Brain injury diagnostic tests & scans
Some of these tests may be
done very soon after admission to hospital as the doctors need to
rapidly assess the danger of the brain injury
Neurologic tests fall into two groups: tests that examine
the structure of the brain and those examining the function of the
brain. The first group includes the CT Scan and MRI,
the second group includes the EEG, SPECT scan, PET scan, and evoked
studies. These tests are commonly used after a traumatic brain
injury (TBI), but could also apply for other types of brain
disorder as well.
MRI, CT and
The MRI (Magnetic Resonance Imaging) and CT (Computed
Tomography, also known as CAT - Computerized Axial Tomography) scan
the brain in cross sections. MRI does this with magnetic fields;
the CT scan uses x-rays. The MRI has a higher degree of resolution
than the CT scan so trauma seen by MRI may go unseen by CT scan.
The X-rays used in CT scans are better at detecting fresh blood
while the MRI scan is better at detecting the remnants of old
hemorrhaged blood, or damaged but intact nerve tissue.
CT scans may be done frequently after the injury to keep an eye
on the amount of brain injury. The MRA (Magnetic Resonance
Angiogram) is a specialized form of MRI which detects blood vessels
instead of brain tissue and can be used to check for bleeding or
for the health of blood vessels.
The Electroencephalogram records the ever changing but tiny
electrical signals coming from the brain using electrodes placed on
the scalp. Slowing of electrical activity in some areas of the
brain while the person is awake may indicate a lesion. Widespread
slowing may indicate a widespread disturbance of brain function.
Waves of electrical discharges indicate an irritable area of the
If allowed to spread, these spikes can produce a seizure. A
Quantitative EEG is capable of creating a map of the brain's
electrical activity throughout the day. Comparison with a typical
EEG makes it possible to localize areas of slowing of electrical
activity. Alone, a QEEG is insufficient to diagnose brain damage
but can help to confirm other tests.
Positron emission tomography measures concentrations of
positron-emitting radioisotopes within brain tissue. The brain uses
glucose for energy so glucose molecules are given a radioactive
"tag" and then breathed in by the patient. The person places their
head under a large Geiger counter that is able to detect areas of
the brain that are not using enough glucose.
Combined MRI & PET
The combined MRI/PET scan was announced in June 2007. The
technology is still in the prototype stage, but allows for the
simultaneous measurement of anatomy, functionality and
biochemistry. Although the scans are conducted separately,
combining them in one machine ensures that the images overlap
perfectly. This gives doctors a better picture of the state of
brain tissue following an injury, or the progression of a
degenerative condition such as Alzheimer's disease.
Single-photon emission computed tomography, like PET, acquires
information about the concentration of radio-nucleides introduced
to the patient's body. The radioactive chemical does not enter the
brain itself but stays in the bloodstream. It allows examination of
the brain's blood supply which is normally reduced to damaged
areas. Its advantage over PET scans is availability and cost.
Every time we hear, see, touch or smell our brain generates an
electrical signal. Evoked potentials are recorded by placing wires
on different parts of the scalp for different senses.
A lumbar puncture is a diagnostic test where cerebrospinal fluid
is extracted for examination, and pressure of the spinal column is
measured. In relation to acquired brain injury, it can look for
primary or metastatic brain or spinal cord neoplasm or cerebral
MRS & MRA
Magnetic resonance spectroscopy is an imaging method of
detecting and measuring activity at the cellular level. It provides
chemical information and is used in conjunction with MRI which
gives three dimensional information and has great potential in the
area of acquired brain injury.
Magnetic resonance angiography produces extremely detailed
pictures of body tissues and organs without the need for x-rays.
The quality is not the same as normal arteriography, but the
patient is spared the risks of catheterization and allergic
reactions to the dye. The MRA procedure is painless. The magnetic
field is not known to cause any tissue damage.
The long-term effects of a brain injury may not be evident for
some time. At best, those with a mild brain injury may be able to
return to work but will spend the rest of their lives battling a
range of Cognitive problems. Others will find themselves dependent
on others for the rest of their lives, while the most unfortunate
may never emerge from a state of Coma.
Intracranial pressure monitor
Swelling of the brain is a potentially very serious issue
immediately after a traumatic brain injury so doctors often
insert an intracranial pressure monitor into the skull
to make sure there is no increased pressure that could worsen the