Recurrent tethered cord syndrome: a novel approach for a difficult surgical condition?

Tethered cord syndrome (TCS) is a challenging disorder with a complex multifactorial etiology, which includes a thickened terminal filum, postrepair myelo­ meningocele, lipomyelomeningocele, and postoperative arachnoid adhesions.7 There are specific indications for surgery and clear surgical options including meticulous microscopic untethering of the cord, dividing the termi­ nal filum, addressing the local pathology, and dividing adhesions. The use of adjuncts such as microsurgical techniques and intraoperative monitoring with micro­ stimulation and recording has proved to be useful in re­ ducing surgical morbidity.9 Unfortunately, as is common with such troublesome pathologies, the story often doesn’t end there. A number of patients who have undergone sur­ gical treatment for TCS can present with clinical and ra­ diological evidence of recurrent tethering.7 The treatment of recurrent cases, particularly those with multiple pre­ vious procedures or in whom the underlying pathology may not allow for compete microsurgical release, is par­ ticularly challenging. Considerable surgical acumen and skill are necessary to avoid neural injury and deal with postoperative complications such as wound breakdown, CSF leakage, and further recurrence of scar tissue, which naturally contracts, leading to further tethering. There are a host of surgical techniques to avoid re­ tethering and also several treatment options available. These include simple ideas like frequent patient turning while he or she is in the prone position postoperatively and early mobilization to avoid gravitational contact between the neural structures and the dura mater, and the use of synthetic dural substitutes to minimize adhe­ sions.5 Other methods to minimize retethering include intradural retention sutures placed with subsequent du­ raplasty using autologous thoracolumbar fascia,11 and a technique of retaining the cord in the midline by fine stay sutures, between the pia mater and the conus and the anterior dura to posterior osseous elements.10 In keeping with its severity, there have even been drastic measures such as sectioning of the entire cord at a functionless lev­ el in cases of recurrent TCS.1 Other less desperate treat­ ment options include conservative, symptom­driven care, and reexploratory microsurgical untethering operations. Repeated operations for TCS have the general complica­ tions that accompany additional surgery, namely lack of an adequate vascular infrastructure, wound breakdown, and danger to the underlying neural structures. For the aforementioned reasons, alternative surgical options to manage recurrent or refractory tethered cord syndrome are welcome. In this issue of Journal of Neurosurgery: Spine, Hsieh et al.4 report on the use of ver­ tebral subtraction osteotomy to treat 2 cases of recurrent TCS. As is common with novel operative techniques, the seeds for surgical innovation were planted in a cadaveric study.2 Using a fresh­frozen human cadaver model, those authors demonstrated that vertebral subtraction at T­11 and T­12 significantly reduced tension in the terminal fi­ lum and lumbosacral nerve roots. In a natural follow­up, Hsieh et al. have elegantly shown how lateral thinking in surgery can be used to treat a complex problem. Using 2 well­described cases of repeated surgically treated TCS, they described the application of vertebral subtraction osteotomy to manage this challenging condition. The 2 patients described had undergone 4–5 previous surgeries, and in the patient in Case 2, a synthetic dural graft had previously been used in a futile attempt to prevent reteth­ ering. The initial conclusions from both cases would sug­ gest that a posterior vertebral subtraction of 15–25 mm can lead to marked reduction in terminal filum tension, equivalent of releasing 90% of neural elements. Such an attempt in a field of recurrent dense fibrosis would cer­ tainly not be without a danger to neuronal function. Although the authors should be commended for the application of lessons learned in one area of spine sur­ gery to another challenging surgical field, the approach 275 277 See the corresponding article in this issue, pp 278–286.