Treatment and prevention of tethered and retethered spinal cord using a Gore-Tex surgical membrane

A Case of Partial Resection of an Intradural Extramedullary Tuberculoma Resulting in Improvement of Lower Limb Paralysis

Intradural extramedullary tuberculomas are a rare manifestation of tuberculosis that can lead to neurological deficits. We present a case of a 26-year-old male from Myanmar with lower limb weakness and gait disturbance, who was diagnosed with tuberculosis and found to have an intradural extramedullary lesion in the thoracic spine. Prompt surgical intervention was performed to address the lesion located at the T2-4 level. Although complete resection was hindered by strong adhesion, significant improvement in lower limb paralysis was achieved. The elasticity loss of the dura mater posed a challenge in suturing, necessitating duraplasty with a synthetic graft material. This case report emphasizes the potential significance of surgical intervention, including partial excision, in the management of intradural extramedullary tuberculomas. Surgical treatment can play a crucial role in improving neurological outcomes in patients with intradural extramedullary tuberculomas, even in challenging scenarios.

Anterior Subcutaneous Transposition With Expanded Polytetrafluoroethylene (ASTEP) for Cubital Tunnel Syndrome: Technical Note

BACKGROUND

Ulnar nerve entrapment neuropathy at the elbow is the most common upper-extremity entrapment neuropathy after carpal tunnel syndrome. Surgical treatment can be complicated by perineural scarring and fibrosis, which may lead to recurrent symptoms. Expanded polytetrafluoroethylene (ePTFE) is a synthetic polymer with antiadhesive properties.

OBJECTIVE

To introduce the operative technique and outcomes of anterior subcutaneous transposition with ePTFE (ASTEP) in primary and recurrent cubital tunnel neuropathy.

METHODS

We studied 14 adult patients (11 men, 3 women; mean age, 45 yr) with cubital tunnel neuropathy (10 primary, 4 revision) who underwent surgery with the ASTEP technique between January 2008 and May 2018. Pain, numbness in the fourth/fifth fingers, and weakness of the intrinsic hand muscles were the most common presenting symptoms. Surgical outcomes were assessed using the modified McGowan and Wilson-Krout criteria.

RESULTS

The average (± standard deviation) preoperative symptom duration was 12.1 ± 5.2 mo (McGowan Grade 1, n = 5; Grade 2, n = 6; Grade 3, n = 3). No intraoperative or postoperative complications were observed with the ASTEP technique. Postoperative follow-up ranged from 9 mo to 7 yr (mean, 4.3 yr). All 14 patients experienced improvement in or complete resolution of their symptoms after this unique intervention.

CONCLUSION

Our novel technique of anterior transposition of the ulnar nerve with ePTFE was safe and highly effective in treating primary and recurrent ulnar nerve entrapment neuropathy at the elbow and represents an alternative to the current techniques.

Myelomeningocele Repair Combining a Double Cryopreserved Amniotic Membrane Homograft and the Keystone Flap in a 3-Year-Old Child: A Case Report

INTRODUCTION

Early repair in patients affected by myelomeningocele (MMC) is of paramount importance in order to prevent infection, minimize neural tissue damage, and reduce mortality. Treatment must include duraplasty and possibly an adequate soft tissue coverage. Delayed surgery in MMC patients can be more tedious due to the less clear borders between the placode and the skin. Moreover, the risks of wound infection and breakdown increase significantly.

CASE PRESENTATION

We present the unusual case of a large MMC in a 3-year-old patient treated by combining the recently described cryopreserved amniotic membrane (AM) as homograft for dural reconstruction and a bilateral Keystone flap for soft tissue reconstruction.

DISCUSSION

Thanks to its anti-inflammatory and elastic proprieties, the AM can play an important role in preventing adhesion between the reconstructed layers, thus reducing the risk of spinal cord tethering. The Keystone flap, at the same time, allows the wound tension to be distributed widely over the flap margins and not only along the midline, which overlies the duraplasty, enhancing the scar quality and lowering the risk of cerebrospinal fluid recurrence and wound dehiscence, with no donor site morbidity.

Comparison of Biomechanical Properties of Dura Mater Substitutes and Cranial Human Dura Mater : An In Vitro Study

Objective

The aim of this study was to investigate the biomechanical differences between human dura mater and dura mater substitutes to optimize biomimetic materials.

Methods

Four groups were investigated. Group I used cranial dura mater (n=10), group II used Gore-Tex^® Expanded Cardiovascular Patch (W.L. Gore & Associates Inc., Flagstaff, AZ, USA) (n=6), group III used Durepair^® (Medtronic Inc., Goleta, CA, USA) (n=6), and group IV used Tutopatch^® (Tutogen Medical GmbH, Neunkirchen am Brand, Germany) (n=6). We used an axial compression machine to measure maximum tensile strength.

Results

The mean tensile strengths were 7.01±0.77 MPa for group I, 22.03±0.60 MPa for group II, 19.59±0.65 MPa for group III, and 3.51±0.63 MPa for group IV. The materials in groups II and III were stronger than those in group I. However, the materials in group IV were weaker than those in group I.

Conclusion

An important dura mater graft property is biomechanical similarity to cranial human dura mater. This biomechanical study contributed to the future development of artificial dura mater substitutes with biomechanical properties similar to those of human dura mater.

The effect of spinal osteotomies on spinal cord tension and dural buckling: a cadaveric study

OBJECT

The standard surgical release of a tethered cord may result in recurrent scar formation and occasionally be associated with retethering. The application of spinal shortening procedures to this challenging problem potentially can reduce tension on the retethered spinal cord while minimizing the difficulties inherent in traditional lumbosacral detethering revision. Although spinal shortening procedures have proven clinical benefit in patients with a recurrent tethered cord, it is unclear how much shortening is required to achieve adequate reduction in spinal cord tension or what impact these osteotomies have on dural buckling.

