Movement Disorders Center at the University of Maryland School of Medicine in Baltimore, referring to Love and his team, which includes Gill. A sense of déjà vu lurks in the background, recalling the fetal transplant work of the late 1990s that also showed sprouting but "did not translate into benefit for Parkinson patients," Weiner added.

Love and colleagues worded their conclusions guardedly. Although they call this work the first evidence of sprouting of dopaminergic fibers, they offer 2 hypotheses to explain the tyrosine hydroxylase distribution: either the sought-after resprouting, or up-regulation to compensate for malfunctioning nerve fibers. The man's progress was similar to that of the other 4 participants in the open-label trial.

1. Love S, Plaha P, Patel NK, et al. Glial cell line-derived neurotrophic factor induces neuronal sprouting in human brain. 

2. Gill SS, Patel NK, Hutton GR, et al. Direct brain infusion of glial cell line­ derived neurotrophic factor in Parkinson disease. 

The Continuing Saga of GDNF and Parkinson Disease

ALS begins vaguely--with a twitch or sudden clumsiness. For Jenifer Estess, whose remarkable book 

 chronicles her battle against ALS, the first symptoms were difficulty in doing sit-ups and in standing up, and a heavy sensation when holding a towel. Wildly fasciculating thigh muscles led her to seek medical help. For soap opera actor Michael Zaslow, ALS initially garbled his speech so much that he soon lost his job--but he resurfaced on a different daytime drama, in which the powers-that-be wrote ALS into his character, calling much-needed attention to the disease.

Estess had the limb-onset form of the disease, and Zaslow the bulbar form, which affects about 25% of patients. In both forms of ALS, upper and lower motor neurons, as well as astrocytes and microglia  eventually die.

"It is a neurodegenerative disease of the motor neurons, throughout the system. People die because they lose control of the upper airways," said Nicholas Boulis, MD, a neurosurgeon at the Cleveland Clinic, who is investigating ways to treat the spinal cord directly. It is a more profound disturbance than other neurodegenerative disorders. "When you steer a car, the steering wheel directly connects to the wheels, but if there is power steering, movement is modulated by circuits that make it easier. Huntington disease and Parkinson disease are like the power-steering circuits; ALS is the direct-drive 

. No matter what, you don't get output," explained Jeffrey Rothstein, MD, PhD, director of the Packard Center for ALS Research and professor of neurology and neuroscience at Johns Hopkins University.

Despite the fact that ALS seems to combine the worst aspects of all neurodegenerative diseases, optimism and effort in the ALS community are inspiring. "We're a small disease, but we move quickly from lab to trial," said Rothstein. Boulis is hopeful for another reason: "ALS presents a defined territory that is critical to extend life: the upper airways. In many ways ALS is more accessible than a spinal cord injury or Alzheimer disease, which is a far more diffuse disorder."

Still, ALS presents daunting hurdles. Gradual onset attenuates diagnosis, but progression comes so fast that clinical trials cannot run as long as those for other neurodegenerative disorders. The mind remains relatively intact without treatment as the ability to move ebbs. Many treatments have failed, the disease's rarity does not invite investment, and the first animal model has been, by many accounts, disappointing. Perhaps the greatest challenge stems from the many mysteries surrounding ALS.	

A rare, poorly understood disorder with subtypes could be a research nightmare. "ALS is a phenotype, like stroke. How did you get there? There may be a very pure form with only motor impairment and a complicated variant with cognitive or sensory problems," said Michael Strong, MD, the Arthur Hudson chair in ALS Research at the University of Western Ontario. Mary Abood, PhD, a research scientist at California Pacific Medical Center, San Francisco, agrees: "Part of the reason it is so difficult to show efficacy in clinical trials is that some people decline more rapidly than others because of a different etiology. A drug being tested may be efficacious against one form but not another."

Identifying environmental triggers and inherited susceptibilities that may underlie ALS subtypes has been problematic. For example, 2 studies found that the incidence of ALS among veterans of the first Gulf War is significantly higher than the incidence among military personnel who were not deployed to the Gulf; however, risk factors have not been isolated.

