Review Question - QID 212377

This patient with recurrent headaches, signs of increased intracranial pressure, and cerebellar dysfunction has an MRI demonstrating a cerebellar mass. The most likely diagnosis is medulloblastoma.

Medulloblastomas are the most common malignant primary brain tumors in children. Medulloblastomas occur almost exclusively in the cerebellum, which can result in compression of the fourth ventricle. This results in increased intracranial pressure which often manifests with headache, nausea, and vomiting that is worse immediately after waking. Exam findings vary depending on the location of the tumor. Midline lesions present with truncal ataxia. A nodding head tremor, also known as head titubation, is another indication of a midline cerebellar lesion. Lateral cerebellar lesions, which are more common in adults than children, lead to an appendicular ataxia, such as impaired finger-to-nose testing and intention tremor. Medulloblastoma can often result in metastatic lesions in the spinal cord, sometimes referred to as "drop metastases." For most patients with medulloblastoma, management includes a combination of surgical resection, chemotherapy, and radiation.

Bartlett et. al review the diagnosis and management of medulloblastoma in children. They discuss the typical exam findings related to cerebellar dysfunction including head titubation and ataxia, as well as those of increased intracranial pressure such as papilledema. They note the role of MR imaging in the diagnosis of this disease.

Figure A demonstrates a T1 MRI image showing a cerebellar mass with associated hydrocephalus.

Figure B demonstrates a contrast-enhanced T2 MRI image showing a heterogeneously enhanced midline lesion suggestive of a medulloblastoma.

Incorrect Answers:
Answer 1: Craniopharyngiomas develop from embryologic remnants of the Rathke pouch, which develops along the nasopharynx to the diencephalon. This tumor can compress the optic chiasm, resulting in a bitemporal hemianopsia. These tumors do not occur in the cerebellum.

Answer 2: Ependymomas are typically found within the fourth ventricle, which may result in similar symptoms related to increased intracranial pressure. However, they do not occur in the cerebellum. Thus, symptoms related to cerebellar dysfunction would not be expected.

Answer 4: Pilocytic astrocytomas are the most common primary brain tumor in children. On MR imaging, these tumors often contain a cystic component, which is not present in this patient's MRI.

Answer 5: Pinealomas are tumors of the pineal gland, which can result in Parinaud syndrome (vertical gaze palsy, not seen in this patient). There is an increase in beta-hCG production that results in precocious puberty in boys.

Bullet Summary:
Medulloblastomas typically present in children with truncal ataxia and a cerebellar midline mass that results in a non-obstructive hydrocephalus due to compression of the 4th ventricle.