Subarachnoid haemorrhage of unknown origin: clinical and tomographical aspects.

65 patients with negative but technically satisfactory 4 vessel angiography - all admitted to our Department in the years 1976-1983 - were evaluated in the present study. CT scan was undertaken in all cases (in 47 cases within 4 days of haemorrhage). Arterial hypertension was present on admission in 9% of cases. The period of follow-up ranged from 4 to 11 years, with a mean of 5.3 years. The study group was compared to a control group, comprising 760 patients with subarachnoid haemorrhage from ruptured aneurysms, admitted during the same period. Clinical grade on admission (Hunt's classification) was better in patients belonging to the study group. The amount of cisternal deposition on CT scan was less significant than in patients with ruptured aneurysms, and the deposition was often atypical (circumpeduncular, ambiental, and/or tentorial). Clinical deterioration associated with vasospasm was observed in 5% of patients in this study and in 27% of patients in the control group. In patients with a consistent or thick cisternal layer (CT scan "at risk") the incidence of clinical vasospasm was 21%, against 47% in controls. One or more rebleedings occurred in 12% of patients in the study group, against 25% of patients in the control group. A significant ventricular dilatation was observed in 15% of patients in the first group (requiring a shunt in 8%), against 25% of patients in the second group (requiring a shunt in 11%). Final outcome was favourable in 95% of patients in this study group and in 63% of patients in the control group, with a mortality rate of 5% in the first group and 32% in the second group.