Trigeminal Neuralgia Caused Purely by Hyperostosis of the Suprameatal Tubercle: Report of a Rare Case

Objective: Trigeminal neuralgia (TN) is usually caused by vascular compression of a vessel at the root entry zone (REZ) if the trigeminal nerve. Less frequently, TN could be caused by space occupying lesions in the CPA.

Methods: We present a case of typical TN caused purely by an hyperostosis of the suprameatal tubercle. A 46 woman was referred to our institution presenting a typical Trigeminal Neuralgia refractory to medical therapy. An MRI was performed showing an hyperostosis of the suprameatal tubercle and a suspect neurovascular conflict, no Gadolinium enhancement was present. High-resolution CT scan confirmed the presence of the hyperostosis of the suprameatal tubercle. The patient was then operated via a retrosigmoid approach; the bony hyperostosis was then removed completely, thus decompressing the nerve. The nerve was inspected thoroughly and no vascular compression was found.

Results: The patient's trigeminal neuralgia ceased completely after the operation. Postoperative high-resolution CT scan showed complete removal of the hyperostosis.

Conclusion: Although trigeminal neuralgia caused by a tumor in the CPA is not rare, only few reports exist in literature of TN caused by hyperostosis and all of them were related to the presence of small meningiomas. In this case, we did not find any tumor, so we assume the cause of the trigeminal neuralgia was an increase of pressure on the trigeminal nerve root due the bone compression of the nerve as well as anatomical features (brain sagging, shorter trigeminal cisternal segment, smaller CPA cisterns) of TN as described elsewhere in the literature.