Neurosurgery for Hydrocephalus

8/10/2019 Neurosurgery for Hydrocephalus

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Neurosurgery for Hydrocephalus

Author: Herbert H Engelhard III, MD, PhD, FACS; Chief Editor: Allen R Wyler, MD

History of the Procedure

Hydrocephalus was first described by Hippocrates. Hydrocephalus was not treated effectively

until the mid 20th century, when the development of appropriate shunting materials and

techniques occurred. Interestingly, at the beginning of the 20th century, doctors (including

urologists) attempted to introduce scopes into the ventricular system. Attempts were also

made to remove the choroid plexus, which generates much of the cerebrospinal fluid (CSF),

in an attempt to treat hydrocephalus. Today, the focus of hydrocephalus research is on

pathophysiology, valve design in shunting, and minimally invasive techniques of treatment.

An image depicting hydrocephalus can be seen below.

Noncommunicating obstructive hydrocephalus caused byobstruction of the foramina of Luschka and Magendie. This MRI sagittal image demonstrates

dilatation of lateral ventricles with stretching of corpus callosum and dilatation of the fourth

ventricle.

Problem

Hydrocephalus is the abnormal rise in CSF volume and, usually, pressure, that results from

an imbalance of CSF production and absorption.

Epidemiology

Frequency

The overall incidence of hydrocephalus is unknown. When cases ofspina bifida are included,

congenital hydrocephalus occurs in 2-5 births per 1000 births. Incidence of acquired types of

hydrocephalus is unknown.

Tanaka et al concluded that the incidence of idiopathic normal pressure hydrocephalus was

1.4% in their study of an elderly Japanese population.[1]
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Etiology

The etiology of hydrocephalus in congenital cases is unknown. Very few cases (< 2%) are

inherited (X-linked hydrocephalus). The most common causes of hydrocephalus in acquired

cases are tumor obstruction, trauma,intracranial hemorrhage,and infection.

Pathophysiology

Hydrocephalus can be subdivided into the following 3 forms:

Disorders of CSF production: This is the rarest form of hydrocephalus. Choroid

plexus papillomas and choroid plexus carcinomas can secrete CSF in excess of its

absorption.

Disorders of CSF circulation: This form of hydrocephalus results from obstruction of

the pathways of CSF circulation. This can occur at the ventricles or arachnoid villi.

Tumors, hemorrhages, congenital malformations (such as aqueductal stenosis), and

infections can cause obstruction at either point in the pathways.

Disorders of CSF absorption: Conditions, such as the superior vena cava syndrome

and sinus thrombosis, can interfere with CSF absorption. Some forms of

hydrocephalus cannot be classified clearly. This group includes normal pressure

hydrocephalus andpseudotumor cerebri.

Presentation

The various types of hydrocephalus can present differently in different age groups.

Acute hydrocephalus typically presents with headache, gait disturbance, vomiting, and visualchanges. In infants, irritability or poor head control can be early signs of hydrocephalus.

When the third ventricle dilates, the patient can present with Parinaud syndrome (upgaze

palsy with a normal vertical Doll response) or the setting sun sign (Parinaud syndrome with

lid retraction and increased tonic downgaze). Occasionally, a focal deficit, such as sixth nerve

palsy, can be the presenting sign. Papilledema is often present, although it may lag behind

symptomatology. Infants present with bulging fontanelles, dilated scalp veins, and an

increasing head circumference. When advanced, hydrocephalus presents with brainstem signs,

coma, and hemodynamic instability.

Normal pressure hydrocephalus has a very distinct symptomatology. The patient is older and

presents with progressive gait apraxia, incontinence, and dementia. This triad of symptomsdefines normal pressure hydrocephalus.

Indications

Most cases of symptomatic hydrocephalus need to be treated before permanent neurologic

deficits result or neurologic deficits progress.

When an etiologic factor is known, hydrocephalus can be treated with temporary measures

while the underlying condition is treated. Examples of temporary treatment measures are

ventriculostomy until a posterior fossa tumor is resected or lumbar punctures in a neonate
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with intraventricular hemorrhage until the blood is absorbed and normal cerebrospinal fluid

(CSF) absorption resumes.

Relevant Anatomy

See Intraoperative details for a discussion of relevant anatomy.

Contraindications

Few cases of hydrocephalus should not be treated. Cases in which treatment should not be

implemented include the following:

The patient in whom a successful surgery would not affect the outcome (eg, a child

with hydranencephaly)

In ventriculomegaly of senescence, the patient who does not have the symptom triad

Ex vacuo hydrocephalus is merely the replacement of lost cerebral tissue withcerebrospinal fluid. Because no imbalance in fluid production and absorption exists,

this technically is not hydrocephalus.

Arrested hydrocephalus is defined as a rare condition in which the neurologic status

of the patient is stable in the presence of stable ventriculomegaly. The diagnosis must

be made extremely carefully because children can present with very subtle

neurological deterioration (eg, slipping school performance) that is difficult to

document.

