C h a p t e r 3 7
Disorders of Brain Function
923
reabsorption of CSF, or obstruction of CSF flow in the
ventricular system.
Pathophysiology.
There are two types of hydroceph
alus: communicating and noncommunicating.
4,7
Com
municating hydrocephalus
is caused by impaired
reabsorption of CSF from the arachnoid villi into the
venous system. Decreased absorption can result from a
block in the CSF pathway to the arachnoid villi or a
failure of the villi to transfer the CSF to the venous sys-
tem. It can occur if too few villi are formed, if postinfec-
tive (meningitis) scarring occludes them, or if the villi
become obstructed with fragments of blood or infec-
tious debris. Adenomas of the choroid plexus can cause
an overproduction of CSF. This form of hydrocephalus
is much less common than that resulting from decreased
absorption of CSF.
Noncommunicating
or obstructive hydrocephalus
occurswhenobstruction in the ventricular systemprevents
the CSF from reaching the arachnoid villi. Cerebrospinal
fluid flow can be obstructed due to congenital malforma-
tions, tumors encroaching on the ventricular system, or
inflammation or hemorrhage. Similar pathologic patterns
occur with noncommunicating and communicating types
of hydrocephalus. The cerebral hemispheres become
enlarged, and the ventricular system beyond the point of
obstruction becomes dilated
4
(Fig. 37-5). The sulci on the
surface of the brain become effaced and shallow, and the
white matter reduced in volume.
Clinical Manifestations.
In adults and children in
whom the cranial sutures have fused, head enlargement
does not occur.
4
Acute-onset hydrocephalus usually is
marked by symptoms of increased ICP, including head-
ache, vomiting, and papilledema or deviation in eye
movements due to pressure on the cranial nerves.
7
If the
obstruction is not relieved, progression to herniation
ensues.
Signs and symptoms of hydrocephalus vary greatly,
depending on age and rapidity of onset. When hydro-
cephalus develops in utero or before the cranial sutures
of the skull have fused in infancy, the ventricles expand
beyond the point of obstruction, the cranial sutures
separate, the head expands, and there is bulging of the
fontanels. Because the skull is able to expand, signs of
increased ICP may be absent, and intelligence spared.
However, seizures are not uncommon, and in severe
cases, optic nerve atrophy leads to blindness. Weakness
and uncoordinated movement are common. Surgical
placement of a shunt allows for diversion of excess CSF
fluid, preventing extreme enlargement of the head and
neurologic deficits.
Diagnosis andTreatment.
The most common diagnos-
tic studies are computed tomographic (CT) and mag-
netic resonance imaging (MRI). The usual treatment is a
ventricular shunting procedure, which provides an alter-
native route for return of CSF to the circulation.
7
Normal Pressure Hydrocephalus.
An important type
of communicating hydrocephalus that is seen in older
adults is called
normal-pressure hydrocephalus
.
4,7
In
normal-pressure hydrocephalus, there is ventricular
enlargement with compression of cerebral tissue, but
a normal CSF pressure. The signs and symptoms of
normal-pressure hydrocephalus, which include memory
changes, disturbances in gait, and urinary incontinence,
usually have an insidious onset. The changes occur so
slowly that they can be easily overlooked by the patient
or his or her family or they may be attributed to the
aging process.
7
The accepted treatment for normal-pressure hydrocephalus is a ventricular shunt.
Traumatic Brain Injury
The term “head injury” is used to describe all struc-
tural damage to the head, including injury to the skull,
brain, or both. The leading causes of head injury are
motor vehicle accidents, bicycle crashes, battlefield
trauma, sports injuries, falls, and assaults.
9,10
Head
injury with concussion is becoming increasingly recog-
nized as a significant medical problem with significant
morbidity and sometimes devastating complications.
9
High-profile cases involving athletes and large num-
bers of returning armed services personnel with battle-
field injuries have brought concussions to the forefront
of concern for school athletic personnel and health
care professionals.
The physical forces associated with head injury may
result in skull fractures, brain injury, and vascular dam-
age, all three of which can coexist.
1,4
Skull fractures are
frequently accompanied by intracranial lesions, and the
presence of skull fracture greatly increases the risk of an
underlying subdural and/or epidural hemorrhage.
FIGURE 37-5.
Hydrocephalus. Horizonatal section of
the brain from a patient who died of a brain tumor that
obstructed the aqueduct of Sylvius shows marked dilation
of the lateral ventricles. (From Fuller GN, Goodman JC.
Central nervous system. In: Rubin R, Strayer DS, eds. Rubin’s
Pathology: Clinicopathologic Foundations of Medicine. 6th ed.
Philadelphia, PA: Wolters Kluwer Health | Lippincott Williams &
Wilkins; 2012:1302.)
