Posterior Fossa Tumors Treatment & Management
- Author: Hassan Ahmad Hassan Al-Shatoury, MD, PhD, MHPE; Chief Editor: Brian H Kopell, MD more...
No primary medical therapy exists for posterior fossa brain tumors. Medications, such as Lasix and corticosteroids, are administered before surgery to reduce the effect of edema on the surrounding structures.
Preoperative details include the following:
Assessment of the general condition of the patient
Preoperative clearance, including cardiovascular assessment, pulmonary assessment, renal assessment, metabolic assessment, and hematologic assessment
Management of the secondary effects of tumor and intracranial hypertension, such as headache, vomiting, and dehydration
Reservation of at least 3 units of fresh blood in case of intraoperative need
Managing symptomatic obstructive hydrocephalus before surgical removal of the tumor (2 schools of thought)
CSF shunting, either internal or external (may expose the patient to the additional inherent shunt risks as well as infection or other surgical complications)
Medical management - Decreasing the intracranial pressure by administering glucocorticoids, such as dexamethasone in a dose of 1 mg/kg/d
Neurological deterioration - Possible emergent operation for tumor removal
Intraoperative details include the following:
- Prone is comfortable for the surgeon. The head is fixed in 3-point head fixation if the patient is older than 2 years.
- The sitting position carries the risk of air embolism. It is less comfortable for the surgeon. The field is much clearer because drainage is easier. In children younger than 2 years, a Mayfield headrest is used. The head is flexed slightly, without compressing the neck vessels.
Safety burr hole
- A safety burr hole is placed in the occipital area. This could be used in case of acute hydrocephalus requiring ventricular drainage.
- In patients with hydrocephalus, the ventricle is cannulated through this burr hole. The catheter is tunneled subcutaneously and connected to an external ventricular drainage system for subsequent management.
Approaches: The most common approaches to the posterior fossa tumors are midline, paramedian, or retromastoid.
General operative principles
- Midline incision extends from the inion to the upper cervical vertebra.
- The paracervical and suboccipital muscles are separated by diathermy.
- Craniectomy is performed according to the site and size of the tumor.
- The foramen magnum is opened, and the C1 arch may be removed, especially in tumors extending to, or beyond, the craniocervical junction.
- The dura is opened in Y-shape, with the base upward.
- Bipolar and self-retaining retractors are used for cerebellar cortical incision to expose the tumor.
- Tumors are removed using gentle suction, ultrasonic surgical aspirator, or carbon dioxide laser. The last method is used only infrequently.
- The extent of tumor removal should be weighed with the possible risk of complication, especially with tumors adherent to the brainstem.
- The dura is closed in a watertight fashion. Dural grafting may be needed for complete closure.
- Using an Ommaya reservoir for perioperative external ventricular CSF drainage enabled tumors to be wholly and safely removed. Restoring CSF circulation provided an effective means of controlling and preventing hydrocephalus secondary to posterior fossa tumors in children.
- Choroid plexus papilloma should be removed totally because it is a benign tumor that does not invade the brain.
- If a dermoid cyst is associated with a sinus, the sinus should be removed completely.
Postoperative details include the following:
Early postoperative care
- Increased ataxia
- Increased lower cranial nerve dysfunction
- Apnea, or respiratory abnormalities
Late postoperative care
- Medulloblastoma: Adjuvant therapy should be administered in medulloblastoma. In this type of tumor, both the brain and spinal cord receive radiation therapy.
- Adjuvant chemotherapy is also administered in poor-risk patients with medulloblastoma in the form of cyclophosphamide-cisplatin-vincristine.
- Ependymomas: In cases with ependymomas, craniospinal irradiation should be considered because subarachnoid seeding sometimes is found, especially in the anaplastic type and those in the fourth ventricle. Recurrent cases may be administered adjuvant chemotherapy as bischloroethylnitrosourea (BCNU) and dibromodulcitol.
- Choroid plexus papilloma and carcinoma: Seeding of tumor cells in the subarachnoid space has been reported, although it is uncommon. Radiation therapy for this metastasis is still under research.
- Hemangioblastoma: Complete surgical resection should be the aim of surgery. However, in case of subtotal removal, radiation therapy may be useful to eradicate the residual tumor.
MRI is a helpful postoperative tool to detect early recurrence before it is manifested clinically. The interval of MRI scanning depends on the tumor histology and postoperative course. Patients receiving chemotherapy for a malignant lesion also should be studied between chemotherapy cycles to assess response. The presence of residual or recurrent contrast enhancement 2 months after surgery suggests recurrence. Postirradiation changes may mimic recurrence, requiring follow-up after few weeks.
Possible complications of posterior fossa tumor surgery include the following:
Lower cranial nerve dysfunction
Facial nerve palsy
Long tract deficits
Other postoperative complications
Shunt obstruction or malfunction
Deep venous thrombosis
Cerebrospinal fluid leak
Cerebellar mutism syndrome 
Outcome and Prognosis
The 5-year survival rates exceed 60% for all patients and 80% for certain good-risk individuals with posterior fossa tumors. In cases of pilocytic cerebellar astrocytoma, the 25-year survival rate exceeds 94%.
