A type of observational study that compares two groups of people (those with the disease or condition under study (cases) and people who do not have the disease or condition (controls)) and retrospectively examines their prior exposure to a particular factor of interest.

Impaired coordination of voluntary movements (ataxia) due to cerebellar dysfunction.

The fluid that surrounds and fills the brain and spinal cord, protecting the brain, providing nourishment for cells, and removing waste.

A research study conducted in humans to evaluate the safety, efficacy, and optimal use of medical interventions such as drugs, devices, or therapies.

The maximum (peak) concentration of a drug found in blood or plasma after the administration.

The presence of multiple pathologies occurring at the same time in the same person. In PSP, co-pathologies are common and may include additional neurodegenerative changes, such as Alzheimer’s disease-related amyloid plaques, Lewy body pathology and age-related cerebrovascular changes, which may contribute to clinical variability and complicate diagnosis.

The co-occurrence of multiple disorders in the same individual, which can influence the diagnosis, treatment, or prognosis of some conditions.

Neurodegenerative syndrome combining movement disorder signs (rigidity, apraxia, dystonia, myoclonus) with cortical signs (apraxia, sensory loss, alien limb).

Descriptive analyses that estimate the overall costs associated with a disease. These studies quantify the economic burden by measuring direct, indirect, and sometimes intangible costs, but they do not compare alternative interventions or relate costs to health outcomes. Instead, they provide baseline data on disease burden, which can inform subsequent economic evaluations and policy decisions.