26 A Large Cerebellopontine Angle Arteriovenous Malformation

26

A Large Cerebellopontine Angle Arteriovenous Malformation

KAZUHIKO NOZAKI AND NOBUO HASHIMOTO

Diagnosis A cerebellopontine angle arteriovenous malformation fed by the anterior inferior cerebellar artery and the posterior inferior cerebellar arteries

Problems and Tactics A large cerebellopontine angle arteriovenous malformation (AVM) with two hemorrhagic episodes had not been treated because of its vascular complexity and vicinity to vital neural structures. Surgical extirpation was applied to eliminate the risk of hemorrhage, and the AVM was successfully removed using stepwise clip applications on feeding arteries and intraoperative angiography.

Keywords AVM, cerebellopontine angle, temporary clip, intraoperative angiography

Clinical Presentation

This 43-year-old woman suffered from two episodes of hemorrhage. She was transferred to a hospital in a comatose condition at 24 years of age and ventriculoperitoneal (V-P) shunt and tracheostomy were performed. Although her clinical condition had gradually improved and she was able to stand and walk with aid, a second hemorrhage occurred at 43 years of age. Angiograms showed a large cerebellopontine angle AVM fed by multiple branches of the left anterior inferior cerebellar artery (AICA) and posterior inferior cerebellar arteries (PICAs) on both sides and draining into the left petrosal vein (Fig. 26–1).

Surgical Technique

The patient was placed in the right lateral position after the placement of a catheter in the left vertebral artery. A C-arm fluoroscopy for intraoperative angiography was set. A left suboccipital craniotomy was performed. After durotomy, the cerebellomedullary cistern was opened. A gentle retraction of the left cerebellar hemisphere with a spatula revealed the nidus in the left cerebellopontine angle cistern, and left lower cranial nerves and seventh to eighth nerves were surrounded by small vascular tangles, which were fed by the left PICA and AICA. The left petrosal vein was dilated as a varix adjacent to the left fifth nerve and drained into the left superior petrosal sinus. Most of the nidus seemed to locate epipially, and the dorsal surface of the nidus faced the old hematoma cavity in the left cerebellar hemisphere.

To clarify the anatomical relationship of the main feeding arteries, nidus, and draining veins, intraoperative angiography was performed after the temporary clip application on the proximal portion of the left AICA. It showed that the left PICA fed the nidus from its dorsal side. First, a temporary clip was applied to the proximal portion of the left AICA, and the small branches to the nidus from the left AICA were meticulously coagulated and cut at the proximity to the nidus, and the main trunk of the AICA feeding normal brain tissue was preserved (Fig. 26–2A). The nidus was carefully dissected from the left seventh through eleventh cranial nerves and the brain stem, without coagulation of its surface. During the dissection of the nidus, small branches to the nidus from the bilateral PICA were also coagulated and cut step by step using the same clip application technique (Fig. 26–2B

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