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

Abstract

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 ${}_{2\mathrm{/}3}$ -receptors in patients with BVF.

Methods:

D ${}_{2\mathrm{/}3}$ -receptor-PET using [ ${}^{18}$ F]fallypride and MRI examinations were performed in 12 BVF-patients and 13 healthy controls.

Results:

BVF-patients showed reduced D ${}_{2\mathrm{/}3}$ -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 ${}_{2\mathrm{/}3}$ -receptor availability in the middle/superior temporal gyrus (GTm/s). D ${}_{2\mathrm{/}3}$ -receptor availability in the right GTm/s and bilateral insula decreased with severity of symptoms. BVF-patients with oscillopsia showed reduced D ${}_{2\mathrm{/}3}$ -receptor availability in the right MT/MST and midbrain tectum.

Conclusions:

Reduced D ${}_{2\mathrm{/}3}$ -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 ${}_{2\mathrm{/}3}$ -receptor availability in the multisensory vestibular cortex in patients with prolonged illness suggests the occurrence of progressive changes in dopamine transmission.