"Kissing" Brainstem Cavernous Angiomas Removed Using a Trans-Fourth Ventricular Floor Approach -Case Report-

Abstract

A 39-year-old woman presented with a rare case of``kissing'' brainstem cavernomas formed by separate lesions enlarging with simultaneous recurrent hemorrhages, which was successfully treated by staged resection using a trans-fourth ventricular floor approach. She had a familial history of cerebral cavernous angioma, and presented with a history of four episodes of sudden neurological deterioration. Magnetic resonance (MR) imaging obtained at each neurological event demonstrated two distinct brainstem cavernomas located in the pontine tegmentum and ventral part of the lower pons, both of which enlarged stepwise caused by simultaneous recurrent hemorrhages. Both cavernomas contacted and formed``kissing'' lesions. She underwent midline suboccipital craniotomy in the prone position. The cavernoma in the pontine tegmentum was resected through a trans-fourth ventricular floor approach. Although``kissing'' formation appeared on preoperative MR imaging, parenchyma was identified at the bottom of the removal cavity of the dorsal lesion, and resection was terminated. MR imaging following the first surgery revealed complete resection of the pontine tegmentum cavernoma and the ventral pontine cavernoma, which was located adjacent to the bottom of the removal cavity and aligned in same direction along the fourth ventricular floor approach. At 10 days after first surgery, she underwent the same procedure with the aid of neuronavigation to resect the ventral pontine cavernoma through the former removal cavity. This approach through the previous removal route, particularly for resection of`k issing'' lesions which are difficult to access in the brainstem, is a technically feasible microsurgical procedure.

Intraoperative facial motor evoked potential monitoring for pontine cavernous malformation resection

“…Access to pontine lesion generally recommended from area which bulging of the lesion is visible, or adjacent surface of the lesion. 14 Trans-fourth ventricular floor approach is indicated when the lesion is located dorsally near or protruding to the fourth ventricular floor under above-mentioned brainstem mapping and/or monitoring is available, although it has been described by some authors that lateral suboccipital retrosigmoid approach via the cerebellar peduncle for dorsal pontine surgery reduces manipulation of structures in the fourth ventricular floor. 3,10 Brainstem vascularization does not comes from fourth ventricular floor surface, but from perforating arteries on it's ventral or lateral side, and upper motor neuron part of facial motor pathway located in ventrolateral part of the pons.…”

“…10) underwent an intentional staged surgery. 14 Facial nerve examination with House-Brackmann scale, and other cranial nerves functions were assessed pre-and postoperatively at discharge. Karnofsky Performance Scale (KPS) score was obtained prior to the surgery and during a 6-month follow-up.…”