TITLE:
Third Cranial Nerve Palsy Complicating Peri Mesencephalic Non Aneurysmal Subarachnoid Hemorrhage: A Case Report
AUTHORS:
Zineb Bayoum, Mounia Rahmani, Meriem Fikri, Najoua Maarad, Wadie Bnouhanna, Maria Benabdeljlil, Saadia Aidi
KEYWORDS:
Peri Mesencephalic Hemorrhage, Non-Aneurysmal Subarachnoid Hemorrhage, Third Cranial Nerve Palsy
JOURNAL NAME:
Open Access Library Journal,
Vol.12 No.7,
July
8,
2025
ABSTRACT: Background and Clinical Significance: Peri-mesencephalic hemorrhage is a rare and benign type of subarachnoid hemorrhage (SAH) defined by the presence of SAH in peri-pontic and peri-mesencephalic cisterns, with no aneurysm or other source of bleeding on angiography. Cranial nerve involvement is very rare and has been rarely reported in the previous studies. Peri mesencephalic subarachnoid hemorrhage (PMSAH) typically presents with benign clinical symptoms such as headache and neck pain and cranial nerve involvement is extremely uncommon, with only few cases documented in the literature. Understanding the pathophysiology and clinical spectrum of PMSAH is essential to avoid misdiagnosis and unnecessary interventions. Case Presentation: We report the case of a 51-year-old man with a non-controlled type 2 diabetes mellitus who presented with sudden onset thunderclap headache following sexual activity. One week later, he developed vertical binocular diplopia and partial right-sided ptosis. Neurological examination revealed a partial third cranial nerve palsy affecting all ocular movements except abduction, along with absent direct and consensual pupillary light reflexes on the right. Brain MRI showed a typical PMSAH and cerebral angiography performed 12 days after symptom onset ruled out aneurysm or vasospasm. Patient was managed conservatively with symptomatic treatment and diabetes optimization, resulting in complete resolution of cranial nerve palsy after three months. Conclusion: This case highlights an unusual presentation of PMSAH complicated by isolated third cranial nerve palsy in the context of poorly controlled diabetes and post-coital effort. Recognizing these rare manifestations can prevent unnecessary invasive procedures and guide appropriate management. Further studies are warranted to better understand the pathophysiology of cranial nerve involvement in PMSAH.