Resection of dorsal midbrain cavernous malformation through Reil's (lemniscal) trigone

Cavernous malformations of the dorsal midbrain present surgical challenges due to proximity to critical structures.

We present the case of a 37-year-old female who presented with left trochlear nerve palsy, left hemibody sensory loss, and left upper and lower extremity 4/5 weakness following ventriculoperitoneal shunting at an outside hospital for treatment of a brainstem hemorrhage. Magnetic resonance imaging showed a hemorrhagic lesion, consistent with cavernous malformation, in the dorsal midbrain. Her symptomatic growing cavernous malformation and significant mass effect were the indications for operative intervention. The paramedian supracerebellar infratentorial surgical approach was selected to minimize intersection with deep venous structures. Gross total resection of the malformation was observed on operative endoscopic inspection and postoperative imaging. She was discharged home on postoperative day 3, and by 3-month follow-up, her diplopia and hemi-body sensory loss had resolved. An anatomical review of approaches for dorsal brainstem lesions and the technical considerations of utilizing the lemniscal trigone, as well as positioning, cistern magna access for cerebrospinal fluid (CSF) relief, and endoscopic inspection are included. The patient consented to the procedure and to the presentation of her images. Institutional review board approval was deemed unnecessary due to the retrospective, case-report nature of this work.

The case highlights the utility of the paramedian supracerebellar infratentorial approach for safe, effective resection of dorsal midbrain cavernous malformations. Careful anatomical planning, endoscopic assistance, and CSF drainage strategies can optimize outcomes and minimize morbidity in this challenging anatomical region.