The characteristic signs and symptoms of progressive supranuclear palsy include:

• A loss of balance while walking. A tendency to fall backward can occur very early in the disease.
• An inability to aim your eyes properly. You may have particular difficulty looking downward, or experience blurring and doubled vision. This difficulty with focusing the eyes can make some people spill food or appear disinterested in conversation because of poor eye contact.

Additional signs and symptoms of progressive supranuclear palsy vary and may mimic those of Parkinson's disease and dementia. These signs and symptoms worsen as the disease advances, and may include:

• Stiffness and awkward movements
• Falling
• Problems with speech and swallowing
• Sensitivity to light
• Sleep disturbances
• Loss of interest in pleasurable activities
• Impulsive behavior, possibly including laughing or crying for no reason
• Difficulties with memory, reasoning, problem-solving and decision-making
• Depression and anxiety
• A surprised or frightened facial expression, resulting from rigid facial muscles

The cause of progressive supranuclear palsy isn't known. The signs and symptoms of the disorder result from deterioration of cells in areas of your brain, especially those that help you control body movements (midbrain) and thinking (frontal lobe).

Researchers have found that the deteriorating brain cells of people with progressive supranuclear palsy have abnormal amounts of a protein called tau. Clumps of tau are also characteristic of other neurodegenerative disorders, such as Alzheimer's disease.

Rarely, progressive supranuclear palsy occurs within a family. But a genetic link isn't clear, and most people with progressive supranuclear palsy haven't inherited the disorder.

The only proven risk factor for progressive supranuclear palsy is age. The condition typically affects people around the age of 60, and is virtually unknown in people under the age of 40.

Complications of progressive supranuclear palsy result primarily from hindered muscle movements. These complications may include:

• Falling, which could lead to head injuries, fractures and other injuries.
• Difficulty focusing your eyes, which also can lead to injuries.
• Difficulty sleeping.
• Difficulty looking at bright lights.
• Problems swallowing, which can lead to choking or inhaling food or liquid into your airway (aspiration). Aspiration can develop into pneumonia, the most common cause of death in people with progressive supranuclear palsy.
• Impulsive behaviors — for example, standing up without waiting for assistance — which can lead to falls.

To avoid the hazards of choking, your doctor may recommend a feeding tube. To avoid injuries due to falling, a walker or a wheelchair may be used.