The hereditary ataxias constitute a group of degenerative diseases that progress over years or decades. With principal pathology involving the cerebellum, dysarthria is an early feature of many of the ataxias. Positron emission tomography was used to study regional cerebral blood flow changes during speech production over a 21. month period in a group of seven right-handed subjects with hereditary ataxia (6 females and 1 male, 3 SCA1 and 4 SCA5, aged 38.3 ± 18.9. years). The decline in blood flow was greatest in cerebellar regions. In contrast, blood flow actually increased during speech production in the classic speech area (Broca's area) but not in its right-hemisphere homologue at the second evaluation. This increase in cortical flow may have been compensatory for cerebellar degeneration as speech intelligibility did not decline significantly during this period. Compensation was not complete, though, as syllable timing shifted in the direction of equal syllable duration, one of the characteristics of ataxic dysarthria. These results are consistent with previous functional imaging studies of ataxia demonstrating a pattern of brain activity that reflects both loss of function and relative compensation when clinical signs and symptoms are still mild. The combination of disease-relevant tasks, behavioral measurement, and functional imaging may provide insight into the early changes associated with neurodegenerative disease.
Bibliographical noteFunding Information:
Support was provided by NIDCD R01 DC007658, PO1NS33718, P20 MH57180, the Parkinson’s Disease Foundation, and the Bob Allison Ataxia Research Center. The helpful comments of Dr. D. Sidtis on earlier versions of this manuscript are gratefully acknowledged. The assistance of J. Anderson, D. Daly, M. Kneer, C. Farmer, D. Hamm, C. Erickson, K. Connaghan, M. Alberg, and J. Mahowald in scanning, data collection, acoustic analysis, and data processing is also greatfully acknowledged.
- Broca's area
- Cerebral blood flow
- Disease progression
- Functional imaging
- Positron emission tomography