Detection of locomotion deficit in a post-traumatic syringomyelia rat model using automated gait analysis technique.

Syringomyelia (SM) is a spinal cord disorder in which a cyst (syrinx) filled with fluid forms in the spinal cord post-injury/disease, in patients syrinx symptoms include loss of pain and temperature sensation or locomotion deficit. Currently, there are no small animal models and connected tools to help study the functional impacts of SM. The objective of this study was to determine the detectability of subtle locomotion deficits due to syrinx formation/expansion in post-traumatic syringomyelia (PTSM) rat model using the recently reported method of Gait Analysis Instrumentation, and Technology Optimized for Rodents (GAITOR) with Automated Gait Analysis Through Hues and Areas (AGATHA) technique. First videos of the rats were collected while walking in an arena (using GAITOR) followed by extracting meaningful locomotion information from collected videos using AGATHA protocol. PTSM injured rats demonstrated detectable locomotion deficits in terms of duty factor imbalance, paw placement accuracy, step contact width, stride length, and phase dispersion parameters compared to uninjured rats due to SM. We concluded that this technique could detect mild and subtle locomotion deficits associated with PTSM injury, which also in future work could be used further to monitor locomotion responses after different treatment strategies for SM.

Multilevel Hemilaminotomy Windows for the Surgical Management of Spinal Epidural Lipomatosis Causing Syringomyelia: Technical Note and Literature Review.

BACKGROUND: Spinal epidural lipomatosis (SEL) is the excessive accumulation of extradural adipose tissue. Severe cases could result in myelopathy, and very rarely, in syringomyelia formation. Surgery has been associated with high morbidity and mortality, and no proven long-term benefits. The objective was to provide a technical description of an efficient and cost-effective procedure for multilevel thoracic decompression without requiring spinal instrumentation. METHODS: A technique of multilevel hemilaminotomy windows is described in a patient with severe thoracic SEL causing syringomyelia. A 3-dimensional spine model was created to illustrate the technique and working angles. We performed a literature review by searching PubMed, Ovid Embase, and Scopus electronic databases with the predetermined inclusion criteria of cases with spinal lipomatosis and a fluid cavity within the spinal cord. RESULTS: The patient's deficit and syringomyelia resolved postoperatively. A review of the literature revealed only 3 cases of syringomyelia secondary to SEL. Syringomyelia expansion occurred in all cases leading to progressive neurologic decline, and surgery with removal of the excessive adipose tissue resolved the syringomyelia and improved the neurologic functioning in all cases. CONCLUSIONS: This technique of multilevel alternating hemilaminotomy "windows" allows for safe and effective decompression and resection of the excessive adipose tissue with reduced operative time and without requiring spine instrumentation. The technique maintains the integrity of the posterior column, thus reducing the risk of postdecompression deformity. Careful bipolar electrocoagulation of internal vertebral veins and meticulous hemostasis is key for minimizing the intraoperative blood loss and avoiding postoperative hematoma formation.

Turbulent Cerebrospinal Fluid Flow in Enlarging Terminal Myelocystocele.

Terminal myelocystocele is a rare type of neural tube malformation, consisting of a skin-covered lumbosacral mass, highly associated with other complex abdominal malformations within the OIES complex (omphalocele, imperforate anus, exstrophy of the cloaca and spinal defects). We present a case of a premature female with an extensive lumbosacral mass at birth, as well as an omphalocele, cloacal exstrophy, renal abnormalities, and sacral agenesis. Lumbar magnetic resonance imaging revealed a meningocele sac herniating through the bone defects and containing a syringocele sac. Advanced imaging techniques showed turbulent cerebrospinal fluid flow. At control, 4 weeks later, the defect doubled in size. The myelocystocele sac was evacuated and closed, and the patient persisted with paraparesis. The role of cerebrospinal fluid flow analysis is well established in Chiari-type malformations, in which turbulent flow within the syrinx is related to a better outcome after surgery. It is possible that the same principle could be applied to other spinal malformations, as shown in this case of terminal myelocystocele.

Is C1-C2 Reduction and Fixation A Good Choice in the Treatment of Recurrent Chiari-Like Symptoms With Syringomyelia?