METHODS

The authors calculated mean values from 4 human cadavers to evaluate the effect of 3 different spinal shortening procedures--Smith-Petersen osteotomy (SPO), pedicle subtraction osteotomy (PSO), and vertebral column resection (VCR)--on spinal cord tension and dural buckling. Three cadavers were dedicated to the measurement of spinal cord tension, and 3 other cadavers were devoted to myelography to measure dural buckling parameters.

RESULTS

The SPO was associated with a maximal decrease in spinal cord tension of 16.1% from baseline and no dural buckling with any degree of closure. The PSO led to a mean maximal decrease in spinal cord tension of 63.1% from baseline at 12 mm of closure and demonstrated a direct linear relationship between dural buckling and increasing osteotomy closure. Finally, VCR closure correlated with a mean maximal decrease in spinal cord tension of 87.2% from baseline at 10 mm of closure and also showed a direct linear relationship between dural buckling and increases in osteotomy closure.

CONCLUSIONS

In this cadaveric experiment, the SPO did not lead to appreciable tension reduction, while a substantial response was seen with both the PSO and VCR. The rate of tension reduction may be steeper for the VCR than the PSO. Adequate tension relief while minimizing dural buckling may be optimal with 12-16 mm of posterior osteotomy closure based on this cadaveric experiment.

Tethered cord syndrome: overview of diagnosis and treatment

This article covers the basis of tethered cord syndrome as a stretch-induced spinal cord disorder, including pathophysiology, signs and symptoms, imaging diagnosis, indication for surgical treatment, and surgical procedures. Anomalies that cause mechanical spinal cord tethering are listed, and the surgical untethering technique for each anomaly is described.

Surgical technique for idiopathic spinal cord herniation: the Hammock method. Technical note

Idiopathic spinal cord herniation is a rare disease, and surgical treatment is recommended for patients with motor deficits or progressive neurological symptoms. Surgery is performed to release and reposition the tethered spinal cord. In terms of repositioning and prevention of reherniation, various procedures have been proposed; enlargement of the ventral dural defect, primary closure of the defect with sutures, and insertion of a ventral patch for duraplasty. We treated 3 patients with idiopathic spinal cord herniation, using a ventral patch for duraplasty with an expanded polytetrafluoroethylene pericardial membrane (the Hammock method), and all 3 cases had good clinical outcome. The specific important technical aspects are described and illustrated. If this procedure is performed meticulously under the microscope by following the specific techniques, the Hammock method is safer and more effective for prevention of reherniation than simple enlargement of the dural defect.

Spinal duraplasty materials and hydrostasis: a biomechanical study

Object

Dural tears are a frequent complication of spinal surgery and contribute to significant morbidity. Occasionally, dural tears cannot be closed primarily and dural patch grafts must be utilized. No data exist on the comparative immediate hydrostatic strength of various patch materials used alone or with a biological adhesive in a spinal dural tear model. Thus, the authors conducted this study to determine the comparative effectiveness of various patch materials used with and without biological adhesive.

Methods

Twenty-four thoracic spines from calves were prepared with laminectomies and spinal cord evacuation, leaving the dura intact. Foley catheters were inflated on either side of a planned dural defect, and baseline hydrostasis was measured using a fluid column at 30, 60, and 90 cm of H2O. A standard dural defect (1 × 2 cm) was created, and 8 patches of each material (human fascia lata, Duragen, and Preclude) were sutured in place using 5-0 Prolene hemo-seal running sutures. Hydrostasis was again tested at the same pressures. Finally, a hydrogel sealant (Duraseal) was placed over the defect and hydrostasis was again tested. Results were analyzed with repeated measures ANOVA.

Results

The leakage rate increased significantly at each pressure tested for all conditions. There was no difference in leakage among the 3 patch materials at any of the pressures or for either condition (with or without sealant). All patch materials allowed significantly greater leakage than the intact condition at all pressures. The use of sealant reduced leakage significantly at the 30 and 60 mm Hg pressures to levels similar to the intact condition. At 90 mm Hg, leakage of the sealed construct was greater than at the intact condition but significantly less than without the use of sealant.

Conclusions

All 3 dural patch materials were of similar hydrostatic strength and allowed greater leakage than at the intact condition. The use of sealant reduced the amount of leakage at all pressures compared with patching alone but allowed more leakage than the intact state at a high hydrostatic pressure (90 mm Hg).

When only partial spinal cord detethering is possible

In most instances, initial surgery to untether a tethered spinal cord is successful. But what happens when it is not? The authors describe the case of a now 18-year-old woman with spina bifida in whom surgery for tethered cord was required on two occasions. In both instances, due to the extent of her underlying lesion and fibrous tissue, only partial detethering was possible without acutely sacrificing significant neurological function. The authors detail the patient's course and review the peer-reviewed scientific literature on outcomes in patients in whom only partial cord detethering is achieved. In their review of all case series and clinical studies pertaining to the surgical treatment of tethered cord syndrome identified during an online search of 2184 scientific abstracts and 2 major neurosurgery textbooks, excluding the present case, the authors identified 53 confirmed or presumed cases of incomplete detethering in eight articles, incorporating 390 patients, for an overall prevalence of roughly 13.6%. Although no investigators have reported statistical comparisons of outcomes in those in whom just partial and complete detethering has been achieved, the evidence generally suggests poorer outcomes in the former. Prospective multicenter studies addressing this important issue clearly are warranted. To date, the authors believe that incomplete detethering is grossly underreported in the medical literature.

Retethering of transected fatty filum terminales

OBJECT

Untethering of a tethered spinal cord (TSC) by transecting or removing a fatty filum terminale is a relatively simple procedure that can prevent or ameliorate neurological symptoms, and the postoperative prognosis is usually good. Progressive neurological deterioration caused by recurrent tethering has been rarely reported. The authors present their experience in cases in which a sectioned fatty filum terminale has become retethered.

