Diagnostic Tests for Neurological/Spinal Injury or Disorder
Medical Disclaimer
MRI and MRA
Magnetic Resonance Imaging(MRI) and Magnetic
Resonance Angiogram(MRA) are done by a sophisticated computer that uses radio-frequency energy and a strong
magnetic field to provide detailed images of internal organs and tissues. The
image results from the different water concentration of the various tissues. No
radiation exposure is involved. The conventional MRI machine consists of a
closed cylindrical magnet in which the patient must lie totally still for short
periods of time. MRI causes no pain, but some patients do find it uncomfortable
and even claustrophobic, though your doctor may prescribe mild sedation.
However, newer, more patient-friendly MRI systems (Open MRI) are
now in widespread use, but some doctors prefer standard systems.
Depending on the part of the body being examined, a contrast agent may be used
to enhance the visibility of certain tissue or blood vessel. This is
administered through a small needle connected to an intravenous line(IV) placed in
vein in the arm or hand. An MRI/MRA is a completely safe, non-invasive
procedure and can take from 15 minutes to an hour to complete, depending on
the part of the body being imaged.
MRI can be used to identify and monitor tumors of the brain and spinal cord.
It can also measure metabolic changes in the active part of the brain
and can be used to map those parts of the brain that handle critical
functions such as sensation, movement, thought and speech. It can also
document changes in chronic disorders of the nervous system such as Multiple
Sclerosis(MS). It is also a useful
diagnostic tool for identifying diseases of the
blood vessels as well as stroke. It is commonly used for patients with diseases
of the pituitary gland. It is also widely used to diagnose sports related
injuries and is useful in documenting brain abnormalities related to dementia
or seizures. MRI can also detect tissue abnormality in patients with diseases
of the eye, inner ear, or abnormalities of the brain stem such
as Chiari
Malformations.
Because the MRI gives such clear pictures of soft-tissue structures in and
around bones, it also is the most sensitive exam available for spinal problems.
It is particularly helpful in identifying stenosis (narrowing of the spinal
canal) and
herniated discs. The MRI can be critical to planning surgery,
radiation therapy, treatment for stroke, or other interventions to treat brain
diseases/disorders. The MRA demonstrates blood vessels in the neck and brain and can
help detect abnormalities.
For an MRI of the head, the patient is placed on a sliding table and a radio
antenna device called a surface coil is positioned around the upper part of the
head. The patient is then positioned inside the MRI gantry. The MRI exam will
generally take from 15 to 45 minutes.
The functional MRI looks at how the brain is actually functioning by identify
regions of increased brain activity. Increases in microscopic vessel size,
chemical changes, or heat production are all signs that a particular part of
the brain is processing information and giving commands to the body. For this
test, the patient performs a particular task while the imaging is taking place.
The metabolism in the area of the brain responsible for that task will
increase, and the signal in MR image will change. By performing specific tasks
that correspond to different functions, it is possible to locate the area in
the brain that governs that function. This information is helpful to a surgeon
so that he/she can avoid those important areas during surgery. The patient lies
on a sliding table with his or her head in a brace designed to hold the head
still, then is slid under or into the cylindrical magnetic unit which creates
the image. As the test progresses, the patients will be asked to perform
various tasks, such as tapping the thumb of one hand against each of the
fingers in that hand.
CT or CAT Scan
The computed tomographic scan (CT or
CAT scan) uses an x-ray beam and a
computer to generate 2 dimensional images of the body. The information is
displayed in a cross-section or "slice" of body tissue. Neurological CT scans
focus on the head or spine.
CAT scans can help detect spinal stenosis (narrowing) or a
herniated disc.
They can assist in locating brain damage in patients with head injury, detect
a blood clot or bleeding in patients with a stroke, detect certain brain
tumors, illuminate enlarged brain ventricles (cavities) in patients with
hydrocephalus, assist in planning radiation therapy for cancer of the brain,
or detect bleeding in a patient with a ruptured or leaking aneurysm. CT can
clearly show even the smallest bones of the body as well as surrounding muscle
and blood vessels. This makes it invaluable in diagnosing and treating cranial
and spinal problems.
