20th July 2023

Parkinson’s Disease (PD)

Pathophysiology

PD is a neurodegenerative disorder affecting the central nervous system. The onset is usually gradual, and as the disease progresses, both motor and non-motor symptoms occur. The area of the brain affected is the substantia nigra (midbrain,) where cell necrosis causes a reduction in dopamine levels. As dopamine plays a key role in regulating movement, this manifests as akinesia. It is thought that the degree of cell loss correlates clinically with the extent of akinesia. This leads to the accumulation of Lewy bodies (eosinophilic inclusion bodies) which contain ubiquitin and alpha-synuclein in the neurons.

PD has a variety of presentations which can be divided into motor (such as tremors and rigidity), and non-motor symptoms (cognitive, sleep disorder, and mood).

Signs and Symptoms

The symptoms usually noted initially are motor, although autonomic dysfunction, neuropsychiatric and sensory issues can present at any time in the disease (table 1). Symptoms known as prodromal features can be used to help diagnose PD; these include rapid eye movement, sleep disorders, hyposmia, typical motor symptoms and neuropsychiatric.

Table 1: Symptoms of Parkinson’s Disease

Diagnosis

PD tends to be a clinical diagnosis, made through an extensive history and examination, ensuring that all secondary causes of Parkinsonism have been excluded. This includes prodromal features such as rapid eye movement, sleep disorders, hyposmia, typical motor symptoms and neuropsychiatric symptoms. Neurological examination may show cardinal motor signs of bradykinesia with tremor, rigidity or both. Typically, the diagnosis should only be made by a specialist. NICE recommends neurologist referrals before medication is started. Diagnosis is not concrete; it should be reviewed throughout an individual’s illness, especially if it takes an atypical course.

Imaging: A DaT (Dopamine Transporter) scan can be useful if the diagnosis is unclear. This involves using small quantities of a radioactive drug to determine how much dopamine is available in the CNS.

Management

Medication

Before commencing treatment, the extent to which a patient’s symptoms are affecting their life should be ascertained. High risk of poly-pharmacy, goals of care and side effects of medications should be established. Dopamine receptor agonists, particularly in those with pre-existing impulse control disorders, history of alcohol or smoking should be used with caution, as this can cause these disorders to relapse.

Medication should not be withdrawn suddenly as this can cause acute akinesia or neuroleptic malignant syndrome. Timing of medication administration is integral to maintaining optimum control. It is important to ensure these medications remain on the same schedule whilst a patient is admitted. Common medications are shown in Table 2.

Table 2: Medications used in the management of Parkinson’s Disease

Other medications can be used to treat non-motor symptoms, such as modafinil for excessive daytime sleepiness and midodrine for postural hypotension.

Palliative Care

Important to involve palliative care and have early discussions of advanced care planning. Providing written and verbal information regarding progression and advanced care planning is also helpful to the patient, especially for decisions regarding artificial feeding. This helps patients make advanced directives.

Other

Other members of the MDT are important to involve, such as physiotherapists and occupational therapists, to ensure patients can safely mobilise and manage at home. Speech and language therapists can support with hypophonia and dysphagia.