General Shunt Complications
Endocrine sequelae and infertility
Many children experience endocrine problems related to hydrocephalus.
- Growth hormone: Growth hormone deficiency can be a sequel of intracranial hypertension (13) or of treatments like tumor surgery or irradiation.
- Diabetes insipidus: Diabetes insipidus is a rare complication of ETV (53).
- Infertility: Infertility is a common sequel among patients with pediatric hydrocephalus that can be caused by neuroendocrine sequelae or other issues, including abdominal lesions or surgery. Gupta noted that fertility was lower when hydrocephalus began during infancy (20). Infertility may follow precocious puberty, which is thought to result from increased ICP (38). In the experience of the author and colleagues, among 220 female patients followed for pediatric hydrocephalus and older than 20 years, only 32 (14.5%) had one child or more (52).
- Obesity: Obesity is a significant concern in children with neurological sequelae and can result from lower energy consumption because of motor deficit or from deregulation of the intake/consumption balance caused by hypothalamic damage (48). In hydrocephalic patients, obesity can increase physical dependence on third persons, cause pseudotumor cerebri through raised venous pressure, and make shunt revisions more hazardous. Preventing obesity through nutritional education and encouraging participation in sports are important in the management of these patients.
- Vision: Visual impairment in patients with hydrocephalus is generally the result of initial or subsequent episodes of increased ICP, or of oculomotor disturbance causing functional amblyopia. These impairments affect up to 83% of hydrocephalic children (3). In a systematic review of pediatric cases, Persson et al. found decreased visual acuity in 33% and optic atrophy in 22% (36). Sensory sequelae, visual as well as auditory, can also result from meningitis.
- Greatest impairment occurs in congenital and postinfectious hydrocephalus: Many adults treated for pediatric hydrocephalus have mental delay. Intellectual outcome is mostly conditioned by the cause of hydrocephalus (11). Congenital hydrocephalus and post-meningitis hydrocephalus are associated with the worst intellectual outcomes.
- Performance IQ is worse than verbal IQ: Performance IQ is generally more affected than verbal IQ (27). Intellectual outcome is also impacted by shunt complications like infection (47) and epilepsy (29).
- Number of revisions is not related to cognition: A large number of shunt revisions in a given patient does not appear to be linked with mental delay. It could, in fact, reflect the level of care with which the patient is followed.
- 2% per year of patients with shunts have seizures: Epilepsy can be the consequence of the causal disease as well as a complication of surgery. The cumulative incidence of epilepsy in patients with shunts has been estimated as high as 2% per year (37).
- 30% prevalence of epilepsy present in nontumoral patients with hydrocephalus: The overall prevalence of epilepsy in patients with nontumoral hydrocephalus was evaluated at 30% (6). In the experience of the author and colleagues, 14% of the patients had epilepsy from the time of diagnosis of hydrocephalus, and the cumulative incidence of new epilepsy was 4% after 10 years and 9% after 20 years (see figure below).
- Epilepsy rate is highest with history of infections: The incidence of epilepsy is higher after shunt infection (28).
- Epilepsy is associated with poor functional outcome: Epilepsy in hydrocephalic patients is associated with behavioral problems, a poor intellectual outcome, and diminished quality of life (23, 29).
- Cumulative incidence of epilepsy in shunted patients
- Headaches common: Headache and migraine are much more common in patients with shunts than has been traditionally thought. In a systematic survey, Rekate and Kranz found headache reported by 29% of children and 44% of adults with shunts (39). Apart from shunt underdrainage and overdrainage, pain can be caused by migraine, visual adaptive headache, tension headache, chronic daily headache caused by abuse of pain-killers, and scarring over the valve. All these diagnoses should be considered when the clinical-radiological picture is unconvincing, before embarking on invasive procedures such as pressure monitoring or shunt revision.
