Shaking on Standing: A Critical Review

Abstract

Orthostatic tremor is a rare condition, though its exact prevalence is unknown, which is clinically characterized by a feeling of unsteadiness or being about to fall on standing and which disappears on walking, sitting, or lying down. It is generally accepted that classic orthostatic tremor manifests with a high-frequency tremor (>13 Hz) of the legs when standing. However, a number of patients initially reported as orthostatic tremor did not actually have such electrophysiological features. It is our experience that there is a clinical spectrum of different conditions presenting as shaking on standing, and this highlights the importance of the electrophysiology to aid the differential diagnosis of these disorders. Here, we provide a critical review of the clinical spectrum of shaking on standing, along with demonstrative electrophysiological recordings of some of these conditions.

Keywords: Parkinson's disease; essential tremor; orthostatic myoclonus; orthostatic tremor; tremor.

Figure 1

(A) EMG recording showing high‐frequency tremor of legs muscles on standing. (B) Coherence analysis between the right and left tibialis anterior muscles, disclosing a tremor peak at 17 Hz (R‐RF, right rectus femoris muscle; L‐RF, left rectus femoris muscle; R‐TA, right tibialis anterior muscle; L‐TA, left tibialis anterior muscle).

Figure 2

Slow (3‐ to 4‐Hz) tremor of the legs on standing (R‐RF, right rectus femoris muscle; L‐FR, left rectus femoris muscle).

Figure 3

(A) EEE‐EMG recording showing irregular, high‐frequency (14‐ to 17‐Hz) bursts of myoclonus in the legs when standing (RVM, right vastus medialis muscle; RTA, right tibialias anterior muscle; RGastro, right gastrocnemius muscle). (B) Nonsignificant coherence analysis between the right and left homologous leg muscles. (C) EEG‐EMG back averaging shows a cortical correlate of the myoclonic jerks (C4 references).

Figure 4

Orthostatic myoclonus on standing; negative myoclonus is indicated by red arrows. R‐Bic, right biceps muscle; R‐ECR, right extensor carpi radlialis muscle; R‐FDIO, right first dorsalis interossei muscles; R‐VM, right vastus medialis muscle; R‐TA, right tibialis anterior muscle; R‐Ga, right gastrocnemius muscle.