Assessment of cerebral dopamine D 2/3 formula-receptors in patients with bilateral vestibular failure.

BACKGROUND

Absence of peripheral vestibular input in bilateral vestibular failure (BVF) has been suggested to induce plastic reorganization in various brain regions. Among several neurotransmitters, dopamine is known to play a key role in cortico-striatal-sensorimotor processing. However, the role of dopamine in vestibular plasticity is scantly documented.

OBJECTIVE

Assessment of D 2/3 formula-receptors in patients with BVF.

METHODS

D 2/3 formula-receptor-PET using [18F]fallypride and MRI examinations were performed in 12 BVF-patients and 13 healthy controls.

RESULTS

BVF-patients showed reduced D 2/3 formula-receptor availability (approximately 40%) in the temporo-parieto-occipital cortex bilaterally, including the multisensory vestibular cortex and visual motion-sensitive areas (MT/MST), as well as in the striatum and the right thalamus. Longer illness duration was associated with bilaterally lower D 2/3 formula-receptor availability in the middle/superior temporal gyrus (GTm/s). D 2/3 formula-receptor availability in the right GTm/s and bilateral insula decreased with severity of symptoms. BVF-patients with oscillopsia showed reduced D 2/3 formula-receptor availability in the right MT/MST and midbrain tectum.

CONCLUSIONS

Reduced D 2/3 formula-receptor availability in multisensory vestibular cortical network areas and basal ganglia may indicate a receptor down-regulation due to the lack of peripheral vestibular input. The more pronounced decline in D 2/3 formula-receptor availability in the multisensory vestibular cortex in patients with prolonged illness suggests the occurrence of progressive changes in dopamine transmission.