BACKGROUND: Foramen magnum decompression (FMD) is the first-choice treatment for Chiari malformation (CM). However, it has been suggested that cerebellar herniation and syringomyelia occur as a natural protective event to prevent neural damage caused by atlantoaxial instability. It is argued that treating instability is the main treatment. Positive results of atlantoaxial fusion have been reported in the literature, but there are no studies including the results of atlantoaxial fusion as the second treatment in patients in whom classical decompression failed. In our study, we report the results of these patients to help in the selection of treatment and we present our treatment algorithm for CM with syringomyelia. METHODS: Thirteen patients who had undergone FMD and duraplasty due to CM and syringomyelia in our clinics and who had recovered clinically and radiologically but had recurrent complaints during long-term follow-up were evaluated. C1-C2 distraction and fusion were performed. We evaluated these patients radiologically and clinically. RESULTS: The mean age of the 13 patients was found to be 32.4 years. Male to female ratio was 6:7. The complaints recurred after an average of 2.1 years. Also, 3 cases were presented with their clinical characteristics and radiologic findings. CONCLUSIONS: FMD may fail even with duraplasty, and treatment of CM in recurrent cases is still controversial. Recently, atlantoaxial instability has been reported to be the main pathology of CM, and the cure for pathology is to treat instability. Recurrent CMs with syringomyelia in which FMD has failed should be treated by atlantoaxial fixation.

Outcomes of Dura Splitting Decompression Versus Posterior Fossa Decompression With Duraplasty in the Treatment of Chiari I Malformation: A Systematic Review and Meta-analysis.

BACKGROUND: Surgery is the definitive treatment option for symptomatic Chiari malformation I (CMI), but there is no clear consensus as to the preferred surgical method. This study aimed to quantitatively assess and compare the effect and safety of dura splitting decompression (DSD) and posterior fossa decompression with duraplasty (PFDD) in treating patients with CMI. METHODS: A literature search of EMBASE, MEDLINE, PubMed, Cochrane Library, and Web of Science databases was conducted. References from January 1990 to September 2020 were retrieved. We only included papers containing original data, comparing the use of DSD and PFDD in CMI patients. RESULTS: Overall, 11 relevant studies were identified, wherein 443 patients treated for CMI by DSD were compared with 261 patients treated by PFDD. No difference was observed between PFDD and PFD in terms of clinical improvement (P = 0.69), syringomyelia improvement (P = 0.90), or reoperation (P = 0.22). DSD was associated with shorter operation durations (P = 0.0007), shorter length of stay (P = 0.0007), and shorter overall postoperative complications (P < 0.0001) (especially cerebrospinal fluid [CSF] leak [P = 0.005], meningitis [P = 0.002], and pseudomeningocele [P = 0.002]), as compared with PFDD. CONCLUSIONS: This study confirmed that dura splitting decompression has clinical and syringomyelia improvement outcomes comparable to posterior fossa decompression with duraplasty. Compared with PFDD, DSD not only significantly shortened the operation time and length of stay, but also significantly reduced the overall complication rate, especially those related to incidence of CSF-related complications. More evidence from advanced multicenter studies are needed to require to validate the findings.

Management of Chiari malformation type I and syringomyelia during pregnancy and delivery.

OBJECTIVE: Although a recurrent question in clinical practice, the management of Chiari malformation type I (CMI) and/or syringomyelia during pregnancy and delivery is still debated. The aim of this study was to investigate the modalities of delivery and anesthesia in women presenting with CMI and/or syringomyelia at a national reference center, and to question their potential role in the natural history of these conditions. STUDY DESIGN: We conducted a retrospective cohort study using a standardized questionnaire, a customized clinical severity score and data from medical records. RESULTS: 83 patients were included in the final analysis: 32 had CMI without syringomyelia, 27 had CMI with syringomyelia and 24 had non-foraminal syringomyelia. Most patients (55/83) were not diagnosed at the time of their pregnancy, 12 had surgery before being pregnant and 16 were diagnosed but not operated. Most women underwent vaginal delivery (62 %) and neuraxial (i.e. epidural or spinal) anesthesia (69 %). However, the proportion of cesarean procedures increased to 53.6 % and even 83.3 % when considering only patients already diagnosed or operated on, respectively. Nonetheless, neither vaginal compared to cesarean delivery (change in clinically severity score: -1.5 ± 0.4 versus -0.9 ± 0.4, p = 0.4) nor neuraxial compared to general anesthesia (-1.2 ± 0.3 versus -1.5 ± 0.6, p = 0.7) were associated with increased clinical deterioration. CONCLUSION: Although individual evaluation is mandatory, this study supports that neither delivery nor anesthesia modalities affect the natural history for the vast majority of patients with CMI and/or syringomyelia.

