1Department of Neurosurgery, Beaumont Hospital, Beaumont, Dublin 9
2Department of General Surgery, Wexford General Hospital, Wexford
Acute subdural haematoma (ASDH) is one of the conditions most strongly associated with severe brain injury.1 Reports prior to 1980 describe overall mortality rates for acute subdural haematomas (SDH's) ranging from 40% to 90% with poor outcomes observed in all age groups. Recently, improved results have been reported with rapid diagnosis and surgical treatment.2 The elderly are predisposed to bleeding due to normal cerebral atrophy related to aging, stretching the bridging veins from the dura.3 Prognosis in ASDH is associated with age, time from injury to treatment, presence of pupillary abnormalities, Glasgow Coma Score (GCS) or motor score on admission, immediate coma or lucid interval, computerized tomography findings (haematoma volume, degree of midline shift, associated intradural lesion, compression of basal cisterns), post-operative intracranial pressure and type of surgery.4 Advancing age is known to be a determinant of outcome in head injury.5 We present the results of a retrospective study carried out in Beaumont Hospital, Dublin, Ireland’s national neurosurgical centre. The aim of our study was to examine the impact of age on outcome in patients with ASDH following severe head injury. Only cases with acute subdural haematoma requiring surgical evacuation were recruited. Mortality was significantly higher in older patients (50% above 70 years, 25.6% between 40 and 70 years and 26% below 40 years). Overall poor outcome (defined as Glasgow outcome scores 3-5) was also higher in older patients; 74.1% above 70 years, 48% between 40 and 70 years and 30% below 40 years. Poor outcome in traumatic acute subdural haematoma is higher in elderly patients even after surgical intervention.
We collected data on patients admitted to Beaumont Hospital from January 1999 to December 2003. This included data from referral letters, admission and inpatient notes, radiology and laboratory reports, outpatient follow up notes and records of death. Of 6575 patients with head injury referred to our department (average 1315 per year) during this period, 150 had ASDH. Following thorough review of patients’ records, 134 cases were included in the study, based on explicit inclusion and exclusion criteria. Cases were assigned to one of three groups: group A up to 40 years, B from 40 to 70 years and C above 70 years. Patients with gunshot wounds to the head were excluded as mortality rate is uniformly high irrespective of age. Also excluded were patients meeting clinical criteria for brain death on arrival in hospital, non-surgical acute subdural haematoma and acute on chronic subdural haematoma.
For inclusion in the study, medical records for each case had to delineate the admission GCS, treatment and outcome to a point at least six months from the time of treatment. Only cases with acute subdural haematoma thicker than 0.5 cm on CT scan, and needing surgical evacuation were included. Clinical data collected included age, sex, mechanism of injury, GCS on admission and initial CT findings. Others were time from injury to emergency room admission, from admission to start of surgery, and time from surgery to death. Cause of death, length of hospital stay and Glasgow Outcome Score (GOS) at six months were also included. The GOS category as described by Jennett and Bond6 was determined in surviving patients from a follow up clinical visit. The five GOS categories are good, moderately disabled, severely disabled, vegetative and death, respectively corresponding to categories 1-5. We divided patient outcomes into favourable (GOS 1 and 2) and unfavourable (GOS 3, 4 and 5).
Of 134 cases studied, 101 were male and 33 female. In group A there were 23 patients (n = 23). This represented 17% of patients. Of these 22 were male patients while there was only 1 female (Table 1). Eleven patients in this category sustained severe head injury (GCS 3 to 8). Of 82 patients in group B (n=82, 63% of patients), there were 63 males and 19 females. Forty nine patients sustained severe head injury (Tables 1 and 2). Number of patients in group C was 29 (n=29; 20% of total). Distribution by gender was 16 males and 13 females. Seventeen sustained severe head injury (Tables 1 and 2).
Mechanism of injury also varied between the groups. In young patients (group A) the leading cause of head injury was road traffic accidents (RTA) followed by falls and assault while in Group B, leading cause of injury was falls (56 of 82) followed by RTA and assault. In group C, majority of patients sustained simple falls (20 out of 26) while 2 were involved in RTA. All unconscious patients were initially evaluated and resuscitated by paramedics onsite. All patients irrespective of age with admission GCS score of 8 or less were intubated in the referring hospitals prior to transfer. Patients already intubated from referring hospitals were operated within six hours of admission to Beaumont hospital except 17 patients who were on warfarin and required time for reversal of anticoagulation.
