Diagnosis and Tests
The first and foremost important step in the successful management
of epilepsy is its accurate diagnosis. Other conditions may be
confused with seizures; some that are particularly relevant in
the pediatric age group include syncope, staring spells due to
inattention and symptoms due to psychological conditions. Once
an accurate diagnosis is established, the next step involves identifying
the possible cause and pursuing an appropriate treatment option.
MRI Scan
• The MRI shows the gross appearance of the brain and therefore
can give anatomic and pathological information of the brain.
• Be sure that no medical (non-surgical) options are available.
If there are, these would be recommended to you and to your neurologist
at home.
• The use of the MRI scan in patients with epilepsy has been
aided by FLAIR techniques and High Resolution MRI imaging and
MRI volumetrics.
FLAIR Imaging
• Fluid-attenuated inversion recovery (FLAIR) improves the
contrast and appearance of abnormalities within the brain.
• It is often helpful to make clear contrast between abnormal
findings (lesions) and normal findings (Cerebrospinal fluid).
• High Resolution MRI
• Obtaining small thin slices through the brain allows the
images to be reconstructed to render a 3-D image of the brain.
• This technique is useful in identifying subtle lesion in
the brain (i.e. cortical dysplasia) as well as their full extent
of involvement.
MRI Volumetrics
• After obtaining the high resolution MRI scan, computer
software can be employed to calculate the respective volume of
a brain structure on one side of the brain and compare it to the
size of the same structure on the other side of the brain.
• MRI volumetrics is occasionally used to evaluate the medial
temporal structures which are frequently abnormal in a disease
called ‘mesial temporal sclerosis’ a frequent cause
of medically intractable epilepsy.
PET Scan
• Positron Emission Tomography (PET scan) is frequently used
during the evaluation for epilepsy surgery.
• PET scans can give information on the function of the brain.
For instance it can give information on how various regions of
the brain metabolize glucose.
• Areas which are not functioning well based on PET scan
may overlap with the region of brain giving rise to epilepsy.
• So this test is often helpful in confirming the epilepsy
syndrome and occasionally helpful when previous testing have not
been able to localize the onset of the epilepsy to one region
of brain.
• Areas of brain which do not metabolize glucose well may
reflect the dysfunctional region of brain giving rise to seizures.
Ictal SPECT Scan
• Single photon emission computed tomography measures the
relative blood flow in various regions of the brain.
• This particular neuroimaging tests brain blood flow information
at a specific moment in time.
• The point in time the test reflects is the time in which
a particular pharmacologic tracer is injected.
• When the tracer is injected soon after the onset of a seizure,
information of blood flow during a seizure can be obtained.
• Ictal SPECT is therefore another functional neuroimaging
test which reflects regional blood flows during seizures.
• Areas which light up during this test may reflect the area
of brain in which the seizures begins.
MRS
• Magnetic resonance spectroscopy uses techniques from MRI
imaging to give quantitative chemical information of the brain.
• The information is usually displayed graphically. Various
amounts of specific chemical are evaluated to look for too much
or too little of specific chemicals in specific regions of the
brain.
• This information looks for an abnormal chemical signature
in one region of brain which again can be useful in the evaluation
for possible epilepsy surgery.
Neuropsychological testing
Most pre-surgical patients typically complete neuropsychological
testing. Neuropsychology is the study of the brain and behavior.
Different regions of the brain are associated with different thinking
skills. Neuropsychologists have developed tests that measure a
variety of thinking skills such as language, attention, problem
solving, and memory. In addition, neuropsychological testing includes
measures of emotional and behavioral functioning. A child's pattern
of strengths and weaknesses on neuropsychological testing can
provide an indication of how well different regions of the brain
are working. Neuropsychological testing is useful in the pre-operative
evaluation of epilepsy surgery candidates for three reasons: 1)
to establish a baseline of function from which to evaluate changes
following surgery; 2) to identify potential regions of brain dysfunction
that might be related to the seizure focus; and 3) to assist in
determining potential risks to thinking skills associated with
epilepsy surgery. In addition, information from a neuropsychological
assessment can be very useful for the schools in identifying the
most appropriate teaching strategies.
