Intracranial hypotension following scoliosis surgery: dural penetration of a thoracic pedicle screw

Reoperation for Misplaced Pedicle Screws: A Multicenter Retrospective Study

STUDY DESIGN

A multicenter retrospective analysis.

OBJECTIVE

This study aims to investigate reoperation of misplaced pedicle screws (MPSs) after posterior spinal fusion (PSF), focusing on neurological complications.

SUMMARY OF BACKGROUND DATA

The management strategy for MPSs and the clinical results after reoperation are poorly defined.

MATERIALS AND METHODS

Subjects were 10,754 patients (73,777 pedicle screws) who underwent PSF at 11 hospitals over 15 years. The total number of reoperations for MPS and patient clinical data were obtained from medical records at each hospital.

RESULTS

The rate of reoperation for screw misplacement per screw was 0.17%. A total of 69 patients (mean age, 67.4±16.5 yr) underwent reoperation because of 82 MPS. Reasons for reoperation were neurological symptoms (58 patients), contact with vessels (5), suboptimal bone purchase (4), and misplacement recognized during operation (2). Neurological symptoms were the major reason for reoperation in cervical (5/5 screws, 100%) and lumbo-sacral (60/67 screws, 89.6%) regions. Contact with vessels was the major reason for reoperation in the thoracic spine (6/10 screws, 60.0%). We further evaluated 60 MPSs in the lumbo-sacrum necessitating reoperation because of neurological symptoms. The majority of MPSs necessitating reoperation were placed in the lower lumbar spine (43/60 screws, 71.7%). The mean pedicle breach tended to be larger in the incomplete recovery group than in the complete recovery group (6.8±2.4 vs . 5.9±2.2 mm, P =0.146), and the cutoff value resulting in incomplete resolution was 5.0 mm. Multivariate analysis revealed that medial-caudal breaches ( vs . medial breach, odds ratio: 25.8, 95% confidence interval: 2.58-258, P =0.0057) and sensory and motor disturbances ( vs . sensory only, odds ratio: 8.57, 95% confidence interval: 1.30-56.6, P =0.026) were significant factors for incomplete resolution of neurological symptoms.

CONCLUSIONS

After reoperation, 70.1% of the patients achieved complete resolution of neurological symptoms. Factors associated with residual neurological symptoms included sensory and motor disturbance, medial-caudal breach, and larger pedicle breach (>5 mm).

Intraoperative 3D Imaging Reduces Pedicle Screw Related Complications and Reoperations in Adolescents Undergoing Posterior Spinal Fusion for Idiopathic Scoliosis: A Retrospective Study

Widely used surgical treatment for adolescent idiopathic scoliosis (AIS) is posterior spinal fusion using pedicle screw instrumentation (PSI). Two-dimensional (2D) or three-dimensional (3D) navigation is used to track the screw positioning during surgery. In this study, we evaluated the screw misplacement, complications, and need for reoperations of intraoperative 3D as compared to 2D imaging in AIS patients. There were 198 adolescents, of which 101 (51%) were evaluated with 2D imaging and 97 (49%) with 3D imaging. Outcome parameters included radiographic correction, health-related quality of life (HRQOL), complications, and reoperations. The mean age was 15.5 (SD 2.1) years at the time of the surgery. Forty-four (45%) patients in the 3D group and 13 (13%) patients in the 2D group had at least one pedicle screw repositioned in the index operation (p < 0.001). Six (6%) patients in the 2D group, and none in the 3D group had a neurological complication (p = 0.015). Five (5%) patients in the 2D group and none in the 3D group required reoperation (p = 0.009). There were no significant differences in HRQOL score at two-year follow-up between the groups. In conclusion, intraoperative 3D imaging reduced pedicle screw-related complications and reoperations in AIS patients undergoing PSI as compared with 2D imaging.

Pseudohypoxic Brain Swelling After Uncomplicated Lumbar Decompression and Fusion for Spondylolisthesis

BACKGROUND

Pseudohypoxic brain swelling (PHBS), also known as postoperative intracranial hypotension-associated venous congestion, is a rare complication after neurosurgery characterized by rapid and often severe postoperative deterioration in consciousness and distinct imaging findings on brain magnetic resonance imaging. Imaging findings associated with PHBS include computed tomography and magnetic resonance imaging findings that resemble hypoxic changes and intracranial hypotensive changes in basal ganglia and thalamus, telencephalic, and infratentorial regions without notable changes in intracranial vasculature.

