[The use of electromyographic examination as a diagnostic tool and phenytoin sodium as treatment in a case of classic springhalt in a Dutch warmblood horse].

The study focuses on the diagnosis and treatment of a condition known as stringhalt in a horse, using electromyographic examination as a diagnostic tool and phenytoin sodium as a treatment.

Understanding Stringhalt

• Stringhalt is a neuromuscular disorder in horses that causes a sudden, jerking lifting of one or both of the hind legs. The consequent abnormal movement is involuntary and often happens when the horse is turning, backing up, or starting to move.
• In this study, the particular case is of a unilateral stringhalt exhibited for 18 months in a 4-year-old Warmblood gelding’s right hind limb.

Use of Electromyography (EMG)

• The only abnormalities detected through the EMG were a prolonged insertion activity, fibrillation potentials, and positive waves at rest. There was also enhanced EMG activity in the right lateral digital extensor muscle on muscle contraction.
• This was interpreted as denervation (loss of nerve supply) and hyperirritability of the said muscle.
• The study found both similarities and differences in this case with Australian stringhalt, another variant of the disorder.
• The EMG examination was found to be helpful in clarifying the etiology (cause) of the classical form of stringhalt, as the only abnormality in this patient was an abnormal electrical activity in one specific muscle.

Phenytoin Sodium as Treatment

• Phenytoin sodium was administered orally. The dosage varied between 15 and 9.3 mg/kg body weight in an attempt to influence the hyper-flexia (excessive flexion).
• Therapeutic effects without any side effects were seen at plasma concentrations between 5.1 and 9.9 mg/L at a dosage of 12 mg/kg body weight given twice daily. This is in line with data referenced in other research literature that suggests effective plasma concentrations fall within the 5-10 mg/L range.
• In this type of stringhalt, the horse was relieved of the excessive tarsal (ankle) hyperflexion by phenytoin, similar to its effect in cases of Australian stringhalt.