Low-frequency hearing loss after spinal anesthesia. Perilymphatic hypotonia?

Audiological tests were conducted on 34 patients before and after undergoing an operation under spinal anesthesia. One of these patients developed a considerable unilateral hearing loss in the low-frequency range, which persisted until an epidural blood-patch was given. Unexpectedly, we also found a general small significant threshold shift at 500 Hz, which has never before been described in the literature. The biological mechanism is discussed and the results suggest that the explanation of the hearing loss could be an endolymphatic hydrops resulting from perilymphatic hypotonia due to loss of liquor, during and after the spinal anesthesia.