Although accidental dural puncture and postdural puncture headache (PDPH) are on the radar of most anesthesiologists administering epidural analgesia, subsequent hearing loss is often overlooked. Yet, hearing impairment is a common occurrence following PDPH, but one that can be improved by applying an epidural blood patch.
“Hearing loss after spinal anesthesia has a reported incidence between 0.4% and 40%,” noted Caroline Borkett-Jones, MD, a consultant anesthesiologist at Lister Hospital, East and North Hertfordshire NHS Trust, in Stevenage, England. “The loss relates to the extent of CSF [cerebrospinal fluid] leak and the type and size of needle used. However, when considering the association between hearing loss and postdural puncture, it’s less well described.”
To gain insight into this relationship, Dr. Borkett-Jones and her colleagues enrolled 110 patients into a prospective, observational trial. Each had symptoms of severe PDPH after accidental dural puncture with a 16G Touhy needle.
All patients were evaluated by an audiologist and tested on the same audiometric equipment; audiometry was performed in the sitting position one hour before and 24 hours after epidural blood patch. Hearing was tested between 250 and 8,000 Hz, and the hearing threshold was considered to have changed if the difference between the two tests was at least 10 dB in the same direction at two or more frequencies.
As Dr. Borkett-Jones reported at the 2015 annual meeting of the Canadian Anesthesiologists’ Society (abstract 86119), 34 patients spontaneously complained of hearing loss. With questioning of all 110 patients, however, 91 felt that their hearing was impaired after the dural puncture.
“Nevertheless, there was significant improvement [P<0.0001] in their hearing after the blood patch, specifically in the lower frequencies below 1,000 Hz,” she said. Indeed, 86 patients had an improvement of at least 10 dB at two points in the low frequency range after application of the patch. Furthermore, all patients who had complained of hearing loss felt that their hearing returned to normal levels after the epidural blood patch.
“It could take as long as a week for the hearing to resolve, but most of them resolve within three days,” said co-investigator Dr. Shanmugusundaram Gowrie-Mohan, a consultant anesthesiologist at the institution.
Despite the effectiveness of the epidural blood patch in resolving hearing impairment, Dr. Gowrie-Mohan explained that clinicians did not use the therapy immediately. “We had two patients who experienced hearing loss without the postdural puncture headache, but we waited a couple of days before we treated them, so we could discuss it with colleagues,” he said. “We also don’t do blood patch within 24 hours because the success rate is a bit higher if you wait, and also, very often we don’t diagnose it within 24 hours, anyway. But both of them wanted the blood patch just because they were so distressed, so we gave it to them and it worked.”
Mechanism of Hearing Loss
Exactly why this phenomenon occurs is unknown, although the investigators thought it was likely due to the transmission of reduced CSF pressure to the inner ear by the cochlear aqueduct. “The cochlear aqueduct is an anatomical connection between the subarachnoid space and the inner ear, which is present in most individuals,” Dr. Borkett-Jones explained. “Alteration of this pressure distorts the basilar and vestibular membranes and the function of the auditory hair cells, thus leading to a decrease in hearing.”
These results suggested that hearing loss after accidental dural puncture may be more common than appreciated. “Audiometric testing may play a role in the diagnosis and management of this problem in the future,” she concluded.
For some members of the audience, the frequency of hearing impairment after accidental dural puncture brought on other concerns. “Given these results, I’m wondering if we should then be adding this to the consent for labor epidurals,” commented Naveen Eipe, MD, a staff anesthesiologist at the University of Ottawa, in Ontario, Canada. “We should likely be telling our patients that they might not just suffer accidental dural puncture, but they might suffer hearing loss as well. This study not only highlights a rather unknown anesthetic complication, it suggests a simple and effective remedy.”