METHODS

The authors retrospectively analyzed the surgical results of pediatric patients with fatty filum terminale-TSC treated by transection of the filum. The patients' charts were reviewed for demographic data, clinical presentation, surgical therapy, and follow-up data.

RESULTS

Of the 225 children who underwent TSC release by sectioning the fatty filum from 1992 to 2005, there were 6 patients (2.7%; 3 males, 3 females) in whom the fatty filum retethered. The mean age at the first diagnosis of TSC was 5.2 years (range 2 months-12.3 years). The mean duration from the first untethering procedure to retethering was 5.4 years. The mean age at the time of retethering was 10.6 years (range 7-17.5 years). Symptoms of retethering were urinary incontinence, low-back pain, difficulty walking, constipation, leg pain, and worsening foot deformity. Patients underwent cystometrography at the time retethering was indicated by increased bladder capacity, large post-void residual volume, decreased bladder capacity, increase in filling pressure, and poor sensation of filling. Magnetic resonance imaging revealed adherence of the rostral stump of the sectioned filum to the midline dorsal dural surface. All patients underwent the second untethering procedure. Four patients improved neurologically and experienced no retethering thereafter (mean follow-up period 5.5 years). Two patients experienced additional retethering after temporary improvement following the second untethering procedure.

CONCLUSIONS

Retethering of the spinal cord is a rare condition occurring after the sectioning of a fatty filum terminale. Awareness of this rare sequela is necessary for appropriate long-term management of TSC caused by a fatty filum terminale. Cystometrography is useful for detecting the lesion and confirming the diagnosis of retethering.

Spinal cord tethering following myelomeningocele repair

OBJECT

Symptom response to spinal cord untethering, and the impact of duraplasty and scoliosis on retethering, are poorly understood in tethering after myelomeningocele (MMC) repair. In this retrospective study, the authors examined the outcomes of children who developed first-time spinal cord tethering following MMC repair. The response of symptoms to untethering and the role of duraplasty and scoliosis in retethering are explored.

METHODS

The authors performed a review of 54 children with first-time symptomatic spinal cord tethering following MMC repair to determine the impact of untethering on symptoms, the impact of dural repair type on retethering, and the role of scoliosis on the prevalence and time to retethering.

RESULTS

The average patient age was 10.3 ± 4.9 years, and 44% were males. The most common presenting symptoms of tethered cord syndrome were urinary (87%), motor (80%), gait (78%), and sensory (61%) dysfunction. The average postoperative time to symptom improvement was 2.02 months for sensory symptoms, 3.21 months for pain, 3.50 months for urinary symptoms, and 4.48 months for motor symptoms, with sensory improvement occurring significantly earlier than motor improvement (p = 0.02). At last follow-up (an average of 47 months), motor symptoms were improved in 26%, maintained in 62%, and worsened in 11%; for sensory symptoms, these rates were 26%, 71%, and 3%, respectively; for pain, 28%, 65%, and 7%, respectively; and for urinary symptoms, 17%, 76%, and 7%, respectively. There was no difference in symptom response with type of dural repair (primary closure vs duraplasty). Symptomatic retethering occurred in 17 (31%) of 54 patients, but duration of symptoms, age at surgery, and type of dural repair were not associated with retethering. Scoliosis was not associated with an increased prevalence of retethering, but was associated with significantly earlier retethering (32.5 vs 61.1 months; p = 0.042) in patients who underwent additional untethering operations.

CONCLUSIONS

Symptomatic retethering is a common event after MMC repair. In the authors' experience, sensory improvements occur sooner than motor improvements following initial untethering. Symptom response rates were not altered by type of dural closure. Scoliosis was associated with significantly earlier retethering and should be kept in mind when caring for individuals who have had previous MMC repair.

Retethering of sectioned fibrolipomatous filum terminale in an adult: case report and review of the literature

BACKGROUND CONTEXT

Recurrent tethering of the spinal cord is a rare late complication after sectioning of a fibrolipomatous filum terminale that has only been reported in two pediatric cases.

PURPOSE

To report adult-onset recurrent tethering of the spinal cord after surgical sectioning of a fibrolipomatous filum terminale and review the literature in an attempt to identify similar cases.

STUDY DESIGN/SETTING

The study was designed to be a case report and literature review.

METHODS

A 21-year-old woman with a history of previous surgical repair for a tethered spinal cord secondary to a fibrolipomatous filum terminale presented with low back and right lower extremity pain, urinary frequency, and fecal incontinence. Progressive bladder and sphincter dysfunction was confirmed on urodynamic testing. Lumbar spine magnetic resonance imaging demonstrated a low-lying and dorsally positioned conus medullaris.

RESULTS

The patient underwent neurosurgical exploration of the previous site of sectioning with rerelease of the proximal fatty filum stump from dorsal dural adhesions. Postoperatively, her pain resolved, and her bowel and bladder control improved.

CONCLUSIONS

Sectioning of both abnormal and apparently normal fila has become a relatively common procedure in pediatric neurosurgery. As more children with this surgical history mature and present for neurosurgical consultation as adults, retethering must be considered in the differential diagnosis.

Foreign body reactions causing spinal cord tethering: a case-based update

BACKGROUND

Patients operated on for myelomeningocele (MMC) and lipomeningocele (LMC) can suffer from late functional worsening that, in many cases, is due to spinal cord tethering by the post-repair scarring process.

ILLUSTRATIVE CASES

In this case-based update, we report two patients operated on for MMC and LMC, respectively, who presented the clinical manifestations of spinal cord tethering, which we attributed to severe foreign body reactions to the materials used at their primary back surgery. In the first case, the cause of the tethering was an intense fibrotic scar around the silk suture used at the initial MMC repair, while in the second one, it was due to a fibrotic mesh containing the lyophilized dural graft implanted for LMC surgery. After a search of the current literature, we were unable to find cases of spinal cord tethering related to excessive scarring after dural repair with foreign materials used for the surgical correction of spinal dysraphism.

