Forelimb tic in a horse.

This article presents the case of an 18-month-old male Quarter Horse that developed a tic in its right forelimb after an injury. Despite various treatments tried, the tic persisted for 21 days of hospitalization but had ceased 10 weeks after discharge.

Case Description

• The case study is about an 18-month-old male Quarter Horse that was referred for evaluation because of a tic in its right forelimb.
• This tic began four weeks after the horse injured its right forelimb.
• The right forelimb appeared to be paretic, meaning it showed signs of weakness or partial paralysis. The horse also displayed constant regular twitches of variable intensity, which often caused his trunk, neck, and head to move.
• The horse frequently threw the affected limb forward. This tic persisted even during the horse’s sleep.

Treatments and Interventions

• The tic disappeared when the horse was under general anesthesia or sedated with xylazine, but it was unaffected by several other drugs including acetylpromazine, diphenylhydantoin, diazepam, carbamazepine, trimethadione, procainamide, quinidine, propranolol, dantrolene, methocarbamol, dimethyl sulfoxide mixed with xylocaine, and it remained unchanged by low volar nerve anesthesia.
• The twitching remained unchanged during the 21 days the horse was hospitalized, but surprisingly, it had stopped 10 weeks after discharge.

Evaluation and Diagnosis

• The researchers carried out electromyographic tracings of the horse’s limb and neck, along with radiographs of the cervical and proximal thoracic spine, scapulohumeral joints, and adjacent ribs, all of which turned out normal.
• The researchers suspected a localized spinal cord lesion or peripheral neuropathy, and neuralgia secondary to trauma, which might have been causing the unusual tic in the horse’s forelimb.