Response to levodopa treatment in dopa-responsive dystonia.
BACKGROUND
Dopa-responsive dystonia (DRD) is similar to Parkinson disease in that both disorders have impaired dopamine synthesis and respond to levodopa treatment. Dopa-responsive dystonia differs in that dopamine storage is intact in contrast to Parkinson disease in which it is markedly reduced.


OBJECTIVE
To examine the short- and long-duration responses to levodopa dosing in subjects with DRD.


METHODS
The response to brief infusions of levodopa was examined in 4 subjects with DRD and the effects of withdrawal of levodopa for 3 to 7 days studied in the 3 subjects receiving long-term levodopa therapy. Motor function was measured with tapping speed, Unified Parkinson's Disease Rating Scale motor score, and global dystonia score.


RESULTS
The short-duration response to levodopa dosing seems to develop more slowly and persists longer in subjects with DRD than in subjects with Parkinson disease. Withdrawal of levodopa leads to a gradual decline in tapping speed and reemergence of dystonia over several days, similar to the rate of decay of motor function in Parkinson disease. The short- and long-duration responses were not clearly differentiated in DRD.


CONCLUSIONS
This pilot study suggests that retained dopamine storage in DRD may prolong the short-duration response and blur the distinction of the short- and long-duration responses. The decline in motor function in DRD on withdrawal of long-term levodopa therapy resembles that in Parkinson disease, suggesting that a long-duration response, if it exists in DRD, is unrelated to dopamine storage.
Nutt
J G
JG
Department of Neurology, OP 32, Oregon Health Sciences University, 3181 SW Sam Jackson Park Rd, Portland, OR 97201-3098, USA.
Nygaard
T G
TG
D000328:Adult; D000978:Antiparkinson Agents / Q000627:therapeutic use*; D004298:Dopamine / Q000378:metabolism; D004421:Dystonia / Q000188:drug therapy / Q000503:physiopathology; D020821:Dystonic Disorders / Q000188:drug therapy* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D020734:Parkinsonian Disorders / Q000188:drug therapy* / Q000503:physiopathology; D010865:Pilot Projects
D000978:Antiparkinson Agents; D007980:Levodopa; D004298:Dopamine