SUMMARY Computed tomography demonstrated a haematoma in the region of the basal ganglia in 61 of 2000 head injured patients. In 41 the haematoma occurred as an isolated lesion while in 20 there was another associated intracranial haematoma. Clinical and radiological differences within these groups are discussed. The patients with basal ganglia haematoma were more severely injured than those in a group who had an intracranial haematoma evacuated by craniotomy and the findings closely resembled those of a group of patients who had sustained diffuse brain damage. They share many features with those of patients with diffuse white matter injury and have a worse prognosis than other traumatic intracranial haematomas.Computed tomography (CT) has proved to be of enormous value in the assessment of traumatic intracranial haematomas and has led to improved clinical management with significant reductions in morbidity and mortality.' CT also demonstrates the effects of diffuse brain injury, though unfortunately the outcome for patients shown to have suffered this type of damage has not been similarly improved. It is only since the advent of CT that one has been able to identify in life small haematomas in the region of the basal ganglia. Basal ganglia haematomas were infrequently described before the scanning era2 and most reports since have concerned very large lesions.3 This study investigates the cause of injury, the clinical features, the CT appearances, and the outcome of a series of patients with basal ganglia haematoma, and considers the possible mechanisms responsible for these haematomas. It also assesses how the features of this group compare with those in a surgically treated group of patients with traumatic intracranial haematoma, and with a group of patients who sustained diffuse brain injury. The scans of 2000 of the head injured patients admitted during the period 1979-1983 were reviewed retrospectively by one of us (PM) and 61 were found to have a haematoma in the basal ganglia region. These patients were then sub-divided into a group in which the basal ganglia haematoma occurred as an isolated lesion (41) and one in which the haematoma was associated with another intracranial haematoma (20). The former group were further sub-divided by CT appearances into those with normal intracranial pressure (20) and those with evidence of raised intracranial pressure (18); that is presence or absence of the 3rd ventricle with or without absent basal cisterns, such findings being consistent with an intracranial -pressure of >20 mm Hg.4 Three patients had a large isolated basal ganglia haematoma causing midline displacement of >5 mm with resulting direct ventricular compression, and were considered separately. In the associated group, the second haematoma was intracerebral in 11, subdural in five and extradural in four.Clinical information concerning age, cause of accident, lucid intervals, focal signs and conscious levels (Glasgow Coma Scale5) were obtained from a retrospective analysis of the case records and this infor...