Sleep-related head jerks: toward a new movement disorder

Clinical features and mechanisms of neck myoclonus in narcolepsy

STUDY OBJECTIVES

The purpose of this study was to investigate the effects of neck myoclonus (NM) on sleep quality and daytime sleepiness in patients with narcolepsy (NT) and to further explore possible underlying mechanisms.

METHODS

We included 72 patients with narcolepsy type 1 (NT1), 34 patients with narcolepsy type 2 (NT2) and 33 healthy controls. Patients underwent questionnaires, lumbar puncture procedure, polysomnography, and multiple sleep latency test (MSLT). Healthy controls underwent polysomnography and questionnaires. Orexin-A levels in the cerebrospinal fluid (CSF) were analyzed by radioimmunoassay. Three catecholamines, including dopamine, norepinephrine and epinephrine, in the CSF were measured by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS).

RESULTS

Both the NT1 and NT2 groups displayed a higher level of NM incidence rate and index compared to the control group in PSG. NT1 displayed greater MSLT REM--NM incidence rate and index than NT2. NM were often associated with arousal or awakening and body movements, which had a prominent influence on sleep quality in both narcoleptic patients and controls. There was a positive correlation between the NM index and the Pittsburgh Sleep Quality Index (PSQI), Stanford Sleepiness Scale (SSS) and Ullanlinna Narcolepsy Scale (UNS) scores in NT1 patients. In MSLT of NT1 patients, REM-NM index were positively correlated with the CSF dopamine levels, and there were elevated dopamine levels but reduced orexin-A levels in patients with REM-NM.

CONCLUSION

NM incidence rate and index were high in patients with narcolepsy, which had a huge effect on sleep quality and aggravated daytime sleepiness. NM should be considered pathological and viewed as a new sleep-related movement disorder. Orexin-A and dopamine may be involved in the development of NM.

Three cases of parasomnias similar to sleep terrors occurring during sleep-wake transitions from REM sleep

Sleep terrors are a non-rapid eye movement (NREM) sleep-related parasomnia characterized by abrupt terror with a frightening scream. However, it remains unknown whether sleep terrors occur only from NREM sleep. We evaluated 3 cases of a sleep terrors-like parasomnia that occurred exclusively during arousals from rapid eye movement (REM) sleep. These parasomnia events occurred at REM sleep-wake transitions, manifesting with screaming or crying, similar to sleep terrors, without alertness or clear orientation. The patients were all young-adult females without notable medical conditions. REM sleep behavior disorder and nocturnal frontal lobe epilepsy were not detected based on their video-polysomnographic findings. These 3 cases should be provisionally diagnosed as "Parasomnia, Unspecified" according to the International Classification of Sleep Disorders, third edition; however, the phenomenological diagnosis is proposed to be "Disorders of Arousal from REM Sleep." Our reported cases indicate that sleep terrors may also arise from REM sleep.

CITATION

Futenma K, Inoue Y, Saso A, Takaesu Y, Yamashiro Y, Matsuura M. Three cases of parasomnias similar to sleep terrors occurring during sleep-wake transitions from REM sleep. J Clin Sleep Med. 2022;18(2):669-675.

REM sleep behavior disorder: Mimics and variants

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia with dream-enactment behaviors occurring during REM sleep and associated with the lack of the physiological REM sleep muscle atonia. It can be isolated and secondary to other neurological or medical conditions. Isolated RBD heralds in most cases a neurodegenerative condition due to an underlying synucleinopathy and consequently its recognition is crucial for prognostic implications. REM sleep without atonia on polysomnography is a mandatory diagnostic criterion. Different conditions may mimic RBD, the most frequent being obstructive sleep apnea during sleep, non-REM parasomnia, and sleep-related hypermotor epilepsy. These diseases might also be comorbid with RBD, challenging the evaluation of disease severity, the treatment choices and the response to treatment evaluation. Video-PSG is the gold standard for a correct diagnosis and will distinguish between different or comorbid sleep disorders. Careful history taking together with actigraphy may give important clues for the differential diagnosis. The extreme boundaries of RBD might also be seen in more severe and complex conditions like status dissociatus or in the sleep disorders' scenario of anti IgLON5 disease, but in the latter both clinical and neurophysiological features will differ. A step-by-step approach is suggested to guide the differential diagnosis.

Electroclinical Features of Sleep-Related Head Jerk

STUDY OBJECTIVES

To evaluate clinical and electrophysiological features of sleep-related head jerk (SRHJ) and electromyographic activity of superficial neck muscles during head jerk.

METHODS

Totally, 850 cases with video-polysomnography recording were collected, among which 50 presented with SRHJ. In these 50 patients, 15 underwent electromyography (EMG) check on bilateral sternocleidomastoid (SCM) and trapezius muscles as well as chin, while 35 had only chin EMG check. Further, the sensitivity and specificity of the both EMGs were calculated and compared.

RESULTS

Six among the 50 SRHJ patients had a primary complaint of involuntary head jerks associated with impaired sleep. Approximately 76.1% of head jerks occurred during REM sleep with the median head jerk index of 5.9/h, 64.5% of which were associated with electroencephalogram arousals and 66.4% with body movements. One patient showed SRHJ predominantly in NREM sleep but also in wakefulness. Surface EMG of SCM/trapezius muscles showed a sensitivity of 92% and a specificity of 97.8%, whereas chin EMG had a sensitivity of 14.5% and a specificity of 98.8%.

CONCLUSION

SRHJ was associated with electroencephalogram arousals and might interfere with sleep. Surface EMG of SCM/trapezius muscles exhibited a good accuracy in the revelation of SRHJ.