Ataxia By Abdikayimova Gulzat

Article on ataxia – classification and management Abhinav Kumar Sharma Under the guidance of Abdikyimova Gulzat Mam (Faculty of Neurology) Professor - Osh State University, IMF Kyrgyzstan Abstract Ataxia has been described as incoordination of voluntary movements and abnormal postural control. There are many different statements concerning the definition, range and nomenclature of ataxia. Different clinical findings, exposure to different neurological structures and different causes lead to the occurrence of each ataxia type. In most cases, treatment of ataxia is not available and supportive treatment should be applied for the management of ataxia symptoms. Ataxia usually follows a trauma to the cerebellum and its tracts like the vestibular, proprioceptive and visual systems. Clinically, the ataxias can be further classified into cerebellar, vestibular, sensory, frontal, optic, visual, mixed ataxia and ataxic-hemiparesis. Etiologically, the ataxias can be categorized into hereditary ataxias, sporadic degenerative ataxias and acquired ataxias. Genetic forms of ataxia must be distinguished from the acquired ataxias like chronic alcoholism, cerebrovascular disease, various toxins agents, immune-mediated inflammation, vitamin deficiency, and persistent central nervous system infections. Once the acquired causes are treated, as ataxia is generally resistant to therapy, the treatment is supportive but may involve physical, occupational, and speech therapy. Introduction The word ataxia is greek in origin (a- negative prefix and taxia to set in order), meaning "Not in order." In medicine, it is utilized to describe loss of coordination and poor postural control. It's an inexact clinical indicator of dysfunction of the cerebellum and/or its connections such as the proprioceptive, visual, vestibular systems and interrelationships between the systems. There are numerous possible causes for these patterns of neurological dysfunction (1, 2). In this review, the neuroanatomic foundation, forms etiologies, and management of ataxia are detailed in the light of the literature. Pathogenesis Ataxia is an impairment of muscle coordination during voluntary movement and impaired postural control. Ataxia usually results from an injury to the cerebellum and its tracts. The main function of the cerebellum is to obtain balance and coordination. Based on the information presented by the vestibular, visual, somatosensory systems and cerebral cortex, the cerebellum generates postural control, balanced and coordinated movement by adjusting accordingly. The vestibulocerebellum acquires eye movements and balance by way of vestibuloocular, vestibulospinal and reticulospinal tracts through the regulation of information in the vestibular and the reticular nuclei. Spinocerebellum receives proprioceptive sensory inputs from the periphery, and regulates movement of body and limb, and is also responsible for locomotion, balance and tonus. Cerebrocerebellum is connected to the cerebral cortex, and is involved in the planning of movement and in evaluating sensory information for action, allowing for precise, coordinated distal movement. In contrast, the cerebrocerebellum has a role in motor control as well as in emotion and cognition. Therefore, the cerebellum is involved with balance and posture maintenance, control of eye movement, planning and execution of coordinated limb movements, motor performance adjustments, learning of new motor tasks, cognitive function and neuroimmunomodulation. Lesion of the cerebellum and/or its connections results in ataxia, oculomotor disturbances, dysmetria, dyssynergia, dysarthria, tremor, hypotonia, prolonged reaction time, and cognitive deficit termed “dysmetria of thought” (2-5). Types of ataxia Ataxia can result from damage to the cerebellum, proprioceptive, vestibular and visual pathways, and/or any interconnection between these pathways. Although there has been no consensus concerning classification of ataxias in literature, depending on system involvement, ataaxias are classified into following: 1. Cerebellar ataxia 2. Vestibular ataxia 3. Sensory ataxia 4. Frontal ataxia 5. Ataxic-hemiparesis 6. Optic ataxia 7. Visual ataxia 8. Mixed ataxia Cerebellar ataxia The designation cerebellar ataxia is employed to describe ataxia due to malfunction of the cerebellum. Ataxia, hypotonia, asynergy, dysmetria, dyschronometria, nystagmus, dysdiadochokinesia, tremor, and cognitive malfunction are features of cerebellar dysfunctions. Where and how these abnormalities manifest themselves will depend on which of the cerebellar structures, i.e., vestibulocerebellum, spinocerebellum or cerebrocerebellum, have been damaged(6). Vestibulocerebellum (flocculonodular lobe) malfunction is marked by vertigo imbalance and abnormal eye movements. This appears as postural instability in an attempt to increase the base. Instability is thus aggravated while standing with the feet