Description

• Essential tremor is a postural (occurring with voluntary maintenance of a position against gravity) or kinetic (occurring during voluntary movement) flexion–extension tremor that is slow and rhythmic and primarily affects the hands, forearms, head, or voice with a frequency of 4 to 12 Hz. Symptoms must be present for ≥3 years for a formal diagnosis of essential tremor.
• Older patients tend to have lower frequency tremors, whereas younger patients exhibit frequencies in the higher range.
• The tremor occurs in the absence of other neurologic signs such as dystonia, ataxia, or parkinsonism. The disease may be familial, sporadic, or associated with other movement disorders. Incidence and prevalence increase with age, but symptom onset can occur at any age. The tremor can be intermittent and exacerbated by emotional or physical stressors, fatigue, and caffeine.
• Systems affected include neurologic, musculoskeletal, ear/nose/throat (ENT) (voice).

Epidemiology

Essential tremor is the most common pathologic tremor in humans.

Etiology and Pathophysiology

• Suspected to originate from an abnormal oscillation within thalamocortical and cerebello-olivary loops, as lesions in these areas tend to reduce essential tremor
• Essential tremor is not a homogenous disorder; many patients have other motor manifestations and nonmotor features, including cognitive and psychiatric symptoms.

Commonly Associated Conditions

• Can be present in 10% of patients with Parkinson disease (PD); characteristics of PD that distinguish it from essential tremor include 3- to 5-Hz resting tremor; accompanying rigidity, bradykinesia, or postural instability; and no change with alcohol consumption
• Patients with essential tremor have a 4% risk of developing PD.
• Resting tremor, typically of the arm, may be seen in up to 20–30% of patients with essential tremor. Although action tremor is the hallmark feature of essential tremor, it is commonly found in patients with PD as well.