The Terri Schiavo story that was widely publicized in early 2005 was one in which clinical issues were at best misunderstood and at worst overshadowed by political posturing and media sensationalism. The subtle distinctions between vegetative state, minimally conscious state (MCS), and locked-in syndrome-difficult to differentiate even for physicians-were too often misused or glossed over. Commentators were more interested in such ethically loaded questions as whether remarks once made by Schiavo while watching television constituted an expressed wish that her life not be prolonged artificially, or whether Schiavo's husband Michael, as her guardian, could be acting in her best interests while living with another woman.
Schiavo's 15 years of impaired consciousness, diagnosed by most consulting neurologists as a vegetative state, ended on March 31, 2005, 2 weeks after her percutaneous endoscopic gastrostomy tube was removed. More than a year later, her story is still a topic of public discussion. Schiavo's husband and her parents each published a book on the anniversary of her death, while US politicians and activists on both sides of the "feeding tube" debate continue to battle over more than 40 proposed pieces of legislation that would restrict the withdrawal of artificially administered nutrition and hydration.
But the past year also has seen an intensification of interest in issues of impaired consciousness on the part of researchers and clinicians. Dozens of papers on the diagnosis and management of vegetative state and minimally conscious state have appeared in the medical literature during that time, including a 555-page special issue of the international journal Neuropsychological Rehabilitation published in the fall of 2005.1 Furthermore, the American Academy of Neurology held a breakfast seminar on vegetative state at its annual meeting in April.
Although functional imaging techniques are helping researchers differentiate vegetative state from MCS by teasing out evidence of cognitive processes in outwardly unresponsive patients, making this critical distinction remains a profound diagnostic challenge for clinicians who lack access to such technology.
"We can't get inside somebody's mind. All we can do is try to stimulate them and gauge their reactions," said James L. Bernat, MD, professor of neurology at Dartmouth Medical School in Hanover, New Hampshire.
MULTIPLE MISDIAGNOSES
Indeed, the ability to measure a patient's responsiveness is the key to the differential diagnosis of vegetative state, MCS, or locked-in syndrome, and the inability to recognize very low levels of awareness is what accounts for the number of minimally conscious or locked-in patients who receive a misdiagnosis of vegetative state. A 1993 study by Nancy L. Childs, MD, and colleagues at the Healthcare Rehabilitation Center in Austin, Texas, found that a misdiagnosis of coma or persistent vegetative state was made in 37% of 49 patients.2 In 1996, Keith Andrews, MD, and colleagues at the Royal Hospital for Neuro-disability in London reported misdiagnosis of vegetative state in 43% of 40 patients-including one man thought to have been in a vegetative state for 7 years who, 2 weeks after admission to Andrews' rehabilitation unit, was able to "dictate" letters to his wife with the aid of a computer.3
No more recent data on misdiagnoses of vegetative state are available in the medical literature, and it is possible that the numbers have come down since the 2002 publication of a definition and diagnostic criteria for MCS by a collaborative group of authors led by Joseph T. Giacino, PhD, associate director of neuropsychology at the New Jersey Neuroscience Institute of the JFK Johnson Rehabilitation Institute in Edison.4 But the consensus among experts is that misdiagnosis rates are still unacceptably high.
"Anecdotally, I think most clinicians who focus in this area would still acknowledge that there are a lot of misdiagnoses being applied,"Giacino said. "Many of us see patients who get admitted to our centers with a diagnosis of vegetative state, and on the first examination, it becomes apparent that they do actually have some awareness."
Published criteria for diagnosing vegetative state (also historically referred to as "persistent vegetative state" or "permanent vegetative state"-terms that Bernat and other experts feel are misleading) and MCS are listed in Tables 1 and 2. The key difference between them is that a patient in a vegetative state demonstrates no evidence of conscious behavior at any time, whereas a patient in an MCS demonstrates clear evidence of conscious behavior at least some of the time. Locked-in syndrome, which is not a disorder of consciousness, can be difficult to distinguish from vegetative state because of the locked-in patient's inability to communicate his or her awareness other than by eye blinking. However, locked-in syndrome is typically characterized by quadriplegia or more extensive paralysis, whereas patients in a vegetative state are not paralyzed and often make reflexive movements, although not purposeful ones.5
Table 1 — Criteria for diagnosis of vegetative state19 |
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| No evidence of awareness of self or environment | ||
| Incapable of interacting with others | ||
| No sustained, reproducible, or purposeful voluntary behavioral responses to visual, auditory, tactile, or noxious stimuli | ||
| No evidence of language comprehension or expression | ||
| Intermittent wakefulness characterized by sleep-wake cycles | ||
| Preserved autonomic and hypothalamic function sufficient for survival with medical or nursing care | ||
| Bowel and bladder incontinence | ||
| Preserved cranial nerve reflexes | ||
Table 2 — Criteria for diagnosis of minimally conscious state4 |
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| Limited but clearly discernable evidence of self-awareness or environmental awareness, as demonstrated in a sustained or reproducible manner by 1 or more of the following behaviors: | ||
| Follows simple commands | ||
| Gestures or verbalizes yes/no responses (regardless of accuracy) | ||
| Verbalizes intelligibly | ||
| Purposeful behavior that occurs in response to relevant environmental stimuli and is not merely reflexive. Examples include: | ||
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