Contrary to expectations, the presence of anti-basal ganglia antibodies in patients with Tourette's syndrome is not associated with brain structural changes, according to a report in the July issue of the Journal of Neurology, Neurosurgery & Psychiatry.
"I was relatively surprised to find that antibody-positive Tourette patients did not differ at all from patients without these auto-antibodies, both in gray matter volume and in the level of organization of white matter," Dr. David E. Martino told Reuters Health.
"We were expecting the presence of significant differences, particularly in the gray matter volume of caudate and putamen, more likely, given the long disease duration of these patients, in the direction of reduced volumes in antibody-positive patients," he explained.
Dr. Martino, from the University of Bari, Italy and colleagues assessed neural damage by performing whole-brain analysis using T1 and diffusion tensor imaging MRI-based methods in 22 Tourette's patients with and without detectable anti-basal ganglia antibodies (ABGAs) in the serum.
Clinical and demographic features did not differ significantly between the nine ABGA-positive and 13 ABGA-negative patients with Tourette's syndrome, the report indicates.
Voxel-based morphometric analysis detected no significant difference in gray matter density between ABGA-positive and ABGA-negative patients in the caudate nuclei, putamina, thalami, or frontal lobes, the authors report.
Similarly, diffusion tensor imaging showed no significant difference in white matter fractional anisotropy for any of the regions of interest.
"Certainly, the clinical and pathophysiological significance, if any, of ABGA in Tourette's syndrome and related disorders, and even in rarer conditions unequivocally related to streptococcal infections, such as Sydenham's chorea (St. Vitus's dance), remains undefined," Dr. Martino said.
"It is very important at this stage to be very cautious in interpreting the result of a clinical test for ABGA in Tourette's syndrome," he concluded. "Until clearer information is provided regarding their significance as a marker, physicians should not use the result of this test to modify their therapeutic approach towards Tourette patients."
"However," Dr. Martino added, "my opinion is that there remains a substantial amount of work to be done before definitely discarding the idea of a link between autoantibodies (and immune activation in general) and the mechanisms of disease in tic disorders and obsessive-compulsive disorder."
J Neurol Neurosurg Psychiatry 2008;79:820-822
