Ictal vocalizations occur more often in temporal lobe epilepsy with dominant (left-sided) epileptogenic zone

To investigate the lateralization value of ictal vocalizations in temporal lobe epilepsy (TLE).

We reviewed video-recordings of 97 patients who had undergone presurgical evaluation programs with video-EEG (electroencephalography)-recorded complex partial seizures (CPS) and high-resolution magnetic resonance imaging (MRI). All patients had surgery due to TLE and became seizure-free. In 57 patients, determination of speech dominance was necessary by using Wada tests or functional MRI (fMRI). To reevaluate the archived seizures, we reviewed one to three consecutively recorded CPS of each patient. Altogether 223 archived seizures were analyzed. Ictal vocalization was considered to be present in a particular patient if it occurred in at least one of the recorded seizures.

Ictal vocalizations occurred in 22 patients. They occurred in 37% of left-sided and in 11% of right-sided patients with TLE (p = 0.003). In patients with determined speech lateralization, ictal vocalizations occurred in 37% of the dominant and in 14% in patients with nondominant epileptogenic zone (p = 0.04). In patients with ictal vocalizations, epilepsy began at age 8.7 +/- 6, whereas in the remaining patients, epilepsy started at age 14.0 +/- 9 (p = 0.017). Logistic regression showed that both hemispheric dominance and age at onset were independently associated with pure ictal vocalization (PIV).

Ictal vocalization is a frequent phenomenon, occurring in 23% of patients with TLE. It is more often associated with left-sided and early onset TLE. Our results may improve the lateralization of the epileptogenic zone and suggest that nonspeech vocalizations in humans are related to the dominant (left-sided) hemisphere. Our study is a further argument that there are different subtypes of TLE depending on the age at onset.