Patients with medulloblastoma are classified into good-risk and bad-risk categories based on the following:
Age of presentation
Extension of surgical resection
Leptomeningeal dissemination or metastasis
Prognosis in medulloblastoma is worse for children younger than 2 years, for patients with subtotal resection (80%), and for those with subarachnoid metastasis or positive results on CSF cytology more than 2 weeks after surgery. In patients with ependymomas, the 5-year survival rate is 20%; in ependymoblastoma, the 5-year survival rate is only 6%.
Choroid plexus papilloma has excellent prognosis, as high as 100% survival rate. Choroid plexus carcinoma has a poor prognosis.
Future and Controversies
Stereotactic radiosurgery utilizes only the physical properties of the irradiation to deliver deadly radiation doses to the tumor. Stereotactic radiotherapy benefits from the differences in radiobiological properties between normal and pathological tissue.
In interstitial brachytherapy, a radioactive material is implanted into the tumor bed at the time of surgery to deliver a continuous, localized dose of irradiation. Chemotherapy with new therapeutic medications may have a role in the treatment of residual tumors after surgery.
Immunotherapy aims at activation of cell-mediated cytotoxic responses and humorally mediated cytotoxic response against the tumor cells. This is still investigational.
An informed consent must be obtained from the patient if his or her general condition permits understanding the risks and potential benefits of surgery; otherwise, it must be obtained from relatives. The discussion related to the informed consent should include the following:
Summary of the nature of the condition and its presumed course without treatment
Description of the proposed surgical treatment
Possible complications that can occur as a result of surgery
Review of alternative treatment modalities, including a brief discussion of the pros and cons of each treatment
A statement that the operation is not guaranteed to improve the patient's condition
Cushing H. Experience with the cerebellar medulloblastoma: critical review. Acta Pathol Microbiol Immunol Scand. 1930. 7:1-86.
Johnson KJ, Cullen J, Barnholtz-Sloan JS, Ostrom QT, Langer CE, Turner MC, et al. Childhood brain tumor epidemiology: a brain tumor epidemiology consortium review. Cancer Epidemiol Biomarkers Prev. 2014 Dec. 23 (12):2716-36. [Medline].
Lin CT, Riva-Cambrin JK. Management of posterior fossa tumors and hydrocephalus in children: a review. Childs Nerv Syst. 2015 Oct. 31 (10):1781-9. [Medline].
Lam S, Reddy GD, Lin Y, Jea A. Management of hydrocephalus in children with posterior fossa tumors. Surg Neurol Int. 2015. 6 (Suppl 11):S346-8. [Medline].
Badhe PB, Chauhan PP, Mehta NK. Brainstem gliomas--a clinicopathological study of 45 cases with p53 immunohistochemistry. Indian J Cancer. 2004 Oct-Dec. 41(4):170-4. [Medline].
Wind JJ, Bakhtian KD, Sweet JA, Mehta GU, Thawani JP, Asthagiri AR, et al. Long-term outcome after resection of brainstem hemangioblastomas in von Hippel-Lindau disease. J Neurosurg. 2011 May. 114(5):1312-8. [Medline].
Arriada N, Sotelo J. Continuous-flow shunt for treatment of hydrocephalus due to lesions of the posterior fossa. J Neurosurg. 2004 Nov. 101(5):762-6. [Medline].
Millard NE, De Braganca KC. Medulloblastoma. J Child Neurol. 2015 Sep 2. [Medline].
Jiang C, Wu X, Lin Z, Wang C, Kang D. External drainage with an Ommaya reservoir for perioperative hydrocephalus in children with posterior fossa tumors. Childs Nerv Syst. 2013 Mar 17. [Medline].
Abe M, Tokumaru S, Tabuchi K, Kida Y, Takagi M, Imamura J. Stereotactic radiation therapy with chemotherapy in the management of recurrent medulloblastomas. Pediatr Neurosurg. 2006. 42(2):81-8. [Medline].
Levin VA, Edwards MS, Gutin PH, et al. Phase II evaluation of dibromodulcitol in the treatment of recurrent medulloblastoma, ependymoma, and malignant astrocytoma. J Neurosurg. 1984 Dec. 61(6):1063-8. [Medline].
Wells EM, Khademian ZP, Walsh KS, Vezina G, Sposto R, Keating RF, et al. Postoperative cerebellar mutism syndrome following treatment of medulloblastoma: neuroradiographic features and origin. J Neurosurg Pediatr. 2010 Apr. 5(4):329-34. [Medline].
Gjerris F, Klinken L. Long-term prognosis in children with benign cerebellar astrocytoma. J Neurosurg. 1978 Aug. 49(2):179-84. [Medline].
Akay KM, Izci Y, Baysefer A, et al. Surgical outcomes of cerebellar tumors in children. Pediatr Neurosurg. 2004 Sep-Oct. 40(5):220-5. [Medline].
DeAngelis LM. Chemotherapy for brain tumors--a new beginning. N Engl J Med. 2005 Mar 10. 352(10):1036-8. [Medline].
