Mild traumatic brain injury : antecedents and aftermath

Abstract

Mild Traumatic Brain Injury (mTBI) is a frequent, trauma-induced injury, associated with loss of consciousness and/or memory loss for the injury event. Injured individuals experience a wide range of somatic symptoms (e.g. headache, nausea), cognitive symptoms (e.g. poor concentration, memory problems) and affective symptoms (e.g. irritability, depressed mood). These symptoms gradually resolve within days or weeks for the majority of the affected individuals. A minority will however report persisting post-concussion symptoms (PCS). The etiology of these complaints is in dispute, both psychological and organic factors have been proposed. Brain Reserve Capacity theory hypothesize that variations in outcome after seemingly similar brain injuries can be explained by brain “reserves” that acts as buffers. Papers presented herein explores this hypothesis with particular emphasis on cognitive and emotional reserve.

Data comes from two studies. Study 1 have a case-control study design with 24 included mTBI patients referred for neuropsychological assessment (paper 1 and 4). Study 2 is a cohort study with 122 mTBI patients followed prospectively from emergency department visit to follow-up at 3 months (paper 2) and 12 months post injury (paper 3). In Paper 1 we examined if mTBI patients with persisting PCS exhibits deficits in emotional awareness, decision making or have higher levels of disadvantageous personality traits compared with non-injured controls. No significant differences in performance were noted with regard to emotional awareness or decision making. Patients had significantly higher levels of trait anxiety and stress susceptibility. In Paper 2 we examined if cognitive performance, particularly attention and memory, in prospectively followed patients with persistent PCS would be more impaired than in those patients who had recovered. We also examined if cognitive reserve, indicated by education level, skill level at work and estimated premorbid intelligence would influence recovery. Three months post injury, mTBI patients regardless of PCS status performed more poorly in a highly challenging memory test compared to non-injured controls and norms. Patients with lower cognitive reserve were 4 times more likely to suffer from persistent PCS.

In Paper 3 we examined if emotional reserve, indicated by previous psychiatric history, personality traits and psychological resilience would influence recovery after mTBI. Oneyear post-injury, 12 % of the prospectively followed patients had persisting PCS and reported disability in daily life. These patients had reported more psychiatric problems and experienced more stress before and at the time of the injury. They also had lower levels of resilience and exhibited higher levels of personality traits related to somatic trait anxiety, embitterment and mistrust compared to recovered patients. In Paper 4 we examined pain reporting in a sample of mTBI patients referred for neuropsychological assessment in the post-acute stage and its possible influence on cognitive performance. Patients reported significantly more musculoskeletal pain in the neck and shoulders than non-injured control. In cognitive tests, patients performed on average worse than the controls, but no additive effect of pain was noted. Pain was however associated with more impaired performance in timed tasks, primarily measuring processing speed, in noninjured controls.

Conclusions: Cognitive deficits in the form of subtle executive problems are still evident in mild traumatic brain injury patients three months post-injury. A pre-injury lower level of cognitive and / or emotional reserve is a considerable risk factor for development of persistent post-concussion symptoms after mild traumatic brain injury. High level of pain, including musculoskeletal pain is common in patients with persisting post-concussion symptoms.