Lumboperitoneal Shunt Placement

Placement of a lumboperitoneal shunt is an effective method to divert spinal fluid. Two general types of lumboperitoneal shunts are in use today: valve-mediated and valveless types. The placement techniques described below are common to both.

Lumboperitoneal shunting is a method of diverting cerebrospinal fluid (CSF) from the subarachnoid space to the abdominal cavity. Advantages of lumboperitoneal shunting include avoidance of brain penetration with the shunt catheter, access to a large CSF space in the thecal sac, and the potential (for good or ill) of a large amount of CSF drainage.

Patients who require a lumboperitoneal shunt have pathology that predisposes to obstruction of CSF absorption or elevated CSF pressure but must have communication of the spinal CSF with the cranial compartment. Specific indications include, but are not limited to, communicating hydrocephalus, normal pressure hydrocephalus, and idiopathic intracranial hypertension (pseudotumor cerebri).[1, 2, 3, 4, 5]

Lumboperitoneal shunts can also be placed for management of localized pathology that affects the spinal cord. They have been used to drain and prevent reformation of pseudomeningoceles, or unwanted collections of CSF. Lumboperitoneal shunts have also been used to help minimize CSF leaks, either natural or iatrogenic. The principle is to decrease the fluid pressure on the dural defect and thus prevent excessive CSF leakage. Its use in the treatment of spinal syringomyelia has also been reported.[6]

A lumboperitoneal shunt should not be placed in patients with localized elevated pressure and mass effect in the cranial cavity (eg, intracranial tumor or subdural hematoma). Excessive shunting of CSF in the spine may create a pressure gradient across the craniospinal junction, promoting downward brain herniation. A Chiari malformation is a relative contraindication to lumbar shunting for this reason. In addition, the spinal CSF space must freely communicate with the cranial CSF space.

Complication Prevention

Lumboperitoneal shunt complications can be divided into those involving the lumbar catheter, those involving the peritoneal catheter, and general complications. Valve complications can also exist if a catheter system with a valve is installed.

Lumbar catheter complications include overdrainage of CSF, catheter obstruction, catheter migration, catheter misplacement, and spinal nerve irritation.[1, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24] Overdrainage of CSF is a commonly cited complication; symptoms generally involve postural headaches, nausea, and vomiting. More severe manifestations of overdrainage, acquired Arnold Chiari displacements and subdural hematomas, have been reported. To reduce the incidence of overdrainage, some surgeons advocate the use of valved-shunt systems. Valved systems allow a fixed volume of CSF to be drained into the peritoneal cavity, or drainage against a fixed pressure (see below).

As the lumboperitoneal catheter is placed in close proximity to the spinal nerves, spinal nerve injury or radiculopathy can occur. In general, the needle should not be placed above the L3 level to avoid potentially injuring the spinal cord. As the patient is in the lateral decubitus position, the Tuohy needle should be inserted with the sharp up-curving end of the needle in parallel to the patient’s longitudinal axis. Once placement of the needle is confirmed, the Tuohy needle should be rotated 90º to allow the catheter to be fed in a rostral or caudal direction. Multiple attempts at spinal puncture can lead to a postoperative CSF leak. Fluoroscopy can be used intraoperatively to aid in placement.

Catheter migration within the spinal and peritoneal compartment is common. Preventive steps involve using sutures and anchors (usually provided with the shunt system) to secure the spinal catheter in place to the lumbar fascia after proper intraoperative placement. Nonetheless, reports of migration have been reported despite securing the catheter.[17, 18, 23, 24, 25]

Shunt infections[1, 7, 9, 25] are not as common in adult patients as are shunt displacements. Steps to prevent infection include proper preoperative surgical site disinfection, careful draping (consider glove change after draping), and minimizing operating time. Systemic antibiotics should also be given within one hour prior to skin incision. The catheter system can be stored in an antibiotic solution prior to insertion but generally is not opened until ready for use.

Blockage of the shunt system, resulting in failure of the system, can occur. The reported incidence of shunt revision due to obstruction ranges from 14%-62%. The incidence of shunt infection and resulting meningitis ranges from 1%-10% of all lumboperitoneal shunts. Shunt infection can also result in shunt obstruction.[1, 8, 9, 26]

Migration of the shunt catheters is also a common experience. The lumbar catheter can migrate relative to the thecal sac (usually into the subcutaneous space), and the peritoneal catheter can likewise come out of the peritoneum. The incidence ranges from 3%-20%. Migration complications have been noted to be more common in the pediatric population.[8, 26, 27] When a catheter migrates out of the thecal sac, a subcutaneous collection of spinal fluid can be observed.

