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Interictal 99Tc(m) HMPAO SPECT and 1H MRS in children with temporal lobe epilepsy
J H Cross1, I Gordon, A Connelly
1Neurosciences Unit, Institute of Child Health, London, England.
Insights
Interictal technetium-99m hexamethylpropyleneamine oxime (HMPAO) SPECT reveals hypoperfusion in temporal lobe epilepsy. Proton magnetic resonance spectroscopy (1H MRS) can clarify findings, especially with bilateral damage.
Area of Science:
- Neurology
- Nuclear Medicine
- Neuroimaging
Background:
- Intractable temporal lobe epilepsy (TLE) often presents with focal hypoperfusion on interictal SPECT.
- Understanding the pathological basis of these findings is crucial for accurate localization.
Purpose of the Study:
- To elucidate the pathological basis of focal hypoperfusion in interictal SPECT in TLE.
- To determine why SPECT may be misleading in seizure focus localization/lateralization.
Main Methods:
- 14 children with intractable TLE underwent interictal 99mTc HMPAO SPECT and 1H MRS of mesial temporal regions.
- Patients without foreign tissue lesions were included.
Main Results:
- 71% of children showed ipsilateral temporal lobe hypoperfusion on SPECT; 1H MRS lateralized correctly in 80% of these.
- 4 children had no anterior temporal perfusion asymmetry; 1H MRS showed bilateral abnormalities in 3.
- Repeated scans in 3 children showed consistent findings between SPECT and 1H MRS over time.
Conclusions:
- 1H MRS abnormalities correlate with interictal SPECT findings, aiding understanding of SPECT abnormalities.
- Bilateral temporal lobe damage can lead to absent perfusion asymmetry on interictal SPECT, potentially misdirecting localization.
Purpose:
To understand the pathological basis of focal hypoperfusion seen on interictal 99Tc(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 99Tc(m) HMPAO SPECT and proton magnetic resonance spectroscopy (1H 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; 1H 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 1H 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 1H 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.