Pineal cysts are benign and frequently asymptomatic, rarely causing mass effect on adjacent structures. Pineal apoplexy is a rare condition caused by hemorrhage into a pineal cyst. This phenomenon is poorly understood and poorly represented in the literature. We present the first reported case of pineal apoplexy presenting as thunderclap headache during pregnancy.

A 35-year-old G3P2002 woman at 35-weeks gestation presented with recurrent thunderclap headaches, transient vision loss, and right hand numbness. She had a known 1.3 x 0.75 x 0.95 cm pineal cyst on imaging ten years earlier. Initial neurological evaluation revealed neck tenderness without focal deficits. Given the acuity and intensity of her headaches, MRI of her brain without gadolinium was obtained and demonstrated a 1.6 x 1.3 x 1.1 cm pineal cyst with fluid level and hemosiderin rim suggesting pineal apoplexy. MRA and MRV did not reveal any vascular dissection, tortuosity, stenosis, or occlusion. There was no hydrocephalus and no acute neurosurgical intervention was required. She was managed conservatively and discharged to follow-up with neurology and obstetrics. Given her clinical improvement and history of two prior successful vaginal deliveries despite her known pineal cyst, she was cleared to proceed with vaginal delivery at 39 weeks, which was successful.

Although pineal cysts are common, pineal apoplexy is exceptionally rare, causing migrainous headaches in the only two prior reports in pregnancy. Thunderclap headache in pregnancy has never been reported from pineal apoplexy. Our patient had no prior history of headaches and developed recurrent thunderclap headaches acutely. Extrapolation from similar cases of pituitary apoplexy in pregnancy was utilized to guide care in light of the limited guidance available. We aim to highlight this rare phenomenon as a potential cause of thunderclap headache so future guidelines can be developed for best management.