title: Clinical and histopathologic correlates of 11C-alpha-methyl-L-tryptophan (AMT) PET abnormalities in children with intractable epilepsy.
abstract: OBJECTIVE
  Interictal increase of (11) C-alpha-methyl-l-tryptophan (AMT) on positron emission tomography (PET) can be seen in cortical epileptic foci, and is particularly common in cortical developmental malformations. Therefore, in the present study, we evaluated the clinical and histopathologic correlates of AMT-PET abnormalities in children with intractable epilepsy undergoing resective surgery.
  
  
  METHODS
  Thirty children (mean age: 6.7 ± 3.2 years) were included in this study. All patients received AMT-PET as part of their presurgical evaluation and subsequently underwent epilepsy surgery. Magnetic resonance imaging (MRI) scans were normal in 15, showed nonspecific changes in 8, and suggested malformations of cortical development (MCDs) in nine children. Asymmetry indices (AIs) were calculated to determine increased AMT uptake.
  
  
  RESULTS
  Histopathology revealed MCDs in 16 (53%) children, including 12 with cortical dysplasia (CD) [mild MCD = 3; CD type IA = 2; CD type IIA = 2 and CD type IIB (severe CD with balloon cells) = 5]. Polymicrogyria and heterotopias (P&Hs) were seen in three cases and subependymal heterotopias (SEHs) in one child. The remaining 14 cases showed normal histopathology with varying degrees of gliosis. Increased AMT uptake was found in all five with CD type IIB, and all three with P&H, but in none with mild MCD and types IA-IIA CD or SEH. Whereas all five children with CD IIB and two with P&H had excellent surgical outcome (class I); children with milder CD or SEH had variable surgical outcome. The 14 patients with normal histopathology included seven patients with focally increased and seven with normal AMT uptake. Although patients with normal pathology and normal AMT-PET had better surgical outcome (class I = 5; II = 2), those with normal pathology, normal MRI, but abnormal AMT-PET had poor surgical outcome (class III = 4; IV = 3).
  
  
  CONCLUSIONS
  Increased AMT uptake in children with CD may predict type IIB dysplasia (with balloon cells) and good surgical outcome. Histopathologic similarities between CD type IIB and epileptogenic cortical tubers may imply a common role of the inflammatory kynurenine pathway of tryptophan metabolism in these lesions. In children with normal histopathology, there is a subgroup with increased AMT uptake and poor surgical outcome.
authors.affiliation: Department of Pediatrics, Children's Hospital of Michigan, Detroit Medical Center, Wayne State University School of Medicine, Detroit, Michigan 48201, USA. hchugani@pet.wayne.edu
authors.forename: Harry T
authors.initials: HT
authors.lastname: Chugani
authors.forename: Ajay
authors.initials: A
authors.lastname: Kumar
authors.forename: William
authors.initials: W
authors.lastname: Kupsky
authors.forename: Eishi
authors.initials: E
authors.lastname: Asano
authors.forename: Sandeep
authors.initials: S
authors.lastname: Sood
authors.forename: Csaba
authors.initials: C
authors.lastname: Juhász
mesh_terms: D001931:Brain Mapping; D002250:Carbon Radioisotopes; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010296:Parietal Lobe / Q000000981:diagnostic imaging / Q000473:pathology; D049268:Positron-Emission Tomography; D013223:Statistics as Topic; D014364:Tryptophan / Q000031:analogs & derivatives*
chemical_list: D002250:Carbon Radioisotopes; C020774:alpha-methyltryptophan; D014364:Tryptophan