Cognitive and funtional outcome following traumatic brain injury or subarachnoid haemorrhage

Long term cognitive impairments are recognised as common consequences of both traumatic brain injury (TBI) and aneurysmal subarachnoid haemorrhage (SAH). Primary injury to the brain resulting from impact and secondary insults arising by various mechanisms contribute to disturbed psychological function in both conditions. The evolution of these cognitive impairments and their association with everyday functional consequences is poorly understood. The present study was designed to investigate the outcome of 100 surviving patients who were admitted consecutively to a regional neurosurgical unit with a diagnosis of either moderate or severe TBI. An additional group of 44 SAH patients was recruited to enable tentative comparisons to be drawn between groups with acute brain injury arising from these different causes. At intervals of 6, 12 and 24 months post-injury, global outcome was estimated using the Glasgow Outcome Scale (GOS) and patients were assessed using a battery of neuropsychological tests. Information concerning the extent of the patient's recovery was also collected at each time point. Poorer GOS outcome was associated with greater severity of initial injury. However, complications arising at the acute stage of treatment also influenced outcome. Because of the limited sensitivity of the GOS, a more detailed outcome scale, the Edinburgh Extended Glasgow Outcome Scale (EEGOS), was devised and applied. Results of the neuropsychological assessment in the TBI patient groups showed that severe cognitive impairment was typically associated with more severe initial injury. These results are in agreement with those of Rimel et al. (1982) in suggesting that patients with moderate TBI experience a level ofmorbidity intermediate between those with severe and those with minor TBI, and contrast with those ofAnderson et al. (1994) for reasons which are discussed. Despite the relationship between severity of injury and cognitive impairment, functional problems were reported to a similar extent by relatives of both the severe and moderate TBI patients. The results suggest that the brain injury impacts on everyday life to a greater extent and in many more patients than might be expected on the basis of formal cognitive assessment. Comparisons between the TBI and SAH groups were heavily influenced by a difference in the estimated severity of initial brain injury, but there were similarities in outcome between groups. A broadly similar pattern of cognitive impairment, although of less severity, was found in the SAH patients, but again functional problems reported by relatives suggested that the injury had more serious effects on everyday life than might be expected from formal assessment. The results suggest that formal assessment of cognitive function is useful and informative in the conditions studied, but that other measures provide important supplementary information about the ways in which acute brain injury influences the lives of patients. Chapter One Acute Brain Injury It has been remarked that an accident which causes injury to the trunk of the body will result in either death or good recovery. However, an accident or condition which causes damage to the brain or nervous system will often result in long term impairment and consequent disability (Jennett, 1996). Such an injury does not lead to a shortened life-expectancy and so the implications for family and carers are significant. For this reason, it is very important to follow up patients who sustain brain injuries to try and assess the degree of residual long term impairment and disability. London (1967) commented that as medical treatment improved, and the proportion of patients who survived severe head injury increased, so the number of severely disabled patients (or 'lamebrains') rose. Over the past thirty years, the survival rate of patients with traumatic brain injury (TBI) has continued to improve according to some authors (Jones et al. 1994; American Congress of Rehabilitation Medicine, 1995), although others have reported a stable mortality rate (Kraus and McArthur, 1996b). Any improvement in mortality and morbidity is likely to be the result of improved critical care techniques. Likewise, in patients with subarachnoid haemorrhage (SAH), advances in surgical and management techniques have led to improved mortality rates (Ropper and Zervas, 1984; Maurice-Williams and Kitchen, 1994). This present thesis aims to investigate the outcome of patients who survive severe or moderate TBI, or aneurysmal SAH, and the implications of this improved survival rate. 1.1 Traumatic Brain Injury Traumatic brain injury (TBI) has been variously defined. Definitions include 'damage to the brain and/or brain stem due to mechanical injury' (Powell, 1994) or 'brain injury caused by trauma to the head (including the effects upon the brain of other possible complications of injury notably hypoxaemia and hypotension, and intracerebral haematoma)' (Medical Disability Society, 1988). A particularly pertinent definition to this present thesis is 'an acquired injury to the brain caused by an external physical force resulting in total or partial disability or impairment' (U.S.Congress Senate, 1992). Traumatic injury to the brain is caused by a combination ofmovement of the head, and acceleration and deceleration forces on impact (Long and Webb, 1983). There are a number of ways in which this can occur. The head itselfmay be stationary when something hits it, as for instance, in the case of assault when the head may be hit with a baseball bat or