Posterior spinal fusion with the use of unit rod instrumentation has been successful in the treatment of neuromuscular scoliosis
1-3 . The reported complications of this procedure include wound infection, pulmonary embolism, pneumonia, skin ulceration, excessive blood loss, pneumothorax, latex anaphylaxis, superior mesenteric artery syndrome, pancreatitis, instrumentation failure, pseudarthrosis, and spinal cord injury
1-11 . We report on two children with cerebral palsy who sustained life-threatening hydrocephalus due to dysfunction of a ventriculoperitoneal shunt after posterior spinal fusion. To our knowledge, this unusual complication has not been reported previously.
Both of our patients had severe scoliosis secondary to spastic quadriplegic cerebral palsy, and both had a history of hydrocephalus treated with a shunt. In both patients, the correction of the spinal curve at surgery was marked. In one of the two patients (Case 1), fracture of the shunt tubing in the cervical region was noted in the immediate postoperative period, but a computed tomographic scan of the head demonstrated no ventricular dilation at that time. Profound symptoms occurred approximately four weeks after the procedure, requiring emergent decompression of a hydrocephalus and revision of the ventriculoperitoneal shunt. In the other patient (Case 2), fracture of the shunt tubing in the cervical region had been recognized two years prior to the spinal fusion. Computed tomographic evaluation of the shunt at that time demonstrated no ventricular dilation, and the hydrocephalus was thought to have arrested. On correction of the scoliosis, the distance between the two ends of the fractured tubing in the cervical region increased, resulting in profound hydrocephalus within eight weeks after the spinal procedure.
Case 1. A ten-year-old boy with severe spastic quadriplegic cerebral palsy and a history of hydrocephalus treated with a shunt was evaluated because of increasing difficulties with sitting in a wheelchair as a result of increasing spinal deformity and pelvic obliquity. The patient had had a ventriculoperitoneal shunt placed in infancy for hydrocephalus associated with intraventricular hemorrhage, with no subsequent revision or malfunction of the shunt. Radiographs of the spine made with the patient sitting demonstrated scoliosis measuring 82° as well as an intact right ventriculoperitoneal shunt (
Fig. 1-A ). The patient underwent a posterior spinal fusion that extended from T2 to the sacrum, with the use of unit rod instrumentation and sublaminar wiring. A postoperative radiograph demonstrated correction of the curve to 10° (
Fig. 1-B ). The upper thoracic and cervical portion of the shunt tubing was not clearly visualized on the postoperative radiograph. On the second postoperative day, routine radiography of the chest revealed a fracture of the ventriculoperitoneal shunt tubing in the cervical region (
Fig. 1-C ). Computed tomography of the head performed on the third postoperative day was interpreted as showing normal-sized ventricles (
Fig. 1-D ), although a baseline scan was not available for comparison. The patient was discharged from the hospital on the tenth postoperative day without signs of a change from his baseline mental status or neurologic function.
Approximately four weeks after the surgery, the patient was brought to the emergency department by his parents for evaluation of emesis, lethargy, and decreased alertness over the previous four to five days. On examination, the patient was hypertensive, bradycardic, and unresponsive. The incision from the prior posterior spinal fusion was well healed, with no signs of infection. Neurologic function was determined to be globally delayed, less responsive than at baseline, and generally hypertonic and hyperreflexic. The orthopaedic and neurosurgery services were consulted, and a computed tomographic scan of the head revealed dilated ventricles (
Fig. 1-E ). A ventricular shunt tap, performed in the emergency room, revealed an elevated intracranial opening pressure of 27 cm H2O (normal, <10 mm Hg [13 cm H2O]), and 15 mL of cerebrospinal fluid was removed. The closing intracranial pressure was 6 cm H2O. After the tapping of the shunt and removal of the cerebrospinal fluid, the patient's level of alertness and his overall condition immediately improved. The patient underwent emergent revision of the shunt on the day of admission. The symptoms had completely resolved by the following day, and the patient was discharged to home. Two weeks after the shunt placement, a repeat computed tomographic scan of the head showed that the ventricles had returned to normal size without dilation (
Fig. 1-F ), and radiographs showed adequate placement of the shunt.
