We discovered a clinical sign that causes the inability to coordinate body movements.
Ataxia is a Greek term that means “disorder.” We refer to ataxia as a clinical sign characterized by incoordination of movement: lack of stability in gait; clumsiness or weakness in upper, lower extremities, body or eye movements, etc. as a consequence of an affectation of the Central Nervous System (CNS).
In general, ataxia is usually secondary to an involvement of the cerebellum or its efferent or afferent nerve pathways, although other brain structures could cause this symptomatology. In this article we will review the characteristics of this phenomenon.
Symptoms of ataxia
Although the main features of ataxia are incoordination of the extremities and saccades of the eyes, other types of symptoms can occur. All the symptoms of ataxia, however, have to do with the ability to move parts of the body. These signs that ataxia is affecting normal body functions are described below.
- Difficulties in visuospatial perception due to oculomotor incoordination.
- Visuoconstructive apraxia as a consequence of incoordination.
- Difficulties in walking, with a tendency to spread the legs.
- Total loss of ability to walk.
As we have said, in the clinic, ataxia usually appears as a sign that can manifest itself in different acquired pathologies – that is: cerebral infarcts, tumors, head trauma, etc. – although it can also present as an isolated disease in its forms hereditary.
Classifications (types of ataxias)
We could classify ataxia following different criteria, although in this review we will explain the main types of ataxia based on whether the pathology has been acquired or is hereditary. Another possible way of classification would be based on the regions of the Central Nervous System that present lesions or abnormalities that can cause ataxia.
1. Acquired ataxias
That an ataxia is acquired implies that it occurs as a consequence of a main pathology suffered by the patient. Thus, cerebral infarcts, cerebral anoxia –a lack of oxygen in the brain–, brain tumors, trauma, demyelinating disease –multiple sclerosis– are common causes of ataxia.
Among other less common causes we could find congenital anomalies, infections, other autoimmune diseases, Human Immunodeficiency Virus, Creutzfeldt-Jakob disease, etc. In general, for ataxia to occur, these pathologies must cause damage to the cerebellum or related structures such as the spinal cord, thalamus, or dorsal root ganglia. A very common cause of ataxia is cerebellar hemorrhage.
The anamnesis, the case study, and the appropriate selection of diagnostic tests are necessary to find the correct etiology. Treatment will be focused on the intervention of the acquired pathology and the prognosis will depend on the severity of the injuries.
2. Hereditary recessive ataxias
Unlike acquired ataxias, these types of ataxia tend to have early onset, during childhood or between the ages of 20 and 30. That the disease is recessive implies that we must have inherited two equal copies of the “defective” gene from our parents.
This implies that a large population is simply a carrier of the disease even if it does not manifest itself, since a “healthy” gene is enough to avoid developing it. In this group we find some of the most common types of ataxia such as Friederich’s Ataxia or Ataxia-Telangiectasia.
2.1. Friederich’s ataxia
It is the most common type of hereditary ataxia. Its prevalence in developed countries is estimated to be 1 person in every 50,000 cases. Its onset is usually in childhood, presenting problems in walking, clumsiness, sensory neuropathy and abnormalities in the movement of the eyes. Other less frequent consequences can be skeletal deformations and hypertrophic myocardipathy.
As the disease progresses, dysarthria –alteration in the articulation of words–, dysphagia –difficulty in swallowing–, weakness in the lower extremities, etc. they are more apparent. It is estimated that between 9 and 15 years from the onset of symptoms the person loses the ability to walk.
This clinical picture is a consequence of neurodegeneration of the ganglion cells of the dorsal root, the spinocerebellar tracts, the cells of the dentate nucleus – a deep nucleus of the cerebellum – and the corticospinal tracts. Purkinge cells – the main cells of the cerebellum – are not affected. The neuroimaging study does not usually show any apparent involvement of the cerebellum.
There is currently no cure and the treatments administered are usually symptomatic. The risk due to dysphagia, cardiomyopathy, etc., implies that patients must be regularly monitored. Various clinical trials are underway to observe the potential of various drugs such as interferon-gamma, among others.
