C h a p t e r 3 7
Disorders of Brain Function
943
It depends on the histologic grade of the tumor, its loca-
tion, and, more recently, recognition of molecular fea-
tures that can be linked to chemosensitivity.
50
Due to
their delicate vasculature, the oligodendroglial tumors
are prone to spontaneous hemorrhage.
Ependymomas.
Ependymomas are derived from the
single layer of epithelium that lines the ventricles and
spinal canal. Although they can occur at any age, they
are most likely to occur in the first two decades of life
and most frequently affect the fourth ventricle; they con-
stitute 5% to 10% of brain tumors in this age group.
1
In adults, the spinal cord is the most common location.
The clinical features depend on the location of the neo-
plasm. Intracranial tumors are often associated with
hydrocephalus and evidence of increased ICP.
Medulloblastomas
Tumors of neuronal origin (e.g., medulloblastomas)
usually occur during infancy and childhood.
48
This is in
accord with the principle that a cell must be capable
of replication to undergo neoplastic transformation.
Medulloblastoma is thought to originate from a primi-
tive cell type in the cerebellum arising from one of two
cerebellar germinal zones: the ventricular zone that
forms the outermost boundary, or the external germinal
layer that lines the outside of the cerebellum.
Medulloblastomas have a bimodal distribution, peak-
ing at 3 or 4 years of age and then again at 8 or 9 years
of age.
48
Children usually present with signs and symp-
toms of increased ICP (i.e., headache, nausea, vomiting,
mental status changes, hypertension) and cerebellar dys-
function (i.e., ataxia, balance problems, movement disor-
ders). The tumor is highly malignant, and the prognosis
for untreated children is dismal. However, the tumor is
highly radiosensitive; with total excision and irradiation,
the 5-year survival rate is as high as 75%.
Meningiomas
Meningiomas develop from the meningothelial cells of
the arachnoid and are outside the brain. They usually
have their onset in the middle or later years of life and
constitute approximately 20% of primary brain tumors
in this age group.
1
Meningiomas are slow-growing, well-
circumscribed, and often highly vascular tumors. They
usually are benign, and complete removal is possible if
the tumor does not involve vital structures.
Primary Central Nervous System Lymphomas
Primary CNS lymphomas have increased in incidence by
a factor of 10 in the past several decades.
1,4
These deep,
periventricular, and diffuse tumors are especially com-
mon in immunocompromised persons, including those
with acquired immunodeficiency syndrome (AIDS) and
immunosuppression after transplantation.
Most primary brain lymphomas are of B-cell origin.
Primary lymphomas of the CNS are highly aggressive,
and recurrence is common despite treatment. Behavioral
and cognitive changes, which are the most common
presenting symptoms, occur in about 65% of patients;
hemiparesis, aphasia, and visual field deficits in about
50%; and seizures in 15% to 20%.
MetastaticTumors
Metastatic tumors, mostly carcinomas, affect approxi-
mately 20% to 40% of persons with cancer.
50
The
five most common sites for metastasis are the lung,
breast, skin (melanoma), kidney, and gastrointestinal
tract.
1,52,53
Within the brain there is regional selectiv-
ity for growth metastasis from the different primary
types of cancer: melanoma is more typically found
in the frontal and temporal lobes, breast cancer in
the cerebellum and basal ganglia, and non–small cell
lung cancer in the occipital lobe. Thus, it appears that
tumor-specific interactions with brain tissue mediate
the establishment and proliferation of brain metas-
tasis. Recent investigations have begun to elucidate
the mechanisms of such molecular mechanisms. For
women with breast cancer, hormone receptor and
human epidermal growth factor receptor-2 status is
predictive of brain metastasis risk.
50
Clinically evident brain metastases present with signs
of increased ICP, mental status changes, seizures, and
focal neurologic deficits. Management of persons with
CNS metastasis consists of symptomatic and definitive
therapies. The mainstays of symptomatic control are
corticosteroids for tumor-related edema, antiepileptic
drugs for seizure control, and multidisciplinary inter-
ventions aimed at minimizing neurologic disability.
50–52
Manifestations
The clinical manifestations of brain tumors depend on
the size and location of the tumor. General signs and
symptoms include headache, nausea, vomiting, mental
changes, papilledema, visual disturbances (e.g., dip-
lopia), alterations in sensory and motor function, and
seizures.
7,47
Because the volume of the intracranial cav-
ity is fixed, brain tumors cause a generalized increase in
ICP when they reach sufficient size or produce edema.
Cerebral edema usually is of the vasogenic type, which
develops around the tumors and is characterized by
an increased extracellular fluid volume. The edema is
thought to result from increased permeability of tumor
capillary endothelial cells. Tumors can also obstruct
the flow of CSF in the ventricular cavities and produce
hydrocephalic dilation of the proximal ventricles and
atrophy of the cerebral hemispheres. With very slow-
growing tumors, complete compensation of ventricular
volumes can occur, but with rapidly growing tumors,
increased ICP is an early sign.
The brain itself is insensitive to pain. The headache
that accompanies brain tumors results from compres-
sion or distortion of pain-sensitive dural or vascular
structures. It may be felt on the same side of the head
as the tumor, but more commonly is diffuse. In the early
stages, the headache is mild and occurs in the morning
on awakening and improves with head elevation. The
headache becomes more constant as the tumor enlarges
