Glossary

A seizure is a sudden change in behavior due to an excessive electrical activity in the brain. There are a wide variety of possible symptoms of seizures, depending on what parts of the brain are affected. Many types of seizures cause loss of consciousness with twitching or shaking of the body. However, some seizures consist of staring spells that can easily go unnoticed. Occasionally, seizures can cause temporary abnormal sensations or visual disturbances.

Sialidosis is a severe inherited disorder that affects many organs and tissues, including the nervous system. This disorder is divided into two types, which are distinguished by the age at which symptoms appear and the severity of features.

Mutations in the NEU1 gene cause sialidosis. This gene provides instructions for making an enzyme called neuraminidase 1 (NEU1), which is found in lysosomes. Lysosomes are compartments within the cell that use enzymes to digest and recycle materials. The NEU1 enzyme helps break down large sugar molecules attached to certain proteins by removing a substance known as sialic acid.

Spasticity is a condition in which certain muscles are continuously contracted. This contraction causes stiffness or tightness of the muscles and may interfere with movement, speech, and manner of walking. Spasticity is usually caused by damage to the portion of the brain or spinal cord that controls voluntary movement. Symptoms may include hypertonicity (increased muscle tone), clonus (a series of rapid muscle contractions), exaggerated deep tendon reflexes, muscle spasms, scissoring (involuntary crossing of the legs), and fixed joints. The degree of spasticity varies from mild muscle stiffness to severe, painful, and uncontrollable muscle spasms. Spasticity can interfere with rehabilitation in patients with certain disorders, and often interferes with daily activities.

A lipid or fat that is critical for the normal structure and function of cells and tissues. It is normally degraded into ceraminde by sphingomyelinase. Niemann-Pick Types A and B are characterized by the absences of the enzyme and the accumulation of sphingomyelin.

An enzyme that resides within the lysosomes and is responsible for the conversion of a lipid (fat) called sphingomyelin into another type of lipid called ceramide. This lipid conversion is critical for the normal structure and function of cells and tissues. Niemann-Pick Type A and B are characterized by its absence and resultant accumulation of sphingomyelin.

A large dark-red oval organ on the left side of the body between the stomach and the diaphragm; produces cells involved in immune responses Definitions from: WordNet®

The startle response or reflex is a normal reflex for an infant when he or she is startled or feels like they are falling. The infant will have a "startled" look and the arms will fling out sideways with the palms up and the thumbs flexed. Presence of the startle response in babies older than a few months is abnormal and associated with neurological damage. For more details visit: http://www.umm.edu/ency/article/003293.htm

The substance on which an enzyme acts.