Caring for patients in a persistent vegetative state is one of the most demanding duties faced by families and health care professionals. An estimated 10,000 to 25,000 adult patients are in a persistent vegetative state in the United States; medical care for these patients may cost up to $7 billion annually. Predicting which patients with severe brain damage will progress to a persistent vegetative state is extremely important, as crucial decisions about life support, resuscitation, tube feeding and other issues have to be faced. Unfortunately, vegetative states may be misdiagnosed in up to 43 percent of patients, and one half of patients in post-traumatic vegetative states may recover within one year. Neurodiagnostic tests such as evoked potentials, electroencephalograms and computed tomographic (CT) scanning have failed to predict the probability of recovery. Kampfl and colleagues studied the ability of magnetic resonance imaging (MRI) to predict recovery from a post-traumatic vegetative state.
The study included 80 patients who were admitted to a trauma and rehabilitation center as a result of closed head injury between 1988 and 1996. The patients were in a subacute vegetative state that continued for at least six to eight weeks following the injury. Full clinical assessment with MRI was performed six to eight weeks after the injury. Clinical assessment, including documentation of the patient's score on the Glasgow Coma Scale, was repeated at two, three, six, nine and 12 months following the injury. International diagnostic criteria were used to define vegetative state; persistent vegetative state was defined as a vegetative state that had endured for at least 12 months following injury. MRIs were interpreted by three independent neuroradiologists who were unaware of the clinical findings or medical histories of the patients.
The most common cause of head injury was motor vehicle accident. Patients who remained in a persistent vegetative state did not differ from those who recovered in terms of age, sex or initial score on the Glasgow Coma Scale. The two groups were also comparable in terms of medical complications or surgical intervention for evacuation of subdural or epidural hematoma. Of the 38 patients who recovered, 24 patients showed signs of recovery within three months, and 36 patients showed signs of recovery within six months of the injury. One half of those who recovered from vegetative states had a moderate disability. In general, better outcomes were associated with earlier signs of recovery.
Patients who developed a persistent vegetative state had a significantly higher frequency of MRI-detected lesions in the corpus callosum and corona radiata. Corpus callosum injury was documented in 98 percent of patients who developed a persistent vegetative state, compared with only 24 percent of those who recovered. Differences in injury to the corona radiata were less dramatic (57 percent in patients with persistent vegetative state, compared with 26 percent of those who recovered) but were still statistically significant. Patients in a persistent vegetative state also had significantly more injuries to the dorsolateral upper brain stem than patients who recovered.
The authors conclude that obtaining cerebral MRI on patients with closed head injury within eight weeks of the injury can predict outcome. They developed a model that correctly predicted outcome at one year in over 87 percent of cases. The most significant lesions determining outcome appeared to be those of the corpus callosum, followed by lesions on the dorsolateral brainstem. This finding is in contrast to studies that have documented the inability of various neurodiagnostic tests and CT scanning to predict outcome in these cases.
editor's note: Assisting a family that is trying to cope with the aftermath of severe trauma is a demanding part of family practice. Although each case is unique, studies like this help to stabilize an overwhelming situation and provide some reasonably scientific data on which families can base decisions. Hope must never be lost, but pragmatic actions have to be taken concerning such issues as long-term placement, the use of ventilation, gastrostomy feeding and level of intervention in treating medical complications. Families may receive conflicting advice and prognoses from multiple specialists, and the primary care physician can be a powerful advocate and counselor. Family physicians need to be able to provide reliable probabilities and “quantitative” information, as well as counseling and support, in the care of these patients and their families.—a.d.w.