Progressive supranuclear palsy (PSP) is a late-onset degenerative disease involving the gradual deterioration and death of specific volumes of the brain. The condition leads to symptoms including loss of balance, slowing of movement, difficulty moving the eyes, and cognitive impairment. PSP may be mistaken for other neurodegenerative diseases such as Parkinson's, frontotemporal dementia and Alzheimer's. The cause of the condition is uncertain, but involves accumulation of tau protein within the brain. Medications such as levodopa and amantadine may be useful in some cases. PSP affects about six people per 100,000. The first symptoms typically occur at 60–70 years of age. Males are slightly more likely to be affected than females. No association has been found between PSP and any particular race, location, or occupation. Signs and symptoms The initial symptoms in two-thirds of cases are loss of balance, lunging forward when mobilizing, fast walking, bumping into objects or people, and falls. Dementia symptoms are also initially seen in about one in five cases of frontotemporal dementia. Other common early symptoms are changes in personality, general slowing of movement, and visual symptoms. The most common behavioural symptoms in patients with PSP include apathy, a lack of inhibition, anxiety, and a profound state of unease or dissatisfaction. Later symptoms and signs can include, but do not necessarily include dementia (typically including loss of inhibition and ability to organize information), slurring of speech, difficulty swallowing, and difficulty moving the eyes, particularly in the vertical direction. The latter accounts for some of the falls experienced by these patients, as they find it difficult to look up or down. 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. Some patients retain full cognitive function up to the end. The visual symptoms are of particular importance in the diagnosis of this disorder. Patients typically complain of difficulty reading due to the inability to look down well. The ophthalmoparesis experienced by these patients mainly concerns voluntary eye movement and the inability to make vertical saccades, which is often worse with downward saccades. Patients tend to have difficulty looking down (a downgaze palsy) followed by the addition of an upgaze palsy. This vertical gaze paresis will correct when the examiner passively rolls the patient's head up and down as part of a test for the