What is the most common ictal correlate of tonic seizures?

The most common ictal correlate of tonic seizures is characterized by paroxysmal fast activity. Tonic seizures are typically associated with a sudden increase in muscle tone, often presenting as stiffening or rigidity. The underlying EEG findings during these seizures primarily show bursts of fast, rhythmic activities, which reflect the simultaneous discharge of a large number of neurons.

Paroxysmal fast activity indicates that there is a heightened state of neuronal excitability occurring during the seizure, which aligns with the nature of tonic seizures where sustained muscle activity is present. This fast activity might appear as beta or gamma rhythms on the EEG, showcasing an elevation in frequency that corresponds with the clinical manifestations of the seizure.

In contrast, paroxysmal slow activity and paroxysmal mixed activity do not typically correlate with the tonic seizure pattern, as these are more reflective of different seizure types or underlying pathology. Paroxysmal sharp waves might indicate focal irritation or specific types of seizures, but they are not the primary feature associated with tonic seizures. Thus, the dominance of fast activity in the EEG findings is a key indicator that supports the identification of tonic seizures in electroencephalographic recordings.