|Year : 2015 | Volume
| Issue : 4 | Page : 294-297
Palatal myoclonus: A long follow-up experience
Viresh Arora, Mike Smith
Department of ENT, Wye Valley NHS Trust, Hereford HR1 2ER, UK
|Date of Web Publication||16-Oct-2015|
A3 Longfield House, Wye valley NHS trust, Hereford HR1 2ER
Source of Support: None, Conflict of Interest: None
Palatal myoclonus is an extremely rare neurotological disorder presenting to an otolaryngologist. It presents as objective tinnitus which is due to rhythmic, involuntary movements of the soft palate causing distress to the patients. Different medical and surgical remedies have been attempted with variable success. Botulinum toxin has been reportedly used in few cases and has reproduced good results lasting for a few months with minimum morbidity. We report a case suffering from palatal myoclonus for about 15 years and injection of botulinum toxin into his tensor veli palatini muscle resolved his objectionable unilateral tinnitus. Optimum results obtained initially, waned off over the years, for which the dose had to be gradually increased to achieve the desired clinical results.
Keywords: Botulinum toxin, Palatal myoclonus, Palatal tremor
|How to cite this article:|
Arora V, Smith M. Palatal myoclonus: A long follow-up experience. Indian J Otol 2015;21:294-7
| Introduction|| |
Palatal myoclonus or also known as palatal tremor a quite an uncommon condition. It is a segmental myoclonus characterized by involuntary brief rapid rhythmic jerky movements of the soft palate and peritubal musculature causing clicking sound in the ear.
It can be subjective which is perceived only by the patients as annoying clicking tinnitus with strong muscle spasms felt at the back of throat or objective if also heard by the examiner. It is an extremely distressing to the patient for which they seek a remedy. The condition usually effects adults and can last indefinitely. It has been reported in children as young as 7 years of age. In the literature about 200 cases of palatal myoclonus have been reported.
Two clinical forms of palatal myoclonus have been identified with distinct etiologies. The symptomatic form is associated with a lesion in the triangle of Guillain. which consists of inferior nuclei, red nuclei, dentate nuclei, and the central tegmental tract. The other form is essential palatal in which tinnitus occurs intermittently secondary to the contractions of tensor veli palitini muscle without the association of intracranial pathology.
Earlier treatment of palatal myoclonus with anxiolytics, anticonvulsants, has rarely been successful to control the tinnitus. In the recent years, the injection of botulinum toxins into the palatal muscles producing encouraging results have been reported by a few researchers.,
Botulinum toxin causes temporary paralysis of the injected muscles up to 8 weeks or more by inhibiting the release of acetylcholine from the presynaptic vesicles and causing subsequent atrophy of the effected muscles. The symptoms recur with the return of the contracting muscles. Its associated side effects such as velopharyngeal insufficiency and nasal regurgitations though short lived counterbalances the response in ameliorating the distressing condition.
| Case Report|| |
A healthy male aged 40 years presented to us 15 years ago with a complaint of clicking sound in the right ear, which he had noticed some weeks ago. He gave a history of sudden onset, without any preceding factors and the sound had progressively become unbearable in a few weeks time. The patient had sleepless nights because of the annoying sounds. He had no history of ear infections, operations on the ear, and did not have exposure to loud sounds. There was no associated hearing loss or vertigo. He was a nonsmoker and consumed a moderate amount of alcohol. His family history was not suggestive.
His ears were unremarkable and otomicroscopy failed to reveal any visible oscillations of the tympanic membrane. His oral examination showed vibrating soft palate both sides, but he complained of tinnitus only on the right side. The contractions were noticed at 1 beat per se cond, which was asynchronous with his pulse. The sound was audible at about 50 cm distance. The sound was not altered with valsalva maneuver, mouth movements, or changes in head position. Neck examination was negative for any vascular lump, and no bruit was audible with the stethoscope. Rinnies was positive both side with 512 Hz and weber being centralized. His audiogram and tympanogram were normal, and the stapedial reflexes were elicited at 80 dB clicks.
Maxillofacial and neurological examination were normal. Laboratory studies including complete blood count, antinuclear antibody studies, and thyroid tests were within range. Magnetic resonance imaging (MRI) scan of the brain failed to show any pathology, and hence, diagnosis of essential myoclonus was established.
The patient was then suggested lyophilized botulinum toxin A (Allergan) injections into his palate to alleviate his symptoms of tinnitus with a small associated risks of transient velopharyngeal insufficiency, dysphagia, and the need for repeated injections. Initially, 50 units of botulinum toxin were injected in total over the whole of the soft palate at multiple sites under direct vision. The sites included insertions of levator palatini and tensor palatini, medial to the pterygoid humulus [Figure 1]. The patient got immediate relief from the tinnitus within 24 h of injection, but complained of hypernasality and nasal regurgitation, and slurring of his speech, which gradually improved over next few days. He noticed a rash with fever 4 days after the injection which subsided with paracetamol.
|Figure 1: Sites of injection of botulinum toxin- Medial to the pterygoid hamulus (white area)|
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The patient remained symptom free for about 12 weeks when his tinnitus started to return back and which gradually increased over next few weeks, requesting him for the next dose of injection. The patient was advised clonazepam 5 mg prn to alley his anxiety. After 6 months, only 10 units were injected, with 7.5 units on the right side, since his main complaints of tinnitus were on the right side only. The benefit lasted about 6 weeks after which his symptoms started to recur and had to use clonazepam more frequently. After 4 months, he was injected with 15 units and the effect lasted for 8 weeks. The next dose of 20 units was given after 6 months, gave him relief for about 8 weeks only, prompting another dose to be injected before than usual anticipated time. Subsequent doses had gradually to be increased by about 10 units/year based on the patient's feedback of recurrence of symptoms. The patient maintained a dairy of his symptoms and the intervening relief period which dictated further injections in regard to the dosage.
