Progressive supranuclear palsy

Progressive supranuclear palsy (PSP) (or the Steele-Richardson-Olszewski syndrome, after the Canadian physicians who described it in 1963 ) is a rare degenerative disorder involving the gradual deterioration and death of selected areas of the brain.

The sexes are affected approximately equally and there is no racial, geographical or occupational predilection. Approximately 6 people per 100,000 population have 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.

Prognosis
There is currently no effective treatment for PSP, although some of the symptoms can respond to nonspecific measures. The average age at symptoms onset is 63 and survival from that point averages 7 years with a wide variance.

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.

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.

Notable cases
Actor Dudley Moore, who suffered from progressive supranuclear palsy, increased public awareness of this disease. He died on March 27, 2002 from its complications.

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.

Reference

 * 1)  Richardson JC, Steele J, Olszewski J. Supranuclear ophthalmoplegia, pseudobulbar palsy, nuchal dystonia and dementia. A clinical report on eight cases of "heterogeneous system degeneration". Trans Am Neurol Assoc 1963;88:25-9. PMID 14272249.
 * 2)  Steele JC, Richardson JC, Olszewski J. Progressive supranuclear palsy: a heterogeneous degeneration involving brain stem, basal ganglia and cerebellum with vertical gaze and pseudobulbar palsy, nuchal dystonia and dementia. Arch Neurol 1964;10:333-359. PMID 14107684.