A new possible mechanism of hearing loss after microvascular decompression for hemifacial spasm

Objective: Hearing loss is a well-known complication that may occur during microvascular decompression (MVD) for hemifacial spasm (HFS). Cause and risk factors are highly variable. We present cases of hearing loss induced by saline overinfusion after MVD. Study Design: Retrospective review in a tertiary referral center. Intervention: Three hundred thirty-one patients with HFS underwent MVD from March 2009 to October 2010. Main Outcome Measures: Brain stem auditory evoked potential (BAEP) was monitored during the surgery. Before completion of the dural closure, the surgical field was routinely filled with warm saline to avoid postoperative pneumocephalus and epidural hematoma. Results: Seven patients experienced a change in wave V amplitude and latency after the dural closure. In 2 patients, the amplitudes decreased by less than 50%, and latencies were delayed by less than 1.0 ms, ipsilaterally in 1 patient and contralaterally in the other. In 1 patient, decreased amplitude and delayed latency appeared bilaterally with more severity on the operated side, accompanied by delayed ipsilateral permanent hearing loss. In 4 of the 7 patients, an ipsilateral response of BAEP was completely absent. Of these 4 patients, 2 experienced permanent hearing loss, and another 2 patients who underwent dural reopening and saline drainage had restoration of their normal hearing. Conclusion: Intradural compression due to overinfusion of saline may lead to postoperative hearing loss, although the incidence is low, and immediate decompression by drainage may be required.