Abstracts

Temporal lobe functional abnormalities involving hippocampus/ amygdale (HA) areas are implicated in the pathogenesis of epilepsy and of pervasive developmental disorders (PDD). MR Spectroscopy (MRS) is considered a research method that is sensitive to brain disorders abnormalities, however, generally not specific. Single voxel proton MRS of HA areas in children with epilepsy and in children with PDD without epilepsy, that had an anatomically normal MRI, were examined and compared to children with typical development.
Ten PDD subjects (5-16 yrs) without epilepsy, four epilepsy subjects (1-14 y) all with difficult to control epilepsy and six control subjects (6-15 yrs) were examined. Both the PDD and the controls were free of medication and the epilepsy subjects were on different combinations of medications.
The MR data were acquired using a 1.5T scanner. T[sub]1[/sub]- and T[sub]2[/sub]-weighted images were obtained covering the brain in all three orthogonal directions. T[sub]2[/sub]-weighted coronal images were used as scouts for single-voxel ¹H MRS data acquisition with a PRESS sequence, TE = 40 ms, TR = 2000 ms, and 128 scan averages. The proton spectra were collected from bilateral HA (left- LHA and right- RHA) (1.6 cm³) regions. According to anatomic, PET, and functional MRI studies, these areas exhibit abnormalities in both PDD and epilepsy.
Resonance peaks of NAA, total creatine (Cr), choline-containing compounds (Cho), glutamine+glutamate (glx) and myo-inositol (mI) were identified. Peak area ratios over Cr resonance were calculated and used as measures of metabolite ratios.
Anatomic MRI was normal in all subjects and controls. In all patients with epilepsy MRS showed increased Glx/Cr ratio in at least one voxel (2.4 [plusmn] 1.77 compared to 0.35 [plusmn] 0.5 in controls). Cho/cr ratio were elevated three of the four patients and NAA/Cr ratio was low in one voxel from two patients. Two of the patients had concomitant elevated glutamine levels in plasma and in CSF. In the PDD group, NAA/Cr was significantly decreased bilaterally, while mI/Cr was significantly increased compared to controls. Cho/Cr was significantly elevated in the LHA (results in table 1).
The findings of decreased levels of NAA in the HA area in both study groups are consistent with neuronal loss/dysfunction, or the existence of immature neurons. Glutamate concentrations are higher in epileptic hippocampi. The elevation of mI and Cho levels in PDD suggests gliosis in those brain regions. This preliminary study shows that with the noninvasive approach, ¹H MRS can provide neurochemical information that is specific to the disorder[table1]