Neurosurgeons use a variety of
diagnostic tests to help identify the specific nature of your neurological
injury or disorder. In turn, the results of these tests help the
neurosurgeon plan an appropriate course of treatment. Following are
descriptions of some of the most frequently performed diagnostic tests by
During this test, a series of regular x-rays are taken as a radiopaque
(impenetrable by x-ray) contrast material (dye) 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.
CT or CAT Scan:
The computed tomographic scan (also called a 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
This 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
(dye). 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
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
relaxation medication. 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. 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.
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.
stepping on a garden hose, a high velocity implies a narrower vessel. The
Doppler ultrasound usually can only visualize arteries in the neck.
Electromyography (EMG): This test is used to learn more about the
functioning of peripheral nerves (those in the arms and legs). It can tell
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 (skin, muscle, finger tips, etc.) Therefore, abnormal
function could mean there is nerve injury or muscle dysfunction.
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. (See Nerve Conduction Study below.)
Intrathecal Contrast Enhanced CAT Scan:
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 the physician
injects a very low dose of intrathecal contrast (dye) 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.
Magnetic Resonance Imaging (MRI)/Magnetic Resonance Angiogram (MRA):
MRI and MRA are done by a machine that uses radiofrequency 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. However, newer,
more patient-friendly MRI systems are now in increasingly widespread use.
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 via a small needle connected to an intravenous line placed in
vein in the arm or hand. An MRI/MRA is a non-invasive procedure and can take
from 15 minutes to approximately one 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 small metabolic changes in the active part of the brain
and therefore be used to map those parts of the brain that handle critical
functions such as thought, speech, movement, and sensation. It can also
document changes in chronic disorders of the nervous system such as multiple
sclerosis. 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 or inner ear.
Because the MRI can give 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 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.
Nerve Conduction Study:
This is a sensitive test usually done in conjunction 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 that a
nerve is functioning normally.
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.
Nuclear Imaging - PET (Positron Emission Tomography) and
SPECT (Single Photon Emission Computed Tomography) Scans:
PET and SPECT 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 image 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 3-D format.
Minimal invasive neurosurgery is becoming
more and more standard neurosurgical procedure, particularly in the brain
The use of neuronavigation,
today a routine method, has proved to
be a very useful surgical tool in the mini invasive neurosurgery. In our
Department, in the treatment of brain tumors or in the very deep lesion
removal a Brain Lab VectorVision neuronavigation system was used. BrainLab
navigator is an intraoparative, image-guided, frameless, localization
system, that consists of a computer workstation for registration of images
and physical spaces, an intraoperative localization device, and a computer
image display. The system provides real-time responses regarding the
locations of surgical instruments. VectorVision is based on passive
reflections of infrared flashes. Universal adapters with reflective markers
for surgical instruments, endoscopes and the operating microscope are used.
Neuronavigation increases radicality in tumors resection and was very
effective in the treatment of critical brain areas lesions.
neuro navigation systems based on preoperative MR or CT images help the
surgeon to locate the lesion with high precision in the planning process
prior to surgery. However, these tools have limited value for guidance
in cases where the brain shifts occur, since "the map then no longer
corresponds to the road". We believe that high quality intraoperative 3D
ultrasound can represent the solution in future neurosurgery by helping
the surgeon to navigate surgical tools with high presicion based on
images representing the patient current anatomy.
Surgical procedures can
then be performed safely and more radically in combination with