CASE DESCRIPTION

This report describes the case of an L4-5 microdiskectomy with posterior decompression and fusion complicated by clinical and radiographic findings resembling PHBS without a known intraoperative durotomy.

CONCLUSIONS

Spine surgeons should be alerted to the possibility that PHBS may occur in patients even after an operation without known durotomy or cerebrospinal fluid leakage and with spontaneous clinical resolution unrelated to suction drainage changes or epidural blood patches.

Medially misplaced pedicle screws in patients without neurological deficits following scoliosis surgery: to observe or to remove?

PURPOSE

This study investigated whether pedicle screws medially misplaced into the spinal canal without neurological complications should be removed or not.

METHODS

A total of 86 patients with scoliosis that underwent spinal fusion using 988 pedicle screws were retrospectively reviewed after a minimum follow-up of 2 years. The inclusion criteria were: (1) patients without outstanding problems during the insertion of pedicle screws, (2) patients without neurological deficits either intraoperatively or postoperatively, and (3) patients that had all implants removed after bone union upon the request of the patient. Medial perforations were evaluated using immediate postoperative helical CT images and classified into three grades: grade 1 (0-2 mm), grade 2 (2-4 mm), and grade 3 (over 4 mm). All unexpected events were recorded at the time of removal.

RESULTS

CT images obtained 2 years postoperatively exhibited neither loosening of screws nor pseudoarthrosis in all patients. CSF leakage from screw holes were recognized in 3 of 87 medially misplaced screws (3.4 %). There was no CSF leakage in grade 1 (35 screws), one CSF leakage (2.5 %) in grade 2 (40 screws), and two (16.7 %) in grade 3 (12 screws). No neurological abnormalities occurred either intraoperatively or postoperatively.

CONCLUSION

This study indicated that screws medially misplaced at a distance greater than 2 mm, especially 4 mm, may be a cause of negative effects on the neural structure and should be removed during the early phase of the postoperative period, even among patients without postoperative neurological abnormalities.

Intracranial hypotension: clinical presentation, imaging findings, and imaging-guided therapy

PURPOSE OF REVIEW

To illustrate clinical presentations, imaging findings, and diagnostic and therapeutic approaches associated with various conditions of intracranial hypotension.

RECENT FINDINGS

Intracranial hypotension occurs spontaneously, following (lumbar) dural puncture, accidental dural opening, or excessive surgical cerebrospinal fluid drainage. The typical clinical manifestation - orthostatic headache - may be masqueraded by atypical clinical findings, including coma, frontotemporal dementia, leptomeningeal hemosiderosis-associated symptoms, and others. MRI signs are highly specific, but the imaging strategy to search for spinal cerebrospinal fluid leaks (none, computed tomography myelography, magnetic resonance myelography with gadolinium, digital subtraction myelography) is a matter of debate. The same is true for the mode of treatment (bed rest, blind, fluoroscopy or computed tomography-guided epidural blood patching, fibrin patching, surgery).

SUMMARY

Clinical presentation as well as diagnostic and therapeutic approaches in intracranial hypotension are very heterogenous.

Neuromonitoring with pulse-train stimulation for implantation of thoracic pedicle screws: a blinded and randomized clinical study. Part 2. The role of feedback

Object

The authors have reported in Part 1 of this study on a novel neuromonitoring test for the prevention of medial malpositioning of thoracic pedicle screws. In the present paper they examine the impact of providing the results of the test as intraoperative feedback to the surgical team.

Methods

This is the second part of a 2-part report of a prospective, blinded and randomized neuromonitoring study designed to lower the incidence of medially malpositioned thoracic pedicle screws. Details of the neuromonitoring technique and data supporting the alarm criteria used are contained in the companion article (Part 1). For the majority of pedicle screw placements, intraoperative test results were withheld from the study team (that is, the team members were blinded to the test results). However, for a limited number of pedicle sites the authors provided one of 2 forms of testing feedback to the surgical team: 1) “break the blind” feedback, if testing suggested that screw placement would result in direct contact between screw and the dura mater; and 2) “planned” feedback, beginning during the later stages of the study and provided for 50% of pedicle sites. Feedback gave the surgeon the opportunity to adjust the trajectory that the screw would ultimately take within the pedicle. The final screw position relative to the pedicle's medial wall for all sites in which feedback was withheld from the surgical team was compared with the screw position for those sites in which either form of feedback (“break the blind” or “planned”) was provided to and acted upon by the surgical team.

