Magnetic resonance imaging of perilymphatic fistula.

Perilymphatic fistula (PLF) is considered to be a most challenging otologic issue. There are no currently agreed upon objective tests for the diagnosis of PLF. In an effort to improve diagnostic accuracy in patients with suspected PLF, a novel diagnostic test involving magnetic resonance (MR) contrast imaging was designed. An experimental PLF was created in the cochlear round window membrane of healthy adult cats. Since cochlear perilymph is thought to be an ultrafiltrate of cerebral spinal fluid, gadodiamide (gadolinium-diethylenetriamine penta-acetic acid [DTPA] bismethylamide), a nonionic paramagnetic contrast agent, was injected intrathecally in an attempt to enhance imaging of the created fistula. Post-contrast images of the fistualized cochlea demonstrate a significant increase in the signal intensity of the cochlear perilymph with pooling of enhanced perilymph observed in the ipsilateral mastoid bulla. Magnetic resonance contrast imaging may prove to be a valuable technique in human studies involving perilymphatic fistula.