Progressive Supranuclear Palsy (PSP) is a progressive parkinsonian disease that is often misdiagnosed as Parkinson's disease or Alzheimer's disease due to the overlap of its symptoms. PSP is the most common atypical parkinsonian disorder. It gets its name from the brain lesions that occur that control the eye movement.
Symptoms of PSP
Symptoms of PSP vary depending on the areas of the brain that are affected by the disease. Accordingly, there are variable clinical syndromes (presentations) of the disease.
Progressive supranuclear palsy: Richardson syndrome (PSP-RS)
This syndrome is the most common form of PSP that typically starts above age 50 with balance disturbances that lead to unexplained falls, often backward without loss of consciousness. Patients may develop gait instability with broad-based steps. Slowness (bradykinesia) and stiffness (rigidity) are Parkinsonian symptoms that occur in all disorders that mimick Parkinson's disease.
Slowness in daily activities is another feature of PSP. For example, PSP patients often take longer to eat, dress, and bathe. Those with Richardson syndrome tend to walk, turn and sit as a "block" because of stiffness in their trunk.They also usually develop slowness and stiffness more in their neck and trunk than in their limbs.
Most of the important symptoms of PSP that lead to its name are found in the eye movements. Vertical supranuclear gaze paresis is a movement limitation of the eyes that results in the inability to aim the eyes properly looking up and down, with the ocular reflexes preserved.
Light sensitivity (photophobia) is another symptom related of PSP that can be explained in part by a decrease in eye blinking. It can be associated with redness of the eyes and increased tearing and patients may need to wear sunglasses even indoors to avoid the irritating light. Due to the severely decreased blinking and diminished facial expressions (mask face), PSP patients may have an "astonished" or "surprise" face.
Patients with PSP-RS usually have some degree of apathy (loss of interest) and slowness of thought (bradyphrenia) associated with impaired attention. Other symptoms related to mental dysfunction are forgetfulness, difficulty in making decisions, impaired abstract thought, and occasionally disinhibition (executive dysfunction).
Dysarthria (poor articulation of speech) and dysphagia (swallowing) are also frequently affected relatively early in the course of the disease. The disease progresses relatively slowly, but PSP-RS patients have a shortened survival rate than in the general population.
Causes of PSP
There is strong evidence that a protein known as "tau" is abnormally aggregated in multiple types of brain cells (neurons, glia) in the brain leading to gradual malfunctioning and death of these cells; the common term is "tauopathy."
The tau aggregation and loss of cells occurs in several areas of the brain to include the subthalamic nucleus, striatum, substantia nigra, pontine tegmentum, oculomotor nucleus, medulla and dentate nucleus. The most specific features for PSP are presence of star-shaped astrocyt¬ic tangles that can be seen with light microscopy and that are stained with an¬tibodies to tau (figure).
PSP is considered a sporadic (not hereditary) disease; however, it has some genetic component. Environmental causes are being investigated, particularly by Dr. Litvan, who leads a multicenter, NIH funded case-control study to determine whether there are occupational and environmental risk factors for PSP.
Treatment for PSP
Management of PSP starts with the correct diagnosis, through clinical examination by a movement disorder specialist.
Multidisciplinary approach: Since PSP is a gradual progressive disease, it does not cause any sudden symptoms unless there are complications. Currently, the main goal of treating PSP is to prevent complications and improve the quality of life. The most important complications that need to be prevented are falls and chocking. Because of those dangers, a multidisci-plinary approach is essential in the management of PSP. Along with a movement disorder specialist, speech, language, and occupational thera¬pists and dietitians should be involved in the management plan.
Physical therapy: Working with a physical therapist can provide effective measures and techniques to avoid falls and their consequences. Physical therapists can provide tips on ways to improve walking and balance (i.e., using a weighted walker and using low-heal nonstick shoes).
U-Step weighted walker shown above
Speech therapy: Speech therapists evaluate the swallowing function (modified barium swallow study) and make sure to prevent chocking in the future by teaching specific techniques like head posturing and modifying diet. In addition, speech therapy can also improve voice projection.
Occupational therapy: Working with an occupational therapist is essential to promote and extend independence. Eating and reading both can be improved in patients with severe limitation of eye movement by using special glasses called prisms to remedy the difficulty of looking down.
Symptomatic treatment: Several drugs have been studied for the treatment of the motor aspects of the PSP. Unlike Parkinson's disease, treating PSP patients with levodopa usually has no significant benefits, however, if there is parkinsonism, it is important to administer it for at least a month at high doses to be sure of the response. Dopamine agonists do not add any additional benefits and may have more side effects.
Botulinum toxin injections: These can effectively be used to treat various forms of focal dystonia and eyelid drop. These injections may help to decrease the disability and improve quality of life; however there is always the risk of side effects.
Biological treatments: Treatments to slow disease progression are not available, but two recent studies in which UCSD investigators participated, evaluated if medications that inhibit one enzyme (GSK-3beta inhibitors: davunetide and tideglusib) could prevent the "cluttering" (aggregation) of tau could be of benefit. Research in this area is quite active.
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Research on PSP
Dr. Irene Litvan and her team are currently involved in a clinical trial with the goal of measuring the progression of PSP and CBD/CBS.