Risk Factors Associated With Hyperammonemia Following Unprovoked Convulsive Seizures

This report describes a unique case of recurrent transient hyperammonemia (THA) following a first-time occurrence of generalized tonic-clonic seizure in a young adult, who went on to develop post-stroke epilepsy. Although this phenomenon has been described in recent literature, we report not only the highest initial ammonia level to date, 549 µmol/L, but we also document serial trends of the ammonia levels at multiple admissions for the same patient for the management of breakthrough seizures. Interestingly enough, persistence of the elevation of the ammonia levels was accompanied by no other significant metabolic derangements, unlike reported in similar cases. Of prior studies, high ammonia levels have been reported in the context of alcohol-induced seizures, with resolution of ammonia levels within eight hours. Here, we highlight the importance of medication compliance, as well as the need for serial ammonia levels for improving patient outcomes, with the knowledge that ammonia accumulation leads to potential irreversible neurotoxicity. Additionally, we completed a systematic literature review on data pertaining to the risk factors associated with hyperammonemia following unprovoked convulsive seizures in an effort to analyze our case in the context of the existing literature. Our objective is to ultimately understand the utility of serial ammonia levels for unprovoked convulsive seizures in the context of the patient's initial presentation, and whether treatment of these episodes of hyperammonemia can significantly alter outcomes.

Keywords: convulsive seizures; hyperammonemia; metabolism; neurophysiology.