[Palato-pharyngo-laryngeal myoclonus]

Abstract

Palato-pharyngo-laryngeal myoclonus is well-known clinical criterion characterized by persistent, rapid, repetitive, rhythmic muscle twitch the rate of which ranges 50-200 Hz. It appears in the palate, pharynx, larynx, diaphragma, and the ocular or limb muscles, but the most common combination of the distribution is palate-pharyngo-laryngeal type or only palatal type. In most instances the movement is synchronous, but others show asynchronous myoclonus at different rates. There was a case report in which an electrical stimulation given at the ulnar nerve produced reset of myoclonus indicating that some feedback mechanism has some influence in the generation of pacemaker activity in the brainstem. This myoclonus has been considered to result from interruption of any one fiber system in a olivocerebellorubrotegment-olivary equipotential reverating circuit, so-called Guillain-Mollaret triangle. As etiological factors, cerebrovascular accidents are the most common, but various other causes have been encountered including tumor, trauma, inflammation, multiple sclerosis, electroshock, dialysis encephalopathy, and other degenerative neurological diseases. Analysis of the symptoms is the most important cure of the diagnosis, and this myoclonus is relatively easily differentiated from other involuntary movement, but recently MRI is a very effective examination to detect a lesion in the medulla visualizing the degenerative changes of the lower olivary nucleus. Clonazepam, trihexyphenidyl, carbamazepine, 5HTP and caeruletin have been reported as effective agents for this movement.