Parkinson's disease

Definition

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterised by the loss of dopamine-producing neurons in the substantia nigra of the brain. It primarily affects movement, leading to symptoms such as tremors, rigidity, bradykinesia (slowness of movement), and postural instability.

Aetiology

The exact cause of Parkinson's disease is unknown. It is believed to result from a combination of genetic and environmental factors. Several genes have been associated with an increased risk of PD, and exposure to toxins such as pesticides may also contribute to the development of the disease.

Pathophysiology

Parkinson's disease is characterised by the degeneration of dopaminergic neurons in the substantia nigra pars compacta. This leads to a deficiency of dopamine in the striatum, a key region involved in regulating movement. The loss of dopamine disrupts the balance of neurotransmitters, impairing the motor control pathways and resulting in the characteristic symptoms of PD.

Risk factors

Age (risk increases with age, typically affecting individuals over 60)
Male gender
Family history of Parkinson's disease
Exposure to environmental toxins (e.g., pesticides, herbicides)
History of traumatic brain injury

Signs and Symptoms

Tremor (typically a resting tremor, often starting in one hand)
Bradykinesia (slowness of movement)
Rigidity (stiffness in the limbs and trunk)
Postural instability (impaired balance and coordination)
Shuffling gait
Reduced facial expression (hypomimia)
Micrographia (small, cramped handwriting)
Speech changes (soft or slurred speech)
Non-motor symptoms (e.g., depression, constipation, sleep disturbances)

Red Flags

Rapid progression of symptoms
Early onset of symptoms (before age 50)
Presence of atypical features (e.g., early severe dementia, hallucinations, significant autonomic dysfunction)
Absence of response to dopaminergic therapy

Investigations

Clinical history and neurological examination focusing on motor symptoms
Response to levodopa treatment (improvement in symptoms supports the diagnosis)
DaTscan (dopamine transporter scan) to assess dopamine deficiency in the brain
MRI or CT scan to rule out other causes of symptoms (e.g., stroke, brain tumour)
Blood tests to exclude other conditions that may mimic Parkinson's disease (e.g., thyroid dysfunction, liver disease)

Management

Primary Care Management:

Referral to a neurologist for confirmation of diagnosis and initiation of treatment
Pharmacological treatment with dopaminergic medications (e.g., levodopa, dopamine agonists) to manage motor symptoms
Non-pharmacological interventions, including physiotherapy, occupational therapy, and speech therapy
Education and support for patients and caregivers, including information about the disease and its progression
Regular monitoring and follow-up to assess treatment efficacy and manage side effects
Referral to a specialist if there are complications or atypical features

Example Management for Parkinson's Disease:

A patient diagnosed with Parkinson's disease may be started on levodopa combined with carbidopa to improve motor symptoms. The initial dose might be levodopa 100 mg/carbidopa 25 mg three times daily, titrating up based on response and tolerability. Regular follow-up with a neurologist is essential to adjust medication, manage side effects, and monitor disease progression. Non-pharmacological treatments such as physiotherapy to maintain mobility and speech therapy to address communication difficulties should also be considered.

References:

NICE. (2017). Parkinson’s Disease in Adults: Diagnosis and Management. Retrieved from https://www.nice.org.uk/guidance/ng71
NHS. (2023). Parkinson’s Disease. Retrieved from https://www.nhs.uk/conditions/parkinsons-disease/
Parkinson's UK. (2023). What is Parkinson's? Retrieved from https://www.parkinsons.org.uk/information-and-support/what-parkinsons
O'Sullivan, S. B., & Schmitz, T. J. (2016). Physical Rehabilitation. 6th ed. F.A. Davis Company.
Ropper, A. H., & Samuels, M. A. (2019). Adams and Victor's Principles of Neurology. 11th ed. McGraw-Hill Education.