Diagnosis and treatment of common forms of tremor

Abstract

Tremor is the most common movement disorder presenting to an outpatient neurology practice and is defined as a rhythmical, involuntary oscillatory movement of a body part. The authors review the clinical examination, classification, and diagnosis of tremor. The pathophysiology of the more common forms of tremor is outlined, and treatment options are discussed. Essential tremor is characterized primarily by postural and action tremors, may be a neurodegenerative disorder with pathologic changes in the cerebellum, and can be treated with a wide range of pharmacologic and nonpharmacologic methods. Tremor at rest is typical for Parkinson's disease, but may arise independently of a dopaminergic deficit. Enhanced physiologic tremor, intention tremor, and dystonic tremor are discussed. Further differential diagnoses described in this review include drug- or toxin-induced tremor, neuropathic tremor, psychogenic tremor, orthostatic tremor, palatal tremor, tremor in Wilson's disease, and tremor secondary to cerebral lesions, such as Holmes' tremor (midbrain tremor). An individualized approach to treatment of tremor patients is important, taking into account the degree of disability, including social embarrassment, which the tremor causes in the patient's life.

Figure 1

Schematic and simplified synopsis of the brain regions and pathways involved in tremorogenesis. See text for details. (D₁, Dopamine receptor type 1; D₂, dopamine receptor type 2; exc., excitatory; GABA, γ-amino butyric acid; Glu, glutamate; GPe, external globus pallidus; GPi, internal globus pallidus; ICP, inferior cerebellar peduncle; inh., inhibitory; SCP, superior cerebellar peduncle; SNc, substantia nigra, pars compacta; SNr, substantia nigra pars reticulata; STN, subthalamic nucleus; VIM, ventrointermediate nucleus of thalamus.)

Figure 2

Complex nature of tremor at rest in Parkinson’s disease (PD). Electrophysiologic surface recording study. The surface electromyography (EMG) recordings of a 67-year-old man with PD reveal a rhythmic activity with a frequency of ~5 Hz in all muscles studied. All recordings shown were performed simultaneously. The antagonists, anterior tibial and gastrocnemius muscles, are activated in shifted phases, and a slight electrical activity was detected in the quadriceps musculature on the same side. The frequency in the electrophysiologic activity on the left and on the right side differs slightly, with 13 activations in the left anterior tibial muscle, but only 12 in the right side during the period represented in the figure. This indicates that tremors originate in separate circuits in the left and right sides, and the overall picture underscores the central origin and complex nature.

Figure 3

Entrainment of psychogenic tremor. Electrophysiologic surface recording study. A 28-year-old woman had developed tremor in her legs 3 months previously. The surface EMG recordings shown here were recorded with the patient standing. There is nearly simultaneous and rhythmic activity in both anterior tibial muscles, but the length, amplitude, and shape of the single bursts is less regular than in Figure 2. Simultaneous contractions in both limbs (upper row) often indicate voluntary activation. There is only a very slight antagonist activity simultaneous with a reflex-like tonic activity in all muscles. When the patient was asked to slowly tap down her right foot (lower row, black bar), the rhythmic activity almost completely abates (entrainment), suggesting a psychogenic cause for this patient’s tremor.