Hearing impairment associated with spinal anesthesia.

Objectives: Hearing loss after spinal anesthesia has been reported to be related to the transmission of a reduced subarachnoid pressure to the inner ear via the cochlear aqueduct due to loss of spinal fluid. However, there are also some controversies related to this phenomenon, which require systematic investigation.

Material And Methods: The effect of spinal needle diameter on hearing loss was investigated using audiometric tests in a prospective comparative study of 30 patients who were scheduled for surgery with spinal anesthesia. The bony structure of the cochlear and vestibular aqueducts was determined from temporal bone CT scans.

Results: Four out of 15 patients (26.67%) treated with a 22 G spinal needle demonstrated hearing loss the day after surgery, which recovered within 2-5 weeks. However, none of the patients treated with a 27 G spinal needle had statistically significant hearing loss in either ear at any frequency. Three out of four patients with hearing loss had an acute-onset balance problem. There was no difference between the two groups in terms of the widths of the vestibular and cochlear aqueducts.

Conclusions: It has been shown audiometrically that the diameter of the spinal needle used to induce spinal anesthesia seems to have an effect on subsequent hearing loss. The patency of the bony canal determines the transmission of pressure changes to the inner ear. However, the individual risk of this complication is not predictable as there is no radiological abnormality of the canal.