PET studies and physiopathology of motor fluctuations in Parkinson's disease

We read with great interest the article by Kumar and colleagues recently published in Brain (Kumar et al ., 2003). We addressed the same problem in a somewhat different way, correlating pharmacological parameters with PET findings (Linazasoro et al ., 2004). Whereas we studied nine patients with Parkinson's disease and motor fluctuations on whom an apomorphine test and PET studies using [18F]fluorodihydroxyphenylalanine (Fdopa) and raclopride were performed, Kumar and colleagues studied differences in the motor response to a levodopa dose on both body sides of patients with asymmetrical Parkinson's disease. These authors conclude that the development of motor fluctuations is related to both levodopa treatment and dopaminergic terminal loss, which induce changes in presynaptic and postsynaptic mechanisms. This conclusion concurs with ours as well as with previously obtained data in clinical and pharmacological investigations. In spite of this, there are some relevant differences in the results, such as the one related to the latency of levodopa to reach its peak effect. Along with the magnitude …