Surgical Management of Hydrocephalus in the Adult

Management of the Adult Treated for Hydrocephalus as a Child

As much as 40% of pediatric neurosurgical practice in most large centers involves the treatment of hydrocephalus. The most common etiologic factor is premature birth and intraventricular hemorrhage. The presumption is that blood in the CSF causes either scarring in the subarachnoid space or sclerosis from inflammation at the absorptive surface of the arachnoid villi. This situation decreases the absorption rate of fluid and causes hydrocephalus with four-ventricle dilatation. This condition has been referred to as communicating or absorptive hydrocephalus. Other etiologies for an absorptive defect in children can be a congenital incontinence of the arachnoid villi for a variety of etiologic reasons or an obstruction within the CSF pathways that will cause ventricular dilatation upstream from the obstruction. The most common situation that presents in this fashion is aqueductal stenosis from either scarring or a benign tectal tumor. In children, obstructive hydrocephalus is first approached with the question of whether the obstruction can be removed or bypassed. Endoscopic third ventriculocisternostomy can be performed to bypass aqueductal obstruction with a high rate of success. At this stage in our ability to treat hydrocephalus, absorptive hydrocephalus causing dilatation of all four ventricles is almost always treated by an extracranial shunting device.

Children who have been treated with a third ventriculocisternostomy bypass need to be monitored into adulthood because there is risk of the ostomy closing many years after its initial placement. The true incidence of this is not yet known but is believed to be relatively low if the ostomy has survived several years. The adult who presents with a third ventriculocisternostomy bypass from childhood can be periodically evaluated by an imaging study such as magnetic resonance imaging with a cinematic gated flow study through the ostomy. If the ostomy has begun to occlude, the lateral and third ventricles may slowly begin to enlarge, even in the absence of overt clinical symptoms. Options for treatment at this time include endoscopic re-exploration for reconstruction of the ostomy or placement of a shunting device.

The management of the majority of adult hydrocephalus that was first treated in childhood revolves around the upkeep of extracranial CSF shunting devices. The utility of annual or biennial shunt checks for pediatric and adult patients is controversial. Our practice is to maintain a regimen of more or less annual shunt check evaluations in all our adult patients with shunts to maintain contact with the patient and the patient’s family, as well as to continually review the presentation and dangers of shunt malfunction. Where the upkeep of a shunting device in a child may concern issues of growth, such as ascertaining whether the extracranial portion of the shunt tubing is of adequate length during periods of growth or the ventricular catheter does not extrude from the ventricular system due to head growth, upkeep and management of shunting devices in adults are more straightforward. Shunt longevity is much longer in older children and adults than in infants, presumably due to issues of growth. In the adult, as in the child, the most common overall complication of shunt placement is a malfunction due to catheter or valve occlusion or fracture. ^, The next most common complication is shunt infection, which is generally seen in an early phase after implantation. Beyond that, issues of overdrainage and underdrainage may also need to be confronted.

Shunt malfunction in the adult, as generally seen in a child, presents with stereotypic symptoms more or less similar to past shunt malfunctions and consistent with the initial presentation of the hydrocephalus. In adulthood, cognitively high-functioning patients are often able to make the diagnosis on clinical grounds. The evaluation consists of the usual radiographic studies such as plain shunt radiographs and a head computed tomography scan after an adequate patient history has been taken and a physical examination has been performed. Oftentimes, the diagnosis of shunt malfunction is made due to either mechanical obstruction of the shunt tubing or enlargement of the ventricular system. In that situation, the shunt is explored operatively in the usual fashion.

We have generally opened the scalp incision first to determine the ventricular catheter patency versus malfunction of the components from the valve to the distal tubing. We then replace one portion of the shunt, either that in the brain or in the extracranial space, in its entirety. Our experience, like that of others, has shown no benefit to replacing the entire shunt versus revision of the affected component. Usually we replace a nonfunctioning valve with a valve of a similar type if the patient had done well for some time with that same valve. This may be different from the situation in the infant or child in whom, as the child grows, drainage needs may require a change to a valve type with other characteristics.

