Cerebellum (in blue) of the human brain
Find information on thousands of medical conditions and prescription drugs.

Spinocerebellar ataxia

Spinocerebellar ataxia (SCA) is a genetic disease with multiple types, each of which could be considered a disease in its own right. As with other forms of ataxia, SCA results in unsteady and clumsy motion of the body due to a failure of the fine coordination of muscle movements, along with other symptoms. more...

Home
Diseases
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
Sabinas brittle hair...
Saccharopinuria
Sacral agenesis
Saethre-Chotzen syndrome
Salla disease
Salmonellosis
Sandhoff disease
Sanfilippo syndrome
Sarcoidosis
Say Meyer syndrome
Scabies
Scabiophobia
Scarlet fever
Schamberg disease...
Schistosomiasis
Schizencephaly
Schizophrenia
Schmitt Gillenwater Kelly...
Sciatica
Scimitar syndrome
Sciophobia
Scleroderma
Scrapie
Scurvy
Selachophobia
Selective mutism
Seminoma
Sensorineural hearing loss
Seplophobia
Sepsis
Septo-optic dysplasia
Serum sickness
Severe acute respiratory...
Severe combined...
Sezary syndrome
Sheehan syndrome
Shigellosis
Shingles
Shock
Short bowel syndrome
Short QT syndrome
Shprintzen syndrome
Shulman-Upshaw syndrome
Shwachman syndrome
Shwachman-Diamond syndrome
Shy-Drager syndrome
Sialidosis
Sickle-cell disease
Sickle-cell disease
Sickle-cell disease
Siderosis
Silicosis
Silver-Russell dwarfism
Sipple syndrome
Sirenomelia
Sjogren's syndrome
Sly syndrome
Smallpox
Smith-Magenis Syndrome
Sociophobia
Soft tissue sarcoma
Somniphobia
Sotos syndrome
Spasmodic dysphonia
Spasmodic torticollis
Spherocytosis
Sphingolipidosis
Spinal cord injury
Spinal muscular atrophy
Spinal shock
Spinal stenosis
Spinocerebellar ataxia
Splenic-flexure syndrome
Splenomegaly
Spondylitis
Spondyloepiphyseal...
Spondylometaphyseal...
Sporotrichosis
Squamous cell carcinoma
St. Anthony's fire
Stein-Leventhal syndrome
Stevens-Johnson syndrome
Stickler syndrome
Stiff man syndrome
Still's disease
Stomach cancer
Stomatitis
Strabismus
Strep throat
Strongyloidiasis
Strumpell-lorrain disease
Sturge-Weber syndrome
Subacute sclerosing...
Sudden infant death syndrome
Sugarman syndrome
Sweet syndrome
Swimmer's ear
Swyer syndrome
Sydenham's chorea
Syncope
Syndactyly
Syndrome X
Synovial osteochondromatosis
Synovial sarcoma
Synovitis
Syphilis
Syringomas
Syringomyelia
Systemic carnitine...
Systemic lupus erythematosus
Systemic mastocytosis
Systemic sclerosis
T
U
V
W
X
Y
Z
Medicines

It can be easily misdiagnosed as another neurological condition, such as multiple sclerosis (MS). There is no known cure for this degenerative condition, which lasts for the remainder of the sufferer's life. Treatments are generally limited to softening symptoms, not the disease itself. The condition is irreversible. A person with this disease will usually end up needing to use a wheelchair, and eventually they will need assistance to perform daily tasks. The symptoms of the condition vary with the specific type (there are several), and with the individual patient. Generally, a sufferer retains full mental capacity while they progressively lose physical control over their body until their death.

One means of identifying the disease is with an MRI to view the brain. Once the disease has progressed sufficiently, the cerebellum (a part of the brain) can be seen to have visibly shrunk. The most precise means of identifying SCA, including the specific type, is through DNA analysis. Some, but far from all, types of SCA may be inherited, so a DNA test may be done on the children of a sufferer, to see if they are at risk of developing the condition.

SCA is related to olivopontocerebellar atrophy (OPCA); SCA types 1, 2, and 7 are also types of OPCA. However, not all types of OPCA are types of SCA, and vice versa. This overlapping classification system is both confusing and controversial to some in this field.

Types

The following is a list of some, not all, types of Spinocerebellar ataxia. The first ataxia gene was identified in 1993 for a dominantly inherited type. It was called “Spinocerebellar ataxia type 1" (SCA1). Subsequently, as additional dominant genes were found they were called SCA2, SCA3, etc. Usually, the "type" number of "SCA" refers to the order in which the gene was found. At this time, there are at least 22 different gene mutations which have been found (not all listed).

Identifying the different types of SCA now requires knowledge of the normal genetic code, and faults in this code, which are contained in a person's DNA (Deoxyribonucleic acid). The "CAG" mentioned below is one of many three-letter sequences that makes up the genetic code, this specific one coding the aminoacid glutamine. Thus, those ataxias with poly CAG expansions, along with several other neurodegenerative diseases resulting from a poly CAG expansion, are referred to as polyglutamine diseases.

