Myoclonus vs chorea

“Anyone can moonwalk. It’s making it smooth that matters” Michael Jackson never once said.

It’s all about smoothness when trying to decide between the dance like “there’s a snake trapped in my arm” chorea and the sudden involuntary contraction of myoclonus.

A boy in his mid teens presented with two years of shaking episodes, worse in the morning. He presented today as it had worsened over the past two days to the point when he could not open a bag of crisps without spilling half of them on the floor. These episodes could come in clusters, or on their own. It usually affected his hands more than his legs. He had occasionally fallen, where he went floppy and then twitched all over. He had never lost consciousness.  The symptoms were sometimes unilateral and at other times bilateral. He had no headache or visual symptoms. He had a normal development and academic ability. He had no family history of epilepsy or anything else of note.

He had a normal cranial nerve, upper limb and lower limb examination. I witnessed some of these abnormal movements. There were sudden, unprovoked contractions of his arm muscles, lasting less than a second. Sometimes two would occur in quick succession.

How could I convince myself it was not chorea? I had watched a few YouTube videos on chorea, and remembered this case in particular:

The chorea movements seemed to travel along a part of the body, and last more than a second at least. It was like a magician trying to distract you. Myoclonic jerks seemed more like someone had delivered a mild electric shock.

We felt there was too much staccato and not enough smooth for chorea. A provisional diagnosis of juvenile myoclonic epilepsy was made, and the patient referred to the first fit clinic.


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