Diagnosis - Early Symptoms & Early Diagnosis

Reviewed by: HU Medical Review Board | Last reviewed: March 2017

Parkinson’s disease (PD) is difficult to diagnosis, particularly in its early stages because the symptoms of other neurologic disorders can be similar to those found in PD.

Current diagnosis is made through the presence of motor symptoms, including bradykinesia (slowed movement and loss of spontaneous movement), muscular rigidity, a resting tremor, and postural instability (balance issues).1

Accurately diagnosing PD is important so that patients can receive the proper treatment and advice regarding care. In addition, diagnosing PD early is important because treatments such as levodopa/carbidopa are more effective when administered early on in the disease. Non-pharmacologic treatments, such as increased exercise, are also easier to perform in the early stages of PD and may help slow down disease progression.1

Recognizing early symptoms of Parkinson's

The identification of pre-motor symptoms is key to early detection of PD. Early symptoms of PD may include:

  • Gastrointestinal difficulties, like constipation and slowed movement of food from the stomach into the intestines (gastroparesis)
  • Reduced sense of smell, also known as hyposmia
  • Sleep problems, including insomnia, REM sleep behavior disorder (acting out dreams while asleep), restless legs syndrome and excessive daytime sleepiness
  • Sexual dysfunction, like erectile dysfunction in men, poor lubrication in women, or difficulty achieving orgasm in both men and women
  • Mood disorders, like depression or anxiety1

Braak’s hypothesis on how Parkinson’s disease begins

Braak’s hypothesis, named for professor Heiko Braak, MD, who outlined the theory in 2003, suggests that rather than beginning in the brain, Parkinson’s disease begins in the periphery of the body. Braak’s hypothesis proposes that the earliest signs of PD are found in the gut and the olfactory bulb, an area of the brain involved in the sense of smell.2-4

The accumulation of the protein alpha-synuclein (a key characteristic of PD, also called Lewy bodies) is believed to begin in the gastrointestinal tract or the olfactory bulb before progressing to other areas of the brain. After the aggregates of alpha-synuclein have formed, they appear to be capable of growing and spreading from nerve cell to nerve cell across the brain.2-4

The appearance of alpha-synuclein aggregates coincides with the appearance of symptoms: alpha-synuclein aggregates in the brainstem (area of the brain near the base of skull) correlates with the onset of motor symptoms. Appearance of alpha-synuclein aggregates in the cortex (the outer layer of the brain that controls higher thought processes and cognition) correlates with dementia and cognitive dysfunction.2-4

Defining populations at risk for Parkinson’s disease

One of the areas of research that aims to aid in the early detection and treatment of PD is seeking to identify “biomarkers”—protein or chemicals in the blood, urine, or cerebrospinal fluid that reliably help diagnose PD, particularly at the early stage. For example, a recent study detected aggregates of alpha-synuclein in the cerebrospinal fluid. These aggregates were found in PD patients but not patients with other neurologic disorders. Many research studies are attempting to identify new biomarkers, particularly those that may even predict whether someone will develop PD over time.5

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