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Abstract

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

Objective: To report frequency and type of complications, and outcome in dogs with severe neurologic signs secondary to internal, suspected obstructive hydrocephalus treated by ventriculoperitoneal (VP) shunting.

Study Design: Case series.

Animals: Dogs (n=14).

Methods: Medical records (2001–2006) was reviewed for dogs that had VP shunting. Inclusion criteria were complete medical record, progressive forebrain signs unresponsive to medical treatment, normal metabolic profile, negative antibody titers and/or cerebrospinal PCR for Toxoplasma gondii, Neospora caninum, and canine distemper virus, magnetic resonance images of the brain, confirmed diagnosis of VP shunting, and follow-up information.

Results: Hydrocephalus was idiopathic in 5 dogs and acquired (interventricular tumors, intraventricular hemorrhage, inflammatory disease) in 9 dogs. Four dogs developed complications 1 week to 18 months postoperatively, including ventricular catheter migration, infection, shunt under-drainage, kinking of the peritoneal catheter, valve fracture, and abdominal skin necrosis. Three of these dogs had 1 or more successful revision surgeries and 1 dog was successfully treated with antibiotics. All, but 1 dog, were discharged within 1 week of surgery, and had substantial neurologic improvement. Median survival time for all dogs was 320 days (1–2340 days), for dogs with idiopathic hydrocephalus, 274 (60–420) days and for dogs with secondary hydrocephalus, 365 (1–2340) days.

Conclusions: VP shunting was successful in relieving neurologic signs in most dogs and postoperative complications occurred in 29%, but were resolved medically or surgically.

Hydrocephalus is characterized by abnormal accumulation of cerebrospinal fluid (CSF) within the cranial cavity with consequent dilation of the ventricular system or subarachnoid space.1–4 Hydrocephalus has been classified in different ways according to its anatomic relationship with the ventricular system (internal or external), to the underlying pathologic process and cause (compensatory or obstructive; congenital, idiopathic, or acquired) and according to pressure differences (normotensive, hypertensive).5,6

Knowledge of the pathologic process in hydrocephalus based on human and experimental studies is surprisingly low, and the adaptive brain response to hydrocephalus is not fully understood.7 Adaptive mechanisms may include hydrodynamic brain compliance, vascular, metabolic, and neuronal connectivity factors, which if understood, may be important in the treatment of hydrocephalus.7 Different animal models of obstructive hydrocephalus have studied,8–13 and seemingly many pathologic mechanisms operate concurrently after the induction of hydrocephalus.

Mechanisms have been classified as primary (occurring during the early stages of hydrocephalus) and secondary (usually appearing later during the progression of ventriculomegaly).14 Primary mechanisms include compression and stretch produced by ventricular expansion. With the worsening of the ventriculomegaly interstitial edema and ischemia develop in the periventricular region and in the cortical grey matter.14 Loss of ependymal lining, periventricular diverticula, and cleft formation have been observed together with disturbances in blood–brain barrier in this stage.14,15 Secondary pathologic mechanisms in the chronic form of hydrocephalus include cell death, gliosis, altered cell metabolism in the white matter, altered connectivity and neurotoxicity. Pathologic cytologic changes are seen in the cortical areas as well as in the white matter especially in the periventricular region.7,15

There are medical and surgical therapeutic options for hydrocephalus. Usually medical treatment does not provide long-term resolution of the clinical signs1,16 whereas, surgical treatment is an effective way of shunting the excessive amount of CSF from the cerebral ventricles into a body cavity.1,16,17 The most commonly used body cavities include the peritoneum, pleural space, and right atrium.16,18

The aims of surgical treatment of hydrocephalus are to reduce the intracranial pressure, ameliorate the patient's neurologic status, and to minimize the damage to the brain parenchyma caused by excessive accumulation of CSF within the ventricular system. These goals are achieved by draining CSF from the ventricular system to an absorption site by means of a shunting system.19 People with obstructive hydrocephalus in which CSF pathways cannot be re-established by removal of the offending lesion undergo a CSF diversionary procedure.6 Nearly 80% of people that are shunted improve, regardless of the system used20; however, the probability of shunt failure over 12 years in children can be as high as 80%.21 Fifty percent of shunt failure has also been reported within the first year of placement in children.22 In people, complications after ventricular shunting are very common and have been divided into mechanical failure, infection, and overdrainage.23

