Sensitive ataxia is a disorder of sensory perception of pressure, vibration and body position in space, leading to discoordination and motor disorders. It is manifested by a disorder of gait and coordination, hypotension of skeletal muscles, pseudoathetosis of the distal extremities. Sensitive ataxia is diagnosed based on neurological status. To identify its etiology, a biochemical blood test, neurophysiological testing, CT or MRI of the brain and spinal cord, genetic studies are carried out. Etiotropic therapy of diseases, the symptom of which is sensitive ataxia, is not always possible. Neurometabolic treatment (anticholinesterase agents, B vitamins, ATP), physical therapy, massage is carried out.
General information
Sensitive ataxia is associated with a disorder of deep (proprioceptive) types of sensitivity, which include: musculoskeletal sense, perceiving information about the position of the human body in the surrounding space; vibration sensitivity; feeling of mass and pressure. Motor and coordination disorders in this variant of ataxia occur due to the fact that the central parts of the proprioceptive system stop receiving kinesthetic signals that give information, including about muscle contractions. Sensitive ataxia is not an independent nosology, it acts as a symptom complex in a number of neurological diseases. In each individual case, its manifestations depend on the topical features of the lesion of the proprioceptive nerve pathways.
The structure of the proprioceptive system
The first sensory neurons of these pathways are localized in the spinal nodes. Their receptors are located in the muscles (Kuehne corpuscles), tendons (Golgi-Mazzoni receptors), papillary layer of the skin (Meissner corpuscles). Impulses from the receptors along the peripheral nerves go to the first neurons. The axons of the latter pass into the spinal cord through the posterior roots and form the conducting paths of Goll and Burdach running in the posterior ropes of the same side. The Gaulle path, or thin bundle, is formed by axons coming from the lower parts (legs) and occupies a more medial position. The Burdach pathway, or wedge-shaped bundle, is formed due to the axons of the upstream sections (arms) and passes laterally to the Gaulle path.
Passing in the posterior spinal columns from the bottom up, the fibers of proprioceptive sensitivity reach the medulla oblongata. The impulses going through them are transmitted to the second sensory neurons located in the nuclei of the posterior pillars of the medulla oblongata. The axons of the second neurons cross over to the other side and go to the ventrolateral nucleus of the thalamus (visual hillock), where the third neurons of the proprioceptive pathway are located, the axons of which end in the cortex of the parietal lobe and precentral gyrus. At the same time, part of the axons of the second proprioceptive neurons goes to the cerebellum and participates in ensuring coordination of movements.
Causes
Sensitive ataxia is caused by damage to the pathways of proprioceptive (deep) sensitivity. The pathological process can be localized in various parts of the proprioceptive system: in the posterior columns of the spinal cord, spinal ganglia, posterior spinal roots, at the level of the medulla oblongata, thalamus, cerebral cortex. Damage to the proprioceptive tract can be caused by vascular catastrophes (spinal or cerebral stroke), funicular myelosis, myelitis of various etiologies, spinal cord tumor, cerebral tumor, spinal dryness in neurosyphilis, multiple sclerosis, spinal injury.
In some cases, sensitive ataxia occurs as a complication of spinal surgery or brain surgery. The defeat of the peripheral parts of the proprioceptive system is observed in Guillain-Barre syndrome and various variants of polyneuropathy: diabetic, alcoholic, infectious-toxic, amyloid, etc. In addition, sensitive ataxia can be a symptom of some genetically determined diseases, for example, Fredreich’s ataxia.
Symptoms
Sensitive ataxia is manifested by a disorder of the sensation of movement of one’s own body. First of all, this is reflected in the patient’s gait. The patient puts his legs disproportionately wide, excessively bends and overextends them at the knees and hip joints, hits the floor with his heel with force. In clinical neurology, such a gait is called “tabetic” or “stamping”. The patients themselves characterize their feelings when walking as “walking on cotton wool” or “sinking”. Patients try to compensate for proprioceptive deficiency with enhanced visual control. They walk looking right at their feet, for which they have to tilt their head down. In the absence of vision control, gait disorders are significantly aggravated. For this reason, patients cannot walk in the dark or with their eyes closed.
