Neurosurgical interventions at the cochlear nerve & nucleus for treatment of tinnitus
Tinnitus is the perception of sound or noise in the absence of a physical sound source. For some patients, tinnitus has a significant impact on their quality of life and conventional treatment options can be insufficient. In this thesis, we evaluated and investigated several neurosurgical treatment options for patients with severe, intractable tinnitus. Tinnitus can be the result of compression of the cochlear nerve with a blood vessel (neurovascular conflict). In this thesis, we showed that a decompression surgery for this conflict has a low success percentage and a relatively high surgical complication rate. However, when patients experience both tinnitus and vertigo, the success percentage is considerably higher. A neurovascular conflict may be diagnosed with MR-imaging, however they do not always relate to ipsilateral symptoms. Our research showed that the type of compression, e.g. causing a dimple in the nerve, is not a good indicator for a symptomatic neurovascular conflict.In order to reduce tinnitus, neurostimulation can be performed. The effect of direct stimulation of the cochlear nerve with a ring electrode was evaluated, but appeared to be not a viable treatment option as damage of the nerve lead to increase in hearing loss in the majority of patients. Another novel option is neurostimulation of the cochlear nucleus in the brainstem with an auditory brainstem implant (ABI). We described a pilot study studying the effect of the ABI on tinnitus. Preliminary results (one year follow-up) in two patients show a stable tinnitus reduction. Also, hearing ability was undamaged after implantation.