1-A 45-year-old right-handed man who has been HIV positive for the past 3 years has noticed some sort of visual change over the past 1 to 2 months. It is difficult for him to describe, but it is some sort of distortion of part of his right visual field. There is a 4-cm rim-enhancing lesion in the left occipital lobe that is revealed by MRI.

Which of the following tumor types is common in the brain of patients with AIDS, but otherwise extremely rare?

Lymphocytic leukemia
Metastatic lymphoma
Primary lymphoma
Kaposi’s sarcoma
Lymphosarcoma

ansawer: Primary lymphoma

explanation : Kaposi’s sarcoma is unusually common in patients with AIDS, but it is rarely metastatic to the brain. Metastatic lymphomas producing meningeal lymphomatosis are not especially rare in the general population, but primary lymphomas (i.e., lymphomas apparently arising in the CNS) were rare before the AIDS epidemic. The primary brain lymphoma usually presents as a solitary mass and can occur anywhere in the brain, but it does have a predilection for the periventricular structures.

2-A 9-year-old girl presents with precocious puberty and episodes of uncontrollable laughter.

Which of the following mass lesions might explain her symptoms?

Craniopharyngioma
Choroid plexus papilloma
Giant aneurysm
Metastatic carcinoma
Hypothalamic hamartoma

answer: Hypothalamic hamartoma

explanation : Hypothalamic hamartomas are nonneoplastic malformations involving neurons and glia in the region of the hypothalamus. They may be discovered incidentally, either on imaging performed for other reasons or at autopsy, or they may cause symptoms referable to the hypothalamus. Most often, the latter involves neuroendocrine functions, causing precocious puberty or acromegaly due to overproduction of growth hormone-releasing hormone. Patients may also experience paroxysms of laughter, known as gelastic seizures. They may be cured surgically. Craniopharyngiomas are epithelial neoplasms arising in the sellar and third ventricular regions. They may cause hypopituitarism and visual field disturbances. Choroid plexus papillomas usually develop intraventricularly and do not extend down into the sella turcica. These tumors affect both children and adults, but they are rare. They are benign if they are surgically accessible and are extirpated early in their evolution. Giant aneurysms occur in many locations, but typically do not cause gelastic seizures or precocious puberty. Metastatic carcinoma generally occurs in older patients and would not be expected to cause these symptoms.

3-With an ependymoma of the posterior fossa, the patient is at risk of dying because of which of the following?

Transforaminal herniation
Emboli from the tumor
Vascular occlusion by the tumor
Hemorrhagic necrosis of the tumor
Status epilepticus

answer: Transforaminal herniation

explanation : As a tumor of the posterior fossa enlarges, the contents of the posterior fossa will be compressed and ultimately forced upward or downward. If the herniation is upward, it is called transtentorial because it is across the tentorium cerebelli. If it is downward, it is called transforaminal because it is across the foramen magnum. Ependymomas are not especially vulnerable to hemorrhagic necrosis. Tumors in the posterior fossa generally do not produce seizures.

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