Essential tremor

Essential tremor (ET), also called benign tremor, familial tremor, and idiopathic tremor, is a medical condition characterized by involuntary rhythmic contractions and relaxations (oscillations or twitching movements) of certain muscle groups in one or more body parts of unknown cause. It is typically symmetrical, and affects the arms, hands, or fingers; but sometimes involves the head, vocal cords, or other body parts. Essential tremor is either an action (intention) tremor—it intensifies when one tries to use the affected muscles during voluntary movements such as eating and writing—or it is a postural tremor, which occurs when holding arms outstretched and against gravity. This means that it is distinct from a resting tremor, such as that caused by Parkinson's disease, which is not correlated with movement. Unlike Parkinson's disease, essential tremor may worsen with action. Essential tremor is a progressive neurological disorder, and the most common movement disorder. Though not life-threatening, it can certainly be debilitating. Its onset is usually between 40 and 50 years of age, but it can occur at any age. The cause is poorly understood. Diagnosis is made by observing the typical pattern of the tremor coupled with the exclusion of known causes of such a tremor. There is currently no medical test available to identify an essential tremor. While essential tremor is distinct from Parkinson's disease, which causes a resting tremor, essential tremor is nevertheless sometimes misdiagnosed as Parkinson's disease. Some patients have been found to have both essential tremors and resting tremors. Treatments for essential tremor include medications, typically given sequentially to determine which provides the most efficacy with least side effects. Clostridium botulinum toxin (Botox) injections and ultrasound are also sometimes used for cases refractory to medications.