[1744] Pathologic Findings in Radiographic Nonlesional Pharmacoresistent Epilepsy

Angela R Shih, Richard A Prayson. Cleveland Clinic, Cleveland, OH

Background: A subset of patients with pharmacoresistent epilepsy have no clear lesion on magnetic resonance imaging (MRI) i.e. nonlesional. There are limited descriptions of the histologic findings associated with such cases. This study retrospectively reviews a series of nonlesional patients to examine the pathology observed in these cases.
Design: 94 patients (74 adults and 20 pediatric) with chronic epilepsy and nonlesional imaging per standardized epilepsy imaging protocol from 2002-2011 were identified and histology slides from tissue resections were reviewed to document pathologic findings. Focal cortical dysplasia (FCD) was classified according to Palmini et al (Neurology 2004;62(Suppl 3):S2-8) and ILAE (Epilepsia 2010;51:676-685) criteria.
Results: Surgery included 67 temporal lobe resections, 26 extratemporal resections and 1 multilobar resection. Of the specimens received, subtotal submission occurred in 57.4% (N=54) and total submission occurred in 42.6% (N=40). Collectively, the most common findings were FCD (45%; N=42), gliosis (38%, N=36), hippocampal sclerosis (HS) (12%; N=11), and absent pathologic abnormalities (7%; N=7). Dual pathology (FCD and HS) was seen in 2 of these FCD cases. Among the 42 cases of FCD, most (71.4%; N=30) were Palmini et al type IA lesions with less frequently observed patterns being type IB (21.4%; N=9) and type IIB (7.1%; N=3). Corresponding ILAE classification for FCD included Ic (67%; N=28), type Ib (21%; N=9), type IIb (7%; N=3) and type IIIa (5%; N=2). The frequency of observed FCD was greater among the extratemporal lobe cases (69%) versus temporal lobe cases (34%). Adult and pediatric groups had comparable proportions of FCD cases. Of the cases with either isolated gliosis or no pathologic findings, 44% (N=18) were subtotal submissions and 56% (N=23) were total submissions.
Conclusions: FCD type I and HS are among the most common observed pathologic abnormalities in nonlesional chronic epilepsy cases. Slightly less than half of nonlesional cases show nonspecific gliosis or no obvious light microscopic abnormality; this may be a bit high due to incomplete histologic sampling of resected tissues in some cases.
Category: Neuropathology

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 254, Wednesday Afternoon


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