Hydrocephalus
Abstract
Hydrocephalus affects many patients with neurologic conditions. It is a result of dilatation of the ventricles in the brain, usually caused by blockage of the cerebrospinal fluid pathways. Because hydrocephalus can occur with many neurologic disorders, recognition of its symptoms and knowledge of its treatment are essential for nurses and all health care providers.
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).
Box 4.1 Conditions Associated with Hydrocephalus
Traumatic brain injury
Tumor
Subarachnoid hemorrhage
Meningitis
Encephalitis
Congenital anomaly
Arnold-Chiari malformation
Clotting disorder
Blood cancer
4.1.1 Classification of Hydrocephalus
Hydrocephalus is sometimes divided into two distinct types: obstructive and communicating (▶ Fig. 4.1).
Fig. 4.1 Depiction of ventricle size for each type of hydrocephalus.
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
Box 4.2 Hydrocephalus in Patients with Subarachnoid Hemorrhage
Hydrocephalus is common in patients with subarachnoid hemorrhage
The presence of blood and blood breakdown products in the subarachnoid space tends to clog the arachnoid granulations, hindering the absorption of CSF
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
Box 4.3 Pain Management in the Elderly
Patients with normal pressure hydrocephalus (NPH) tend to be elderly. Judicious pain management is warranted; however, the use of opioids and anticholinergic agents should be minimized in this population
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)
Box 4.4 Shunt Failure
Clinical manifestations of shunt failure are identical to symptoms of hydrocephalus
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).
Diagnostic study | Expected findings | Nursing implications |
CT | Ventricle size Location of existing catheter Bleeding Hemorrhage in subarachnoid space Midline shift | N/A |
MRI | Same as for CT More detailed imaging than CT Catheter not visible on MRI | No radiation Patient may require sedation if claustrophobic; if fast-spin echo MRI or “one bang” MRI is used, sedation may be unnecessary |
Cine MRI | Depicts CSF flow | Same as for MRI |
Lumbar puncture | Measurement of pressure Observation of CSF qualities; provides CSF for culture | Requires patient cooperation; nurse may need to assist with patient positioning Patient must remain flat for designated period after examination |
Venogram | Measures ICP and venous pressures in the heart; can help identify pressure gradients (blockage) | Same as for any operative procedure Patient will be anesthetized |
Shuntogram | Radionuclide injected to follow CSF flow through the shunt to determine its patency | Preparation of site Assisting in sterile removal of CSF for diagnostic procedure No special precautions |
Abbreviations: CSF, cerebrospinal fluid; CT, computed tomography; ETV, endoscopic third ventriculostomy; ICP, intracranial pressure; MRI, magnetic resonance imaging; N/A, not applicable. | ||
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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