Video-Assisted Thoracoscopic Lateral Interbody Fusion for Symptomatic Pseudarthrosis in Neurofibromatosis 1-Associated Spinal Deformity

BACKGROUND

The treatment of symptomatic pseudarthrosis via posterior-only approaches in the setting of neurofibromatosis 1 (NF1) is challenging due to dural ectasias, resulting in erosion of the posterior elements. The purpose of this report is to illustrate a minimally invasive method for performing anterior thoracic fusion for pseudarthrosis in a patient with NF1-associated scoliosis and dysplastic posterior elements. To the best of our knowledge, this is the first documented case of using video-assisted thoracoscopic lateral interbody fusion to treat pseudarthrosis for NF1-associated spinal deformity.

CASE DESCRIPTION

The patient underwent video-assisted thoracoscopic anterior spinal fusion via a direct lateral interbody approach with interbody cage placement at T10-T11 and T11-T12, followed by revision of his posterior spinal fusion and instrumentation. The patient had an uneventful postoperative course. At 6 months of follow-up, the patient had complete resolution of his preoperative symptoms and had returned to full-time work with no complaints. At 3 years postoperatively, the patient reported being satisfied with the operation and had continued to work full-time without restrictions.

CONCLUSIONS

To the best of our knowledge, this is the first report of pseudarthrosis in the setting of NF1-associated scoliosis treated via minimally invasive anterior thoracic fusion facilitated by video-assisted thoracoscopic surgery. This is a powerful technique that allows for safe access for anterior thoracic fusion in the setting of dysplastic posterior anatomy and poor posterior bone stock.

Is spinopelvic mismatch associated with increased disability at 2 years following short-segment lumbar fusions?

OBJECTIVE

This study aimed to investigate the impact of pelvic incidence (PI) and lumbar lordosis (LL) matching on health-related quality of life (HRQOL) outcomes in patients undergoing one- or two-level lumbar fusions for degenerative pathology. The study also examined changes in alignment and HRQOL over a 24-month follow-up period.

METHODS

A retrospective cohort study used data from a multicenter, prospectively collected database. Radiographic parameters were measured preoperatively and at 3-month and 24-month postoperative time points. Patients were categorized as having alignment (PI-LL ≤ 10°) or malalignment (PI-LL > 10°) at all time points. The Oswestry Disability Index scores were collected at the same time points. Statistical analyses assessed differences in HRQOL scores and radiographic parameters between the aligned and malaligned groups.

RESULTS

Seventy-six patients were included. Both the aligned and malaligned groups showed improved HRQOL scores after surgery, but patients with proper alignment (PI-LL ≤ 10°) had significantly better HRQOL scores at the 24-month follow-up. Alignment remained stable from 3 months to 24 months postoperatively, with minimal movement between the aligned and malaligned groups.

CONCLUSIONS

Proper PI-LL matching in one- and two-level lumbar fusions for degenerative pathology leads to improved HRQOL outcomes at the 24-month follow-up. Patients with maintained proper alignment after surgery experience continued improvement in disability levels. Surgeons should consider longer follow-up for patients who do not achieve proper alignment initially, as 24 months is crucial for assessing the consequences of malalignment in short-segment lumbar fusions.

Gout-Induced Cervical Deformity and Progressive Myelopathy Mimicking Infection Requiring Cervical Reconstruction

BACKGROUND

This study describes a rare case where gout, a condition primarily associated with joint inflammation, initially manifested as a progressive cervical kyphotic deformity, mimicking infection and causing myelopathy. The patient, a previously healthy 56-year-old woman, presented with severe jaw pain and a temporomandibular joint abscess, alongside 2 months of worsening balance and arm/hand tingling. Extensive clinical and radiographic assessments revealed a severe cervical kyphotic deformity with bony erosion at multiple vertebral levels, raising suspicion of an infectious cause of compressive myelopathy.

METHODS

The patient underwent an urgent staged surgical intervention involving multilevel cervical decompression and fusion, coupled with cervical deformity correction.