The largest veterinary study of the surgical treatment of hydrocephalus, reported successful results in 13 of 21 dogs that had ventriculo-atrial shunting.17 Another study reported favorable outcome in 1 of 4 dogs that had ventriculo-atrial shunting.24 In these 2 studies of ventriculo-atrial shunting complications included anesthetic death, heart failure, and catheter displacement. Limited information is available on complications and outcome of dogs that have ventriculoperitoneal (VP) shunting for hydrocephalus.1,17,25–27 Thus our objectives were to describe our surgical procedure for VP shunting in dogs, and to report the frequency and type of complications associated with VP shunting, and to assess outcome.

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

Medical records (September 2001–September 2006) were searched for dogs that had VP shunting. Inclusion criteria were complete medical record, presence of progressive forebrain signs unresponsive to medical treatment, normal hematologic and metabolic profiles, negative antibody titers and/or CSF PCR for Toxoplasma gondii, Neospora caninum, and canine distemper virus, magnetic resonance imaging (MRI) of the brain consistent with internal, suspected obstructive hydrocephalus, VP shunting, and follow-up until time of death (where applicable). Follow-up included, 4 week postoperative re-check at our hospital, repeated brain MRI when possible, and phone call updates with owners.

For this study, MRI features that allowed a diagnosis of internal, suspected obstructive hydrocephalus included presence of distended lateral ventricles with periventricular edema, the presence of transtentorial or foramen magnum herniation and subjective evaluation of ventricular volume compared with breed matched dogs admitted to our hospital that had MRI scan of the brain for nonneurologic conditions. MR images of the brain were acquired (1.5 T Sigma Echospeed System, General Electric Medical System, Milwaukee, WI). T2-weighted (T2W), T1-weighted (T1W) and T1-weighted images acquired after intravenous (IV) administration of paramagnetic contrast medium (0.1 mL/kg; gadopentate 469.01 mg/mL) in at least 1 plane in all dogs. Gradient echo and FLAIR images were also obtained at the radiologist's discretion.

For the surgical procedure, dogs were either not premedicated or administered methadone (0.2–0.3 mg/kg intramuscularly) and anesthesia was induced with IV propofol and maintained either with IV propofol infusion and oxygen delivered via endotracheal tube or with sevoflurane in oxygen.

A Kaplan–Meier survival plot was performed; 1 dog lost to follow-up was censored at its last known survival time for the data analysis.

VP Shunting Equipment

Elements used for the VP shunting system included an integral snap assembly ventriculostomy reservoir dome, a ventricular catheter with stainless-steel stylet, a plastic secure tab, an integral peritoneal catheter and a subcutaneous catheter passer (Medronic PS Medical Snap Shunt Assemblies, Goleta, CA). In all dogs a proximal, low-pressure, CSF-flow control valve was used (Medronic PS Medical Snap Shunt Assemblies). These valves are fabricated of dissimilar materials, polypropylene and silicone elastomer, reducing the chance of valve sticking and deformation. Also the simple, uniform flow path ensured optimum valve performance. The opening pressure for this low-pressure valve is 30–45±25 mmH2O.

Surgical Technique

Dogs were positioned in sternal recumbency. The dorsal surface of the cranial cervical area, cranium, and face were clipped and aseptically prepared for surgery. A 4 in. square area of the right/left lateral abdomen just caudal to the last rib was also clipped and prepared, as was a 2.5 in. wide strip joining the cranial and the abdominal areas on the right and or left side of the dog depending on the side of the shunting. A small rostrotentorial approach28 was used to reach the cranium and a hole in the mid-caudal parietal bone just lateral to the sagittal crest created with a burr in a pneumatic drill. The ventral aspect of the burr hole was opened with a small curette to identify the dura mater. The diameter of the hole was large enough to comfortably accommodate the ventricular catheter. A second smaller, burr hole was made caudal to this. Monofilament nonabsorbable suture material was passed from the small to the large burr hole; this suture was used to secure the ventricular catheter to the cranium in a later stage of the surgery.