 While the possible roles of chemicals from burning oil fields, vaccines, and exposure to unusual pathogens were being contemplated, another, more recent study that looked at incidence in association with military endeavors found elevated rates of occurrence among persons who served in the military at any time than among those who did not.

 The association, then, may be more with military service in general than with time or place of military activity.

A clearer environmental link comes from the native Chamorro people of Guam, where the incidence of a trio of neurodegenerative diseases--ALS, Parkinson disease dementia, and a combination of these--peaked shortly after World War II, affecting nearly 10% of the population. After the NIH ruled out a clear genetic pattern, attention turned to environmental triggers. A combination of folklore and logic led, in the 1960s, to the seeds of cycad trees. Consumption of seeds from the cycad tree increased when other foods became scarce during wartime.

In the early 1980s, researchers identified a possible neurotoxin: the amino acid beta-

-methylamino-levo-alanine (BMAA), which resembles an amino acid linked to an ALS-like illness prevalent in India and is similar to the excitatory neurotransmitter glutamate. However, it was present in cycad seeds in parts per million--not enough to affect the human CNS--but biologic detective work solved the puzzle.

In 2003, Paul Cox of the Institute for Ethnobotany in Kauai, Hawaii, and Oliver Sacks, BM, BCh, at the Albert Einstein College of Medicine in New York, painted a plausible ecologic scenario of biomagnification: cyanobacteria produce BMAA in the soil, which cycad roots tap. Then, bats called flying foxes eat cycad seeds and concentrate the neurotoxin in their tissue, just as fish concentrate mercury. World War II brought guns to the Chamorro, which enabled them to blast dozens of the delectable bats from trees--easy targets with neurotoxin-slowed reflexes. Dining on bats could have poisoned the Chamorro people.

To follow up on an ALS-environmental link, in 2004, the Agency for Toxic Substances and Disease Registry, part of the US Department of Health and Human Services, launched an effort at hazardous waste sites in 5 states to see whether ALS incidence had increased in their vicinity. The first results, reported in May 2005 from Kelly Air Force Base in Bexar County, Texas, found no additional cases.

Evidence for an infection connection also is weak. Anecdotal reports blame Lyme disease for misdiagnosis, but the differential diagnosis of Lyme disease is easily ruled out, Rothstein said. Viruses have been implicated too, at first based on the similar effects of poliovirus, and more recently, with the detection of increased levels of reverse transcriptase, a retroviral enzyme, in ALS patients.

If environmental data are sparse, molecular clues are perhaps too diverse. ALS is associated with at least 9 different genetic variants and 3 susceptibility genes. Shortly after the 

 researchers developed a transgenic mouse bearing the human mutation.

 But the problem was not due to a deficit or excess of 

 because altering levels of the normal enzyme in the mouse did not halt pathogenesis if the errant human gene was present.

 This situation indicates a "toxic gain-of-function"--the variant enzyme does something different.

Localizing the aberrant enzyme explains part of what may be happening; in mice and human postmortem tissues, the enzyme accumulates at the surfaces of mitochondria and in the intermembrane spaces, which may explain the structurally abnormal mitochondria in some patients.

 Mitochondria are the cell's headquarters for apoptosis. Here the abnormal enzyme interacts with the protein Bcl-2, which normally blocks apoptosis. With this control lifted, cells die.

The other major puzzle piece to ALS etiology is excitotoxic injury, which arises from impaired handling of glutamate in the spinal cord. Transporter proteins made in astrocytes escort glutamate across synapses, where it binds postsynaptic receptors. Calcium ions enter, triggering neuronal death. Normally, the transporters bind excess glutamate and take it into nearby astrocytes.

Evidence implicates impaired glutamate transporters and receptors in ALS. Rothstein and associates

 compared synaptosomes--vesicles that form at nerve endings when the tissue is homogenized--from spinal cord; sensory, motor, and visual cortex; striatum; and hippocampus from 13 persons with ALS, 12 with Huntington disease, 15 with Alzheimer disease, and 17 controls. The transporter effectively bound its cargo in all, but in the ALS patients, binding was slow in the spinal cord and in the motor and sensory cortexes.

