Severe Head Injury With Amnesia May Boost Later Risk of Multiple System Atrophy

BY JOHN R. BELL
Elsevier Global Medical News

BOSTON (EGMN) - Severe head injury with amnesia is associated with a fourfold increased risk of multiple system atrophy later in life, according to preliminary analysis of a multicenter, case-control study presented May 1 at the annual meeting of the American Academy of Neurology.

Caroline Tanner, Ph.D., director of clinical research at the Parkinson's Institute in Sunnyvale, Calif., and colleagues, obtained via questionnaire, detailed lifetime histories of head injury for 141 subjects deemed by movement-disorder specialists as being likely to have multiple system atrophy (MSA) and for 140 healthy control subjects who were nonblood relatives of the MSA patients.

Head injury was defined as being associated with loss of consciousness, concussion, or amnesia. The investigators excluded those with head injury occurring after the onset of MSA.

For the likelihood of ever having had head injury with amnesia, the investigators reported a crude odds ratio of 4.4, which did not change after they controlled for gender. Of the MSA group, 12 (9%) reported sustaining such an injury, compared with 3 (2%) of the control participants (odds ratio 4.8).

Dr. Tanner and colleagues reported that although both groups had similar rates of significant head injury (39 of 140 of the MSA subjects vs. 41 of 141 of the control subjects), as well as concussion or loss of consciousness, there was more amnesia reported among the participants with MSA. For MSA participants, the median time from the first head injury with amnesia to the onset of disease was 32 years.

When only amnesia that occurred 10 years before the reference year was included, the increased risk of MSA remained.

Demographic profiles of both groups were similar. At recruitment, men accounted for 60% of the MSA group and 42% of the control group. The mean ages were 63 years and 66 years, respectively. Of the MSA subjects, 90% were non-Hispanic whites, versus 83% of the control subjects.

Prior research has established a correlation between severity of neuronal injury and posttraumatic amnesia, as well as Parkinson's disease, noted Dr. Tanner who presented the study in a poster session at the meeting. If this connection is replicated by larger studies, it could help predict who is likely to develop MSA and enable a preventive intervention.

"There's a little bit of plausibility to ... [the injury/MSA hypothesis] from the pathogenesis idea, because we think it sets off sort of the cascade of inflammatory injury and that that may be important to [Parkinson's disease] and MSA pathogenesis. An alternative theory is that it could disrupt the blood-brain barrier," she said. If it does, then someone who suffers a head injury with amnesia might be more vulnerable to toxins entering the brain.

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