OrthostaseTremor

OrthostaseTremor, commonly referred to as orthostatic tremor, is a rare movement disorder characterized by a high-frequency tremor of the legs that emerges when a person stands still and is relieved by walking, sitting, or lying down. The tremor is typically most noticeable as a feeling of unsteadiness rather than a visible shake. Electrophysiological testing often detects a tremor frequency in the 13 to 18 Hz range.

Clinical features include onset in middle to older adulthood, gradual progression, and marked instability when standing. The tremor is present during upright posture but not at rest and may lead to a need to shift weight or move the feet. Patients frequently report difficulty standing still and may develop avoidance of activities that require prolonged standing.

Diagnosis relies on history and physical examination, supported by electrophysiological studies such as surface or intramuscular EMG showing synchronized high-frequency bursts in leg muscles during standing. The diagnosis is made by demonstrating that the tremor occurs with standing and diminishes with movement, while other causes of gait disturbance are excluded.

Etiology and pathophysiology are not fully understood. Evidence suggests a central generator involving brainstem and cerebellothalamocortical networks that produces rapid oscillatory activity when upright. There are rare familial reports, but most cases appear sporadic.

Treatment aims at symptom relief. No disease-modifying therapy is established. Low-dose benzodiazepines (eg, clonazepam) and anticonvulsants (eg, gabapentin or pregabalin) may help in some patients. Physical therapy and mobility aids can improve safety, and deep brain stimulation has been reported only in isolated cases. The condition tends to be chronic with variable impact on function.