Cerebellar Lesions

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Cerebellar Lesions The cerebellum integrates sensory and other inputs to coordinate ongoing movements and participate in motor planning. The cerebellum has no direct connections to the lower motor neurons but modulates motor function through upper motor neurons. The Vermis and flocculonodular lobes regulate balance and eye movements via connections with vestibular nuclei and oculomotor system, these regions control the medial motor systems. The more lateral areas of the cerebellum control muscles of extremities, the most lateral areas control function in motor planning. (Chapter 15 Cerebellum) When cerebellar lesions occur they produce ataxia (irregular uncoordinated movement.) Ataxia occurs ipsilateral to the side of the cerebellar injury. Midline cerebellar lesions cause unsteady gate (truncal ataxia) and eye movement abnormalities (nystagymas), which are often accompanied by vertigo, nausea and vomiting. Lateral cerebellar lesions cause limb ataxia. (Chapter 15 Cerebellum) Patients with cerebellar damage, regardless of the cause or location, exhibit persistent errors in movement. These movement errors are always on the same side of the body as the damage to the cerebellum, reflecting the cerebellum's unusual status as a brain structure in which sensory and motor information is represented ipsilateral rather than contra laterally. Furthermore, somatic, visual, and other inputs are represented topographically within the cerebellum; as a result, the movement deficits may be quite specific. For example, one of the most common cerebellar syndromes is caused by degeneration in the anterior portion of the cerebellar cortex in patients with a long history of alcohol abuse. Such damage specifically affects movement in the lower limbs, which are represented in the anterior spinocerebellum. The consequences include a wide and staggering gait, with little impairment of arm or hand movements. Thus, the topographical organization of the cerebellum allows cerebellar damage to disrupt the coordination of movements performed by some muscle groups but not others. The implication of these pathologies is that the cerebellum is normally capable of integrating the moment-to-moment actions of muscles and joints throughout the body to ensure the smooth execution of a full range of motor behaviors. Thus, cerebellar lesions lead first and foremost to a lack of coordination of ongoing movements. For example, damage to the vestibulocerebellum impairs the ability to stand upright and maintain the direction of gaze. The eyes have difficulty

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