A Combinatorial Approach with Cerebellar Tonsil Suspension to Treating Symptomatic Chiari Malformation Type I in Adults: A Retrospective Study.

BACKGROUND: Primary Chiari malformations (CMs) are congenital defects of the skull base and brain. Among the 4 CM types, type I (CM-I) occurs most frequently and may cause somatosensorimotor, autonomic and vision symptoms. Presently, posterior fossa decompression alone (PFD) or with duraplasty (PFDD) and cerebellar tonsil (CbT) shrinkage tactics are standard treatments, albeit inherent issues. There has been no report on devising CbT suspension (CTS) to manage CM-I. OBJECTIVES: 1) To design a CTS protocol that can be used with CbT coagulation (CTC) and PFDD; 2) to evaluate the regimen for feasibility, safety, and efficacy in a retrospective study; and 3) to obtain data for planning prospective studies to validate PFDD + CTC + CTS as a novel approach to treating adult CM-I. METHODS: PFDD + CTC + CTS (n = 17), PFDD + CTC (n = 13), and PFDD (n = 12) were performed for 42 adult patients (age range, 18-55 years; female:male = 27:15) following a balanced study design. Neck Disability Index (NDI), Chicago Chiari Outcome Scale (CCOS), and /magnetic resonance imaging/computed tomography were used to determine postsurgery outcomes for approximately 20 months. RESULTS: Comparing to PFDD + CTC or PFDD, patients receiving PFDD + CTC +CTS operation exhibited significantly improved group average NDI (10.72 ± 3.95%; P = 0.007), CbT elevation distance (7.06 ± 2.42 mm; P < 0.001, Kruskal-Wallis test; 55.7 ± 25.4% higher than the presurgery level; P < 0.001, analysis of variance), and syringomyelia syrinx retraction (P = 0.009, analysis of variance). CONCLUSIONS: The PFDD + CTC + CTS regimen appeared to be safe and potentially more efficacious in patients with CM-I evaluated for the period, relative to PFDD + CTC or PFDD treatment. Future prospective studies were warranted.

Somatosensory and motor evoked potentials during correction surgery of scoliosis in neurologically asymptomatic Chiari malformation-associated scoliosis: A comparison with idiopathic scoliosis.

OBJECTIVES: To analyze the somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) in neurologically asymptomatic Chiari malformation-associated scoliosis (CMS) patients with and without syringomyelia as compared with those in idiopathic scoliosis (IS) ones, and to identify whether the deformities have impacts on the neurophysiological monitoring. PATIENTS AND METHODS: This study included neurologically asymptomatic CMS patients undergoing posterior correction surgery between January 2010 and January 2016. IS patients were involved as control group and a subgroup of age- and height-matched IS patients were selected. The age, standing height and Cobb angles of main curve were measured. The SEPs latency and amplitude, MEPs amplitude, and the rate of abnormal SEPs pathologic change were compared between CMS and IS patients using independent-sample t-test and Chi-square test. RESULTS: Sixty CMS patients and 210 IS patients were included. There was no difference between CMS patients and IS or matched IS patients in SEPs latency and amplitude, MEPs amplitude or rate of abnormal SEPs (p > 0.05). Forty-eight CMS patients concurrent with syringomyelia were associated with higher Cobb angle of main curve and lower SEPs amplitude than those without syringomyelia (p < 0.05). No significant difference was found between CMS patients with and without syringomyelia in age, height, SEPs latency, MEPs amplitude or rate of abnormal SEPs (p > 0.05). CONCLUSION: Neurologically asymptomatic CMS patients showed similar absolute values of neurophysiological monitoring with IS patients. The syringomyelia in CMS indicated more severe curvature and lower SEPs amplitude even after posterior fossa decompression.

Clinical and radiological outcomes of arachnoid-preseving suboccipital decompression for adult chiari I malformation with and without syringomyelia.