RESULTS

Post surgery, she received antibiotics for 7 days, during which pathologic analysis unveiled collections of macrophages reacting to urate crystal deposition in a pattern consistent with gouty tophus. This unexpected diagnosis marked a novel case of undiagnosed gout-induced severe cervical deformity presenting with myelopathic symptoms and successfully managed through cervical spine deformity correction.

CONCLUSIONS

This report underscores the significance of considering gout as a potential cause when encountering unusual spinal pathologies, especially in cases where gout-related symptoms are atypical. The presented 540-degree surgical approach effectively addressed both the cervical deformity and gout-induced myelopathic symptoms. To the best of our knowledge, this study represents the first documented instance of a patient with undiagnosed gout-induced severe cervical deformity successfully treated through cervical spine deformity correction, emphasizing the importance of vigilance and innovative management approaches in such rare clinical scenarios. As of the 2-year follow-up, the patient exhibited significant symptom improvement and overall well-being.

Trans-sacral interbody fixation in long fusions to the sacrum for adult spinal deformity: complications and fusion rates at minimum two years follow-up

PURPOSE

This study aims to investigate the fusion rate and complications associated with trans-sacral interbody fusion (TSIF) in long fusions to the sacrum for adult spinal deformity (ASD) over a two year follow-up period. Potential predictor variables associated with pseudarthrosis were also examined.

METHODS

A retrospective clinical review was conducted on a consecutive series of ASD patients who underwent long fusions to the sacrum, with TSIF performed as a same-day or staged procedure. Patient demographics, bone mineral density, operative details, perioperative and late complications, and fusion rates were reviewed. Univariate analysis was used to identify the risk factors associated with pseudarthrosis.

RESULTS

The study included 43 patients with an average age of 55.3 ± 8.9 years. The perioperative complication rate was 28%, with 12% of the complications directly related to TSIF. The late complication rate was 33%, with 16% related to TSIF. The most common complications were pseudarthrosis (14%) and postoperative ileus (7%). The overall radiographic fusion rate at two years was 86%. Univariate analysis revealed that revision surgery was significantly associated with pseudarthrosis (p = 0.027). Over the follow-up period, patients who underwent TSIF during long posterior fusions to the sacrum showed improvement in overall SRS scores, ODI scores, and SF-36 physical health and mental health (p < 0.05).

CONCLUSION

TSIF is a relatively safe and minimally invasive method for achieving interbody fusion at the lumbosacral junction in the treatment of ASD, with acceptable fusion rates and a low complication rate. However, TSIF is not recommended for revision reconstruction in ASD.

Personalized Medicine in Orthopaedic Surgery: The Case of Spine Surgery

Personalized medicine has made a tremendous impact on patient care. Although initially, it revolutionized pharmaceutical development and targeted therapies in oncology, it has also made an important impact in orthopaedic surgery. The field of spine surgery highlights the effect of personalized medicine because the improved understanding of spinal pathologies and technological innovations has made personalized medicine a key component of patient care. There is evidence for several of these advancements to support their usage in improving patient care. Proper understanding of normative spinal alignment and surgical planning software has enabled surgeons to predict postoperative alignment accurately. Furthermore, 3D printing technologies have demonstrated the ability to improve pedicle screw placement accuracy compared with free-hand techniques. Patient-specific, precontoured rods have shown improved biomechanical properties, which reduces the risk of postoperative rod fractures. Moreover, approaches such as multidisciplinary evaluations tailored to specific patient needs have demonstrated the ability to decrease complications. Personalized medicine has shown the ability to improve care in all phases of surgical management, and several of these approaches are now readily available to orthopaedic surgeons.

What is the fate of the adjacent segmental angles 6 months after single-level L3-4 or L4-5 lateral lumbar interbody fusion?

BACKGROUND CONTEXT

Lateral lumbar interbody fusion (LLIF) is an effective technique for fusion and sagittal alignment correction/maintenance. Studies have investigated the impact on the segmental angle and lumbar lordosis (and pelvic incidence-lumbar lordosis mismatch), however not much is documented regarding the immediate compensation of the adjacent angles.