Case 2. A twelve-year-old girl with severe spastic quadriplegic cerebral palsy and a history of hydrocephalus treated with a shunt was evaluated for severe scoliosis that limited her ability to sit in a wheelchair despite several wheelchair modifications. The patient had a history of prematurity and intraventricular hemorrhage that required placement of a ventriculoperitoneal shunt in the neonatal period. She had not had a subsequent replacement or malfunction of the shunt. Two years prior to our evaluation, the ventriculoperitoneal shunt had been noted to be fractured in the cervical region; this was an incidental finding on a chest radiograph that had been made at an outside institution during an evaluation for pneumonia. A computed tomographic scan of the head performed at that time had reportedly demonstrated normal ventricles, and the patient was asymptomatic. There was no further intervention to address the shunt fracture, and because the neurologic status had not deteriorated since the fracture had been noted, the hydrocephalus was believed to have arrested.
A posterior spinal fusion with instrumentation was recommended to address the spinal deformity. The preoperative curve measured 80° (
Fig. 2-A ), and the shunt tubing at this time was seen to be overlapping itself by 1 mm at the site of the shunt fracture (
Fig. 2-B ). The patient underwent a posterior spinal fusion extending from T2 to the sacrum, with use of unit rod instrumentation and sublaminar wiring. A postoperative radiograph demonstrated correction of the curvature to 15° (
Fig. 2-C ). In this patient, as in Case 1, the cervical portion of the shunt tubing was not clearly visualized on the postoperative radiograph. The patient had an uncomplicated postoperative course and was discharged from the hospital fifteen days after the procedure.
At the first postoperative outpatient follow-up visit at four weeks, a radiograph of the spine revealed that the ends of the fractured shunt were separated by 15 mm (
Fig. 1-D ). The patient was doing well, and the mental and neurologic status was the same as before surgery.
Approximately eight weeks after surgery, the patient was reevaluated because of a one-week history of increasing lethargy, intermittent episodes of abdominal pain, and loss of consciousness that lasted between five and ten minutes. On examination, the patient was noted to be less responsive than she had been at the baseline evaluation, with an increase in muscle tone and hyperreflexia. The incision from the posterior spinal fusion was well healed. A computed tomographic scan of the head demonstrated dilated ventricles. After a neurosurgical consultation was obtained, an emergent tap of the ventricular shunt was performed that revealed an elevated intracranial opening pressure of >20 cm H2O (normal, <10 mm Hg [13 cm H2O]), and 15 mL of cerebrospinal fluid was removed. The closing intracranial pressure was <10 cm H2O. After the shunt was tapped and the cerebrospinal fluid was removed, the patient's level of alertness and overall condition immediately improved. The patient underwent subsequent shunt revision on the day of admission. The acute symptoms had completely resolved by the following day, and the patient was discharged to home.
Four weeks after revision of the shunt, a repeat computed tomographic scan of the head showed resolving ventricular dilation, and a shunt survey demonstrated adequate placement of the shunt. Neurologic function remained at the baseline level without deterioration.
While most patients with cerebral palsy do not have a history of hydrocephalus treated with a shunt, progressive ventricular dilation secondary to intraventricular hemorrhage in premature infants is the most common indication for placement of a ventriculoperitoneal shunt during the neonatal period. Acute hydrocephalus appears to be secondary to an impairment of cerebrospinal fluid absorption caused by particulate blood clot, and subacute chronic hydrocephalus is presumably related to obliterative arachnoiditis in the posterior fossa, where the blood tends to collect. Slowly progressive ventricular dilation will develop in approximately 35% of premature infants with intraventricular hemorrhage, and approximately 15% of that group will require placement of a ventriculoperitoneal shunt
12 .
Shunt dysfunction has been extensively evaluated in patients with myelomeningocele
13-20 . Echizenya et al. evaluated the mineralization and biodegradation of twenty-five shunts that had remained implanted for a period between six days and ten years
16 . They found that the ultimate tensile strength and extensibility of the shunt tubing decreased gradually during the first three years after implantation and became remarkably altered after five years, suggesting that the shunt system becomes progressively less elastic and more fragile with time.
