Parkinson's Disease - Diagnosis

In the absence of an alternative diagnosis, Parkinson's disease can be diagnosed if at least three of its four main manifestations are present: resting tremor, rigidity (increased muscle resistance throughout the entire range of passive movement in a particular joint of the limb), often of the "cogwheel" type, bradykinesia and postural instability. Weakened facial expressions (mask-like face), micrographia, impaired fine motor coordination, hunched (flexor) posture, and the "freezing" phenomenon, which is characterized by a sudden blockade of movement and is often provoked by fear when a sudden stimulus appears, are also often observed.

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Differential diagnosis of Parkinson's disease

Parkinson's disease should be differentiated from other diseases that cause parkinsonism syndrome, including drug-induced parkinsonism, progressive supranuclear palsy, multiple system atrophy (striatonigral degeneration, Shy-Drager syndrome), diffuse Lewy body disease, corticobasal degeneration. Every patient with parkinsonism should first be asked whether he or she is taking drugs that block dopamine receptors, including neuroleptics (eg, chlorpromazine and haloperidol), drugs to treat nausea and weakened gastric motility (eg, prochlorperazine or metoclopramide). Reserpine can also cause parkinsonism.

Other diseases should be considered first when the patient does not have a classic resting tremor. In progressive subnuclear palsy (PNP), postural reflexes are usually impaired early, which is manifested by frequent unexplained falls. Progressive subnuclear palsy should also be suspected in cases of impaired voluntary saccades, especially in the vertical plane, as well as in cases where rigidity in the neck and trunk is expressed to a much greater extent than in the limbs. Striatonigral degeneration and Shy-Drager syndrome are clinical variants of the same disease - multiple system atrophy (MSA), which is characterized by specific pathomorphological changes, but can manifest itself in different clinical syndromes. Although some patients with multisystem atrophy have resting tremor, the frequent presence of spasticity in the lower limbs, extensor plantar signs, orthostatic hypotension, and sometimes ataxia distinguish them from patients with Parkinson's disease. Corticobasal degeneration often presents with apraxia and the "alien limb" phenomenon, which is characterized by the arm (less often the leg) spontaneously assuming unusual postures and making involuntary movements. Diffuse Lewy body disease is usually characterized by dementia with a tendency to visual hallucinations, but sometimes manifests as parkinsonism, which can be resistant to levodopa drugs. The complete absence of resting tremor often indicates that the patient does not have Parkinson's disease, but one of the above diseases. A more reliable diagnostic sign of Parkinson's disease is the high effectiveness of dopaminergic drugs.

Although symptomatic therapy is quite effective in the early stages of Parkinson's disease, it does not affect the process of neuronal death in the substantia nigra, which continues steadily and leads to disease progression. As Parkinson's disease progresses, late complications appear, which are largely provoked by the therapy itself. These include drug-induced dyskinesias and the "on-off" phenomenon, characterized by rapid fluctuations between a state of immobility due to an increase in parkinsonism symptoms and a more mobile state, usually accompanied by dyskinesias. There are three main types of dyskinesia, the most common of which are "peak dose" dyskinesias. These movements are usually choreoathetoid in nature, intensified by excitement, but rarely cause significant discomfort to the patient. Another type of dyskinesia is biphasic dyskinesias - at the beginning and end of the action of the next dose of dopaminergic agent. Biphasic dyskinesias cause much more discomfort to the patient than "peak dose" dyskinesias and are usually ballistic or dystonic in nature. They are often more severe in the afternoon. The third type of dyskinesia - dyskinesia of the "off" period - occurs against the background of exhaustion of the action of the next dose and the intensification of Parkinsonism symptoms, they are usually represented by painful contraction of the lower limbs.

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