Somatosensory auras in focal epilepsy: A clinical, video EEG and MRI study

PURPOSE To determine the clinical characteristics of somatosensory auras (SSA) and analyse features of seizure semiology predictive for localization in focal neocortical and limbic epilepsy. METHODS This study analyses the clinical, video-EEG and MRI imaging features of 75 consecutive patients with focal epilepsy who described somatosensory auras at seizure onset to determine the frequency and localising value of SSAs in different types of focal epilepsy. Sensory characteristics, somatotopic distribution, evolution of the auras and subsequent ictal features in relation to MRI and EEG findings were analysed. RESULTS The incidence of SSAs in 600 patients with focal epilepsy was 12%. Seventy-five patients were studied further: 77% reported tingling. Pain, thermal changes and a sense of movement or pulling were also reported. Distal unilateral auras in the hand and arm (46%) were most frequent and associated with a contralateral centroparietal focus. Contralateral auras were reported in 62% of lesional cases, focal cortical dysplasia was the commonest pathology in operated cases. Bilateral auras were associated with more diffuse pathologies or parasagittal foci. Evolution was centrifugal, somatotopic and usually unilaterally confined. Subsequent motor semiology was postural tonic, unilateral clonic, psychomotor or secondary generalized. CONCLUSION SSA are highly correlated with centroparietal epilepsy but may occur in temporal lobe, mesial frontal and multifocal epilepsy. A lesional etiology including discrete dysplasias, tumours, ischemic and postencephalitic gliosis is likely.