Hearing loss can be classified as conductive or sensorineural, although both may
occur after certain types of head injuries. Conductive hearing loss can be due to
mechanical disruption of the ossicles, impedance with noise conduction to the eardrum, or
a blockage in the middle ear or external auditory canal (e.g. blood clot). Sudden
neurosensory hearing loss (NSHL) is defined as loss of hearing due to pathology within or
medial to the cochlea (disorders involving the acoustic nerve or hair cell function).
Diagnosis and Treatment Options
If a patient presents with a chief complaint of loss of hearing, first verify the
presence of a real hearing loss. Use the 512 Hz tuning fork to perform a Weber and Rinne
test. Beware of inconsistent responses and have a high index of suspicion for malingerers.
If the 512 Hz tuning fork test is consistent with a conductive hearing loss, check for
effusions, retraction, chronic ear disease, and perforation. Also perform valsalva
testing. The cause of a conductive hearing loss is usually evident by history or exam and
it is rarely of sudden onset unless it occurs with barometric pressure changes.
On the other hand, if the tuning fork test is consistent with sensorineural hearing
loss, then confirmatory audiometric testing is mandatory. Any sudden onset of
sensorineural loss should be referred within 24 hours for evaluation by an
otolaryngologist because rapid intervention (medical or surgical) is associated with
higher rates of recovery. Sudden sensorineural hearing loss secondary to perilymphatic
fistulas is surgically treatable.
All other forms of inner ear injury causing sudden sensory loss, with the exception of
decompression illness, are treated with oral steroids, bed rest, and fluids. There are
many protocols using inhaled gases and vasodilators, but the clinical efficacy is
statistically no greater than with steroid therapy alone. Prompt treatment is more
important than which treatment, as most studies show that the prognosis for saving
hearing deteriorates beyond the 7th day following onset of symptoms.
Remember that 10 percent of patients with acoustic neuromas present with sudden
sensorineural hearing loss. Imaging with MRI or CT scan should be performed to rule out
the likelihood of a mass lesion.
Barometric Pressure Changes
Special consideration must be given to patients with sudden sensorineural hearing
loss following barometric pressure changes like diving or aerospace accidents. The
probability of perilymph rupture is greater in these patients and rapid diagnosis and
institution of bedrest with fluids will improve chances of spontaneous closure. If bedrest
does not relieve symptoms surgical intervention is warranted. Decompression illness can
also cause cochlear gas emboli with hearing loss. Perform a careful neurologic exam and
always consult with a diving medical officer (DMO) or otolaryngologist.
Sudden sensorineural hearing loss is often misdiagnosed due to the
failure of evaluating the patient with tuning forks. Perform a methodical exam of the ears
and related structures. If hearing can be saved, intervention must be initiated early
following symptom onset. Consultation with an otolaryngologist is very important as well
as MRI and CT imaging to rule out mass lesions.
DeWeese and Saunders, Textbook of Otolaryngology
Reviewed by CAPT David H. Thompson, MC, USN, Department of Otolaryngology,
National Naval Medical Center, Bethesda, MD.(1998).