Refer to the Neurology Glossary to learn the meaning of medical terms used by neurologists.

Attention Deficit Hyperactivity Disorder (ADHD) in Children and Adolescents is a condition that becomes apparent in some children in the preschool and early school years. It is hard for these children to control their behavior and/or pay attention. It is estimated that between 3 and 5 percent of children have ADHD, or approximately 2 million children in the United States. This means that in a classroom of 25 to 30 children, it is likely that at least one will have ADHD.

Alzheimer's Disease is a brain disorder that seriously affects a person's ability to carry out daily activities. The most common form of dementia among older people is Alzheimer's disease (AD), which initially involves the parts of the brain that control thought, memory, and language. Although scientists are learning more every day, right now they still do not know what causes AD, and there is no cure. Abnormal clumps in the brain (called amyloid plaques) and tangled bundles of fibers (called neurofibrillary tangles) are considered signs of Alzheimer's disease.

Epilepsy is a brain disorder that results in repeated seizures. Nerve cells normally communicate with each other through electrical impulses. These impulses act on other neurons, glands, and muscles to produce human thoughts, feelings, and actions. During a seizure, these impulses become overactive, causing strange sensations, emotions, and behavior, or sometimes convulsions, muscle spasms, and loss of consciousness. Having a seizure does not mean that a person has epilepsy. Only when a person has had two or more seizures is he or she considered to have epilepsy. Types of epilepsy include frontal lobe epilepsy, pediatric epilepsy, refractory epilepsy, and temporal lobe epilepsy (TLE).

Headache: What hurts when you have a headache? The bones of the skull and tissues of the brain itself never hurt, because they lack pain-sensitive nerve fibers. Several areas of the head can hurt, including a network of nerves which extends over the scalp and certain nerves in the face, mouth, and throat. Also sensitive to pain, because they contain delicate nerve fibers, are the muscles of the head and blood vessels found along the surface and at the base of the brain. Types of headaches include chronic daily headaches, cluster headaches, menstrual headaches, migraine headaches, rebound headaches, and tension-type headaches.

Multiple Sclerosis (MS): during an MS attack, inflammation occurs in areas of the brain and spinal cord called white matter. This inflammation arises in random patches called plaques. This symptom of MS is followed by destruction of myelin, the fatty covering that insulates nerve cell fibers in the brain and spinal cord. Myelin facilitates the smooth, high-speed transmission of electrochemical messages between the brain, the spinal cord, and the rest of the body; when it is damaged, neurological transmission of messages may be slowed or blocked completely, leading to diminished or lost function.

Parkinson's Disease is a disorder that affects nerve cells, or neurons, in a part of the brain that controls muscle movement. In Parkinson's disease, neurons that make a chemical called dopamine die or do not work properly. Dopamine normally sends signals that help coordinate your movements. No one knows what damages these cells. Symptoms of Parkinson's disease may include: trembling of hands, arms, legs, jaw and face; stiffness of the arms, legs and trunk; slowness of movement; and poor balance and coordination.

Stroke: A stroke occurs when the blood supply to part of the brain is suddenly interrupted or when a blood vessel in the brain bursts, spilling blood into the spaces surrounding brain cells. In the same way that a person suffering a loss of blood flow to the heart is said to be having a heart attack, a person with a loss of blood flow to the brain or sudden bleeding in the brain can be said to be having a "brain attack." Brain cells die when they no longer receive oxygen and nutrients from the blood or when they are damaged by sudden bleeding into or around the brain. Ischemia is the term used to describe the loss of oxygen and nutrients for brain cells when there is inadequate blood flow. Ischemia ultimately leads to infarction, the death of brain cells which are eventually replaced by a fluid-filled cavity (or infarct) in the injured brain.