Semiological characteristics and clinical application value of bilateral asymmetrical tonic seizures

Abstract

Objective To illustrate the semiological characteristics of the three sub-types within the broad bilateral asymmetric tonic seizures (BATS), summarize their predictive values on lateralization and localization of seizure onset zone (SOZ), and analyze the difference between BATS and asymmetrical tonic limb posturing (ATLP). Methods A retrospective review of 385 patients who underwent stereotactic electrode implantation in the Sanbo Brain Hospital, Capital Medical University from September 2011 to May 2018 was performed. As long as there was a clinical epileptic seizure in the presence of BATS or ATLP, the patients were classified into the corresponding groups. Postoperative prognosis was assessed using Engel′s grading criteria for a follow-up of no less than six months. Seizure descriptions were based on the classification of epileptic seizures introduced by Luders, which used arrows to connect the symptoms in chronological order. Results There was no statistically significant difference between the classic BATS and bilateral proximal tonic seizure in terms of whether it could be an independent seizure, as the onset and end of the seizure, with version and generalized tonic-clonic seizure (P>0.05). Compared with the ATLP, except for whether it could be an independent seizure (P=1.000) and onset before versive seizure (P=0.068), the BATS showed significantly different semiological features (P<0.05). The classic BATS and secondary motor area epilepsy had a 100.0% predictive accuracy on the lateralization of SOZ. In the patients with broad BATS, the SOZ distribution was more extensive, but it was rare in the orbitofrontal gyrus, frontal pole and mesial temporal lobe. Compared with the bilateral proximal tonic seizures from the other regions, those originated from supplementary somatosensory motor area and its adjacent areas were rare and showed no statistically significant difference (0/8 vs 40.0% (18/45), χ2=3.226, P=0.072) but a low trend. The predictive value of BATS on lateralization of SOZ was higher than that of ATLP (84.9% (45/53) vs 57.1% (24/42), χ2=9.086, P=0.003), and BATS was less originated from temporal lobe than ATLP (3.8% (2/53) vs 23.8% (10/42), χ2=8.523, P=0.004). Conclusion Different from ATLP, the broad BATS are characterized by tonic proximal upper limb posturing, and have a higher predictive value on lateralization and localization of SOZ. Key words: Epilepsy, tonic-clonic; Bilateral asymmetrical tonic seizures; Asymmetric tonic limb posturing; Electroencephalography