Clinical Pearls & Morning Reports
The European Epilepsy Brain Bank (EEBB) was established in 2006 under the direction of the Framework Program of the European Union to standardize histopathological reporting of specimens obtained during epilepsy surgery and to survey epileptogenic brain lesions. The database includes 4944 men and 4579 women with surgically treated epilepsy who underwent surgery during the period from 1990 through 2014 in 36 specialized epilepsy surgery centers. Blumcke et al. examined specimens from the EEBB database, and recently published a report describing the histopathological diagnoses in this large database, to complement existing information on drug-resistant epilepsy and epilepsy surgery. A post hoc analysis of associations between histopathological diagnoses and the outcome of surgery was performed for a subset of the centers. Read the latest Original Article.
Q: What was the most common histopathological diagnosis identified among surgical specimens in the EEBB database?
A: Hippocampal sclerosis was the most common histopathological diagnosis; this condition was identified in 36.4% of all surgical specimens — 44.5% of those from adults and 15.0% of those from children. The temporal lobe was operated on in 71.9% of the patients in the overall study population, and hippocampal sclerosis was diagnosed in 54.4% of specimens obtained from this lobe. Overall, the rate of freedom from seizures 1 year after surgery was 61.4% among patients who had the diagnosis of hippocampal sclerosis.
Q: How common was a diagnosis of brain tumor among cases in the EEBB database?
A: Brain tumors were the second most common histopathological diagnosis, occurring in 23.6% of specimens, with ganglioglioma being the most frequent (found in 10.4% of all patients in the study population). A total of 82.5% of gangliogliomas were located in the temporal lobe. Dysembryoplastic neuroepithelial tumors were the second most frequent type of tumor (5.9% of patients); in 68.1% of cases, the tumor was located in the temporal lobe. One year after surgery, 68.4% of patients with tumors (79.9% of children and 63.5% of adults) were seizure-free.
A: Malformations of cortical development were found in 19.8% of specimens and were the third most frequent histopathological category; such malformations were identified in 39.3% of all specimens obtained from children. Subtypes of focal cortical dysplasia were the most common malformations of cortical development, accounting for 70.6% of cases. The onset of epilepsy in patients with malformations of cortical development was earlier than that among patients with other disease categories. Overall, 57.6% of patients with malformations of cortical development (59.9% of children and 54.6% of adults) were seizure-free 1 year after surgery.
A: In children and adults, 6.1% and 8.4%, respectively, of tissue samples had astrogliosis only and could not be categorized as having any conventional lesion type. This does not imply that the tissue was functionally normal, since 50.2% of patients with drug-resistant seizures before epilepsy surgery and unclassifiable tissue samples were seizure-free 12 months after surgery, which implicates the resected tissue in the genesis of the seizures. It is also possible that a molecular alteration that can decrease seizure threshold but is not apparent as an abnormality on light microscopy was an element involved in the conditions in this group of patients. Ambiguous histopathological findings may also result from the inconsistent nature of neurosurgical sampling.
Table 2. Summary of the 10 Most Common Histopathological Diagnoses among 9523 Patients Who Underwent Epilepsy Surgery.