DISCUSSION AND CONCLUSIONS

The pathogenesis of spinal cord tethering in our instances closely relate with the histopathologically observed intense foreign body reaction around the materials used at the primary back surgery. We recommend avoiding as much as possible the use of foreign materials during the initial repair of spinal dysraphism.

Incidence of symptomatic retethering after surgical management of pediatric tethered cord syndrome with or without duraplasty

BACKGROUND

Cord retethering and other postoperative complications can occur after the surgical untethering of a first-time symptomatic tethered cord. It is unclear if using duraplasty vs. primary dural closure in the initial operation is associated with decreased incidence of either immediate postoperative complications or subsequent symptomatic retethering. It is also unclear if different etiologies are associated with different outcomes after each method of closure. We reviewed our pediatric experience in first-time surgical untethering of symptomatic tethered cord syndrome (TCS) to identify the incidence of postoperative complications and symptomatic retethering after duraplasty vs. primary closure.

MATERIALS AND METHODS

We retrospectively reviewed 110 consecutive pediatric (<18 years old) cases of first-time symptomatic spinal cord untethering at our institution over a 10-year period. Incidence of postoperative complications and symptomatic retethering were compared in cases with duraplasty vs. primary dural closure use.

RESULTS

Mean age was 5.7 +/- 4.8 years old. "Complex" etiologies included lipomyelomeningocele or prior lipomyelomeningocele repair in 22 (20%) patients, prior myelomeningocele repair in 35 (32%), and concurrent lumbosacral lipoma in 18 (16%). "Noncomplex etiologies" included fatty filum in 26 (24%) and split cord malformation in five (4%). Seventy-five (68%) cases underwent primary dural closure vs. 35 (32%) with duraplasty. Twenty-nine (26%) patients experienced symptomatic retethering at a median [interquartile range (IQR)] of 30.5 [20.75-41.75] months postoperatively. There was no difference in incidence of postoperative cerebrospinal fluid leak, surgical site infection, or median [IQR] length of stay in patients receiving primary dural closure [4 (5%), 7 (9%), and 5 (4-6) days, respectively] vs. duraplasty [3 (9%), 3 (9%), and 6 [5-8] days, respectively], p > 0.05. Complex etiologies were more likely to retether than noncomplex etiologies after primary closure (33.6% vs. 6.6%, p = 0.05) but not after duraplasty (13.7% vs. 5.4%, p = 0.33). Duraplasty graft type (polytetrafluoroethylene vs. bovine pericardium) was not associated with pseudomeningocele or retethering.

CONCLUSION

In our experience, the increased rate of symptomatic retethering observed with complex pediatric TCS (pTCS) etiologies after primary dural closures was not observed when duraplasty was instituted. Expansile duraplasty may be valuable specifically in the management of patient subgroups with complex pTCS etiologies.

Suboccipital decompression for Chiari I malformation: outcome comparison of duraplasty with expanded polytetrafluoroethylene dural substitute versus pericranial autograft

OBJECTIVE

Treatment failure for Chiari decompression is frequently associated with scarring, intradural adhesions, and recurrent loss of hindbrain space. While autograft has been our standard for hindbrain duraplasty, we investigated whether introducing anti-adhesive synthetic GORE PRECLUDE MVP Dura Substitute (expanded polytetrafluoroethylene [ePTFE] graft) was associated with improved patient outcomes.

MATERIALS AND METHODS

We retrospectively reviewed records of patients undergoing first-time suboccipital decompression/duraplasty for Chiari-I malformation utilizing ePTFE graft or pericranial autograft. Magnetic resonance imaging (MRI) at last follow-up was assessed for: (1) recurrent loss of dorsal hindbrain cerebrospinal fluid (CSF) space/CSF flow(cine-MR) at duraplasty site, (2) pseudomeningocele, or (3) syringomyelia improvement. Symptom recurrence warranting revision surgery was compared between cohorts.

RESULTS

Sixty-seven patients (age 11 +/- 5 years) underwent duraplasty with pericranial autograft (n = 40) or ePTFE graft (n = 27). Perioperative morbidity did not differ between cohorts. No patients receiving ePTFE graft experienced incisional CSF leak, surgical site infection, or symptomatic pseudomeningocele. At median 8 months postoperatively, all (100%) patients with ePTFE graft maintained physiological CSF flow/decompressed hindbrain CSF space on cine-MRI versus 32 (79%) patients receiving pericranial autograft (p < 0.05). Radiographic syrinx improvement occurred in 80% of patients with ePTFE graft and 52% of patients with pericranial autograft (median time to improvement: 5 vs 12 months, respectively, p < 0.05). At median 16 months postoperatively, four (10%) patients with pericranial autograft required revision decompression versus 0 (0%) patients with ePTFE graft (p = 0.090).

CONCLUSION

Duraplasty utilizing ePTFE graft was associated with improved maintenance of hindbrain space, accelerated syringomyelia improvement, and a trend toward decreased treatment failure versus pericranial autograft. Future studies of long-term outcome are warranted to confirm observed effects. Synthetic ePTFE graft is a safe alternative for duraplasty in the setting of Chiari malformation.

Tethered cord syndrome

Tethered cord syndrome is a clinical phenomenon resulting from anatomic restriction of the normal movement of the spinal cord or vascular compromise leading to hypoxia of its distal structures. Tethering can be acquired (secondary) or congenital (primary). This article presents the relevant embryology, primary and secondary causes of tethering, clinical presentations, the treatment of specific entities, indications and options for Tethered cord syndrome is a clinical phenomenon resulting from anatomic restriction of the normal movement of the spinal cord or vascular compromise leading to hypoxia of its distal structures. Causes of tethering can be acquired (secondary) or congenital (primary). This article presents the relevant embryology, primary and secondary causes of tethering, clinical presentations, the treatment of specific entities, indications and options for surgical treatment, and surgical complications.

