Essential tremor is the most prevalent tremor disorder. Despite of that, very little is known about the responsible mechanisms. This is a review article emphasizing the pathophysiology of essential tremor, but it also includes epidemiology, clinics and treatment.
Clinically essential tremor shows great heterogeneity. It is characterized by a 4-12 hz kinetic and/ or postural tremor mainly affecting the upper extremities. Tremor can also be seen in the neck, lower extremities, voice, face and truncus. Essential tremor is a progressive disorder, in worst case leaving the patient unable to eat and dress. Medical treatment, mainly by propranolol and/ or primidon, alleviates the symptoms in 50 %. Alternatively “deep brain stimulation” (DBS) can be done. Many cases show autosomal dominant pattern of inheritance, but some are sporadic.
The tremor is probably generated by one or more central oscillators. We know that GABAergic mechanisms are involved. The question is where in the CNS the oscillator is situated. Wherever the origin, the causative signals are sent from thalamus to the cortical motor areas. Thalamus could of course be the oscillator, but both clinical and image studies point to cerebellum. A lesion in the cerebellum may convincingly cure the essential tremor. Oliva inferior, which is another step retrograde, is debated, but totally it seems that the evidence suggesting this is not strong enough. Because of the heterogeneity of the disorder, one must not forget the possibility that essential tremor constitutes a number of disease entities with many different pathophysiological mechanisms.