Functional brain imaging in combined motor and sleep disorders

The pathophysiology of sleep-related motor diseases and sleep dysfunction in movement disorders is widely unknown as yet. Functional brain imaging, in particular radioisotope and magnetic resonance techniques, are powerful tools to investigate possible pathomechanisms of combined sleep and motor dysregulation. In patients with Restless legs syndrome (RLS), only a subtle striatal dopamine deficit was found in PET and SPECT despite a good treatment effect of dopaminergic drugs. Functional MRI suggested a central generator of periodic limb movements during sleep (PLMs) in RLS. In contrast, a marked striatal dopamine depletion was demonstrated in patients with REM sleep behaviour disorder (RBD) as the base for the clinical and nosological overlap of RBD with parkinsonian disorders. PET and SPECT also suggested that sleep abnormalities in Parkinson's disease (PD), such as REM sleep diminution or increased PLMs, are indirect manifestations of the primary striatal dopamine deficiency.