An aberrant venous channel mimicking the perilabyrinthine cells in the petrous bone of a patient with vestibular schwannoma: illustrative case.

BACKGROUND: Anatomical variations, such as high jugular bulbs and air cell development in the petrosal bone, should be evaluated before surgery. Most bone defects in the internal auditory canal (IAC) posterior wall are observed in the perilabyrinthine cells. An aberrant vascular structure passing through the petrous bone is rare. OBSERVATIONS: A 48-year-old man presented with a right ear hearing disturbance. Magnetic resonance imaging revealed a 23-mm contrast-enhancing mass in the right cerebellopontine angle extending into the IAC, consistent with a right vestibular schwannoma. Preoperative bone window computed tomographic scans showed bone defects in the IAC posterior wall, which ran farther posteroinferiorly in the petrous bone, reaching the medial part of the jugular bulb. The tumor was accessed via a lateral suboccipital approach. There was no other major vein in the cerebellomedullary cistern, except for the vein running from the brain stem to the IAC posterior wall. To avoid complications due to venous congestion, the authors did not drill out the IAC posterior wall or remove the tumor in the IAC. LESSONS: Several aberrant veins in the petrous bone are primitive head sinus remnants. Although rare, their surgical implication is critical in patients with vestibular schwannomas.