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To analyze seizure-like motor phenomena immediately occurring after concussion (concussive convulsions).

Twenty-five videos of concussive convulsions were obtained from YouTube as a result of numerous sports-related search terms. The videos were analyzed by four independent observers, documenting observations of the casualty, the head injury, motor symptoms of the concussive convulsions, the postictal period, and the outcome.

Immediate responses included the fencing response, bear hug position, and bilateral leg extension. Fencing response was the most common. The side of the hit (p = 0.039) and the head turning (p = 0.0002) was ipsilateral to the extended arm. There was a tendency that if the blow had only a vertical component, the bear hug position appeared more frequently (p = 0.12). The motor symptom that appeared with latency of 6 ± 3 s was clonus, sometimes superimposed with tonic motor phenomena. Clonus was focal, focally evolving bilateral or bilateral, with a duration of 27 ± 19 s (5–72 s). Where lateralization of clonus could be determined, the side of clonus and the side of hit were contralateral (p = 0.039).

Concussive convulsions consist of two phases. The short-latency first phase encompasses motor phenomena resembling neonatal reflexes and may be of brainstem origin. The long-latency second phase consists of clonus. We hypothesize that the motor symptoms of the long-latency phase are attributed to cortical structures; however, they are probably not epileptic in origin but rather a result of a transient cortical neuronal disturbance induced by mechanical forces.