Sensory trick in upper limb dystonia.

Area of Science:

• Neurology
• Movement Disorders

Background:

• Sensory trick (ST) maneuvers offer temporary relief for dystonia, observed in 44%-89% of cranial-cervical and 20% of upper limb dystonia cases.
• Idiopathic adult-onset upper limb dystonia often presents with writing difficulties.

Purpose of the Study:

• To determine the prevalence of sensory trick in idiopathic adult-onset upper limb dystonia.
• To evaluate if sensory trick can differentiate dystonic tremor from non-dystonic tremor.

Main Methods:

• 37 patients with idiopathic upper limb dystonia and 19 with non-dystonic action tremor wrote a sentence before and after a standardized sensory trick.
• Handwriting readability was assessed by three blinded observers.

Main Results:

• 13% of patients self-reported prior ST use; 38% showed handwriting improvement with the standardized trick.
• The standardized trick improved handwriting in 42% of dystonic tremor patients but none with non-dystonic tremor (p=0.003).
• High interobserver agreement (kappa=0.86) was noted for ST effectiveness.

Conclusions:

• Sensory trick may be more prevalent in upper limb dystonia than previously reported.
• An effective sensory trick could be a diagnostic hallmark for idiopathic dystonia.
• The absence of an effective sensory trick may aid in identifying non-dystonic upper limb tremor.