Posterior fossa tumor is a type of brain tumor located in or near the bottom of the skull.

Causes

The posterior fossa is a small space in the skull, found near the brain stem and cerebellum. The cerebellum is the part of the brain responsible for movement, balance, and coordination.

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, which start in the brain, rather than spreading from elsewhere in the body.

There are no known cause or risk factors associated with a posterior fossa tumor.

Symptoms

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

• Ataxia (uncoordinated gait)
• Drowsiness
• Headache
• Imbalance
• Nausea
• Vomiting

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

• Dilated pupils
• Eye deviations
• Facial muscle weakness
• Hearing loss
• Loss of sensation of part of the face
• Taste disturbances
• Unsteadiness when walking
• Visual field deficits

Exams and Tests

Diagnosis is based on thorough history and physical examination, followed by imaging tests. The best way to look at the posterior fossa is with an MRI scan. CT scans are usually not helpful.

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

Treatment

Most tumors of the posterior fossa are surgically removed, even if they are noncancerous. There is limited space in the brain area, and the tumor can press on delicate structures if it grows.

Occasionally, depending on the type of tumor and the size of it, postoperative radiation treatment is also used.

Support Groups

The stress of illness may be eased by joining a support group whose members share common experiences and problems.

Outlook (Prognosis)

Prognosis depends on early detection. Complete obstruction to the flow of spinal fluid causes herniation and death. If tumors are recognized before this point, surgery is associated with good, long-term survival.

Possible Complications

• Cranial nerve palsies
• Herniation
• Hydrocephalus
• Increased intracranial pressure

When to Contact a Medical Professional

Call your health care provider if you notice consistent headaches that are accompanied by nausea, vomiting, or visual changes.

Alternative Names

Infratentorial brain tumors; Brainstem glioma