Interictal Tc-99(m) HMPAO SPECT and H-1 MRS in children with temporal lobe epilepsy

Purpose: To understand the pathological basis of focal hypoperfusion seen on interictal Tc-99(m) hexamethylpropyleneamine oxime (HMPAO) single-photon-emission computed tomography (SPECT) in intractable temporal lobe epilepsy, and to determine why the technique may be misleading in the localization and lateralization of the seizure focus in some cases. Methods: Interictal Tc-99(m) HMPAO SPECT and proton magnetic resonance spectroscopy (H-1 MRS) of the mesial temporal regions were performed in 14 children with intractable temporal lobe epilepsy not caused by a foreign tissue lesion. Results: Hypoperfusion of one temporal lobe ipsilateral to the seizure focus was demonstrated in 10 (71%) Of the children; H-1 MRS correctly lateralised in eight of these 10. No asymmetry of perfusion of the anterior temporal regions was seen in the remaining four children; on H-1 MRS, three of these were bilaterally abnormal but nonlateralising. Repeated SPECT and 1H MRS in three children demonstrated changes over time, the findings from the two techniques being consistent with each other on both the initial and the repeated scans. Conclusions: Abnormalities demonstrated by H-1 MRS correlate well with those seen on interictal SPECT and can help to understand the pathologic basis of these SPECT abnormalities. Furthermore, the presence of bilateral damage can result in an absence of perfusion asymmetry on interictal SPECT.