Electroclinical phenotypes and outcomes in TBC1D24-related epilepsy

TBC1D24 is a newly recognized gene in which variations lead to variable clinical phenotypes including drug-resistant epilepsy. We report four patients with novel variants of TBC1D24 demonstrating drug-resistant focal epilepsy, developmental delays, and head growth deceleration. All patients had seizure semiologies consisting of prolonged, unilateral, focal clonic activity of the arm, leg or face, in addition to generalized clonic or myoclonic seizures. Ictal EEG characteristics included epilepsia partialis continua, epilepsy of infancy with migrating focal seizures, and other focal seizures with indiscrete interictal-ictal transitions. Two seemingly unrelated Navajo patients with identical variations experienced super-refractory status epilepticus at 9 months of age, with one achieving resolution with ketogenic diet therapy. Our series suggests that TBC1D24-related epilepsy can manifest with hypotonia, developmental delays, and a variety of focal-onset seizures prone to electroclinical dissociation.