Attention was then focused on peritoneal catheter placement and the cranial site was covered with moist sterile gauze. A small flank approach was performed caudal to the last rib; the external abdominal oblique, internal abdominal oblique and transverse abdominal muscles were dissected according to their fiber direction. The transverse fascia and the peritoneum were then incised, and ∼4 in. of the peritoneal catheter was inserted in the peritoneal cavity (for a 15 kg dog) and sutured to the abdominal wall. The length of peritoneal catheter inserted was adjusted based on body size. A purse-string suture was placed around the abdominal wall incision using a monofilament nonabsorbable suture material and the extraperitoneal portion of the distal catheter was secured to it with a Chinese finger-trap suture. The catheter was then looped under the superficial fascia and the subcutaneous catheter introducer was used to tunnel the distal catheter under the skin from the abdominal site to the cranial incision.

Ventricular catheter insertion was facilitated using a 21 G needle to perforate the meninges. The ventricular catheter was introduced into the lateral ventricle with an ∼30° angle and directed slightly cranially. The precise angle of insertion and depth was assessed before surgery based on the dog's MR images. Once the catheter was positioned in the ventricle, the stylet was removed and CSF flow confirmed. A hemostat was used temporarily to clamp the ventricular catheter to minimize loss of CSF while the valve was connected. The proximal catheter was secured to the cranium using the plastic tab and with a Chinese finger-trap suture. The fascia of the temporalis muscle was reapposed at the sagittal crest. The proximal catheter was looped in the cranial cervical area and the end was attached to the valve. CSF was observed to flow into the valve and the incision closed.

One or both lateral ventricles were shunted according to the dog's brain anatomy and underlying pathology. In dogs that had shunting of both lateral ventricles, a modified valve was used that had 2 entry ports and 1 exit. In this way, only 1 distal (peritoneal) catheter needed to be placed. Amoxicillin clavulanic acid (20 mg/kg IV) was injected 20 minutes before surgery and every 2 hours during the procedure and continued postoperatively in combination with metronidazole (10 mg/kg orally) for 2 weeks. Postoperative pain checks were performed every 2 hours during the first 48 postoperative hours and discomfort/pain was managed by opioid and/or paracetamol administration. All dogs were administered prednisolone (0.5–1 mg/kg daily or every other day) after surgery.

RESULTS

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

Case Histories

Of 16 dogs that had VP shunting, 14 met the inclusion criteria. Breeds were Boxer (4), Golden Retriever (3), Collies (2) and 1 each of Labrador Retriever, Jack Russell Terrier, Staffordshire Bull Terrier, and Doberman Pincher. Mean age at admission was 5 years (range, 0.5–11 years). Ten dogs were male (2 intact, 8 neutered) and 4 were female (1 intact, 3 spayed). The most common clinical signs on admission were obtunded mentation (10 dogs) and seizures (8). Other clinical signs included reduced or absent menace in both eyes (6 dogs), reduced postural reactions (6), and neck pain (1).

In all dogs, MRI consistently revealed distended lateral ventricles with various degrees of periventricular edema and compression of the caudal fossa structures. Five dogs were diagnosed with idiopathic hydrocephalus, because an underlying cause for obstructive hydrocephalus was not identified with MRI and CSF analysis. Acquired hydrocephalus was diagnosed in 9 dogs; 8 had a mass lesion (suspect neoplasia) either within the ventricular system or a lesion causing mass effect and secondary obstruction of the ventricular system, and 1 dog had a multifocal central nervous system inflammatory disease. Prednisolone (0.5–1 mg/kg daily) was administered to all dogs for a variable period (range, 2–42 days) before surgery. Dogs either failed to show an improvement of neurologic signs or had an initial response followed by deterioration. Ten dogs were also administered phenobarbitone (2–4 mg/kg twice daily) alone or in combination with potassium bromide (30 mg/kg daily) as anticonvulsant treatment.

