Background: Various cerebrospinal fluid (CSF) biomarkers are studied in Parkinson’s disease (PD) and atypical parkinsonian syndromes (APS). Several studies found reduced 5-hydroxyindoleacetic acid (5-HIAA), the main serotonin metabolite, in PD. There is little evidence regarding its levels in APS.
Methods: We measured 5-HIAA in the CSF of 90 PD patients, 16 MSA patients, 26 progressive supranuclear palsy (PSP) patients, 11 corticobasal degeneration (CBD) patients, and 31 controls. We also compared the values in depressed and non-depressed patients.
Results: There was a statistically significant difference in CSF 5-HIAA in PD and MSA compared to the control group (median in PD 15.8 µg/l, in MSA 13.6 µg/l vs. 24.3 µg/l in controls; P=0.0008 in PD, P=0.006 in MSA). There was no statistically significant difference in CSF 5-HIAA in PSP and CBD compared to the control group (median in PSP 22.7 µg/l, in CBD 18.7 µg/l vs. 24.3 µg/l in controls; P= 1 in both PSP and CBD). CSF 5-HIAA levels were lower in PD patients with depression compared to PD patients without depression (median 8.34 vs. 18.48, P<0.0001).
Conclusions: CSF 5-HIAA is decreased in PD and MSA. The CSF 5-HIAA levels in PSP and CBS did not differ from those of the control group. There was a tendency toward lower CSF 5-HIAA in MSA than in PD, however, the results did not reach statistical significance. These results may be explained by more severe damage of the serotonergic system in synucleinopathies (PD, MSA) than in tauopathies (PSP, CBS).