Synaptic Changes in Parkinson Disease Assessed with in vivo Imaging

Ann Neurol. 2020 Mar;87(3):329-338. doi: 10.1002/ana.25682. Epub 2020 Feb 5.


Objective: Parkinson disease is characterized by motor and nonmotor symptoms, reduced striatal dopamine signaling, and loss of dopamine neurons in the substantia nigra. It is now known that the pathological process in Parkinson disease may begin decades before the clinical diagnosis and include a variety of neuronal alterations in addition to the dopamine system.

Methods: This study examined the density of all synapses with synaptic vesicle glycoprotein 2A (SV2A) in Parkinson disease subjects with mild bilateral disease (n = 12) and matched normal controls (n = 12) using in vivo high-resolution positron emission tomographic imaging as well as postmortem autoradiography in an independent sample with Parkinson disease (n = 15) and normal controls (n = 13) in the substantia nigra and putamen.

Results: A group-by-brain region interaction effect (F10, 22 = 3.52, p = 0.007) was observed in the primary brain areas with in vivo SV2A binding. Post hoc analyses revealed that the Parkinson disease group exhibited lower SV2A in the substantia nigra (-45%; p < 0.001), red nucleus (-31%; p = 0.03), and locus coeruleus (-17%; p = 0.03). Exploratory analyses also revealed lower SV2A binding in clinically relevant cortical areas. Using autoradiography, we confirmed lower SV2A in the substantia nigra (-17%; p < 0.005) and nonsignificant findings in the putamen (-4%; p = 0.06).

Interpretation: This work provides the first evidence of synaptic loss in brainstem nuclei involved in the pathogenesis of Parkinson disease in living patients. SV2A imaging holds promise for understanding synaptic changes central to the disease. Ann Neurol 2020;87:329-338.

MeSH terms

  • Autoradiography
  • Case-Control Studies
  • Early Diagnosis*
  • Female
  • Functional Neuroimaging
  • Humans
  • Locus Coeruleus / pathology
  • Male
  • Membrane Glycoproteins / metabolism
  • Middle Aged
  • Nerve Tissue Proteins / metabolism
  • Parkinson Disease / diagnostic imaging*
  • Parkinson Disease / pathology*
  • Positron-Emission Tomography
  • Putamen / metabolism
  • Putamen / pathology*
  • Pyridines
  • Pyrrolidines
  • Red Nucleus / pathology
  • Substantia Nigra / metabolism
  • Substantia Nigra / pathology*
  • Synapses / pathology*


  • (11c)-ucb
  • Membrane Glycoproteins
  • Nerve Tissue Proteins
  • Pyridines
  • Pyrrolidines
  • SV2A protein, human