In the absence of muscle weakness, the disorder of coordinated movements of limb movements, unstable and uncoordinated, is called ataxia. Etiology and mechanism Any simple movement of the body must involve the participation of four groups of muscles: active, antagonistic, synergistic and fixed muscles to complete, and depends on the coordination and balance of the nervous system. The thin and cuneate tracts of the posterior spinal cord run the entire length of the spinal cord, with the thin tracts conducting deep sensation in the lower trunk and both lower extremities, and the cuneate tracts conducting deep sensation in the upper trunk and both upper extremities. Fibers from the posterior cord cross in the medulla oblongata and travel through the thalamus to the cerebral cortex, where the posterior tract transmits deep sensations in muscles, joints and tendons, the position of the limbs in space, the force and range of motion impulses of the limbs, and partial and two-point discrimination sensations. The anterior rotor system transmits balance information centripetally and elicits balance responses. The cerebellum is an important center for the maintenance of somatic balance, ataxia, and muscle tone. The functions of these structures are in turn under the unified control of the cerebral cortex. Ataxia can occur in deep sensory, anterior rotatory system, cerebral and superior cerebral lesions, which are called sensory, anterior rotatory, cerebellar and cerebral ataxias, respectively. Clinical manifestations 1, sensory ataxia: ataxia is reduced when the eyes are open, intensified when the eyes are closed, accompanied by position perception, vibration perception is reduced or disappeared. Because deep sensory disorder is common in the lower extremities, standing instability and gait instability are the main manifestations. The patient has difficulty walking at night, and the torso tends to fall toward the washbasin when washing the face (positive washbasin sign). When walking, the eyes look at the ground and raise the feet too high, the step distance is wide, and the step on the ground is too heavy, which is like crossing the threshold, so it is called cross-threshold gait. The closed-eye difficult-to-stand sign is positive, the finger-nose test and the heel-knee-shin test are incorrect. 2, cerebellar ataxia: cerebellar and its afferent and efferent fiber lesions can cause ataxia, characterized by both balance disorders of the trunk and unstable standing, and ataxia of the limbs and poor distance discrimination, alternating movement disorders, coordination, delayed movement onset and termination, or continuity disorders. Cerebellar ataxia is not affected by eye opening, eye closure or illumination, and is not accompanied by sensory impairment, but by nystagmus, dysarthria, nonsense and a specific cerebellar gait, i.e., walking with two feet apart, with different gait sizes, and with an unstable gait that tends to fall. During the finger-nose test, the ataxia is extremely obvious, and the upper limbs are seen to be in an arc of oscillation with intentional tremor, and there is hypotonia or loss of muscle tone, excessive joint movement, fast reactive movement disorder, and muscle rebound phenomenon. 3, vestibular ataxia: caused by damage to the vestibular system, mainly due to balance disorders. Characterized by balance disorders at rest and during movement. It has the same points as cerebellar ataxia, such as wide base of both feet when standing, unstable body, leaning to the side or back, and skewing when walking. However, there are obvious vertigo, nystagmus and abnormal vestibular function test to differentiate them. 4.Hereditary ataxia: It is a chronic disease of the central nervous system with unknown etiology, mostly with family history, autosomal recessive or dominant inheritance, and occasionally with companionship. The pathological changes are mainly degeneration of the spinal cord, cerebellum and brainstem, and peripheral nerves, optic nerve, brain and cerebellum can also be involved. Ataxia and poor distance discrimination are the main clinical manifestations.