PURPOSE

To evaluate acute adjacent and segmental angle as well as lumbar lordosis changes in patients undergoing a L3-4 or L4-5 LLIF for degenerative pathology.

STUDY DESIGN/SETTING

Retrospective cohort study.

PATIENT SAMPLE

Patients included in this study were analyzed pre- and post-LLIF performed by one of three fellowship-trained spine surgeons, 6 months following surgery.

OUTCOME MEASURES

Patient demographics (including body mass index, diabetes diagnosis, age, and sex) as well as VAS and ODI scores were measured. Lateral lumbar radiograph parameters: lumbar lordosis (LL), segmental lordosis (SL), infra and supra-adjacent segmental angle, and pelvic incidence (PI).

METHODS

Multiple regressions were applied for the main hypothesis tests. We examined any interactive effects at each operative level and used the 95% confidence intervals to determine significance: a confidence interval excluding zero indicates a significant effect.

RESULTS

We identified 84 patients who underwent a single level LLIF (61 at L4-5, 23 at L3-4). For both the overall sample and at each operative level, the operative segmental angle was significantly more lordotic postop compared to preop (all ps≤.01). Adjacent segmental angles were significantly less lordotic postop compared to pre-op overall (p=.001). For the overall sample, greater lordotic change at the operative segment led to more compensatory reduction of lordosis at the supra-adjacent segment. At L4-5, more lordotic change at the operative segment led to more compensatory lordosis reduction at the infra-adjacent segment.

CONCLUSION

The present study demonstrated that LLIF resulted in significant increase in operative level lordosis and a compensatory decrease in supra- and infra-adjacent level lordosis, and subsequently no significant impact on spinopelvic mismatch.

Incidence, etiology and time course of delays to adult spinal deformity surgery: a single-center experience

PURPOSE

We sought to determine the incidence, origin, and timeframe of delays to adult spinal deformity surgery so that institutions using preoperative multidisciplinary patient assessment teams might better anticipate and address these potential delays.

METHODS

Complex spine procedures for treatment of adult spinal deformity from 1/1/18 to 8/31/21 were identified. Procedures for infection, tumor, and urgent/emergent cases were excluded. Operations delayed due to COVID or those that were performed outside of our established perioperative care pathway were also excluded. The electronic health record was used to identify the etiology and timeline of all pre- and peri-operative delays.

RESULTS

Of 235 patients scheduled for complex spine surgery, 193 met criteria for inclusion. Of these patients, 35 patients experienced a surgical delay (18.1%) with a total of 41 delays recorded. Reasons for delay include medically unoptimized (25.6%), intraoperative complication (17.9%), patient directed delay (17.9%), patient illness/injury (15.4%), scheduling complication (10.3%), insurance delay/denial (5.1%), and unknown (2.6%). Twenty-four delays experienced by 22 individuals occurred within 7 days of their scheduled surgery date.

CONCLUSION

At a single multidisciplinary center, most delays to adult spinal deformity surgery occur before a patient is admitted to the hospital, and for recommendations of additional medical workup/clearance. We suspect that the preoperative protocol might increase pre-admission delays for unoptimized patients, as the protocol is intended to ensure patients receive surgery only when they are medically ready. Further research is needed to determine the economic and system impact of delays related to a preoperative optimization protocol weighed against the reduction in adverse events these protocols can provide.

Anterior Cervical Corpectomy and Fusion for Degenerative Cervical Spondylotic Myelopathy: Case Presentation With Surgical Technique Demonstration and Review of Literature

Anterior cervical corpectomy and fusion (ACCF) provides an extensive decompression and provides a large surface area for fusion in patients presenting with cervical spondylotic myelopathy. Unfortunately, this procedure is a more difficult spinal surgery to perform (compared with a traditional anterior cervical discectomy and fusion) and has a higher incidence of overall complications. In literature, ACCF has functional outcomes that seem clinically equivalent to those for multilevel anterior cervical discectomy and fusion, especially when contained to 1 vertebral body level, and in cases, for which both posterior and anterior procedures would be appropriate surgical options, may provide greater long-term clinical benefit than posterior fusion or laminoplasty. In this manuscript, we summarize the indications and outcomes following ACCF for degenerative cervical spondylotic myelopathy. We then describe a case presentation and associated surgical technique with a discussion of complication avoidance with this procedure.

