It was independently described first in 1905 by Zappert as jactatio capitis nocturna and by Cruchet as rhythmie du sommeil.

[2] In order to be considered pathological, the ICSD-II requires that in the sleep-related rhythmic movements should “markedly interfere with normal sleep, cause significant impairment in daytime function, or result in self-inflicted bodily injury that requires medical treatment (or would result in injury if preventive measures were not used)”.

The rhythmic movements may produce some bodily injury via falls or muscle strains, but this is not reported in all patients[4] .

[citation needed] Rhythmic movement disorder is observed using the standard procedure for polysomnography, which includes video recording, EEG during sleep, EMG, and ECG.

RMD patients often show no abnormal activity that is directly the result of the disorder in an MRI scan.

Additionally, there is a close association with Alpha waves that contain a mixture of K complexes and arousals, regardless of the NREM stage in which the RMD occurred.

The occurrence of these two sequences of brain waves suggests that the disorder is linked to an “unstable vigilance level” throughout NREM sleep[9] .

[14] The direct cause and pathophysiological basis of RMD is still unknown and can occur in children and adults of perfect or non-perfect health.

Rare cases of adult RMD have developed due to head trauma, stress, and herpes encephalitis.

[1] Familial cases have been reported suggesting there may be some genetic aspect to the disorder; however, to date, this explanation has not been directly tested.

Another theory suggests that RMD is a learned, self-stimulating behavior to alleviate tension and induce relaxation, similar to tic movements.

[15] An alternative theory suggests that the rhythmic movements help develop the vestibular system in young children, which can partially explain the high prevalence of RMD in infants.

Often, impairments are not severe enough to warrant this process and so RMD is not often diagnosed unless there are extremely interfering or disabling symptoms.

Additionally, 80-90% of individuals with Restless Legs Syndrome show periodic limb movements as observed on a polysomnogram, which are not common in RMD patients.

However, use of a polysomnogram can help distinguish one disorder from the other as RMD involves movements in both REM and NREM sleep, which is unusual for seizures.

In such a therapy, affected individuals are asked to perform RMD-like motions during the day in a slow and methodic manner.

Such behavioral training has been shown to carry over into sleep, and the forcefulness of the RMD movements is reduced or eliminated.