With an estimated prevalence of 1 case in 20,000-100,000 cases, ataxia-telanigectasia (AT) is the most common cause of recessive ataxia in patients under 5 years of age. As the disease develops, we can find hypotonia –decreased muscle tone–, polyneuropathy –peripheral nervous system involvement–, oculomotor apraxia –problems in changing the gaze towards a stimulus that must be fixed, etc. Patients with AT often have immunodeficiencies that cause recurrent lung infections.
In the neuroimaging study, atrophy of the cerebellum can be observed, unlike Friederich’s ataxia. As in the previous case, the treatment is aimed at the symptoms and there is no cure.
2.3. Other recessive hereditary ataxias
We find many more types of hereditary ataxias such as Ataxia with oculomotor apraxia, Cayman Ataxia, Ataxia with vitamin E deficiency, Childhood spinocerebral ataxia, etc.
3. Dominant hereditary ataxia
Dominant hereditary ataxias occur in each generation of a family with a 50% risk of receiving the disease from one parent. In this case, a single copy of the affected gene is enough to develop the disease. Depending on the course of the disease, they can be divided into episodic or progressive. There are different genetic tests for the diagnosis of these pathologies. As in the previous cases, there are no cures either.
Ataxia and Apraxia: They are not the same
From a neuropsychological point of view, the major differential diagnosis to be made is to distinguish ataxia from apraxia. Although they can lead to similar cognitive deficits, especially in acquired forms, they are significantly different from a clinical point of view. Apraxia is defined as an alteration in the execution of certain learned movements in response to an order and out of context that is not attributable to sensory or motor impairments, lack of coordination or attention deficits.
Ataxia, on the other hand, is a motor coordination deficit as such. Although a patient cannot perform the required action upon an order, it will be due to motor disability. In apraxia the problem arises because the “verbal input” –that is, the command– cannot be associated with the motor response or “motor output”.
On the other hand , in apraxia we should not find other problems such as gait instability, swallowing problems, etc. Thus, in these cases, neurological evaluation will be mandatory if we observe signs incompatible with apraxia. However, it should also be taken into account that both clinical manifestations can occur concomitantly.
The incidence of ataxia nationwide
With the prevalences that we have cited in the case of ataxia in its hereditary form, we can consider these diseases as rare – in Europe being a rare disease one that occurs every 2000 people. When diseases are rated as rare it is generally more difficult to advance your research to find effective treatments.
In addition, as we have seen, the hereditary forms of the disease mainly affect children and young people. This has led to the emergence of various non-profit associations that promote the treatment, dissemination and improvement of the quality of life of these patients. Among them we find the Catalan Association of Hereditary Ataxias, the Sevillana Association of Ataxias and the Madrid Association of Ataxias.
Ataxia, although not very prevalent in its hereditary manifestation, is a disorder that affects the activities of daily living and independence in the lives of many people, especially in the young population. In addition, pharmaceutical and business priorities make research in this field slow, so treatment proposals focus on palliative care.
That is why its existence must be disclosed and its effects made known. Each step, no matter how small, can represent improvements in the quality of life of these patients, with the relief for the health system that this implies. The study and development of early detection and the automation of treatment systems will be beneficial for patients, families, caregivers and health professionals. When we advance in these fields, we all come out ahead and, for this reason, we must make known and support these social causes.
- Arnedo A, Bembire J, Tiviño M (2012). Neuropsychology through clinical cases. Madrid: Editorial Médica Panamericana.
- Junqué C (2014). Neuropsychology Manual. Barcelona: Synthesis
- Akbar U, Ashizawa T (2015). Ataxia. Neurol Clin 33: 225-248.
- Delatycki MB, Williamson R, Forrest SM (2000). Friedreich ataxia: an overview. Journal of medical genetics 37: 1–8.
- Manto M, Marmolino D (2009). Cerebellar ataxias. Current opinion in neurology 22: 419–429.
- Matthews BR, Jones LK, Saad DA, Aksamit AJ, Josephs KA (2005). Cerebellar ataxia and central nervous system whipple disease. Archives of neurology 62: 618–620.
- Pandolfo M (2009). Friedreich ataxia: the clinical picture. J Neurol 256 (Suppl 1): 3–8.