Ataxia
| Ataxia | |
|---|---|
| Specialty | Neurology, Psychiatry |
| Symptoms |
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Ataxia (from
These nervous system dysfunctions occur in several different patterns, with different results and different possible causes. Ataxia can be limited to one side of the body, which is referred to as hemiataxia. Friedreich's ataxia has gait abnormality as the most commonly presented symptom. Dystaxia is a mild degree of ataxia.[1]
Types
Cerebellar
The term
People with cerebellar ataxia may initially present with poor balance, which could be demonstrated as an inability to stand on one leg or perform
Dysmetria is thought to be caused by a deficit in the control of interaction
- postural instability, in which the person tends to separate his/her feet upon standing, to gain a wider base and to avoid titubation (bodily oscillations tending to be forward-backward ones). The instability is, therefore, worsened when standing with the feet together, regardless of whether the eyes are open or closed. This is a negative Romberg's test, or more accurately, it denotes the individual's inability to carry out the test, because the individual feels unstable even with open eyes. [citation needed]
- Dysfunction of the vermis and associated areas near the midline) presents itself with a wide-based "drunken sailor" gait (called truncal ataxia),[8] characterised by uncertain starts and stops, lateral deviations, and unequal steps. As a result of this gait impairment, falling is a concern in patients with ataxia. Studies examining falls in this population show that 74–93% of patients have fallen at least once in the past year and up to 60% admit to fear of falling.[9][10]
- 'Dysfunction of the cerebrocerebellum' (lateral hemispheres) presents as disturbances in carrying out voluntary, planned movements by the extremities (called appendicular ataxia).[8] These include:
- Intention tremor (coarse trembling, accentuated over the execution of voluntary movements, possibly involving the head and eyes, as well as the limbs and torso)
- Peculiar writing abnormalities (large, unequal letters, irregular underlining)
- A peculiar pattern of dysarthria (slurred speech, sometimes characterised by explosive variations in voice intensity despite a regular rhythm)
- Inability to perform rapidly alternating movements, known as dysdiadochokinesia, occurs, and could involve rapidly switching from supination of the forearm. Movements become more irregular with increases of speed.[11]
- Inability to judge distances or ranges of movement happens. This dysmetria is often seen as undershooting, hypermetria, the required distance or range to reach a target. This is sometimes seen when a patient is asked to reach out and touch someone's finger or touch his or her own nose.[11]
- The rebound phenomenon, also known as the loss of the check reflex, is also sometimes seen in patients with cerebellar ataxia, for example, when patients are flexing their elbows isometrically against a resistance. When the resistance is suddenly removed without warning, the patients' arms may swing up and even strike themselves. With an intact check reflex, the patients check and activate the opposing triceps to slow and stop the movement.[11]
- Patients may exhibit a constellation of subtle to overt cognitive symptoms, which are gathered under the terminology of Schmahmann's syndrome.[12]
Sensory
The term
Sensory ataxia presents itself with an unsteady "stomping" gait with heavy heel strikes, as well as a postural instability that is usually worsened when the lack of proprioceptive input cannot be compensated for by visual input, such as in poorly lit environments.[14][15]
Physicians can find evidence of sensory ataxia during physical examination by having patients stand with their feet together and eyes shut. In affected patients, this will cause the instability to worsen markedly, producing wide oscillations and possibly a fall; this is called a positive Romberg's test. Worsening of the finger-pointing test with the eyes closed is another feature of sensory ataxia. Also, when patients are standing with arms and hands extended toward the physician, if the eyes are closed, the patients' fingers tend to "fall down" and then be restored to the horizontal extended position by sudden muscular contractions (the "ataxic hand").[16][17]
Vestibular
The term vestibular ataxia is used to indicate ataxia due to dysfunction of the
Causes
The three types of ataxia have overlapping causes, so can either coexist or occur in isolation. Cerebellar ataxia can have many causes despite normal neuroimaging.[19]
Focal lesions
Any type of focal lesion of the central nervous system (such as stroke, brain tumor, multiple sclerosis, inflammatory [such as sarcoidosis], and "chronic lymphocytyc inflammation with pontine perivascular enhancement responsive to steroids syndrome" [CLIPPERS[20]]) will cause the type of ataxia corresponding to the site of the lesion: cerebellar if in the cerebellum; sensory if in the dorsal spinal cord...to include cord compression by thickened ligamentum flavum or stenosis of the boney spinal canal...(and rarely in the thalamus or parietal lobe); or vestibular if in the vestibular system (including the vestibular areas of the cerebral cortex).[citation needed]
Exogenous substances (metabolic ataxia)
Other examples include various prescription drugs (e.g. most
Radiation poisoning
Ataxia can be induced as a result of severe acute radiation poisoning with an absorbed dose of more than 30 grays.[26]Furthermore, those with ataxia telangiectasia may have a high sensitivity towards gamma rays and x-rays.[27]
Vitamin B12 deficiency
Vitamin B12 deficiency may cause, among several neurological abnormalities, overlapping cerebellar and sensory ataxia.[28] Neuropsychological symptoms may include sense loss, difficulty in proprioception, poor balance, loss of sensation in the feet, changes in reflexes, dementia, and psychosis, can be reversible with treatment.[29] Complications may include a neurological complex known as subacute combined degeneration of spinal cord, and other neurological disorders.[30]
Hypothyroidism
Symptoms of neurological dysfunction may be the presenting feature in some patients with
Causes of isolated sensory ataxia
Peripheral neuropathies may cause generalised or localised sensory ataxia (e.g. a limb only) depending on the extent of the neuropathic involvement. Spinal disorders of various types may cause sensory ataxia from the lesioned level below, when they involve the dorsal columns.[33][34][35]
Non-hereditary cerebellar degeneration
Non-hereditary causes of cerebellar degeneration include chronic
Hereditary ataxias
Ataxia may depend on
Arnold–Chiari malformation (congenital ataxia)
Succinic semialdehyde dehydrogenase deficiency
Wilson's disease
Gluten ataxia
Gluten ataxia is an
Potassium pump
Malfunction of the
-K+
pumps in the cerebellum of a live mouse results in it displaying ataxia and dystonia.[57]
Cerebellar ataxia associated with anti-GAD antibodies
Antibodies against the enzyme glutamic acid decarboxylase (GAD: enzyme changing glutamate into GABA) cause cerebellar deficits.[58] The antibodies impair motor learning and cause behavioral deficits.[59] GAD antibodies related ataxia is part of the group called immune-mediated cerebellar ataxias.[60] The antibodies induce a synaptopathy.[61] The cerebellum is particularly vulnerable to autoimmune disorders.[62] Cerebellar circuitry has capacities to compensate and restore function thanks to cerebellar reserve, gathering multiple forms of plasticity. LTDpathies gather immune disorders targeting long-term depression (LTD), a form of plasticity.[63]
Diagnosis
- Imaging studies - A CT scan or MRI of the brain might help determine potential causes. An MRI can sometimes show shrinkage of the cerebellum and other brain structures in people with ataxia. It may also show other treatable findings, such as a blood clot or benign tumour, that could be pressing on the cerebellum.
