Assessment of these square-wave jerks and diminished vertical saccades is especially useful for diagnosing progressive supranuclear palsy, because these movements set PSP patients apart from other parkinsonian patients. Difficulties with convergence (convergence insufficiency), where the eyes come closer together while focusing on something near, like the pages of a book, is typical. Because the eyes have trouble coming together to focus at short distances, the patient may complain of diplopia (double vision) when reading.A characteristic facial appearance known as “procerus sign”, with a wide-eye stare, furrowing of forehead with a frowning expression and deepening of other facial creases is diagnostic of PSP. Cause
The cause of PSP is unknown. 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 (rs1800547), has been linked to PSP. Nearly all people with PSP received a copy of that variant from each parent, but this is true of about two-thirds of the general population. Therefore, the H1 haplotype appears to be necessary but not sufficient to cause PSP. Other genes, as well as environmental toxins, are being investigated as other possible contributors to the cause of PSP.Additionally, the H2 haplotype, combined with vascular dysfunction, seems to be a factor of vascular progressive supranuclear palsy.Besides tauopathy, mitochondrial dysfunction seems to be a factor involved in PSP. Especially, mitochondrial complex I inhibitors (such as acetogenins and quinolines contained in Annonaceae, as well as rotenoids) are implicated in PSP-like brain injuries.
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 Parkinsons, frontotemporal dementia and Alzheimers. 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, disinhibition, anxiety, and dysphoria.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.