Second edition

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In turn, upward extension of a macroadenoma may impinge
on the optic chiasm, with a bitemporal hemianopia; on the
hypothalamus, with diabetes insipidus; or, in extreme cases,
on the frontal lobe, with cognitive changes and seizures.
Endocrinologic changes seen with secretory tumors most
commonly involve hyperprolactinemia, with amenorrhea in
females and gynecomastia and erectile dysfunction in males.
Excess growth hormone and adrenocorticotropic hormone
(ACTH) secretion are the next most common changes and
may cause acromegaly or Cushing’s disease respectively.
Gonadotropin and thyroid-stimulating hormone (TSH)
excess are rare. Importantly, in about 10 percent of secreting
adenomas, two or more hormones may be excessively produced.
In addition, in some cases of macroadenomas there
may be ‘kinking’ of the pituitary stalk, and in such cases
dopamine delivery to the posterior pituitary may be
impaired with a resultant secondary hyperprolactinemia.
Magnetic resonance scanning is typically positive with
macroadenomas; however, microadenomas of less than
3 mm in diameter may escape detection. In rare instances,
pituitary adenomas may undergo hemorrhage or infarction,
producing the syndrome of ‘pituitary apoplexy’ with severe
headache, diplopia, blindness, and, critically, an acute case of
adrenocortical insufficiency, which may be fatal.
Craniopharyngiomas are lobulated, calcified tumors
that, although most commonly occurring in children, may
occur in patients of any age. They typically arise from the
junction of the infundibulum and pituitary gland, and may
produce a variety of symptoms, depending on which direction
they grow in. With upward extension and impingement
of the hypothalamus, there may be diabetes insipidus
and obesity, and with compression of the third ventricle,
hydrocephalus may occur. Compression of the optic chiasm
may cause a bitemporal hemianopia, and with downward
extension various forms of pituitary failure may appear.
Pineal tumors include not only pinealomas but also
germ cell tumors, gliomas, and teratomas. These tumors
cause symptoms primarily by compression of the adjacent
quadrigeminal plate and the underlying aqueduct of Sylvius,
with a Parinaud syndrome (limitation of upgaze and an
Argyll Robertson pupil) and obstructive hydrocephalus
respectively.
Hemangioblastomas (Boughey et al. 1990) are cystic
masses found in the cerebellum, which typically contain an
enhancing nodule on MR scanning. They are found in children
or young adults, usually present with cerebellar symptoms,
and may occur as part of von Hippel–Lindau disease.
Colloid cysts of the third ventricle are rare cystic masses that
may cause dementia (Kelly 1951), either by compression of
the surrounding thalamus (Faris and Terrence 1989; Lobosky
et al. 1984) or as a result of obstructive hydrocephalus, as illustrated
in Figure 19.2. Interestingly, by virtue of a ‘ball-valve’
effect, in which the foramen of Monro is intermittently
occluded, these tumors may also cause intermittent elevations
of intraventricular pressure. Thus, patients may experience
intermittent headache, unsteadiness, and confusion, and
report that these symptoms are posture-dependent.
METASTATIC TUMORS
19.1 Brain tumors 599
Figure 19.2 This unenhanced computed tomography scan
demonstrates a colloid cyst, which, by obstructing the foramen of
Monro, has caused obstructive hydrocephalus with dilation of the
lateral ventricles. (Reproduced from Gillespie and Jackson 2000.)
Metastases may arise from various different primary
tumors and almost always reach the brain via hematogenous
spread. By far the most common source is lung cancer,
primarily the non-small-cell type, followed by breast
cancer and melanoma and then by various other tumors,
including those of the colon and rectum, kidney, gallbladder,
liver, thyroid, testicle, prostate, uterus or ovary, and
pancreas; both systemic lymphoma (primarily of the non-
Hodgkin’s type) and leukemia may also metastasize to the
brain. Of all these primaries, melanoma and testicular cancer,
although not common, exhibit the greatest propensity
for metastasis to the brain.
Two-thirds of metastases eventually settle in the brain
parenchyma, whereas the remainder lodge either in the
leptomeninges (where they create a condition known as
leptomeningeal carcinomatosis) or in the dura. Parenchymal
metastases may be found throughout the cerebrum (Delattre
et al. 1988a); they are found in the hemispheres in about
three-quarters of cases, in the cerebellum in about oneeighth,
and in the brainstem or thalamus in the remainder;
of those lodging in the hemispheres, all lobes may be
involved, including, in descending order, the frontal, parietal,
occipital, and temporal lobes.
Metastases to the parenchyma generally appear as
homogenously enhancing masses, often with considerable
peri-tumoral edema; in high-grade malignancies, however,
central necrosis may lead to a ring-enhancing pattern.
Although solitary lesions may occur, multiple tumors, as
noted earlier, are more common, and indeed at autopsy
one may find widespread, microscopic foci.