Limbic System Abnormalities Associated with Ammon's Horn Sclerosis Do Not Alter Seizure Outcome after Amygdalohippocampectomy

Abstract

Summary:Purpose: To evaluate whether limbic system abnormalities associated with Ammon's horn sclerosis alter seizure outcome after selective amgydalohippocampectomy.Methods: In 45 patients with unilateral mesial temporal lobe epilepsy, histologically proven Ammon's horn sclerosis, and uneventful postoperative course, volumes of the hippocampus, hemisphere, amygdala, entorhinal cortex, mamillary body, and fornix were measured by using a T 1 -weighted 3-D gradient-echo sequence with roughly isotropic (1.17 × 1.17 × 1-mm) voxels. In addition, signal intensity of the hippocampus and of the temporal lobe white matter was visually assessed and graded on a coronal T 2 -weighted fast-spin-echo sequence with 2-mm-thick slices. Volumetric measurements and visual analysis were compared between seizure-free and non-seizure-free patients examined 12 months after surgery.Results: Hippocampal, hemispheric, entorhinal cortex, mamillary body, and fornix volumes, but not amygdalar volumes, were significantly smaller on the operated-on than on the nonoperated-on side and significantly smaller in patients compared with controls. No volume differences of the hippocampus, hemisphere, amygdala, entorhinal cortex, mamillary body, and fornix existed between seizure-free (Engel class IA) and non-seizurefree patients (Engel class IB-IV). Increased temporal lobe white matter signal was observed in 15 patients but did not alter seizure outcome.Conclusions: Limbic system abnormalities are not a surrogate marker to predict postsurgical seizure outcome in patients with unilateral Ammon's horn sclerosis.

The Frequency and Extent of Mammillary Body Atrophy Associated with Surgical Removal of a Colloid Cyst

“…A stereologic technique was used to derive mammillary body volume, whereas other studies have used planimetric techniques with patients presenting with cognitive impairment 30 and temporal lobe epilepsy. 28 Stereology is associated with high levels of reproducibility; and before measurement of the entire cohort, good 45 intrarater reliability values of 0.99 for right and left structures, by using the 0.8-mm scans, were obtained, demonstrating that our technique was reproducible, even when applied to patients having significant mammillary body atrophy.…”

“…Although the present study used a 1.0-mm-volume scan for comparison purposes, previous MR imaging studies of the mammillary bodies have used a variety of section thicknesses (1.0 mm, 31 1.1 mm, 28 1.5 mm, 29,30,32, and 3.0 mm 26,27 ). Other differences included the use of a 3T imaging system because previous MR imagingϪbased measurements of mammillary body volume have used 1.5T systems.…”

“…[27][28][29][30][31][32] An additional MR imaging sequence was used to acquire intracranial volume data for normalizing the data for differences in head size across patients and controls. This sequence was a T2-weighted intracranial volume scan; parameters were TR, 3000 ms; TE, 102 ms; FA, 150°; 3-mm section thickness; 10-mm section gap; acquisition time, 2 minutes.…”

“…This was a challenge because the mammillary bodies are positioned at the base of the brain and are small, with an estimated volume of approximately 50 mm. 3,26,27 Unlike previous MR imaging studies of the mammillary bodies, 28,29 the volume estimates were based on stereology, which uses a randomly generated start section and randomly generated grids for the measurement procedure, therefore ensuring that the volume estimates were unbiased, (ie, sections and grids were not chosen by the observer) and ensuring predictable precision.…”

Neuroimaging in Focal Epilepsies: An Update

“…[16] Secondary MRI findings of HS include: atrophy of structures of the limbic system, such as amygdala, ipsilateral mammillary body, entorhinal cortex, ipsilateral fornix, posterior thalamus, cingulate gyrus and contralateral cerebellum. [17,18] Atrophy-signal alterations of the contralateral hippo- Sagittal images parallel to the long axis of hippocampus 1) T2WI 3D: no gap, FOV = 230x230, voxel size = 1,5x1,5x1,5 mm, TR = 1800 ms, TE shortest. 2) FLAIR 3D (fat-suppressed = spectral-attenuated inversion recovery): FOV: 250x250, voxel size = 1,2x1,2x1,0 mm, TR = 4800 ms, TE shortest, TI = 1650 ms.…”