The advent of percutaneously programmable, differential pressure valves and programmable valves with fused anti-siphoning components ( Table 81.1 ) allows some flexibility in installing a valve that can provide dynamics similar to those of the one being replaced and retains the option of changing the shunting dynamics without operative intervention. With regard to shunt revision in the adult patient, generally we recommend replacing those components that are nonfunctional but not disturbing other components that appear to be functioning adequately.

Shunt infection in the adult patient almost always presents with some sign of systemic infection such as a fever, elevated serum leukocyte count, or frank meningitis, although the risk factors for infection, as well as many commonly used approaches to reduce infection rates in CSF shunts, remain insufficiently studied to determine significance. The severity of symptoms depends on the infectious agent and may range from headache with minimal other signs of infection (for relatively benign organisms such as Staphylococcus epidermidis or Corynebacterium ) to a more virulent picture of life-threatening meningitis (if the etiologic agent is Staphylococcus aureus or a gram-negative organism). A shunt infection needs to be treated as any foreign body infection would be in an adult, with removal of all infected foreign body material, which in general means removal of the entire shunt. Depending on the etiology of the hydrocephalus and the need for daily drainage, the shunt can be replaced with an external draining ventricular catheter or a lumbar drainage catheter for the period of the antibiotic treatment. Although the length of this period of temporary external drainage and antibiotic treatment can vary, most recommendations include at least several days of external drainage with negative CSF cultures before replacement of the shunting device in a new location, if possible. Depending on the terminus of the shunt, whether it is in the peritoneum, the pleura, or the cardiac atrium, the infection may spread or become loculated in those areas and require separate treatment. One other late complication of infection in the adult population that is more common than in the pediatric population is sclerosis of an absorbing surface from acute or chronic infection. In the peritoneum, this presents as a CSF pseudocyst or ascites, and in the pleural space this may present as CSF pleural effusion. In either situation, once recurrent infection is ruled out, the distal CSF catheter may be moved to another location or placed in the vascular tree through a large vein into the cardiac atrium where reabsorptive sclerosis is not present.

Shunt overdrainage and underdrainage in the adult can become a problem with age, in which presumably the brain may require lower pressure analogous to the normal-pressure hydrocephalus syndrome, which is described later. In that situation, the approach to the shunting dynamics is similar to that in the normal- or low-pressure hydrocephalus situation in that a trial of drainage at a low pressure may be appropriate or a programmable valve can be placed to allow percutaneous programming to lower pressures.

Our impression is that in patients whom we have followed from childhood into adulthood, complications seem to be reduced as children reach adulthood. The etiologic basis for this is unclear but may have to do with cessation of growth and reduced physical activity. Upkeep and care of the adult who was treated for hydrocephalus as a child are quite rewarding and relatively straightforward.

Evaluation and Management of Hydrocephalus Presenting in Adulthood

The causes of hydrocephalus presenting in adulthood are the same and yet different from hydrocephalus presenting in childhood. Intraventricular and subarachnoid blood from aneurysmal subarachnoid hemorrhage or hemorrhage from intraparenchymal vascular malformations can cause chronic hydrocephalus via a mechanism believed to be similar to that seen in the absorptive hydrocephalus of prematurity. Similarly, bacterial meningitis can also cause inflammation and presumably scarring in the subarachnoid space or at the arachnoid villi, which will cause an absorptive hydrocephalus. These entities present with four-ventricle enlargement, as in childhood. Obstructive lesions such as tectal tumors or even congenital scarring at the sylvian aqueduct can cause triventricular enlargement and obstructive hydrocephalus, which present in adulthood. The treatment of aqueductal stenosis in an adult, similar to that in a child, is third ventriculocisternostomy to bypass the obstruction. Also, intraventricular tumors or large tumors abutting the ventricles can sometimes cause hydrocephalus from what is believed to be a CSF hyperprotein state that may reduce villus absorption of CSF. These causes of hydrocephalus and its presentation mirror similar situations in childhood and present with symptoms and signs of elevated intracranial pressure.

