Ataxia is the loss of the ability to coordinate muscular movement.
Etiology
Ataxia is caused by the dysfunction of the cerebellum and its afferent and efferent pathways. Ataxia has a broad list of causes, including:
Ataxia is caused by the dysfunction of the cerebellum and its afferent and efferent pathways. Ataxia has a broad list of causes, including:
Drugs, such as alcohol, barbiturates, lithium, or chemotherapeutic drugs
Toxins, such as mercury, solvents, lead, gasoline, or glue
Infections, such as coxsackievirus, human immunodeficiency virus (HIV), Legionella, Lyme disease, or varicella
Nutritional conditions, such as vitamin B1, B12, or E deficiency
Endocrine conditions, such as hypothyroidism
Vascular conditions, such as cerebellar infarction or hemorrhage
Hereditary conditions, such as Friedreich's ataxia, ataxia telangiectasia, or Machado-Joseph (SCA-3)
Neoplastic conditions, such as cerebellar glioma, metastatic tumors, or paraneoplastic syndromes
Congenital conditions, such as Chiari or Dandy-Walker malformations .
Epidemiology
Friedreich's ataxia is the most common cause of hereditary ataxia, constituting about half of hereditary ataxias. The incidence of Friedreich's ataxia is approximately 1 to 2 per 50,000 in the United States .
Friedreich's ataxia is the most common cause of hereditary ataxia, constituting about half of hereditary ataxias. The incidence of Friedreich's ataxia is approximately 1 to 2 per 50,000 in the United States .
History
The history should include time of onset of the development of ataxia, whether it is symmetric or asymmetric, and whether it is focal or diffuse. A gradual onset with symmetric and bilateral symptoms suggests a biochemical, immune, metabolic, or toxic cause. Focal and asymmetric ataxias with other symptoms such as headaches and cranial nerve palsies suggest a cerebellar mass. The history should also include questioning regarding medications that can cause ataxia (e.g., lithium), exposure to toxins (e.g., mercury), and history of ethanol intake. The age of onset can be helpful in differentiating some of the hereditary ataxias. The patient should be questioned about recent or chronic infections because there are several that can cause ataxia (e.g., varicella, Lyme disease, or HIV).
The history should include time of onset of the development of ataxia, whether it is symmetric or asymmetric, and whether it is focal or diffuse. A gradual onset with symmetric and bilateral symptoms suggests a biochemical, immune, metabolic, or toxic cause. Focal and asymmetric ataxias with other symptoms such as headaches and cranial nerve palsies suggest a cerebellar mass. The history should also include questioning regarding medications that can cause ataxia (e.g., lithium), exposure to toxins (e.g., mercury), and history of ethanol intake. The age of onset can be helpful in differentiating some of the hereditary ataxias. The patient should be questioned about recent or chronic infections because there are several that can cause ataxia (e.g., varicella, Lyme disease, or HIV).
Physical examination
The examination should include an evaluation of the type of ataxia. The patient's speech should be observed for difficulties such as dysarthria or scanning speech. The patient's gait should be observed. Eye movements should be examined for nystagmus or cranial nerve palsies. The patient's movements should be evaluated for tremor, loss of proprioception, weakness, loss of fine motor control, spasticity, rigidity, bradykinesia, and dystonia. In addition, the history and physical examination should search for other problems that can mimic ataxia from cerebellar causes, such as vertigo from vestibular disease, or difficulties in gait that are actually due to leg weakness .
The examination should include an evaluation of the type of ataxia. The patient's speech should be observed for difficulties such as dysarthria or scanning speech. The patient's gait should be observed. Eye movements should be examined for nystagmus or cranial nerve palsies. The patient's movements should be evaluated for tremor, loss of proprioception, weakness, loss of fine motor control, spasticity, rigidity, bradykinesia, and dystonia. In addition, the history and physical examination should search for other problems that can mimic ataxia from cerebellar causes, such as vertigo from vestibular disease, or difficulties in gait that are actually due to leg weakness .
Testing
Computed tomography or magnetic resonance imaging (MRI) of the brain (preferably MRI) to evaluate for causes such as a neoplasm, hemorrhage, or infarction. This should be done as soon as possible, because some causes may be surgical emergencies (e.g., mass effect leading to brain stem herniation).
Many other causes may be discovered by laboratory testing. Possible tests include thyroid-stimulating hormone, vitamin B1 and vitamin B12 levels, HIV,
P.54rapid plasma reagin, Lyme, and toxicology. Antibodies to Yo, Ri, and PCD may be present in paraneoplastic syndromes. In children, screening for inherited metabolic disorders may be warranted.
Lumbar puncture may be helpful for diagnosing causes such as multiple sclerosis, viral cerebellitis, and other infections. An electroencephalogram may reveal seizure-related ataxia .
