Recurrent trigeminal neuralgia due to granulomatous change in a prosthesis for microvascular decompression: A case report

A case of recurrent trigeminal neuralgia due to granulomatous change in a prosthesis (Teflon felt) for microvascular decompression (MVD) is reported. A 40-year-old woman experiencing right trigeminal neuralgia presented at our institution. A Teflon felt prosthesis was inserted between the caudal loops of the duplicated superior cerebellar arteries (SCAs) and the pons for MVD. The symptoms of neuralgia resolved immediately after surgery. Two months after surgery, the trigeminal neuralgia recurred and was controlled by carbamazepine (CBZ) administration. Three years thereafter, the pain suddenly became severe and was no longer controllable with CBZ. Radiographic images showed typical findings of granuloma in the right prepontine cistern. The granuloma size subsequently increased, and a second surgery was performed. The root entry zone of the trigeminal nerve and SCAs, where the Teflon felt was inserted at the time of the first surgery, were completely covered by a soft, white, granulomatous mass and the prosthesis adhered to the nerve and SCAs. Most of the prosthesis was removed, and the SCAs were attached to the interior surface of the cerbellar tentorium. The pain resolved soon after the second surgery, although slight hypesthesia of the right cheek remained. The patient's postoperative status has been uneventful during 10 months of follow-up. Histological examination revealed that the mass was a granuloma. In this patient, the CT findings were characterized by an abnormally long duration of marked enhancement and increased size of the lesion, which were compatible with a diagnosis of granuloma. It should be borne in mind that granulomatous changes in prostheses may result in early recurrence of trigeminal neuralgia. Therefore patients with early recurrence should be followed up with CT scanning, since the results of surgical removal of the prosthesis and granuloma are good.