Specific Imaging Findings

Teflon granuloma is seen as a focal calcification on CT images and tends to be hypointense on all MRI sequences. They may range from a few millimeters to a few centimeters in size and frequently enhance on post-contrast MR images. The typical location is in the cerebellopontine angle at the site of previous neurosurgical vascular decompression procedure. Granulomas are most commonly seen following surgery for intractable trigeminal neuralgia, characteristically at the root entry zone (REZ) of the nerve within the first few millimeters from the brainstem. The lesions are best depicted on high-resolution 3D MR images, either T2-weighted (such as CISS, DRIVE, FIESTA) or post-contrast T1-weighted, as elongated oval to round heterogenous structures, characteristically located between the vessel and the nerve or brainstem.

Pertinent Clinical Information

Microvascular decompression (MVD) is commonly performed for medically refractory trigeminal neuralgia (tic douloureux) and hemifacial spasm. A piece of polytetraluoroethylene (PTFE, Telon) is usually placed between the nerve (or pons) and the blood vessel compressing the nerve. Deleterious effects of this procedure are rare; however, cases of enlarging enhancing masses that were mistaken for neoplasms have been described. More commonly the patients present with recurrence of the initial symptomatology, usually within a few years, frequently accompanied by new facial numbness. Telon granuloma is found on surgical re-exploration, sometimes with prominent adhesions. Polyvinyl alcohol foam (Ivalon sponge) has also been used for MVD and may also lead to granulomatous reaction and scar formation. Cases of foreign-body granuloma occurring after craniotomy with dura-cranioplasty and other materials have also been described.