Hydrocephalus

Donna C. Wallace and Michele M. Grigaitis

Keywords: cerebrospinal fluid, endoscopic third ventriculostomy, intracranial pressure, lumboperitoneal shunt, normal pressure hydrocephalus, ventriculoperitoneal shunt

4.1 Hydrocephalus

Hydrocephalus is a condition that results in dilatation of the cerebral ventricles, usually after blockage of the cerebrospinal fluid (CSF) pathways in the brain (Video 4.1). It was recognized early on by the Greeks, who treated it by puncturing the swollen ventricles with reeds or by banding the skull to prevent it from expanding further. The Greek physician Galen (129–200 AD) theorized that the cerebral ventricles communicated with one another and posited that the ventricles were the vessels that transported waste products through the pituitary gland. Centuries later, Vesalius (1514–1564) was able to describe the mechanisms of hydrocephalus more clearly.

In patients with hydrocephalus, CSF does not travel from its point of production in the ventricles to its point of absorption in the systemic circulation. Hydrocephalus is generally classified according to its point of obstruction; however, this classification system is the subject of much debate.

Hydrocephalus is often considered to primarily affect children, but it also occurs in adults with certain neurologic conditions or diseases. Because this handbook addresses neurologic concerns in adult patients only, our discussion on hydrocephalus and its implications will be limited to the adult population (Box 4.1 Conditions Associated with Hydrocephalus).

4.1.1 Classification of Hydrocephalus

Hydrocephalus is sometimes divided into two distinct types: obstructive and communicating ( Fig. 4.1).

Obstructive Hydrocephalus

• Also referred to as noncommunicating hydrocephalus ( Fig. 4.2)

• Caused by tumors, congenital abnormalities of the brain, cysts, inflammation resulting from infection, or other conditions that interfere with patency of the CSF pathways.

  

  Fig. 4.2 Injected contrast agent in only one lateral ventricle, suggestive of obstructive hydrocephalus.

Communicating Hydrocephalus

• Occurs when the arachnoid villi can no longer adequately absorb CSF ( Fig. 4.3)

• Caused by intraventricular or subarachnoid hemorrhage or by some infections.

  

  Fig. 4.3 Symmetric enlarged ventricles demonstrate possible communicating hydrocephalus.

Idiopathic Normal Pressure

• Type of communicating hydrocephalus

• Etiology unknown

4.1.2 Pathophysiology of Hydrocephalus

• Most CSF is produced by the choroid plexus in the ventricles, but it is also produced in other areas along the neuraxis ( Fig. 4.4). In adults, CSF is replaced several times each day, and roughly 400 to 500 mL of CSF is produced daily. The total amount of CSF in the ventricles, brain, and along the neuraxis is about 150 mL at any given time

• CSF flow occurs as follows

  • CSF travels from the lateral ventricles through the two foramina of Monro to the third ventricle and then through the aqueduct of Sylvius to the fourth ventricle ( Fig. 4.5)

  • CSF continues down the spinal canal in the posterior portion of the spinal sac and returns to the brain

  • As CSF circulates over the cerebral hemispheres, it is absorbed into the sagittal sinus via the arachnoid villi

• Hydrocephalus results from

  • Failure of the CSF absorption mechanism

  • Obstruction of the CSF pathway

  • Overproduction of CSF (rare).

    

    Fig. 4.4 Flow of cerebrospinal fluid.

    

    Fig. 4.5 Cerebrospinal fluid pathway.

Epidemiology

• The rate of persons born with congenital hydrocephalus is 0.5 to 4 per 1000 persons

• The actual number of people living with hydrocephalus is hard to determine

• Approximately 25,000 shunting procedures are performed annually in the United States, but some believe this number may be as high as 50,000

Etiology

Congenital

• Neonatal developmental anomaly

• Genetic disorders

• Intracranial abnormalities

  • Dandy–Walker malformation (occurs when the roof of the fourth ventricle does not develop and the ventricle therefore becomes enlarged)

  • Aqueductal stenosis ( Fig. 4.6)

  • Choroid plexus papilloma (resulting in the overproduction of CSF)

  • Spina bifida.

