Palatal tremor (palatal myoclonus)
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文摘
Palatal Tremor (palatal myoclonus, palatal nystagmus, brainstem myorhythmia) is a rare rhythmic (1-5 Hz) movement disorder which can be classified into two forms: The first is essential PT (EPT) presenting with a rhythmic earclick synchronous with the palatal activity as the major symptom. The second is symptomatic palatal tremor (SPT) developing following a lesion within the Guillain-Mollaret triangle and often involving other cranial nerve or extremity muscles. Besides these two classical forms of palatal tremor some patients do exist for which a clearcut classification is still lacking. Recent evidence suggests that only SPT is associated with olivary pseudohypertrophy. SPT is considered a model of a human tremor and neurophysiologic features suggest, that the rhythmic activity is transmitted through brainstem-pathways to the majority of motor nuclei contralateral to the olivary hypertrophy. On the same side abnormal motor learning can be demonstrated probably indicating an abnormality of cerebellar function. Cerebellar metabolism is reduced on the side contralateral to the affected inferior olive. The pathophysiology of EPT is distinct from SPT but remains obscure. The findings in palatal tremor suggest some new hypotheses for the origin of postural tremors like essential tremor.