Tremor

Tremors are the most common movement disorder and are defined as rhythmic, involuntary movements of one or more parts of the body. Tremors are classified as resting or action tremor (i.e., postural and intention tremors). Resting tremors typically occur in patients with Parkinson's disease (PD) and usually present as asymmetrical tremors that occur during rest. Postural tremors are usually essential or physiologic. Essential tremors are the most common type of tremor and usually involve the hands and head. They characteristically improve with alcohol consumption. Physiologic tremors occur when holding a position against gravity and are enhanced by increased sympathetic stimulation (e.g., caffeine, anxiety). Intention tremors suggest cerebellar lesions, which typically occur with strokes, trauma, or tumors. Patients present with a coarse hand tremor that is aggravated by goal-directed movements. A combination of tremor types is also possible. The diagnosis of tremors is typically clinical. Further laboratory tests and imaging may be required to determine the underlying condition. Treatment depends on the type of tremor.

Essential tremor

• Most common form of tremor
• Bimodal distribution: teens and 6^th decade of life (common in elderly patients)
• Etiology: Positive family history (50–70%; autosomal dominant inheritance); or sporadic; benign form
• Clinical features
  • Localization: hands (about 90%), head (about 30%; "yes-yes” or "no-no” motion), voice (about 15%)
  • Mostly bilateral postural tremor with a frequency of 5–10 Hz
    • Slowly progressive
    • Worse with voluntary movement , stress, fatigue, and caffeine
    • Resolves at rest
    • Improves with alcohol consumption
  • The essential tremor may be accompanied by an intention tremor (in 50% of patients) and/or a resting tremor (in 15% of patients)
• Diagnosis: Usually a clinical diagnosis of exclusion
• Treatment
  • Drugs of choice: propranolol or primidone
  • Alternatives (if propanolol and primidone are unresponsive or contraindicated)
    • Other beta blockers (e.g., atenolol, sotalol)
    • Other anticonvulsants (e.g., gabapentin, topiramate) including certain benzodiazepines (e.g., alprazolam, clonazepam)
  • In drug-resistant cases
    • Deep brain stimulation (DBS)
    • Thalamotomy

Physiologic tremor

• A physiologic tremor does not suggest a disorder , while an enhanced physiologic tremor oscillations, more visible), may be more significant and debilitating
• Age of onset: may occur at any age
• Etiology: enhanced by sympathetic stimulation
  • Stress, exercise, or fatigue
  • Intoxication: mercury poisoning, caffeine, alcohol
  • Drug-induced: valproate, lithium, SSRIs, tricyclics, beta-2 agonists, levothyroxine, immunosuppressants (e.g., daclizumab, basiliximab)
  • Withdrawal: alcohol, benzodiazepines, barbiturates, marijuana
  • Medical conditions: hyperthyroidism or pheochromocytoma, Lewy body dementia
  • Other: magnesium deficiency, hypoglycemia , Wilson's disease
• Clinical features
  • Usually a fine bilateral postural tremor in the hands and fingers (∼ 10 Hz)
  • Occurs while holding a position against gravity (e.g., extending arms in front of body)
• Diagnosis: depends on suspected underlying cause (thyroid function tests, blood glucose level, review of medications, history of substance use)
• Treatment: usually reversible once the underlying cause is treated; propranolol may be considered under certain conditions

Orthostatic tremor

• Epidemiology
  • Rare
  • Sex: ♀ > ♂
  • Age of onset: 60 years (usually)
• Etiology: unknown
• Clinical features: long periods of standing may lead to:
  • Trembling feeling in the legs
  • Subjective feeling of unstable balance, and falling over
• Diagnosis
  • Clinical diagnosis:(Synchronized) shaking of the legs may be seen or felt by the examiner.
  • Electromyography of the legs while patient is standing; detection of 13–18 Hz tremor
• Treatment
  • Symptom-based
  • Medicinal: clonazepam, gabapentin

Consider an essential tremor in a patient presenting with chronic bilateral hand tremors without further neurological deficits and a positive family history!

References:^{[1][2][3][4][5][6][7]}

• Flapping tremor (Asterixis)
  • Etiology
    • Metabolic encephalopathy (especially alcohol-induced hepatic encephalopathy)
    • Wilson's disease
  • Clinical features
    • Irregular, high oscillations when arms and hands are extended
    • Short loss of postural muscle tone followed by a corrective reflex movement → more of a negative myoclonus than a tremor
    • In Wilson's disease: ascites, jaundice, Kayser-Fleischer rings, muscle spasms, and mental symptoms
  • Diagnosis
    • Determine cause of encephalopathy (e.g., blood tests, CSF analysis, cCT/MRI, EEG)
    • See also Wilson's disease
  • Treatment: : see “treatment” sections of hepatic encephalopathy and Wilson's disease
• Psychogenic tremor
  • Etiology
    • Conversion disorder
    • Other psychiatric disorders
  • Clinical features
    • Mostly postural tremor with a sudden onset
    • Worsens under direct observation and diminishes with distraction
  • Diagnosis
    • Ask about somatization in past history
    • Diagnosis of exclusion
  • Treatment: cognitive-behavioral therapy
• Dystonic tremor: Postural and intention tremor (can occur at rest) that occur in muscles with preexisting dystonia
• Holmes tremor: : Low frequency, large oscillations, postural and intention tremor caused by stroke lesions in the midbrain, thalamic, cerebellar, or pontine.

References:^[1][2][8]