Trigeminal Neuralgia from Simultaneous Compression by Cerebellopontine Angle Epidermoid and Duplicated Superior...

A 51-year-old woman presented with 2 years of progressive left facial pain and numbness in maxillary nerve and mandibular nerve distributions. Symptoms were refractory to increasing doses of carbamazepine and gabapentin. Magnetic resonance imaging showed a left cerebellopontine angle nonenhancing mass, with diffusion restriction causing trigeminal nerve compression. Fast imaging employing steady-state acquisition sequences revealed a superior cerebellar artery loop in the angle between cranial nerve V and pons. The patient agreed to resection of the mass and microvascular decompression. Retrosigmoid craniotomy was performed with sensory/motor, and facial-auditory nerves' monitoring. The mass was densely adherent to cranial nerves VII-X and the anterior inferior cerebellar artery, causing compression at the root entry zone of the trigeminal nerve. It was carefully dissected off these structures; pathology confirmed an epidermoid. A large bony tubercle obscured visualization; therefore, a 30° endoscope was used. The tubercle was drilled, and remnant portions of the mass were removed. During mobilization of the superior cerebellar artery loop, it was found to be duplicated, and polytef (Teflon) pledgets were placed for microvascular decompression. The trigeminal nerve was thus discovered intraoperatively to be trapped simultaneously between the duplicated superior cerebellar artery loop from above and the epidermoid from below. Pain relief was immediate; at 12-month follow-up, the patient was pain-free, she had minimal numbness around the angle of the lip, and medications were discontinued. Facial nerve function and hearing were intact. A pure endoscopic approach is minimally invasive with a smaller incision and has been described for microvascular decompression for trigeminal neuralgia. Cerebrospinal fluid leak rates are expected to be lower. This technique has a steep learning curve and could pose a significant challenge for resection of lesions densely adherent to neurovascular structures. A pure microscopic approach generally involves a larger incision and can be better suited for resection of cerebellopontine angle lesions where bimanual dissection would be necessary. Visualization around corners in the presence of large bony protuberances (e.g., large suprameatal tubercle) around vessels and nerves in the depths is a drawback. Combining microscopic surgery with endoscopic assistance (especially angled endoscope) negates the disadvantages of either method alone, allowing for visualization around structures in the depths of the cerebellopontine angle where microscope lighting may be reduced, and provides a means to achieve gross total resection of tumor hidden from view.