Patients suffering from chronic fatigue syndrome (CFS/ME) do so because of cerebral function abnormalities as a result of diminution of brain blood flow, says a California nuclear medicine specialist. Dr Ismael Mena of the Harbor-UCLA Center in Los Angeles said: "All adult patients with chronic fatigue have abnormal diminution of blood flow to different areas of the brain - mostly in the frontal lobes." He told a meeting on CFS/ME recently that this diminished blood flow could reflect damage to those areas, but might also be the result of damage to another area of the brain that is expressed in the frontal lobes. He said the primary damage may be in the limbic system, particularly in the hippocampus. "This is the one that projects directly in the frontal lobes where most of the damage is seen in patients with chronic fatigue."

The diminution of blood flow to the temporal lobes could also explain why patients with chronic fatigue complain of cognitive impairment as that is where the memory resides. Using brain Single Photon Emission Computer Tomography (SPECT), Dr Mena studied the brain flow patterns of 19 normal people with an average age of 66; 33 CFS/ME patients with an average age of 55; and 26 patients with depression and a mean age of 62.

Great Precision
Although computed tomography (CT) and magnetic resonance imaging (MRI) can denote with great precision the structures of the brain, with brain SPECT the functions of the brain can be examined. Dr Mena said he examined the brain blood flow because it is directly related to brain function. Two sets of measurements were taken - one using 133Xe rCBF to measure the amount of blood flow in the brain tissue, the other, 99mTc-HMPAO, to provide images of brain blood flow.

Dr Mena said in a normal person the blood flow, when measured using 133Xe rCBF, fluctuates between 50 and 67 mL/min/100g of brain tissue. However, patients with CFS/ME donít exhibit a uniformity in blood flow. For example, in one patient, aged 42, blood flow was 37 mL/min/100g in the right frontal lobe. "For a person of this age it should be 55, ± 5", he said. In another example, a 48 year-old woman, there was extensive hypoperfusion in the frontal lobes. "But more extensively in the dorsal frontal lobes with blood flow between 38 mL and 47 mL", he said. The 99mTc-HMPAO data also showed patients had both frontal perfusion and temporal hypoperfusion, but to provide a more precise analysis of the data, Dr Mena said regions of interest were set and a computer was used to calculate the amount of blood flowing in them. Approximately 100 measurements were taken per patient.

Dr Mena said when this type of analysis was done, the distribution of 133Xe rCBF in a normal elderly person is close to 45 mL/min/100g. Again, this data showed in patients with CFS/ME there was a diminution of blood flow in the right hemisphere. With the 99m Tc-HMPAO data, Dr Mena said there was significant hypoperfusion throughout the frontal lobes as well as the right temporal lobe.

Dr Mena also examined the effect of exercise on patients with CFS/ME. Patients were given the standard cardiac stress test. While a normal person usually gets his wind back within five minutes after doing the test, those with CFS/ME had to wait at least one hour before their levels of carbon dioxide returned to their pre-exercise levels. "There's a marked worsening of blood flow in both hemispheres, but mostly in the right hemisphere, and these abnormalities persist up to 24 hours", he said. After 24 hours, sometimes even 48 hours, patients' brain blood flow returned to where it was at normal activity level.

Acknowledgment: Reprinted from The Messenger, March 1993, newsletter of The M.E. Association of Canada.

Reprinted from Emerge, September 1993.