Literature Review: A Roundup of Important Recent Studies

Bottom line: For these young children, bilateral cochlear implantation seemed to generate a significant benefit in spatial acuity tasks, compared with unilateral cochlear implant usage. Sound localization skill began to approach the level of the study participants with normal hearing. Longer usage with bilateral cochlear implants was associated with better performance.

Reference: Grieco-Calub TM, Litovsky RY. Spatial acuity in 2-to-3-year-old children with normal acoustic hearing, unilateral cochlear implants, and bilateral cochlear implants. Ear Hear. 2012;33(5):561-572.

—Reviewed by George Hashisaki, MD

SSCD Treated with Surgical Plugging

Does surgical plugging of a dehiscent superior semicircular canal affect hearing outcome?

Background: A low frequency conductive hearing loss has been associated with superior semicircular canal dehiscence (SSCD). A theoretical explanation is the presence of a mobile “third window” at the dehiscent area that allows sound pressure energy to be shunted away from the cochlea. This effect would impact air conduction thresholds but not bone conduction thresholds, thus creating an apparent conductive hearing loss.

Study design: Retrospective review of 43 cases of SSCD treated with surgical plugging of the affected superior semicircular canal. Pre-operative and post-operative audiograms were compared.

Setting: Tertiary academic medical center: Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore.

Synopsis: The study included 40 patients who underwent a total of 43 repairs of SSCD using a technique of surgical plugging of the superior semicircular canal through a middle cranial fossa approach. All patients had pre-operative and short-term (seven-to-10 day) post-operative audiograms. Thirty-two of the affected 43 ears also had audiograms at more than one month post-operatively (range, one to 15 months; median, three months).

The short-term audiograms showed a slight worsening of bone conduction thresholds across frequencies and persistence of a mild air-bone gap across frequencies. A majority of patients were noted to have fluid or blood in the middle ear.

For the ears with audiograms at longer than one month after surgery, the bone conduction thresholds improved slightly, but a decrease persisted in thresholds at 2000 and 4000 Hz. Air conduction thresholds improved, compared with the short-term audiograms, across frequencies, nearly matching the bone conduction thresholds. In comparison to pre-operative audiograms, there was improvement in the low frequency conductive hearing loss, but there was evidence of a new sensorineural hearing loss at 4000 and 8000 Hz.

Bottom line: The low frequency conductive hearing loss seen in some patients with SSCD is corrected by surgical plugging of the dehiscence. In addition, the procedure was associated with a new mild sensorineural hearing loss in 25 percent of the study participants.