Spontaneous intracranial hypotension mimicking aneurysmal subarachnoid hemorrhage.

OBJECTIVE: An excruciating headache of instantaneous onset is known as a thunderclap headache. A subarachnoid hemorrhage is the prototypical cause, but other serious disorders may also present with a thunderclap headache, including cerebral venous sinus thrombosis, carotid artery dissection, and pituitary apoplexy. We report a group of patients with thunderclap headaches as the initial manifestation of spontaneous intracranial hypotension caused by a spinal cerebrospinal fluid leak. METHODS: Among 28 patients with spontaneous intracranial hypotension due to a documented spinal cerebrospinal fluid leak, four (14%) initially experienced an excruciating headaches of instantaneous onset. RESULTS: The mean age of the four patients (two men and two women) was 35 years (range, 24-45 yr). Nuchal rigidity was present in the three patients who sought early medical attention, and they underwent emergency computed tomographic scanning, lumbar puncture, and cerebral angiography to rule out an aneurysmal subarachnoid hemorrhage. The delay between the onset of headache and diagnosis of intracranial hypotension ranged from 4 days to 5 weeks. A fourth patient did not seek medical attention until 1 month after the ictus. CONCLUSION: Spontaneous intracranial hypotension should be included in the differential diagnosis of thunderclap headache, even when meningismus is present.

Biomechanical effects of progressive anterior cervical decompression.

STUDY DESIGN: A repeated-measures in vitro flexibility test was performed. OBJECTIVES: To determine the biomechanical functions of tissues resected during anterior cervical decompression of various extents. SUMMARY OF BACKGROUND DATA: The biomechanical consequences of discectomy have been studied in vitro, and uncovertebral joint removal has been modeled numerically. No studies have assessed the relative biomechanical contributions of different anterior column structures. METHODS: In seven human cadaver C4-T1 specimens, 20 motion segments were studied. After each destructive step, including discectomy, unilateral uncinate process removal, bilateral uncinate process removal, and posterior longitudinal ligament transection, torques were applied to four-level specimens while the angular motion was measured at each level. RESULTS: Angular range of motion and neutral zone increased by variable but statistically significant amounts after each progressive resection, most notably in flexion and extension. Each resection step caused progressively larger shifts (up to 23 mm) in the location of the axis of rotation. Uncovertebral joint resection caused the most significant changes in the observed angular coupling. CONCLUSIONS: Anterior cervical decompression significantly increases the instability and alters the kinematics of cervical motion segments. Each structure resected contributes to normal stability and kinematics, so as many structures as possible should be left intact during anterior decompression without fusion. Because flexion and extension were the modes of motion that increased most significantly after decompression, the primary function of a grafting technique or fixation device should be to limit these motions.

Biomechanics of grade I degenerative lumbar spondylolisthesis. Part 1: in vitro model.

OBJECT: The authors sought to create and to evaluate an in vitro model of Grade I degenerative (closed-arch) spondylolisthesis. METHODS: The model of spondylolisthesis was created by two primary procedures: 1) resection of the disc; and 2) stripping of anterior and posterior longitudinal ligaments away from the vertebral bodies (VBs). In 13 vertebral levels obtained from three cadaveric lumbar spines, the tissues were resected sequentially in alternating order to determine the relative contribution of each resection to spinal instability. The entire specimens were loaded with nonconstraining torques and then individual levels were loaded with anteroposterior shear forces. The motion values were measured optoelectronically for each specimen at individual levels. CONCLUSIONS: The integrity of the disc was more important than attachment of the ligaments to the VB, but the resection of both structures was necessary to achieve substantial destabilization. The structures of the spine are highly resilient, and destabilization is difficult to achieve without performing extensive resection. Using the techniques described in this paper to alter normal spines, a level of spinal instability (Grade I; 25% slippage) that may represent spondylolisthesis can be modeled in vitro.

Biomechanics of grade I degenerative lumbar spondylolisthesis. Part 2: treatment with threaded interbody cages/dowels and pedicle screws.