Defining Cervical Sagittal Plane Deformity - When Are Sagittal Realignment Procedures Necessary in Patients Presenting Primarily With Radiculopathy or Myelopathy?

OBJECTIVE

It remains unclear whether cervical sagittal deformity (CSD) should be defined by radiographic parameters alone versus both clinical and radiographic factors, and whether radiographic malalignment by itself warrants a CSD corrective surgery in patients who present primarily with neurologic symptoms.

METHODS

We administered a survey to a group of expert surgeons to evaluate whether radiographic parameters alone were sufficient to diagnose CSD, and in which scenarios surgeons recommend a CSD realignment procedure versus addressing the neurologic symptoms alone.

RESULTS

No single radiographic criteria reached a 50% threshold as being sufficient to establish the diagnosis of CSD. When asymptomatic radiographic malalignment was present, a sagittal deformity correction was more likely to be recommended in patients with myelopathy versus those with radiculopathy alone. The majority of surgeons recommended deformity correction when symptoms of cervical deformity were present in addition to radiographic malalignment (85% with deformity symptoms and radiculopathy, 93% with deformity symptoms and myelopathy).

CONCLUSION

There is no consensus on which radiographic and/or clinical criteria are necessary to define the presence of CSD. We recommend that symptoms of cervical deformity, in addition to radiographic parameters, be considered when deciding whether to perform deformity correction in patients who present primarily with myelopathy or radiculopathy.

Use of Cannulated Reamers to Facilitate Thoracic Diskectomy Using a Minimally Invasive Retropleural Thoracotomy Approach-Surgical Technique

BACKGROUND

The surgical treatment of symptomatic thoracic disk herniations is technically challenging. In the past decade, a minimally invasive retropleural thoracotomy approach has become more popular to treat this pathology. However, efficient bone removal to safely perform the diskectomy and spinal cord decompression is difficult with this technique because of the small incision size and long working distance in the thoracic cavity and the proximity of the compressed thoracic cord.

OBJECTIVE

To describe a novel surgical technique for performing a thoracic diskectomy using a minimally invasive lateral approach using cannulated reamers to facilitate bone removal.

METHODS

This technique was used in 7 consecutive patients who presented with thoracic myelopathy from a thoracic disk herniation. First, a standard lateral minimally invasive retropleural approach to the thoracic spine was performed. Partially threaded guide wires were placed in the posterior aspect of the vertebral bodies adjacent to the affected disk space, and sequential cannulated reamers were passed over the guidewires to perform partial corpectomies. The posterior annulus, posterior longitudinal ligament, and herniated disk material were then resected using Penfield dissectors and Kerrison rongeurs to complete the decompression.

RESULTS

All 7 patients who underwent thoracic diskectomy using this approach had stable or improved neurologic function postoperatively. There were no complications related to the use of the cannulated reamer technique.

CONCLUSION

The use of cannulated reamers provides a simple and efficient method for safe bone removal to facilitate minimally invasive thoracic diskectomy using a lateral approach. This is an easily reproducible technique using commonly available equipment.

Team Approach: Safety and Value in the Practice of Complex Adult Spinal Surgery

Surgical management of complex adult spinal deformities is of high risk, with a substantial risk of operative mortality. Current evidence shows that potential risk and morbidity resulting from surgery for complex spinal deformity may be minimized through risk-factor optimization. The multidisciplinary team care model includes neurosurgeons, orthopaedic surgeons, physiatrists, anesthesiologists, hospitalists, psychologists, physical therapists, specialized physician assistants, and nurses. The multidisciplinary care model mimics previously described integrated care pathways designed to offer a structured means of providing a comprehensive preoperative medical evaluation and evidence-based multimodal perioperative care. The role of each team member is illustrated in the case of a 66-year-old male patient with previous incomplete spinal cord injury, now presenting with Charcot spinal arthropathy and progressive vertebral-body destruction resulting in lumbar kyphosis.

