Middle Ear Myoclonus (MEM) is a form of tinnitus, the perception of sound without an external source. This specific type is caused by the sudden, involuntary, and repetitive contractions of the small muscles located within the middle ear. Individuals experiencing this condition report hearing a distinct clicking, thumping, buzzing, or fluttering sound in one or both ears. While MEM is not considered dangerous, the persistent and disruptive nature of the internal sound can significantly impact a person’s quality of life. Understanding the underlying cause is the first step toward finding effective treatment.
The Anatomical Mechanism
The internal sound characteristic of MEM is a direct result of the mechanical disruption caused by two tiny muscles: the Tensor Tympani and the Stapedius muscle. These muscles attach to the chain of small bones, or ossicles, that transmit sound to the inner ear. The Tensor Tympani connects to the malleus, while the Stapedius connects to the stapes. The normal function of these muscles is to act as a protective reflex, stiffening the eardrum and ossicular chain to dampen intense sound vibrations. When MEM occurs, one or both muscles begin to spasm or twitch sporadically, pulling on the attached bones and creating the audible clicks or thumps.
Primary Causes and Associated Conditions
The exact cause of Middle Ear Myoclonus often remains unknown, classifying it as idiopathic. However, the condition can be broadly linked to several categories of issues that disrupt the normal function of the middle ear muscles.
Neurological Causes
Involuntary spasms can result from a disorder affecting the nerves or brainstem that control the muscles. Examples include demyelinating diseases like multiple sclerosis or lesions affecting the brainstem. The Tensor Tympani is innervated by the trigeminal nerve, and the Stapedius by the facial nerve; dysfunction along these pathways can trigger the contractions. MEM is sometimes associated with other movement disorders, such as essential tremor or palatal myoclonus, suggesting a shared neurological origin for the abnormal muscle activity.
Structural and Local Causes
These causes stem from issues within the ear or surrounding anatomical structures. Dysfunction of the Eustachian tube, which equalizes middle ear pressure, can cause muscle tension leading to spasms. Because the Tensor Tympani is closely associated with the muscles that open the Eustachian tube, problems like chronic ear infections or allergies can indirectly trigger the myoclonus. Conditions like temporomandibular joint (TMJ) disorders may also contribute, as the Tensor Tympani and jaw muscles share related innervation and physical connections.
Psychological Factors
Stress and anxiety are known to increase overall muscle tension and nervous system activity. This can lower the threshold for spasms in the middle ear muscles. Anxiety often intensifies the perception of the sound and may trigger or worsen the frequency of the muscle contractions.
Identifying Symptoms and Diagnosis
The defining symptom of Middle Ear Myoclonus is the perception of an internal, non-pulsatile sound that is frequently described as clicking, thumping, or tapping. This sound is often intermittent or rhythmic. In rare cases, the loudness of the contraction is sufficient for the sound to be heard by an examiner, classifying it as objective tinnitus. The spasms can sometimes be triggered by external factors like loud noises, or internal actions such as swallowing or speaking.
Diagnosis begins with a thorough medical history and physical examination, which includes otoscopy to visualize the eardrum. The physician may observe a rhythmic movement of the tympanic membrane that corresponds with the patient’s reported clicking sound. Ruling out other causes of objective tinnitus, particularly vascular issues, is a crucial part of the diagnostic process.
Specialized auditory tests, such as tympanometry and acoustic reflex testing, are essential to confirm the muscular origin. Tympanometry measures the eardrum’s mobility in response to air pressure changes and can reveal irregular contractions of the middle ear muscles. Acoustic reflex testing measures the Stapedius muscle’s response to loud sounds, potentially showing an irregular or absent reflex pattern that indicates abnormal muscle activity.
Treatment and Management Options
The primary goal of managing Middle Ear Myoclonus is to reduce the frequency and severity of the involuntary muscle spasms. Treatment follows a stepwise approach, starting with pharmacological management.
Medications commonly used include muscle relaxants, such as benzodiazepines, and anticonvulsants, which help to suppress the abnormal nerve signals that cause the muscle to twitch.
If oral medications prove ineffective, local injection of botulinum toxin directly into the affected middle ear muscle is an option. The toxin temporarily paralyzes the muscle, providing temporary relief and helping to confirm which muscle is responsible for the symptoms. The effects last for a few months, and the procedure may need repetition.
For severe and persistent cases unresponsive to medication or injections, surgical intervention may be considered as a last resort. The most common procedure is a tenotomy, which involves cutting the tendon of the spastic muscle, either the Tensor Tympani or the Stapedius. This non-reversible procedure permanently stops the muscle from pulling on the middle ear bones.