CT scanning is fast, painless, and simple and involves little radiation
exposure. If contrast material is injected, patients may experience a warm,
flushed sensation or experience a metallic taste in their mouth for a few
minutes. The CT scanner is a large, square machine with a donut-like hole in
the center. The patient lies on a table that can move up or down and slides
into and out of the center of the hold. The patient's body may be supported
by pillows to help hold it still and in the proper position during the scanning
process. Inside the machine, an x-ray tube on a rotating gantry moves around
the patient's body to produce the images, making clicking and whirring sounds
as the gantry moves. A CT scan usually takes from 15 minutes to 30 minutes; a
CT exam of the head and brain can take between 10 and 45 minutes.
Enhanced CAT Scan with Intrathecal Contrast
This test is similar to a myelogram, which utilizes contrast or x-ray dye to
better visualize the spinal canal and nerve roots in the spine. This test can
be performed to determine problems in the cervical, thoracic and lumbar spine.
Regardless of what area is to be studied, the physician first applies a numbing
medication to the skin. Then, using x-ray guidance, more specifically,
fluoroscopy, the physician injects a very
low dose of an intrathecal contrast agent into the patient's spinal sac, where
the spinal fluid is located. Regardless of what level of the spine is to be
studied, the contrast is injected in the lower back and then the patient is
moved into a position that enables the flow of contrast to reach the area of
interest. Contrast is heavier than water. The patient then undergoes a CAT Scan
of the portion of the spine under scrutiny. The CAT Scan takes approximately
45 to 60 minutes to complete.
Angiography
During this test, a series of regular x-rays are taken as a radiopaque
(impenetrable by x-ray) contrast material is injected directly into an
artery. The resulting radiographic image is like a map of the blood vessels.
An angiogram is an accurate way of looking at arteries and veins of the head,
neck and brain, and provides information that cannot be obtained with other
tests. It is often used to determine the degree of narrowing of an artery in
the head or neck. It can also be used to detect the location and size of
aneurysms and vascular malformations. This is an invasive test, requiring a
physician to insert a catheter into the major artery near the groin and direct
it "upstream" to the arteries near the brain.
Doppler Ultrasound
This is a basic imaging test to judge the health of the carotid arteries and
is done as part of an assessment of a patient's risk of stroke. It is a
non-invasive test that takes about 15 to 20 minutes. The patient reclines on
an exam table and the physician passes an electronic hand-held device over the
body area of concern, pressing the device directly across the skin. The device
transmits sound waves that are reflected from the structures in the neck and
reconstructed into a picture of the outsides and inside of the artery walls.
The Doppler can also use changes in the reflected sound waves to determine the
velocity of blood flow through the artery. Just like stepping on a garden
hose, a high velocity implies a narrower vessel. The Doppler ultrasound usually
can only visualize arteries in the neck.
EMG
The Electromyography(EMG) test is used to learn more about the functioning
of peripheral nerves, which are those in the arms and legs. The results show if
a nerve is pinched, and give an estimate of how severely, and where it is
compromised. An EMG tests for the electrical impulse coming from the brain
and/or spinal cord to the affected area. If that impulse is blocked somewhere
along the spinal pathway, it may be delayed or reduced enroute to its final
destination, such as the skin, a muscle, finger tips, etc. Therefore, abnormal
function could mean there is nerve injury or muscle dysfunction. This test can
be a bit uncomfortable, your doctor may prescribe a mild sedative.
Muscles receive constant electrical signals from properly functioning nerves,
and in turn they broadcast their own electrical signals. During an EMG, the
electrical activity in muscles is measured. The doctor places very thin
needles (like those used in acupuncture) into the muscles to record the
electrical signal from the various leg or arm muscles. If a muscle doesn't
receive adequate impulses from its nerve, it broadcasts signals that indicate
the muscle is confused.
The results of this test are usually correlated with the results from the
Nerve Conduction Study, allowing the doctor to determine which nerves are
pinched and the degree of malfunction.
Nerve Conduction Study
This is a sensitive test most often done along with with an EMG. It utilizes
electrical stimulation of a specific nerve or nerves and records the nerve's
ability to transmit an impulse. This study can determine how well a nerve is
functioning.
