Hippocampal sclerosis--origins and imaging.

Area of Science:

• Neurology
• Pathology
• Radiology

Background:

• Hippocampal sclerosis (HS) has been linked to epilepsy for nearly two centuries.
• Historically studied via postmortem analysis, HS is now primarily investigated using surgical specimens from temporal lobe resections.
• HS is the leading pathology in drug-resistant mesial temporal lobe epilepsy (MTLE).

Purpose of the Study:

• To review the diagnostic features of HS using magnetic resonance imaging (MRI) and histopathology.
• To discuss the pathological subtypes and associated lesions of HS.
• To evaluate the predictive value of imaging findings for surgical outcomes in MTLE.

Main Methods:

• Standard MRI protocols utilizing coronal slices to identify HS features like reduced hippocampal volume and altered signal intensity.
• Histopathological examination of surgical specimens to confirm neuronal loss and gliosis.
• Review of functional imaging studies, including 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET), for predicting surgical success.

Main Results:

• MRI can reliably detect HS, characterized by specific imaging features.
• HS exhibits diverse pathological patterns and can be associated with other neuropathologies.
• Preoperative MRI detection of HS strongly predicts favorable seizure outcomes following temporal lobe resection (TLR).
• Functional imaging, particularly FDG-PET, can aid in predicting surgical outcomes when MRI is inconclusive.

Conclusions:

• HS is a key pathological correlate of MTLE, with distinct MRI and histopathological findings.
• The presence of HS on MRI is a significant predictor of successful surgical treatment for MTLE.
• While surgical techniques evolve, approximately two-thirds of patients with HS undergoing surgery achieve seizure freedom.