A middle-aged man in good health presented with mild sensorineural hearing loss in both ears and hears a loud popping noise in his right ear. The otoscopic and photographic studies showed a normal right eardrum. Hearing test data were carefully inspected for a unilateral difference between ears because only his right ear was affected; no difference was observed.
An audiologist evaluated this patient for the loud snapping and popping noise in his right ear and to document his complaint, if possible. (Figure 1.) The deflections on the tympanometric tracing are not artifact; they correlate with the popping noise in the right ear.
The patient suffers from objective tinnitus. I was able to hear the popping noise in his ear with a Toynbee tube and a standard listening scope for hearing aids. (Figures 3A and B.) The popping and snapping sound was heard easily in the patient's ear through the scope, and he signaled each time he heard the noise. It was obvious that the sound he heard and the sound I heard was the same, a noise that occurred several times each minute at irregular intervals. It was not constant or rhythmic.
Diagnosis: Objective Tinnitus
The patient has a dysfunctional middle ear muscle in the neural pathway on the right. It is most likely the tensor tympani pathway, but we cannot rule out the stapedial pathway at this point. The middle ear has several structures, including the eardrum, the ossicles, and two muscle groups. The stapedius muscle is attached to the stapes and innervated by the seventh cranial facial nerve. The tensor tympani muscle is attached to the long process of the malleus and supplied by the fifth cranial nerve (trigeminal). The stapedius muscle is responsible for the acoustic reflex, and loud sounds cause it to contract. Tensor tympani reflexes can be provoked by touching the face near the eye. Pathological situations have been reported in both pathways.
When the stapedius or tensor tympani muscle contracts, the attached middle ear ossicle is pulled toward the respective muscle. The eardrum is tightened and the compliance (impedance vs. imminence) changes. This dynamic event can be recorded and studied using middle ear tympanomentry (imminence) equipment.
The acoustic reflex pathway is well known. A loud sound enters the ears and travels up the eighth cranial nerve (the auditory nerve) to the brain where the signal crosses to the descending facial cranial nerve, innervating the stapedius muscle. Contractions of the stapedius muscle tighten the eardrum, and the movement of the eardrum is observed by the tympanometer probe signal, which monitors the ear. Acoustic reflex tests are routinely done in middle ear evaluations.
Nonacoustic signals can also elicit middle ear muscle reflexes. The tensor tympani muscle may contract with palatal myoclonus (muscle spasms in the palate); these can be observed in the mouth with the soft palate's periodic movement that coordinates with a clicking noise in the ear. These two muscles are distributed by the fifth cranial nerve (trigeminal). A more central disruption in the fifth cranial nerve may affect the tensor tympani and palatal fibers.
Some patients can voluntarily contract the muscles in their middle ears. I know a person who can do this and generate a popping or snapping noise that is similar to the one this patient is experiencing. Unfortunately, the patient could not control the noise he heard.
Muscle tremors, spasms, and irregular contractions are commonly observed in various parts of the body. Patients with these problems are usually referred to neurologists because a disruption in the neurological network can result in irregular muscle tone and spasmodic muscle movement such as twitching. Comprehensive workups usually include an MRI with contrast and general neurological studies.
I referred the patient to a neurotologist and a neurologist for additional testing. The various underlying diseases that can create a spasmodic muscle need to be ruled out, including palatal myoclonus, multiple sclerosis, Alzheimer's disease, stroke, hypoxia, and amyotrophic lateral sclerosis.
© 2012 Lippincott Williams & Wilkins, Inc.
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