SPECT scans

  I suffered a serious head injury, but doctors are still at a loss why I just fell unconscious without warning.  MRI is normal, EEG shows abnormalities in the left front of the brain.  The spect however shows serious perfusion restriction in the front left temporal lobe and in a few other areas also some restriction.  My question is if there is a standard for SPECT scans and to what extent can this be used as a diagnostic tool.  Several doctors have widely varying opinions of the validity of these type of scans.  I suffer from multiple symptoms and disorders to such an effect that I am unable to do work.
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Thanks for your question.  As you probably know, the SPECT scan of the brain
is an imaging technique that attempts to indicate the perfusion status of
different areas of the brain.  It is often used to study the "hemodynamic
reserve" particularly during the second phase of the study, when a vasodilating
agent is given to the patient.  Brain regions that has a less than optimal
response to such blood vessel dilating agents will appear less well irrigated
than areas respond well to such agents.  Similarly, brain areas that are
just above the "normal threshold" of perfusion will also show up as
hypo-perfused during this second "stress stage" of the test.  There is a
degree of subjectivity on the interpretation on what constitutes a mild, a
moderate, or a severe hypoperfusion, but particularly for the latter two
degrees of hypoperfusion (moderate/severe), the inter-observer variation in
rating when compared with a normal perfusion is quite reliable.  In other
words, two or more physicians intepreting a moderate or severe hypoperfusion
scan would very likely agree on the diagnosis.  In your particular case,
it is possible that the head trauma did cause a lesion to the left temporal
region that is not "visible" in a static study (such as a MRI), but is
demonstrated by the SPECT scan.
I hope this information is helpful.  Best of luck.
This information is provided for general medical education purposes only.
Please consult your doctor regarding diagnostic and treatment options.