Tethered cord syndrome: an updated review

Tethered cord syndrome (TCS) is a diverse clinical entity characterized by symptoms and signs which are caused by excessive tension on the spinal cord. The majority of cases are related to spinal dysraphism. TCS can present in any age group, and presentations differ according to the underlying pathologic condition and age, with pain, cutaneous signs, orthopedic deformities and neurological deficits being the most common. Surgical untethering is indicated in patients with progressive or new onset symptomatology attributable to TCS. The surgical strategy aims to release the tethering structure and thus the chronic tension on the cord. Early operative intervention is associated with improved outcomes. Pain relief is accomplished in almost all cases. Realistic surgical goals include relief of pain and stabilization of neurological function, although improvement in function is often seen. Cord untethering can also halt the progression of scoliosis. The benefits of surgery are debated in asymptomatic patients and patients with normal imaging.

Effectiveness and handling characteristics of a three-layer polymer dura substitute: a prospective multicenter clinical study

Object

The goal of this study was to assess the effectiveness and handling characteristics of a dura substitute composed of two outer layers of expanded polytetrafluoroethylene (PTFE) and a middle layer consisting of an elastomeric fluoropolymer.

Methods

In a prospective multicenter study, the dura substitute was implanted using a standard technique in 119 patients undergoing cranial or spinal surgery requiring duraplasty. Intraoperative assessments of the dura patch consisted of testing for cerebrospinal fluid (CSF) leakage employing the Valsalva maneuver and a surgeon’s standard evaluation of the handling characteristics of the device. Postoperative assessments conducted during a mean follow-up time of 15.7 months (range 0.3–45.6 months) consisted of physical examinations, routine computed tomography (CT) or magnetic resonance (MR) imaging studies, and histological studies of any removed dura patches.

The mean age of the 119 patients was 40 years (range < 1–81 years). The dura substitute was implanted cranially in 102 patients and spinally in 17. Intraoperative assessment including the Valsalva maneuver led to application of additional sutures in 17 patients. Handling features were rated very good to excellent. Postoperative clinical evaluation resulted in 79 excellent and 18 good results. Imaging studies (MR imaging studies in 69 patients and CT studies in 34 patients) showed no adhesions in 87 patients and minimal adhesions in seven patients (the dura was not visualized in nine patients). Postoperative complications occurred in 12 patients. There were six cases of CSF leakage, three cases of extradural hematoma, one case of arachnoid fibrosis after decompression of a Chiari malformation Type I, and two cases of infection. Eight (7%) of these complications were potentially related to the dura patch.

Conclusions

In a large, multicenter clinical study of the use of an expanded-PTFE–containing dura substitute, the device was found to be easy to handle and implant. No serious dura patch–related intraoperative adverse events were observed. Postoperatively, there were no major sealing problems or long-term complications. In two cases the patch had to be removed due to fibrosis and infection. The three-layer polymer dura substitute appears to be safe and effective in minimizing CSF leakage and adhesion formation, and its use avoids any risk of prion disease transmission.

Vertebral column subtraction osteotomy for recurrent tethered cord syndrome in adults: a cadaveric study

OBJECT

The standard treatment for lumbosacral tethered cord syndrome (TCS) in adults is surgical detethering. In patients with recurrent TCS, additional detethering operations are associated with increased risk of complications and subsequent scar formation. The authors studied the effect of undertaking a vertebral column subtraction osteotomy (VCSO) at the thoracolumbar junction to shorten the vertebral column and reduce neural element tension.

METHODS

A model of TCS, developed in fresh-frozen human cadavers, was evaluated in three experiments. In Experiment 1, VCSO of 20 to 25 mm was performed at the T11-12 level. The vertebral column was sequentially shortened and the reduction in tension was measured separately in the terminal filum and the L-1 to S-3 or S-4 nerve roots. In Experiments 2 and 3 the reduction in tension was measured in the spinal cord after a VCSO and after simulating a traditional detethering operation. Vertebral column shortening produced tension reduction in all experiments. Tension decreased to less than 0.6 g in the terminal filum, L1-S3/4 nerve roots, and spinal cord after closure of a 20- to 25-mm VCSO. The mean +/- standard deviation of the deltatension/deltadistance was -0.242 +/- 0.019 g/mm for the terminal filum, -0.246 +/- 0.019 g/mm for the lumbar nerve roots, and -0.216 +/- 0.040 g/mm for the sacral nerve roots. A simulated traditional detethering operation required significant neural element release (detethering) to achieve spinal cord tension reduction equivalent to VCSO.

CONCLUSIONS

A VCSO significantly reduced neural tension at the thoracolumbar junction. This novel procedure may provide an alternative to traditional surgical detethering when scarring is excessive and the risk of complications and retethering are high.

two-stage operation for resection of spinal cord astrocytomas: technical case report of three cases

OBJECTIVE AND IMPORTANCE

Surgery for excision of intramedullary spinal cord tumors without increasing neurological deficit is one of the more difficult operations in spinal surgery. In particular, infiltrating astrocytomas without a clear cleavage between the tumor and normal spinal cord parenchyma are difficult to remove totally without producing additional neurological impairment. In this study, we describe a two-stage resection facilitating total resection of intramedullary tumors.

CLINICAL PRESENTATION

Three cases of spinal cord astrocytomas were treated using a two-staged method.

TECHNIQUE

The first surgery included myelotomy, biopsy and duroplasty. A thin expanded polytetrafluoroethylene sheet was placed between the dorsal surface of the spinal cord and dura mater to prevent adhesions. Two or 3 weeks after surgery, a second surgery was performed to remove the now exophytic tumor.