A study from the University of Tokyo found that faulty RNA editing alters the glutamate recep- tor.

 Researchers compared how mRNA encodes a receptor subunit in ALS patients and in controls. In the ALS patients, a single incorrect amino acid is inserted into the protein about half the time.

The relationship between oxidative stress and excitotoxicity remains murky in regard to whether each causes a disease subtype or whether one precipitates the other. "At the present time, it is very difficult to decipher the toxic mechanism involved in ALS," said Patrick Aebischer, MD, PhD, president of the Swiss Federal Institute of Technology in Lausanne, Switzerland.

Another hypothesis regarding trauma as a risk factor for ALS resurfaced recently, when German and Italian researchers wrote about "the Italian motoneuron mystery."

 ALS was diagnosed in 33 of 24,000 top Italian soccer players between the 1960s and 1996.

ALS diagnosis is clinical; no laboratory tests are available (see box, Future ALS Diagnostics). The average neurologist will probably see only 3 or 4 ALS patients in a career; an internist may never see an ALS patient. Yet by the time of diagnosis, 50% of a patient's motor neurons may be affected.

In 1999, Aventis Pharma AG commissioned a study of the diagnostic trajectories of 201 patients in 6 countries. The average experience: a patient first consults a physician 4.6 months after symptom onset and first meets with a neurologist by 10.8 months, who diagnoses ALS within 6.9 months. That's more than 18 months from the first twitch or tumble. Nearly half of the patients were initially referred to non-neurologists, including rheumatologists, orthopedists, and chiropractors. Patients with bulbar onset and/or fasciculations tended to be referred to a neurologist faster.

Diagnosing ALS takes time. "When a patient first shows up, not even a specialist can make the diagnosis," said Rothstein, who, as head of a tertiary care center, sees more than 300 patients a year, of whom only 1 or 2 have received a misdiagnosis. "If the first symptoms are in the hands, a patient might come in thinking carpal tunnel syndrome; bulbar patients think it is a stroke," he added. After these and other possibilities have been ruled out, diagnosis requires watchful waiting. "Textbook criteria are evidence of diffuse upper and motor neuron degeneration on at least 2 levels. Signs of lower motor neuron involvement include weakness in the muscle, atrophy of the muscle, and fasciculations. Signs of upper motor neuron degeneration are brisk reflexes, hyperactive reflexes, spastic muscle tone, and some weakness," Rothstein said.

Harder to exclude is multifocal motor neuropathy, an autoimmune condition. "A patient may come in with a history of progressive, diffuse lower motor neuron signs and symptoms--weakness in one hand that has spread to the other, or footdrop--over 9 months. The patient has all the lower motor neuron signs, but no gross upper motor neuron signs," Rothstein said. He uses a blood test for anti-GM1 antibodies and an electromyogram to rule out the autoimmune condition. But continuing lack of upper motor neuron symptoms prompts some physicians to diagnose atypical ALS. In these cases, Rothstein said, upper motor neuron involvement usually is clear at autopsy.

 Animal models enable researchers to track amyotrophic lateral sclerosis (ALS) pathogenesis. Erik Storkebaum, MSc, and colleagues at the Center for Transgene Technology and Gene Therapy at Flanders Interuniversity, Leuven, Belgium, took several approaches to increase supply of the neuroprotective protein vascular endothelial growth factor (VEGF) in an animal model. "When administered to rats at 60 days, which is 1 month before symptoms, it delayed onset and prolonged survival by 22 days. When we gave VEGF at the age of disease onset, which more closely mimics the human situation, the treatment still prolonged life by an average of 10 days," Storkebaum reported at the Society for Neuroscience annual meeting in October 2004.

 Metabolon, Inc., of Durham, NC, is pursuing a route to earlier diagnosis that uses mass spectrometry to screen plasma for disease-specific, nonprotein biomarker "signatures." "In very preliminary work, we believe that we can see biomarkers that are different in sporadic versus familial ALS, and lower and upper motor neuron disease," said president and CEO John Ryals, PhD. Once signatures are confirmed, the approach will be used to track disease progression, he added.