- Lumbar puncture (spinal tap) - A needle is inserted into the lower back (lumbar region) between two lumbar vertebrae to obtain a sample of cerebrospinal fluid for testing.
- Genetic testing - Determines whether the mutation that causes one of the hereditary ataxic conditions is present. Tests are available for many but not all of the hereditary ataxias.
Treatment
The treatment of ataxia and its effectiveness depend on the underlying cause. Treatment may limit or reduce the effects of ataxia, but it is unlikely to eliminate them entirely. Recovery tends to be better in individuals with a single focal injury (such as
The movement disorders associated with ataxia can be managed by pharmacological treatments and through
Current research suggests that, if a person is able to walk with or without a mobility aid, physical therapy should include an exercise program addressing five components: static balance, dynamic balance, trunk-limb coordination, stairs, and contracture prevention. Once the physical therapist determines that the individual is able to safely perform parts of the program independently, it is important that the individual be prescribed and regularly engage in a supplementary home exercise program that incorporates these components to further improve long term outcomes. These outcomes include balance tasks, gait, and individual activities of daily living. While the improvements are attributed primarily to changes in the brain and not just the hip or ankle joints, it is still unknown whether the improvements are due to adaptations in the cerebellum or compensation by other areas of the brain.[69]
Decomposition, simplification, or slowing of multijoint movement may also be an effective strategy that therapists may use to improve function in patients with ataxia.[13] Training likely needs to be intense and focused—as indicated by one study performed with stroke patients experiencing limb ataxia who underwent intensive upper limb retraining.[72] Their therapy consisted of constraint-induced movement therapy which resulted in improvements of their arm function.[72] Treatment should likely include strategies to manage difficulties with everyday activities such as walking. Gait aids (such as a cane or walker) can be provided to decrease the risk of falls associated with impairment of balance or poor coordination. Severe ataxia may eventually lead to the need for a wheelchair. To obtain better results, possible coexisting motor deficits need to be addressed in addition to those induced by ataxia. For example, muscle weakness and decreased endurance could lead to increasing fatigue and poorer movement patterns.[citation needed]
There are several assessment tools available to therapists and health care professionals working with patients with ataxia. The International Cooperative Ataxia Rating Scale (ICARS) is one of the most widely used and has been proven to have very high reliability and validity.[73] Other tools that assess motor function, balance and coordination are also highly valuable to help the therapist track the progress of their patient, as well as to quantify the patient's functionality. These tests include, but are not limited to:
- The Berg Balance Scale
- Tandem Walking (to test for Tandem gaitability)
- Scale for the Assessment and Rating of Ataxia (SARA)[74]
- tapping tests – The person must quickly and repeatedly tap their arm or leg while the therapist monitors the amount of dysdiadochokinesia.[75]
Other uses
The term "ataxia" is sometimes used in a broader sense to indicate lack of coordination in some physiological process. Examples include optic ataxia (lack of coordination between visual inputs and hand movements, resulting in inability to reach and grab objects) and ataxic respiration (lack of coordination in respiratory movements, usually due to dysfunction of the respiratory centres in the medulla oblongata).
Optic ataxia may be caused by lesions to the
See also
External links
References
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- ^ "Ataxia - Symptoms & Causes". Mayo Clinic. 3 June 2020. Retrieved 10 August 2020.
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- ^ "Sensory Ataxia". Physiopedia. Retrieved 19 October 2022.
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Further reading
- Perlman S (1998). "Hereditary Ataxia Overview (last revision 2012)". In Pagon RA, Bird TD, Dolan CR, Stephens K, Adam MP, Bird TD (eds.). All GeneReview. University of Washington, Seattle. PMID 20301317.
- Manto M, Gruol D, Schmahmann J, Koibuchi N, Rossi F (2013). Handbook of the Cerebellum and Cerebellar Disorders. Springer. ISBN 978-94-007-1332-1.
- Esmail S (2018). "Cerebellar ataxia but normal neuroimaging: now what?". Scivision.