Outcomes of Fusions From the Cervical Spine to the Pelvis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Determine the indications, complications, and clinical outcomes in patients requiring fusions from the cervical spine to the pelvis. Several investigators have examined fusions from the thoracic spine to the sacrum, but no similar study has been performed for cervical-to-pelvis fusions.

METHODS

Patients from 2003 to 2014 with an upper instrumented vertebrae (UIV) in the cervical spine (any level) and a lower instrumented vertebrae (LIV) in the sacrum or pelvis were included in the study. Those with infectious or acute trauma-related deformities were excluded. Patient demographics, medical history, diagnosis, operative procedure, and health-related quality of life measures were analyzed. Student's t test, Kruskal-Wallis test, and χ² test were used as appropriate; significance was set at P < .05 for all tests.

RESULTS

Fifty-five patients met inclusion criteria for the study. Average follow-up was 2.8 years. Proximal junctional kyphosis was the most common indication for cervical-to-pelvis fusions (36%). The most common UIV was C2 (29%) followed by C7 (24%). There was an average 31° correction in maximum kyphosis and a 3.3 cm improvement in sagittal vertical axis. In adults, the rate of complication was 71.4%, with a major complication rate of 39.3% and reoperation rate of 53.6%. There was significant improvement in the Scoliosis Research Society (SRS-22r) score (3.0 to 3.5; P < .01).

CONCLUSION

Proximal junctional kyphosis is the most common indication for patients requiring fusion to the cervical spine. Adult patients incur a significant risk of major complications and reoperations. However, significant improvement in SRS-22r outcomes are noted in these patients.

Lumbar computed tomography scans are not appropriate surrogates for bone mineral density scans in primary adult spinal deformity

OBJECTIVE

The authors examined the correlation between lumbar spine CT Hounsfield unit (HU) measurements and bone mineral density measurements in an adult spinal deformity (ASD) population.

METHODS

Patients with ASD were identified in the records of a single institution. Lumbar CT scans were reviewed, and the mean HU measurements from L1–4 were recorded. Bone mineral density (BMD) was assessed using femoral neck and lumbar spine dual-energy x-ray absorptiometry (DEXA). The number of patients who met criteria for osteoporosis was determined for each imaging modality.

RESULTS

Forty-eight patients underwent both preoperative DEXA and CT scanning. Forty-three patients were female and 5 were male. Forty-seven patients were Caucasian and one was African American. The mean age of the patients was 62.1 years. Femoral neck DEXA was more likely to identify osteopenia (n = 26) than lumbar spine DEXA (n = 8) or lumbar CT HU measurements (n = 6) (p < 0.001). There was a low-moderate correlation between lumbar spine CT and lumbar spine DEXA (r = 0.463, p < 0.001), and there was poor correlation between lumbar spine CT and femoral neck DEXA (r = 0.303, p = 0.036).

CONCLUSIONS

Despite the opportunistic utility of lumbar spine CT HU measurements in identifying osteoporosis in patients undergoing single-level fusion, these measurements were not useful in this cohort of ASD patients. The correlation between femoral neck DEXA and HU measurements was poor. DEXA assessment of BMD in ASD patients is essential to optimize the care of these complicated cases.

Adolescent Idiopathic Scoliosis: Update on Bracing, Surgical Techniques, and Patient Safety

The primary goal in the management of adolescent idiopathic scoliosis is to prevent the progression of spinal deformity either with the use of a brace or with surgery. The goals of surgery, if indicated, are to correct the spinal deformity safely and to preserve overall spinal balance and as many motion segments as possible, which maximizes the long-term health of a patient's spine. Recently, tremendous advances have been made in the surgical techniques that are used to correct adolescent idiopathic scoliosis, and improved tools have allowed surgeons to perform spinal deformity surgery as safely and with as few complications as possible. Surgeons should be aware of recent evidence that demonstrates the efficacy of bracing in patients who have adolescent idiopathic scoliosis. In addition, surgeons should understand recent advances in spinal deformity surgery with regard to fusion level selection, implant placement, three-dimensional deformity correction, and techniques that are used to minimize perioperative complications.

