Kaiserova M, Chudackova M, Prikrylova Vranova H, et al. - In several studies, patients with Parkinson disease (PD) were identified exhibiting reduced levels of 5-hydroxyindoleacetic acid (5-HIAA), the main serotonin metabolite. Researchers herein investigated its levels in atypical parkinsonian syndromes (APS).

• CSF was retrieved from 90 PD patients, 16 MSA patients, 26 progressive supranuclear palsy (PSP) patients, 11 corticobasal degeneration (CBD) patients, and 31 controls 5-HIAA and was assessed for 5-HIAA levels.

• PD and MSA patients showed decreased CSF 5-HIAA levels.

• PSP and CBS patients did not differ from those in the control group in terms of CSF 5-HIAA levels.

• Relative to PD patients, MSA patients had a tendency toward lower CSF 5-HIAA, however, the results did not reach statistical significance.

• More severe damage of the serotonergic system in synucleinopathies (PD, MSA) vs tauopathies (PSP, CBS) may explain these results.