OBJECTIVE: To share our experience related to clinic and radiologic outcomes of patients with Chiari I malformation. PATIENTS AND METHODS: This retrospective study evaluated surgical outcome of 48 patients who underwent posterior fossa decompression and duraplasty with arachnoid-preservation technique February 2010 and February 2019. Clinic and radiologic outcomes at long-term follow-up were provided. RESULTS: Surgery led to satisfactory outcomes in both clinic and radiologic measures. The majority of patients (66.7%) in the follow-up period informed us that their symptoms significantly improved. In 14 patients (29.2%), the symptoms were gone totally and no complaining was reported to us. Syringomyelia was encountered in 21 patients (43.7%) on pre-operative MRI. During long-term, significant improvement (syrinx segments were remarkably reduced in diameter) in syrinx size was noted in 16 of the 21 patients (76.1%). In 5 of the 21 patients (23.8), complete improvement, that is, syrinxes were totally collapsed, was seen. Surgery-related complications occurred in a total of 5 patients (10.4%). CONCLUSION: In our experience, we found decompressive craniectomy wide enough with duraplasty without arachnoid opening is safe and successful in patients with CIM. Complication rate is low and arachnoid preserving technique should be performed by experienced neurosurgeons.

The Chiari I malformation.

As with many pathologies, the course of our understanding of the Chiari I malformation (CIM) has developed extensively over time. The early descriptions of the Chiari malformations by Hans Chiari in 1891 opened the door for future classification and research on this topic. However, even over a long timeframe, our understanding of the pathophysiology and, more importantly, treatment, remained in its infancy. As recently as the 1970s, CIM was not discussed in popular neurology textbooks. Syringomyelia is listed as a degenerative disorder with no satisfactory treatment. Radiation therapy was considered an option in treatment, and surgery was thought to play no role. During the last 40 years, equivalent to the duration of a neurosurgical career, our understanding of the pathophysiology and natural history of CIM, coupled with modern MRI, has improved the treatment paradigm for this patient population. More importantly, it has given us evidence confirming that CIM is a disorder responsive to surgical intervention, giving patients once thought to be destined for lifelong disability a comparatively normal life after treatment. The purpose of this article is to offer a review of CIM and its important associated entities. The authors will discuss the evolution in understanding of the Chiari malformation and, importantly, distinguish between symptomatic CIM and asymptomatic tonsillar ectopia, based on imaging and presenting symptomatology. They will discuss techniques for surgical intervention, expected outcomes, and complications after surgery. Proper patient selection for surgery based on appropriate symptomatology is tantamount to achieving good surgical outcomes in this population, separating those who can be helped by surgery from those who are unlikely to improve. While our knowledge of the Chiari malformations continues to improve through the efforts of clinical and basic science researchers, surgeons, and patients, our current understanding of these entities represents a monumental improvement in patient care over a relatively short time period.

Peripheral nerve hyperexcitability.

Neuromyotonic and myokymic discharges are abnormal electrical muscular discharges caused by ectopic discharges from motor axons and represent the hallmarks of peripheral nerve hyperexcitability. Neuromyotonic discharges are specific for peripheral nerve hyperexcitability syndromes, whereas myokymic discharges may occur either focally or in a more generalized fashion in many other peripheral nerve disorders. Isaacs syndrome and Morvan syndrome are rare acquired peripheral nerve hyperexcitability disorders that share common clinical features and are often associated with elevated voltage-gated potassium channel-complex antibodies. Central nervous system symptomatology is more common in Morvan syndrome, which also overlaps with limbic encephalitis. Cramp-fasciculation syndrome, a more common syndrome, may represent a milder form of peripheral nerve hyperexcitability. Peripheral nerve hyperexcitability syndromes should be distinguished from stiff person syndrome, myotonic disorders, and rippling muscle disease. When severe, Isaacs syndrome and Morvan syndrome may be disabling but often respond to membrane-stabilizing drugs and immunomodulatory treatments. The electrophysiologic features of these disorders are described.

Effect of extradural constriction on CSF flow in rat spinal cord.

