Mild traumatic brain injury : clinical course and prognostic factors for postconcussional disorder

Abstract

Background: Mild traumatic brain injury (MTBI) is frequent and sometimes leads to persistent disability. It remains a matter of controversy as to what impact the different main determinants - brain injury factors and psychosocial factors - exert on the development of postconcussional disorder (PCD).

Aims, subjects and methods: The overall aim was to find predictors for PCD after MTBI. One hundred and twenty-two persons with MTBI were assessed with CT and MRI brain scans, S 100B, S 100A1B, and clinical variables. The first week after the trauma an extended assessment was performed, including previous history of psychiatric disorder, psychological function the year before the trauma, personality, coping ability, and concurrent psychosocial streamers. Three months post injury outcome was assessed by use of self assessment questionnaires for MTBI symptoms and disability. Cognitive impairment was assessed with a computerized Automated Psychology Test (APT) and neuropsychological testing. Thirtyfive healthy control persons were assessed for comparison.

Results: Is increased S 100 associated with cognitive impairment? S 100B and S 100A1B were increased in 42 % and 64 % of the patients. Cognitive impairment was found in 8 % when assessed with APT and in 30 % when assessed with neuropsychological tests. No significant correlation was found between S 100B or S 100A1B and cognitive impairment, nor between subjectively reported cognitive dysfunction and test performance, regardless of the method used.

What is the clinical course after MTBI? At least one persisting symptom was reported by 49 % of the patients at three months - most commonly poor memory, sleeping problems and fatigue. High symptom load at day one correlated with high symptom load and disability at three months, when 25 % also reported disability in at least one domain of everyday life.

How should PCD be defined? The ICD-10 definition of PCD was considered too liberal as no disability was required. Sixteen % of control subjects were considered "cognitive impairment cases" as compared to 28 % in the MTBI group. The results from neuropsychological testing had insufficient specificity to qualify, as proposed in the DSM-IV, as a defining property of PCD. A definition of PCD based on a minimum of three symptoms and two domains of disability at three months post injury was proposed, which yielded 17 % PCD cases in the whole sample.

Which risk factors predict the development of PCD? Preinjury psychological vulnerability (previous psychiatric disorder, trait anxiety, embitterment), lower preinjury psychological function (GAF) and concurrent psychosocial stressors were significant predictors of PCD. Posttraumatic stress (hyperarousal) one week after the MTBI had the highest impact on the outcome. Female gender and concurrent medical condition were also correlated to PCD, but no correlation was found between PCD and injury related factor.

Summary: Signs of brain injury or brain dysfunction are present in the early phase after MTBI but show poor correlation to PCD as defined by at least three symptoms in combination with disability at three months post injury. The results from neuropsychological testing had insufficient specificity to qualify as a defining property of PCD. Prognosis after MTBI is good in most cases, but a minority of patients develop PCD, which emerges as a result of the interaction between premorbid psychological vulnerability, brain dysfunction in the early phase, posttraumatic hyperarousal and concurrent psychosocial stressors.