Management

Ten dogs had unilateral VP shunting (5 right, 5 left) and 4 dogs had bilateral VP shunting. In 3 dogs, intraoperative biopsy of the mass confirmed neoplasia (ependymoma, choroid plexus carcinoma, poorly differentiated glioma). Two dogs had a course of hypofractionated radiotherapy using a protocol modified from Brearley et al.29

Surgery was uneventful in all dogs. All but 1 dog were discharged within 1 week of surgery and had marked neurologic improvement (consisting of a brighter mentation, ability to ambulate unassisted, ability to eat and drink unassisted, urinary and fecal continence, loss of the compulsive behavior) based on a repeated neurologic examination by a board-certified neurologist, and regained a good quality of life (as assessed by the owner and consisting of responding to his/her name and basic commands, ability to take light exercise and being house trained). Seven of 9 dogs with acquired hydrocephalus had repeat MRI (1 week to 18 months); 5 had >1 repeated MRI. In 5 dogs repeat MRI showed improvement of the hydrocephalus (Figs 1–4); however, in 4 of these dogs MRI also revealed an increase in size of the intraventricular mass. In 1 dog, the mass was smaller on the follow-up MRIs. MRI was repeated because of deterioration of forebrain signs 1 week postoperatively in 1 dog, and, respectively, 7 and 8 months, and 17 and 18 months postoperatively in 2 dogs.

image

Figure 1.  Magnetic resonance of transverse T2-weighted FLAIR image of the brain at the level of the rostral mesencephalon. Lateral ventricles are dilated and a hyperintense lesion is also present at the level of the mesencephalic aqueduct.

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image

Figure 2.  Magnetic resonance of transverse T2-weighted FLAIR image of the brain at the level of the rostral mesencephalon of the dog in Fig 1, 3 months postoperatively. The hydrocephalus has resolved. The ventricular portion of the VP shunt is seen entering the left lateral ventricle.

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image

Figure 3.  Magnetic resonance of midsagittal T2-weighted image of the brain. Lateral and third ventricles are distended. There is caudal trans tentorial herniation and cervical spinal cord hyperintensity likely suggesting syrinx formation. An isointense mass lesion is seen in the lateral ventricles.

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Figure 4.  Magnetic resonance of midsagittal T2-weighted image of the brain of the dog in Fig 3, 3 months postoperatively. There is complete resolution of the hydrocephalus and forming syrinx. The isointense intraventricular mass lesion is still visible in the lateral ventricles.

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Complications

Four dogs developed complications 1 week to 18 months postoperatively; 3 dogs had >1 complication. Dogs that developed complications had a sudden (<48 hours) deterioration of forebrain signs and were readmitted for further investigations. This included collection of CSF from the reservoir and flush of the shunting system; radiographs of the shunt in 1 dog; and brain MRI in 3 dogs. Complications included ventricular catheter migration (near the ventricular mass) at 7 months in 1 dog (Figs 5 and 6); infection at 7 and 17 months in 2 dogs (Figs 7 and 8); shunt under-drainage at 1 week, 8 and 18 months in 3 dogs; kinking of the peritoneal catheter at 7 months in 1 dog; valve fracture at 8 months in 1 dog; and necrosis of a small portion of the skin above the site of peritoneal catheter insertion at 9 months in 1 dog. In both dogs that developed infection, Staphylococcus spp. was cultured from a CSF sample; both dogs responded to IV and oral amoxicillin and clavulanic acid antibiotic treatment (20 mg/kg twice daily for 4 weeks), selected based on antimicrobial culture and susceptibility results. Additional diagnostic tests performed in these 2 dogs (chest and abdominal imaging and urinary culture) failed to identify other sites/sources of infection. Three dogs had revision surgery that included ventricular catheter replacement (3 dogs), valve replacement (1), peritoneal catheter replacement (1), and removal of necrotic abdominal skin (1). All 4 dogs responded to revision surgery or medical treatment.

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Figure 5.  Magnetic resonance of transverse T2-weighted FLAIR image of the brain at the level of the diencephalon. Lateral ventricles are dilated and a large, hyperintense, mass lesion is present in the right lateral ventricle.