Results

Of the 820 pedicle tracks tested among the 71 surgical cases included in this study, a total of 684 were operated upon without any form of feedback. Planned feedback was provided for an additional 107 pedicle tracks, of which 15 triggered an intraoperative alarm (evoked electromyogram response in leg muscles to stimulus intensity ≤ 10 mA) leading to a warning to the surgical team of a medially biased pedicle track. Finally, the blind was broken 29 times, in each case when testing revealed a particularly low threshold (≤ 4 mA) for evoked responses in leg muscles when stimulating along the pedicle track with the ball-tipped probe. As detailed in the companion paper to this one, there were 32 screws with threads lying at least 2 mm medial to the pedicle wall. In all 32 instances (100%), either these screws were in the “no feedback” category (n = 29) or they were in a feedback category but the surgeon elected to not revise the pedicle-track trajectory. Two patients returned to the operating room for revision of screw placements because the screws were encroaching upon the central canal; the pedicle tracks for these screws had been in the “no feedback” category.

Conclusions

This is the first blinded and randomized study to prove that implementing a novel neuromonitoring strategy during placement of thoracic pedicle screws can significantly reduce the incidence of clinically relevant thoracic pedicle screw medial malpositioning.

Neuromonitoring with pulse-train stimulation for implantation of thoracic pedicle screws: a blinded and randomized clinical study. Part 1. Methods and alarm criteria

Object

Reports of the accuracy of existing neuromonitoring methods for detecting or preventing medial malpositioning of thoracic pedicle screws have varied widely in their claimed effectiveness. The object of this study was to develop, test, and validate a novel neuromonitoring method for preventing medial malpositioning of pedicle screws in the thoracic spine during surgery.

Methods

This is a prospective, blinded and randomized study using a novel combination of input (4-pulse stimulus trains delivered within the pedicle track) and output (evoked electromyography from leg muscles) to detect pedicle track trajectories that—once implanted with a screw—would cause that screw to breach the pedicle's medial wall and encroach upon the spinal canal. For comparison, the authors also used screw stimulation as an input and evoked electromyogram from intercostal and abdominal muscles as output measures. Intraoperative electrophysiological findings were compared with postoperative CT scans by multiple reviewers blinded to patient identity or intraoperative findings.

Results

Data were collected from 71 patients, in whom 802 screws were implanted between the T-1 and L-1 vertebral levels. A total of 32 screws ended up with screw threads encroaching on the spinal canal by at least 2 mm. Pulse-train stimulation within the pedicle track using a ball-tipped probe and electromyography from lower limb muscles correctly predicted all 32 (100%) of these medially malpositioned screws. The combination of pedicle track stimulation and electromyogram response from leg muscles proved to be far more effective in predicting these medially malpositioned screws than was direct screw stimulation and any of the target muscles (intercostal, abdominal, or lower limb muscles) we monitored. Based on receiver operating characteristic analysis, the combination of 10-mA (lower alarm) and 15-mA stimulation intensities proved most effective for detection of pedicle tracks that ultimately gave rise to medially malpositioned screws. Additional results pertaining to the impact of feedback of these test results on surgical decision making are provided in the companion report.

Conclusions

This novel neuromonitoring approach accurately predicts medially malpositioned thoracic screws. The approach could be readily implemented within any surgical program that is already using contemporary neuromonitoring methods that include transcranial stimulation for monitoring motor evoked potentials.

Symptomatic pneumocephalus associated with lumbar dural tear and reverse trendelenburg positioning: a case report and review of the literature

Symptomatic pneumocephalus is a rare complication of degenerative lumbar spine surgery. This is a case report of a patient who developed transient diplopia associated with pneumocephalus following lumbar spine surgery complicated by a dural tear. The diplopia improved as the pneumocephalus resolved. Factors involved in the development of pneumocephalus include an unintended durotomy and intraoperative reverse Trendelenburg positioning that was utilized to decrease the risk of postoperative vision loss. When encountering cerebrospinal fluid (CSF) leakage intraoperatively, spine surgeons should level the operating table until closure of the dural defect to prevent potential complications associated with pneumocephalus. If postoperative patients complain of severe headaches or display a focal cranial neurologic deficit, then a computed tomography (CT) scan of the brain should be ordered and evaluated. Consulting neurologists should be aware of the circumstances surrounding this rare complication.

