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Functional significance of MRI defined mesial temporal sclerosis in temporal lobe epilepsy
E M Yacubian1, A Cukiert, P Carrilho
1Hospital das Clínicas, Faculdade de Medicina da Universidade de São Paulo FMUSP, Brasil.
Abstract:
The functional significance of MRI-defined mesial temporal sclerosis in temporal lobe epilepsy (TLE) is not completely established. In order to study the possible relationship between signals of mesial temporal sclerosis on MRI and interictal SPECT findings we selected 18 patients with complex partial seizures, unilateral temporal EEG focus and normal CT. The EEG focus was defined by the presence of interictal sharp waves and slow background on several scalp EEG obtained during many years of follow up in all patients and by ictal recordings with sphenoidal electrodes in 12 patients. Group I comprised patients (n = 11) in whom MRI showed mesial temporal sclerosis; group II patients (n = 7) had normal MRIs. All patients were submitted to interictal 99m-Tc HMPAO injections with concomitant EEG monitoring. Lateralized hypoperfusion ipsilateral to the EEG was found in 13 patients (72%). In all Group II and in 6 Group I patients a temporal hypoperfusion was found. This SPECT study showed a higher positivity rate in patients with normal MRI than previously reported. On the other hand, in all these group II patients a neocortical origin of epileptic focus was suspected on clinical or electroencephalographic basis. Positive SPECT findings may be at least as prevalent in neocortical as in mesiolimbic epilepsy.
Insights
Mesial temporal sclerosis on MRI may not always correlate with SPECT findings in temporal lobe epilepsy (TLE). This study suggests positive SPECT findings are common even in patients with normal MRIs, indicating potential neocortical epilepsy origins.
Area of Science:
- Neurology
- Radiology
- Nuclear Medicine
Background:
- The diagnostic significance of MRI-detected mesial temporal sclerosis in temporal lobe epilepsy (TLE) requires further clarification.
- Understanding the relationship between MRI findings and functional imaging like SPECT is crucial for epilepsy localization.
Purpose of the Study:
- To investigate the correlation between MRI-defined mesial temporal sclerosis and interictal SPECT findings in patients with temporal lobe epilepsy.
- To assess the prevalence and localization of hypoperfusion in TLE patients with and without MRI evidence of mesial temporal sclerosis.
Main Methods:
- Selected 18 patients with complex partial seizures, unilateral temporal EEG focus, and normal CT.
- Categorized patients into Group I (n=11) with MRI-confirmed mesial temporal sclerosis and Group II (n=7) with normal MRIs.
- Performed interictal SPECT using 99m-Tc HMPAO with concurrent EEG monitoring.
Main Results:
- Lateralized hypoperfusion ipsilateral to the EEG focus was observed in 72% of patients.
- Temporal hypoperfusion was detected in all Group II patients (normal MRI) and 6 Group I patients (MRI-evident sclerosis).
- SPECT demonstrated a higher positivity rate in patients with normal MRIs than previously reported, suggesting potential neocortical origins.
Conclusions:
- Interictal SPECT findings can be positive even in the absence of MRI-defined mesial temporal sclerosis.
- Positive SPECT findings may be as prevalent in neocortical epilepsy as in mesiolimbic epilepsy.
- This challenges the assumption that MRI-evident mesial temporal sclerosis is the sole indicator for temporal hypoperfusion in TLE.