171. The answer is a. (Ropper, pp 622-628.) Between 2% and 5% of all tumors occurring in the general population are primary CNS tumors. In adults, the most common primary brain tumor is the astrocytoma. In children, brain tumors are more likely to arise in the posterior fossa. Even in childhood, glial cell tumors, such as the cerebellar astrocytoma and the optic glioma, are common.
172. The answer is b. (Ropper, pp 622-628.) The most common primary brain tumors are malignant astrocytomas. These are classified as grade 3 or 4. Grade 4 astrocytoma is more commonly called glioblastoma multiforme. It is malignant in the very conventional sense that it invades adjacent tissue. This type of glial tumor is usually seen in adults; men are more susceptible than women.
173. The answer is e. (Swaiman, p 1687.) The posterior fossa is the usual location for brain tumors in children. Medulloblastomas, ependymomas, and cerebellar (or brainstem) gliomas account for most of the tumors that occur before puberty. Other common tumors developing intracranially in children include optic gliomas and metastatic leukemias.
174. The answer is b. (Swaiman, p 1687.) Meningiomas may occur in childhood, but are more likely to appear and become symptomatic during adult life. Neurofibromas are not primary brain tumors, although schwannoma of the eighth cranial nerve (CN) is sometimes incorrectly referred to as an acoustic neurofibroma rather than an acoustic schwannoma. Colloid cysts of the third ventricle are not necessarily neoplastic, although most are assumed to have started as neoplasms rather than as developmental anomalies. Glioma is a broad category that includes the astrocytoma. Adenomas, such as pituitary adenomas, do develop in children, but much less commonly than either astrocytomas or medulloblastomas. CNS tumors account for a large proportion of the tumors seen in childhood. In fact, they are second in frequency only to childhood leukemias and account for 15% to 20% of childhood tumors.
175. The answer is a. (Ropper, pp 628-630.) Hyperostosis is thickening of the bone and is much less commonly induced by tumors in or about the brain than is thinning of the bone. Thinning occurs especially with pituitary adenomas, which may cause erosions in the floor of the sella turcica as an early feature. Calcifications may develop in schwannomas or astrocytomas, but both of these tumor types will usually cause bony erosions where they impinge on the skull. Calcifications may develop in many primary or metastatic brain tumors, but calcification sufficient to be readily seen on a skull x-ray suggests an astrocytoma, meningioma, oligodendroglioma, or metastatic tumor. Calcification can be visualized on CT scan in about 17% of medulloblastomas. With meningiomas, hyperostosis may develop in the bone adjacent to the tumor even if there is no infiltration of the bone by the tumor.
176. The answer is a. (Ropper, p 641.) The pineal region is the source of an extraordinarily diverse group of tumor types, ranging from astrocytomas (derived from glial tissue) to chemodectomas (derived from sympathetic nervous tissue). Several different types of germ cell tumors arise from the tissues in this region, presumably from embryonal cell rests. In the United States, pineal tumors account for only 1% of intracranial tumors, but one-third of these pineal tumors are germ cell tumors, including germinomas and choriocarcinomas.
177. The answer is c. (Ropper, p 986.) With von Hippel-Lindau syndrome, the patient may exhibit tumors in multiple organs. In the brain, hemangioblastomas are the tumors most likely to arise, and these tumors are usually limited to the cerebellum or brainstem. Hemangioblastomas are often multiple and become symptomatic by bleeding into themselves. The initial episode of bleeding may prove lethal.
178. The answer is e. (Ropper, pp 612-655.) The headache is typical of that caused by intracranial hypertension. Additionally, the patient has focal neurological symptoms and signs. This creates particular concern about a brain tumor or hemorrhage, and the patient should be evaluated as soon as possible. An appointment next month is too late. Intravenous prochlorperazine is a good treatment for status migrainosus; however, this history is atypical for such a diagnosis, and more serious problems should be ruled out first in the emergency room. Zolmitriptan is a treatment for migraines. This history is not typical for migraine, and zolmitriptan is also relatively contraindicated in patients with complex migraine. This history is very atypical for seizures, and an EEG is not likely to provide useful information in this case.