Evaluating the Diagnostic Yield of Computed Tomography-Guided Aspirations in Suspected Post-operative Spine Infections

BACKGROUND

Early detection of surgical site infection (SSI) following spinal surgery would allow for prompt treatment and would improve overall outcome, yet early diagnosis is a challenge. Computed tomography (CT) guided aspiration of fluid collections may aid in diagnosis, as its diagnostic utility has previously been demonstrated in the setting of hip SSI, knee SSI, and spontaneous diskitis. There is no literature on its use in post-operative spinal SSIs.

QUESTIONS/PURPOSES

The current study aims to (1) determine the diagnostic value of CT-guided aspiration in evaluating suspected SSI; (2) identify the characteristics of the clinical presentation that are predictive of SSI; and (3) identify characteristics of the hematologic workup that are predictive of SSI.

METHODS

Thirty patients who underwent CT-guided aspiration of paraspinal post-operative fluid collections and culture of aspirate fluid over the 6-year period from 2006 to 2011 were retrospectively reviewed. Aspirate fluid culture results were compared to intraoperative cultures, which were used as the "gold standard" for diagnosing SSI. The diagnostic value was evaluated by determining the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of aspirate fluid cultures. Clinical presentation, patient demographics, comorbidities, and laboratory values were reviewed for association with infection risk.

RESULTS

Eleven of thirty patients undergoing CT-guided aspiration were subsequently confirmed to have SSI through positive cultures. Wound drainage, wound erythema, elevated ESR, and cloudiness of aspirate fluid were associated with SSI. The sensitivity and specificity of aspirate cultures were 36.4 and 89.5%, respectively, and the respective positive predictive value (PPV) and negative predictive value (NPV) were 66.7 and 70.8%.

CONCLUSIONS

Cloudy aspirate fluid was highly suggestive of infection, while wound erythema, drainage, and elevated ESR were also suggestive of SSI. CT-guided aspirations are a useful adjunct tool in evaluating for SSI but further studies are necessary before it can be considered a stand-alone diagnostic procedure.

Incidence and Risk Factors for Major Surgical Complications in Patients With Complex Spinal Deformity: A Report From an SRS GOP Site

STUDY DESIGN

Retrospective analysis of a prospectively collected single-center database.

OBJECTIVES

To report the incidence of and identify risk factors for perioperative complications in surgically treated pediatric and adult patients with complex spine deformities in an underserved region and Scoliosis Research Society Global Outreach Program site.

SUMMARY OF BACKGROUND DATA

Surgical treatment for complex spinal deformity is challenging and requires a multidisciplinary approach for optimal management. The incidence and risk factors for major perioperative complications in outreach sites with limited resources are unknown.

METHODS

A total of 427 consecutive patients who underwent instrumented spinal fusion for complex spinal deformities were reviewed. Clinical, radiographic, and demographic data were reviewed at preoperative and postoperative time points, and potential risk factors for perioperative complications were assessed. The authors performed multivariate logistic regression analysis (LRA) to determine independent risk factors for postoperative complications and neurological deficits.

RESULTS

Major complications were seen in 85 cases, which consisted of neurologic deficits (n = 27; 17 transient and 10 permanent), wound infections (n = 17), implant-related problems (n = 35), progressive deformity (n = 13), and death (n = 6). Among the possible risk factors, univariate LRA indicated 3-column osteotomies as a risk factor for postoperative major complications and multivariate LRA indicated 3-column osteotomies as an independent risk factor for neurological deficit. Curves 100° and above were at higher risk for complications.

CONCLUSIONS

Postoperative complications were seen in 20% of surgically treated patients with complex spine deformities at a Scoliosis Research Society SRS Global Outreach Program site. Three-column osteotomies were identified as an independent risk factor of both postoperative complications and neurological deficits. The significant observed correlation of 3-column osteotomies and postoperative neurological deficits should serve as a guide for surgeons in the preoperative planning and management of severe spinal deformities, especially in locations with limited resources. Patients undergoing correction of large curves may also have a higher complication rate.

