title: Tonsillar herniation and cervical syringomyelia in association with posterior fossa tumors in children: a case-based update.
abstract: BACKGROUND
  Posterior fossa tumors most commonly occur in children. They frequently present with raised intracranial pressure and may have tonsillar herniation. The symptomatology is predominantly directed towards the tumor. The occurrence of syringomyelia in such cases is most unusual. Symptomatic syringomyelia is rare.
  
  
  METHODS
  We describe a case of a pilocytic astrocytoma of the cerebellum in a 13-year-old girl who presented with clinical features of progressively worsening raised intracranial pressure and secondary tonsillar herniation and cervical syringomyelia. Magnetic resonance (MR) imaging showed a large midline inhomogenously enhancing vermian tumor causing moderate obstructive hydrocephalus. In addition, the cerebellar tonsils herniated down to the C2 level, and there was a centrally located syrinx from C2-T1. The tumor was resected through a suboccipital craniectomy. At follow-up after 3 months, MR imaging demonstrated total resolution of tonsillar herniation and cervical syringomyelia.
  
  
  CONCLUSIONS
  The occurrence of tonsillar herniation and syringomyelia in association with a slow growing benign tumor like pilocytic astrocytoma of the cerebellum is uncommon. The blockade of normal cerebrospinal fluid circulation pathway at the foramen magnum is the crucial factor. Surgical extirpation of the tumor restores the normal cerebrospinal fluid circulation at the foramen magnum and produces an excellent outcome. The need for an additional surgical procedure for treatment of associated tonsillar herniation and syringomyelia can be avoided. Volumetric assessment of the posterior fossa may provide a better understanding of the pathophysiology of syringomyelia in such patients.
authors.affiliation: Division of Neurosurgery, Children's Hospital of Eastern Ontario, 401 Smyth Road, Ottawa, K1H 8 L1, Ontario, Canada.
authors.forename: Dattatraya
authors.initials: D
authors.lastname: Muzumdar
authors.forename: Enrique C G
authors.initials: EC
authors.lastname: Ventureyra
mesh_terms: D000293:Adolescent; D001254:Astrocytoma; D018450:Disease Progression; D005260:Female; D006547:Hernia / Q000209:etiology*; D006801:Humans; D015192:Infratentorial Neoplasms / Q000150:complications*; D008279:Magnetic Resonance Imaging; D014066:Palatine Tonsil / Q000473:pathology*; D013595:Syringomyelia / Q000209:etiology*