NCC with Kinsbourne type OMAS (opsoclonus, myoclonus and Ataxia syndrome) secondary to phenytoin toxicity

Background: OMS is a rare neurological disorder affects approximately 1/1,000,000 of the worldwide population without gender, generic or ethnic predilection1. The most common causeof OMS in children is paraneoplastic, especially due to neuroblastoma, parainfectious, congenital, metabolic or drug toxicity. The exact pathophysiology of OMS is not known2, Although opsoclonus and myoclonus both are adverse effect of phenytoin but opsoclonus– myoclonus syndrome (OMS) as a consequent effect of phenytoin toxicity has rarely been reported in the literature 3. Objective: The purpose of reporting this case is to emphasize that as phenytoin has narrow therapeutic window and myriad of side effects even a minor increase in dose leads to toxicity like in our patient there was appearance of OMS after increment of dose of phenytoin. Methods: We present the case of a 19 years old male who was a known case of seizure disorder and presented to us with generalized tonic clonic seizure, opsoclonus, myoclonus and ataxia. Results: A 19 years old male who was diagnosed with? NCC? Tuberculoma on basis of brain imaging around and was started on tab phenytoin, presented to us with generalized tonic clonic seizure. Dosage of phenytoin was increased around one and half month back due to one episode of GTCS and tablet valproate was added in treatment recently for intermittent abnormal jerky movement but there was no improvement in his symptoms. Patient presented in drowsy state and was found to have exaggerated deep tendon reflexes. Subsequently, dysarthria, difficult walking, jerky movements of upper limb, urinary incontinence, slurred speech, opsoclonus with evidence of myoclonic jerks involving all four limbs, face and eyelids. He had severe trunk as well as gait ataxia, incoordination and dysmetria. Hematological, biochemical and cerebrospinal fluid examinations were normal. Brain magnetic resonance imaging revealed likely possibility of neurocyticercosis and serum phenytoin level was markedly increased (56 mg/L). Phenytoin was stopped and tab clobazam 5mg HS was started along with valproate. All his symptoms including opsoclonus–myoclonus and ataxia gradually disappeared over next 10 days. Therefore, phenytoin induced opsoclonus–myoclonus ataxia syndrome was the final diagnosis. The repeat estimation of serum phenytoin level was within normal limits (18 mg/L). Conclusion: This case report of phenytoin toxicity will help to alert physicians about the toxic manifestations of phenytoin in patients on long as well as short term therapy. Treatment with phenytoin should be individualized based on the patient’s clinical response, plasma drug levels and signs of toxicity and regular follow up to evaluate compliance and response to therapy. Monitoring of serum phenytoin levels and adverse drug reactions should be done even when the seizure is under control and especially when there are doubts of early toxic effects. We should also educate the patients and caregivers about the clinical manifestations of phenytoin toxicity, so that it can be recognized early and treated appropriately.