Sensitive ataxia in the hands is manifested by a violation of arbitrary movements and coordination, which make it difficult to perform the most mundane actions. So, the patient cannot insert the key into the lock, fasten the button, bring a cup of drink to his mouth without spilling it. At rest, chaotic involuntary movements of the fingers of the hands are noted, resembling athetosis — violent movements caused by damage to the subcortical cerebral centers. Unlike true athetosis, which increases with active motor acts, sensitive pseudo-athetosis disappears during voluntary movements.
Sensitive ataxia has a different clinical picture depending on the topic of damage to the proprioceptive pathways. Pathological changes in the posterior columns at the level of the lumbar and thoracic segments lead to the occurrence of ataxia only in the lower extremities. When the posterior pillars are affected above the cervical thickening, sensitive ataxia manifests itself both in the legs and in the arms. Unilateral damage to the proprioceptive tract before the transition of its fibers to the opposite side leads to homolateral hemiataxia — manifestations of ataxia in half of the body on the side of the pathological process. Unilateral damage to the pathways of deep sensitivity after their intersection is accompanied by heterolateral hemiataxia — ataxia in the extremities of the opposite half of the body to the focus.
Diagnostics
Sensitive ataxia is easily detected by a neurologist during a neurological examination. There is muscle hypotension in the extensors and flexors of the affected limbs, loss of deep types of sensitivity. In the Romberg pose, there is a stagger, which increases significantly when the eyes are closed. When holding outstretched arms, pseudoathetosis occurs. Coordination tests are disrupted: the patient does not get his finger into the tip of his nose, cannot precisely put the heel of one foot to the knee of the other. An attempt to run along the crest of the tibia of one leg with the heel of the other leg is carried out jerkily and is accompanied by deviations of the heel in different directions. A characteristic tabetic gait is noted.
In the neurological status, along with ataxia, other types of neurological deficits and general cerebral symptoms due to the underlying disease may be noted. Sensitive ataxia requires differentiation, first of all, from other types of ataxia. Its main difference is a significant increase in symptoms when closing the eyes. At the same time, it should be borne in mind that mixed forms of ataxia are possible, for example, sensitive cerebellar.
The main task of instrumental examinations is to identify the cause of ataxia. For this purpose, the patient may be prescribed blood biochemistry, EEG, MRI of the brain, CT and MRI of the spine, electroneurography, evoked potentials, electromyography. If you suspect the hereditary nature of the disease, you need to consult a geneticist with DNA analysis and genealogical research.
Treatment and prognosis
Sensitive ataxia needs etiotropic and symptomatic therapy. The primary task is to stop the pathological process. With its infectious etiology, antibacterial therapy is required, with vascular — vasoactive or hemostatic. With funicular myelosis, vitamin B12 is administered according to the scheme. When diagnosing a tumor, together with a neurosurgeon, they decide on the possibility of its removal.
Symptomatic treatment involves maintaining optimal metabolic conditions in the nervous tissue to increase its resistance to pathological changes and its ability to recover. Neurometabolic therapy involves the introduction of ATP, anticholinesterase pharmaceuticals (galantamine, proserin), vitamins g. V. An integral part of the treatment is physical therapy and massage. Physical therapy allows you to improve coordination of movements through training, in combination with massage, it strengthens the muscles.
Sensitive ataxia has a favorable prognosis in cases where it is possible to eliminate the cause of the disease and restore the affected area of the proprioceptive tract. With the hereditary nature of ataxia, tumor processes, the formation of persistent degenerative foci, the prognosis for recovery is unfavorable. In such cases, treatment is aimed at stopping the progression of the pathological process and training the patient’s motor skills.