Majority of patients presented with severe head injury (GCS 3 to 8); 11 patients in group A, 49 in B and 17 in C (Table 2). Neurological status in the younger patients (Groups A and C) did not deteriorate significantly between the time of admission and start of emergency surgery in contrast to older patients (Group C) among whom 5 patients with initial GCS of 13 to 15 deteriorated to 8 or less and ended up in the severe head injury category. After initial resuscitation all unconscious patients were given oxygen and haemodynamically stabilized, and those with signs of brainstem dysfunction or abnormal motor movements received mannitol. Neurosurgical treatment of patients with ASDH diagnosed by CT scan consists of a wide craniotomy, haematoma evacuation +/- continuous intracranial pressure (ICP) monitoring. The distribution of types of surgical treatment did not vary significantly between age groups. In terms of outcome, patients were broadly classified into favourable (GOS 1-2) and unfavourable (GOS 3-5) categories. The overall mortality rate was significantly higher in older patients (Group C) - 50% (n=13) in Group C, 25.6% (n=21) in B and 26% (n=6) in A (Table 3).
Overall outcome was as follows
In those below 40 years, one patient (4%) was severely disabled and with 26% (n=6) mortality there was unfavourable outcome of 30% and good outcome of 70 %. Between 40 and 70 years, 25.6% (n=21) had GOS 3 and 4. Added to the 25.6% (n=21) mortality, there was 52% unfavourable outcome. 48% had favourable outcome. Over 70 years, 24.1% (n=7) were severely disabled or vegetative in addition to the 50% mortality (n=13), a 74.1% unfavourable outcome. 25.9% had favourable outcome, all of whom had moderate or mild head injury on initial presentation. We performed a subgroup analysis of patients with severe head injury. In group A (<40 years), all surviving patients with severe head injury made good recovery. Four patients however died. 49 cases in group B (40-70 years) were classified as severe. Just under half (48.97%) had unfavourable outcome. Of the 17 patients in group C (>70 years) with severe head injury, 13 died. The remaining 4 had poor outcomes. This was an unfavourable outcome rate of 100%.
Patient age is thought to be a strong predictor of morbidity and mortality following severe closed head injury.7 Some authors have suggested that one of the pathophysiological mechanisms behind this effect may be due to increased sensitivity to ischaemic brain damage associated with mitochondrial dysfunction seen both with advancing age and severe head injury.8 Although some of this increased mortality may be explained by other factors, age itself is an independent predictor for mortality in this age group.9 This review of patients treated in our centre reveals divergent outcomes in younger patients (Groups A and B) versus older age (Group C). This confirms numerous prior studies showing that elderly patients suffering head injury have a higher rate of mortality and morbidity than younger individuals with similar injury. The timing of mortality also differs. Older patients have a greater likelihood of dying at later time post injury than patients in younger age groups although the survival rate within 48 hours following injury is similar for all age categories.
Aetiology of head injury changes across the age spectrum. Falls and pedestrian injury become more common in older age groups while the incidence of RTA declines. An increasing incidence of sensory deficit, muscle weakness, gait unsteadiness and arrhythmia contribute to the higher risk of falls in older patients. Greater lethality of ASDH relative to other brain lesions is well documented.7 Older patients are especially predisposed to intracranial mass lesions, particularly subdural haematoma regardless of injury mechanism. The reasons for this haemorrhagic tendency may include cerebral atrophy with change in the viscoelastic properties of the brain, alterations in the mechanical properties of the bridging veins and stress on venous structures secondary to cerebral atrophy. Patients with acute subdural haematoma reviewed in this study were treated according to standard protocols in all age groups; time from injury to initiation of treatment did not differ significantly between the old and young groups. As a group the mortality rate in young patients (Group A) was 26% and 70% of young patients were functional survivors. In this group, encouraging results were noted even in those patients with severe head injury with outcome of functional survival in 64%. A decline in these figures was noted with increasing age. In groups B and C, respective mortality rates were 50 % and 26% with functional survival of 48% and 23%. In older patients (Group C) there were no functional survivors among those with severe head injury.
Poor outcome in elderly patients in our study is similar to recently published studies of smaller groups of elderly patients with acute subdural haematoma2,7 and appears relatively unchanged from pre-1980 reports. There are many possible explanations for poor outcome. Older patients may have a more destructive injury than young patients. Acute subdural haematoma volume in older patients is on average more than four times and causes twice the amount of midline shift as in younger patients.10 Another important factor to consider is the possibility that the aging brain has impaired regenerative capacity. Furthermore, several medical conditions are more prevalent in old age, such as ischaemic heart disease, hypertension, chronic obstructive airway disease and diabetes mellitus. Such illnesses are known to impact negatively on outcome in elderly trauma victims. It is clear that age must be considered an important component of outcome prediction in head injury. Our findings raise questions about the ability of medical intervention to prevent the poorer outcomes associated with increased age and this should be considered when evaluating intervention options for severe head injury. Our findings also indicate the need to focus attention on the neurobiological changes associated with aging as a means to better understanding and perhaps influencing outcome associated with increasing age.
Correspondence: S Hanif
Department of Neurosurgery, Beaumont Hospital, Beaumont, Dublin 9
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