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- Diagnosing
Epilepsy
Diagnosis
of seizure disorder is based on the following considerations:
Medical History: the physician needs to know when seizures
started, and have a detailed description of seizures. The family's
health history is also considered.
EEG: an Electroencephalogram(EEG) detects electrical
impulses in the brain. The brain's electrical impulses are transmitted
from small metal discs placed on the patient's scalp, through
wires which are hooked up to the EEG machine. EEGs are useful
in identifying areas of increased nerve cell activity.
MRI: Magnetic Resonance Imaging(MRI) uses a large
magnet positioned around the person to produce a magnetic field
in the patient's body. Precise two-or three-dimensional images
are produced, providing doctors with detailed information about
the brain's structures.
MEG/MSI: Magnetoencephalography(MEG), also called
Magnetic Source Imaging(MSI), records magnetic brain
waves, much the same as an EEG records electrical brain waves.
It is used to assess the function of brain tissue.
CAT Scan: Computerized Axial Tomography is a
special type of radiological procedure which is used to take images
of the brain. The X-rays are analyzed by a computer to show the
brain's structures. This information helps doctors spot any damage
inside the brain which could be generating abnomal electrical
signals.
PET: Position emission tomography (PET) provides
information about the brain's metabolic activities by detecting
how quickly tissues absorb radioactive isotopes. A radioactive
gas or an IV injection of glucose tagged with isotopes is administered
to the person being tested. The isotopes emit positrons that combine
with negatively charged electrons in tissue cells to create gamma
rays. A computer translates the gamma rays into patterns that
reflect cerebral blood flow, blood volume and neuron metabolism.
Functional MRI: Functional MRI is similar to PET, providing
information on active brain tissue functioning and blood delivery.
However, it is more precise in temporal and spatial resolution.
It is an ideal tool in pre-operative planning because it reveals
the exact location of the seizure area.
Magnetic Resonance Spectroscopic Imaging(MRSI): is similar to
Magnetic Resonance Imaging (MRI) except that while MRI looks at
the signals detected from the protons of water, MRSI looks at
those from many other proton-containing metabolites.
Single Photon Emission Computed Tomography (SPECT):
produces 2 - or 3 - dimensional images by tracing a radioactive
substance injected into a vein. A Spect scan can help to locate
the site where a seizure originates, can confirm the diagnosis
of a seizure type, and help in evaluation for possible surgery.
Testing equipment is not currently available in all areas and
is constantly improving. Consult your specialist or local epilepsy
association.
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