Abstracts

RATIONALE: Positron emission tomography (PET) with 2-deoxy-2[¹⁸F]fluoro-D-glucose (FDG) can detect focal cortical abnormalities in children with cryptogenic infantile spasms, although many show bilateral, multifocal hypometabolism. Recently the new PET tracer [alpha][¹¹C]methyl-L-tryptophan (AMT) was reported to differentiate between epileptogenic and non-epileptogenic lesions in children with tuberous sclerosis. Increased uptake of AMT on PET occurs in epileptogenic cortical regions in 40-60% of patients with intractable partial epilepsy.In the present study AMT PET was applied to children with intractable infantile spasms not associated with tuberous sclerosis, in order to determine if this imaging modality can further identify the epileptic focus.
METHODS: Eighteen children (11 boys and 7 girls, age 9 months [ndash] 8 years, mean age 3.0 years; 15 with non-focal MRI and 3 with cortical developmental malformation) with intractable infantile spasms underwent AMT PET scans. Focal cortical areas of increased AMT uptake were recorded and compared to FDG PET and EEG findings.
RESULTS: Seven patients (39%) had a single focus of increased AMT uptake, and these children were significantly older (mean age: 4.4 years) than the remaining 11 without focal AMT PET abnormalities (mean age: 2.2 years; p=0.038). There was only one child (a 17 month old girl) below 2 years of age (out of 7) who had an AMT focus. Age at onset of spasms did not differ significantly between AMT positive and AMT negative patients (p=0.19). Of the 11 children whose EEGs revealed an epileptic focus, 4 showed increased AMT uptake, and these areas were concordant with the EEG findings. One of 2 children with lateralizing but non-localizing ictal EEG showed increased AMT uptake in the left temporal lobe, which was later verified as the site of seizure onset by intracranial EEG. Five patients had non-focal ictal EEG findings, and one of these showed increased AMT uptake in the right temporal lobe. FDG PET showed unilateral hypometabolism in 8 children (44.4%), and 3 of these had increased AMT uptake ipsilaterally involving a smaller area than the corresponding FDG abnormality. Of 10 patients with multifocal FDG PET hypometabolism, 4 showed a single focal area of increased AMT uptake. Seizure onset was identified by intracranial EEG monitoring in 3 cases, and it was always concordant with the location of the AMT PET findings.
CONCLUSIONS: AMT PET can reveal focal epileptogenic cortical regions in about 40% of children with intractable infantile spasms. This sensitivity of AMT PET appears to be similar to that in older patients with partial epilepsy, especially in children above 2 years of age. Focal increase of AMT uptake can occur in children with infantile spasms whose FDG PET are non-localizing, and these AMT abnormalities are concordant with ictal intracranial EEG findings. Thus, FDG and AMT PET can be used as complementary imaging methods to identify focal epileptogenic cortical regions for surgical resection in infantile spasms.
[Supported by: NS 34488, NS/RR 38324]; (Disclosure: Grant - NS 34488, NS/RR 38324)