* * *
An inability to coordinate muscle activity during voluntary movement; most often due to disorders of the cerebellum or the posterior columns of the spinal cord; may involve the limbs, head, or trunk. SYN: ataxy, incoordination. [G. a-prov. + taxis, order]
- acute a. generalized a. of abrupt onset, most often caused by drug intoxications, poisonings, or vestibular neuronitis.
- Briquet a. weakening of the muscle sense and increased sensibility of the skin, in hysteria. SYN: hysterical a..
- Bruns a. difficulty in initiation of movement of the feet when they are in contact with the ground; a condition related to a frontal lobe lesion.
- Friedreich a. [MIM*229300] a neurologic disorder characterized by a., dysarthria, scoliosis, high-arched foot or pes cavus and paralysis of the muscles, especially of the lower extremities; onset usually in childhood or youth with sclerosis of the posterior and lateral columns of the spinal cord; autosomal recessive inheritance, caused by mutation involving trinucleotide repeat expansion in Friedreich a. gene (FRDA) on chromosome 9q. SYN: hereditary spinal a., heredotaxia.
- gluten a. a. resultant from immunologic damage to cerebellulm, posterior spinal columns, and periperal nerves in gluten-senstive individuals
- hereditary cerebellar a. 1. a disease of later childhood and early adult life, marked by ataxic gait, hesitating and explosive speech, nystagmus, and sometimes optic neuritis. It probably comprises several distinct conditions with diverse patterns of inheritance. 2. collective term for a number of hereditary disorders in which cerebellar signs are the most prominent finding.
- hysterical a. SYN: Briquet a..
- Leyden a. SYN: pseudotabes.
- locomotor a. the severe gait a. seen with tabetic neurosyphylis. Patients walk with the feet wide apart, slapping them clumsily to the floor with each step, and depend on visual cues to maintain balance. SEE ALSO: tabetic neurosyphilis.
- motor a. a. developing upon attempting to perform coordinated muscular movements. SYN: kinetic a..
- optic a. an inability to guide the hand toward an object using visual information; seen in Balint syndrome.
- respiratory a. SYN: Biot respiration.
- sensory a. an a. due to impairment of position sense caused by lesions located at some point along the central or peripheral sensory pathways.
- spinocerebellar a. the most common hereditary a., with onset in middle to late childhood, manifested as limb a., nystagmus, kyphoscoliosis, and pes cavus; the major pathologic changes are found in the posterior columns of the spinal cord; most often autosomal recessive inheritance.
- static a. inability to preserve equilibrium while standing, due to loss of myesthesia; present during the resting state.
- a. telangiectasia, a.-telangiectasia a slowly progressive multisystem disorder with the following manifestations: a. appearing with the onset of walking; telangiectases of the conjunctiva and skin of the face, neck, and ears; athetosis and nystagmus; and recurrent infections of the respiratory system caused by immunoglobulin deficiencies. Due to an autosomal recessive trait, with major pathologic changes involving the cerebellar cortex, posterior columns, spinocerebellar tracks, anterior horn cells, dorsal roots, and peripheral nerves. A high percentage of the patients have an IgA deficiency concomitant with decreased T-helper cell function. There are numerous chromosome breaks and α-fetoprotein levels in the sera are usually elevated; caused by several mutations in PI3′kinase gene. SYN: a. telangiectasia syndrome, Louis-Bar syndrome.
- vasomotor a. a form of autonomic a. causing irregularity in the peripheral circulation, marked by alternations of pallor and suffusion, due to spasm of the smaller blood vessel s.
- vestibulocerebellar a. a. due to disease of the central vestibular system or its cerebellar components, manifested clinically by an unsteady gait, nystagmus, and incoordination of arm and leg movements.
* * *
atax·ia ə-'tak-sē-ə, (')ā- n an inability to coordinate voluntary muscular movements that is symptomatic of some nervous disorders
atax·ic -sik adj
* * *
n.
the shaky movements and unsteady gait that result from the brain's failure to regulate the body's posture and the strength and direction of limb movements. It may be due to disease of the sensory nerves or the cerebellum. In cerebellar ataxia there is clumsiness of willed movements. The patient staggers when walking; he cannot pronounce words properly and may have nystagmus. Cerebellar (or Nonne's) syndrome is a form of cerebellar ataxia. Friedreich's ataxia is an inherited disorder appearing first in adolescence. It has the features of cerebellar ataxia, together with spasticity of the limbs. The unsteady movements of sensory ataxia are exaggerated when the patient closes his eyes (see Romberg's sign). See also ataxia telangiectasia, tabes dorsalis.
• ataxic adj.
* * *
atax·ia (ə-takґse-ə) [Gr., from a-1 + taxis order] failure of muscular coordination; irregularity of muscular action. Cf. asynergy and dystaxia.Medical dictionary. 2011.