Isolated idiopathic hypomagnesemia presenting as aphasia and seizures.

Isolated hypomagnesemia of the idiopathic form is a rare condition that is known to present as generalized motor seizures in children. This report describes a 4-year-old African-American male who presented with a predominant symptom of sudden onset aphasia and no clear initial motor seizure activity. An evaluation revealed an isolated and severe hypomagnesemia (initial serum magnesium levels <1.0 mg/dL) and inappropriate renal handling of magnesium (fractional excretion of magnesium >40% under conditions of hypomagnesemia). The child had subsequent generalized tonic-clonic seizures that were brought under control with valproic acid therapy and magnesium supplementation. Six months after the diagnosis, he had regained 50-60% of his speech and had no further staring spells or motor seizure activity after the initial episode. Isolated and idiopathic hypomagnesemia caused by defective renal reabsorption of magnesium is a rare familial condition with variable inheritance. Aphasia as the solitary presenting symptom has not been described before. The exact pathophysiology of hypomagnesemic aphasia and seizures is not known but may relate to disinhibition of specific types of glutamate receptors. In the present case, neuronal depolarization may have been localized to language areas in the temporal lobes.