To attain a better understanding of the mechanical complications and failures of ventriculoperitoneal shunts, Sainte-Rose et al. retrospectively evaluated 1719 patients with hydrocephalus
20 . They reported shunt malfunction in 81% at twelve years, with fracture or disconnection of the tubing in 13.6%. In that study, the existence of a shunt tube connector was considered to be the major cause of shunt fracture. Placement of the connector in the thoracic or abdominal wall led to a higher rate of fracture than did placement of the connector in the cervical region. Cuka and Hellbusch found a rate of shunt fracture of 17.4% in a retrospective review of 401 patients
15 . They reported that the catheters most often became fractured in the cervical region approximately three years after insertion.
Hoover et al. reported on a twelve-year-old boy with myelomeningocele at the L3 level, scoliosis of 103°, and severe pelvic obliquity who sustained a ventriculoperitoneal shunt fracture after surgical correction of the scoliosis
19 . Symptoms of hydrocephalus developed seventy-two hours after surgery, and the patient underwent emergent shunt revision. The authors found the shunt to be fractured and calcified in the cervical region. They recommended performing an evaluation for a fractured or disconnected shunt when neurologic deterioration occurs after correction of spinal deformity in a patient with myelodysplasia. Geiger et al. evaluated the complications that occurred in a group of seventy-seven patients with myelomeningocele who had undergone scoliosis surgery
18 . They found that five patients had insufficiency of the ventriculoperitoneal shunt within three months after correction of the scoliosis. No details of the specific causes of insufficiency were discussed in that report; however, the authors recommended neurosurgical evaluation to confirm proper functioning of the shunt.
In our Case 2, the ventriculoperitoneal shunt had been recognized as being fractured at least two years prior to the spinal procedure. In retrospect, the fractured shunt was likely still functioning, suggesting the existence of a patent fibrous tract communicating between the cephalad and caudad ends of the fractured shunt tubing. That tract was likely disrupted on correction of the spinal deformity. Clyde and Albright reported two cases with evidence of such a patent fibrous tract in a fractured, outgrown, or disconnected ventriculo-peritoneal shunt
14 . They warned against assuming that hydrocephalus has arrested in a patient with a documented shunt fracture or disconnection, and they recommended that studies be performed to determine that the shunt is functioning.
Both of our patients had features that may have predisposed them to shunt fracture or dysfunction. In both patients, the shunt had been in place for more than ten years, the shunt tube connector was located in the thoracic region, and the scoliosis was severe, necessitating extensive surgical correction. In Case 2, a shunt fracture had been noted two years preoperatively, and the hydrocephalus was assumed to have arrested because the patient was asymptomatic. Neither of our patients had had a recent preoperative computed tomographic scan of the head so it was not possible to compare the postoperative ventricular size with that present preoperatively.
On the basis of the studies described above as well as our two cases, we recommend that the preoperative evaluation for scoliosis correction in a child with cerebral palsy and a history of hydrocephalus treated with a shunt include, at the very least, documentation of the structural integrity of the shunt. Particular attention should be paid to the cervical portion of the shunt because of the high rate of failure in this region. When the cervical portion of the shunt is poorly visualized on the preoperative full-length spinal radiograph, an anteroposterior radiograph of the cervical spine should be made as a way of documenting shunt integrity in this region. The integrity of the shunt should be documented again on postoperative radiographs because of the possibility of shunt fracture during the correction of a large deformity.
If the preoperative radiograph demonstrates shunt fracture, computed tomography of the head should be performed to determine baseline ventricular size. We caution against assuming that hydrocephalus has arrested in a patient with a documented shunt fracture because a patent fibrous tract may exist through the area of separation. Further separation of the fractured shunt during correction of the spinal deformity may disrupt such a tract, leading to life-threatening hydrocephalus.
If the postoperative radiograph demonstrates shunt fracture, an immediate computed tomographic scan of the head should be performed to serve as a baseline with which to compare subsequent scans. The onset of symptoms of hydrocephalus in our patients occurred one to two months after surgery. With the possibility of late presentation of symptoms, it would be advisable to obtain a follow-up computed tomographic scan before the patient is discharged from the hospital. A shunt revision is necessary if signs of ventricular dilation or symptoms of hydrocephalus are noted. Furthermore, the child's caretakers should be made aware of the signs and symptoms of shunt dysfunction and should be counseled that shunt dysfunction is a potentially life-threatening complication of a corrective spinal fusion in children with cerebral palsy and a history of hydrocephalus treated with a shunt.