Diagnostic Tests and Scans - Fact Sheet
 A variety of tests can be done to help determine if you have a 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.
MRI, CT and MRA
The MRI (Magnetic Resonance Imaging) and CT (Computed Tomography, also known as CAT - Computerised 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 haemorrhaged 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 specialised 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.
EEG
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 Cerebral Cortex. 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 localise areas of slowing of electrical activity. Alone, a QEEG is insufficient to diagnose brain damage but can help to confirm other tests.
PET Scan
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 and 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.
SPECT Scan
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.
Evoked Potentials
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.
Lumbar Puncture
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 haemorrhage.
MRS and 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 catheterisation 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.
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Diagnostic Tests and Scans 
