Idiopathic sudden sensorineural hearing loss (ISSHL) is defined as a hearing loss of at least 30dB occurring within three days over at least three contiguous frequencies. The most common symptoms involves a sudden unilateral hearing loss, tinnitus, a sensation of aural fullness and vertigo.

The cause of ISSHL remains unclear but maybe due to vascular occlusion, viral infections, labyrinthine membrane breaks, immune associated disease, abnormal cochlear stress response, trauma, abnormal tissue growth, toxins, ototoxic drugs and cochlear membrane damage.

The cochlea and the structures within it require a high oxygen supply. Perilymph oxygen tension is decreased significantly in patients with ISSHL. This can be restored with hyperbaric oxygen therapy.

Patients who present within 14 day of symptom onset or as earlier is more likely to have a better outcome.  10 to 20 treatments using Hyperbaric oxygen therapy is required.