Successful conservative management for ruptured basilar artery perforator aneurysm associated with early hematoma expansion in right temporal lobe without aneurysm rerupture: illustrative case.

backgroundEarly intracerebral hematoma (ICH) expansion without aneurysm rerupture is extremely rare in patients with a ruptured basilar artery perforator aneurysm (BAPA), and the treatment strategy has not been established. OBSERVATIONS: A 47-year-old male was rushed to the authors' hospital due to loss of consciousness. CT imaging showed diffuse subarachnoid hemorrhage (SAH) and ventriculomegaly, and 3D CT angiography (CTA) showed a BAPA. Ventricular drainage was performed, and conservative treatment for the BAPA was started. However, CT imaging on SAH day 1 showed an enlarged ICH in the right temporal lobe with no increase of SAH. Subsequent CTA showed no contrast extravasation from the right middle cerebral artery and no detection of BAPA. Since the BAPA was not considered to have reruptured and there was no mass effect due to the ICH, conservative treatment was continued with close imaging studies. There was no rerupture of the BAPA, and ventriculoperitoneal shunt insertion was performed on SAH day 36. The patient was transferred to a rehabilitation hospital on SAH day 62 with a modified Rankin Scale score of 1 (mild attention disorder). LESSONS: Conservative management for a ruptured BAPA can be performed even in a case of early ICH enlargement without aneurysm rerupture. https://thejns.org/doi/10.3171/CASE25760.