OBJECT: The authors sought to determine the biomechanical effectiveness of threaded interbody cages or dowels compared with that achieved using pedicle screw instrumentation in resisting Grade I lumbar spine degenerative spondylolisthesis. METHODS: Thirty-three levels obtained from seven cadaveric lumbar spines were instrumented with cages or dowels, pedicle screw/rod instrumentation, or both. Entire specimens were loaded with nonconstraining torques. Each level was loaded with anteroposterior shear forces while an optical system was used to measure the specimen's motion at individual levels. Pedicle screw/rods outperformed interbody cages and dowels in treating spondylolisthesis. Cages or dowels alone provided only moderate biomechanical stability, and their effectiveness depended heavily on the integrity of the ligaments and remaining annulus, whereas the success of pedicle screw fixation relied predominantly on the integrity of the bone for solid fixation. Little biomechanical difference was demonstrated between cages and dowels; both devices were susceptible to loosening with cyclic fatigue. CONCLUSIONS: Biomechanically, cages or dowels alone were suboptimal for treating lumbar spondylolisthesis, especially compared with pedicle screw/rods. Threaded cages or dowels used together with pedicle screws/rods created the most stable construct.

The effects of dexamethasone on bone fusion in an experimental model of posterolateral lumbar spinal arthrodesis.

OBJECT: The use of corticosteroid agents during the healing phase after spinal arthrodesis remains controversial. Although anecdotal opinion suggests that corticosteroids may inhibit bone fusion, such an effect has not been substantiated in clinical trials or laboratory investigations. This study was undertaken to delineate the effect of exogenous corticosteroid administration on bone graft incorporation in an experimental model of posterolateral lumbar fusion. METHODS: An established, well-validated model of lumbar intertransverse process spinal fusion in the rabbit was used. Twenty-four adult New Zealand white rabbits underwent L5-6 bilateral posterolateral spinal fusion in which autogenous iliac crest bone graft was used. After surgery, the animals were randomized into two treatment groups: a control group (12 rabbits) that received intramuscular injections of normal saline twice daily and a dexamethasone group (12 rabbits) that received intramuscular dexamethasone (0.05 mg/kg) twice daily. After 42 days, the animals were killed and the integrity of the spinal fusions was assessed by radiography, manual palpation, and biomechanical testing. In seven (58%) of the 12 control rabbits, solid posterolateral fusion was achieved. In no dexamethasone-treated rabbits was successful fusion achieved (p = 0.003). Tensile strength and stiffness of excised spinal segments were significantly lower in dexamethasone-treated animals than in control animals (tensile strength 91.4+/-30.6 N and 145.3+/-48.2, respectively, p = 0.004; stiffness 31.4+/-11.6 and 45.0+/-15.2 N/mm, respectively, p = 0.02). CONCLUSIONS: The corticosteroid agent dexamethasone inhibited bone graft incorporation in a rabbit model of single-level posterolateral lumbar spinal fusion, inducing a significantly higher rate of nonunion, compared with that in saline-treated control animals.

Biomechanical comparison of anterior cervical plating and combined anterior/lateral mass plating.

BACKGROUND CONTEXT: Previous studies showed anterior plates of older design to be inadequate for stabilizing the cervical spine in all loading directions. No studies have investigated enhancement in stability obtained by combining anterior and posterior plates. PURPOSE: To determine which modes of loading are stabilized by anterior plating after a cervical burst fracture and to determine whether adding posterior plating further significantly stabilizes the construct. STUDY DESIGN/SETTING: A repeated-measures in vitro biomechanical flexibility experiment was performed to investigate how surgical destabilization and subsequent addition of hardware components alter spinal stability. PATIENT SAMPLE: Six human cadaveric specimens were studied. OUTCOME MEASURES: Angular range of motion (ROM) and neutral zone (NZ) were quantified during flexion, extension, lateral bending, and axial rotation. METHODS: Nonconstraining, nondestructive torques were applied while recording three-dimensional motion optoelectronically. Specimens were tested intact, destabilized by simulated burst fracture with posterior distraction, plated anteriorly with a unicortical locking system, and plated with a combined anterior/posterior construct. RESULTS: The anterior plate significantly (p<.05) reduced the ROM relative to normal in all modes of loading and significantly reduced the NZ in flexion and extension. Addition of the posterior plates further significantly reduced the ROM in all modes of loading and reduced the NZ in lateral bending. CONCLUSIONS: Anterior plating systems are capable of substantially stabilizing the cervical spine in all modes of loading after a burst fracture. The combined approach adds significant stability over anterior plating alone in treating this injury but may be unnecessary clinically. Further study is needed to assess the added clinical benefits of the combined approach and associated risks.

Surgical treatment of lumbar spondylolisthesis.