During this test, electrode patches are placed along the known course of the
nerve. The nerve is then stimulated with a tiny electrical current at one
point. A nerve should then transmit the signal along its course so that an
electrode placed further done the arm or leg captures the signal as it passes.
A normally functioning nerve will transmit the signal faster and stronger than
a sick nerve.
The results of this test are usually correlated with the results from the EMG
test, allowing the doctor to correlate which nerves are pinched and the degree
of malfunction. Nerve Root Block Nerve roots exit the spinal cord and form
nerves that travel into the arms or legs. These nerves allow movement of the
arms, chest wall, and legs. These nerve roots may become inflamed and painful
because of irritation from a bony spur or herniated disc in the spine. This
test provides important information about which nerve is causing pain by
temporarily numbing the nerve root of concern. If the patient's pain is reduced
after the injection, that nerve is most likely causing the pain. If the pain
level is unchanged, that nerve is most likely not causing the patient's pain.
By confirming or eliminating the exact source of pain, the test allows the
physician to develop appropriate treatment, which could include further nerve
blocks and/or surgery.
Discography
This controversial, painful test is used to determine if intervertebral discs in the
spinal column are a source of pain. This test involves the placement of a
needle into the disc spaces while utilizing x-ray guidance and injecting
contrast material. The discs are soft, cushion-like pads, which separate
the hard vertebral bones of the spine. A disc may cause pain in the neck,
mid-back, low back, arms, chest wall, abdomen or legs when it bulges,
herniates, tears or degenerates.
CT and MRI scans only illustrate anatomy and cannot prove a patient's source
of pain. In some cases, discs may appear abnormal on MRI or CT scans but not
be the source of pain. A discogram can help identify discs that cause pain and
help the neurosurgeon plan the correct surgery. A negative discogram can help
avoid surgery that may not be beneficial. Because of the nature of the test,
discography is usually done only if the patient's pain is significant enough
to consider surgery.
During the procedure, an IV is started to administer antibiotics and a sedative
to help relaxation. The patient will lie on his/her back for discography of the
cervical spine and on his/her side for discography of the thoracic and lumbar
spine. The physician numbs the skin, then directs a small needle, using x-ray
guidance, into the space of the suspect disc. The procedure may be performed at
more than one disc level at the same time. After the needle is properly
positioned, a small amount of contrast is injected into each disc, with the
expressed intention of provoking pain. Immediately
thereafter, the patient is taken to the CAT scan machine where additional
images are taken. Following the CAT scan, patients are taken to a recovery
area and monitored for 30 to 60 minutes. A prescription for pain medication
often helps with managing muscle discomfort that may occur for a few days
after the procedure. If at all possible, avoid this test unless absolutely
required.
Nuclear Imaging - PET and SPECT
PET(Positron Emission Tomography) and SPECT (Single Photon Emission
Computed Tomography) Scans are part of the family of nuclear imaging techniques
that use small amounts of radioactive isotopes (radionuclides) to measure
cellular and/or tissue metabolism. Radionuclides are absorbed by healthy tissue
at a different rate than tissue that is diseased.
A PET scan can map the biological function of an organ, detect subtle
metabolic changes, may be used to determine if a tumor is benign or malignant.
The PET scan utilizes a machine called a cyclotron, which is an accelerator
that propels charged particles using alternating voltage in a magnetic field
to generate radioisotopes. The patient is injected with a radionuclide specific
to the function or type of metabolism being tested for. The radionuclide will
collect in that specific area of the body. The patient lies on a scanning table
while a ring-shaped machine is positioned over the target area of the body.
Detectors in the ring pick up gamma rays emitted from the body tissues. A
computer analyzes the data and produces cross-sectional images on film and/or
a video monitor.
A SPECT Scan is used to determine blood flow to tissue, which helps discover
how well and organ may be working. It is very sensitive and useful in detecting
stress fracture, spondylosis (a degenerative disease of the spinal column,
infection (such as discitis), and tumor. As with a PET Scan, a radionuclide
is injected intravenously into the patient and it circulates through the blood.
A camera then rotates around the patient, picking up images cast by the
radionuclide. The information is then transferred to a computer that converts
the data into film images. The images are projected as cross-sections of the
body and can be rendered into a computerized, 3 dimentional(3D) format.
this file not directly accessible