Newly onset radicular pain has been noted to occur with lumboperitoneal shunts. This may result from catheter migration or localized inflammation leading to arachnoiditis. The onset of symptoms may necessitate shunt revision. The incidence of developing newly onset radicular pain ranges from 5%-6%.[1, 26]

Overdrainage of CSF can result in intracranial hypotension and positional headaches. Incidence has been noted to be from 5%-10%.[25, 27] Valves have been designed to trigger at different pressures in the recumbent and standing position (see below), and programmable valves are also available. In one case report, authors report overdrainage secondary to an iatrogenic dural defect when placing the lumbar section of the shunt.[16] On the other hand, underdrainage without relief of preoperative symptoms is also possible. Incidence can range from 9%-12%.[8]

Intracerebral hemorrhages and secondary Arnold Chiari-type tonsillar herniation have been reported. The incidence of postprocedure subdural hematomas ranges from 2%-4%.[1, 9] Isolated case reports of intraparenchymal hemorrhages, as well as abdominal hemorrhages that occur after shunt placement, have also been reported.[21, 22] The incidence of Arnold-Chiari 1 displacements have been reported to occur in up to 70% of patients. However, only a smaller subset of patients, 1%-14%, have been described to develop symptoms.[2] Interestingly, associated scoliosis has also been reported.[14]

In addition to the standard surgical instruments needed to open and close the peritoneal cavity, a Tuohy needle and catheter passing instrument (shunt tunneler) are used when placing a lumboperitoneal shunt. The Tuohy needle is a hollow needle used to access the spinal compartment and has a curved tip to direct the catheter. The catheter passing instrument is a hollow metal tube used to bluntly dissect through the subcutaneous tissues. Specifically, it is used to pass the catheter from the spinal access site to the flank and/or the abdominal incision.

Anesthesia

General anesthesia is typically used when placing a lumboperitoneal shunt, but other options are possible.

Positioning

The patient is placed in a lateral decubitus position with arms raised above the shoulders. Care is taken to properly support the patient’s arms in a position of comfort and to avoid localized compression. Soft gel pads are placed to maintain the patient in this position. The lateral decubitus position gives the surgeon operative access to both the spinal and peritoneal compartments, as well as the tract along which the catheter is passed.

Once in this position, the patient is widely prepared in the region to allow for access to more than one spinal level, along the lateral aspect of the patient’s flank where the catheter is passed or valve placed, and on the abdomen where the peritoneal cavity is accessed. Visibility of the superior iliac crest should be maintained as an anatomic landmark.

Maintenance of a lumbar-peritoneal shunt requires access to urgent neurosurgical care, although routine follow-up or shunt studies are probably unnecessary. Of course, a return of symptoms would typically lead to an investigation of shunt function. Radionuclide shunt studies are not routinely performed, but CT scans are often used to diagnose displacement, and a lumbar puncture can usually be used to measure CSF pressure.

Two general types of lumboperitoneal shunts are in use today: valve-mediated and valveless types. The placement techniques described below are common to both.

As noted above, the patient is typically placed in a lateral decubitus position. The iliac crests serve as a reasonable landmark for the L4-5 spinal level. Fluoroscopy can be used for greater accuracy, and there is reason to believe that the L5-S1 level may be a better site, in case of an epidural hemorrhage due to needle puncture.

After preparation of the skin and draping of the lumbar area, flank, and abdomen, a longitudinal incision is made in the midline, and dissection is carried down to the muscle fascia layer. A Tuohy needle is inserted into the thecal sac and should be well within the space to allow for passage of the catheter (see image below).

The Tuohy needle should be placed with the needle bevel aligned in a rostral-caudal direction; whether rostral or caudal is a matter of preference. The authors suggest measurement of pressure at this point, although the positioning and the presence of general anesthesia and ventilation makes this reading rather artificial. The lumboperitoneal catheter can then be eased through the Tuohy needle and into the thecal sac for approximately 6-8 cm to allow for some displacement upon removal of the needle (see the image below). The catheter should never be withdrawn through the needle once it has passed the tip to avoid shearing off the end of the catheter. If additional attempts are necessary, remove the needle with the catheter.

The peritoneal cavity can be accessed simultaneously, as resources allow, through a laparoscopic approach or under direct vision. One advantage of the laparoscopic approach is that the catheter can be inserted through the flank incision, which is used to position a valve. A direct approach to the peritoneum usually requires a more medial ventral incision. Dissection through Scarpa fascia, innominate fascia, the muscle layers, and transversalis fascia is performed successively until the peritoneal membrane has been reached.

At this point, if a valve is to be placed, a flank incision is made, and the catheter-tunneling instrument is used to connect the lumbar to the flank incision. If no valve is to be placed, tunneling can be accomplished from the lumbar region to the abdomen, depending on the patient’s habitus. An intervening incision may be required. Assuming a valve is being placed, the spinal catheter can be brought to the flank exposure, taking care not to dislodge it from the thecal sac. An anchoring device can be sutured to the lumbar fascia to reduce the chance of displacement, leaving additional tubing as a strain relief. The valve is then connected to the cut end of the spinal catheter, and additional tubing is placed in a similar fashion from the flank incision to the abdominal incision (see the images below).

Flow from the distal end of the system should be ascertained before placement into the peritoneal cavity. The authors typically put a purse-string suture in the peritoneum around the catheter to lessen the risk of displacement. Little concern exists about leaving too much catheter in the peritoneal space.

Closure is carried out in standard fashion. As described above, the laparoscopic approach allows for smaller abdominal incisions and placement from the flank incision site.