Patient was apprehensive of the frequent injections of the toxin, required every 6 months or earlier, so he was suggested coblation of the soft palate to decrease the bulk and stiffening of the palate in hope to decrease the contractions of the soft palate. The patient failed to get a desirable benefit, rather complained of prolonged postoperative pain. He declined further coblation attempts and insisted for further botulinum injections.
Over the years, the injected doses failed to keep up with remission. For the last few years, the patient received 60 units/session with response lasting for about 10 weeks. In the last 2 years, 75 units of botulinum toxin were injected at 6 monthly intervals [Figure 2]. A repeat MRI scan was done 2 years ago has been negative, ruling out any pathology.
| Discussion|| |
Myoclonus is a brief, rapid, shock-like, jerky movement disorder of a group of muscles secondary to various etiologies. Palatal myoclonus is a regular, rhythmic contraction of the palatal soft palate, which may be accompanied by myoclonus in other muscles including those in the face, tongue, and throat. A clicking sound commonly audible is a noise made by the contacting palatal muscles. Tinnitus can be subjective when heard by the patient himself or objective when heard by the examiner.
The causes of the objective can be vascular in origin such as arteriovenous malformations and venous hums. It can be physiological occurring during the sleep. The contractions are very rapid, occurring up to 150 times a minute. The frequency of the jerking is usually 1–2 Hz. It has been suggested that the contraction of the levator veli palatini muscle may induce pressure variation's into the eustachian tube, which may induce oscillations in the tympanic membrane. It needs to be differentiated from middle ear myoclonus when the muscles of the middle ear tensor tympani and stapedius are involved, which is visualized as oscillating tympanic membrane on otoscopic examination and is confirmed by tympanometry.
Palatal myoclonus can be essential or symptomatic of a neurological lesion in the Guillain. triangle. Deficiencies in the inhibitory neurotransmitters receptors serotonin, gamma aminobutyric acid, and glycine in the brain relate to some forms of myoclonus have been speculated by some researchers. In the symptomatic form, it has been seen that hypertrophic degeneration of the inferior olivary nuclei by ipsilateral brainstem disease or contralateral cerebellar disease could induce symptomatic palatal myoclonus in humans. These patients usually are often unaware of the palatal movements but have symptoms and signs relating to brainstem or cerebellar dysfunction. In the essential variant, an objective click is audible due to the rapid contracting peritubal muscles levator veli palatini and tensor veli causing opening and closure of the eustachain tube.
Myoclonus of the palatal muscles is rare and a well-accepted therapeutic approach for palatal myoclonus does not exist based on small numbers of patients. Medical treatment is usually refractory in patients with symptomatic form palatal myoclonus. In a few sporadic cases, only 20% of patients have been reported partial relief on treatment with barbiturates, phenytoin, carbamazepine, clonazepam and 5-hydroxytryptophan, anticonvulsants and anxiolytics, and sedatives. White noise masking has been able to achieved a partial relief in the symptoms. Other treatment modalities such as deep brain stimulation are under evaluation.
Essential palatal myoclonus affects mostly the tensor veli palatini muscle and has successfully treated with botulinum toxin. Treatment with botulinum toxin type-A injection in the palatal muscles under electromyographic (EMG) guidance has proved its efficacy. Surgically perforation of the tympanic membrane and cutting of the levator palatini muscle, tensor veli palatini and tensor tympani muscle dissection have not added much to the benefit. Sectioning the tensor tympani and stapedius muscle have been partly beneficial only in patients suffering from middle ear myoclonus.
We tried using coblation of the soft palate to stiffen the palate thinking would reduce the contractions of the muscles although much relief was not obtained, and no reference could be gathered in the literature.
One of the researchers injected 10 units under EMG and have reported to achieve satisfying results. In our case, we started with 10 units, the relief in symptoms lasted for a few weeks only dictating gradual increments over a period of time is similar to some authors who have reportedly injected 30 units unilaterally under direct vision. Moreover, in our case relief was short lived up to a maximum of 10 weeks and over a period of time remissions were noticed much earlier. We had a long follow-up with this patient, and such a long follow-up has not been reported earlier, and none of the authors has reported such frequent remissions.
Botulinum injections have also been extensively used for esthetic procedures such as a facial rejuvenation for many years and the successful treatment requiring repeated injections over long periods. We noticed in our case, the effect of the injections waned rapidly, needing dose increments, which can be accounted by the emergence of antibodies to the botulinum toxin, necessitating the dose to be increased to alleviate the symptoms. Cases of secondary treatment failure are being increasingly reported with the development of high titers of antibodies to the toxin prompting dose adjustments.
| Conclusion|| |
Since botulinum toxin is the only palliative treatment available and the emergence of resistance with neutralizing antibodies is a concern, since the injections would be required lifelong. Clinicians should be wary of this and devise newer protocols to minimize emerging resistance. We believe that Injections under EMG guidance would be helpful requiring less dosage, would minimize the resistance development.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]