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Molecular imaging of movement disorders
#MMPMID27029029
Lizarraga KJ
; Gorgulho A
; Chen W
; De Salles AA
World J Radiol
2016[Mar]; 8
(3
): 226-39
PMID27029029
show ga
Positron emission tomography measures the activity of radioactively labeled
compounds which distribute and accumulate in central nervous system regions in
proportion to their metabolic rate or blood flow. Specific circuits such as the
dopaminergic nigrostriatal projection can be studied with ligands that bind to
the pre-synaptic dopamine transporter or post-synaptic dopamine receptors (D1 and
D2). Single photon emission computerized tomography (SPECT) measures the activity
of similar tracers labeled with heavy radioactive species such as technetium and
iodine. In essential tremor, there is cerebellar hypermetabolism and abnormal
GABAergic function in premotor cortices, dentate nuclei and ventral thalami,
without significant abnormalities in dopaminergic transmission. In Huntington's
disease, there is hypometabolism in the striatum, frontal and temporal cortices.
Disease progression is accompanied by reduction in striatal D1 and D2 binding
that correlates with trinucleotide repeat length, disease duration and severity.
In dystonia, there is hypermetabolism in the basal ganglia, supplementary motor
areas and cerebellum at rest. Thalamic and cerebellar hypermetabolism is seen
during dystonic movements, which can be modulated by globus pallidus deep brain
stimulation (DBS). Additionally, GABA-A receptor activity is reduced in motor,
premotor and somatosensory cortices. In Tourette's syndrome, there is
hypermetabolism in premotor and sensorimotor cortices, as well as hypometabolism
in the striatum, thalamus and limbic regions at rest. During tics, multiple areas
related to cognitive, sensory and motor functions become hypermetabolic. Also,
there is abnormal serotoninergic transmission in prefrontal cortices and
bilateral thalami, as well as hyperactivity in the striatal dopaminergic system
which can be modulated with thalamic DBS. In Parkinson's disease (PD), there is
asymmetric progressive decline in striatal dopaminergic tracer accumulation,
which follows a caudal-to-rostral direction. Uptake declines prior to symptom
presentation and progresses from contralateral to the most symptomatic side to
bilateral, correlating with symptom severity. In progressive supranuclear palsy
(PSP) and multiple system atrophy (MSA), striatal activity is symmetrically and
diffusely decreased. The caudal-to-rostral pattern is lost in PSP, but could be
present in MSA. In corticobasal degeneration (CBD), there is asymmetric, diffuse
reduction of striatal activity, contralateral to the most symptomatic side.
Additionally, there is hypometabolism in contralateral parieto-occipital and
frontal cortices in PD; bilateral putamen and cerebellum in MSA; caudate,
thalamus, midbrain, mesial frontal and prefrontal cortices in PSP; and
contralateral cortices in CBD. Finally, cardiac sympathetic SPECT signal is
decreased in PD. The capacity of molecular imaging to provide in vivo time
courses of gene expression, protein synthesis, receptor and transporter binding,
could facilitate the development and evaluation of novel medical, surgical and
genetic therapies in movement disorders.
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