- Shunt degradation: Catheter degradation occurs over long periods of time, due to slow-burning biological reactions to silicon, which is oxidized into silica (22), and the release of barium from the shunt, which is replaced by calcium. This degradation can lead to subcutaneous pseudotumoral masses, with episodes of inflammation, ossification of the catheter tract, and often rupture of the catheter. Acute inflammation can be treated by local percutaneous anti-inflammatory drugs, but all these complications are best prevented by selecting systems with striped catheters low in barium.
- Progressive myelopathy: Progressive myelopathy caused by meningeal thickening occurs with long delays in patients shunted for post-meningitis hydrocephalus and manifests as progressive tetraparesis with falls and increased dependence. In already severely handicapped patients, this slow degradation can be unnoticed, so the real incidence is likely underestimated (49). There is deterioration over time with plateaus of unpredictable duration; surgical osteodural decompression can stabilize, but can also aggravate the patient’s symptoms irreversibly. Consequently, the decision to operate or not is often agonizing.
- Secondary Chiari malformation: Chiari malformation can be induced classically by lumbar drainage (14) but can also result from chronic overdrainage by a ventricular shunt (10). The pathogenesis is unclear, and some cases may in fact represent chronic tonsillar herniation caused by sustained intracranial hypertension. Management includes shunt revision, upgrading of the shunt resistance, posterior fossa decompression, and expansion cranioplasty.
Late shunt infection
- 13% of shunt infections occur late: Shunt infection is generally caused by intraoperative contamination and occurs usually in days or weeks after surgery. In rare cases, infection can be much more delayed, and other causes of infection can be identified, such as blood-borne contamination, traumatic wound over the shunt tract, abdominal surgery, abdominal sepsis, and bowel perforation (figure below). Some authors (43) have found that 13% of shunt infections occurred more than a year after surgery, often unrelated to it.
- Nonlocalizing symptoms of infection: In an adult with a shunt, especially a severely handicapped one, shunt infection can be heralded by altered general status or even cause sudden death (9). Basically, any infectious event in a patient with a shunt should raise the suspicion of shunt infection, especially if shunt surgery was performed during the preceding 6 months.
- Cumulative incidence of shunt infection: Although most cases occur within a month after shunt surgery, new cases continue to occur many years after.
- Headache and dizziness on standing: Chronic overdrainage is the consequence of mismatch between the shunt’s mechanics, which have to be kept simple, and human physiology, of which much is unknown. It is a particular problem for patients with pressure-regulated shunts. The manifestations are headache and dizziness when standing.
- Significant functional disability: Although symptoms are usually transient, they may cause severe functional impairment in some cases.
- Proximal catheter occlusion: Overdrainage has been blamed for causing proximal catheter occlusion (16).
- Dural enhancement on MRI: Imaging can show diffuse dural contrast uptake, thickening of the calvaria, and slit ventricles. Although such dural enhancement has no consequences, it may cause confusion in tumor cases because it can be mistaken for tumor dissemination.
- Difficult diagnosis: Symptoms are nonspecific, and many differential diagnoses need to be considered, in particular shunt hypodrainage, fatigue caused by depression, endocrine failure, and abuse of pain-killers.
- ICP monitoring helpful: ICP monitoring is an important step in the management of these patients. Results can be falsely negative in patients with intermittent symptoms. If results are normal, monitoring may need to be repeated when the patient is clearly symptomatic.
- Increase resistance of shunt valve to treat: Treatment options include upgrading the valve setting (if adjustable), switching to a flow-regulated valve or a low-flow valve, and expansion cranioplasty.
Ventriculoperitoneal Shunt Complications
Peritoneal pseudocyst and ascites
- Ascites and pseudocyst both have abdominal symptoms: CSF accumulation in the peritoneum comes in two forms: ascites, in which the whole peritoneum is incompetent in resorbing the CSF, and pseudocyst, which is a localized accumulation while the rest of the peritoneum remains competent. In both cases, the patient presents with abdominal swelling, discomfort, intestinal transit impairment, and vomiting.
- Suspect pseudocyst in nonconversant patients with distal obstruction: A peritoneal pseudocyst has to be carefully sought in severely handicapped patients referred for suspected shunt obstruction, because it is easily overlooked in such patients. Such obstruction in these patients can be initially misdiagnosed as constipation or bezoar.
