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High signal intensity on T2-weighted MRI correlates with hypoperfusion in temporal lobe epilepsy
P Ryvlin1, L Garcia-Larrea, B Philippon
1EEG Department, Neurological Hospital, Lyon, France.
Abstract:
Single-photon emission computed tomography (SPECT) and [99mTc]HMPAO were used to assess the functional significance of nonspecific magnetic resonance imaging (MRI) abnormalities observed in patients with temporal lobe epilepsy and no focal lesion on CT scan. We studied 18 patients whose MRI was normal or showed high signal intensity on T2-weighted images (T2WIs) at the site of the EEG focus in 11 and 7 cases, respectively. EEG was monitored during regional cerebral blood flow (rCBF) study. Lateralized hypoperfusion was present in 7 of 17 interictal (41%) and in one postictal cases; it was located in the temporal lobe on the side of the EEG focus in all, and was significantly more frequent in patients with high signal intensity on T2WI (86%) than in patients with a normal MRI (18%). The degree of temporal perfusion asymmetry measured in each individual was higher in patients whose MRI was abnormal.
Insights
Single-photon emission computed tomography (SPECT) using [99mTc]HMPAO helps identify functional significance of MRI abnormalities in temporal lobe epilepsy. Abnormalities on T2-weighted images correlate with hypoperfusion near the EEG focus.
Area of Science:
- Neurology
- Nuclear Medicine
- Radiology
Background:
- Temporal lobe epilepsy (TLE) diagnosis can be challenging with non-specific MRI findings.
- Assessing functional significance of MRI abnormalities is crucial for understanding epilepsy.
- Computed tomography (CT) scans may not reveal focal lesions in some TLE cases.
Purpose of the Study:
- To evaluate the functional significance of non-specific MRI abnormalities in TLE using SPECT.
- To correlate regional cerebral blood flow (rCBF) with EEG findings and MRI characteristics.
- To determine if SPECT can identify hypoperfusion associated with EEG foci in TLE patients with normal or non-specific MRI.
Main Methods:
- SPECT with [99mTc]HMPAO was performed in 18 patients with TLE and non-specific MRI.
- Patients underwent EEG monitoring during the regional cerebral blood flow (rCBF) study.
- MRI findings were categorized as normal or showing high signal intensity on T2-weighted images (T2WIs) at the EEG focus site.
Main Results:
- Lateralized temporal hypoperfusion was observed in 41% of interictal SPECT scans.
- Hypoperfusion was significantly more frequent in patients with high T2WI signal intensity (86%) compared to normal MRI (18%).
- Temporal perfusion asymmetry was greater in patients with abnormal MRI compared to those with normal MRI.
Conclusions:
- SPECT using [99mTc]HMPAO is valuable for assessing functional significance of non-specific MRI findings in TLE.
- High T2WI signal intensity on MRI is associated with a higher likelihood of interictal hypoperfusion.
- SPECT can help lateralize the epileptic focus in TLE patients where MRI findings are ambiguous.