Why do some patients after head injury deteriorate over the long term?
- Correspondence to Dr Simon Fleminger, Institute of Psychiatry, Kings College London, London SE5 8AZ, UK;
- Received 7 May 2012
- Accepted 11 May 2012
- Published Online First 6 August 2012
- head injury
- cognitive neuropsychology
- subarachnoid haemorrhage
When asked to see a patient who is deteriorating rather than getting better over time since a head injury, the clinician will need to rule out complications of the head injury, such as a subdural haematoma. The neuropsychiatrist will assess whether, for example, a depressive illness, anxiety disorder, psychosis or substance abuse explains the deterioration. But oftentimes there is no obvious explanation for the deterioration. This finding tallies with studies that find increasing cognitive impairment over time since injury in a proportion of patients.1 Explanations for this include accelerated cerebral atrophy2 and/or chronic inflammation3 or depleted cerebral reserve bringing forward age-related cognitive decline.4
Two papers with very different methodologies, one strong and one rather weaker, address the question of the long-term outcome after a head injury. Wang et al,5 interrogated a clinical database containing the medical insurance records of one million people, to see if head injury was a cause of dementia. Patients who were older than 30 years and with a head injury diagnosis entered the study. Their records were followed-up for 5 years to see if they acquired a diagnosis of dementia over this period. Compared with matched controls, these head injured probands had about a twofold increased risk of developing dementia. The effect was slightly smaller after controlling for the observation that the probands had, at the time of head injury, higher rates of cardiovascular disease including strokes.
However, the fact that those with head injury had higher rates of cardiovascular disease indicates that head injuries were not merely random events, but that something about the person put them at increased risk of suffering a head injury. Perhaps prodromal symptoms of a dementia also increased the risk of head injury, and this in part explains the higher rate of dementia post injury; an examination of the year of greatest risk in the 5-year follow-up, would have been of interest. Nor have the authors examined the interaction between the two to threefold increased risk of stroke they found in many of these head injured cases5 (the cohort of Chen et al 6 overlaps heavily with the present paper but is not identical) on the likelihood of being diagnosed as suffering dementia over the same 5-year follow-up period. Finally one wonders, when the clinicians entered the data into the insurance record endorsing the diagnosis of dementia, and in the vast majority of cases in both probands and controls this was ‘unspecified’ dementia, did they always mean that the patient had deteriorated since the injury? Or were they sometimes, in those who had suffered a head injury, merely referring to a global impairment of cognitive function, acquired at the time of the head injury but unchanged since then. In summary, I thought this paper provided qualified endorsement of the proposal that head injury increases the risk of developing a dementia.
In the second paper by McMillan et al,7 there is no doubt about what is being measured. This is the latest of a series of papers where the Glasgow Outcome Scale—Extended has been used to follow-up a cohort of patients who suffered a head injury in Glasgow in the mid 1990s, to observe changes in disability over time. For those of us interested in neuropsychiatric effects on outcome after head injury, this has been a fascinating series of papers to follow. The follow-up at 5–7 years8 found that depression and alcohol use predicted who had done badly, that is, got worse over time since the injury. Now, looking at a 12–14-years follow-up, again a significant minority, over a quarter, of patients had got worse (compared with how they had been at 5–7 years). The best predictor at 5–7 years post injury of who was going to deteriorate was the patient's view of themselves. Those who felt relatively powerless, as measured by their perceived locus of control being ‘powerful others’, were more likely to show an increase in their disability when assessed 7 years later. This study suggests that the effect of self perception on outcome is seen years after injury, and in the first few months,9 a finding that has important treatment implications.
Competing interests None.
Provenance and peer review Commissioned; externally peer reviewed.