Middle ear myoclonus
Using Botox to treat middle ear myoclonus (MEM) syndrome (a form of tinnitus) is an attractive option. Tinnitus is a symptom and described as the perception of sound without an appropriate external source. Myoclonus is the rhythmic contraction of a muscle and in the case of MEM syndrome of either, or in rare cases both, of the middle ear muscles. The “clicking” or “buzzing sound” can be severely distressing to patients. It may lead to anxiety and depression.
How does Botox work?
Botox protein, also called Botulinum toxin blocks a chemical namely acetylcholine in the nerve- muscle junction. The result is that the nerve impulse cannot elicit a muscle response. Used in many areas of medicine where muscle contraction is unwanted or where muscle response is uncontrolled or spastic it is now a well-established world-wide treatment. Unfortunately, the effect of Botox is usually transient, being effective for only 3-4 months. In a case study by Liu and co-worker’s botulinum toxin type A was administered through a tympanic membrane perforation, into the middle ear to treat MEM syndrome. The patient responded well and was symptom free for 4 months.
Middle ear muscles
The middle ear contains two muscles namely the stapedius muscle and the tensor tympani muscle. They attach to different ear bones (ossicles) and are innervated by separate cranial nerves. The function of the stapedius muscle is to stiffen the ossicular chain at the level of the stapes and is likely to attenuate external sound in order to protect the cochlea. The tensor tympani muscle attaches to the malleus a by contracting stiffens the ossicular chain at the level of the malleus and tympanic membrane. This action leads to the attenuation of internal body sound generated when swallowing, chewing and talking. Another function of these muscles is to produce movements at the ossicular joints for the joints to stay healthy and work effectively in protecting the tympanic membrane against ambient pressure changes.
The presentation of MEM syndrome.
Patients present with the history of a “clicking” or “buzzing” sound in the ear. The sound may also be described as bubbling, thumping, whooshing, gushing, ticking, crackling, throbbing or tapping. In rare cases the noise may be heard by another person. This is then referred to as objective tinnitus. It is difficult to distinguish between myoclonus of the stapedius muscle and myoclonus of the tensor tympani (tensor tympani or TT syndrome) based on the reported characteristics of the sound. Although a “clicking” sound is generally associated with TT syndrome and a “buzzing” sound with
stapedius muscle myoclonus a definite diagnosis can only be made with direct visualisation of the muscle spasm.
The examination is usually normal but, in some cases, a rhythmic movement of the tympanic membrane may be seen, sometimes initiated by eye blinking. Audiometry is not used for diagnosis but in some cases long-term audiometry may show a characteristic appearance. Conditions that may mimic MEM syndrome include palatal myoclonus and patulous eustachian tube. In palatal myoclonus the contraction of the soft palate can be visualised and in a patulous eustachian tube patients can hear their own voice (autophonia) and rhythmic movement of the tympanic membrane in tandem with breathing can be visualised.
What causes MEM syndrome.
In most cases the cause is unknown. Anxiety plays a major role and is believed to lower the threshold for the occurrence of the muscle contractions. Other conditions that may be responsible for objective tinnitus and need to be excluded include abnormal blood vessels, atherosclerosis, vascular tumours such as paraganglioma and multiple sclerosis.
How can MEM syndrome be managed?
Using Botox to treat middle ear myoclonus (MEM) syndrome is an attractive management option. After exclusion of other conditions treatment for MEM syndrome usually includes the use of oral medication such as anticonvulsants or surgery. Medication aim to reduce the myoclonus and some drugs like benzodiazepines have an additional anti- anxiety effect. Anti epileptic drugs such as carbamazepine may cause a lot of unwanted side effects. Surgical treatment comprises of tympanotomy and surgical section of the muscle tendons (tenotomy). This is non-reversible and therefore the diagnosis must be clear, medication not affective and the responsible middle ear muscle identified with certainty. Tenotomy may also lead to sound hypersensitivity. This may be devastating affecting both personal and professional life of a patient.
I am therefore of the opinion that Botox should be considered in the treatment of MEM syndrome before surgical intervention in the form of tenotomy is performed.
Injecting Botox into the Tensor Tympani Muscle. M. Maleus. I. Incus
Applying Botox to the middle ear.
To treat MEM syndrome Botox can be applied to the middle ear in different ways. It is however important to realise that that Botox works on striated muscle and in the middle ear the tendons of both muscles are the visible and most exposed parts, not the muscle. I therefore propose rather injecting the Botox into the muscle by means of a bent fine spinal tap needle to get the maximal response. This can be accomplished using endoscopes or direct visualisation during a tympanotomy.