Surgical Management of Cerebrospinal Fluid Leakage After Spinal Surgery

Incidence and Prevalence

Dural tears with CSF leaks are well-documented and common complications of spinal surgeries. Prevention of CSF leak is a focal point of any spine surgery. However, the incidence rate is hypothesized to be underreported because of the lack of associated morbidity with most dural tears. Thus, the prevalence is largely debated, but has been reported to be 0.5% to 18%. ^, The prevalence of CSF leaks is higher in patients undergoing revision surgery and it is advisable to address areas devoid of scar tissue prior to working in areas where scar tissue exits from prior surgical intervention. The occurrence and management of CSF leaks are specific to the region and the surgical approach.

Specific Regions and Surgical Approaches

The lumbosacral region is noted as the most common location for dural injuries. This is due to the anatomy of the region and to how commonly spine surgeries are done in this region. ^, Many conditions facilitate dural tears, including thinned dura, prior spinal surgery, dural fibrosis, spinal stenosis, and spinal bifida. ^, Additionally, ossification of spinal ligaments, use of a high-speed drill, and synovial cysts have been associated with dural tears. ^, Postoperative causes of increased intra-abdominal pressure, including constipation, urinary retention, and cough, can also lead to dural tears. Numerous mechanisms such as trauma, disc fragments, bone spikes, excessive dural traction, iatrogenic laceration by sharp instruments, or intradural explorations have led to CSF leaks with several dramatic consequences. ^, Potentially, leaks can lead to pseudomeningocele formation, intracranial hypotension, neural element herniation with pain and neurologic deficits, wound dehiscence, fistula formation, and infection. ^{, ,} Therefore, any CSF leak warrants immediate repair.

CSF leaks frequently occur in extradural procedures during decompression of severe spinal stenosis or during revision surgery where scar tissue is prevalent. In a patient who has not previously undergone spine surgery, the bony structures should be removed initially with a Leksell rongeur and a high-speed drill superficial to the ligamentum flavum. Ideally the drill should be used in a medial-to-lateral fashion to reduce incidence of slippage and tear. Proper and adequate dural separation from the overlying fascia and lamina must be performed to reduce the incidence of any dural tear, which is most commonly caused by dura being caught between the Kerrison rongeur footplate and the bone. Therefore, a fine dissecting instrument, such as an angled curette or Woodson dissector, should be utilized before placement of a cutting instrument in the epidural space. This exercise becomes even more important in a revision case, as there is associated scar formation and it can be adherent to dura. A 3% to 5% higher rate of duratomy has been reported in revision cases. ^{, ,} It is recommended in revision cases that the laminectomy be extended to obtain an area of dura that has not been previously operated on prior to approaching a segment of dura which potentially contains scarred/abnormal tissue. ^, If the scar is easily dissected from the dura, then a blunt dissector may be utilized; otherwise sharp dissection may be needed for safe exploration.

Use of spinal instruments as well as bony spikes are reported causes of delayed CSF leaks. Medial placement of pedicle screws or deep placement of anterior spinal fusion plating screws can lead to dural injures with late presentation of CSF leak symptoms. In these scenarios, CSF leaks may not be noted during the surgery or may not even exist in the case of injury with bony spikes. Special attention must be made to obtain proper length and placement of screws. In addition, bony spikes should be eliminated by smoothing the bony edges. In case of a surgical repair, extension of bony decompression may be warranted in order to directly expose the dural injury for adequate visualization and repair. Also, intraoperative Valsalva maneuver and tilting of the table to increase the dependent position of durotomy can help in direct evaluation of the dura.

The relative risk of developing an intraoperative inadvertent dural tear using an anterior procedure has been reported to be increased in patients undergoing corpectomy, fusion, surgical management of ossification of the posterior longitudinal ligament (OPLL) and revision. Dural injuries during anterior spinal operations follow the same principles as previously mentioned. Proper and careful dural dissection in addition to adequate bony exposure is essential to prevent and repair leaks in these approaches. However, special attention must be given to cases involving ossification of posterior longitudinal ligaments, as dural injuries in the cervical spine are most prevalent in the presence of OPLL. These patients are 13.7 times more likely to have CSF leaks during their spinal surgeries. If a laceration occurs and warrants a suture repair, dura should be carefully dissected parallel to its fiber. However, following the removal of the posterior longitudinal ligament, a dural gap is often created, which requires a patch for repair. Occasionally, this gap may not be completely covered, in which case it can be sewn onto the dura as much as possible, with the remainder of the defect being sealed with fat, muscle, and fibrin glue.

The transoral approach has a deep surgical field and it is particularly susceptible to penetration by instruments and injury to the dura. CSF leaks during transoral approaches can have significant mortality; thus many neurosurgeons recommend a preoperatively placed lumbar drain to reduce the hydrostatic pressure on the wound. If the dural tear is significant, then the lumbar drain may need to be converted to a shunt to maintain a low pressure for at least 1 month postoperatively.

In an intradural case, dura may be opened in a midline or paramedian fashion. These cases mostly involve spinal tumors or biopsies for which dura can be easily repaired by watertight dural suturing under a microscope. With meningiomas and a dural defect that is under tension, if dorsally located and adequate exposure is obtained, a dural patch may be used for sealing of the dura. However, with far lateral approaches to the spine or ventral defects, dura may not be easily repaired. In this situation further treatments (as described later) may be necessary to prevent CSF leakage.