What is the expected EEG pattern in a patient experiencing a tonic-clonic seizure?

The expected EEG pattern during a tonic-clonic seizure is characterized by high voltage fast activity. This corresponds with the generalized, rapid electrical discharges occurring in the brain throughout the seizure, which involves both the tonic phase (stiffening of the body) and the clonic phase (rhythmic jerking movements). During this type of seizure, the EEG typically shows a mixture of high-amplitude spikes and fast waves, reflecting the chaotic and intense neuronal firing associated with the seizure activity.

The presence of high voltage fast activity represents the abnormal synchronization of large groups of neurons, which is a hallmark of seizure activity. This pattern can often be seen in the frontal or generalized leads of the EEG during the seizure. Recognizing this distinct pattern is crucial for diagnosis and differentiation from other neurological events.

Other patterns listed do not represent the activity associated with a tonic-clonic seizure. Interictal spikes are often seen in individuals with epilepsy but occur during periods between seizures rather than during an active seizure. Continuous theta activity is more commonly associated with different types of brain states and is not characteristic of tonic-clonic seizures. An empty state on an EEG indicates no activity and does not correlate with the dynamic electrical discharges occurring during a tonic-clonic seizure.