179. The answer is b. (Ropper, pp 631-634.) The breast, lung, kidney, skin, and uterus are all common sources of metastases to the brain. The incidences of metastases from the lung account for two-thirds of cases of brain metastasis presenting without a known primary. Skin lesions metastasizing to the brain include malignant melanomas.
180. The answer is a. (Ropper, pp 631-634.) Metastatic lesions are spread primarily by the vascular system. The gray–white junction (where the white matter and the gray matter meet) is the interface at which bloodborne cells are most likely to lodge and grow. No part of the brain is exempt from the spread of metastases, but the cerebral hemispheres and the cerebellum are especially vulnerable.
181. The answer is a. (Ropper, pp 631-634.) The outlook with malignant melanoma, breast cancer, lung cancer, or renal cancer metastatic to the brain is poor and limited to a matter of months, but malignant melanoma is especially grim because it is highly likely to bleed after it metastasizes to the brain. Malignant melanoma and choriocarcinoma are likely to produce lethal intracranial hemorrhages, and the former may in fact first become apparent only after it has precipitated an intracranial hemorrhage. Prostate cancer does not typically metastasize to the brain.
182. The answer is b. (Ropper, pp 643-644.) Colloid cysts may produce transient or persistent obstruction of the flow of cerebrospinal fluid (CSF). Because this is an especially deep-seated lesion, it may be more practical to simply shunt the fluid from the lateral ventricles rather than attempt to excise the cyst. These cysts are usually lined with epithelial cells and may arise from a variety of sources, including low-grade neoplasms that involute early in their evolution.
183. The answer is c. (Ropper, p 729.) Kaposi 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 (ie, 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.
184. The answer is d. (Ropper, pp 648-651.) With bitemporal hemianopsia, the visual fields in both eyes are impaired, but only the temporal quadrants of the field in each eye are affected. Pressure on the optic chiasm inferiorly by a tumor arising in or near the sella turcica will crush the fibers crossing in the chiasm from the medial aspects of the optic nerves. The most medial fibers in both optic nerves are contributed by the nasal aspects of the retina. The nasal or medial aspects of the retina receive light from the temporal or lateral aspects of the visual field.
185. The answer is e. (Swaiman, pp 1701, 2115-2116.) 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 caused by 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.
186. The answer is a. (Ropper, pp 349-351.) 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.
187. The answer is i. (Ropper, pp 630-631.) Patients with AIDS are at risk for numerous CNS infections, but have an increased frequency of only two tumor types: lymphoma and Kaposi sarcoma (KS). KS may metastasize to the CNS, but lymphoma is routinely primary to the CNS. This tumor may produce blindness through direct invasion of the optic nerve.
188. The answer is a. (Ropper, pp 637-638.) Medulloblastomas are one of the most common CNS tumors of childhood. They typically develop in the cerebellum, causing ataxia. Astrocytomas may also occur in children infratentorially, primarily in the cerebellum and brainstem. In either location, hydrocephalus may develop because of obstruction at the level of the fourth ventricle. The astrocytoma that develops in the cerebellum is usually cystic. Medulloblastomas are invariably infratentorial, at least initially. They may extend supratentorially or become disseminated supratentori-ally through seeding of cells carried in the CSF. Ependymomas, another common tumor type in children, are derived from the lining of the ventricles and also carry the risk of hydrocephalus and seeding throughout the CNS.
189. The answer is c. (Ropper, pp 652-653.) The neurofibromatoses are a pair of hereditary neurocutaneous syndromes that result in a variety of congenital and later-occurring abnormalities and neoplasms affecting the skin, nervous system, and other organs. Neurofibromatosis (NF) type 1, also called peripheral NF, is characterized by café au lait spots, which are light to dark brown spots found on the skin; multiple cutaneous and subcutaneous tumors; bone cysts; sphenoid bone dysgenesis; precocious puberty; pheochromocytoma; syringomyelia; glial nodules; cortical dysgenesis; and macrocephaly. Optic nerve tumors are a particularly worrisome complication and may produce blindness in children.