RESULTS

Magnetic resonance imaging scans showed exophytic extrusion of the tumor in all three cases before the second operation. In each patient, we were able to carry out gross total removal of the tumors without additional neurological deficit except for transient joint position sense loss in one case. All three patients remain neurologically stable without evidence of tumor recurrence more than 3 years after surgery.

CONCLUSION

A two-stage operation may enhance the surgeon's ability to completely resect extensive low-grade spinal cord astrocytomas and, at the same time preserve neurological function.

Partial physeal growth arrest treated by bridge resection and artificial dura substitute interposition

We treated four cases of partial physeal growth arrest by resecting the bone bridge and interposing an expanded polytetrafluoroethylene membrane, which has minimal tissue response. We evaluated three cases with sufficiently long follow-up. No apparent recurrence of the bone bridge and no limb length discrepancy occurred in any of the cases. No remodeling after the operation occurred. In one case, which underwent this operation and corrective osteotomy of the proximal tibia, slight recurrence of the varus deformity occurred which was detected only by radiographs, and did not compromise the alignment of the leg. There were no complications.

Postoperative fibrosis after surgical treatment of the porcine spinal cord: a comparison of dural substitutes

Object. Postoperative adhesion- and fibrosis-induced spinal cord tethering is not uncommon and may be associated with delayed clinical sequelae. Multiple dural substitutes have been used in surgery without a full appreciation of the grafts' adverse effects. The authors conducted a comparative animal experimental study to evaluate the degree of chronic inflammatory reactions, adhesions, and fibrosis caused by the use of four dural substitutes—Surgicel, Durasis, DuraGen, and Preclude.

Methods. Twenty-six pigs weighing 30 to 40 kg underwent a two-level lumbar laminectomy (a midline durotomy, implantation of a 2-cm dural substitute in the subarachnoid space, and watertight dural closure). After 8 weeks the animals were killed, and two independent neuropathologists blinded to the dural substitute group evaluated several sites along the implants, providing descriptions and quantitative scoring of fibrosis, chronic inflammatory reactions, foreign-body reactions, and spinal cord changes. Kruskal—Wallis one-way analysis of variance for ranks corrected for multiple comparisons was used to examine differences among the materials.

Conclusions. The DuraGen dural substitute produced the least amount of inflammation in the subarachnoid space and Preclude generated the most (p < 0.001). Surgicel and DuraGen were completely resorbed on histological sections, but both produced some inflammation, which diminished gradually from the dural implant center. Histological evaluation of the nonresorbed grafts demonstrated that Durasis caused the least degree of inflammatory cell infiltration (p < 0.001). The Preclude dural substitute consistently demonstrated encapsulation and arachnoidal reaction. There was no evidence of implant-related adverse effects on the underlying pia mater and white matter regardless of the substitute type.

Seprafilm superior to Gore-Tex in the prevention of peridural fibrosis

OBJECT

This is an investigation into the effects of two barrier membranes in the prevention of peridural fibrosis in an animal model.

METHODS

Seprafilm or Gore-Tex was applied to a laminectomy defect overlying the dura mater in rats separated into treatment groups. A third group of rats underwent laminectomy only and served as controls. Two months postoperatively a histological study was performed to compare the amount of scar tissue in each group. The gross dissection demonstrated that both membranes created a controlled dissection plane, facilitated access to the epidural space, and provided a reduction in the amount of tissue adhering to the dura mater. Statistically, Seprafilm was superior to Gore-Tex in preventing peridural fibrosis (p < 0.05).

CONCLUSIONS

Seprafilm can prevent peridural fibrosis better than Gore-Tex and can be used in humans in spinal surgery.

Prevention of postoperative posterior tethering of spinal cord after resection of ependymoma

OBJECT

The authors evaluated an alternative method to avoid postoperative posterior tethering of the spinal cord following resection of spinal ependymomas.

METHODS

Twenty-five patients with spinal ependymoma underwent surgery between 1978 and 2002. There were 16 male and nine female patients whose ages at the time of surgery ranged from 14 to 64 years (mean 41.8 years). The follow-up period ranged from 6 to 279 months (mean 112.4 months). In the initial 17 patients (Group A), the procedure to prevent arachnoidal adhesion consisted of the layer-to-layer closure of three meninges and laminoplasty. In the subsequently treated eight patients (Group B), the authors performed an alternative technique that included pial suturing, dural closure with Gore-Tex membrane-assisted patch grafting, and expansive laminoplasty. In Group A, postoperative adhesion was radiologically detected in eight cases (47%), and delayed neurological deterioration secondary to posterior tethering of the cord was found in five cases. In Group B, there was no evidence of adhesive posterior tethering or delayed neurological deterioration. A significant intergroup statistical difference was demonstrated for radiologically documented posterior tethering (p < 0.05, Fisher exact test). Moreover, patients with radiologically demonstrated posterior tethering suffered a significant delayed neurological functional deterioration (p < 0.01, Fisher exact test).

CONCLUSIONS

This new technique for closure of the surgical wound is effective in preventing of postoperative posterior spinal cord tethering after excision of spinal ependymoma.

Expanded polytetrafluoroethylene membrane for prevention of adhesions in patients undergoing external decompression and subsequent cranioplasty

Cranioplasty performed after external decompression for brain swelling may be difficult because of the development of adhesions between the temporal muscle and the dura. Membranes composed of expanded polytetrafluoroethylene (ePTFE) were inserted at external decompression to prevent such adhesions. The ePTFE membranes were placed suturelessly between the temporal muscle and the dura, covering the proximal portion of the temporal muscle at the sphenoidal ridge and the dural suture line. In addition, part of the membrane was placed directly below the skin incision to allow easy visualization at subsequent cranioplasty in 10 patients. Cranioplasty was performed 38 to 126 days (mean 63.9 days) after external decompression. No adhesions were observed, either between the ePTFE membranes and the dura, or between the membranes and the temporal muscle. No temporal muscle and dural injuries occurred during cranioplasty, and no patient showed signs of infection. Mean operating time was 71.0 minutes and mean blood loss was 75.2 ml. Sutureless insertion of ePTFE membranes at external decompression increases the ease and safety of subsequent cranioplasty, decreases operating time and blood loss, and avoids injury to the temporal muscle and dura.

