Arise from mesial and lateral temporal regions
The distinction between medial and lateral is important as mesial temporal lobe seizures will be abolished after standard temporal lobectomy or selective amygdalohippocampectomy, while lateral temporal lobe seizures will often require invasive video-EEG monitoring in order to map eloquent cortex and tailor a surgical resection.
Clinical features supporting mesial temporal lobe epilepsy = early age of onset, history of complex febrile seizures, congenital brain malformations, CNS infections, tumors, head trauma, perinatal injury, stuttering course of seizure control, and typically with well-controlled seizures in early childhood but re-emergence of refractory epilepsy in adolescence or early adulthood and frequent or rare secondarily generalized seizures
Clinical seizures favoring lateral temporal lobe epilepsy = later age of onset, absence of early risk factors, absence of hippocampal atrophy, and more commonly negative structural or functional brain imaging
Mesial temporal lobe seizures semiology = often have an aura (rising epigastric discomfort or inappropriate fear or olfactory feeling and/or autonomic signs like pallor, flushing, mydriasis, irregular respiratory or respiratory arrest, abdominal borborygmi, and eructation). These seizures often exhibit contralateral dystonic posturing of the hands (and ipsilateral hand automatisms), preserved ictal language if the focus is in non-dominant temporal lobe, ictal speech arrest if the focus is in dominant temporal lobe, posticttal nose wiping with ipsilateral hand, ictal vomiting or retching behavior, and head version in transition to secondary generalization.
On EEG, mesial tempora lobe seizures are often associated with a rhythmic theta-range ictal rhythm on scalp EEG. Typically, temporal rhythmic activity of <5 Hz frequency is followed wi 30s by 5-7 Hz sphenoidal maximum theta activity. At times, sudden generalized or lateralized suppression or attenuation is also seen. Interictal EEG abnormalities consistently of frequent spike or sharp waves predominantly in the inferomesial (sphenoidal electrodes) and anterior temporal regions.
Lateral temporal lobe seizures etiology = less common than mesial temporal lobe seizures, may be associated an aura of vertigo or with auditory or visual hallucinations. These seizures often evolve early to unilateral clonic activity and early head turn.
On scalp EEG, lateral temporal lobe seizures have a high incidence of repetitive epileptiform discharges at ictal onset. Also if present, a transitional shop wave at ictal onset favors a neocortical>hippocampal seizure onset. Neocortical seizures often start with higher frequency activity (alpha or beta range) on scalp EEG but may also be associated with irregular polymorphic 2-5 Hz lateralized activity. Interictal EEG abnormalities in neocortical temporal epilepsy may be absent or consist of occasional spikes or sharp waves predominant in the anterior or mid-temporal regions.
Features that do not point to mesial vs lateral temporal onsets: ictal emeticus, ictal urinary urge, ictal spitting, which often to the non dominant temporal lobe, and piloerection, which localizes to the dominant temporal lobe
