Recurrent Perimesencephalic Subarachnoid Hemorrhage After 12 Years: Missed Diagnosis, Vulnerable Anatomy, or Random Events?

BACKGROUND

Perimesencephalic subarachnoid hemorrhage (PMSAH) is a well-defined subtype of angiogram-negative SAH, characterized by a benign natural history and a virtually nonexistent risk of recurrence. Few case reports of recurrent PMSAH exist in the literature, all occurring after relatively short time intervals ranging from 5 days to 31 months, mostly in patients on antithrombotic therapy. We present a unique case of ultra-late PMSAH recurrence after 12 years, in a patient not receiving antithrombotic medications.

CASE DESCRIPTION: A woman presented with 2 similar episodes of sudden-onset severe headache and neck pain, without associated neurologic deficits: a first episode at the age of 48 years and a second at 60 years. In each instance, the pattern of hemorrhage was consistent with PMSAH, platelet count and coagulation tests were normal, and a full etiologic work-up, including CTA, catheter angiography, and magnetic resonance imaging, failed to reveal an underlying vascular or tumoral etiology. The patient had a favorable clinical course each time.

CONCLUSIONS

Although exceptional, recurrence of PMSAH is not impossible. If the 2 events are assumed to be random and independent of each other, binomial statistics yield approximately a 79 per billion chance of 2 or more episodes occurring over an 80-year lifetime. However, other possibilities should be kept in mind, including tiny and radiographically occult vascular lesions or particular venous anatomy predisposing patients to recurrent bouts of PMSAH. Patients should not be told that the risk of recurrence is zero, but that it is close to zero.