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Essential tremor
Other namesIdiopathic tremor
Spiral drawing of Essential Tremor patient.svg
Archimedean spiral drawings from a man with a unilateral essential tremor. The spiral on the left was drawn by the subject using the left hand, and the one on the right using the right hand.
SpecialtyNeurology
Usual onsetAny age, but typically after 40
CausesUnknown
Risk factorsFamily history, exposure to particular toxins
Diagnostic methodBased on symptoms
Differential diagnosisCerebellar tremor, dystonic tremor, multiple sclerosis, Parkinson's disease
TreatmentMedications, surgery
MedicationBeta blockers, primidone, anti-epileptics, topiramate, gabapentin, levetiracetam, benzodiazepines
FrequencyAnnual incidence of 23.7 per 100,000 (2010)

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 typically is 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, present with sustained muscle tone. This means that it is distinct from a resting tremor, such as that caused by Parkinson's disease, which is not correlated with movement.

Essential tremor is a progressive neurological disorder, and the most common movement disorder. Its onset is usually after age 40, but it can occur at any age. The cause is unknown. Diagnosis is by observing the typical pattern of the tremor coupled with the exclusion of known causes of such a 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 is most effective coupled with which has the least troublesome side effects. Clostridium botulinum toxin (Botox) injections and ultrasound are also sometimes used for cases refractory to medications.

Signs and symptoms