Myorhythmia: Phenomenology, etiology, and treatment

Abstract

Myorhythmia is defined as repetitive, rhythmic, slow (1-4 Hz) movement affecting chiefly cranial and limb muscles. When occurring in the limbs it may be oscillatory and jerky, whereas oculo-masticatory myorhythmia, typically associated with Whipple's disease, is a slow, repetitive, often asymmetrical, facial and ocular movement. Thus, myorhythmia overlaps phenomenologically with tremor and segmental myoclonus. Although often present at rest, it must be differentiated from parkinsonian or dystonic tremor. Recognition of this movement disorder is important because it is usually associated with lesions involving the brainstem, thalamus, or other diencephalic structures with potentially treatable etiologies. In addition to Whipple's disease, myorhythmia has been described in patients with cerebrovascular disease, listeria encephalitis, anti-N-methyl-d-aspartate receptor encephalitis, steroid-responsive encephalopathy associated with autoimmune thyroiditis, multiple sclerosis, and other disorders. In addition to our own experience, we have systematically reviewed the medical literature, focusing on the phenomenology, pathophysiology, and etiology of this poorly recognized movement disorder. In this review, we aim to highlight the clinical features that differentiate myorhythmia from other movement disorders. Treatment should be directed against the underlying etiology.

Systematic review of movement disorders and oculomotor abnormalities in Whipple's disease

“…Terminology used in the literature has been somewhat inconsistent and contributes to some confusion about the movement disorders seen in CNS‐WhD. The term myorhythmia was introduced by Hertz in 1931, but its first use in the setting of WhD was by van Bogaert et al in 1963, who reported “oculofaciocervical myorhythmia” in a patient diagnosed 16 years later with CNS‐WhD . Some of the cases we reviewed predated that report.…”

Unusual tremor syndromes: know in order to recognise

“…Myorhythmia has been recently defined as a repetitive, rhythmic, often jerky movement of slow (1–4 Hz) frequency, typically affecting the cranial and limb muscles16 although the term myorhythmia was originally coined by Herz17 in 1931. The movements of myorhythmia predominantly occur at rest and are distinguishable from a parkinsonian tremor by the lack of L-dopa responsiveness, a more irregular and slower frequency, as well as an intermittent nature.…”

“…For instance, some of these tremors were predominantly described in patients with dystonia and would currently be more likely referred to as dystonic tremor 16. The main source of confusion results from the differential diagnosis with Holmes’ tremor or pseudorhythmic myoclonus, as these terms have been used interchangeably.…”

“…While conducting the literature review, available video evidence of cases reported as myorhythmia were also analysed by two authors (AF and AEL). In some cases, the original authors did not classify the movement as myorhythmia but they were included in a recent review on the topic 16. Forty-four video segments were taken into account and inter-rater agreement ranged from 79.5% (variability) to 90.9% (frequency).…”

Therapeutic Developments for Tics and Myoclonus

“…Physiologically, myoclonus has been classified as cortical (e.g., cortical‐reflex myoclonus, epileptic myoclonus, and Alzheimer's disease), cortical‐subcortical (e.g., posthypoxic myoclonus, Huntington's disease [HD], and corticobasal degeneration), segmental (e.g., brainstem and spinal), or peripheral (e.g., hemifacial spasm). Myoclonus may be manifested by generalized, stimulus‐sensitive jerks, observed, for example, in patients with posthypoxic myoclonus, as small amplitude focal jerk‐like movements in epilepsia partialis continua, or slow, rhythmic, jerky movements present typically in brainstem or spinal segmental myoclonus, also referred to as myorhythmia …”