ANATOMY

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 [11], 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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Definitions, Incidence, Symptoms, Pathophysiology, Imaging findings, Risk factors, Prognosis, Treatment, Prevention

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10. Soelva V, Hernaiz DP, Abbushi A, Rueckriegel S, Bruhn H, Eisner W, Thomale UW (2013) Fronto-cerebellar fiber tractography in pediatric patients following posterior fossa tumor surgery. Childs Nerv Syst 29: 597-607

11. Crutchfield JS, Sawaya R, Meyers CA, & Moore BD, III (1994). Postoperative mutism in neurosurgery. Report of two cases. J Neurosurg 81: 115-121.

12. Morris EB, Phillips NS, Laningham FH, Patay Z, Gajjar A, Wallace D, Boop F, Sanford R, Ness KK, Ogg RJ (2009) Proximal dentatothalamocortical tract involvement in posterior fossa syndrome. Brain 132: 3087-3095

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17. Aarsen FK, van Dongen HR, Paquier PF, van MM, Catsman-Berrevoets CE (2004). Long-term sequelae in children after cerebellar astrocytoma surgery. Neurology 62: 1311-1316

18. Al-Afif S, Staden M, Krauss JK, Schwabe K, Hermann EJ (2013). Splitting of the cerebellar vermis in juvenile rats--effects on social behavior, vocalization and motor activity. Behav Brain Res 250: 293-298

19. Schmahmann JD (1991). An emerging concept. The cerebellar contribution to higher function. Arch Neurol 48: 1178-1187

20. Avula S, Kumar R, Pizer B, Pettorini B, Abernethy L, Garlick D, Mallucci C (2015) Diffusion abnormalities on intraoperative magnetic resonance imaging as an early predictor for the risk of posterior fossa syndrome. Neuro-Oncology 17(4): 614-22

21. Ojemann JF, Partridge SC, Poliakov AV, Niazi TN, Shaw DW, Ishak GE, Lee A, Browd SR, Geyer JR, Ellenbogen RG (2013) Diffusion tensor imaging of the superior cerebellar peduncle identifies patients with posterior fossa syndrome. Child Nerv Syst 29: 2071-2077