Hot topics - Parkinson's disease
With the MRCGP exams in mind, Dr Mona Kular takes a look at Parkinson’s Disease
With the MRCGP exams in mind, Dr Mona Kular takes a look at Parkinson's Disease
What is Parkinson's Disease?
Parkinson's Disease is a neurodegenerative condition resulting from a deficiency of dopamine producing cells within the substantia nigra in the midbrain. Symptoms usually arise once dopamine levels have decreased by approximately 80% . The exact aetiology is currently unknown but there is ongoing research into genetic and environmental factors. The prevalence of Parkinson's Disease is about 0.2%, rising to around 4% of those over the age of 80 .
Diagnosis and Symptoms
Diagnosis is predominantly clinical and based on a set of core symptoms :
• Resting tremor: Best picked up with the patients' hands resting in their lap, but needs to be differentiated from postural, essential or intention tremor.
• Rigidity: Often on passive movements of the limbs
• Bradykinesia General slowing of movements and difficulty initiating movements
• Postural instability Difficulties with balance and co-ordination
Early symptoms may be subtle and/or unilateral, progressing with time to become more prominent. It is acknowledged however, that diagnosis is difficult - particularly in elderly patients who may have tremor or postural instability for other reasons. The diagnostic error in the community is somewhere in the region of 47%, but significantly lower in the specialist setting. For this reason, NICE recommends that patients with suspected Parkinson's Disease should be referred to a specialist untreated within six weeks for diagnosis, and that this should be based on the UK Parkinson's Disease Society Brain Bank Criteria which uses inclusion, exclusion and supportive criteria. However, even in the specialist setting, differentiating Parkinson's Disease from essential tremor can be difficult and in these situations NICE advocates the use of single photon emission computed tomography (SPECT) to aid diagnosis .
It is important to remember that Parkinson's Disease often also manifests in non-motor symptoms; mental health problems such as psychosis, dementia and especially depression are not uncommon, along with sleep disturbances and autonomic disturbances. Particularly in the primary care setting, non-motor symptoms should be watched for and a low threshold adopted in the diagnosis of depression which is frequently missed.
First line pharmacological therapies used in early Parkinson's Disease, once motor functions are affected on a daily basis, include:
• Levodopa: Used at the lowest dose possible to maintain good function
• Dopamine agonists: Non ergot derived, e.g. bromocriptine, preferred to ergot derived
• MAO-B inhibitors: Early use decreases time to ‘end of dose' effect, e.g. Selegeline
In the later stages of Parkinson's Disease, the following are often added in:
• Dopamine agonists
• MAO-B inhibitors
• COMT inhibitors
A limited cohort of patients in whom motor symptoms are not controlled by best medical treatment and who are otherwise fit, will be eligible for surgical intervention.
Antiparkinsonian medication should not be withdrawn abruptly, as this risks causing an acute akinesia or even neuroleptic malignant syndrome. This can also be caused through disorders of absorption, such as gastroenteritis, so it is important to be vigilant.
It has also become increasingly clear that those with Parkinson's Disease benefit from regular access to a specialised multi-disciplinary team, including specialist nurses, physiotherapists, occupational therapists and speech and language therapists.
Parkinson's Disease Society, www.parkinsons.org.uk
2 Clinical Review, Parkinson's Disease, C E Clarke. BMJ 2007;335:441-445
3 National Institute of Neurological Disorders and Stroke, www.ninds.nih.gov
4 NICE Guidelines, Parkinson's Disease. June 2006.
Dr Mona Kular is a GP in a registrar in Nottingham