"Stretched Slinky" Sign: Another Clue to Functional Tremor.

OBJECTIVE

Functional tremor (FT) is the most common functional movement disorder, although its diagnosis can be challenging. Archimedes spiral drawings can be helpful in eliciting additional signs associated with tremor. Here, we present examples of an unusual looping of Archimedes spirals only seen in FT.

METHODS

Clinical information regarding demographic data, clinical history, and examination findings (including Archimedes spiral drawings) and investigation results of patients with FT in the movement disorders clinic were reviewed.

RESULTS

Three paradigmatic patients with FT demonstrated a unique looping appearance of Archimedes spiral drawings, akin to the appearance of a stretched slinky. The degree of randomness of the spirals varied from patient to patient and often mirrored tremor severity, regardless of the diagnosis.

DISCUSSION: The clinical hallmarks of a FT include a variable combination of positive signs, such as inconsistency (variability and distractibility), incongruence with known tremor syndromes, entrainment, and coactivation, although these findings might not always be present. We describe a unique appearance of spiral drawings, which could add as another clinical sign for FT. Consider looping of spirals as another diagnostic clue to FT.