    

    Fig. 4.6 Hydrocephalus resulting from aqueductal stenosis.

Acquired

• Aqueductal stenosis (may not show symptoms until older, or may be acquired after infection or bleeding)

• Subarachnoid, intraventricular, or intracranial hemorrhage (Box 4.2 Hydrocephalus in Patients with Subarachnoid Hemorrhage)

• Bacterial, viral, fungal, or parasitic infection (after which the pathways on the arachnoid villi are blocked)

• Tumor, cyst, or other obstruction

• Arnold-Chiari malformation

• Traumatic brain injury or swelling of the brain

• Thrombosis of the superior sagittal sinus

Clinical Manifestations

• Visual changes, especially diplopia

• Cognitive changes

• Change in personality

• Changes in vital sign, including bradycardia and hypertension; see also Chapter 3: Principles of Intracranial Pressure

• Pathologic reflexes

• Upward gaze palsy

• Headache

• Seizures (rare)

Idiopathic Normal Pressure Hydrocephalus

• Insidious onset, usually after the age of 40 years. The average age of persons who develop idiopathic NPH is over 60 years (Box 4.3 Pain Management in the Elderly)

• Minimum duration is 3 to 6 months

• No evidence of antecedent event (e.g., traumatic brain injury and stroke)

• Progresses over time

• Symptom triad

  • Gait disturbance

  • Cognitive deficit

  • Urinary incontinence

4.1.3 Diagnosis of Hydrocephalus

History

• Patient’s chief complaint

• History of shunt placement (i.e., when shunt was placed, what type of shunt the patient received, and previous valve settings) (Box 4.4 Shunt Failure)

• Any other neurological history (e.g., tumor)

Assessment

The classic symptom triad in patients with hydrocephalus includes dementia, urinary incontinence, and abnormal gait. An adequate assessment should include each of the following components:

• Level of consciousness (LOC)

• Cranial nerve assessment

• Motor, sensory, cognitive, and gait assessment

• Visual acuity

• Incontinence

• Cognitive testing (specifically for NPH)

  • Folstein’s Mini–Mental State Examination

Diagnostic Tools

Health care practitioners may use various tools to diagnose hydrocephalus ( Table 4.1).

Computed Tomography

• A computed tomography (CT) scan is the imaging study of choice in patients with suspected or confirmed hydrocephalus. It shows

  • Ventricular size

  • Position of an existing intraventricular catheter

Magnetic Resonance Imaging

• Magnetic resonance imaging (MRI) shows more detail than CT scan

• No radiation

• Fast-spin echo or “one bang” MRI is a rapid scan (approximately 3 minutes in duration) that does not require sedation

• Programmable shunts may require plain radiographs to check settings after MRI, because the magnet in MRI may change valve settings

Shuntogram

• Shuntogram, also called radionuclide cisternography, shows CSF flow through the shunt, recording emptying time and demonstrating possible obstruction

• Used to determine shunt function if the patient is not responding to therapy

Cine MRI

• A video-style MRI that shows the movement of CSF flow

Lumbar Puncture

• May be used to obtain CSF cultures

• Contraindicated until a space-occupying lesion has been ruled out, because lumbar puncture could cause herniation in the presence of a space-occupying lesion; see also Chapter 3: Principles of Intracranial Pressure

• A large-volume tap is used to assess NPH (patient’s condition may improve after removal of large volume of CSF)

4.1.4 Treatment of Hydrocephalus

Medical/Conservative

• Observation

• Acetazolamide may be tried in some circumstances

Surgical

• Serial lumbar punctures

• Shunts (discussed later) and shunt taps (Box 4.5 Focus On: Shunt Taps)

• Endoscopic third ventriculostomy (ETV)

  • An endoscope is used to create a hole in the floor of the third ventricle, thereby creating a diversion for CSF around the obstruction

Box 4.5 Focus On: Shunt Taps

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