Identification of transient altered consciousness induced by military-related blast exposure and its relation to postconcussion symptoms

BACKGROUND: The ongoing controversy whether mild traumatic brain injury (TBI) can cause chronic sequel is partly due to diagnostic limitations. Diagnosing mild TBI is particularly challenging when assessment is not immediate, and when informed, first responder documentation or witness corroboration is absent. In this common scenario, the diagnosis is made entirely on self-report of an initial period of alteration of consciousness (AOC) associated with a plausible injury mechanism. Yet, there is scant published empirical guidance on methods for accurately detecting historical AOC. OBJECTIVES: To assess the value that recalled AOC symptoms collected via questionnaire have in evaluating individuals exposed to blast during recent military deployment. More specifically, to analyze the concrete AOC items (those signifying unconsciousness and/or posttraumatic amnesia) for their (1) frequency and distribution of positive versus negative responses, (2) interitem agreement, and (3) relation to current neuropsychiatric symptoms including those consistent with postconcussion syndrome (PCS). PARTICIPANTS: Eighty-seven active duty or Veteran subjects who experienced acute effects from a blast within the past 2 years while deployed for Operations Enduring and Iraqi Freedom. RESULTS: Twenty-nine participants (33.3%) responded positively to at least 1 of 3 concrete AOC items: gap in memory (17.2%), memory not continuous (13.8%), and/or told by observer they had loss of consciousness (20.7%). Alteration of consciousness items were associated with but nondiscriminate of current symptom distress on standardized measures of PCS (Rivermead Postconcussion Symptom Questionnaire), posttraumatic stress disorder (PTSD; PTSD Checklist), depression (Centers for Epidemiological Studies Depression Scale), and pain (Short Form McGill Pain Questionnaire). CONCLUSIONS: The positive association between subjects' questionnaire-based AOC item responses and current symptom complex measures suggests that mild TBI has a role in the development of chronic neuropsychiatric symptoms after blast exposure. The lack of symptom- complex discrimination, and the inconsistencies found in subjects' item responses suggest that a structured interview may improve postacute diagnostic specificity for mild TBI.