CHICAGO - Minor motor disorders (MMDs) often appear in AIDS patients long before they develop overt basal ganglia dysfunction and encephalopathy. According to a presentation at Tuesday's neuroradiology scientific sessions at RSNA, MR spectroscopy's unique ability to detect neurologic signs of MMD could make it a useful tool for developing new drugs and therapies for HIV-positive patients.
Dr. Frank Wenserski from the Institute of Diagnostic Radiology at Heinrich-Heine University in Dusseldorf, Germany found elevated levels of the metabolite myo-Inositol in the brains of HIV patients with normal MRI results, raising the hope that increasing knowledge in this area may lead to prevention of more serious neurological dysfunction in patients with the HIV-1 virus.
Even in patients with no MRI lesions or clinical abnormalities, large European and American studies have shown that MMDs predict progression towards dementia and death in HIV-1-associated brain disease, Wenserski said.
"On the basis of a former PET study which showed initial hypermetabolism in the basal ganglia in patients in which MMD occurred, followed by a pseudo-normalization, and then finally hypometabolism in basal ganglia at the stage of clinically overt AIDS dementia, we decided to investigate some newer MR techniques -- like diffusion and perfusion imaging, and MR spectroscopy -- that have the potential to illuminate the pathologic mechanisms underlying HIV-1-associated MMD," he said.
To eliminate other possible causes of MMD, the researchers chose a very homogeneous group of subjects: 32 Caucasian homosexual males. None had an active history of intravenous drug use, and all but three were taking antiretroviral medications at the time of imaging.
The patients were divided into 3 groups: patients with normal motor function for at least one year (Group 1); patients with the first signs of motor dysfunction following at least a year of normal function (Group 2), and 12 patients with known sustained motor dysfunction for at least six months (Group 3).
No abnormalities were found in either diffusion- or perfusion-weighted imaging in any of the patients.
The researchers then used 1H-MR spectroscopy to measure the principal brain metabolites, including myo-Inositol (mI), Choline-containing compounds (Cho), Creatine and Phosphocreatine (Cr), and N-acetylaspartate.
All imaging was performed on a Magnetom Vision 1.5-tesla MR scanner (Siemens Medical Systems, Erlangen, Germany) using a single-voxel STEAM-20 sequence, TR of 1500 ms, TE of 20 ms, with 256 acquisitions and a spectroscopic volume of 2x2x2 cm.
"In spectroscopy there were no differences between Group 1 and Group 2, but patients with sustained minor motor disorders (Group 3) showed significantly higher values of mI/Cr." No significant differences were found in the other metabolites, Wenserski said, although Group 3 patients had slightly higher NAA/Cr and Cho/Cr ratios.
"Our conclusions are that metabolic changes appear long before conventional MRI or clinical examination show any abnormality, and they can be detected using MR spectroscopy," he said. "The significant increase in mI vs. Cr in patients with sustained MMD may reflect glial proliferation. As it is known that incipient MMD but not sustained minor motor disorders under certain circumstances can be reversible, further measurements will have to follow to figure out whether this reflects the point of no return."
By Eric Barnes
AuntMinnie.com staff writer
November 29, 2000
Related Reading
MR spectroscopy finds brain metabolite changes in
asymptomatic HIV patients, November 22, 2000
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