Dystonic tremor in Writer's cramp Mimicking primary handwriting tremor

Writer's cramp is a task-specific focal dystonia with peculiarity of occurring only during handwriting. The presence of abnormal posturing and dystonic tremor may exhibit distinctive patterns across individuals, and may closely resemble primary writing tremor, especially when dystonic postures are mild.

We present a 48-year-old right-handed Filipino businessman who developed a gradually worsening right-hand tremor confined to handwriting over one year, stabilizing after six months. Neurological examination was otherwise normal, but writing tests revealed dystonic wrist extension and shoulder abduction, along with wrist rotational/pronation-supination dystonic tremor during writing. Wavy/oscillating drawing patterns were observed. Diagnosis of writer's cramp was made, which mimicked primary writing tremor due to overlapping features. Multiple oral medications were ineffective, but ultrasound-guided botulinum toxin injections led to clinical improvements, with better handwriting during faster writing and worse at slower speeds.

This case underscores the complexity of diagnosing and treating task-specific dystonia with tremor. Incorporating tests like line-drawing at different speeds, including vertical and diagonal lines, can enhance evaluation.