Signs and symptoms of Parkinson's disease
Signs and symptoms of Parkinson's disease are varied. Parkinson's disease affects movement, producing motor symptoms. Non-motor symptoms, which include dysautonomia, cognitive and neurobehavioral problems, and sensory and sleep difficulties, are also common. When other diseases mimic Parkinson's disease, they are categorized as parkinsonism. Motor signs and symptoms. Four motor symptoms are considered cardinal signs in PD: slowness of movement (bradykinesia), tremor, rigidity, and postural instability. Typical for PD is an initial asymmetric distribution of these symptoms, where in the course of the disease, a gradual progression to bilateral symptoms  develops, although some asymmetry usually persists. Other motor symptoms include gait and posture disturbances such as decreased arm swing, a forward-flexed posture, and the use of small steps when walking; speech and swallowing disturbances; and other symptoms such as a mask-like facial expression or small handwriting are examples of the range of common motor problems that can appear. Cardinal signs. Four motor signs are considered cardinal in PD: tremor, rigidity, bradykinesia, and postural instability (also referred to as parkinsonism). ... immobile patients who become excited may be able to make quick movements such as catching a ball (or may  be able to suddenly run if someone screams "fire"). This phenomenon (kinesia paradoxica) suggests that patients with PD have intact motor programmes, but have difficulties accessing them without an external trigger, such as a loud noise, marching music, or a visual cue requiring them to step over an obstacle. Other motor symptoms. Other motor symptoms include: Neuropsychiatric. Parkinson's disease causes neuropsychiatric disturbances, which mainly include cognitive disorders, mood disorders, and behavior problems, and can be as disabling as motor symptoms. Since L-Dopa, the widely used drug in Parkinson's disease treatment, is decarboxylated by aromatic L-amino acid  decarboxylase (AADC), which is found in both dopaminergic and serotonergic neurons, it is possible for serotonergic neurons to convert L-Dopa into dopamine and generate excessive neuronal death by creating reactive oxygen species and quinoproteins. The association of serotonin with mood and cognition may explain some of the side-effects observed in patients treated with L-Dopa due to serotonin deficit. In most cases, motor symptoms predominate at early PD stages, while cognitive disturbances (such as mild cognitive impairment or dementia) emerge later. The onset of parkinsonism in PD relative to dementia is used as an arbitrary criterion to clinically  distinguish Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) using a ‘one-year rule’. Dementia onset within 12-months of or at the same time as motor dysfunctions qualified as DLB, whereas in PDD, parkinsonism had to precede dementia by at least one year. Cognitive disturbances occur even in the initial stages of the disease in some cases. A very high proportion of sufferers have mild cognitive impairment as the disease advances. Most common deficits in nondemented patients are: Deficits tend to aggravate with time, developing in many cases into dementia. A person with PD has a  six-fold increased risk of suffering it, and the overall rate in people with the disease is around 30%. Moreover, prevalence of dementia increases in relation to disease duration, going up to 80%. Dementia has been associated with a reduced quality of life in disease sufferers and caregivers, increased mortality, and a higher probability of moving to a nursing home. Cognitive problems and dementia are usually accompanied by behavior and mood alterations, although these kinds of changes are also more common in those patients without cognitive impairment than in the general population. Most frequent mood difficulties include: Obsessive–compulsive behaviors  (also known as Impulse-control disorders) such as craving, binge eating, hypersexuality, pathological gambling, punding, or others, can also appear in PD, and have been related to a dopamine dysregulation syndrome associated with the medications for the disease. Psychotic symptoms are common in PD, generally associated with dopamine therapy. Symptoms of psychosis, or impaired reality testing, are either hallucinations, typically visual, less commonly auditory, and rarely in other domains including tactile, gustatory, or olfactory, or delusions, that is, irrational beliefs. Hallucinations are generally stereotyped and without emotional content. Initially, patients usually have insight so that the hallucinations are benign in  terms of their immediate impact, but have poor prognostic implications, with increased risk of dementia, worsened psychotic symptoms, and mortality. Delusions occur in about 5-10% of treated patients, and are considerably more disruptive, being paranoid in nature, of spousal infidelity or family abandonment. Psychosis is an independent risk factor for nursing-home placement. Hallucinations can occur in parkinsonian syndromes for a variety of reasons. An overlap exists between PD and dementia with Lewy bodies, so that where Lewy bodies are present in the visual cortex, hallucinations may result. Hallucinations can also be brought about by excessive dopaminergic stimulation. Most  hallucinations are visual in nature, often formed as familiar people or animals, and are generally not threatening in nature. Some patients find them comforting; however, their caregivers often find this part of the disease most disturbing, and the occurrence of hallucinations is a major risk factor for hospitalisation. Treatment options consist of modifying the dosage of dopaminergic drugs taken each day, adding an antipsychotic drug such as quetiapine, or offering caregivers a psychosocial intervention to help them cope with the hallucinations. Sleep. Sleep problems can be worsened by medications for PD, but they are a core feature of the disease . Some common symptoms are: Gastrointestinal. Parkinson's Disease causes constipation and gastric dysmotility that is severe enough to endanger comfort and even health. A factor in this is the appearance of Lewy bodies and Lewy neurites even before these affect the functioning of the substantia nigra in the neurons in the enteric nervous system that control gut functions. Neuro-ophthalmological. PD is related to different ophthalmological abnormalities produced by the neurological changes. Among them are: