Indications and Preoperative Considerations

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  Posterior fossa meningiomas are uncommon lesions that can be found virtually anywhere in the infratentorial space. The management of these lesions will depend on their size, location, growth rate and clinical presentation.

  
  
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  These tumors can be classified according to their location as suboccipital, petrosal or tentorial cerebellar surfaces, cerebellopontine angle (CPA), fourth ventricle or petroclival meningiomas ( Table 12.1 ). Each location is related to different signs and symptoms, treatment options and surgical approaches.

  
  
  
  

  Table 12.1

  
  

  Classification of posterior fossa meningiomas and approach according to the location of the tumor

  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Location	Incidence	Symptoms	Common surgical approaches
  Occipital surface	10%	Headaches, cerebellar syndrome, increased intracranial pressure, hemianopsia, visual hallucinations	Suboccipital craniotomy ± occipital craniotomy
  Lateral petrous surface	8–10%	V, VII and VIII cranial neuropathies; brainstem and cerebellar compression syndromes	Retrosigmoid craniotomy
  CPA	10–15%	V, VII and VIII cranial neuropathies; brainstem and cerebellar compression syndromes	Pterional craniotomy variants ± anterior petrosectomy
  Petroclival region	10–38%	III, IV, V, VI, VII, VIII, IX, X and XI cranial neuropathies; brainstem and cerebellar compression syndromes; spasticity; headaches	Pterosal craniotomy variants ± anterior petrosectomy
  Jugular foramen	Rare	IX, X and XI cranial neuropathies; brainstem and cerebellar compression syndromes	Retrosigmoid craniotomy, transjugular variants
  Foramen magnum	4–20%	Increased intracranial pressure; IX, X, XI and XII cranial neuropathies; brainstem and spinal cord compression syndromes	Suboccipital craniotomy ± C1 laminectomy, transoral; far lateral approach
  Pineal region	6–8%	Increased intracranial pressure; visual symptoms; cerebellar dysfunction	Infratentorial supracerebellar craniotomy, occipital transtentorial craniotomy, supra/infratentorial trans-sinus approach
  Fourth ventricle	Rare	Headaches, increased intracranial pressure	Midline suboccipital craniotomy
  Tentorial surface	30%	III, V, VI, VII and VIII cranial neuropathies; headaches; increased intracranial pressure; brainstem and cerebellar compression syndromes; psychomotor epilepsy	Subtemporal craniotomy, petrosal craniotomy variants, retrosigmoid craniotomy

   
  

  Reproduced with permission from Amin, B.Y., Ryu, S., Rock, J.P., 2012. Surgical management of posterior fossa meningiomas. In Quiñones-Hinojosa, A. (Ed.), Schmidek & Sweet: Operative Neurosurgical Techniques: Indications, Methods and Results, sixth ed. Saunders, Elsevier Inc., Philadelphia, vol. 1, pp. 501–516.
  
  
  
  
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  The patients may present with sign and symptoms secondary to compression of cranial nerves and long tracts, hydrocephalus and/or intracranial hypertension. The diagnosis is based on MRI and CT studies, which demonstrate an intense enhanced lesion after contrast administration and its relation with the surrounding posterior fossa contents.

  
  
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  CT angiography, magnetic resonance angio-venography (MRA/MRV) and conventional angiography are useful for preoperative vascular evaluation. The latter, although less used nowadays, is required for preoperative embolization, which can be helpful in cases where early control of the tumor’s blood supply is difficult during surgery.

  
  
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  Different treatment options, including observation, radiosurgery and surgical resection, are available for meningiomas. Radiotherapy is useful as an adjuvant treatment for patients with atypical or malignant meningiomas and in subtotally or unresectable cases with evidence of growth. Radiosurgery is typically reserved for lesions less than 3 cm in diameter.

  
  
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  Surgery for posterior fossa meningiomas is considered in cases of symptomatic patients, as well as initially asymptomatic patients who have enlarging lesions and/or who develop symptoms related to their tumor.

  
  
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  In cases that present with ventricular obstruction, a temporary ventriculostomy or third ventriculostomy may be performed prior to the tumor resection.

  
  
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  Neurophysiology monitoring of long tracts and cranial nerves is typically recommended in order to minimize iatrogenic injury.