This article provides an overview of studies that address the medical and surgical treatment of lumbar spondylolisthesis, both degenerative and isthmic. Although the efficacy of decompression for symptomatic lumbar stenosis recalcitrant to conservative treatment has been demonstrated, the addition of instrumentation to a fusion procedure remains controversial. The senior author's (VKHS) experience with pedicle screw fixation and fusion for lumbar spondylolisthesis, the addition of interbody fusion, and spinal navigation is reviewed.

Clinical measurement, statistical analysis, and risk-benefit: controversies from trials of spinal injury.

BACKGROUND: The National Acute Spinal Cord Injury Studies have been a series of trials assessing the role of pharmacologic agents in the prevention of secondary neuronal damage after acute spinal cord injury. METHODS: The trials were multicenter randomized, controlled studies. RESULTS: Two trials have demonstrated the efficacy of high-dose methylprednisolone in improving neurologic and functional recovery and have shown a reassuring safety profile. CONCLUSION: This study responds to a recent commentary on these trials and examines in particular the roles of clinical measurement, statistical analysis, and risk benefit in assembling evidence for or against innovative therapies.

Pediatric cervical spine injuries: report of 102 cases and review of the literature.

OBJECT: To evaluate and review their experience with pediatric cervical injuries and factors affecting outcome, the authors conducted a retrospective clinical study of 102 cases (65% boys, 35% girls) of pediatric cervical spine injuries treated in the last decade. This study is an extension of and comparison with their earlier experience. METHODS: Patients were divided into two age groups-birth to 9 years (Group I) and 10 to 16 years of age (Group 2)- and managed according to status at presentation and type of injury. Thirty patients were managed surgically and 72 non-surgically (42 wore a halo brace and 30 wore hard collars or custom-molded braces). Motor vehicle accidents were the most common cause of injury, and 40% were associated with head injury. Patients in the younger-age group (Group 1) sustained more neurological injuries than the older patients in Group 2, and most injuries were in the upper cervical spine. Of the 38 children in Group 1, in 39% a subluxation was present and in 29% a fracture or fracture/subluxation was demonstrated. Of the patients in Group 2, 80% had sustained fractures or fracture/subluxations. Vertebral fractures were the most common radiological findings (32%). At late follow-up review (mean 5 years), solid fusions were demonstrated in all patients. Neurological deterioration did not occur in any patient. The mortality rate was 16%. Compared with the authors' earlier report, the incidence of cases with pediatric cervical injuries increased, as did the number managed surgically. Various fusion techniques were used, and neurological and fusion outcomes improved as compared with the previous report. CONCLUSIONS: The prognosis of neurological recovery from pediatric cervical spine injuries is related to the severity of the initial neurological injury. Management must be tailored to the patient's age, neurological status, and type and level of injury. Compared with our earlier experience, fusion and instrumentation procedures were used more frequently. Different types of fusion and instrumentation procedures can be performed safely in children and produce good outcomes.

Pediatric spine and spinal cord trauma. State of the art for the third millennium.

The purpose of this work was to analyze the literature published in English and to review the experience of the Barrow Neurological Institute (BNI) with spine and spinal cord injury (SCI) in children. Standard computerized data bases were queried for information regarding SCI, spinal injury, spinal instability, and spinal cord regeneration to produce a review of the epidemiology, diagnosis, treatment, outcome and directions for future research. We also reviewed our experiences in the management of infants and children with spine injuries and SCIs and with spinal instability from all causes. A total of 132 articles were identified and obtained from the Medical Library at St. Joseph's Hospital and Medical Center in Phoenix, Ariz. and through interlibrary loan. All these articles were read, although not all were used in the final review. A review of all children with SCIs revealed that fractures treated over the past 20 years at the BNI were very rare in preadolescent children, who suffered mostly from ligamentous injury or SCI without radiographic abnormality. A total of 68 children aged 16 years or younger who had been treated over the past 15 years and who had undergone spinal fusions for trauma, congenital anomalies, or tumor resection were identified. Occipitocervical fusion is well tolerated in children as young as 11 months when internal stabilization with a threaded titanium rod is used. Posterior instrumentation, including pedicle screw fixation, is feasible in children as young as 4 years. Fusion techniques derived from the adult spinal instrumentation experience were found appropriate except for the youngest patients. Fusion in the newborn period was futile in our experience. The adolescent spine does not differ from the adult spine in terms of sensitivity or response to fixation. Children past the neonatal period can be successfully instrumented for spinal stability without apparent long-term sequelae. Related advances are needed in the area of prevention. Long-term advances in spinal cord regeneration can be expected from ongoing basic science investigations.

