Surdités brusques : intérêt de l’imagerie

Magnetic resonance imaging in a guinea pig model of inner ear decompression sickness and barotrauma

OBJECTIVES/HYPOTHESIS

Scuba diving may cause severe hearing loss and vertigo due to inner ear barotrauma and decompression sickness. These may be difficult to differentiate clinically. Decompression sickness requires costly and potentially dangerous hyperbaric therapy, whereas such treatment may worsen barotrauma. The objective of this study was to assess the potential utility of magnetic resonance imaging to identify and distinguish blood from air in the inner ear, manifestations of barotrauma and decompression sickness, using a guinea pig model.

STUDY DESIGN

Prospective animal trial.

METHODS

Magnetic resonance of the head was performed at 3 Tesla, pre- and postinjection of 2, 4, or 10 μL of air or blood through the round window into the perilymph. With this model, 2 μL has been shown to cause hearing loss. Images were reviewed by a neuroradiologist blinded to the treatment.

RESULTS

All 14 normal ears, five of seven blood- and five of seven air-injected ears, were correctly interpreted. Two blood- and one air-injected ear were interpreted as indeterminate. One air-injected ear was incorrectly interpreted as blood.

CONCLUSIONS

Magnetic resonance reliably distinguishes small volumes of air and blood in the guinea pig inner ear. Magnetic resonance should be evaluated for its utility in the diagnosis of inner ear barotrauma and decompression sickness in scuba divers.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:2106-2109, 2016.

[Sudden onset hearing loss: imaging work-up]

Sudden onset hearing loss is idiopathic. It occurs in less than 24 h and spontaneously resolves within 15 days in two thirds of cases. Imaging is performed to exclude other causes of sudden onset hearing loss (vestibular schwannoma, vertebral artery dissection, stroke) and evaluate the inner ear structures. A few anatomical anomalies have been associated with an increased risk of hearing loss. Morphological anomalies involved the following structures in decreasing order of frequency: lateral semicircular canal (hypoplasia and dilatation), superior semicircular canal, posterior semicircular canal, vestibule and cochlea. Enlargement of the vestibular aqueduct also is frequently observed.

[Consensus on diagnosis and treatment of sudden hearing loss. Asociación Madrileña de ORL]

Idiopathic sudden sensorineural hearing loss is an unexplained unilateral hearing loss with onset over a period of less than 72 hours, without other known otological diseases. We present a consensus on the diagnosis, treatment and follow-up of this disease, designed by AMORL, after a systematic review of the literature from 1966 to June 2010. Diagnosis of sudden sensorineural hearing loss is based on mandatory otoscopy, acoumetry, tonal audiometry, speech audiometry, and tympanometry. After clinical diagnosis is settled, and before treatment is started, a full analysis should be done and an MRI should be requested later. Treatment is based on systemic corticosteroids (orally in most cases), helped by intratympanic doses as rescue after treatment failures. Follow-up should be done at day 7, with tonal and speech audiometries, and regularly at 15, 30, and 90 days after start of therapy, and after 12 months. By consensus, results after treatment should be reported as absolute dBs recovered in pure tonal audiometry, as improvement in the recovery rate in unilateral cases, and as improvement in speech audiometry.