Hippocampal sclerosis is the most common pathological finding in temporal lobe epilepsy.
While CA1 and CA4 subregions are typically affected, considerable variability in the
involvement of the different subregions has been recognized between patients with
specific hippocampal subfield pathology being demonstrated to predict surgical outcomes
in medically refractory patients. Developing novel imaging biomarkers for hippocampal
subfield pathology that can be obtained in vivo has the potential to allow more accurate
prediction of surgical outcomes prior to surgery.
A major challenge in studying hippocampal subregions is the small size of the structures
which are often smaller than the resolution of conventional MRI techniques. Cerebral
blood vessels can be visualized with MRI using a variety of methods, some which do not
require MRI contrast and others that do. The advantage of non-contrast methods is that
subjects do not require intravenous contrast injections while the disadvantage is that
the non-contrast methods are not capable of visualizing smaller vessels.
Recently high-resolution vascular imaging of the hippocampus using ferumoxytol as an MRI
contrast agent has been reported by researchers at Wayne State University. It is believed
that this method would provide the detail required to address the hypothesis that the
microvasculature of hippocampal subregions is disrupted in temporal lobe epilepsy.
OBJECTIVES
The Specific Aims of this study are:
Aim 1: Implement ferumoxytol enhanced MRI imaging of cerebral vasculature with similar
quality as compared to work conducted at Wayne State University. Aim 2: Compare
hippocampal microvasculature density of hippocampal subregions between participants with
TLE and hippocampal sclerosis and control subjects.
HYPOTHESES
Successful acquisition of susceptibility weighted imaging (SWI) vascular imaging,
with similar quality as compared to work conducted at Wayne State University, will
be possible.
Participants with temporal lobe epilepsy and hippocampal sclerosis will demonstrate
reduced microvasculature in hippocampal subfields that will correlate with
previously reported regional MRI changes.
METHODS /DATA ANALYSIS
AIM 1:
10 control subjects will be scanned using the Wayne State University SWI acquisition
protocol. Participants will receive ferumoxytol diluted with normal saline administered
by a Registered Nurse using an MRI compatible IV infusion pump. Any adverse events during
the infusion / scan will be documented and compared to previous ferumoxytol MRI safety
data. Data quality will be assessed both qualitatively and quantitatively. Maps of the
hippocampal microvasculature will be obtained and reviewed in order to confirm that the
quality of the maps is comparable to the Wayne State University data. Fractional vessel
density (FVD) of microvasculature, major arteries and major veins will be obtained, and
comparisons will be made to ensure that the mean values and standard deviations are
comparable.
AIM 2:
20 control subjects, and 20 participants with temporal lobe epilepsy and hippocampal
sclerosis, will be studied. Participants will receive ferumoxytol diluted with normal
saline administered by a Registered Nurse using a MRI compatible IV infusion pump. Any
adverse events will be documented.
Microvasculature density of hippocampal subregions will be evaluated based on the same
image analysis approach as the Wayne State University Group.