Non-Hyperammonemic valproate encephalopathy

Abstract

A 21-year-old male known case of primary hypothyroidism, Seizure disorder sequelae of an old trauma receiving sodium valproate, clobazam and phenobarbitone for control of Generalized tonic clonic seizures reported to neurology OPD with history of altered sensorium and gait unsteadiness for 1 week with history of hike in valproate dose 2 weeks before. On examination he was drowsy. Neurological examination was unremarkable except for gait unsteadiness and ataxia. Patient was admitted and evaluated for acute worsening. All (the) biochemical parameters including complete blood count, liver function tests, kidney function tests, routine urine examination, arterial blood gas analysis, blood and urine culture tests were normal. CSF analysis was also normal. Repeat MRI brain was also done which depicted all old changes with no fresh changes which will account for worsening of his sensorium. EEG was suggestive of diffuse encephalopathy. Thyroid function tests were also normal. Valproate encephalopathy was suspected and Valproate was empirically stopped and he was put on levetiracetam and phenytoin. His sensorium improved rapidly after stoppage of valproate with normalization of EEG. Serum valproate Levels were high with serum ammonia levels were in the normal range. We made the inference of nonhyperammoneamic valproate encephalopathy. This case highlights the existence of non-hyperammonemic valproate induced encephalopathy, suggesting mechanisms other than hyperammonemia responsible for this encephalopathy.

Keywords: EEG; Hypothyroidism; Valproic acid.

Fig. 1:

EEG done after admission during drowsy state showed a marked diffuse background slowing intermixed with 2-2.5 Hz of high-amplitude slow waves, occurring synchronously over both hemispheres, which did not change afterinjectionof IV diazepam.

Fig. 2:

Electroencephalogram appears almost completely normal, with well-developed α-waves in the posterior head regions(arrows).