The cerebellum plays a role in coordinating movements, and its dysfunction may cause incoordinated movements, which is called ataxia. The cerebellum has extensive connections with the spinal cord, the brainstem, and the cerebrum. The cerebellum receives information about the motor plan from the cerebrum, with details about planned muscle contractions, and also about how movements are occurring in real time from the spinal cord and brainstem. It then sends feedback information to other motor areas of the cerebrum and brainstem to make movements smoother and more accurate. Incoordinated movements may occur with abnormalities of either the cerebellum or its connections, leading to gait ataxia (incoordinated walking) or limb ataxia (incoordinated limb movements).
The term lateral means away from the midline of the body, which separates the right and left halves, and the term medial means toward the midline. The lateral cerebellum is involved in coordinating movements mostly for the ipsilateral limbs, so that a lateral cerebellar lesion often causes ataxia of the ipsilateral arm and leg. The medial cerebellum is involved in coordinating the movements of walking, so that a medial cerebellar lesion often causes gait ataxia.