BACKGROUND: Fluid homeostasis in the central nervous system (CNS) is essential for normal neurological function. Cerebrospinal fluid (CSF) in the subarachnoid space and interstitial fluid circulation in the CNS parenchyma clears metabolites and neurotransmitters and removes pathogens and excess proteins. A thorough understanding of the normal physiology is required in order to understand CNS fluid disorders, including post-traumatic syringomyelia. The aim of this project was to compare fluid transport, using quantitative imaging of tracers, in the spinal cord from animals with normal and obstructed spinal subarachnoid spaces. METHODS: A modified extradural constriction model was used to obstruct CSF flow in the subarachnoid space at the cervicothoracic junction (C7-T1) in Sprague-Dawley rats. Alexa-Fluor 647 Ovalbumin conjugate was injected into the cisterna magna at either 1 or 6 weeks post-surgery. Macroscopic and microscopic fluorescent imaging were performed in animals sacrificed at 10 or 20 min post-injection. Tracer fluorescence intensity was compared at cervical and thoracic spinal cord levels between control and constriction animals at each post-surgery and post-injection time point. The distribution of tracer around arterioles, venules and capillaries was also compared. RESULTS: Macroscopically, the fluorescence intensity of CSF tracer was significantly greater in spinal cords from animals with a constricted subarachnoid space compared to controls, except at 1 week post-surgery and 10 min post-injection. CSF tracer fluorescence intensity from microscopic images was significantly higher in the white matter of constriction animals 1 week post surgery and 10 min post-injection. At 6 weeks post-constriction surgery, fluorescence intensity in both gray and white matter was significantly increased in animals sacrificed 10 min post-injection. At 20 min post-injection this difference was significant only in the white matter and was less prominent. CSF tracer was found predominantly in the perivascular spaces of arterioles and venules, as well as the basement membrane of capillaries, highlighting the importance of perivascular pathways in the transport of fluid and solutes in the spinal cord. CONCLUSIONS: The presence of a subarachnoid space obstruction may lead to an increase in fluid flow within the spinal cord tissue, presenting as increased flow in the perivascular spaces of arterioles and venules, and the basement membranes of capillaries. Increased fluid retention in the spinal cord in the presence of an obstructed subarachnoid space may be a critical step in the development of post-traumatic syringomyelia.

Fluid dynamics in syringomyelia cavities: Effects of heart rate, CSF velocity, CSF velocity waveform and craniovertebral decompression.

Purpose How fluid moves during the cardiac cycle within a syrinx may affect its development. We measured syrinx fluid velocities before and after craniovertebral decompression in a patient and simulated syrinx fluid velocities for different heart rates, syrinx sizes and cerebrospinal fluid (CSF) flow velocities in a model of syringomyelia. Materials and methods With phase-contrast magnetic resonance we measured CSF and syrinx fluid velocities in a Chiari patient before and after craniovertebral decompression. With an idealized two-dimensional model of the subarachnoid space (SAS), cord and syrinx, we simulated fluid movement in the SAS and syrinx with the Navier-Stokes equations for different heart rates, inlet velocities and syrinx diameters. Results In the patient, fluid oscillated in the syrinx at 200 to 210 cycles per minute before and after craniovertebral decompression. Velocities peaked at 3.6 and 2.0 cm per second respectively in the SAS and the syrinx before surgery and at 2.7 and 1.5 cm per second after surgery. In the model, syrinx velocity varied between 0.91 and 12.70 cm per second. Increasing CSF inlet velocities from 1.56 to 4.69 cm per second increased peak syrinx fluid velocities in the syrinx by 151% to 299% for the three cycle rates. Increasing cycle rates from 60 to 120 cpm increased peak syrinx velocities by 160% to 312% for the three inlet velocities. Peak velocities changed inconsistently with syrinx size. Conclusions CSF velocity, heart rate and syrinx diameter affect syrinx fluid velocities, but not the frequency of syrinx fluid oscillation. Craniovertebral decompression decreases both CSF and syrinx fluid velocities.

Intracranial hypotension and hypertension: reversible Chiari malformation due to dynamic cerebrospinal fluid abnormalities in Gorham-Stout disease. Case report.

Gorham-Stout disease (GSD) is an intractable disease characterized by massive osteolysis caused by abnormal lymphangiogenesis in bone. In rare cases of GSD, CSF abnormalities develop. The authors present the case of a 19-year-old woman with GSD presenting with orthostatic headache due to intracranial hypotension (5 cm H2O). The clinical course of this case was very unusual. Orthostatic headache was associated with a CSF leak from the thigh after pathological fractures of the femur and pelvis. The chronic CSF leak led to acquired Chiari malformation (CM) with syringomyelia. After an epidural blood patch, her neurological status improved; however, after the complete arrest of the CSF leak from the thigh, she presented with severe nonpostural headache and progressive visual acuity loss with optic papilledema. A ventriculoperitoneal shunt was placed to treat intracranial hypertension (50 cm H2O). Headache improved and optic papilledema decreased after shunt surgery. This case shows that dynamic CSF abnormalities may lead to reversible CM in patients with GSD. Sealing a CSF leak rather than performing suboccipital decompression is recommended for acquired CM resulting from a CSF leak.

