Review Question - QID 217208

This patient with an intermittent, low-amplitude, high-frequency tremor that persists with distraction likely has an enhanced physiologic tremor. Enhanced physiologic tremors may become apparent in patients with increased sympathetic nervous system activity and may be caused by certain medications (e.g., selective serotonin reuptake inhibitors such as fluoxetine).

Physiologic tremors are low-amplitude, high-frequency tremors that may occur in healthy individuals. These tremors may become more apparent and bothersome due to medications or diseases that increase sympathetic tone, in which case they are labeled enhanced physiologic tremors. For example, caffeine, corticosteroids, and selective serotonin reuptake inhibitors have been associated with enhanced physiologic tremors. Conditions such as hyperthyroidism and anxiety disorders may also cause enhanced physiologic tremors. Features that support the diagnosis of physiologic tremor include persistence with distraction, bilateral limb involvement, worsening of the tremor with movement, and acute worsening of tremor concurrent with initiation of a new medication. The diagnosis of enhanced physiologic tremor is clinical and requires the exclusion of pathologic causes of tremor by a thorough history and physical exam. In cases of enhanced physiologic tremor hypothesized to be caused by medication, a decrease in the dose or cessation of the medication may be therapeutic, if feasible.

Lenka and Jankovic reviewed the types of tremors. They found that physiologic tremor usually involves the bilateral hands and fingers and is the most common postural tremor. They recommended that for severe cases of enhanced physiologic tremor, propranolol can be used for treatment.

Incorrect Answers:
Answer 1: Cerebellar tremors are low-frequency, high-amplitude tremors that worsen with intention (e.g., worsening with finger-to-nose testing). Cerebellar tremors are typically associated with other signs of cerebellar dysfunction such as gait imbalance, ataxia, and dysmetria, which are not evident in this patient.

Answer 2: Functional tremors (also known as psychogenic tremor) occur abruptly and may affect any limb. These tremors may be associated with psychiatric disorders such as anxiety, depression, and post-traumatic stress disorder (PTSD). Features supporting a diagnosis of functional tremor include cessation of the tremor with distraction and variability in the presentation of the tremor.

Answer 3: Orthostatic tremor is characterized by rapid muscle contraction of the legs when standing leading to feelings of imbalance. These tremors typically do not affect the upper extremities and present only when standing up, unlike the enhanced physiologic tremor of this patient.

Answer 4: Parkinson tremor is a feature of Parkinson disease and is characterized by a resting, "pill-rolling" tremor that improves with action. Typically, other signs of Parkinson disease may be evident, such as micrographia, bradykinesia, and rigidity. This patient's age and lack of Parkinsonian symptoms make Parkinson tremor unlikely.

Bullet Summary:
Enhanced physiologic tremors are low-amplitude, high-frequency tremors that worsen with movement and are associated with states of increased sympathetic tone (e.g., drugs, hyperthyroidism, anxiety, and caffeine).