Alpha-methyl-L-tryptophan PET detects epileptogenic cortex in children with intractable epilepsy
C Juhász1, D C Chugani, O Muzik
1Department of Pediatrics, Children's Hospital of Michigan, Detroit Medical Center, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Insights
Alpha-[11C]methyl-L-tryptophan (AMT) PET scans show higher specificity for identifying the seizure onset lobe in children with neocortical epilepsy. This PET tracer aids in localizing epileptogenic zones, especially when MRI and FDG PET are inconclusive.
Area of Science:
- Neuroimaging
- Epileptology
- Nuclear Medicine
Background:
- Alpha-[11C]methyl-L-tryptophan (AMT) PET shows selective uptake in epileptogenic tubers in children with tuberous sclerosis.
- This tracer aids in differentiating between epileptogenic and nonepileptogenic tubers during the interictal state.
Purpose of the Study:
- To determine if increased AMT uptake in children without tuberous sclerosis complex indicates the epileptogenic zone.
- To compare the effectiveness of AMT PET and 2-deoxy-2[18F]fluoro-D-glucose (FDG) PET in localizing epileptogenic cortical regions.
Main Methods:
- 27 children with intractable neocortical epilepsy underwent evaluation for resective surgery.
- Areas of increased AMT and decreased FDG uptake were objectively marked using custom software.
- PET findings were correlated with EEG, histology, and surgical outcomes.
Main Results:
- Focal cortical increases in AMT uptake were observed in 15 patients.
- AMT PET demonstrated lower sensitivity (39%) but higher specificity (100%) for seizure onset compared to FDG PET (sensitivity 73.2%, specificity 62.7%).
- Increased AMT uptake regions were smaller than FDG hypometabolic areas and associated with cortical developmental malformations.
Conclusions:
- Focal AMT uptake increases are less sensitive but more specific for the seizure onset lobe than FDG PET hypometabolism.
- AMT PET can aid in subdural electrode placement when MRI and FDG PET are insufficient.
- Regions adjacent to increased AMT uptake warrant careful evaluation with intracranial EEG due to high epileptogenicity.
Background:
In children with tuberous sclerosis, the PET tracer alpha[11C]methyl-L-tryptophan (AMT) has been shown to be selectively taken up by epileptogenic tubers, thus allowing differentiation from nonepileptogenic tubers in the interictal state.
Objective:
To determine whether cortical areas showing increased AMT uptake in children without tuberous sclerosis complex with intractable neocortical epilepsy indicate the epileptogenic zone, and to assess the relative contributions of AMT and 2-deoxy-2[18F]fluoro-D-glucose (FDG) PET abnormalities to the localization of epileptogenic cortical regions.
Methods:
Areas of increased AMT and decreased FDG uptake were marked objectively as regions with abnormal asymmetry using an in-house written software in 27 children who underwent comprehensive evaluation for resective epilepsy surgery. The marked PET abnormalities were compared to the locations of scalp and subdural EEG epileptiform abnormalities, as well as histology and surgical outcome.
Results:
Focal cortical increases of AMT uptake were found in 15 patients. The lobar sensitivity (39.0%) of AMT PET for seizure onset was lower, but its specificity (100%) was higher (p < 0.0001) than that of hypometabolism on FDG PET (sensitivity 73.2%, specificity 62.7%). AMT PET abnormalities were smaller than corresponding FDG PET hypometabolic regions (p = 0.002), and increased AMT uptake occurred in two patients with nonlocalizing FDG PET. Histologically verified cortical developmental malformations were associated with increased AMT uptake (p = 0.044). Subdural electrodes adjacent to the area of increased AMT uptake were most often involved in seizure onset.
Conclusions:
Focal increase of cortical AMT uptake in children is less sensitive but more specific for the lobe of seizure onset than corresponding FDG PET hypometabolism, and it is often associated with epileptogenic cortical developmental malformations. AMT PET can assist placement of subdural electrodes even when MRI and FDG PET fail to provide adequate localizing information. Cortical areas adjacent to increased AMT uptake should be carefully addressed by intracranial EEG because these regions often show a high degree of epileptogenicity.
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