Posterior fossa syndrome-a narrative review

Abstract

Posterior fossa syndrome (PFS), or cerebellar mutism syndrome (CMS), is a collection of neurological symptoms that occur following surgical resection of a posterior fossa tumour, and is characterised by either a reduction or an absence of speech. Some authors suggest that CM is only one symptom of the CMS complex that also includes ataxia, hypotonia and irritability as well as cranial nerve deficits, neurobehavioral changes and urinary retention or incontinence. It is seen almost exclusively in children. In 1985 Rekate et al. published the first work describing CM as a clinical entity, occurring as a consequence of bilateral cerebellar injury. Other associated symptoms include visual impairment, altered mood, impaired swallowing and significant gross and fine motor deficits. The effects of this can have a devastating impact on both the patient and their carers, posing a significant clinical challenge to neurorehabilitation services. The reported incidence was between 8% and 31% of children undergoing surgery for posterior fossa tumour. The underlying pathologies include vasospasm, oedema, and axonal/neuronal injury. Neuroimaging has contributed to a better understanding of the anatomical location of postoperative injury. There have been a number of suggestions for treatment interventions for PFS. However, apart from some individual reports, there have been no clinical trials indicating possible benefit. Occupational therapy, speech and language therapy, as well as neurocognitive support, contribute to the recovery of these patients.

Keywords: Posterior fossa syndrome (PFS); cerebellar mutism syndrome (CMS); neuroimaging; posterior fossa tumour.

Figure 1

Denate nucleus injury and PFS. (A) T2-weighted pre-operative MRI scan shows a large midline posterior fossa tumour, consistent with a medulloblastoma (arrow). Post-operative FLAIR imaging in (B), taken six months after resection of the tumour, demonstrates hyperintensity in the region of the right dentate nucleus (arrow). This is consistent with injury in this region. Clinically, the child has PFS. PFS, posterior fossa syndrome; MRI, magnetic resonance imaging; FLAIR, fluid attenuation inversion recovery.

Figure 2

Unilateral and bilateral superior cerebellar peduncle injury in PFS. (A,B) Pre- and post-operative T2-weighted MRI scans show a midline fourth ventricular tumour extending under the left superior cerebellar peduncle; after resection this structure is attenuated (arrows); (C,D) in these images, also T2-weighted MRI scans, the tumour compresses both superior cerebellar peduncles (C). In the post-operative image (D), both superior cerebellar peduncles are attenuated (arrows). Both children had PFS. These imaging data illustrate the association between loss of integrity of the superior cerebellar peduncle and PFS. PFS, posterior fossa syndrome; MRI, magnetic resonance imaging.

Figure 3

Hypertrophic olivary degeneration in PFS. (A) Pre-operative T2-weighted MRI scan demonstrates a large fourth ventricular medulloblastoma (arrow). Post-operatively, this child developed PFS. Although not evident in the early post-operative MRI scan in (B) (arrow), the scan in (C), performed one year after surgery, shows hypertrophic degeneration of the inferior olivary nucleus (arrow). PFS, posterior fossa syndrome; MRI, magnetic resonance imaging.