Diagnostic and Surgical Management of a Thrombosed Distal PICA Aneurysm: A Selected Case Report and Review from a Retrospective Institutional Series.

BACKGROUND

Distal posterior inferior cerebellar artery (PICA) aneurysms are rare vascular lesions, comprising less than 0.5% of all intracranial aneurysms. When thrombosed, they can mimic neoplastic or infectious processes, leading to delayed diagnosis and potential mismanagement. The complex anatomy of the PICA and its variable relationships with adjacent neurovascular structures further complicate both the diagnostic process and surgical approach. Here, we present a rare case of a thrombosed distal PICA aneurysm, with emphasis on imaging characteristics, differential diagnosis, and surgical considerations.

CASE PRESENTATION: A 55-year-old man presented with progressive occipital headache, gait ataxia, and dysmetria. Magnetic resonance imaging (MRI) revealed a 1.6 cm lesion in the left cerebellar hemisphere with central T1 hyperintensity and peripheral enhancement, suggestive of a thrombosed aneurysm or mass. Digital subtraction angiography (DSA) confirmed a partially thrombosed saccular aneurysm at the telovelotonsillar segment of the left PICA. Surgical management involved a left suboccipital craniotomy with microsurgical clipping and thrombectomy. Intraoperative findings confirmed a saccular aneurysm with dense intraluminal thrombus adherent to surrounding cerebellar tissue. Histopathology demonstrated organized thrombus with vascular wall disruption and neovascularization, consistent with chronic aneurysmal changes. Postoperative recovery was uneventful, and the patient was discharged with full neurological function restored. Follow-up imaging showed no residual aneurysm.

CONCLUSION

Thrombosed distal PICA aneurysms pose a diagnostic challenge due to their atypical radiologic appearance and potential to mimic neoplastic lesions. Recognition of characteristic imaging features, such as peripheral enhancement and central hyperintensity on MRI, can aid early diagnosis and prevent mismanagement. Surgical intervention remains the definitive treatment, requiring careful planning due to the complex vascular territory of the distal PICA. Awareness of this rare entity among radiologists and neurosurgeons is critical to guide accurate diagnosis, avoid misinterpretation, and optimize patient outcomes.