Mesial temporal lobe epilepsy is characterized by hippocampal stiffness alterations and relational memory deficits
Hillary Schwarb1, Curtis L. Johnson2, Bradley P Sutton1, Tracey M Wszalek1, Graham Huesmann3; 1University of Illinois, 2University of Delaware, 3Carle Foundation Hospital
Mesial temporal lobe epilepsy (MTLE) is the most common cause of persistent, medically-intractable seizures, but has promising surgical outcomes. The use of surgical intervention requires positive structural MRI findings (e.g. hippocampal volumetry), however, with traditional methods, significant tissue damage must occur before detection is possible. Because surgery is highly effective in stopping seizures, the development of novel, sensitive imaging biomarkers for earlier detection is essential. MTLE is characterized by degradation and scarring of lateral hippocampal tissue over time accompanied by considerable memory deficits. Magnetic resonance elastography (MRE) is an emerging non-invasive tool for quantitatively measuring tissue stiffness that reflect the microstructural health of tissue. Because MTLE ultimately results in sclerotic hippocampal tissue, which should be stiffer than healthy tissue, MRE may prove an important tool for early MTLE detection. Further, MRE measures of hippocampal integrity may provide insight to memory impairment in MTLE. In this study, 9 MTLE patients were compared to 7 matched controls, and all participants completed an MRE scan and a relational memory behavioral battery. Patients were significantly impaired on all relational memory measures. Furthermore, MRE revealed higher hippocampal stiffness in the epileptogenic hemisphere compared to the unaffected side. The ratio of epileptogenic to unaffected hippocampal stiffness dissociated patients from controls with high accuracy. Finally, the significant relationship between relational memory performance and tissue stiffness was similar in both hemispheres for controls, but present only in the contralateral (non-epileptogenic) hemisphere for patients. These data suggest that MRE, combined with memory measures, may be beneficial in characterizing MTLE.
Topic Area: LONG-TERM MEMORY: Episodic