190. The answer is e. (Ropper, pp 644-646.) Schwannomas usually develop on the vestibular division of CN VIII and are pathologically derived from Schwann cells rather than nerve tissue and are therefore more appropriately called vestibular schwannomas than acoustic neuromas (the traditional name). Although this is not the division of the nerve that carries information from the cochlea, the cochlear division is crushed as the tumor expands. This type of tumor is especially likely with NF type 2, a hereditary disorder characterized by a variety of tumors in the skin and nervous system.
191. The answer is h. (Ropper, p 641.) Pineocytomas are histologically benign lesions affecting the region of the pineal gland. They arise from the parenchymal cells of the pineal gland. This patient’s symptoms and signs constitute Parinaud syndrome, which may include loss of vertical gaze, loss of pupillary light reflex, lid retraction, and convergence–retraction nystagmus, in which the eyes appear to jerk back into the orbit on attempted upgaze. This syndrome occurs in lesions owing to involvement of the dorsal midbrain in the region of the superior colliculus. Other tumors appearing in the pineal region that can produce a similar clinical picture include germ cell tumors (germinomas), teratomas, and gliomas. Malignant pineal tumors, or pineoblastomas, may also occur, and are similar histologically to medulloblastomas.
192. The answer is a. (Ropper, pp 655-661.) Paraneoplastic cerebellar degeneration is characterized by subacute and relentlessly progressive ataxia, dysarthria, and nystagmus. Myoclonus, opsoclonus (irregular jerking of the eyes in all directions), diplopia, vertigo, and hearing loss may also occur. Imaging may eventually reveal cerebellar atrophy, and pathology will disclose loss of Purkinje cells in the cerebellum as the primary abnormality. The most common associated tumor types are small cell carcinoma of the lung, ovarian carcinoma, and lymphoma, in that order. Approximately 50% of patients may harbor anti-Purkinje cell antibodies (called anti-Yo antibodies), and these are especially commonly found in women with breast cancer or gynecologic malignancies. Interestingly, the symptoms of paraneoplastic cerebellar degeneration often precede the symptoms of the underlying tumor itself, leading to speculation that the immune reaction that damages the nervous system may, in fact, be protective against the tumor.
193. The answer is d. (Ropper, p 1097.) Hypercalcemia may occur as a complication of cancer in up to 5% of patients. It may be a result of parathyroid-related peptide secreted by the tumor itself (usually a lung cancer) or of bone destruction by metastatic disease. The elevated serum calcium decreases membrane excitability, leading to the clinical syndrome of fatigability, lethargy, generalized weakness, and areflexia. In more severe cases, coma and even convulsions can occur. Symptoms usually do not occur until levels reach 14 mg/dL or higher.
194. The answer is l. (Ropper, pp 1417-1418.) The Lambert-Eaton myasthenic syndrome (LEMS) shares some features with myasthenia gravis, notably proximal muscle weakness. It usually develops subacutely, however, and spares the bulbar musculature and eyes. There is also little response to anticholinesterase drugs. A characteristic feature is the increase in strength briefly after repeated muscle activation. Most cases are associated with an underlying oat cell carcinoma of the lung or other malignancy. In other cases, LEMS may be associated with other autoimmune illness. The underlying defect is the loss of function of the voltage-sensitive calcium channels in the presynaptic nerve terminal at the neuromuscular junction, attributed to cross-linking and aggregation by pathologic IgG autoantibodies. Various immune-modulating therapies, as well as 3,4-diaminopyridine, have been used with varying success. Removal of the underlying malignancy may also be curative.
195. The answer is i. (Ropper, pp 1289-1290.) Polyneuropathy may occur in up to 15% of patients with multiple myeloma. This generally takes the form of a chronic distal symmetrical sensory or sensorimotor neuropathy. In some cases, the neuropathy progresses more aggressively, and the patient becomes confined to a wheelchair. Spinal fluid protein may be elevated, and the illness has the appearance of a chronic inflammatory demyelinating polyneuropathy. Up to 20% of patients referred for evaluation of polyneuropathy may have an underlying monoclonal paraproteinemia. In the absence of an obvious malignancy, this is called a monoclonal gammopathy of undetermined significance, but a hematologic malignancy may later turn up in as many as one-third of such patients.