Trigeminal Neuralgia (TGN) Secondary to Enlarged Suprameatal Tubercle (EST)

Introduction: Classic trigeminal neuralgia is caused by vessels compressing the trigeminal nerve root entry zone. The culprit is usually the superior cerebellar artery, anterior inferior cerebellar artery, or a vein. Multiple rare causes have been reported including aneurysmal compression, skull base tumors, and vascular malformations. Enlarged suprameatal tubercle as a cause of TGN has not been described. We present a patient that had complete pain relief after resecting the suprameatal tubercle (ST) to decompress the root entry zone of the trigeminal nerve.

Methods: We reviewed retrospectively a patient chart presented with medically refractory TGN. The patient demographics, clinical data, and radiological images were included after obtaining the patient's consent. Pain severity was scaled using the Barrow Neurological Institute (BNI) Pain Intensity score. On preoperative MRI and CT scan of the brain, there was a large left ST causing compression of the root entry zone (REZ) of the trigeminal nerve (TN; [Fig. 1]). The patient was 37-year-old right-handed female who failed medical management and multiple percutaneous balloon compressions of the left sided TGN. The pain started in the V2 distribution and then involved all three branches. The preoperative pain was scored at 5. Microsurgical images from the surgery were used.

Results: We performed a left retrosigmoid craniotomy and an enlarged ST was encountered and drilled. The REZ of the TN was decompressed. Patient had complete relief of her symptoms in the immediate postoperative period. Microsurgical demonstration of the drilling is illustrated ([Fig. 2]). BNI pain intensity score was 1 until the last follow-up at 48 months. Postoperative CT scan was obtained ([Fig. 1D]).

Conclusion: EST is a rare cause of TGN that should be considered in patients with no other aberrant causes of nerve root entry zone compression. A careful reviewing of the preoperative scan must be done to rule out any nonvascular causes both on MRI and CT scan.

Fig. 1 (A) Preoperative MRI brain Coronal T2 CISS showing left enlarged ST in close proximity to TN (B) Axial T2 CISS REZ. (C) CT scan brain axial cut bone window showing left prominent ST. (D) Postoperative CT scan after drilling of the suprameatal tubercle. CT, computed tomography; ST, suprameatal tubercle; TN, trigeminal nerve.

Fig. 2 Demonstration of (A) Retrosigmoid craniotomy. (B) Before microscopic EST drilling. (C) After drilling (Impingement is noted on the nerve). EST, enlarged suprameatal tubercle.

Publication History

Article published online:
12 February 2021