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Posterior Fossa Tumors Treatment & Management

  • Author: Hassan Ahmad Hassan Al-Shatoury, MD, PhD, MHPE; Chief Editor: Brian H Kopell, MD  more...
 
Updated: Oct 24, 2015
 

Medical Therapy

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.

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Preoperative Details

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
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Intraoperative Details

Intraoperative details include the following:

  • Operative position
    • 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.[9]
  • Special concerns
    • 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.
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Postoperative Details

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.[10]
    • 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.[11]
    • 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.
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Follow-up

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.

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Complications

Possible complications of posterior fossa tumor surgery include the following:

  • Lower cranial nerve dysfunction
  • Facial nerve palsy
  • Deafness
  • Long tract deficits
  • Hemiplegia
  • Hemiparesis
  • Sensory abnormalities
  • Other postoperative complications
  • Infection
  • Prolonged coma
  • Shunt obstruction or malfunction
  • Chest infection
  • Deep venous thrombosis
  • Pulmonary embolism
  • Cerebrospinal fluid leak
  • Cerebellar mutism syndrome [12]
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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%.[13]

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.

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Future and Controversies

Future management

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.

Special issues

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
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Contributor Information and Disclosures
Author

Hassan Ahmad Hassan Al-Shatoury, MD, PhD, MHPE Associate Professor, Department of Neurosurgery, Suez Canal University; Co-Director, Center of Research and Development in Medical Education and Health Services Suez Canal University Hospital

Disclosure: Nothing to disclose.

Coauthor(s)

Herbert H Engelhard, III, MD, PhD, FACS Director, UIC Neuro-Oncology Program, Chief, Division of Neuro-Oncology, Associate Professor, Department of Neurosurgery, University of Illinois at Chicago College of Medicine

Herbert H Engelhard, III, MD, PhD, FACS is a member of the following medical societies: American Association for Cancer Research, Society for Neuroscience, Society for Neuro-Oncology, American Society for Cell Biology, Congress of Neurological Surgeons, Chicago Medical Society, American Association of Neurological Surgeons, American College of Surgeons, American Medical Association, Illinois State Medical Society

Disclosure: Nothing to disclose.

Ayman Ali Galhom, MD, PhD Lecturer (Associated Professor), Department of Neurosurgery, Suez Canal University Faculty of Medicine, Egypt

Ayman Ali Galhom, MD, PhD is a member of the following medical societies: Congress of Neurological Surgeons

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Brian H Kopell, MD Associate Professor, Department of Neurosurgery, Icahn School of Medicine at Mount Sinai

Brian H Kopell, MD is a member of the following medical societies: Alpha Omega Alpha, American Association of Neurological Surgeons, International Parkinson and Movement Disorder Society, Congress of Neurological Surgeons, American Society for Stereotactic and Functional Neurosurgery, North American Neuromodulation Society

Disclosure: Received consulting fee from Medtronic for consulting; Received consulting fee from St Jude Neuromodulation for consulting; Received consulting fee from MRI Interventions for consulting.

Additional Contributors

Michael G Nosko, MD, PhD Associate Professor of Surgery, Chief, Division of Neurosurgery, Medical Director, Neuroscience Unit, Medical Director, Neurosurgical Intensive Care Unit, Director, Neurovascular Surgery, Rutgers Robert Wood Johnson Medical School

Michael G Nosko, MD, PhD is a member of the following medical societies: Academy of Medicine of New Jersey, Congress of Neurological Surgeons, Canadian Neurological Sciences Federation, Alpha Omega Alpha, American Association of Neurological Surgeons, American College of Surgeons, American Heart Association, American Medical Association, New York Academy of Sciences, Society of Critical Care Medicine

Disclosure: Nothing to disclose.

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Posterior fossa anatomy.
 
 
 
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