Principles in localizing a cerebellar lesion
What are the general principles in localizing a cerebellar lesion?
Lesions of the midline impair coordination involving stance and gait.
Lateral lesions impair the limbs ipsilateral to the cerebellar lesion.
Lesions of the cerebellar hemisphere impair movement ipsilaterally due to three major decussations. With movement initiation, corticopontine fibers synapse in the pons → cross in the MCP (first decussation) via the pontocerebellar fibers → cerebellum → cross back to the red nucleus via the SCP decussation (second) → cerebral cortex. With movement execution, the corticospinal tracts cross at the decussation of the pyramids (third) in the medullocervical junction. Hence, a left cerebellar hemispheric lesion causes a deficit in the left hemibody by influencing movement(s) originating in the right cerebral cortex.
Lesions of the afferent or efferent pathways may also cause cerebellar signs.
• Lesions of the SCP and the deep nuclei usually produce the most severe disturbances.