Infratentorial Tumors

Highest incidence: Age 3–12 y and 55–65 y

Two-thirds of childhood CNS tumors; approximately 3–5:100,000/y under age 19 y

15–20% of adult CNS tumors; incidence lower than in children

Very confined space, brain tolerates tumor poorly, leading to symptoms and less forgiving with surgery than supratentorial

CSF obstruction with hydrocephalus common; ICP tolerated poorly

Increasing ICP and hydrocephalus

Impaired protective airway reflexes and aspiration

Irregular ventilation due to brainstem compression and swelling

Impaired level of consciousness

Cranial nerves abnormalities

Survival 60% in children.

Prognosis is poor with glioblastoma, and infiltrating brainstem glioma.

Benign lesions, such as meningioma and acoustic neuroma, have low morbidity and mortality but may recur if resection is incomplete.

Degree of head elevation influences venous pressure and incidence and severity of air embolism (sitting (worst) > prone > park bench/lateral position).

Primary intraaxial lesions are generally malignant; extraaxial lesions are typically benign.

Children: Astrocytoma, medulloblastoma, and brainstem glioma are the most common in children ages 3–12 y.

Less than 1 y old, most common are astrocytoma, cerebellar PNET medulloblastoma ependymoma, brainstem glioma.

Less than 2 y old, most common are are medulloblastoma and low-grade glioma (70%).

Pediatric cystic cerebellar astrocytoma is associated with 80% survival at 20 y.

Adult: Most primary tumors are acoustic neuroma associated with NF-II and meningioma. (most >60 y are acoustic).

Metastases: Lung and breast most common; vasogenic so ICP common. Metastases to cerebellum forms mass lesion.

Differentiate from AVM and aneurysms.