Myoclonus (Pediatric) Workup

Myoclonus may be tested by looking at the electrical activities in brain and affected muscle(s). Electromyography (EMG) of the muscles typically shows the duration and frequency of the myoclonic bursts, and whether these bursts spread to other spinal segments (as is seen in propriospinal myoclonus). It may also be helpful in determining whether jerking movements occur simultaneously in more than one limb, or whether they flow gradually down the body. In cortical myoclonus, there may be an excessively large brain electrical response to electrical stimulation of the hands or feet. This response is tested by using somatosensory-evoked potentials (SSEPs). In some cases, it is also possible to demonstrate the myoclonic electrical signal in muscle following a tendon tap. This may be helpful in diagnosing cortical reflex myoclonus.

In any form of myoclonus, it is important to look for a cause. Any medication or toxin that could produce the symptoms should be removed if possible. Family history needs to be investigated and metabolic studies may be appropriate, particularly if there are other symptoms or if symptoms become progressively worse. Metabolic tests may include screening for treatable disorders such as Wilson's disease. Since myoclonus may be a symptom of general systemic illness, including liver failure and some types of tumors, it is important to screen for general health problems. In particular, in the opsoclonus-myoclonus syndrome, the child should have a CT or nuclear medicine scan of the chest and abdomen as well as blood and urine tests. These tests look for evidence of a neuroblastoma tumor. If there is a suspicion of an epilepsy syndrome, an electroencephalogram (EEG) is. Brain MRI is important to look for tumors, stroke, malformations, or other structural lesions near the cortex, brainstem, or cerebellum. This is particularly true if the myoclonus is focal or if the child is suspected of having the syndrome of epilepsia partialis continua. Since certain viral infections can cause myoclonus, a spinal tap is sometimes needed for this diagnosis.

Many cases of essential myoclonus or essential myoclonus-dystonia will improve with small amounts of alcohol. Although this is useful for diagnosis, it is not helpful for long-term treatment.

	Treatment