What makes a "great resident": the resident perspective

Orthopedic surgery residency training is a difficult endeavor, and the selection of residents that will perform well in a rigorous training program is challenging for residency program directors. Even defining a "great" resident is a difficult endeavor. However, there are certain qualities that anecdotally are associated with high-performing residents, which include being trustworthy, hard-working and efficient, self-directed learners, detail-oriented, and personable. These qualities are difficult to teach and are likely learned by an individual during their early years of education and groomed during college and medical school. Individuals possessing these characteristics are more likely to bring a high-level of professionalism to their work as residents and to perform well on objective measures of success in residency such as high OITE scores, good faculty evaluations, and peer-reviewed publications. We discuss the available, but limited, literature on what makes a "great" resident and share the resident perspective on this topic.

Popliteal venotomy during posterior cruciate ligament reconstruction in the setting of a popliteal artery bypass graft

Injury to the vascular structures in the popliteal fossa during arthroscopic cruciate ligament reconstruction can be limb threatening or even life threatening. We present the first report, to our knowledge, of an isolated injury to a popliteal vein during arthroscopic posterior cruciate ligament reconstruction. Unfortunately, the venotomy led to cardiopulmonary arrest and flash pulmonary edema in this patient. Preoperative planning is paramount to assess risk of injury to vascular structures, which may be increased in patients who have had prior procedures on the affected knee. Furthermore, vascular surgery consultation preoperatively after a magnetic resonance angiogram or venogram and avoiding the use of epinephrine in the arthroscopy fluid should be considered when performing these higher-risk procedures.

Direct membrane association drives mitochondrial fission by the Parkinson disease-associated protein alpha-synuclein

The protein α-synuclein has a central role in Parkinson disease, but the mechanism by which it contributes to neural degeneration remains unknown. We now show that the expression of α-synuclein in mammalian cells, including neurons in vitro and in vivo, causes the fragmentation of mitochondria. The effect is specific for synuclein, with more fragmentation by α- than β- or γ-isoforms, and it is not accompanied by changes in the morphology of other organelles or in mitochondrial membrane potential. However, mitochondrial fragmentation is eventually followed by a decline in respiration and neuronal death. The fragmentation does not require the mitochondrial fission protein Drp1 and involves a direct interaction of synuclein with mitochondrial membranes. In vitro, synuclein fragments artificial membranes containing the mitochondrial lipid cardiolipin, and this effect is specific for the small oligomeric forms of synuclein. α-Synuclein thus exerts a primary and direct effect on the morphology of an organelle long implicated in the pathogenesis of Parkinson disease.

The behavior of alpha-synuclein in neurons

Despite considerable evidence linking alpha-synuclein with membranes in vitro, it has proven difficult to demonstrate membrane association of the protein in vivo. alpha-Synuclein localizes to the nerve terminal, but biochemical experiments have not revealed a tight association with membranes. To address the dynamics of the protein in live cells, we have used photobleaching and found that alpha-synuclein exhibits high mobility, although distinctly less than an entirely soluble protein. Further, neural activity controls the distribution of alpha-synuclein, causing its dispersion from the synapse. In addition to the presumed role of alpha-synuclein dynamics in synaptic function, changes in its physiological behavior may underlie the pathological changes associated with Parkinson's disease.

Neural activity controls the synaptic accumulation of alpha-synuclein

The presynaptic protein alpha-synuclein has a central role in Parkinson's disease (PD). However, the mechanism by which the protein contributes to neurodegeneration and its normal function remain unknown. Alpha-synuclein localizes to the nerve terminal and interacts with artificial membranes in vitro but binds weakly to native brain membranes. To characterize the membrane association of alpha-synuclein in living neurons, we used fluorescence recovery after photobleaching. Despite its enrichment at the synapse, alpha-synuclein is highly mobile, with rapid exchange between adjacent synapses. In addition, we find that alpha-synuclein disperses from the nerve terminal in response to neural activity. Dispersion depends on exocytosis, but unlike other synaptic vesicle proteins, alpha-synuclein dissociates from the synaptic vesicle membrane after fusion. Furthermore, the dispersion of alpha-synuclein is graded with respect to stimulus intensity. Neural activity thus controls the normal function of alpha-synuclein at the nerve terminal and may influence its role in PD.

