Concurrent presentation of palatal myoclonus and sleep apnea: A polysomnographic assessment

1. Introduction 

This case discusses the possible relationship of palatal myoclonus (PM) demonstrated in a patient who presented to our sleep clinic for evaluation of sleep-disordered breathing.

2. Case presentation 

A 69-year-old woman with a 10-year history of idiopathic PM was referred to our sleep center for evaluation of difficulty maintaining sleep. At her initial sleep consultation, she reported snoring and daytime hypersomnia, often experiencing difficulty breathing and loud snoring during sleep.

She initially presented to her neurologist with a history of auditory ear clicks and involuntary movements in her neck and throat. Her current medications included fexofenadine, amlodipine and atenolol, and her physical exam was significant for bilateral rhythmic movements of the mentalis muscles and prominent rhythmic palatal movements (approximately 90/min). The rest of her examination was normal, including normal phonation and tongue movements. A brain MRI did not show evidence of stroke, masses or hypertrophy of the inferior olives. She was subsequently diagnosed with idiopathic PM. She was tried on clonazepam, lioresal, divalproex sodium and lamotrigine without substantial improvement.

A polysomnogram was recommended based on her history of snoring, hypersomnolence, and post-menopausal status which revealed a sleep latency of 67min with decreased slow wave and REM sleep and decreased sleep efficiency (59%). The apnea–hypopnea index (AHI) was 17events/h, with a REM AHI of 49events/h. Almost all of the respiratory events were obstructive. The average non-supine oxygen saturation was 96.5% and 96.4% in the supine position. The minimum SpO2 was 88% and was 97.1% during NREM sleep and 96.8% during REM sleep. The PM persisted during NREM sleep but was more variable in frequency and amplitude during REM sleep. During arousals in REM sleep (usually related to respiratory events), the PM amplitude and frequency increased to ranges demonstrated in the lighter stages of sleep. She opted for CPAP therapy and a recommended pressure of 10cm H2O was initiated. The patient reported difficulty tolerating CPAP and discontinued it. There was no documented improvement of the PM during CPAP treatment.

3. Discussion 

PM is a rare movement disorder defined as brief, rhythmic involuntary movements of the soft palate usually at a frequency of 1.5–3.0Hz [1]. Symptomatic PM typically persists during sleep, but the frequency and amplitude may vary based on sleep stage [2]. It has been proposed that PM may represent a primitive unmasked reflex since PM resembles the rhythmic gill movements of fish. This explanation is not only interesting, but may provide some insight as to why PM persists during sleep [3].

Our patient demonstrated PM during wakefulness and all stages of sleep with a reduced frequency and amplitude during REM sleep. PM amplitude and frequency during arousals from REM sleep were similar to those observed during lighter stages of sleep. PM amplitude has previously been described to be at the lowest during slow wave sleep.

In 2005, Ross and Jankovic [1] reported a case of palatal myoclonus illustrating occasional overlap in clinical features between two types, essential (EPM) and symptomatic palatal myoclonus (SPM), as described by Deuschl et al. [4]. SPM is thought to result from a lesion within the dentatorubral–olivary pathway, while the anatomical lesion for EPM is unknown. Unlike SPM which persists during sleep, EPM disappears during sleep like most other movement disorders [5]. The clinical presentation of our patient is most suggestive of a case of idiopathic SPM or an overlap of SPM and EPM suggesting a clinical hybrid. A hybrid has been previously described in a patient with a PM preceded by an upper respiratory infection. Our patient demonstrated concurrent PM and sleep-disordered breathing which has been reported in a patient with neuro-Behçet syndrome in whom the myoclonus was speculated to have played a role in the presence of apnea [6]. There are no reports of an association between SDB and idiopathic PM as demonstrated by our patient. Generally, the collapse of the soft palate is probably only partially responsible for sleep apnea which is further supported by a success rate of only 40% with a uvulopalatopharyngoplasty [7]. Further analysis of our patient’s breathing pattern revealed that when the palate contracts (Fig. 1) there is a change in the flow as noted in the nasal pressure signal. The effect, however, is brief and does not disrupt the overall breathing frequency or oxygen saturation during sleep. The figure also shows that when the PM contractions occur within a snoring episode, the snoring event appears to be curtailed, as described in reports when the tensor veli palatini muscle was stimulated during sleep [8]. Nevertheless, it is clear that the contractions of the palate are not enough to prevent an obstructive apnea from occurring (Fig. 2), highlighting that obstructive sleep apnea often involves collapse of other upper airway structures such as base of tongue. Therefore, even though one may speculate that PM could play a role in the presence or severity of SDB, as it behaves similarly to regulated, automatic controlled movements during sleep such as respiration, one could also argue that the presence of PM may be unrelated and coincidental when found present in the same individual. Thus, further investigations screening for SDB in patients with PM may not only demonstrate an interesting association, but may also provide additional clues regarding the underlying etiology for patients classified with PM or the uniquely described hybrid SPM/EPM variant demonstrated in this case.

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Fig. 1. This is approximately five seconds of the patient’s polysomnography featuring the breathing channels. The patient is in REM sleep and oxygen saturation (not shown) is 93%. The inflections on the chin EMG show the palatal myoclonus; this shows how the patient is snoring on the nasal pressure signal (high frequency inflections) and that when there is a myoclonus burst, the snore is abbreviated. Chin EMG, genioglossus electromyography; nasal pressure, airflow as measured by nasal cannula pressure transducer; thermistor, airflow as measured by nasal–oral thermistor; chest effort; respiratory effort in chest as measured by respiratory inductive plethsmography; Abd effort, respiratory effort in abdomen as measured by respiratory inductive plethsmography.

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Fig. 2. This is a 30s epoch of the patient’s polysomnography. The patient is in REM sleep and the arrows show that despite the continued presence of the palatal myoclonus, an obstructive apnea persists until an arousal. Chin EMG, genioglossus electromyography; nasal pressure, airflow as measured by nasal cannula pressure transducer; thermistor; airflow as measured by nasal–oral thermistor; chest effort; respiratory effort in chest as measured by respiratory inductive plethsmography; Abd effort, respiratory effort in abdomen as measured by respiratory inductive plethsmography; oximeter; oxygen saturation as measured by pulse oximetry.