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MRI assessments of hippocampal pathology in extratemporal lesional epilepsy
G D Cascino1, C R Jack, F W Sharbrough
1Department of Neurology, Mayo Clinic, Rochester, MN 55905.
Abstract:
We performed a prospective study in 18 patients to determine the extent of MRI-identified hippocampal pathology in patients with intractable partial epilepsy of extratemporal origin. A mesial temporal signal-intensity alteration or hippocampal formation (HF) atrophy, or both, have been shown to be reliable markers of the temporal lobe of seizure origin in patients with mesial temporal sclerosis. All patients subsequently received surgical ablative therapy between 1988 and 1992. During shortterm follow-up, 14 of the 18 patients experienced a significant reduction in seizure tendency, and 12 patients were rendered seizure-free. Qualitative and quantitative (HF volumetry) assessments of HF pathology were performed retrospectively by a blinded investigator. No hippocampal imaging alteration was present in 17 patients. Left HF atrophy was confirmed in one patient with post-traumatic epilepsy who underwent a successful right frontal lobectomy. Morphometric MRI studies rarely identify hippocampal pathology in patients with extratemporal epilepsy.
Insights
Magnetic resonance imaging (MRI) rarely detects hippocampal pathology in epilepsy originating outside the temporal lobe. This study found minimal MRI-identified hippocampal abnormalities in patients with intractable extratemporal partial epilepsy.
Area of Science:
- Neurology
- Radiology
- Neurosurgery
Background:
- Mesial temporal signal intensity alteration or hippocampal formation (HF) atrophy are markers for temporal lobe epilepsy.
- Extratemporal epilepsy originates outside the temporal lobe, and its association with hippocampal pathology is less understood.
Purpose of the Study:
- To investigate the prevalence and extent of MRI-identified hippocampal pathology in patients with intractable partial epilepsy of extratemporal origin.
- To assess the utility of MRI in identifying hippocampal abnormalities in this patient population.
Main Methods:
- Prospective study of 18 patients with intractable partial epilepsy of extratemporal origin.
- Retrospective qualitative and quantitative (HF volumetry) MRI assessments of hippocampal pathology by a blinded investigator.
- Surgical ablative therapy was performed, with short-term follow-up assessing seizure reduction.
Main Results:
- No hippocampal imaging alteration was detected in 17 out of 18 patients.
- One patient with post-traumatic epilepsy showed left HF atrophy and underwent successful right frontal lobectomy.
- 14 of 18 patients experienced significant seizure reduction, and 12 were seizure-free post-surgery.
Conclusions:
- Morphometric MRI studies rarely identify hippocampal pathology in patients with extratemporal epilepsy.
- The findings suggest that hippocampal abnormalities are uncommon in this epilepsy subtype, despite surgical success in some cases.