Infantile-onset mesial temporal lobe epilepsy with severe cognitive regression

Infantile-onset mesial temporal lobe epilepsy with severe cognitive regression is an extremely rare epileptic syndrome characterized by seizures originating from the mesial (inner) structures of the temporal lobe, with onset during infancy (typically within the first two years of life). Unlike the more common forms of mesial temporal lobe epilepsy seen in older children and adults, this infantile-onset variant is distinguished by its association with severe and progressive cognitive decline. The condition primarily affects the central nervous system, particularly the hippocampus and surrounding mesial temporal structures. Affected infants typically present with focal seizures that may include behavioral arrest, oral automatisms, and autonomic features. The seizures are often drug-resistant, meaning they respond poorly to standard antiepileptic medications. A hallmark feature of this condition is the severe cognitive regression that accompanies or follows seizure onset, leading to significant intellectual disability, language impairment, and loss of previously acquired developmental milestones. Brain MRI may reveal hippocampal sclerosis or signal abnormalities in the mesial temporal regions, and EEG typically shows temporal lobe epileptiform discharges. The treatment landscape remains challenging. Management primarily involves antiepileptic drug therapy, though seizures are frequently refractory to multiple medications. In select cases, epilepsy surgery (such as temporal lobectomy or selective amygdalohippocampectomy) may be considered to achieve seizure control, though cognitive outcomes remain variable. Supportive therapies including speech therapy, occupational therapy, and developmental interventions are important components of care. The underlying etiology in many cases remains unclear, though genetic factors and early structural abnormalities of the temporal lobe are suspected contributors.

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