- 50% of pseudocysts are due to subacute infections: In roughly half of cases, pseudocyst is caused by subacute infection (4), and suspicion of sepsis should be high if the patient has been reoperated recently. In such cases, it is prudent to externalize the shunt, and, according to fluid studies, either treat as a shunt infection (antibiotics followed by insertion of a completely new shunt) or reimplant a new peritoneal catheter.
- Abdomen can usually be reused after pseudocyst treated: The peritoneum can generally be reused, at some distance from the previous site. However, in ascites, the whole peritoneum is incompetent, and the shunt’s distal recipient site must be moved, generally to the atrium (45).
- Rare occurrence: Bowel perforation by a peritoneal catheter is a rare occurrence. Although historically associated primarily with spring-reinforced catheters, it can occur with any peritoneal catheter. The incidence in the shunted population has been estimated at 0.1%/year (46). This complication, although rare, suggests that useless shunts should be removed whenever possible.
- Most patients present with nonspecific signs of shunt malfunction: Although bowel perforation is an unmistakable diagnosis when the catheter protrudes through the anus or any other natural orifice (15, 34), most patients have a more nonspecific and misleading presentation. Patients present with signs and symptoms suggesting shunt malfunction, often without infectious signs. Attention should be paid to the predominance of digestive symptoms like vomiting and abdominal pain, and blood studies (white cell count and CRP assay) always should be performed before embarking on a shunt revision.
- Meningitis possible: Perforation causes multibacterial contamination of the catheter, with the potential of leading to fatal meningitis if not recognized (9).
- Chronic inflammation surround a distal catheter: Perforation can also result in a chronic inflammation of the tissues surrounding the catheter. This inflammation can represent a mechanism for rejection of the infected foreign body (15).
- Externalize shunt and treat infection: The correct approach should be to externalize the shunt, refrain from laparotomy, treat with antibiotics, and insert a new peritoneal shunt at some distance from the previous site.
- Shunt origin is first consideration in case of acute abdomen: As a rule, an abdominal emergency in a patient with a shunt is due to the shunt until proved otherwise. Although the identification of a small pool of CSF in the lower peritoneal cavity by ultrasonography is a normal finding in shunted patients with patent shunts, it does not eliminate the shunt as the source of symptoms in a patient with an acute abdomen.
- If peritonitis shunt externalized: As a general rule, abdominal sepsis requires removal of the shunt with temporary external drainage, and eventual insertion of a new shunt into the peritoneum will be the preferred solution whenever possible.
- In case of peritonitis, referral to neurosurgeon mandatory. The first question is whether the CSF is contaminated. Clinical examination and CSF samples from the shunt reservoir and lumbar puncture will help decide on either externalization of the peritoneal catheter or total removal of the shunt and insertion of an external drain. After cure of the abdominal infection and, if present, of the meningitis, a new shunt should be inserted that follows a totally new track, ideally to the peritoneum, or to the atrium if the abdomen is not available. It is wise to anticipate the need for conversion to an atrial shunt and to check the jugular vein with ultrasound to determine if it can accept such a shunt.
- Varying etiologies for peritonitis: Peritonitis can occur as a complication of hollow viscus perforation (appendix, fallopian tube, gallbladder, Meckel’s diverticulum), or spontaneously by hematogeneous or transmural bacterial migration. In rare observations, the role of a preexisting peritoneal collection, secondarily contaminated, has been documented (19).
- Other etiologies of acute abdomen are treated as usual: Common abdominal emergencies like appendicitis, invagination, hernias, or pyloric stenosis do not interfere with the shunt as long as the peritoneum is not contaminated. Whether open or laparoscopic, abdominal surgeries should be performed as usual and do not require the presence of a neurosurgeon.
Abdominal surgery and laparoscopic surgery
Neurosurgeons are often anxious about shunt contamination during abdominal surgery.
