Myoclonus: Recurrent Body Jerks

by Colleen

My 15 months old experiences whole body jerks similar to the movements when one is having hiccups. They are frequent, and almost at regular intervals. The periodic jerking of my son’s body continues also when he is asleep, but at a slower rate.

When he jerks, his whole body moves. He raises his hands and legs. The legs are lifted up but only a bit, and especially when he is seated. Rest all seems normal. His cognitive development is normal for his age.

Up till now no tests have been done, and he has not received any medications for these involuntary abnormal movements.
Doctor, what could be the issue?

The Expert, Ren Chats Answers

The information provided suggests “generalised myoclonic jerks”.
Myoclonic activity can originate from any part of the nervous system (cortex, brainstem, spinal cord or nerve), and at times as a reflex phenomenon in response to sensory stimuli, like repetitive sounds, rocking and movements during automobile rides.

1 in 10 cases have history of febrile seizures. In more severe cases recent history of vaccination or febrile illness may be present. Parents who indulge in recreational drugs may unknowingly expose their children to toxins that jeopardise optimal function of the neuro-transmitters in yet developing nervous system.

Immature nervous system is well known to cause variety of irregular jerky movements in the neonatal period. But in older infants and toddlers one has to consider several other causes, which can be grouped as follows:

1. Physiological myoclonus
The causes for physiological myoclonus range from normal ongoing development of the nervous system to those induced by excessive muscular activity.

2. Symptomatic to underlying neurological disorder.
These are many, and they include some serious underlying disorders. Since your son has normal development, and is generally healthy, I will skip these for now..

3. Essential myoclonus occurs in absence of other neurological symptoms.
Familial predisposition is common in these cases. Usually, at least one parent would have history of similar movement disorder. This parent carriers the abnormal dominant trait on his/her non-sex chromosomes, which has 50-50 chances of being passed down to each of the offspring.

A genetic link to parasomnia (group of unusual behaviour of the nervous system during sleep), and migraine has also been suggested.

4. Epileptic – Benign myoclonic epilepsy of infancy
It is a rare disorder, the cause for which is not known. It is characterized by brief fits of generalised spasmodic jerky contractions in children below 3 years of age. However, some cases with later onset have also been reported. It typically occurs in kids who are developmentally normal, and the seizures too disappear sometime during childhood. Nevertheless, the term “benign” applied is probably questionable because –

a.) Though electroencephalograms (EEG) taken in between the attacks are normal, the tracings during the attacks show generalised abnormalities.

b.) Valproic Acid, an anti-epileptic medication, is successfully used to control the seizures.

c.) Some affected children are unable to cope with the normal school curriculum. It is because these children suffer mild to severe delay in their cognitive development.

d.) After the seizure free period, a few children who suffered from benign myoclonic epilepsy of infancy develop idiopathic generalised epilepsy.

What should you do?

Considering the whole scenario, I would advise you to contact your son’s doctor at the earliest. It would be worthwhile to involve a paediatric neurologist as well.
Hope this helps.
Take Care!
And please continue the follow-up evaluations till your son is well settled in his school, even if he is supposedly doing well. Hopefully No abnormality will ever be found. Even then it would be worth the trouble on the basic principle of “a stitch in time saves nine”

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