Benign hydrocephalus of infancy is found in neonates and young infants. The children

are asymptomatic, and head growth is normal. CT scan shows mildly enlarged

ventricles and subarachnoid spaces.

Imaging Studies

CT scan of the head delineates the degree of ventriculomegaly and, in many cases, the

etiology. When performed with contrast, it can show infection and tumors that cause

obstruction. It also helps with operative planning. Ventricles are usually dilated

proximal to the point of obstruction. In pseudotumor cerebri, the CT scan findings are

usually normal.

Perform MRI scan of head in most, if not all, congenital cases of hydrocephalus. This

delineates the extent of associated brain anomalies such as corpus callosum agenesis,

Chiari malformations, disorders of neuronal migration, and vascular malformations.

Some tumors, for example the midbrain tectal gliomas, only can be detected with thisstudy. T2-weighted images can show transependymal flow of cerebrospinal fluid

(CSF).

Fetal and neonatal cranial ultrasound is a good study for monitoring ventricular size

and intraventricular hemorrhage in the neonatal ICU setting. Certainly, prior to

treatment, perform other imaging studies.

Diagnostic Procedures

Lumbar puncture can be used to measure intracranial pressure, but it should only be

performed after imaging studies rule out an obstruction. A diagnostic high-volume lumbar
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puncture in normal pressure hydrocephalus can assist in making decisions regarding shunting.

Spinal fluid can show the type and severity of infection (see the eMedicine articleMeningitis).

Medical Therapy

Medical therapy is usually a temporizing measure. In transient conditions, such as sinusocclusion, meningitis, or neonatal intraventricular hemorrhage, medical therapy can be

effective.

Acetazolamide (25 mg/kg/d in 3 doses): Careful monitoring of respiratory status and

electrolytes is crucial. Treatment beyond 6 months is not recommended.

Furosemide (1 mg/kg/d in 3 doses): Again, electrolyte balance and fluid balance need

to be monitored carefully.

Lumbar punctures: In neonates recovering from intraventricular hemorrhage, serial

lumbar punctures can, in some cases, resolve hydrocephalus. If possible, this is the

preferred method of treatment.

Removal of the underlying cause usually resolves hydrocephalus.

Surgical Therapy

As performance of cerebrospinal fluid (CSF) diversion (most often ventriculoperitoneal

shunting) has increased in frequency, so has awareness of the pitfalls of the procedure.

Recently, a resurgence of interest in third ventriculostomies has occurred.

Preoperative Details

Make every effort to identify the cause of hydrocephalus prior to considering a diversionprocedure.

Do not consider an indwelling distal catheter in patients with active infection or high

cerebrospinal fluid protein (>150 mg/dL).

Obtain some idea of brain compliance in order to select the optimum valve pressure and

decide if the pressure-programmable valve should be used.

Use one dose of preoperative prophylactic antibiotics.

Intraoperative Details

Third ventriculostomy: Reserve this procedure for obstructive cases in patients who

have normal or near-normal spinal fluid absorptive capacity. Use a blunt instrument to

penetrate the floor of the third ventricle. Sharp instruments or lasers can cause

vascular injury. Leaving a clamped drain in place postoperatively might be prudent.

The burr hole placed on the coronal suture allows a straight trajectory to the foramen

of Monro. Stereotactic guidance is not needed if endoscopic techniques are used.

Ventriculoperitoneal shunting: This procedure is by far the most common procedure

for CSF diversion. The abdomen should be able to absorb the excess spinal fluid.

Either 1 of 2 major locations for the burr holes are typically used. The ventricularcatheter can be placed more reliably from the (right) frontal approach. Some surgeons
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still prefer parietooccipital catheters. The proximal catheter tip should lie anterior to

the choroid plexus in the frontal horn of the lateral ventricle when the parietooccipital

approach is used. Certain landmarks and measurements are used, as per neurosurgical

texts. In difficult cases, stereotactic placement may be an option.

Ventriculoatrial shunting: This procedure is usually the first choice for patients who

are unable to have distal abdominal catheters (eg, multiple operations, recentabdominal sepsis, known malabsorptive peritoneal cavity, abdominal pseudocyst).[2]

The procedure carries more risk. Long-term complications are more serious (eg, renal

failure, great vein thrombosis). Fluoroscopic guidance is necessary to prevent catheter

thrombosis (short distal catheter) or cardiac arrhythmias (long distal catheter).

Ventriculopleural shunting: Reserve this procedure for patients with failed peritoneal

and atrial shunts.

Torkildsen shunts or internal shunts are straight tubes that communicate to

cerebrospinal fluid spaces without a valve. Their effectiveness and long-term efficacy

are not proven.