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image

Figure 6.  Magnetic resonance of transverse T2-weighted image of the brain at the level of the rostral mesencephalon of the dog in Fig 5, 1 week postoperatively. The tip of the ventricular portion of the VP shunt is embedded in the ventricular mass. Right-sided mass effect on the mesencephalon is present. The VP shunt is seen entering through the right parietal bone. In this dog the VP shunt was under draining.

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image

Figure 7.  Magnetic resonance of transverse T2-weighted FLAIR image of the brain at the level of the diencephalon. Lateral ventricles are dilated and asymmetric. Third ventricle is also distended. Periventricular white matter hyperintensities are seen.

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image

Figure 8.  Magnetic resonance of transverse T2-weighted FLAIR image of the brain at the level of the rostral mesencephalon of the dog in Fig 7, 17 months postoperatively. The dilation of the lateral ventricles is marked. The CSF signal is abnormal and failed to suppress on this sequence. Extensive hyperintensity is located within the internal capsule and corona radiata and surrounding the VP shunt. The ventricular portion of the VP shunt is seen entering through the left parietal bone. CSF culture in this dog was positive for Staphylococcus spp.

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Outcome

Of 5 dogs with idiopathic hydrocephalus, 1 was euthanatized because of relapse of clinical signs at 9 months; 1 was euthanatized because of renal failure at 12 months; 1 was in good health at 14 months and then lost to follow-up; and 2 were euthanatized at owner request because of persistent (unchanged pattern) seizure activity, respectively, 2 and 4 months after surgery. In these 2 dogs, the shunting system was checked for patency by retrieving CSF from the reservoir and flushing; no malfunctions were identified.

Of 9 dogs with acquired hydrocephalus, 1 dog was euthanatized 24 hours after surgery because of lack of improvement. This dog had a parenchymal mass causing obstructive hydrocephalus and increased intracranial pressure diagnosed 42 days before surgery and was initially treated with corticosteroids. On readmission, the dog was comatose and MRI revealed worsening of the hydrocephalus and of the mass effect on the caudal fossa structures. The dog remained comatose despite VP shunt surgery. Seven dogs were euthanatized because of worsening of neurologic signs 1–19 months postoperatively; 5 had repeat MRI and in 4, the mass was larger. In 1 dog, MRI revealed recurrence of a multifocal inflammatory CNS disease and on necropsy, nonsuppurative encephalitis was confirmed. The dog that did not have repeat MRI was euthanatized on owner request 1 month postoperatively because of persistent seizures.

One dog was euthanatized because of cardiac failure 10 months postoperatively. In this dog MRI was repeated at 3 and 6 months postoperatively as part of a check-up and at 7 and 8 months because of neurologic deterioration. The 3 and 6 month MRI revealed an unchanged ventricular mass and resolution of the hydrocephalus. The 7-month MRI revealed migration of the ventricular catheter toward the ventricular mass and thickening of the catheter tip. These findings were confirmed intraoperatively. CSF culture revealed heavy growth of Staphylococcus spp. The VP shunt was replaced and the dog was administered amoxicillin and clavulanic acid, and responded well. MRI repeated at 8 months revealed recurrence of the hydrocephalus and enlargement of the ventricular mass. The ventricular catheter was again replaced; CSF microbial culture was negative. The dog had good clinical improvement and was discharged 5 days postoperatively.

One dog was still alive at the time of writing 6.5 years postoperatively; MRI was repeated in this dog at 6 and 18 months, and confirmed reduction of the hydrocephalus as well as reduction in size of the intraventricular lesion.

Median survival time for all dogs was 320 days (95% CI: 61–517 days). Thirteen dogs were alive at 1 month postoperatively, 9 dogs were alive at 3 months, 6 at 12 months, and 2 at 18 months (Fig 9).

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Figure 9.  Kaplan–Meier survival plot of the 14 dogs with VP shunting (looking at all causes of death). Patients lost to follow-up were censored at their last known survival time for the data analysis.

