Blunted response of caudal locus coeruleus to arousing stimuli in Parkinson's disease.

Caudal locus coeruleus neuromelanin signal is reduced in Parkinson’s disease, and this structural loss is linked to orthostatic hypotension and cognitive impairment.

• Why it matters: Noradrenergic degeneration in the locus coeruleus is tied to non-motor symptoms, but how rostro-caudal pathology affects arousal-related brain responses remains unclear.
• What they did: In a case-control study (71 people with PD ON medication; 40 matched controls), 7 T MTw MRI quantified caudal LC neuromelanin signal, and a subsample (30 PD; 27 controls) underwent 7 T fMRI to test caudal LC activation to arousing auditory and visual stimuli.
• The result: Caudal neuromelanin signal reduction was significant versus controls (P = 0.010) and correlated with orthostatic hypotension (P = 0.009) and cognitive impairment (P = 0.036); caudal LC activation to arousing stimuli was reduced in PD (P = 0.012), significant only in the ON state (P = 0.012; OFF trend P = 0.105).

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