Background: van Gijn and co-workers identified "Perimesencephalic haemorrhage" (PM) as distinct, benign, non-aneurysmal subarachnoid haemorrhage. However, there is only one retrospective series of this entity outside the Netherlands.
Purpose: to confirm (or not) the benign nature of perimesencephalic subarachnoid haemorrhage by evaluating its clinical course and long-term follow-up in a consecutive series of patients admitted to a University Hospital.
Methods: Patients with subarachnoid haemorrhage and negative cerebral angiography admitted between January 1985 and April 1992 were classified according to the distribution of blood on a CT scan performed within 72 hours after onset, in perimesencephalic and non-perimesencephalic haemorrhages. Demographic and clinical data (collected consecutively), complications and long-term follow-up (obtained by chart review and follow-up by mail) were compared in the two groups.
Results: Seventy one cases, 36 perimesencephalic and 35 nonperimesencephalic were included. Sex and age distribution were similar in the two groups. A normal examination on admission was the rule in the perimesencephalic group. Only one patient with perimesencephalic haemorrhage had a complication--transient neurological signs during angiography--and there were no deaths or morbidity during follow-up. In the non-perimesencephalic group three patients rebleed, four developed hydrocephalus and two had delayed cerebral ischaemia. Mean duration of follow-up was 27.6 months for the perimesencephalic and 30.8 months for the non-perimesencephalic group. After discharge there was a fatal rebleed in the latter group. Fifteen percent of the subjects (11% of the perimesencephalic group and 20% of the non-perimesencephalic group) retired from work during the follow-up period. Headaches and depression were found in similar percentages (22-25%) in both groups.
Conclusions: This study confirms that perimesencephalic haemorrhage is a distinct entity within the larger group of subarachnoid haemorrhage with negative angiograms, with a good short term and long-term prognosis, and no need for repeated angiographic investigation.