Reversible subacute peripheral neuropathy induced by phenytoin

Area of Science:

• Neurology
• Pharmacology
• Toxicology

Background:

• Phenytoin (diphenylhydantoin) is a widely used anticonvulsant medication for seizure management.
• Long-term phenytoin use can be associated with various adverse effects.
• Monitoring for neurological complications is crucial in patients on chronic anticonvulsant therapy.

Observation:

• A patient undergoing one year of phenytoin treatment for seizures developed dysesthesia and loss of sensory and reflex function in the legs.
• Serum phenytoin levels were within the therapeutic range during treatment.
• No other signs of clinical toxicity were observed.

Findings:

• The patient's symptoms of peripheral neuropathy, including dysesthesia and sensory/reflex loss, were directly linked to phenytoin therapy.
• Discontinuation of phenytoin led to the complete resolution of the neurological deficits.
• This suggests phenytoin-induced peripheral neuropathy as the cause of the observed symptoms.

Implications:

• This case highlights a potential neurotoxic side effect of phenytoin, even within therapeutic drug levels.
• Clinicians should consider phenytoin-induced peripheral neuropathy in patients presenting with unexplained leg sensory and reflex abnormalities.
• Early recognition and discontinuation of the offending drug can lead to favorable outcomes and symptom resolution.