The posterior fossa is a small space in the skull, found near the brainstem and cerebellum. The cerebellum is the part of the brain responsible for balance and coordinated movements. The brainstem is responsible for controlling vital body functions, such as breathing.

If a tumor grows in the area of the posterior fossa, it can block the flow of spinal fluid and cause increased pressure on the brain and spinal cord.

Most tumors of the posterior fossa are primary brain cancers. They start in the brain, rather than spreading from somewhere else in the body.

Posterior fossa tumors have no known causes or risk factors.

Symptoms occur very early with posterior fossa tumors and may include:

• Drowsiness
• Headache
• Imbalance
• Nausea
• Uncoordinated walk (ataxia)
• Vomiting

Symptoms from posterior fossa tumors also occur when the tumor damages local structures, such as the cranial nerves. Symptoms of cranial nerve damage include:

• Dilated pupils
• Eye problems
• Face muscle weakness
• Hearing loss
• Loss of feeling in part of the face
• Taste problems
• Unsteadiness when walking
• Vision problems

The diagnosis is based on a thorough medical history and physical exam, followed by imaging tests and a biopsy. The best way to look at the posterior fossa is with an MRI scan. CT scans are not helpful to see that area of the brain in most cases.

The following procedures may be used to remove a piece of tissue from the tumor to help with diagnosis:

• Open brain surgery, called a posterior craniotomy
• Stereotactic biopsy

Most tumors of the posterior fossa are removed with surgery, even if they are not cancerous. There is limited space in the posterior fossa, and the tumor can easily press on critical structures if it grows.

Depending on the type and size of the tumor, radiation treatment may also be used after surgery.

You can ease the stress of illness by joining a support group whose members share common experiences and problems.

A good outlook depends on finding the cancer early. A total blockage in the flow of spinal fluid can be life threatening. If tumors are found early, surgery can lead to long-term survival.

Complications may include:

• Cranial nerve palsies
• Brain herniation
• Hydrocephalus
• Increased intracranial pressure

Contact your health care provider if you have regular headaches that occur with nausea, vomiting, or vision changes.

Infratentorial brain tumors; Brainstem glioma; Cerebellar tumor

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Dorsey JF, Salinas RD, Dang M, et al. Cancer of the central nervous system. In: Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff's Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:chap 63.

Friehling ED, Meade JC, Bleyer A, Ritchey KA. Principles of cancer treatment. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 543.

Updated by: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.