Edwards M, Hudgins R. Medulloblastomas and primitive neuroectodermal tumors of the posterior fossa. In: Mclaurin R, Schut L, Venes J, et al, eds. Pediatric Neurosurgery: Surgery of the developing nervous system. Philadelphia, Pa:. WB Saunders Co. 1989:347-356.
Gottardo NG, Gajjar A. Current Therapy for Medulloblastoma. Curr Treat Options Neurol. 2006 Jul. 8(4):319-334. [Medline].
Hawkins JC 3d. Treatment of choroid plexus papillomas in children: a brief analysis of twenty years'' experience. Neurosurgery. 1980 Apr. 6(4):380-4. [Medline].
Hendrick E, Raffel C. Tumors of the fourth ventricle: ependymomas, choroid plexus papillomas, and dermoid cysts. In: McLaurin R, Schut L, Venes J, et al, eds. Pediatric neurosurgery: Surgery of the developing nervous system. Philadelphia, Pa:. WB Saunders Co. 1989:366-372.
Hoffman HJ, Becker L, Craven MA. A clinically and pathologically distinct group of benign brain stem gliomas. Neurosurgery. 1980 Sep. 7(3):243-8. [Medline].
Jones B. Posterior fossa treatment. Br J Radiol. 2005 Mar. 78(927):285; author reply 285. [Medline].
May PL, Blaser SI, Hoffman HJ, et al. Benign intrinsic tectal "tumors" in children. J Neurosurg. 1991 Jun. 74(6):867-71. [Medline].
Morawski KF, Niemczyk K, Bohorquez J, Marchel A, Delgado RE, Ozdamar O. Intraoperative monitoring of hearing during cerebellopontine angle tumor surgery using transtympanic electrocochleography. Otol Neurotol. 2007 Jun. 28(4):541-5. [Medline].
Padovani L, Sunyach MP, Perol D, Mercier C, Alapetite C, Haie-Meder C. Common strategy for adult and pediatric medulloblastoma: a multicenter series of 253 adults. Int J Radiat Oncol Biol Phys. 2007 Jun 1. 68(2):433-40. [Medline].
Park TS, Hoffman HJ, Hendrick EB, et al. Medulloblastoma: clinical presentation and management. Experience at the hospital for sick children, toronto, 1950-1980. J Neurosurg. 1983 Apr. 58(4):543-52. [Medline].
Pierre-Kahn A, Hirsch JF, Roux FX, et al. Intracranial ependymomas in childhood. Survival and functional results of 47 cases. Childs Brain. 1983. 10(3):145-56. [Medline].
Raffel C. Medulloblastoma: molecular genetics and animal models. Neoplasia. 2004 Jul-Aug. 6(4):310-22. [Medline].
Rath GP, Bithal PK, Chaturvedi A, Dash HH. Complications related to positioning in posterior fossa craniectomy. J Clin Neurosci. 2007 Jun. 14(6):520-5. [Medline].
Rogers L, Pueschel J, Spetzler R, et al. Is gross-total resection sufficient treatment for posterior fossa ependymomas?. J Neurosurg. 2005 Apr. 102(4):629-36. [Medline].
Rorke L, Schut L. Introductory survey of pediatric brain tumors. In: McLaurin R, Schut L, Venes J, et al, eds. Pediatric Neurosurgery: Surgery of the developing nervous system. Philadelphia, Pa:. WB Saunders Co. 1989:335-337.
Rorke LB. The cerebellar medulloblastoma and its relationship to primitive neuroectodermal tumors. J Neuropathol Exp Neurol. 1983 Jan. 42(1):1-15. [Medline].
Schijman E, Peter JC, Rekate HL, et al. Management of hydrocephalus in posterior fossa tumors: how, what, when?. Childs Nerv Syst. 2004 Mar. 20(3):192-4. [Medline].
Schumacher M, Schulte-Mönting J, Stoeter P, Warmuth-Metz M, Solymosi L. Magnetic resonance imaging compared with biopsy in the diagnosis of brainstem diseases of childhood: a multicenter review. J Neurosurg. 2007 Feb. 106(2 Suppl):111-9. [Medline].
Smith RR, Zimmerman RA, Packer RJ, et al. Pediatric brainstem glioma. Post-radiation clinical and MR follow-up. Neuroradiology. 1990. 32(4):265-71. [Medline].
Sutton L, Schut L. Cerebellar astrocytomas. In: McLaurin R, Schut L, Venes J, et al, eds. Pediatric Neurosurgery: Surgery of the developing nervous system. Philadelphia, Pa:. WB Saunders Co. 1989:338-346.
Wilne S, Collier J, Kennedy C, Koller K, Grundy R, Walker D. Presentation of childhood CNS tumours: a systematic review and meta-analysis. Lancet Oncol. 2007 Aug. 8(8):685-95. [Medline].
Zabek M. Primary posterior fossa tumours in adult patients. Folia Neuropathol. 2003. 41(4):231-6. [Medline].
Zhou LF, Du G, Mao Y, Zhang R. Diagnosis and surgical treatment of brainstem hemangioblastomas. Surg Neurol. 2005 Apr. 63(4):307-15; discussion 315-6. [Medline].