Abstracts

Rationale: Neuronal hyperexcitability is a basic pathophysiology of epilepsy, and also regulated by glial cells. Pathologic studies using surgical specimens frequently report cortical and subcortical gliosis irrespective of etiology. So far, the subjects of surgical pathological studies on gliosis mostly deal with adults or elder children with focal epilepsy. Age-related epileptic encephalopathy, such as infantile spasms or Lennox-Gastaut (IS / LGS), is hardly included in those studies. In this study, the relationship between the presence or absence of age-specificity in maturation of astrogliosis and type of epilepsy such as infantile IS/LGS and juvenile/adult focal epilepsy was investigated. Methods: The study was approved by the institutional review board. The subjects were 10 patients with drug resistant epilepsy who underwent focal resection or hemispheric/multilobar surgery. In order to avoid the modifying effects of the pathological lesions, cases with clear lesions on MRI, such as FCD, tuberous sclerosis, tumors, post-encephalitis changes were excluded. The subjects were classified into IS/LGS group (n = 6) and focal onset epilepsy group (n = 4) based on preoperative diagnosis of epilepsy. Surgically resected cortical specimens were retrospectively observed using immunohistochemistry with glial fibrillary acidic protein (GFAP) antibody and excitatory amino acid transporter 2 (EAAT2) antibody in pediatric/adult patients with refractory epilepsy. Results: In patients with juvenile/adults focal onset epilepsy, marked cortical gliosis was noted, whereas it was absent in patients with infantile-onset IS/LGS. The expression of the EAAT2, which is one of the astrocytic functions, was normally maintained regardless of the epilepsy type or the age of onset. Conclusions: In age-specific epileptic encephalopathy such as IS/LGS, lack of cortical gliosis is a characteristic histological feature, suggesting that there may be a different pathological condition than other epilepsy. Exposure to hyperexcitation in infancy may inhibit the development of astrocytes; i.e., functions involved in GFAP synthesis. and astrocytes may remain in an immature state. Funding: The Japan Epilepsy Research Foundation (2016-2018)