together, whether the eyes are open or closed. Some of the eye movement abnormalities like gaze-evoked nystagmus, rebound nystagmus, ocular dysmetria, inability to inhibit the vestibulo-ocular reflex and abnormalities of optokinetic nystagmus are also observed (7). Spinocerebellar (vermis and paravermis) dysfunction manifests as a broad-based "Drunken sailor" Gait referred to as truncal ataxia, characterized by uncertain starts and stops, lateral deviations, and unequal steps, and gait ataxia (8). Cerebrocerebellar dysfunction manifests as disturbances in the execution of voluntary, planned movements by the extremities. These include: Intentional tremor, writing difficulty, dysarthria, dysmetria, abnormality of alternating movements, loss of check reflex, and hypotonia. Intention tremor is a kinetic tremor that appears as a broad, course, and low frequency (less than 5 hz) tremor. The amplitude of an intention tremor increases as anextremity approaches the endpoint of voluntary and visually guided movement. Intention tremor is caused by dysfunction of the lateral zone of the cerebellum, and superior cerebellar peduncle. Intention tremors can also be seen as a result of damage to the brainstem or thalamus. Depending on the location of cerebellar damage, these tremors can be either unilateral or bilateral. Kinetic and postural tremors or titubations also occur in cerebellar diseases. There are also writing abnormalities in cerebellar ataxia characterized by large, unequal letters, and irregular underlining. Cerebellar dysarthria is characterized by slurred, monotonous or scanning speech. Dysmetria is inability to judge distances or ranges of movement, as undershooting (hypometria), or overshooting (hypermetria), the required distance or range to reach a target. Breakdown of alternating movements known as asynergia or dyssynergia characterizes defects in the sequence and timing of the constituent parts of a movement. Dysdiadochokinesia can entail rapid altering between pronation and supination of the forearm. Bradyteleokinesia is terminal slowing in reaching the target. Rebound phenomenon is also sometimes seen in patients with cerebellar ataxia. Hypotonia and hyporeflexia, pendular tendon reflexes are also seen in acute cerebellar lesion (2,6,8). Vestibular ataxia Vestibular ataxia follows as a result of vestibular dysfunction. Its clinical presentation is based on the speed of lesion development, extent of the lesion such as unilateral or bilateral, and the state of vestibular compensation. Vestibular dysfunction caused by acute-onset unilateral lesion is characterized by severe vertigo, nausea, vomiting, blurred vision and nystagmus. In slow-onset, chronic bilateral vestibular dysfunction cases, these symptoms are absent and dysequilibrium may be the sole presentation (6). Vestibular ataxia produces gross difficulties with gait and balance reactions in sitting and standing. Sudden vertigo may be associated with an inability to walk or even to stand. The patient stumbles on walking, has a broad base support and can lean backwards or to the side of the lesion. Head and trunk motion and subsequently arm motion are often diminished because of vertigo (9). The equilibrium in vestibular ataxia is perturbed when performing a head or eye movement. Ataxia may be provoked by asking them to move the head from side to side while walking. Balance on one foot or walking parallel with open or closed eyes may also be disrupted (10). In addition, the patient with vestibular dysfunction depend to a large degree on visual input, so shutting the eyes highlights the gait disorder. Since vestibular ataxia is gravity-dependent, limb movement incoordination cannot be elicited when the patient is tested in the recumbent position but appears when the patient attempts to stand or walk. Extremity ataxia is by no means evident in vestibular ataxia (11). Vestibular dysfunction also includes spontaneous or positional nystagmus, robotic gait ataxia with head turning, and on difficulty in balancing on one foot or on a complaint surface with eyes closed. Nystagmus is often encountered in unilateral peripheral vestibular lesion, typically unidirectional, and mostly most prominent on gaze away from the side of vestibular lesion. Head-shaking nystagmus is another helpful finding to diagnose patients with unilateral vestibular hypofunction. The head-thrust test is positive in peripheral Vestibular disorders. Dix-hallpike test is important,particularly when paroxysmal positional vertigois being tested. Central vestibular disorders also result indeficits in eye movement conjugation, saccadic pursuitand horizontal optokinetic abnormalities, spontaneous or positional central nystagmus,failure of suppression of fixation, slowing of thenystagmus fast phases, slowing of the nystagmus slow phases,retraction of nystagmus, perverted nystagmus, verticaloptokinetic abnormalities, and retraction Nystagmus. Deep tendon reflexes are normal, an