Mirror movements or functional tremor masking organic tremor

Area of Science:

• Neurology
• Neurophysiology

Background:

• Functional tremors are diagnosed using clinical and physiological criteria like entrainment and distractibility.
• Psychosomatic comorbidities are often associated with functional tremors.
• Neurophysiology plays an underrecognized role in diagnosing tremors.

Observation:

• A 62-year-old woman with a history of polio presented with tremor, initially suspected to be functional.
• Subsequent evaluation revealed a variable and entrainable tremor, suggestive of a functional etiology.
• Neurophysiological study identified an underlying organic tremor, distinct from the functional presentation.

Findings:

• Tremor entrainment with contralateral hand tapping can be mistaken for mirror movements or functional movements.
• The underlying organic tremor was not entrained by external stimuli.
• Motor overflow, especially with large amplitude movements, can mimic mirror movements.

Implications:

• Functional tremors can obscure the presence of an underlying organic tremor.
• Objective neurophysiological assessment is vital for accurate tremor diagnosis.
• Refining clinical and physiological evaluation techniques can improve the identification of organic etiologies in tremor patients.