Progressive supranuclear palsy

# Overview
Progressive supranuclear palsy (PSP) (or the Steele-Richardson-Olszewski syndrome, after the Canadian physicians who described it in 1963 ) is a rare brain disorder that causes serious and permanent problems with control of gait and balance. The most obvious sign of the disease is an inability to aim the eyes properly, which occurs because of lesions in the area of the brain that coordinates eye movements. Some patients describe this effect as a blurring. PSP patients often show alterations of mood and behavior, including depression and apathy as well as progressive mild dementia. It must be emphasized that the pattern of signs and symptoms can be quite different from person to person. The symptoms of PSP are caused by a gradual deterioration of brain cells in a few tiny but important places at the base of the brain, in the region called the brainstem. PSP is often misdiagnosed because some of its symptoms are very much like those of Parkinson's disease, Alzheimer's disease, and more rare neurodegenerative disorders, such as Creutzfeldt-Jakob disease. The key to establishing the diagnosis of PSP is the identification of early gait instability and difficulty moving the eyes, the hallmark of the disease, as well as ruling out other similar disorders, some of which are treatable. Although PSP gets progressively worse, no one dies from PSP itself.
The sexes are affected approximately equally and there is no racial, geographical or occupational predilection. Approximately 6 people per 100,000 population have PSP.

# Pathophysiology
The affected brain cells are both neurons and glial cells.  The neurons display neurofibrillary tangles, which are clumps of tau protein, a normal part of brain cell's internal structural skeleton.
The principal areas of the brain affected are:
- the basal ganglia, particularly the subthalamic nucleus, substantia nigra and globus pallidus;
- the brainstem, particularly the portion of the midbrain where "supranuclear" eye movement resides;
- the cerebral cortex, particularly that of the frontal lobes;
- the dentate nucleus of the cerebellum;
- and the spinal cord, particularly the area where some control of the bladder and bowel resides.

# Genetics
Fewer than 1% of those with PSP have a family member with the same disorder.  A variant in the gene for tau protein called the H1 haplotype, located on chromosome 17, has been linked to PSP.  Nearly all people with PSP received a copy of that variant from each parent, but this is true of only about two-thirds of the general population.  Therefore, the H1 haplotype appears to be necessary but not sufficient to cause PSP.  Other genes and environmental toxins are being investigated as other contributors to the cause of PSP.

# Symptoms and signs
The initial symptom in two-thirds of cases is loss of balance and falls.  Other common early symptoms are changes in personality or general slowing of movement.
Later symptoms and signs are dementia (typically including loss of inhibition and ability to organize information), slurring of speech, difficulty swallowing, and difficulty moving the eyes, most specifically in the downward direction.
Some of the other signs are poor eyelid function, contracture of the facial muscles, a backward tilt of the head with stiffening of the neck muscles, sleep disruption, urinary incontinence and constipation.

# Differential diagnosis
PSP is frequently misdiagnosed as Parkinson's disease because of the slowed movements and gait difficulty, or as Alzheimer's Disease because of the behavioral changes. It is one of a number of diseases collectively referred to as Parkinson plus syndromes.

# Treatment
There is currently no effective treatment for PSP, although scientists are searching for better ways to manage the disease. In some patients the slowness, stiffness, and balance problems of PSP may respond to antiparkinsonian agents such as levodopa, or levodopa combined with anticholinergic agents, but the effect is usually temporary. The speech, vision, and swallowing difficulties usually do not respond to any drug treatment.. Another group of drugs that has been of some modest success in PSP are antidepressant medications. The most commonly used of these drugs are Prozac, Elavil, and Tofranil. The anti-PSP benefit of these drugs seems not to be related to their ability to relieve depression. Non-drug treatment for PSP can take many forms. Patients frequently use weighted walking aids because of their tendency to fall backward. Bifocals or special glasses called prisms are sometimes prescribed for PSP patients to remedy the difficulty of looking down. Formal physical therapy is of no proven benefit in PSP, but certain exercises can be done to keep the joints limber. A surgical procedure, a gastrostomy, may be necessary when there are swallowing disturbances. This surgery involves the placement of a tube through the skin of the abdomen into the stomach (intestine) for feeding purposes.

# Prognosis
PSP gets progressively worse but is not itself directly life-threatening. It does, however, predispose patients to serious complications such as pneumonia secondary to difficulty in swallowing (dysphagia). The most common complications are choking and pneumonia, head injury, and fractures caused by falls. The most common cause of death is pneumonia. With good attention to medical and nutritional needs, however, most PSP patients live well into their 70s and beyond.
The average age at symptoms onset is 63 and survival from that point averages 7 years with a wide variance.

# Support groups
Several international organizations serve the needs of patients with PSP and their families and support research.  The Society for PSP ("CurePSP") is based in the US and the PSP Association is based in the UK.