Sound Bites

June 17, 2006

mental notes

News from the Annual Meeting of the American Academy of NeurologyNeurologic Gait Predicts Vascular Dementia By: Jordana Bieze Foster The presence of a neurologic gait abnormality, particularly in combination with executive dysfunction, may be predictive of vascular dementia onset within 5 years, according to researchers from Albert Einstein College of Medicine in the Bronx, New York. Revisiting the 422-subject population from the Bronx Aging study (Verghese J, Lipton RB, Hall CB, et al. Abnormality of gait as a predictor of non-Alzheimer's dementia. N Engl J Med. 2002;347:1761-1768), the investigators grouped the 3 types of neurologic gait that were associated with vascular dementia in the earlier study: hemiparetic, frontal, and unsteady. They also looked at the first 5 years of follow-up (the earlier study had a median duration of 6.6 years follow-up)."The important thing is that we want to be able to tell patients about the risk of vascular dementia in the next few years. They don't necessarily want to know about their 20-year risk," said Joe Verghese, MD, associate professor of neurology at Albert Einstein and lead author of both studies. At baseline, high-risk neurologic gait was diagnosed in 54 of 422 patients. During the 5-year follow-up, vascular dementia developed in 25 of the 422 patients. The hazard ratio associated with developing vascular dementia based on baseline high-risk neurologic gait alone was 2.66, but the predictive power of the gait variable increased significantly when combined with executive dysfunction measured using the Digit Symbol Substitution test. The hazard ratio for vascular dementia was 5.94 in patients with either high-risk neurologic gait or executive dysfunction and 12.48 in patients with both risk factors."Executive dysfunction provides incremental validity to high-risk neurologic gait in identifying high-risk subjects," Verghese said. "If gait is normal and there's no executive dysfunction, you can be reasonably certain there's no vascular dementia."History of stroke or transient ischemic attack was not predictive of vascular dementia, probably because of the silent nature of many strokes, Verghese said. However, hemiparetic gait, which had the highest hazard ratio of the 3 high-risk gait types in the earlier study, is frequently associated with stroke. In addition, frontal gait has been associated with cerebrovascular disease. Although unsteady gait may have many causes, Verghese and colleagues believe their findings suggest this gait type may be a marker for low levels of cerebrovascular disease that can progress if left unchecked.- Verghese J, Derby C, Lipton R. High risk neurological gaits and vascular dementia. Neurology. 2006;66(suppl 2):A57-A58.

News from the Annual Meeting of the American Academy of NeurologyEssential Tremor: A Too-Common Misdiagnosis By: Jordana Bieze Foster Essential tremor (ET) is misdiagnosed in 1 of every 3 cases. The findings confirm an earlier report of overdiagnosis of ET and identify specific factors that are characteristic of misdiagnoses.A team led by Elan D. Louis, MD, associate professor of neurology at Columbia University in New York City, retrospectively reviewed and reevaluated 71 cases of ET. The ET diagnosis in 26 (36.6%) of those cases was deemed to be false. ET was most often confused with Parkinson disease (PD) (11 cases), followed by dystonia (6 cases), PD with ET (5 cases), and other tremor disorders.The finding was consistent with a British study (Schrag A, Munchau A, Bhatia KP, et al. Essential tremor: an overdiagnosed condition? J Neurol. 2000;247:955-959), in which 50% of ET cases diagnosed by a neurologist were consistent with a previously defined phenotype. In the study, 10 of 25 patients in whom ET was misdiagnosed had symptoms that the authors described as clearly characteristic of other diagnoses, including additional dystonia, neuropathic tremor, unilateral leg tremor, drug-induced tremor, and sudden onset after head trauma.Patient characteristics that were more often associated with an ET misdiagnosis included self-reported unilateral tremor onset (seen in 48.8% of false cases versus 37.5% of true cases), unilateral arm tremor on examination (19.2% versus 2.2%), spooning of hands or other subtle dystonic postures (53.9% versus 6.7%), slight reduction in arm swing (53.9% versus 13.3%), and unusual features such as isolated thumb or leg tremor (34.6% versus 0%).The results reflect a lack of consensus within the neurology community about inclusion and-perhaps more important-exclusion criteria for the diagnosis of ET. Louis and his team recommend the development of an improved diagnostic algorithm.- Jain S, Lo S, Louis E. Essential tremor may be the most commonly misdiagnosed movement disorder: identification of factors associated with diagnostic errors. Neurology. 2006;66(suppl 2):A114.

News from the Annual Meeting of the American Academy of Neurology"Nice-Guy Syndrome" in ALS Tied to Amygdalar Involvement By: Jordana Bieze Foster Patients with amyotropic lateral sclerosis (ALS) tend to respond positively to facial expressions that healthy persons consider threatening or distrustful. The phenomenon suggests amygdalar involvement in ALS, according to researchers from Baylor College of Medicine in Houston.To confirm their suspicion of amygdalar involvement in what has been called the "nice-guy syndrome" in ALS, investigators showed photographs of 51 faces to 26 patients with ALS and 26 healthy persons (controls) to evaluate facial recognition responses. The researchers asked each person whether he or she would ask the photographed person for directions to a hotel if lost in a strange town at dusk.Controls rated 14 of the 51 faces as "not approachable" (a negative value on a scale from 23 to +3), whereas the patients with ALS rated only 3 of 51 faces as not approachable. The researchers noted that the average rating for the top 10 most approachable faces was similar for the 2 groups (2.0 in patients versus 2.1 in controls), while the average rating for the 10 least approachable faces was significantly different (+0.25 for patients versus 20.92 for controls). "Trusters," or study participants whose 10 lowest ratings averaged a positive value, accounted for 14 of the 26 patients with ALS but only 6 of the 26 controls.Because amygdalar dysfunction has been associated with the inability to recognize threat in facial expressions, the research team, represented at the American Academy of Neurology (AAN) meeting by Heike I. Schmolck, MD, PhD, a fellow in the Department of Neurology at Baylor, theorized that amygdala functioning is impaired in ALS. "This is the possible biological basis for the 'ALS personality,'" the researchers concluded.- Schmolck HI, Mosnik D, Schulz PE. Is the amygdala affected in amyotrophic lateral sclerosis. Neurology. 2006;66(suppl 2):A260.