Parkinson's disease typically manifests after the age of 50 and rarely before the age of 40. It is a slowly progressing clinical condition. One of the primary symptoms of Parkinson's is tremor at rest, which is most commonly observed in the hands. These tremors generally occur at a rate of 3-7 beats per second and tend to disappear during purposeful movements and sleep. For example, the tremor vanishes when reaching for a glass. Another significant symptom is increased muscle tone, resulting in stiffness. When passive movement is attempted, resistance is encountered. For instance, trying to straighten a bent arm at the elbow is met with resistance, a phenomenon known as cogwheel rigidity. Another important symptom is the general slowness of movement. The gait becomes characterized by small steps, a lack of arm swinging, and a forward-leaning posture (anteflexion posture).
Additionally, patients may exhibit reduced facial expressions, speak in a monotonous and soft voice, and have difficulty sitting down and standing up. While not present in every case, other common symptoms include hypersalivation (excess saliva), seborrhea (oily skin and scalp), and constipation. Less common autonomic nervous system symptoms include impotence, incontinence, and orthostatic hypotension. Depression and dementia can also occur in the later stages. The disease's presentation can vary significantly from patient to patient. Some cases may predominantly feature tremors and muscle stiffness for many years, a condition known as hemiparkinsonism. Others may progress more rapidly with symptoms such as bradykinesia (slowness of movement), muscle rigidity, and postural instability, without prominent tremors.
Parkinson's disease can be primary or secondary to other conditions, including:
- Post-traumatic (following trauma)
- Certain medications affecting the nervous system
- Arteriosclerosis
- Toxins
- Post-encephalitis (inflammation of the brain)
Since Parkinson's disease arises from a deficiency of dopamine, a crucial neurotransmitter, treatment primarily involves medical therapy to replenish dopamine levels. Surgical options, such as a procedure called stereotactic thalamotomy, may also be considered in some cases.