Dural substitute for long-term imaging of cortical activity in behaving monkeys and its clinical implications

We present a transparent silicone dural substitute, which we have been using for the last 7 years for imaging cortical dynamics in awake behaving monkeys. This substitute enabled us to record optically for more than a year intrinsic or voltage sensitive dye signals. It is thin and elastic enough to allow microelectrode to pass through without any damage, using full visual control to target the electrode to the desirable recording site. This implant has proved crucial for maintaining the cortex in a good physiological condition and for preserving its optical characteristics that are necessary for optical imaging. We describe the details of the surgical implantation of the silicone dural substitute, the maintenance of the exposed cortex over long periods of time, the cortical reaction to this implant and its possible clinical implications in humans, and the rehabilitation procedure in monkeys.

Inhibition of epidural scar tissue formation after spinal surgery: external irradiation vs. spinal membrane application

PURPOSE

The scar tissue that forms after lumbar dissection is a severe complication and a cause of lumbar and radicular pain. It was recently shown that radiotherapy could inhibit peridural fibrosis after laminectomy. In this study, the efficiency of external irradiation was compared with spinal membrane application.

METHOD AND MATERIALS

Thirty male New Zealand rabbits underwent L5 laminectomy. Ten rabbits each received a single fraction of 900-cGy external irradiation administered by 9-MeV electron beam 24 h after the surgery. Ten other rabbits each had spinal membrane applied during laminectomy. The remaining 10 rabbits constituted the control group. All of the rabbits were killed 30 days after the laminectomy. Axial histologic sections through the laminectomy defect were evaluated. Each specimen was scored for the extent and density of fibrosis and arachnoidal adherence.

RESULTS

The extent and density of fibrosis and arachnoidal adherence differed significantly between the control group and the treatment groups (p < 0.05). However, the extent and density of fibrosis and arachnoidal adherence did not differ significantly between the spinal membrane and irradiation groups (p > 0.05).

CONCLUSION

This preliminary study showed that high-single-fraction/low-total-dose administered postoperatively can successfully inhibit postsurgical epidural fibrosis as effectively as applied spinal membrane.

Disturbances of cerebrospinal fluid flow attributable to arachnoid scarring cause interstitial edema of the cat spinal cord

OBJECTIVE

Spinal arachnoid scarring may be caused by trauma, inflammation, surgery, spinal instability, degenerative diseases, or malformations and may lead to progressive neurological deficits and syringomyelia. We wanted to investigate the effects of focal arachnoid scarring in the cervical spinal canal of cats on pressures in the subarachnoid space and spinal cord tissue, as well as on spinal cord histological features.

METHODS

Twenty-nine adult cats were used for this study. Nine animals served as control animals, whereas 20 animals received a focal arachnoid scar at C1-C2, which was produced by placement of a kaolin-soaked fibrin sponge on the posterior surface of the spinal cord. After 4 months, pressure recordings above and below the scar, in the subarachnoid space and spinal cord, were performed. Elasticity measurements were performed with small bolus injections. Morphometric analyses of brain and ventricle volumes, sizes of the central canal, and sizes of the perivascular spaces in gray and white matter were also performed.

RESULTS

No animal developed clinical or neurophysiological evidence of neurological symptoms at any time. In the kaolin-treated group, pressure recordings revealed a significant increase in the subarachnoid pressure at C1, because of the cerebrospinal fluid flow obstruction. Pressure gradients tended to increase at all measuring points. A significant difference was detected between the spinal cord and subarachnoid space at C2, where the intramedullary pressure exceeded the subarachnoid pressure. Elasticity was significantly increased in the spinal cord at C2. Intracranially, no evidence of hydrocephalus was observed. In the spinal cord, perivascular spaces were significantly enlarged in the posterior white matter above the arachnoid scar and in the central gray matter below the area of scarring in the cervical cord.

CONCLUSION

Arachnoid scarring at C1-C2 produces an interstitial type of edema in the central gray matter below the area of scarring in the cat cervical cord, because of altered cerebrospinal fluid and extracellular fluid flow dynamics. These changes may be interpreted as the initial stage in the development of syringomyelic cavities.

Surgical management of syringomyelia associated with spinal adhesive arachnoiditis

The authors describe a new surgical technique to minimise the postoperative recurrence of adhesion after microlysis of adhesion to treat syringomyelia associated with spinal adhesive arachnoiditis. A 47 year old male presented with numbness of the lower extremities and urinary disturbance and was demonstrated to have a case of syringomyelia from C1 to T2 which was thought to be secondary to adhesive spinal arachnoiditis related to a history of tuberculous meningitis. Following meticulous microlysis of the adhesions, maximal expansion of a blocked subarachnoid space was performed by expansive duraplasty with a Gore-Tex surgical membrane, expansive laminoplasty and multiple tenting sutures of the Gore-Tex graft. Postoperatively, the syringomyelia had be en completely obliterated and improvement of the symptoms had been also achieved. The technique described may contribute to improvement of the surgical outcome following arachnoid dissection by maintaining continuity of the reconstructed subarachnoid space.

Examination of the safety and efficacy of an absorbable dura mater substitute (Dura Patch) in normal applications in neurosurgery

BACKGROUND

The possibility of the transmission of Creutzfeldt-Jakob disease and slow virus infection (HIV) by cadaveric dura implants makes it necessary to find synthetic, absorbable substitute materials for plastic reconstruction of the dura mater. Dura-Patch is a bilayered composite of a dyed polydioxanone (PDS) foil and an undyed fleece of Polyglactin 910 (Vicryl) and PDS threads, known to be completely resorbable.