 Cognitive decline may appear early in ALS, but is not yet well enough understood to aid diagnosis. "From 30% to 70% of patients may have a behavioral syndrome of disinhibition or emotional lability and difficulty with complex sequential task performance and speech. It is fairly subtle. If you look for it, you'll find it, but it doesn't leap out at you," said Michael Strong, MD, Arthur Hudson Chair in ALS Research at the University of Western Ontario, who chaired a workshop on cognitive changes in ALS in mid-May. Florid dementia is rare, he added. The subtler impairments arise from the frontotemporal lobe, apart from the motor strip.

ALS research shifts quickly from bench to bedside (see box, Future ALS Therapeutics). Finding the glutamate link quickly led to the development of the drug riluzole (Rilutek, Aventis). It increases survival by 3 to 6 months, more in younger patients, and is more effective in bulbar-onset cases.

 But it stands alone in the ALS drug arsenal. In January 2005, Novartis stopped developing TCH346, an anti-apoptotic agent, after phase 2 clinical trials did not show change in progression or survival. Agents that have been tried and rejected include celecoxib (Celebrex, Pfizer), indinavir (Crixivan, Merck), creatine, and neurotrophic factors; still in phase 3 clinical trials is minocycline (www.clinicaltrials.gov/ ct/show/NCT00047723?order=1).

Another promising antibiotic is ceftriaxone (Rocephin, Roche), identified in a screen of 1040 drugs for hiked transcription of the gene that encodes the glutamate transporter, which normally prevents glutamate excitotoxicity.

 The screen detected 20 compounds, 15 of which are b-lactamase antibiotics--but the mechanism is not related to antibacterial activity. Because ceftriaxone increased the supply of transporters in ALS mice and delayed progression, clinical trials are ongoing For more information, you can go to: www. clinicaltrials.gov/ct/show/show/NCT00001539?order=2 or go to www.clinicaltrials.gov/ct/show/NCT00111644?order=1).	

The ceftriaxone story reveals the importance of experimental design. A decade ago, trials of the drug in ALS had negative results,

 but those efforts, Rothstein said, were led by a single case report that was quickly retracted.

 The Italian ALS study group "conducted the trials expecting improvement, didn't use placebos in many cases, and tried the drugs for 1 to 8 weeks. In ALS, it takes 9 months to a year to see something," he added. 

Another old drug that is already helping some ALS patients is the cough remedy dextromethorphan/quinidine. Although a recent 

 article ridiculed its use as treatment for inappropriate laughing and crying,

 such emotional lability is a hallmark of ALS--and a debilitating one for patients who still work. "We've been using it off-label for years. The circuitry that controls the head-and-face musculature is tied to suppression of emotion. A patient with bulbar-onset ALS can very easily laugh and cry. The slightest hint of emotion bursts out," said Rothstein. Avanir Pharmaceuticals of San Diego is seeking FDA clearance to market the drug, which will be sold as Neurodex, for pseudobulbar affect. (See also A Cough Medicine and Neurologic Disorders, 

Yet another familiar compound being scrutinized for anti-ALS activity is tetrahydrocannabinol (THC). Abood and her team

 found that THC protects against oxidative stress and excitotoxicity in isolated spinal cord neurons. (See also Cannabinoids Showing Potential Value in Parkinson, Lou Gehrig Diseases, 

mouse, in several doses, and found that it delayed disease progression and prolonged life span by about 5%, which extrapolates to about 4Z\x extra months in humans," she said. Some physicians prescribe Marinol (Unimed) off-label for appetite stimulation in ALS patients, and Health Canada recently approved Sativex (GW Pharmaceuticals), a cannabis extract, to treat multiple sclerosis. This drug may also be useful in ALS. (See Canada Approves Cannabis, 

