Parkinson’s Disease

Parkinson’s disease is a motor disorder characterized by difficulty in initiating movements, slowness of movement, and rigidity. Patients often have a masked facial expression, muscle tremors, poor balance, a flexed posture and a shuffling gait. Like Alzheimer’s disease, Parkinson’s disease is a progressive brain illness whose risk increases with advancing age.. The incidence of Parkinson’s disease is about 1% at age 65 and about 5% at age 85.

The symptoms of Parkinson’s disease result from the death of neurons in a midbrain nucleus called substantia niagra. These neurons normally release dopamine from their synaptic terminals in the basal nuclei. The degeneration of dopamine neurons is associated with the accumulation of protein aggregates containing α synuclein, a protein typically found in presynaptic nerve terminals.

Most cases of Parkinson’s disease lack a clearly identifiable cause. However, the consensus among scientists who study the disease is that it results from a combination of environmental and genetic factors. For example, some families with an increased incidence of Parkinson’s disease have a mutated form of the gene for α synuclein. One hypothesis is that changes in the structure of α synuclein cause dopamine neurons in the substantia niagra to become susceptible to oxidative cell damage.

At present there is no cure for Parkinson’s disease although various approaches are used to manage the symptoms,including brain surgery, deep brain stimulation, and drugs such as L-dopa, a dopamine precursor that can cross the blood-brain barrier. One potential cure is to implant dopamine secreting neurons,either in the substantia niagra or in the basal ganglia. Embryonic stem cells can be stimulated or genetically engineered to develop into dopamine-secreting neurons.

References:

Davidson's Principles and Practise of Medicine,23rd edition

Lange clinical neurology and neuroanatomy, Aaron L Berkowitz