METHODS

The Dura-Patch was tested prospectively in 101 patients undergoing 75 supratentorial, 20 infratentorial, and 6 spinal operations in seven different neurosurgical departments. Fixation of the substitute was either by suturing, gluing, or both. The specific tissue properties were investigated considering biocompatibility, form, size, adaptability, fixation, scarring, and resistance to CSF tearing with the aid of hematologic and neurological parameters, CCT, and/or MRI scanning up to 6 months postoperatively.

RESULTS

A total of 76 of 101 patients completed the study (75%). The biocompatibility of the Dura-Patch with timely absorption of the implant material was excellent without exception. There was no notable local scarring and no infections. Transient CSF cushioning in 12.9% of the patients was in keeping with the normal range. The elasticity and flexibility of the Dura-Patch was rated as "good" in 90% and was still better when the size of the implant increased, with an overall rating of handling as "good" or "excellent" in 97% of all operations.

CONCLUSIONS

The new absorbable Dura-Patch showed itself to be suitable for both plastic dura reconstruction and plastic extension of the subdural space with primary, watertight, germproof closure in routine intracranial and spinal tumor removal.

The use of Gore-Tex membrane for adhesion prevention in tethered spinal cord surgery: technical case reports

OBJECTIVE

The incidence of retethering caused by postoperative adhesions at the repair site after initial tethered spinal cord surgery is not uncommon. To assess the effectiveness of a Gore-Tex membrane in preventing these adhesions, only clinical radiological and experimental animal evaluation has been reported. In this report, we describe two cases in which Gore-Tex membrane was implanted at the initial untethering surgery and in which we were able to confirm the real effectiveness of the Gore-Tex membrane during a second operation.

METHODS

In the first patient, Gore-Tex membrane was used for dural repair in the untethering surgery of the split spinal cord malformation. Because of the suspicion of a thickened filum terminale, repeated surgery was indicated 10 months after the initial procedure. In the second patient, Gore-Tex membrane was implanted during the initial untethering surgery for a lipomyeloschisis and a dermal sinus. Because of a persistent fistula of the dermal sinus, a second operation was necessary 1 year after the first operation.

RESULTS

During the repeated surgery, a thorough inspection of the implanted Gore-Tex membrane revealed no adhesions between the Gore-Tex membrane and the intradural content in both cases.

CONCLUSION

We support the use of Gore-Tex membrane in the prevention of postoperative dural adhesions in the repair of spinal dysraphism.

Prevention of arachnoiditis and postoperative tethering of the spinal cord with Gore-Tex surgical membrane: an experimental study with rats

OBJECTIVE

Arachnoidal adhesions and inflammation were evaluated in 72 rats after spinal dural repair with one of three materials, i.e., Gore-Tex surgical membrane, collagen-coated Vicryl mesh, or lyophilized spinal dural allograft.

METHODS

Laminectomy at L1 was performed, and then a 3- x 4-mm segment of spinal dura mater and arachnoid membrane was excised. After implantation of the dural substitute, the animals were divided into normal and injured groups. In the injured group, a spinal cord injury was produced at the midpoint of the duraplasty site by the clip compression technique, with 25-g force for 1 minute. Neurological performance was assessed by the inclined plane technique, and groups of rats were killed at 8 to 24 weeks after surgery. The spinal column was removed en bloc and processed for histological examination.

RESULTS

There were no differences in neurological function among the three dural substitutes in either injured or noninjured rats. However, there were major differences among the groups in the incidence and severity of arachnoid adhesions and tethering. The neural tissue was bound to a thick neomembrane surrounding the lyophilized dural allograft and the collagen-coated Vicryl mesh. In contrast, the Gore-Tex surgical membrane induced only a thin membranous adhesion, which was loose and flexible. The inflammatory and foreign body response was most pronounced in rats treated with collagen-coated Vicryl mesh, at 8 and 24 weeks.

CONCLUSION

In the present study, Gore-Tex surgical membrane was a very good material for the surgical repair of spinal dural defects. Additional experimental studies are required to compare Gore-Tex membrane with autologous tissues.

Latissimus dorsi flap procedures to cover myelomeningocele in utero: a feasibility study in human fetuses

There is experimental and clinical evidence that in utero repair of myelomeningocele (MMC) may preserve neurological function. In five aborted human fetuses (gestational age, 18 to 29 weeks), the authors tested whether proximally and distally based latissimus dorsi flaps (LDF) can be used to cover MMC lesions. Fetal soft tissues were developed enough to allow surgical handling, preparation of both flap types was technically easy, and the vascular pedicles could be preserved. The proximally pedicled LDF was suitable to cover the upper spine from lower cervical to lower thoracic levels, whereas the distally pedicled LDF was suitable to cover the spine between lower thoracic and lower sacral levels. These results suggest that various LDF procedures are technically feasible in early gestational human fetuses and could be used for in utero repair of MMC.

Tethered thoracic cord resulting from spinal cord herniation

Tethered cord syndrome (TCS) usually involves tethering of the lower cord at the conus medullaris from dural abnormalities, but may occur after spinal cord herniation. A tethered thoracic spinal cord is rare. We present an unusual case of a 30-year-old woman with a history of myelopathy presumed to be secondary to T6 cord compression resulting from T6-T8 arachnoid cyst. She continued to deteriorate after partial excision of the cyst. Repeat magnetic resonance imaging suggested recurrence of the presumed arachnoid cyst with cord compression and showed tethering at T6-T8. Surgical exploration revealed myelocele with cord herniation through the anterior thoracic dura. Pathologic diagnosis showed neural tissue with gliosis. After physical therapy treatments, the patient had increased lower extremity strength, ambulated with a cane, and regained some bladder control. Progressive myelopathy may represent tethering of the cord resulting from cord herniation. Early recognition of TCS, even in patients with minimal neurologic deficits, could prevent progressive disability.