Ataxia It is a Greek term that means “disorder.” We refer to ataxia as a clinical sign characterized by lack of coordination of movement: lack of stability in walking; clumsiness or weakness in the upper limbs, lower limbs, body or eye movements, etc. as a consequence of an affectation of the Central Nervous System (CNS).
In general terms, ataxia is usually secondary to an affectation of the cerebellum or its efferent or afferent nervous pathways, although other brain structures could cause this symptomatology. In this article we will review the characteristics of this phenomenon.
Although the main characteristics of ataxia are incoordination of the limbs and saccadic eye movements, other types of symptoms may occur. All 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.
As we have said, in the clinic, Ataxia usually presents as a sign that can manifest itself in different acquired pathologies –that is, cerebral infarctions, tumors, craniocerebral trauma, etc.– although it can also occur as an isolated disease in its hereditary forms.
Classifications (types of ataxias)
We could classify ataxia following different criteria, although in this review We will explain the main types of ataxia depending 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 anomalies likely to produce 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 infarctions, cerebral anoxia (lack of oxygen in the brain), brain tumors, trauma, and 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 terms, For ataxia to occur, these pathologies must cause damage to the cerebellum or structures related to it such as the spinal cord, thalamus or dorsal root ganglia. A very common cause of ataxia is cerebellar hemorrhage.
History, case study, and appropriate selection of diagnostic tests are necessary to find the correct etiology. The treatment will be focused on the intervention of the acquired pathology and the prognosis will depend on the severity of the injuries.
2. Recessive hereditary ataxias
Unlike acquired ataxias, these types of ataxia usually begin early, during childhood or between 20 and 30 years of age. 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 not develop it. In this group we find some of the most common types of ataxia such as Friederich’s Ataxia or Ataxia-Telangiectasia.
2.1. Friedrich’s ataxia
It is the most common type of hereditary ataxia. Its prevalence in developed countries is estimated to be 1 person per 50,000 cases. Its onset is usually in childhood, presenting problems with gait, clumsiness, sensory neuropathy and abnormalities in eye movement. Other less frequent consequences may be skeletal deformities and hypertrophic cardiopathy.
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 after the onset of symptoms, the person loses the ability to walk.
This clinical picture is a consequence of the neurodegeneration of the dorsal root ganglion cells, the spinocerebellar tracts, the cells of the dentate nucleus – a deep nucleus of the cerebellum – and the corticospinal tracts. The Purkinge cells – the main cells of the cerebellum – are not affected. The neuroimaging study does not usually show any apparent involvement of the cerebellum.
Currently there is no cure and the treatments administered are usually symptomatic The risk due to dysphagia, cardiomyopathy, etc., means that patients must be monitored regularly. Various clinical trials are underway to observe the potential of various drugs such as, among others, interferon-gamma.
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 – involvement of the peripheral nervous system –, oculomotor apraxia – problems in changing gaze towards a stimulus that must be fixed on –, etc. Patients with AT often have immunodeficiencies that cause recurrent lung infections.
In the neuroimaging study, cerebellar atrophy can be observed, unlike Friederich’s ataxia As in the previous case, treatment is directed at the symptoms and there is no cure.
23. 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, infantile 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 of the parents 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 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 that must be made is to distinguish ataxia from apraxia Although they may entail 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 attentional deficits.
Ataxia, on the other hand, is a motor coordination deficit as such. Even if a patient cannot execute the action required by 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. Therefore, 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 at the national level
With the prevalence that we have cited in the case of ataxia in its hereditary form, we can consider these diseases as rare – in Europe a rare disease is one that occurs in one case every 2,000 people. When diseases are classified as rare, it is generally more difficult to advance their research to find effective treatments.
Furthermore, as we have seen, 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 Sevillian Association of Ataxias and the Madrid Association of Ataxias.
Conclusions
Ataxia, although not very prevalent in its hereditary manifestation, It is a disorder that affects activities of daily living and independence in the lives of many people, especially in the young population. Furthermore, pharmaceutical and business priorities mean that research in this field advances slowly, which is why 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 that this represents for the health system. The study and development in early detection and automation of treatment systems will be beneficial for patients, families, caregivers and health professionals. When we advance in these fields, we all win and, for this reason, we must publicize and support these social causes.
