Cerebellar Quadrangular Lobule Resection for Microsurgical Treatment of a Pontine Cavernous Malformation via the Trans-Middle Cerebellar Peduncle Approach

The pons is the most common site for brainstem cavernous malformations. 1-3 Lesions in this region seem to be more aggressive than superficial lesions and often present unique surgical challenges due to their depth and proximity to eloquent structures. 1,4-7 The cerebellar-mesencephalic fissure and the cerebellar interpeduncular region 7-8 serve as critical microsurgical corridors for approaching intrinsic lesions of the posterolateral pons. 8-13 However, their access is limited by surrounding structures such as the superior and middle cerebellar peduncles, dentate nucleus, and pontine fiber tracts. 4,6-8,11 Anatomical studies have shown that partial resection of the cranial portion of the quadrangular lobule of the cerebellum (QLC) significantly enhances the operative corridor by improving the angle of attack and expanding visualization, while respecting known safe entry zones near the interpeduncular sulcus. 8-16 We present the case of a 32-year-old right-handed male with acute headache and right-predominant tetraparesis. MRI revealed a hemorrhagic dorsolateral pontine cavernous malformation with a surrounding hemosiderin ring and compression of the fourth ventricle. A microsurgical resection was performed via supracerebellar infratentorial approach. A minimal resection of the cranial quadrangular lobule improved both craniocaudal and mediolateral visualization, facilitating complete and safe excision of the lesion. Postoperative MRI and CT confirmed a gross-total resection. Objective outcome was GCS 15/15, mRS 1/6, no cranial nerve deficits, and improved strength (5/5 left; 4/5 right). Discharge occurred on postoperative day 14. In carefully selected dorsolateral pontine cavernous malformations, a minimal QLC resection can expand operative freedom while respecting functional boundaries and vascular preservation principles with favorable postoperative functional outcomes.