A points-based algorithm for prognosticating clinical outcome of Chiari malformation Type I with syringomyelia: results from a predictive model analysis of 82 surgically managed adult patients.

OBJECTIVE Although various predictors of postoperative outcome have been previously identified in patients with Chiari malformation Type I (CMI) with syringomyelia, there is no known algorithm for predicting a multifactorial outcome measure in this widely studied disorder. Using one of the largest preoperative variable arrays used so far in CMI research, the authors attempted to generate a formula for predicting postoperative outcome. METHODS Data from the clinical records of 82 symptomatic adult patients with CMI and altered hindbrain CSF flow who were managed with foramen magnum decompression, C-1 laminectomy, and duraplasty over an 8-year period were collected and analyzed. Various preoperative clinical and radiological variables in the 57 patients who formed the study cohort were assessed in a bivariate analysis to determine their ability to predict clinical outcome (as measured on the Chicago Chiari Outcome Scale [CCOS]) and the resolution of syrinx at the last follow-up. The variables that were significant in the bivariate analysis were further analyzed in a multiple linear regression analysis. Different regression models were tested, and the model with the best prediction of CCOS was identified and internally validated in a subcohort of 25 patients. RESULTS There was no correlation between CCOS score and syrinx resolution (p = 0.24) at a mean ± SD follow-up of 40.29 ± 10.36 months. Multiple linear regression analysis revealed that the presence of gait instability, obex position, and the M-line-fourth ventricle vertex (FVV) distance correlated with CCOS score, while the presence of motor deficits was associated with poor syrinx resolution (p ≤ 0.05). The algorithm generated from the regression model demonstrated good diagnostic accuracy (area under curve 0.81), with a score of more than 128 points demonstrating 100% specificity for clinical improvement (CCOS score of 11 or greater). The model had excellent reliability (κ = 0.85) and was validated with fair accuracy in the validation cohort (area under the curve 0.75). CONCLUSIONS The presence of gait imbalance and motor deficits independently predict worse clinical and radiological outcomes, respectively, after decompressive surgery for CMI with altered hindbrain CSF flow. Caudal displacement of the obex and a shorter M-line-FVV distance correlated with good CCOS scores, indicating that patients with a greater degree of hindbrain pathology respond better to surgery. The proposed points-based algorithm has good predictive value for postoperative multifactorial outcome in these patients.

Functional Impairments in a Patient with Morvan Syndrome: A Case Presentation.

A 48-year-old man with lung squamous cell carcinoma was admitted to acute care with cognitive impairment after recent chemotherapy. He developed myoclonus, ataxia, agitation, and visual hallucinations. Morvan syndrome, a rare voltage-gated potassium channel antibody disorder characterized by neuromyotonia with central nervous system dysfunction, was eventually diagnosed. He received plasmapheresis and was admitted to inpatient rehabilitation, where he safely participated in therapies. By focusing on neuromuscular rehabilitation, balance training, fine motor skills, and cognitive retraining emphasizing skills relevant to the patient's premorbid cognitive activities, the patient demonstrated significant functional improvement, decreasing the burden of care of his caregivers. LEVEL OF EVIDENCE: V.

Intradural pathology and pathophysiology associated with Chiari I malformation in children and adults with and without syringomyelia.