Are Breech Rates for Pedicle Screws Higher in the Upper Thoracic Spine?

STUDY DESIGN

A case-control study.

OBJECTIVES

To evaluate pedicle screw placement in pediatric patients with various etiologies of scoliosis, and to identify predictors of misplacement.

SUMMARY OF BACKGROUND DATA

Accuracy of placement of pedicle screws has not been well documented for posterior spinal instrumentation and fusion performed in the non-idiopathic population.

METHODS

A total of 54 patients (29 idiopathic, 16 neuromuscular, and 9 congenital/syndromic scoliosis), ages 5-19 years, were included. Computed tomography scans were obtained on patients postoperatively to assess screw position. Three pediatric orthopedic surgeons evaluated screw placement, and risk factors for misplacement were examined.

RESULTS

Of 1,042 pedicle screws, 8.3% were misplaced. Among all etiologies, screws placed at T1 (28.6%) and T2 (18.2%) had higher misplacement rates. T2 screws and curve correction greater than 75% had higher misplacement rates in congenital/syndromic patients; screws at T3, screws at upper end of construct, and proximal screws had significantly higher misplacement rates in neuromuscular patients; and no variables predicted misplacement in idiopathics. Screws placed at the most proximal end of the screw/rod construct also had a higher misplacement rate (14.1%) compared with all remaining levels (7.8%). Nonidiopathic patients had higher anterior misplacement compared with idiopathic. No screws were removed or revised, and no screw-related complications were observed.

CONCLUSIONS

Pedicle screw instrumentation in the thoracolumbar spine was safe for pediatric patients. We found that pedicle screws placed at top levels are at higher risk for misplacement among all pediatric scoliosis patients. Nonidiopathic patients are at higher risk for anterior screw misplacement, and the predictive effect of vertebral level is more profound in nonidiopathic patients. Because of these findings, we routinely use fluoroscopic guidance for the placement of T1 and T2 screws, and screws at the proximal end of construct.

Neurological outcome and management of pedicle screws misplaced totally within the spinal canal

STUDY DESIGN

This study reports 9 cases referred to our institution after surgical correction of adolescent idiopathic scoliosis and pedicle screws misplaced totally within the spinal canal.

OBJECTIVE

To assess the neurological outcome associated with pedicle screws misplaced totally within the spinal canal.

SUMMARY OF BACKGROUND DATA

The prevalence of neurological complications from misplaced pedicle screws might be under-reported, and optimal management of pedicle screws misplaced totally within the spinal canal remains unclear.

METHODS

Nine cases with pedicle screws misplaced totally within the spinal canal during posterior surgery for adolescent idiopathic scoliosis were reviewed. All cases presented at least 1 medially misplaced pedicle screw, with spinal canal intrusion greater than pedicle screw diameter, that is, completely within the spinal canal. Percentage of spinal canal intrusion was measured from computed tomographic scans.

RESULTS

Spinal canal intrusion varied from 21% to 61%. In 2 patients, misplacement of pedicle screws was recognized intraoperatively and all implants were removed. They both had motor deficits from which 1 patient recovered completely. Two patients had early postoperative postural headache that disappeared after removal of the misplaced screw. Five patients had uneventful early postoperative course. One of these developed a Brown-Sequard syndrome 2 years after surgery and underwent complete implant removal. Another patient developed left thoracic paresthesia 3 years after surgery, and complete implant removal was performed. Two neurologically intact patients had uneventful implant removal after infection. The last patient refused implant removal and remained asymptomatic 5 years after surgery.

CONCLUSION

Improper pedicle screw placement can lead to neurological complications appearing early or late (after 2 yr). Late neurological complications were associated with screw loosening in 2 cases. The authors strongly recommend removal of any pedicle screw misplaced totally within the spinal canal due to the risk of early or late neurological complications, regardless of the severity of spinal canal intrusion.

Symptomatic postlaminectomy cerebrospinal fluid leak treated with 4-dimensional ultrasound-guided epidural blood patch

BACKGROUND

A persistent cerebrospinal fluid leak after spinal surgery can be associated with both meningitis and/or pneumocephalus. Therefore, early active intervention is recommended with surgical exploration, lumbar subarachnoid drain, and less commonly epidural blood patch. In the absence of a ligamentum flavum, the use of high-resolution ultrasound (US) spine imaging enables real-time advancement of a Tuohy needle towards the dura and the precise injection of blood to cover the dural defect.