Deciding When to Treat Hydrocephalus in the Adult

In adult hydrocephalus, symptoms are primarily due to inappropriate pressure within the ventricular system. Compression of brain tissue by ventricular enlargement may produce problems in gait due to stretching of subcortical white matter tracts. The rate of development of hydrocephalus differs significantly and affects which symptoms occur. Slow progression may lead to subtle changes in cognition; rapid progression leads to headache and loss of consciousness. These symptoms can include headache, vomiting, mental status change, gait changes, extraocular movement deficit, visual changes, or cognitive changes. Hydrocephalus presenting after aneurysmal subarachnoid hemorrhage is diagnosed in the ongoing evaluation and treatment of the lesion that has caused the bleeding. Similarly, hydrocephalus developing after meningitis is recognized as the meningitis is treated. However, the exact threshold for treatment of hydrocephalus in the adult can sometimes be difficult to define. Clearly, symptoms such as headache or cognitive changes which are interfering with life or lifestyle would constitute indications for initiating treatment, regardless of whether the hydrocephalus is from a process of reducing absorption or one of obstruction. Radiographic evidence of enlarging ventricles in the absence of overt symptoms may also constitute indications for intervention, although in many cases it is difficult to discern whether a process, such as an infection, has begun to cause global brain atrophy or whether inappropriate pressure within the ventricular system is causing ventricular enlargement.

Using our definition of hydrocephalus as an inappropriate amount of CSF under an inappropriate pressure, a measurement of CSF pressure either by lumbar puncture (in the setting of communicating hydrocephalus) or by direct ventricular access (in the setting of triventricular enlargement from obstruction) is diagnostic when combined with imaging. A secondary criterion when CSF pressure is measured by lumbar puncture or ventricular tap is to observe a reduction in presenting symptoms through a reduction in CSF pressure. This is the analogous situation to the large-volume CSF removal that is often performed for the diagnosis of normal-pressure hydrocephalus syndrome. The exact limits of what is considered normal CSF pressure in adults are unclear. Many would consider pressures as high as 20 cm H ₂ O in the lumbar space with the patient in a supine position to be within the normal range. However, sometimes symptoms of elevated intracranial pressure can be witnessed when pressure is measured to be as low as 15 to 18 cm H ₂ O, and those symptoms can be ameliorated by reduction in the CSF pressure to less than 10 or even less than 5 cm H ₂ O. This situation begins to establish a continuum of inappropriate CSF pressures in the adult that begins in the clearly abnormal range above 20 or 25 cm H ₂ O but can end quite squarely in the middle of what most would consider a normal-pressure value. Similarly, pressures as high as mid-20 cm H ₂ O can be asymptomatic, with no change in ventricular size. Whether this defines compensated hydrocephalus or simply a variant of normal is unclear.

Regardless, when symptoms referable to elevated intracranial pressure in the presence of an enlarged ventricular space can be ameliorated or reduced by drainage of CSF, there exists a clear indication for treatment of hydrocephalus. In the absence of a pressure measurement, symptoms referable to elevated intracranial pressure that coincide with enlarged or enlarging ventricles also call for treatment. Precise indications for intervention are sometimes not possible, even considering ventricular size, CSF pressure, and the effect of drainage of CSF. Each case must be individually evaluated by the treating neurosurgeon. The goal of treatment is to restore a CSF pressure and dynamic that maximally reduces symptoms while maintaining the pressures within a range appropriate for cerebral perfusion, and which reduces ventricular size to a normal range.

Choices of Techniques for Treating Hydrocephalus

The general approach to an individual presenting with symptomatic hydrocephalus or radiographic enlargement of ventricles depends on the etiology of the hydrocephalus. In practical terms, obstructive hydrocephalus should generally be considered for a bypass procedure or removal of obstruction before resorting to extracranial shunting. Hydrocephalus due to absorption or obstruction of the subarachnoid space with four-ventricle enlargement should be approached with extracranial shunting, primarily. Aqueductal stenosis in a center where expertise is available should be treated by a third ventriculocisternostomy, which may avoid the need for permanently implanted hardware. Still, extracranial shunting is certainly an option that will adequately treat this type of hydrocephalus. Extracranial shunting for obstruction or for four-ventricle hydrocephalus provides the additional possibility of fine-tuning CSF drainage dynamics and pressures that a bypass procedure cannot accomplish.