Fossa Tumors Medulloblastoma
is the most frequent infratentorial tumor in neonates. Medulloblastomas
are usually midline and arise from primitive neurons in the posterior
medullary velum. They may compress and infiltrate the brainstem. They
present with signs of brainstem dysfunction and increased intracranial
pressure. Apnea may be the first sign of medulloblastoma. Posterior fossa arachnoid
cysts can produce apnea by brainstem compression (Figure 26.1). Apnea
is more likely to occur with ventrally located cysts. The treatment for
posterior fossa arachnoid cysts producing apnea is surgical decompression.
Figure 26.1.— [A]
Ventrally located posterior fossa arachnoid cyst compressing the brainstem.
[B] Decompressed posterior fossa arachnoid cyst. The apnea in this patient
ceased after treatment.