Perhaps the biggest hurdle for an ALS patient is the decision to use or refuse a ventilator when breathing begins to fail. Many neurologists concur that the overwhelming majority of patients refuse this measure. Rothstein explains why: the disease doesn't stop. "You eventually lose all movements. You may get little twitches in your fingers that you can use to communicate with computers. When that goes, you can use eye movements to track infrared devices to communicate. But eventually eye movements cease, and then you are locked in. People must give up their lives to take care of you for a very unusual quality of life. As physicians, we support it if it's what a patient wants, but it is important for patients to understand what it means to be on a ventilator." This dire situation may change if clinical trials after a pilot study on a diaphragm pacing system that stimulates the phrenic nerve are positive. (See DPS and Electrostimulation Allow Patients With ALS to Breathe, 

The rarity and lack of treatment for ALS may paint a bleak picture, but the alacrity with which basic science is transitioning to clinical trials offers hope. Don Cleveland, PhD, a professor of medicine, neuroscience, and cellular and molecular medicine at the University of California, San Diego, described the current climate as one of "stubborn optimism." "The issue isn't that we can't identify strategies that can be effective, but whether we can deliver them in an optimal way. The failures are of delivery, not the concept," he said at an ALS symposium at the Society for Neuroscience 2004 annual meeting.	*

 At Chaoyang Hospital in Beijing, Hongyun Huang, MD, has treated more than 100 patients who have amyotrophic lateral sclerosis (ALS) with injections of human fetal olfactory ensheathing glial cells into 2 sites in the subcortical white matter below the motor cortex and, in some patients, at the top of the spinal cord. The waiting list for Americans with ALS is 600 strong. "People are reporting dramatic improvement--but we've been there before, with fetal transplants and Parkinson disease (PD). The placebo effect in brain surgery is enormous," said Nicholas Boulis, MD, a neurosurgeon at the Cleveland Clinic. He was referring to the phenomenon whereby participants in clinical trials for PD treatments who undergo sham surgery sometimes report improvement. But Huang does not think this is the case for ALS. "I don't think the effect that makes the patients improve is a placebo effect. This terrible disease is quite different from PD, which is often influenced by mental state." He hopes that the treatment will patch damage and halt progression.

 Insulinlike growth factor (IGF) (myotrophin) is in phase 3 clinical trials to slow progression of weakness in ALS. Earlier trials were negative in Europe but positive in the United States. When the sponsoring company opted out of a third try, an academic consortium took over. The clinical trial uses this recombinant protein. Preclinical models are testing gene therapies, including the piggybacking of IGF-1 to clostridial toxins to target motor neurons and the use of an adeno-associated virus as a vector that uses its retrograde axonal transport from muscle to neuron.	

Patrick Aebischer, MD, PhD, president of the Swiss Federal Institute of Technology in Lausanne, Switzerland, and his team are dampening expression of the 

 gene while providing the normal protein. The result in mice is delayed onset of ALS and 3 additional weeks of life. The technique uses small, interfering RNAs (siRNAs). "These are small pieces of RNA that bind mRNA and are degraded by enzymes, so the protein is not produced," he said. Aebischer has videos that show ALS mice being unable to hoist themselves out of a pool before treatment and showing restoration of some swimming ability after treatment. "[ALS symptoms in] the treated mice were significantly ameliorated, their [electromyographic findings] improved, and treatment conserved many more myelinated axons," he said.

 Ian Wilmut, PhD, a professor at the Roslin Institute in Edinburgh, and Christopher Shaw, MD, of the Institute of Psychiatry in London, received a license in February 2005 to use early human embryos to explore the etiology of various diseases. The first disease they are looking into is ALS. They will introduce the 

mutation and derive embryonic stem cells, which will then be stimulated to differentiate as neural tissue.

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Animal models enable researchers to track amyotrophic lateral sclerosis (ALS) pathogenesis. Erik Storkebaum, MSc, and colleagues at the Center for Transgene Technology and Gene Therapy at Flanders Interuniversity, Leuven, Belgium, took several approaches to increase supply of the neuroprotective protein vascular endothelial growth factor (VEGF) in an animal model. "When administered to rats at 60 days, which is 1 month before symptoms, it delayed onset and prolonged survival by 22 days. When we gave VEGF at the age of disease onset, which more closely mimics the human situation, the treatment still prolonged life by an average of 10 days," Storkebaum reported at the Society for Neuroscience annual meeting in October 2004