Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_24_библиотеки_им_акад_М_И_Перельмана

The eld of clinical ataxiology encompasses three main domains: the vestibulo-cerebellar syndrome (VCS), the cerebellar motor syndrome (CMS), and the cerebellar cognitive-affective syndrome/Schmahmann’s syndrome (CCAS/SS). This subdivision in three main cerebellar clinical functions meets the anatomy, the neuroimaging data, and the clinical observations. Indeed, studies of cerebro-cerebellar connectivity conrm that the three clinical domains are based upon anatomically distinct communication systems within the central nervous sys­tem, with selective involvement of the various cerebellar lobules in given oculomotor, motor, or cognitive tasks. Cerebro-cerebellar loops run in parallel and are arranged topographically. The lobules I–V and the adjacent parts of lobule VI and lobule VIII are mainly engaged with motor control. The lobules VI and VII modulate supramodal higher-order functions. The literature has converged towards a task-dependent engagement of specic cerebel­lar areas. Several standardized clinical scales have been developed for the assessment of VCS and CCAS/SS, but we still miss a detailed rating scale dedicated to the VCS.The development and validation of such scale will have important implications from a diagnostic and fol­low- up standpoint of patients, as well as for future clinical trials. Cerebellar functional topography has reached maturity and is entering in the clinical routine of ataxiologists.

Details on cerebellar anatomy from a macro- or microana­tomic perspective are presented in other chapters of this book. We focus in this section on specic parts of its com­plex structural and functional organization, in order to clarify the neuroanatomy behind the three clinical syndromes reported above.

(c) The cognitive cerebellum is mainly located in the poste-

internal forward models (Molinari et al. 2009; Molinari

2016; Lawrenson etal. 2018; D’Angelo 2018). In terms of

motor control, it is now assumed that the cerebellum regu­lates intra- or inter-limb co-contractions/alternate contrac­tions with a precise timing to coordinate limb movements, in order to achieve successfully complex motor behaviors such as upright standing, gait, or reaching (Bareš et al. 2019). Expectations and estimates of future motor states are essen­tial to perform fast movements with accuracy. These accurate predictions decrease the dependence on time-delayed sen­sory signals, the inferior olive monitoring the errors by com-

The ataxic motor symptoms would occur in case of failure to implement predictions within the motor loops. In terms of cognitive operations, the constellation of cog-

At a cognitive level, cerebellar disorders result in a mismatch between reality and perceived reality. Decits observed in CCAS/SS include impaired executive functions (planning, abstract reasoning, verbal uency, working memory) and spatial cognition dysfunction, linguistic difculties, or per­sonality changes with a dysregulation of affect. Visuospatial disintegration results in errors in sequences required for drawing. Verbal uency decits range from telegraphic speech to mutism. Cerebellar patients may also present neu­ropsychiatric features in the spheres of attentional control, emotions, and social skill sets (Argyropoulos etal. 2020). Patients may appear with overfamiliarity, impulsivity, and aberrant behavior. These observations provide a framework to the understanding the neuropsychiatry of the cerebellum and open perspectives to elucidate disorders of social com­munication such as autism (Schmahmann 1998; Baumann etal. 2015; Bodranghien etal. 2016).

Cerebellum dysfunction can be evaluated using clinical rat­ing scales. These scales allow the objective evaluation of ataxic patients, grading severity of the disease for a proper clinical follow-up (Bodranghien et al. 2016). The rating scales remain the most robust clinical method for the assess­ment of cerebellar patients.

syndromes have a distinct neuroanatomical foundation in terms of connectivity with the cerebral cortex, brainstem nuclei, and spinal cord. The elucidation of the neuroanatomy of cerebellar pathways has been the substratum of our cur­rent understanding of cerebellar clinical neuroscience. Cerebellum appears now as a critical node interconnected with numerous loops including the spinal cord, motor cortex, and cerebral association areas.

Cerebellar research of these last two centuries has clari­ed our appraisal of cerebellar decits observed in daily practice. Errors in predictions likely subserve the clinical symptoms in the three cerebellar syndromes. This is in agree­ment with the pioneering universal cerebellar transform (UCT) hypothesis which has been put forward by Schmahmann (Schmahmann 2019). According to this the­ory, cerebellum maintains a behavior around a homeostatic baseline in a given sensorimotor or behavioral context, in an automatic manner without conscious awareness and on the basis of the connectivity. In other words, the cerebellum per­forms unique computations in a topographically arranged

manner. Errors results in CVS, CMS, and/or CCAS/SS.The uniform histology of the cerebellum is a major underpinning of the UCT and cerebellar lesions result in a universal symp­tom, dysmetria, which affects oculomotor control, motor control of limbs and/or cognitive/affective/emotional control according to the topography of the lesion(s). The streams of information which are affected can be predicted on the basis of the neuroanatomy.

nal version of the manuscript.