Case report of unusual cause of trigeminal neuralgia: Trigeminal neuralgia secondary to enlarged suprameatal tubercle

Abstract

Background Classic trigeminal neuralgia (TN) is caused by vessels compressing the trigeminal nerve root entry zone. The cause is usually impingement of the superior cerebellar artery, anterior inferior cerebellar artery, or a vein. Other rare causes have been reported including aneurysmal compression, skull base tumors, and vascular malformations. An enlarged suprameatal tubercle (EST) as a cause of TN has not yet been described. Case presentation We report the first case of 37 year old female patient presented with severe TN involving the three branches of trigeminal nerve who failed medical treatment and underwent multiple balloon compression for left TN with minimal improvement. The severity of pain was assessed using Barrow Neurological Institute (BNI) pain intensity score. Patient had brain MRI with CISS sequence and CT scan for the brain. After careful revision of her imaging studies, patient found to have prominent and heavily calcified left supra meatal tubercle. Her preoperative BNI score was 5. Patient had left retrosigmoid craniotomy and drilling of left suprameatal tubercle. No other structures were seen in contact with left trigeminal nerve root entry zone. Patient had significant improvement on her pain, postoperative BNI score was 1 until the last follow-up 4 years. Conclusion EST is a rare cause of TGN and should be suspected as the offending compressing structure when no other causes seen on imaging studies.

Surgical Nuances and Predictors of Requirement for Suprameatal Tubercle Removal in Microvascular Decompression for Trigeminal Neuralgia

“…causing the direct bony compression of the trigeminal nerve. 15 Several factors are known to be associated with the technical difficulty of trigeminal nerve MVD, including the involvement of dolichoectatic vertebrobasilar arteries as an offending vessel, 17 well-developed SPV complexes as a vascular obstacle, 14 and enlarged SMTs as a bony obstacle. [3][4][5][6][7][8][9][10] Multivariate analysis with logistic regression, performed in the present study, indicated that an enlarged SMT and a multiple number of offending vessels are indicative of the need for SMT removal during trigeminal MVD.…”

“…Surgical outcomes were assessed at a median follow-up duration of 3.6 years after surgery (range, 18 months-10 years), and categorized according to the Barrow Neurological Institute (BNI) pain intensity score, as follows: I-no pain; IIoccasional pain without medications; III-some pain, adequately controlled with medications; IV-some pain, not adequately controlled with medications; and V-severe pain or no pain relief with medications. 15 The study population was divided into two groups: patients who underwent SMT removal (n ¼ 20) and those who did not (n ¼ 177). Variables, including SMT height, clinical characteristics, surgical findings, and outcomes, were evaluated and compared between the two groups.…”