Ictal unilateral blinking is an unreliable lateralizing sign in tuberous sclerosis complex

• Unilateral blinking during focal seizures suggests an ipsilateral focus.
• Unilateral blinking is not uncommon in focal seizures in children with TSC.
• In TSC, ictal unilateral blinking may be ipsilateral or contralateral to the focus.
• In TSC, unilateral blinking early in seizures is more often contralateral.
• Seizure propagation and different mechanisms may cause the variable lateralization.

ObjectiveIctal unilateral blinking is an uncommon but reportedly reliable lateralizing sign, indicating an ipsilateral seizure focus. We aimed to determine its lateralizing utility in patients with tuberous sclerosis complex (TSC).MethodsWe reviewed the video-EEGs of 92 children with TSC and drug-resistant epilepsy. Eleven (12%) had seizures with unilateral blinking, of which 10 underwent epilepsy surgery. Lateralization of seizures was inferred from other semiology, ictal scalp EEG and outcome following tuberectomy.ResultsSeizures manifesting with unilateral blinking were focal motor in four patients, focal motor evolving into epileptic spasms in six, and epileptic spasms with focal features in one. Associated unilateral facial contraction was seen in five patients and arm jerking in four. Lateralized scalp ictal rhythms were seen in seven patients. Following tuberectomies, seven patients are seizure free and two had >90% reduction. Overall lateralization of seizures with unilateral blinking was contralateral in six patients and ipsilateral in four. When unilateral blinking was early in seizures, overall lateralization was more often contralateral (6/7 patients, PPV 85%).SignificanceIctal unilateral blinking is not infrequent but unreliable in lateralizing seizures in TSC. Unrecognized seizure propagation to contralateral symptomatogenic regions and potentially different mechanisms may account for the variable lateralization.