A 34-year-old woman has a coarse shaking tremor of both arms. When the examiner asks her to perform rhythmic finger tapping with one hand at varying speeds, the contralateral tremor changes frequency to match the tapping. EEG and serum ceruloplasmin are normal. What does this finding indicate?

• A Wilson disease
• B Functional (psychogenic) tremor ✓
• C Essential tremor
• D Parkinsonian rest tremor

Explanation

Entrainment, where an involuntary tremor shifts its frequency to match a voluntarily performed rhythm, indicates functional tremor because truly involuntary movements cannot be voluntarily entrained. Essential and parkinsonian tremors retain their characteristic frequencies independent of concurrent voluntary tasks. Normal ceruloplasmin excludes Wilson disease, which would also show Kayser-Fleischer rings and hepatic involvement.

Reference: Bradley's Neurology in Clinical Practice, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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