Parkinson disease is a motor system disorder that causes trembling, stiffness and trouble moving.

Parkinson disease is a movement disorder that can cause muscles to tighten and become rigid. It can make it hard to walk and engage in daily activities.

Periodic paralysis (PP) is a rare genetic disorder. It causes sudden attacks of short-term muscle weakness, stiffness, or paralysis. These attacks may affect the whole body or just one or two limbs.

Peripheral neuropathy is a type of damage to the nervous system.

Polymyositis is a disease that causes muscles to become irritated and inflamed. The muscles eventually start to break down and become weak. The condition can affect muscles all over the body. It can make even simple movements hard to do....

A positron emission tomography (PET) scan is a type of nuclear medicine imaging test. It is used to examine various body tissues to identify certain conditions by looking at blood flow, metabolism, and oxygen use. PET scans may also be ...

Post-polio syndrome (PPS) is a disorder of the nerves and muscles that happens in some people many years after they have had polio. PPS may cause new muscle weakness that worsens over time, pain in the muscles and joints, and tiredness.

Multiple sclerosis (MS) is a disease that interferes with your brain's ability to operate your body.

Prion diseases comprise several conditions. A prion is a type of protein that can trigger normal proteins in the brain to fold abnormally. Prion diseases can affect both humans and animals and are sometimes transmitted to humans by ...

Progressive supranuclear palsy is a disorder in a small section of the brain that causes weakness of certain muscles.This is a rare disorder but may be mistaken for Parkinson's disease.