Notes

Both onset of initial symptoms and duration of disease can be subject to variation. If the disease is caused by a polyglutamine trinucleotide repeat CAG expansion, a longer expansion will lead to an earlier onset and a more radical progression of clinical symptoms, resulting in earlier death.

Read more at Wikipedia.org


[List your site here Free!]


Friedreich's ataxia
From Gale Encyclopedia of Medicine, 4/6/01 by Richard Robinson

Definition

Friedreich's ataxia (FA) is an inherited, progressive nervous system disorder causing loss of balance and coordination.

Description

Ataxia is a condition marked by impaired coordination. Friedreich's ataxia is the most common inherited ataxia, affecting between 3,000-5,000 people in the United States. FA is an autosomal recessive disease, which means that two defective gene copies must be inherited to develop symptoms, one from each parent. A person with only one defective gene copy will not show signs of FA, but may pass along the gene to offspring. Couples with one child affected by FA have a 25% chance in each pregnancy of conceiving another affected child.

Causes & symptoms

Causes

The gene for FA codes for a protein called frataxin. Normal frataxin is found in the cellular energy structures known as mitochondria, where it is involved in regulating the transport of iron. In FA, the frataxin gene is expanded with nonsense information known as a "triple repeat." This extra DNA interferes with normal production of frataxin, thereby impairing iron transport. FA is thought to develop at least in part because defects in iron transport prevent efficient use of cellular energy supplies.

The nerve cells most affected by FA are those in the spinal cord involved in relaying information between muscles and the brain. Tight control of movement requires complex feedback between the muscles promoting a movement, those restraining it, and the brain. Without this control, movements become uncoordinated, jerky, and inappropriate to the desired action.

Symptoms

Symptoms of FA usually first appear between the ages of 8 and 15, although onset as early as 18 months or as late as age 25 is possible. The first symptom is usually gait incoordination. A child with FA may graze doorways when passing through, for instance, or trip over low obstacles. Unsteadiness when standing still and deterioration of position sense is common. Foot deformities and walking up off the heels often results from uneven muscle weakness in the legs. Muscle spasms and cramps may occur, especially at night.

Ataxia in the arms follows, usually within several years, leading to decreased hand-eye coordination. Arm weakness does not usually occur until much later. Speech and swallowing difficulties are common. Diabetes mellitus may also occur. Nystagmus, or eye tremor, is common, along with some loss of visual acuity. Hearing loss may also occur. A side-to-side curvature of the spine (scoliosis) occurs in many cases, and may become severe.

Heartbeat abnormalities occur in about two thirds of FA patients, leading to shortness of breath after exertion, swelling in the lower limbs, and frequent complaints of cold feet.

Diagnosis

Diagnosis of FA involves a careful medical history and thorough neurological exam. Lab tests include electromyography, an electrical test of muscle, and a nerve conduction velocity test. An electrocardiogram may be performed to diagnose heart arrhythmia.

Direct DNA testing is available, allowing FA to be more easily distinguished from other types of ataxia. The same test may be used to determine the presence of the genetic defect in unaffected individuals, such as siblings.

Treatment

There is no cure for FA, nor any treatment that can slow its progress. Amantadine may provide some limited improvement in ataxic symptoms, but is not recommended in patients with cardiac abnormalities. Physical and occupational therapy are used to maintain range of motion in weakened muscles, and to design adaptive techniques and devices to compensate for loss of coordination and strength. Some patients find that using weights on the arms can help dampen the worst of the uncoordinated arm movements.

Heart arrhythmias and diabetes are treated with drugs specific to those conditions.

Prognosis

The rate of progression of FA is highly variable. Most patients lose the ability to walk within 15 years of symptom onset, and 95% require a wheelchair for mobility by age 45. Reduction in lifespan from FA complications is also quite variable. Average age at death is in the mid-thirties, but may be as late as the mid-sixties. As of mid-1998, the particular length of the triple repeat has not been correlated strongly enough with disease progression to allow prediction of the course of the disease on this basis.

Prevention

There is no way to prevent development of FA in a person carrying two defective gene copies.

Key Terms

Ataxia
A condition marked by impaired coordination.
Scoliosis
An abnormal, side-to-side curvature of the spine.

Further Reading

For Your Information

    Books

  • "Spinocerebellar Degeneration (Friedreich's Ataxia)." In Harrison's Principles of Internal Medicine, edited by Kurt J. Isselbacher et al. New York: McGraw-Hill, 1994, 2285.

    Periodicals

  • Quest. Available from the Muscular Dystrophy Association.

    Organizations

  • Muscular Dystrophy Association. 3300 East Sunrise Drive, Tucson, AZ 85718. (520) 529-2000 or (800) 572-1717. http://www.mdausa.org.

Gale Encyclopedia of Medicine. Gale Research, 1999.

Return to Spinocerebellar ataxia
Home Contact Resources Exchange Links ebay