Computed tomography or magnetic resonance imaging (MRI) of the brain (preferably MRI) to evaluate for causes such as a neoplasm, hemorrhage, or infarction. This should be done as soon as possible, because some causes may be surgical emergencies (e.g., mass effect leading to brain stem herniation).
Many other causes may be discovered by laboratory testing. Possible tests include thyroid-stimulating hormone, vitamin B1 and vitamin B12 levels, HIV,
P.54rapid plasma reagin, Lyme, and toxicology. Antibodies to Yo, Ri, and PCD may be present in paraneoplastic syndromes. In children, screening for inherited metabolic disorders may be warranted.
Lumbar puncture may be helpful for diagnosing causes such as multiple sclerosis, viral cerebellitis, and other infections. An electroencephalogram may reveal seizure-related ataxia .
Genetics
There is a long list of hereditary ataxias. The most common of these is Friedreich's ataxia. The hereditary ataxias are subdivided by the mode of inheritance. The most common are autosomal recessive (e.g., Friedreich's ataxia). Autosomal dominant ataxias are classified by a sequential numbering system (e.g., SCA-3 which is most common in the United States). There are also X-linked and mitochondrial forms of hereditary ataxias .
There is a long list of hereditary ataxias. The most common of these is Friedreich's ataxia. The hereditary ataxias are subdivided by the mode of inheritance. The most common are autosomal recessive (e.g., Friedreich's ataxia). Autosomal dominant ataxias are classified by a sequential numbering system (e.g., SCA-3 which is most common in the United States). There are also X-linked and mitochondrial forms of hereditary ataxias .
Differential diagnosis
Ataxia has diverse causes, ranging from toxins (e.g., mercury), infections (e.g., Lyme disease), and neoplasms to hereditary degenerative causes (e.g., Friedreich's ataxia)(1). Friedreich's ataxia usually starts before 25 years of age. It most commonly presents with lower extremity symptoms including gait disturbances, diminishing reflexes, and loss of proprioception. Other symptoms (which can occasionally be presenting symptoms) include dysarthria, scoliosis, nystagmus, and foot deformities. Approximately 25% of patients have hypertrophic cardiomyopathy and 10% have diabetes mellitus .
Ataxia has diverse causes, ranging from toxins (e.g., mercury), infections (e.g., Lyme disease), and neoplasms to hereditary degenerative causes (e.g., Friedreich's ataxia)(1). Friedreich's ataxia usually starts before 25 years of age. It most commonly presents with lower extremity symptoms including gait disturbances, diminishing reflexes, and loss of proprioception. Other symptoms (which can occasionally be presenting symptoms) include dysarthria, scoliosis, nystagmus, and foot deformities. Approximately 25% of patients have hypertrophic cardiomyopathy and 10% have diabetes mellitus .
Clinical manifestations
The speed of the onset and the type of symptoms (symmetric vs. focal) can be very helpful in diagnosing the cause of ataxia.
A common example of acute symmetric ataxia is alcohol intoxication with its clumsiness, slurred speech, unbalanced gait, nystagmus, and inaccurate finger-to-nose testing. An acute and symmetrical onset would lead a clinician to suspect drugs, toxins, or infection. Examples of more chronic symmetrical ataxias include hypothyroidism, paraneoplastic disorders, inherited disorders, or vitamin B12 deficiency.
A rapid but focal onset would lead a clinician to suspect vascular or infectious causes. For example, the sudden onset of right-sided clumsy movements, the inward gaze of the right eye, and a headache would lead one to suspect a right-sided (cerebellar symptoms are ipsilateral) mass in the posterior fossa such as a hemorrhage or abscess.
A slower onset of focal or asymmetric findings would lead one to suspect neoplasms, multiple sclerosis, vascular lesions, or congenital malformations .
The speed of the onset and the type of symptoms (symmetric vs. focal) can be very helpful in diagnosing the cause of ataxia.
A common example of acute symmetric ataxia is alcohol intoxication with its clumsiness, slurred speech, unbalanced gait, nystagmus, and inaccurate finger-to-nose testing. An acute and symmetrical onset would lead a clinician to suspect drugs, toxins, or infection. Examples of more chronic symmetrical ataxias include hypothyroidism, paraneoplastic disorders, inherited disorders, or vitamin B12 deficiency.
A rapid but focal onset would lead a clinician to suspect vascular or infectious causes. For example, the sudden onset of right-sided clumsy movements, the inward gaze of the right eye, and a headache would lead one to suspect a right-sided (cerebellar symptoms are ipsilateral) mass in the posterior fossa such as a hemorrhage or abscess.
A slower onset of focal or asymmetric findings would lead one to suspect neoplasms, multiple sclerosis, vascular lesions, or congenital malformations .
