Is the left hemisphere more prone to epilepsy and poor prognosis than the right hemisphere?

The central nervous system is known to have asymmetric immune system modulation. Thus far, no clinical study has examined asymmetric immune modulation between hemispheres in focal epilepsy patients. We aimed to compare the prognosis of epilepsy patients lateralized to the right hemisphere with epilepsy patients lateralized to the left hemisphere using clinic and demographic data. Ninety-nine patients with focal epilepsy with all seizures originating in only one hemisphere, between the ages of 18-and 86 years were included. We included patients with focal epilepsy whose seizures were lateralized to only one hemisphere. Age, gender, marital status, education, mental retardation, hand dominance, etiology, trauma, central nervous system infection, febrile convulsion, parental relationships, seizure onset age, seizure frequency (per month), systemic disease, and biochemical parameters were recorded. To evaluate lateralization, we used positron emission tomography (PET/CT), long-term video-electroencephalography (EEG), and magnetic resonance imaging (MRI) investigations. Thirty-seven patients (37.4%) patients were right-lateralized, whereas 62 patients (62.6%) were left-lateralized ( = 0.01). Seizures frequency seizures were higher in patients lateralized to the left hemisphere than in the right. ( = 0.001). In patients with epilepsy lateralized to the left hemisphere, epilepsy onset age was lower ( = 0.003), numbers of antiepileptic medicines were higher ( = 0.04), and epilepsy durations and longest seizure-free periods were longer ( = 0.001 and  = 0.04, respectively). We have shown that compared to the right hemisphere, the left hemisphere is far more prone to seizures and has a poorer prognosis.