A 51-year-old woman presented with a 5-year history of tinnitus and a loud clicking sound in her left ear.
Initial Presentation: A 51-year-old woman with a 5-year history of tinnitus and a loud clicking sound in her left ear.
Description: The clicking was persistent and distressing, but disappeared when she ate and spoke, and she could suppress it at will for a short time. Otorhinolaryngological studies and tympanometry showed no abnormalities, and examination showed a semi-rhythmic movement of the soft palate.
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A 51-year-old woman presented to our department with a 5-year history of a loud clicking sound in her left ear. The patient said that the clicking was persistent and distressing; it disappeared during eating and talking, and she could suppress it at will for a few minutes.
On examination, we found no abnormalities of the cranial nerves; eye examination was normal with no exophthalmos or conjunctival congestion. She had no involuntary movements of her mouth, face, jaw, or tongue. Fundoscopy was normal.
Laboratory investigations found no abnormalities. Otorhinolaryngological studies and tympanometry also showed no abnormalities. However, we did find a constant, semirhythmic movement of the patient’s soft palate—which had not been noticed previously—that disappeared when the patient was distracted by asking her to clap her hands
What is the most likely diagnosis?
- Cavernous arteriovenous fistula
- Middle ear myoclonus
- Oral dyskinesia
- Palatal tremor
Answer: Palatal tremor
Breakdown: MRI showed no abnormalities, and we made a diagnosis of isolated palatal myoclonus—also known as essential palatal tremor or myoclonus. We treated her with 3 mg of clonazepam orally once a day and her symptoms partially improved over the next 2 months.
Palatal myoclonus is an uncommon clinical finding characterised by a rhythmic contraction of the palatal muscles—including the levator veli palatini and the tensor palatini muscles. The contractions lead to the rapid opening and shutting of the Eustachian tube, which produces a clicking tinnitus that is usually audible to the examiner. Secondary or symptomatic palatal tremor is caused by lesions involving the connections between the ipsilateral red nucleus in the midbrain, the inferior olive in the medulla, and the contralateral dentate nucleus in the cerebellum—the three nuclei together being referred to as the Guillain–Mollaret triangle forming the dentato-rubro-olivary pathway (figure). In approximately 70% of cases the lesion is a vascular infarct; other causes include glial fibrillary acidic protein or mitochondrial DNA polymerase γ mutations, neuroferritinopathy, or progressive ataxia and palatal tremor.
Patients with no apparent structural lesions are considered to have isolated palatal tremor. Notably, the tensor veli palatini—innervated by the trigeminal nerve—is mostly involved in cases of isolated palatal tremor, whereas in symptomatic or secondary palatal tremor it is the levator veli palatini muscle—innervated mainly by the vagus nerve—that is affected.
Some cases of isolated palatal tremor may be considered as functional neurological disorders. Some patients report being able to suppress the clicking sound either at will or while being distracted, suggesting a functional origin.
Palatal tremor should be distinguished from middle ear myoclonus—another form of objective tinnitus. In middle ear myoclonus, the sound of the tinnitus is reported to be a buzzing rather than a clicking, and movement of the tympanic membrane rather than the palate is seen on otoscopy.
Treatment options are limited, but phenytoin, carbamazepine, clonazepam, sumatriptan, and botulinum toxin have been found to be useful in some patients.
Source: All content for this “Diagnostic Puzzle” was sourced from The Lancet. The article was written by Kiyoshi Shikino, PhD, Rurika Sato, MD, Nao Hanazawa, MD and Masatomi Ikusaka, PhD.
Original article is available at:
https://www.thelancet.com/article/S0140-6736(21)01247-2/fulltext
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