Lumboperitoneal shunts are used in communicating hydrocephalus, especially if

ventricles are small. Pseudotumor cerebri is the classical indication of this method ofshunting. A positional valve is helpful because it turns off the flow of CSF when the

patient is upright, thereby preventing overdrainage headache.

Postoperative Details

ICU observation after third ventriculostomy is advised.

In patients with high brain compliance, gradual assumption of the upright position and slow

mobilization may reduce the incidence of early subdural hematoma formation.

Plain radiographs of the entire hardware system confirm good position and serve as excellent

baseline studies for the future. Postoperative CT scan is used to document ventricular size

(see Follow-up section).

Wounds should remain dry for at least 3 days postoperatively, until epithelialization has

occurred.

In patients with pleural shunts, perform an early postoperative chest radiograph to ensure

adequate absorption of fluid. Large effusions can occur in short periods, and respiratory

problems can ensue.

If the patient has no clinical indicators of ventriculitis, CSF sampling from extraventricular

drains should be performed once every 3 days, which reportedly decreases the incidence of

ventriculitis.[3]

Follow-up

Remove stitches by 2 weeks postsurgery.

Perform CT scan for baseline at 2-4 weeks postsurgery.

Monitor all children with shunts every 6-12 months. Carefully monitor head growth in

infants. Check distal tubing length with plain radiographs when the child grows.

Appropriate specialists should carefully assess child development.


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What happens to ventricular size in patients who have a third ventriculostomy or

Torkildsen shunt is not known. Other methods of assessment of patency need to be

used, such as MRI flow studies and clinical evaluations (eg, detailed funduscopic

examinations).

In patients with pseudotumor cerebri, visual acuity and fields should be monitored by

the appropriate specialist.

Complications

The most common complications differ depending on the type of shunt and the underlying

pathophysiology.

Infection is the most feared complication in the young age group. The overwhelming majority

of infections occur within 6 months of the original procedure. Common infections are

staphylococcal and propionibacterial. Early infections occur more frequently in neonates and

are associated with more virulent bacteria such asEscherichia coli. Infected shunts need to be

removed, the cerebrospinal fluid (CSF) needs to be sterilized, and a new shunt needs to be

placed. Treatment of infected shunts with antibiotics alone is not recommended because

bacteria can be suppressed for extended periods and resurface when antibiotics are stopped.

Subdural hematomas occur almost exclusively in adults and children with completed head

growth. Incidence of subdural hematomas can be reduced by slow postoperative mobilization

and perhaps by avoiding rapid intraoperative ventricular decompression. This allows for brain

compliance reduction. The treatment is drainage and may require temporary occlusion of the

shunt.

Shunt failure is mostly due to suboptimal proximal catheter placement. Occasionally, distalcatheters fail. Suspect infection if the distal catheter is obstructed with debris. Abdominal

pseudocysts are synonymous with low-grade shunt infection.

Overdrainage is more common in lumboperitoneal shunts and manifests with headaches in

the upright position. In most cases, overdrainage is a self-limiting process. However, revision

to a higher-pressure valve or a different shunt system occasionally may be necessary. A

positional valve that closes when the patient is upright is also available.

Slit ventricle syndrome is an extremely rare condition in which brain compliance is unusually

low. It mostly occurs in the setting of prior ventriculitis or shunt infection. The patient may

develop high pressures without ventricular dilatation. The slit ventricle syndrome does notimply overdrainage, and the symptoms usually are those of high pressure rather than low

pressure. Most experts also agree that slit ventricles predispose the patient to a higher

incidence of ventricular catheter failure. Repeated ventricular blockage by the coapted

ventricular wall may be helped by performing a subtemporal decompression that creates an

artificial pressure reservoir and induces slight reenlargement of the slit ventricle.

Outcome and Prognosis

In general, outcome is good. A typical patient should return to baseline after shunting, unless

prolonged elevated intracranial pressure or brain herniation has occurred. The neurologic

function of children is optimized with shunting. Infection, especially if repeated, may affectcognitive status.


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The best long-term results in the most carefully selected patients are no better than 60% in

normal pressure hydrocephalus. Few complete recoveries occur. Often, gait and incontinence

respond to shunting, but dementia responds less frequently.

Often, various other neurologic abnormalities associated with hydrocephalus are the limiting

factor in patient recovery. Examples are migrational abnormalities and postinfectioushydrocephalus.

Future and Controversies

Hydrocephalus research and treatment have advanced tremendously in the last 20 years.

Examples are the development of new shunt materials and, more recently, programmable

valve technology. Current research categories include the following:

Transplantation of tissue, such as vascularized omentum, to reestablish normal

cerebrospinal fluid (CSF) could be the best method to treat communicating

hydrocephalus.

Third ventriculostomies and aqueductoplasty eliminate the need for shunting in

noncommunicating cases of hydrocephalus. New optics and smaller scopes have

expanded this field over the last 5 years.

Documents

Neurosurgery for Hydrocephalus