- Communication between treating services mandatory: Laparoscopic surgery has become very popular among visceral surgeons; this trend may collide with the tendency of neurosurgeons to insert peritoneal catheters through an umbilical incision, with potential conflict of interest. Neurosurgeons must inform the patient and the treating surgeon of the presence of the catheter, usually at the upper margin of the umbilicus, leaving the rest of the circumference available for laparoscopic surgery.
- 5% incidence of peritoneal contamination during percutaneous gastrostomy: Bui et al. estimated the risk of contamination during percutaneous gastrostomy to be approximately 5%, which is comparable to the risk associated with shunt surgery (7).
- Low rate of infection with urological procedures: Enterocystoplasty, appendico-vesicostomy, and other operations on a chronically contaminated urinary tract are commonly performed in handicapped patients, especially those with myelomeningocele. However, the infection rate associated with these procedures is unexpectedly low, suggesting efficient natural defenses (47).
- Anticipate possible pregnancy in females with shunts: Shunt series as well as any X-ray based imaging should be performed sparingly in sexually active female patients.
- Pregnancy not contraindicated: Shunts by themselves should not be considered an obstacle to pregnancy, delivery, or cesarean section if needed. Only peridural anesthesia requires some dose adjustment because the intrathecal volume is collapsed in patients with shunts.
- Genetic counseling considered for fertile women: Before women become pregnant, questions should be raised on the genetic nature of the hydrocephalus (mostly to reassure the patient), the teratogenicity of drugs (especially antiepileptic drugs), and associated conditions (like urinary problems in spina bifida), which can impact on or be impacted by pregnancy. Ideally, an interview should be held at the time of adolescence as part of the patient’s education. Physicians should be proactive in initiating this discussion since it is rarely started by the patient but it is often on their mind.
- Headaches common during pregnancy: During pregnancy, fluid imbalance and hormonal modifications can cause headache (33), with the double risk of false alert regarding the shunt and of ignoring shunt malfunction. Close dialogue between obstetricians and neurosurgeons is necessary to evaluate each case.
Complications of Atrial Shunts
- Higher incidence of fatal complications: Atrial catheters are no longer used as a first-line standard procedure. Historically, it became clear that peritoneal shunts had a clear advantage over atrial shunts when Mazza et al. compared two series of shunts. and showed that, although the complication rates were the same in both groups, the complications themselves were more often fatal with atrial shunts (32).
- Emboli causing death and cor pulmonale: A particular complication of atrial shunts is sudden death, caused by massive acute emboli (30) or chronic emboli with pulmonary heart failure (8).
- Bacteremia a special consideration: Atrial catheters can be contaminated by bacteria. A form of shunt infection specific of atrial shunts is shunt nephritis, which is caused by accumulation of immune complexes in the kidney during chronic infection (18). Patients with atrial shunts and/or their physicians should be informed of this eventuality. The risk of bacteremia during dental care should also be taken into consideration, and antibioprophylaxis during dental care has been proposed (1).
- Revision more problematic: Shunt revision of atrial shunts is more complicated technically; catheter length cannot anticipate statuary growth, requiring reoperation for catheter lengthening in children, and only two internal jugular veins are available. Often, when an atrial shunt is revised, the best choice is to replace it with a peritoneal catheter.
Late ETV occlusion
- Most failures of ETV early: When the patient has been treated with endoscopy, guidelines for long-term follow-up are scarce. ETV occlusion generally occurs early; obstruction rarely occurs after 3 years postoperatively.
- Potentially fatal complication: If neglected, intracranial hypertension can have very severe consequences, including disability and death.
- Unclear etiology of late failures: The pathophysiology of ETV occlusion is unclear. Theoretically, the flow of CSF through the ETV is supposed to maintain patency. The fact that occlusion occurs supposes fluctuations in CSF flow, allowing scarring to develop. In postmortem studies, histology has shown thick scar tissue, lending support to the hypothesis that the ETV had been occluded for some time before symptoms occurred (17). However, understanding how a patient can survive for long periods with an occluded ETV remains perplexing.