Cerebellar Lesions

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