Common Words and Phrases Associated with Charcot Marie Tooth Disease

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Note: The definitions of words and phrases found on this page are subject to change at any time. The definitions are provided for informational purposes only. Every effort is made to provide the most up to date information. Unless otherwise noted, definitions are derived from MedTerms Medical Dictionary. The information provided on this page is not intended to diagnose any medical condition you may have and should not be construed as medical advice.

AFO - Acronym for Ankle Foot Orthosis.

 

Allele - An allele is one of two or more versions of a gene. An individual inherits two alleles for each gene, one from each parent. If the two alleles are the same, the individual is homozygous for that gene. If the alleles are different, the individual is heterozygous. Though the term allele was originally used to describe variation among genes, it now also refers to variation among non-coding DNA sequences. Genome.Gov.

 

Autosomal - Pertaining to any of the non-sex chromosomes.

 
 

Autosomal Dominant - A pattern of inheritance in which an affected individual has one copy of a mutated gene and one normal copy of a gene on a pair of autosomal chromosomes.

 

Autosomal Recessive - A pattern of inheritance in which an affected individual has two copies of a mutated gene on a pair of autosomal chromosomes.

 

Axon - The long fiber of a nerve cell (a neuron) that acts somewhat like a fiber-optic cable carrying messages.

 

Chromosome - A carrier of genetic information that is visible under an ordinary light microscope. Each human chromosome has two arms: the p (short) arm, and the q (long) arm. Generally, the nucleus of a human cell contains two sets of chromosomes (each set is called an allele) - one allele given by each parent. Each allele has 23 single chromosomes: 22 autosomes (non-sex chromosome); and an X /Y sex chromosome combination denoting male, or an X/X sex chromosome combination denoting female [one X chromosome is given by the mother, and either an X chromosome or a Y chromosome is randomly given by the father]. A chromosome contains roughly equal parts of protein and DNA. The chromosomal DNA contains an average of 150 million nucleotide building blocks, called bases.

 

De Novo - A genetic alteration that is present for the first time in one family member as a result of a variant (mutation) in a germ cell (egg or sperm) of one of the parents, or a variant that arises in the fertilized egg itself during early embryogenesis. Also called: de novo variant, new mutation, or new variant. NCI Dictionary of Genetic Terms.

 

Demyelinating - A degenerative process that erodes away the myelin sheath that normally protects nerve fibers.

 

Distal - The more (or most) distant of two (or more) things, the points farthest away from the brain and spinal cord.

 

Dominant - A genetic trait is considered dominant if it is expressed in a person who has only one copy of a particular gene mutation. (In genetic terms, a dominant trait is one that is phenotypically expressed in heterozygotes).

 

EMG - Electromyogram. An electromyogram is a test that is used to record the electrical activity of muscles. When muscles are active, they produce an electrical current. This current is usually proportional to the level of the muscle activity. An EMG can be used to detect abnormal electrical activity of muscle that can occur in many diseases and conditions, including peripheral nerve damage.

Foot-Drop - Dropping of the front of the foot due to weakness or paralysis of the anterior muscles of the lower leg. Foot-drop results in a steppage gait.

 

Gait - The manner of walking.

 
 

Heterozygote - An individual who has two different copies of a particular gene (one normal copy, one copy with a mutation).

Heterozygous - Possessing two different forms of a particular gene (one normal copy, one copy with a mutation). Dominant subtypes of CMT are referred to as heterozygous.

 
 

Homozygote - An individual who has two identical forms of a particular gene (two copies of the same mutation).

 

Homozygous - Possessing two identical forms of a particular gene (two copies of the same mutation). Recessive subtypes of CMT are referred to as homozygous.

KAFO - Acronym for Knee Ankle Foot Orthosis.

 
 

Myelin - The fatty substance that covers and protects nerves. Myelin is a layered tissue that surrounds the nerve fibers (axons). This sheath around the axons acts like a conduit in an electrical system, ensuring that messages sent by axons are not lost en-route to their intended destination.

 

NCV - Nerve Conduction Velocity. An NCV test is an electrical test used to detect nerve conditions. During the NCV test, the nerve is electrically stimulated by one electrode while other electrodes detect the electrical impulse "downstream" from the first electrode. The NCV test is usually done with surface patch electrodes similar to those used for an EKG (electrocardiogram). The patch electrodes are placed on the skin over the nerve at various locations. One electrode stimulates the nerve with a very mild electrical impulse. The resulting electrical activity is recorded by the other electrodes. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to calculate the speed of impulse transmission (the nerve conduction velocity, or NCV). This test is commonly used to diagnose and to monitor Charcot Marie Tooth Disease.

 

Orthosis - The correction of disorders of the limbs or spine by use of braces and other devices to correct alignment or to provide support.

 

Orthotic - A support, brace, or splint used to support, align, prevent, or correct the function of movable parts of the body. Shoe inserts are orthotics that are intended to correct an abnormal or irregular walking pattern, by altering slightly the angles at which the foot strikes a walking or running surface.

Orthotist - A person who specializes in the making and fitting of orthotic devices, and who is qualified to practice in the medical specialty of orthotics. Dictionary.com.

 
 

Peroneal (Muscles) - The peroneal/fibular muscles are a group of two muscles of the leg that lie within the fibular/lateral compartment of the leg (outside edges of the lower leg). Originating from the fibula (lower leg/calf bone) and inserting on certain metatarsal bones (the bones of the foot), these muscles play an important role in the movement of the foot at the ankle joint. Ken-Hub Library of Anatomy.

Pes Cavus - A condition in which the arch of the foot is too high. The opposite of pes planus.

 

Pes Planus - A condition in which the entire sole of the foot touches the floor when standing. The opposite of pes cavus. Flat foot.

 
 

Phrenic Nerve - A nerve that arises mainly from the fourth cervical nerve and is primarily the motor nerve of the diaphragm, but also sends sensory fibers to the pericardium (the thin membrane that encases the heart). Dictionary.com.

Polyneuropathy - A disease of the Peripheral Nervous System involving several nerves. Medical-Dictionary.

 
 

Proband - The family member through whom a family's medical history comes to attention. An example might be when somebody is the first in the family to be diagnosed with Charcot Marie Tooth Disease. The proband may also be called the index case, propositus (if male), or proposita (if female).

 

Proprioception - The ability to sense stimuli arising within the body regarding position, motion, and equilibrium. Even if a person is blindfolded, he or she knows through proprioception if an arm is above the head or hanging by the side of the body. The sense of proprioception is disturbed in many neurological disorders, including Charcot Marie Tooth Disease. It can sometimes be improved through the use of sensory integration therapy, a type of specialized occupational therapy.

 

Proximal - Toward the beginning, the nearer of two (or more) things, the points closest to brain and spinal cord.

 

Recessive - A genetic trait is considered recessive if it is expressed in a person who has two copies of a particular gene mutation.  (In genetic terms, a recessive trait is one that is phenotypically expressed in homozygotes).

 

Schwann Cell - A myelin-secreting glial cell that spirally wraps around an axon of the Peripheral Nervous System to form the myelin sheath. Merriam-Webster.

Steppage Gait - A manner of walking in which the advancing foot is lifted high so that the toes clear the ground. Steppage gait is a sign of foot-drop.

 
 

X Chromosome - The sex chromosome that is found twice in females, and singly, along with a single Y Chromosome, in males.

 

X-Linked - A gene that is located on the X Chromosome. An X-Linked disorder is associated with or caused by a gene that is located on the X Chromosome.