Symptomatic and essential palatal tremor. 2. Differences of palatal movements

Palatal tremor, a rhythmic movement disorder of the soft palate, may be described as two separate entities: symptomatic palatal tremor (SPT) and essential palatal tremor (EPT). The symptomatic form is associated with brain stem or cerebellar disease, whereas the essential form has no known etiology. A cardinal symptom of EPT is the presence of ear clicks, which do not occur in SPT. Visual observation of the movements in the two disorders suggests that the difference in symptoms is due to the activation of different palatal muscles, the levator veli palatini in SPT and the tensor veli palatini in EPT. Electromyographic recording from the levator veli palatini muscle showed abnormal bursting activity time locked to the palatal movements in patients with SPT, but not in those with EPT. Because the two palatal muscles are innervated by different cranial nerves, SPT and EPT are likely to have separate origins.