The symptoms of post-operative pediatric CMS are thought to be caused by damage/disturbances of various parts of the cerebellum, as well as cerebello-cerebral pathways passing through the brainstem. This can result in secondary affection of supratentorial brain areas by means of diaschisis, where damage in one part of the brain (cerebellum/brainstem in this case) results in functional disturbances in anatomically distant, yet neuronally connected parts of the brain (the cerebrum) due to lack of excitatory impulses [1, 2, 3].
Dentato-thalamo-cortical pathway: Cerebellar mutism is thought to be caused by bilateral damage to the dentate nuclei and/or their efferents (DTC-pathway) [4, 5, 6, 7]. Recent research points to the right DTC-pathway as being more important in this context [8, 9, 10] which makes sense as it terminates in the left cerebral hemisphere that contains two major language areas. Although mutism is known to result from damages anywhere along the path , the main focus areas when it comes to posterior fossa operations have been the dentate nuclei themselves and the proximal part of their outflow tracts (i.e. superior cerebellar peduncles and mesencephalic tegmentum) [12, 13, 20, 21].
Cerebellum: Neurological/motor symptoms such as ataxia, tremor, dysmetria, dysarthria, oculomotor abnormalities and problems with orofacial, arm and leg movements are caused by damage to the anterior lobe and posterior lobule VI and VIII of the cerebellum [14, 15], but the anatomical substrates of hypotonia, hemiparesis, urinary retention and urinary/fecal incontinence have not been elucidated. Cognitive symptoms and language problems are caused by damage to the posterior lobe. There is some lateralization of function with lobule VI, VIIB and Crus I of the left cerebellar hemisphere being important for executive skills and visual processing, and lobules VI, VIIA and Crus I of the right cerebellar hemisphere for language and verbal working memory [7, 14, 16]. Affective/behavioral symptoms are primarily related to damage of the vermis [7, 17, 18, 19], but lobule VI of the right cerebellar hemisphere and lobule VI and Crus I of the left one are also involved in emotional processing [14, 15] - see Fig. 2 above to the right for a simplified version of cerebellar topography in the CCAS and PFS. For a 3D atlas of the human cerebellum and an in-depth analysis of cerebellar topography click here and here.
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