Cervical corpectomy: report of 185 cases and review of the literature.

OBJECT: This study was conducted to determine the indications, safety, efficacy, and complication rate associated with performing corpectomy to achieve anterior decompression of neural elements or for removing anterior lesions. METHODS: Between 1987 and 1998, 185 patients underwent cervical corpectomy for the treatment of degenerative spondylitic disease (81 cases), ossification of posterior longitudinal ligament (16 cases), correction of postoperative kyphosis (31 cases), trauma (39 cases), tumor (10 cases), and infection (eight cases). Ninety-nine patients presented with myelopathy, 48 with radiculomyelopathy, 24 with radicular pain, and 14 with neck muscle pain. Eighty-seven patients underwent a one-level corpectomy; 45 of these patients underwent a discectomy at a different level. Seventy patients underwent a two-level corpectomy; 27 of these patients underwent a discectomy at a different level. Twenty-eight patients underwent a three-level corpectomy. Autograft (iliac crest) was used in 141 cases and allograft (fibula) in 44 cases. All but six patients underwent fixation with an anterior plate-screw system. There were no operative deaths. During the procedure the vertebral artery was injured in four patients and preserved in two of them. No neurological sequelae were encountered. Postoperative hoarseness, transient dysphagia, and pain at the graft site were transitory and successfully managed. The fusion rate was 98.8%. Six patients experienced transient deterioration after surgery but they improved. No patient experienced permanent neurological deterioration and 160 (86.5%) improved. CONCLUSIONS: Corpectomy has an important role in the management of various degenerative, traumatic, neoplastic, or infectious disorders of cervical spine. Following treatment in this series, radiculopathy always improved and myelopathy was reversed in most patients.

Stability of the craniovertebral junction after unilateral occipital condyle resection: a biomechanical study.

OBJECT: The authors sought to determine the biomechanics of the occipitoatlantal (occiput [Oc]-C1) and atlantoaxial (C1-2) motion segments after unilateral gradient condylectomy. METHODS: Six human cadaveric specimens (skull with attached upper cervical spine) underwent nondestructive biomechanical testing (physiological loads) during flexion-extension, lateral bending, and axial rotation. Axial translation from tension to compression was also studied across Oc-C2. Each specimen served as its own control and underwent baseline testing in the intact state. The specimens were then tested after progressive unilateral condylectomy (25% resection until completion), which was performed using frameless stereotactic guidance. At Oc-C1 for all motions that were tested, mobility increased significantly compared to baseline after a 50% condylectomy. Flexion-extension, lateral bending, and axial rotation increased 15.3%, 40.8%, and 28.1%, respectively. At C1-2, hypermobility during flexion-extension occurred after a 25% condylectomy, during axial rotation after 75% condylectomy, and during lateral bending after a 100% condylectomy. CONCLUSIONS: Resection of 50% or more of the occipital condyle produces statistically significant hypermobility at Oc-C1. After a 75% resection, the biomechanics of the Oc-C1 and C1-2 motion segments change considerably. Performing fusion of the craniovertebral junction should therefore be considered if half or more of one occipital condyle is resected.

A prospective randomized double-blind controlled trial to evaluate the efficacy of an analgesic epidural paste following lumbar decompressive surgery.

OBJECT: Pain control can often be improved by local (as opposed to systemic) application of analgesic and/or anesthetic medication. The purpose of this study was to evaluate the efficacy of a single-dose epidural analgesic "paste" in the control of postoperative pain in patients who have undergone lumbar decompressive surgery. METHODS: Sixty patients undergoing routine elective lumbar decompressive surgery were randomized in a double-blind fashion to one of two groups: those receiving active paste or placebo paste. The paste was applied to the exposed dura at the time of surgery, just prior to wound closure. Patients received follow-up care in the hospital and at home for 3 months postsurgery. Several outcome measures were studied to ascertain differences in pain control and to ensure comparability between groups. Patients who received active paste demonstrated significantly lower pain scores compared with those who received placebo paste for up to 6 weeks postoperatively. General health perception indexed by the Short Form 36 was also significantly better in patients who received active paste for up to 6 weeks. In-hospital and outpatient oral narcotic consumption was significantly lower in the active paste-treated group. Inpatient straight leg raising scores were improved in those patients who received active compared with control paste. CONCLUSIONS: Application of an analgesic paste directly to the epidural space during lumbar decompressive surgery significantly improves postoperative pain control, reduces prescribed analgesic drug consumption, and improves overall health perception for up to 6 weeks following surgery. The authors conclude that this postoperative pain control strategy is both effective and safe and may provide a new standard of pain management in patients undergoing lumbar discectomy or laminectomy.