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DISCUSSION

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

Eleven dogs were large breed, 2 were medium, and 1 was a small breed. Three of the 5 dogs with idiopathic hydrocephalus were large breed dogs, which is not typical for hydrocephalus. In a retrospective study of 564 dogs, 11 breeds were considered at risk for congenital hydrocephalus including 8 toy breeds.30 A necropsy study15 of 20 juvenile dogs diagnosed with congenital hydrocephalus, however, also had an atypical breed distribution that included 16 medium and large breed dogs. The reason for the unusual breed distribution in our case series is speculative. Young, toy-breed dogs that have progressive, forebrain neurologic signs are likely to be diagnosed with hydrocephalus and may be managed medically or euthanatized because of guarded prognosis4,16 without seeking specialist opinion. Based on the atypical breed distribution in our case series, we believe hydrocephalus should be considered in any young dog with forebrain signs.

Adequate selection of the dogs that may benefit from VP shunting is most important. Our decision to shunting these dogs was based on neurologic assessment and MRI findings. All dogs were initially treated medically and either failed to improve or had relapse of clinical signs during treatment. Failure to respond to medical therapy is reported as an indication for surgical treatment of hydrocephalus.1 Brain MRI consistently revealed dilated lateral ventricles with variable periventricular edema. Progression of the forebrain signs and presence of periventricular edema and/or mass effect on the caudal fossa structure, were interpreted as indicators of expanding hydrocephalus14 and were used as criteria to perform shunting.

Few veterinary studies have attempted to identify more objective guidelines for decision making before VP shunting.31,32 One study identified an association between presence and severity of neurologic signs and basilar artery resistance index and ventricular to brain ratio.31 In addition a ventricular to brain ratio >60% was identified as a predictor for development of neurologic signs31; however, another study failed to identify an association between ventricular size and severity of neurologic signs in dogs.32 This discrepancy may reflect the difficulties encountered when trying to indentify general guidelines to apply to a heterogeneous population of dogs such as those with hydrocephalus.

Neurologic improvement was observed within a week of surgery and at the 4 week recheck in 13 dogs regardless of the underlying cause of hydrocephalus. Two dogs were thereafter euthanatized (2 and 4 months postoperatively) on owner request because of persistence of seizure activity. This may suggest that, although the shunting procedure may be effective in improving the neurologic deficits, it may not be very effective in altering the seizure pattern.

Direct comparison between this case series and other reports17,24 on canine hydrocephalus is limited because of differences in the type of dogs being treated. In our study, morbidity associated with the surgical technique was minimal and mainly consisted of postoperative discomfort that responded to opioids and/or paracetamol. Considering that all dogs were being administered prednisolone at the time of surgery, paracetamol was chosen as an analgesic instead of a licensed nonsteroidal anti-inflammatory drug to prevent complications because of simultaneous use of nonsteroidal anti-inflammatory medications and steroids. All dogs but one were discharged within 1 week of surgery.

Several postoperative complications (including infection, catheter migration, shunt under drainage, kinking of the peritoneal catheter, valve fracture, and abdominal skin necrosis) occurred in 29% of dogs studied. Similar complications have been reported in people with a rate of up to 40%, regardless of shunt type.33,34 Shunt infections occur at a rate ranging from 6% to 20% in people and appear to occur more commonly within the first 6 months of surgery.35–37 Two dogs (14%) had infection 6 and 18 months postoperatively. An explanation for this late onset of infection could not be identified. Staphylococcus spp. was cultured from the CSF of both dogs. Staphylococcus spp. is also the most commonly isolated bacteria in people with shunts38 and Gram-negative bacteria represent ∼15% of shunt infections.39,40 Thirty-nine percent mortality, 22% permanent brain damage and 17% mental retardation have been reported after Gram-negative infections in children.39,40 Prophylactic antimicrobial therapy is still controversial in people; however, meta-analyses of randomized trials of prophylactic antimicrobial agents in CSF shunts suggest a statistically significant effect favoring antibiotic prophylaxis (∼50% reduction in infection risk).41,42 Protocols of prophylaxis against infections included, the use of vigorous asepsis, limited staffing in the operating theatre, first operation in the morning, minimal skin exposure, 1 dose of antibiotics, and a skilled neurosurgeon. This reduced infection rate from 15% to 0.33% in 1 study43 and from 13% to 3.8% in another.44