Effects of 23.4% sodium chloride solution in reducing intracranial pressure in patients with traumatic brain injury: a preliminary study

OBJECTIVE

Mannitol is the standard of care for patients with increased intracranial pressure (ICP), but multiple administrations of mannitol risk renal toxicity and fluid accumulation in the brain parenchyma with consequent worsening of cerebral edema. This preliminary study assessed the safety and efficacy of small-volume injections of 23.4% sodium chloride solution for the treatment of intracranial hypertension in patients with traumatic brain injury who became tolerant to mannitol.

METHODS

We retrospectively reviewed the charts of 13 adult patients with traumatic brain injury who received mannitol and 23.4% sodium chloride independently for the treatment of intracranial hypertension at San Francisco General Hospital between January and October 2003. Charts were reviewed to determine ICP, cerebral perfusion pressure, mean arterial pressure, serum sodium values, and serum osmolarity before and after treatment with 23.4% sodium chloride and mannitol. Complications were noted.

RESULTS

The mean reductions in ICP after treatment were significant for both mannitol (P < 0.001) and hypertonic saline (P < 0.001); there were no significant differences between reductions in ICP when comparing the two agents (P = 0.174). The ICP reduction observed for hypertonic saline was durable, and its mean duration of effect (96 min) was significantly longer than that of mannitol treatment (59 min) (P = 0.016). No complications were associated with treatment with hypertonic saline.

CONCLUSION

This study suggests that 23.4% hypertonic saline is a safe and effective treatment for elevated ICP in patients after traumatic brain injury. These results warrant a rigorous evaluation of its efficacy as compared to mannitol in a prospective randomized controlled trial.

A combinatorial code for the interaction of alpha-synuclein with membranes

Considerable genetic and pathological evidence has implicated the small, soluble protein alpha-synuclein in the pathogenesis of familial and sporadic forms of Parkinsons disease (PD). However, the precise role of alpha-synuclein in the disease process as well as its normal function remain poorly understood. We recently found that an interaction with lipid rafts is crucial for the normal, pre-synaptic localization of alpha-synuclein. To understand how alpha-synuclein interacts with lipid rafts, we have now developed an in vitro binding assay to rafts purified from native membranes. Recapitulating the specificity observed in vivo, recombinant wild type but not PD-associated A30P mutant alpha-synuclein binds to lipid rafts isolated from cultured cells and purified synaptic vesicles. Proteolytic digestion of the rafts does not disrupt the binding of alpha-synuclein, indicating an interaction with lipid rather than protein components of these membranes. We have also found that alpha-synuclein binds directly to artificial membranes whose lipid composition mimics that of lipid rafts. The binding of alpha-synuclein to these raft-like liposomes requires acidic phospholipids, with a preference for phosphatidylserine (PS). Interestingly, a variety of synthetic PS with defined acyl chains do not support binding when used individually. Rather, the interaction with alpha-synuclein requires a combination of PS with oleic (18:1) and polyunsaturated (either 20:4 or 22:6) fatty acyl chains, suggesting a role for phase separation within the membrane. Furthermore, alpha-synuclein binds with higher affinity to artificial membranes with the PS head group on the polyunsaturated fatty acyl chain rather than on the oleoyl side chain, indicating a stringent combinatorial code for the interaction of alpha-synuclein with membranes.

Emerging role of gap junctions in epilepsy

This review highlights the contribution of gap junctions to the pathophysiology of epilepsy. The tissue expression and spatiotemporal regulation of connexins is discussed, and the phenotypes of specific connexin knockouts are considered. Electrophysiologic studies have implicated gap junctions in the generation of very fast oscillations preceding seizures. Gap junction inhibitors have shown powerful anticonvulsant effects, to date primarily in in vitro studies. Specific inhibition of gap junctions in vivo along with more detailed human tissue studies are needed to understand more fully the role of gap junctions in epileptogenesis.