The ataxic subgroup: A discrete outcome after traumatic brain injury

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Abstract
We have observed five individuals who appear to represent a unique subgroup of patients with traumatic brain injury (TBI). Because of the prominence of severe ataxia, this group has been labelled the ‘ataxic subgroup’. These individuals are distinguished by both clinical course and outcome, including severe ataxia, prolonged coma and prolonged post-traumatic amnesia (PTA). They distinguish themselves from other severely impaired TBI patients in that they spend a relatively longer length of time prior to the establishment of volition, but progress rapidly through the period of confusion. We hypothesized that this group is unique in that they have suffered Grade III diffuse axonal injury (DAI) with no or minimal complications due to other primary or secondary brain damage. In order to investigate these hypotheses, a retrospective file review of a selected group of 72 patients was undertaken to determine the specificity and sensitivity of two diagnostic criteria. The existence of severe Grade III DAI without other primary or secondary brain damage was presumed if severe ataxia was present in conjunction with normal CT scans. Results of this review indicated that 33% of the population demonstrated severe ataxia, although only 11% also had normal CT scans. These dual criteria were neither adequately sensitive nor specific to define the five patients who comprised the `ataxic subgroup'. When rate of clearing the confused period of PTA was added to the diagnostic criteria, specificity improved. Although this attempt to define this subgroup empirically was not entirely successful, further attempts to delineate this group are important in that prognosis for clearing PTA is good despite early indicators of poor outcome. Furthermore, this group may provide clues regarding the presentation of one type of neuropathology unique to TBI.