Bilateral sagittal split mandibular osteotomies as an adjunct to the transoral approach to the anterior craniovertebral junction. Technical note.

Transoral approaches are used to expose the craniovertebral junction anteriorly. In patients in whom there is limited mandibular excursion, the placement of retractors and/or surgical instruments is difficult, and midline "stairstep split mandibulotomy" has been advocated as an adjunctive procedure. Although effective, this approach requires external splitting of the lip as well as median glossotomy or a lateral mucosal incision. The purpose of this study was to show that bilateral sagittal split mandibular osteotomies (BSSMOs), which are used in orthognathic surgery, represent a safer and more effective alternative to the stairstep split mandibulotomy when performed as an adjunct to the transoral approach because all incisions are intraoral and the plane of retraction is rostrocaudal instead of lateral. Hospital records and radiographic files of four patients who underwent BSSMO/transoral approach for odontoidectomy between 1994 and 1997 were reviewed retrospectively. There were three women and one boy (mean age 37.8 years, range 11-68 years). Predisposing conditions included rheumatoid arthritis (two patients), Klippel-Feil syndrome (one patient), and congenital occipitocervical instability (one patient). Jaw mobility was limited in all patients. In addition, one patient had macroglossia, another micrognathia, and another retrognathia. The BSSMO provided excellent exposure for resection of the odontoid process, as verified on follow-up magnetic resonance imaging or computerized tomography studies obtained in all patients. All mandibles were rigidly fixed by placing anterior mandibular border titanium plates and unicortical screws, and there was no incidence of nonunion or of lingual or inferior alveolar nerve injuries. The mean follow-up period was 26 months. The BSSMO is an excellent, less invasive adjunct to the transoral approach in patients with limited jaw mobility.

The optimal radiologic method for assessing spinal canal compromise and cord compression in patients with cervical spinal cord injury. Part II: Results of a multicenter study.

STUDY DESIGN: A multicenter, retrospective study using computed tomographic and magnetic resonance imaging data to establish quantitative, reliable criteria of canal compromise and cord compression in patients with cervical spinal cord injury. OBJECTIVES: To develop and validate a radiologic assessment tool of spinal canal compromise and cord compression in cervical spinal cord injury for use in clinical trials. SUMMARY OF BACKGROUND DATA: There are few quantitative, reliable criteria for radiologic measurement of cervical spinal canal compromise or cord compression after acute spinal cord injury. METHODS: The study included 71 patients (55 men, 16 women; mean age, 39.7 +/- 18.7 years) with acute cervical spinal cord injury. Causes of spinal cord injury included motor vehicle accidents (n = 36), falls (n = 20), water-related injuries (n = 8), sports (n = 5), assault (n = 1), and farm accidents (n = 1). Canal compromise was measured on computed tomographic scan and T1- and T2-weighted magnetic resonance imaging, and cord compression at the level of maximum injury was measured on T1- and T2-weighted magnetic resonance imaging. All films were assessed by two independent observers. RESULTS: There was a strong correlation of canal compromise and/or cord compression measurements between axial and midsagittal computed tomography, and between axial and midsagittal T2-weighted magnetic resonance imaging. Spinal canal compromise assessed by computed tomography showed a significant although moderate correlation with spinal cord compression assessed by T1- and T2-weighted magnetic resonance imaging. Virtually all patients with canal compromise of 25% or more on computed tomographic scan had evidence of some degree of cord compression on magnetic resonance imaging, but a large number of patients with less than 25% canal compromise on computed tomographic scan also had evidence on magnetic resonance imaging of cord compression. CONCLUSIONS: In patients with cervical spinal cord injury, the midsagittal T1- and T2-weighted magnetic resonance imaging provides an objective, quantifiable, and reliable assessment of spinal cord compression that cannot be adequately assessed by computed tomography alone.