METHODS

Six patients, after lumbar spine surgery with instrumentation and primary closure was complicated by incidental dural tears, developed severe symptomatic headaches that failed conservative therapy. All patients underwent US-guided epidural blood patch. Precise needle advancement to the dura was observed with US guidance, and 4-dimensional US scanning was used to confirm the expansion of blood over the dura in real time.

RESULTS

All patients had symptomatic relief of their headaches and successful treatment of dural leaks using US-guided blood patch.

CONCLUSIONS

Real-time US guidance allowed accurate positioning of the Tuohy needle and deposition of the epidural blood patch in the setting of a surgically removed ligamentum flavum. Further investigations are needed to confirm that an US-guided epidural blood patch may offer reliable symptomatic relief to postsurgical persistent cerebrospinal fluid leak and may serve as an intermediate step along a spectrum between conservative initial management and surgical reexploration.

CT-guided percutaneous translaminar approach for blood patching: case report and technical note

In this article the authors describe a novel technique for performing epidural blood patch (EBP) by percutaneous CT-guided translaminar approach in challenging cases where interlaminar approach is not possible. A 24-year-old woman with medical history of multiple spinal surgeries and instrumentations for the treatment of scoliosis, presented 3 months post-operatively with acute and severe orthostatic headaches that began 1 week after surgery. Neurological examination was normal. Brain magnetic resonance imaging (MRI) showed mild thickening and contrast enhancing in the bilateral dura. Computed tomography (CT) myelography revealed CSF leakage in the level of T3 vertebra. EBP was attempted using fluoroscopic and then CT guidance; however, despite multiple attempts, the epidural space could not be accessed through the interlaminar route due to extensive instrumentation of the spine and profound structural bony abnormalities. EBP was performed successfully via a CT-guided translaminar approach using an Ostycut trephine needle (Angiomed(®)/Bard, Karlsruhe), without complications.

Spontaneous intracranial hypotension due to intradural thoracic osteophyte with superimposed disc herniation: report of two cases

Spontaneous intracranial hypotension (SIH) is a clinical syndrome in which absolute or relative hypovolemia of the cerebrospinal fluid (CSF) results in various neurological symptoms. The etiology of spontaneous CSF leaks often remains unknown. However, it is believed that the most common cause is the fragility of spinal meninges at the level of radicular nerve root sleeve. These tears can be spontaneous (primary) or secondary. Spinal pathologies can cause this tear with resultant CSF leak and SIH, which include spinal trauma, degenerative diseases and spinal surgery. Uncommonly, SIH is developed by osteophyte with disc herniation without any other pathology. In this article, we reported two cases of SIH secondary to spinal dural tear due to intradural thoracic osteophyte with superimposed disc herniation, with the absence of other pathologies, which were treated successfully with epidural blood patch (EBP).

Postsurgical intracranial hypotension: diagnostic and prognostic imaging findings

BACKGROUND AND PURPOSE

CSF loss with consecutive intracranial hypotension has been discussed as a possible pathogenetic mechanism in poor clinical outcome after uneventful neurosurgery and appears to be correlated to specific imaging findings. The purpose of this study was to describe the clinical and imaging findings of symptomatic intracranial hypotension likely induced by wound suction drainage.

MATERIALS AND METHODS

This is a review of previously published cases of patients in whom this condition developed after uneventful intracranial surgery. We performed an analysis of 3 more cases, of which 2 occurred after spinal surgery with accidental dural opening.

RESULTS

Sixteen patients who remained unconscious or did not become fully responsive after surgery showed symmetric bilateral thalamic/basal ganglia signal intensity changes on CT and MR imaging studies. Of these 16 patients, 4 died and 2 also had brain stem signal intensity changes. All patients had rapid and distinct intraoperative and postoperative CSF loss documented on CT and/or MR imaging studies by a transient increase of the sag ratio, defined as maximal anteroposterior midbrain diameter by maximal bipeduncular diameter.

CONCLUSIONS

The clinical course and typical MR imaging findings characterize the disease entity postsurgical intracranial hypotension. These findings also underline the potential danger of wound suction drainage in the case of possible CSF loss.