Spectrum of Non-Motor Symptoms in Parkinson's Disease

Abstract

Parkinson's disease is predominantly classified as a movement disorder. Beyond the textbook definition of rigidity, tremors, and bradykinesia, Parkinson's disease encompasses an entire entity of non-motor symptom complexes that can precede the motor features by many years. Despite their significant clinical importance, the awareness of non-motor symptoms is quite negligible. Sleep disorders, gastrointestinal dysfunction, olfactory disturbances, anxiety, and depressive episodes are some of the most common non-motor presentations. The wide-spread occurrence of olfactory symptoms and the low cost of the assessment, is favoring olfactory dysfunction as a potential biomarker in Parkinson's. Sleep disorders may manifest before the motor and autonomic symptoms and might be linked to concomitant sleeping disorders like insomnia, REM sleep disorders, restless leg syndrome, narcolepsy, or obstructive sleep apnea. Non-motor symptoms can deteriorate the quality of life in Parkinson's patients. Early detection of non-motor symptoms can help in the diagnosis of Parkinson's disease and can fairly improve the survival and prognosis of these patients.

Keywords: gastrointestinal disorders; non-motor symptoms; olfactory dysfunction; parkinson' s disease; sleep disorders.

Figure 1. The brain-gut axis in Parkinson’s disease. (A) Two-way communication between the brain and the gut via the vagus nerve. (B) Non-motor symptoms of Parkinson’s disease.

Figure 2. Braak staging steps 1-6. The pink shading represents the pattern of spread of alpha-synuclein from the olfactory region to the cortex.