Parkinson disease is one of the most common progressive, degenerative neurologic disorders and is affecting approximately 1% of individuals older than 60 years. Anatomopathologic, Parkinson disease present two major findings: the loss of pigmented dopaminergic neurons in the substantia nigra (pars compacta) and the presence of Lewy bodies. The exact cause of Parkinson disease is still unknown and is believed that the disease appear due to a combination of genetic and environmental factors, but until now, no environmental cause of Parkinson disease has yet been proven. A known genetic mutation can be identified in approximately 10% of cases and in these cases the average age of onset is 50 years old.
Parkinson Disease Symptoms
Onset is often nonspecific, accompanied by depression and fatigue. 20% of patients experience an initial upper limb clumsiness. Typical onset of Parkinson disease is characterized by the appearance of a postural asymmetric tremor, which most commonly affects the upper limb.
Parkinson disease is characterized by three cardinal symptoms: akinesia or bradykinesia, tremor and extrapyramidal hypertonicity. Postural instability, which is the fourth cardinal symptom, occurs later, after several years of disease evolution.
Akinesia or bradykinesia means a slowness in movements or a lack of initiative in motor movements, loss of associated movements, such as the lack of upper limb swing during walking, the lack of gesticulation during speech. Akinesia is characterized by rapid fatigue in alternative or repetitive movements. Facial bradykinesia is characterized by decreased facial expression (hypomimia), like a mask and blinking rate is decreased. Bradykinesia also includes speech impairments (bradylalia), voice is becoming softer, less distinct or more monotonal. Patient may also present difficulties in swallowing. Bradykinesia can be suppressed by strong excitant factors, situation in which the patient presents paradoxical kinesia (is moving very fast). Another paradoxical aspect of Parkinson disease is represented by akathisia (characterized by unpleasant sensations of inner restlessness that manifests itself with an inability to sit still or remain motionless).
Hypokinesia differentiates itself from paralysis by the fact that is characterized by amplitude and speed redaction of movements, and not by muscle weakness. Hypokinesia develops slowly, being long time unnoticed and refers to the a slow execution of voluntary (for example, to lift an object), and automatic movements (for example, blinking, upper limb balance while walking). When is quite advanced, hypokinesia leads to functional disability, patient realize that has a motor problem and is possible to describe it as a paresis instead of describing the slow and low amplitude of its movements. Hypokinesia, as a manifestation of the motor system abnormalities, is dangerous only in advanced forms, when it may lead to severe immobilization of patient, with possibility of complications such as pneumonitis or pulmonary embolism.
Clinical manifestations of hypokinesia are the result of the combination of speed, frequency and amplitude reduction of spontaneous and automatic movements:
- Hypomimia: a reduced degree of facial expression, expressionless facies and decreased blink rate;
- Reduction of automatic movements: reduction of head movements and gesticulation during conversation, decreased amplitude of upper limb balance while walking, arms may remain fixed in semiflexion during walking;
- Impairments in repetitive movements: repetitive movements become slower and successive movement amplitude decreases (for example, micrographia – as patient is writing the letters become increasingly smaller);
- Difficulty in initiating movements: the ability to arise from a chair is affected or hesitation at the first step when the patient is initiating gait. Some patients with Parkinson disease have difficulty in performing two simultaneously motor acts (for example, to lift and move the hands);
- Motor blockage or freezing phenomenon is a sudden interruption of motor act, usually occurs while walking,being a characteristic for basal ganglia dysfunction. Freezing phenomenon may occur spontaneously or may be caused by certain circumstances such as the need to move through a crowded space or in patient attempt to navigate doorways. Emotional stimuli as anger and fear can also trigger the freezing phenomenon;
- Hypophonia is characterized by lower amplitude and inflection of voice. In severe cases difficult articulation of words results in a suppressed speech. Monotone voice, vocal tremor, poor articulation, variable speech rate, trouble with the initiation of speech, and stuttering-like qualities are all characteristic for Parkinson disease and sometimes may lead to an unintelligible speech.
Rigidity or extrapyramidal hypertonicity, is manifested by an increase in resistance to passive movements about a joint. Rigidity can be either smooth (lead pipe) or oscillating (cogwheeling). This resistance contributes to the slowness of movements and to decreased amplitude of associated movements. Is usually distributed on all muscle groups, but with a slight predominance on trunk and limb flexors, leading to a flexion posture of the body, which seen from lateral evokes the appearance of a question mark. Besides posture abnormalities, the patient loses compensatory reflexes necessary to restore balance. Posture influences walking, patients may take smaller steps and gait cadence is reduced.
Tremor in Parkinson disease is characterized by a rhythmic movements of the limbs and occurs when members are not engaged in voluntary action (resting tremor). Tremor is slowly and may be temporarily suspended or reduced by voluntary, active movements and reappears after a few seconds of rest. Typically, occurs when the patient is completely relaxed, first in one upper limb and then spreads slowly to the lower limbs and to the mandible. Very rarely, tremor may affect the head, but never affects the voice. Parkinsonian tremor amplitude is increased by stress, anxiety and fatigue. At the onset, tremor may be limited to one upper limb, later extending to the other hand and legs, and finally may include lips, jaw, tongue and very rarely the entire head.
Secondary clinical signs of Parkinson disease are represented by respiratory and sphincter impairment and constipation. Cognitive impairment can lead to dementia in 30% of cases. Sleep disorders are represented by daytime sleepiness associated with sleep-wake rhythm reversal. 50% -70% of patients with Parkinson disease develop depression. Personality changes may occur, patients become surly and selfish. Autonomic disorders can cause salivation, seborrhea, hypotension, and sensory disorders can cause paresthesias and limb pain.
Parkinson Disease Diagnosis
Parkinson disease is diagnose by the three cardinal symptoms: bradykinesia, tremor and rigidity. No laboratory or imaging explorations are required in patients with typical presentation of the disease. This patients are aged 55 years or older and present a slowly progressive and asymmetric resting tremor, bradykinesia or rigidity. Patients who do not present tremor should generally be considered for MRI evaluation to exclude brain lesions such as stroke, tumor, or demyelination.