Sensorimotor mapping of the human cerebellum during pineal region surgery.

Background: The cerebellum is a fundamental structure of the central nervous system. However, in humans, its anatomo-functional organization and the processes through which this organization adapts in response to injuries remain widely unknown.

Methods: Motor and somatosensory evoked potentials were used to map functional representations in the posterior cerebellum of patients with extra- and intracellebellar injuries. Extracerebellar patients had injuries outside the cerebellum (e.g. pineal region, quadrigeminal plate) while intracerebellar patients had injuries within the cerebellum. Data were collected in 20 extracerebellar patients for motor representations. Only preliminary data were gathered for somatosensory representations and intracerebellar patients.

Results: In extracerebellar patients, electrical stimulation induced muscle contractions in the ipsilateral hemibody. These representations were somatotopically organized with large overlaps between the face and upper limb in the superior posterior cerebellum and the upper and lower limb in the inferior posterior cerebellum. Neck muscles were represented in the oculomotor vermis. In intracerebellar patients, preliminary data seem to indicate that motor plasticity is achieved by recruiting the contralesional (healthy) cerebellar hemisphere.

Conclusions: Although still ongoing, this project could eventually lead to an improvement of the surgical treatment of patients with lesions of the posterior fossa, by improving our knowledge of cerebellar organization and the process of post-lesional plasticity.