Mechanical shunt failure is one of the most common complications of shunting.23 The shunt catheters can be occluded from a variety of causes including debris, blood, protein, intra-parenchymal placement, choroids plexus, coaption of the ventricular walls, gliosis, or infection. Such occlusion accounts for ∼50% of shunt complications in the pediatric population.45 Mechanical failure of the shunting system occurred in 3 dogs with acquired hydrocephalus. One dog, in particular, had 2 types of mechanical failure, migration of the tip of the ventricular catheter inside the ventricular mass and shunt under drainage. We speculate that presence of an acquired cause of hydrocephalus (intraventricular mass and inflammatory disease) might have predisposed these dogs to mechanical shunt failure. However, the number of dogs is too small to draw definitive conclusions. Shoulder pain, ascites, pseudocysts and perforation of the abdominal wall, gallbladder and intestines are also complications seen in people after VP shunting.34,46–48 One dog developed a small area of skin necrosis above the site of peritoneal catheter insertion 9 months postoperatively. The reason for developing this late complication can be associated with a possible flank trauma or mobilization of the distal portion of the catheter because of the very active nature of the dog (Jack Russell Terrier); this might have led to secondary skin pressure necrosis. Skin pressure necrosis has been reported previously in 1 dog 2 months postoperatively.16

Three dogs with idiopathic hydrocephalus were euthanatized on owner request because of persistent seizure activity (2 dogs) and relapse of the neurologic signs (1 dog). Overall 6 of 9 dogs with acquired hydrocephalus were euthanatized because of progression of the underlying disease confirmed by MRI or necropsy in 5 dogs. None of the dogs were euthanatized or died as a consequence of VP shunting or because of postoperative complications. The 2 most common reasons for euthanasia were, persistence of seizure activity in dogs with idiopathic hydrocephalus and progression of the underlying disease in dogs with acquired hydrocephalus. Persistency of seizures activity despite shunting might be because of the presence of altered cellular connectivity or neurotoxicity, that have been described in association with hydrocephalus.14

Progression of the underlying disease was expected when an intraventricular mass/tumor was diagnosed. These dogs, however, did benefit from VP shunting although for a limited time. Outcome in people that undergo CSF shunting strongly depends on the underlying disease (ie, congenital malformations, aqueductal stenosis, local neoplasia, or diffuse systemic cancer).49,50 Cumulative survival rates of people undergoing CSF shunting are around 50% at 5 years postoperatively and between 30% and 40% at 10 years.49 In our study, nearly 43% of dogs were alive at 12 months postoperatively. Like most veterinary studies, survival was influenced by the owners' decision to have the dog euthanatized based on their subjective assessment of the dog's quality of life. Additionally, we can assume that treatment in people is started much earlier than in dogs. Early clinical signs of increased intracranial pressure in people often include headache, blurred vision and nausea, signs that would be quite difficult to recognize in animals. In people, there is general agreement that early shunting maximizes the chances of obtaining a successful outcome.19,51

In summary, VP shunting was performed in 14 dogs with obstructive hydrocephalus; 13 had marked improvement of neurologic signs in the immediate postoperative period and were discharged within 1 week of surgery. No complications directly related to the surgery occurred. Four dogs (29%) developed complications, and 3 of these had >1 problem, all of which were readily resolved either medically or surgically. Persistence of seizure activity in dogs with idiopathic hydrocephalus and progression of the underlying disease in dogs with acquired hydrocephalus were the 2 most common reasons for euthanasia. Persistence of seizure activity would therefore appear to be an important point to discuss with the owners when planning VP Shunting. Progression of the underlying disease was expected in dogs with acquired hydrocephalus; however, we believe that VP shunting can be offered as a palliative, adjunctive treatment in dogs with acquired hydrocephalus that present with severe and progressive forebrain signs and do not respond to medical treatment. Overall, long-term outcome for dogs after VP shunting was guarded irrespective of the underlying cause of the hydrocephalus. This, however, may reflect an atypical dog population and the limited number of dogs in this case series.

ACKNOWLEDGMENTS

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

This study was performed at the Animal Health Trust, Newmarket, UK with the support of Vetoquinol.

REFERENCES

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES