Hippocampal Volumetric and Morphometric Studies in Frontal and Temporal Lobe Epilepsy

Abstract

The most common temporal lobe pathology is Ammons Horn sclerosis (AHS), and several different imaging techniques have been utilized to detect this with varying success. We describe the clinical application of magnetic resonance imaging (MRI) using a three-dimensional volume technique which allows total hippocampal volume to be measured and symmetry evaluated. Hippocampal surface area was calculated in sequential 1.5 mm thick contiguous images, using a GE IC workstation. Total volumes and surface areas were calculated. The cross-sectional surface area at 1.5 mm intervals was displayed graphically, permitting morphometric analysis of the hippocampus throughout its length. Focal atrophy within any part of the hippocampal formation (HF) and its extent could thus be assessed. Patients with well-lateralized temporal lobe epilepsy (TLE) (n = 20) and well-defined frontal lobe epilepsy (FLE) (n = 20) were studied, and volumes compared with normal values derived from 10 neurologically normal controls. Asymmetric hippocampal volume loss was demonstrated in all 20 patients with clinically typed TLE, but not in normal controls or patients with FLE. Volume loss distribution was anterior in 12 patients, posterior in one patient and widespread in seven patients. Secondarily generalized seizures were strongly associated with widespread loss. This method of surface area and volumetric analysis of the hippocampus in TLE can demonstrate asymmetry and focal involvement, and help distinguish between hippocampal and frontal pathologies.

MR-based in vivo hippocampal volumetrics: 1. Review of methodologies currently employed

“…Measuring the tail of the hippocampus is the most difficult part, but using the coronal section on which the crux of the fornices is seen in full profile, allow measurement of the head, body, and most of the tail of the hippocampus (90-95%). 20,56 Several authors define the posterior border of the hippocampus as the crura of the fornices, 20,21,53,56,108 but others use the presence of the inferior and superior colliculli, 46,78 or the absence of the vertical fissures of the Sylvian fissure instead. 84 All of these differing anatomical boundary definitions are a source of major variation among the protocols and constitute the largest source of discrepancy in normative hippocampal volumes found by the various research studies.…”

“…Some researchers, such as Shenton et al, 54 measured the amygdala-hippocampal complex, whereas others reliably differentiated between amygdala and hippocampus. 20,21,55 Of the protocols in this database, 80% attempted to measure as much of the hippocampus as they could, and included the head and body in their measurements. Only a small minority of these studies excluded the tail.…”

“…The protocol of Jack et al, 53 which has been revised in 1994, 56 and that of Watson et al protocol 20 are the most popular and are reported to have been used in 31 studies each. The protocols of Soininen et al 55 and Cook et al 21 are two other important and popular ones, which are also used frequently. Together, these 14 protocols account for 46% of the hippocampal volumetric studies performed to date.…”

“…17 The MR-derived hippocampal volumetric technique has demonstrated good validity and reproducibility, [18][19][20] and accuracy of the measurements has been shown by MRI volumetric measurement of phantoms with a known volume. 18,21 However, studies on hippocampal volume in neuropsychiatric disorders are inconclusive and do not always provide consistent results. There are differences in laterality (right or left), direction (increase or decrease), and degree of the hippocampal volumetric changes.…”

T1ρ MRI of Alzheimer's disease

“…With speed and simplicity, linear measurements of inter-object distances in the brain are able to differentiate between normal and AD-affected patients but with significant overlap between normal controls and mild AD-affected individuals (DeCarli et al 1990). Morphological changes monitored in 2D cross-sections lack the full potential of volumetric analyses but are generally less time-consuming (Cook et al 1992). The volume of CSF, gray matter (GM), and white matter (WM) change with the progression of AD (Sullivan et al 1993;Convit et al 1997;Thompson et al 2007).…”