3A. Differential diagnosis of tremors

Tremors are classified as either resting tremors or action tremors. Resting tremors occur during rest, while action tremors occur during voluntary movement. There are two subtypes of action tremor:

• Resting tremor – occurs in rest
• Action tremor – occurs during voluntary contraction
  • Postural tremor – when holding arms out against gravity
  • Kinetic tremor – occurs when moving the arms
    • Intention tremor – tremor at the end of a targeted movement
    • Task-specific tremor

There are many possible causes of the different types of tremor. This topic will cover the most common.

Physiological tremor

Physiological tremor is a kind of postural tremor which occurs in healthy people who are exposed to certain factors, like:

• Stress
• Sympathetic activation
• Hyperthyroidism
• Caffeine
• Alcohol withdrawal

It’s a fine tremor with low amplitude. No treatment is necessary, only avoiding the trigger. Benzodiazepines may be used in severe cases.

Parkinson tremor

Parkinsonism involves a resting tremor. It’s asymmetric and is sometimes called a pill-rolling tremor because they often perform a special movement of the thumb and index finger as if you were rolling a pill between them.

Essential tremor

Essential tremor is a condition which causes a postural or kinetic tremor. It’s a hereditary autosomal dominant condition which worsens with stress, fatigue, or caffeine. It’s a fine tremor which affects the hands and the head. Interestingly, it improves with alcohol. It’s usually bilateral.

Pharmacological treatment like propranolol and antiepileptics can be used, but unfortunately they usually don’t improve the symptoms a lot. In very severe cases we can use deep brain stimulation of thalamic nuclei. (DBS can be effective for any kind of disabling tremor.)

Cerebellar tremor

Cerebellar injury (stroke, trauma, MS, alcohol) causes an intention tremor, a kind of kinetic tremor. It occurs during target-directed voluntary movements and is a coarse (low frequency) tremor where the person makes a slow “zigzag” movement towards the target. It can be unilateral or bilateral.

Other types of tremor

Neuropathic tremor can occur in case of any neuropathy, like diabetic neuropathy. The clinical features are variable.

Functional/psychogenic tremor is caused by psychiatric disease. The features do not correspond to any organic tremor, vary over time, and the clinical features change when the patient is distracted.

Flapping tremor, also called asterixis, is due to hepatic or uraemic encephalopathy and involves a characteristic flapping motion of the hands.