OBJECTIVE The pathophysiology underlying tonsillar herniation and CSF obstruction in Chiari malformation Type I (CM-I) is unclear, and the cause of CM-I-associated syringomyelia is not well understood. A better understanding of this pathophysiology is important for an improved treatment strategy. Therefore, the authors sought to identify, characterize, and examine the intradural pathology and CSF flow pathophysiology in the posterior fossa and at the level of the foramen magnum that occurs in the setting of CM-I. They determined the incidence of these intradural findings and assessed differences across age, with the degree of tonsillar herniation, and in the presence and absence of syringomyelia. METHODS A prospective database initiated in March 2003 recorded all intraoperative findings during surgical treatment of children and adults with CM-I with or without syringomyelia. A total of 389 surgeries for CM-I were performed in 379 patients between March 2003 and June 2016. A total of 109 surgeries were performed in 109 patients with CM-I (without osseoligamentous abnormalities) in whom both a posterior fossa extradural and intradural decompression with duraplasty was performed (first-time intradural procedures). Using a surgical microscope, intradural pathology and obstruction of CSF channels were identified and assessed. Student t-tests and Fisher's exact tests compared groups in a series of univariate analyses, followed by multivariate logistic regression. RESULTS The following intradural pathological entities were observed (prevalence noted in parentheses). These include those that did not obstruct CSF flow channels: opacified arachnoid (33.0%), thickened arachnoid (3.7%), ischemic and gliotic tonsils (40.4%), tonsillar cysts (0.9%), and inferior descent of the fourth ventricle and cervicomedullary junction (CMJ) (78.0%). The following intradural pathological entities were observed to obstruct CSF flow channels: medialized tonsils (100%), tonsil overlying and obstructing the foramen of Magendie (21.1%), intertonsillar and tonsil to CMJ arachnoid adhesions (85.3%), vermian posterior inferior cerebellar artery branches obstructing the foramen of Magendie (43.1%), and arachnoid veils or webs obstructing or occluding the foramen of Magendie (52.3%). Arachnoid veils varied in type and were observed in 59.5% of patients with CM-I who had syringomyelia, which was significantly greater than the 33.3% of patients with CM-I without syringomyelia who had an arachnoid veil (p = 0.018). The presence of CM-I with an arachnoid veil had 3.22 times the odds (p = 0.013, 95% CI 1.29-8.07, by multivariate logistic regression) of being associated with syringomyelia, adjusting for tonsillar herniation. The inferior descent of the fourth ventricle and CMJ occurred with a greater degree of tonsillar herniation (p < 0.001) and correlated with a cervicomedullary kink or buckle on preoperative MRI. CONCLUSIONS Intradural pathology associated with CM-I with or without syringomyelia exists in many forms, is more prevalent than previously recognized in patients of all ages, and may play a role in the pathophysiology of CM-I tonsillar herniation. Arachnoid veils appear to partially obstruct CSF flow, are significantly more prevalent in cases of CM-I with syringomyelia, and therefore may play a role in the pathophysiology of CM-I-associated syringomyelia.

A rat model of chronic syringomyelia induced by epidural compression of the lumbar spinal cord.

OBJECTIVE There has been no established animal model of syringomyelia associated with lumbosacral spinal lipoma. The research on the pathophysiology of syringomyelia has been focused on Chiari malformation, trauma, and inflammation. To understand the pathophysiology of syringomyelia associated with occult spinal dysraphism, a novel animal model of syringomyelia induced by chronic mechanical compression of the lumbar spinal cord was created. METHODS The model was made by epidural injection of highly concentrated paste-like kaolin solution through windows created by partial laminectomy of L-1 and L-5 vertebrae. Behavioral outcome in terms of motor (Basso-Beattie-Bresnahan score) and urinary function was assessed serially for 12 weeks. Magnetic resonance images were obtained in some animals to confirm the formation of a syrinx and to monitor changes in its size. Immunohistochemical studies, including analysis for glial fibrillary acidic protein, NeuN, CC1, ED-1, and caspase-3, were done. RESULTS By 12 weeks after the epidural compression procedure, syringomyelia formation was confirmed in 85% of the rats (34 of 40) on histology and/or MRI. The syrinx cavities were found rostral to the epidural compression. Motor deficit of varying degrees was seen immediately after the procedure in 28% of the rats (11 of 40). In 13 rats (33%), lower urinary tract dysfunction was seen. Motor deficit improved by 5 weeks after the procedure, whereas urinary dysfunction mostly improved by 2 weeks. Five rats (13%, 5 of 40) died 1 month postoperatively or later, and 3 of the 5 had developed urinary tract infection. At 12 weeks after the operation, IHC showed no inflammatory process, demyelination, or accelerated apoptosis in the spinal cords surrounding the syrinx cavities, similar to sham-operated animals. CONCLUSIONS A novel experimental model for syringomyelia by epidural compression of the lumbar spinal cord has been created. The authors hope that it will serve as an important research tool to elucidate the pathogenesis of this type of syringomyelia, as well as the CSF hydrodynamics of the lumbar spinal cord.

Sustained high-pressure in the spinal subarachnoid space while arterial expansion is low may be linked to syrinx development.

Syringomyelia (a spinal cord cyst) usually develops as a result of conditions that cause cerebrospinal fluid (CSF) obstruction. The mechanism of syrinx formation and enlargement remains unclear, though previous studies suggest that the fluid enters via the perivascular spaces (PVS) of the penetrating arteries of the spinal cord, and that alterations in the CSF pulse timing and pressure could contribute to enhanced PVS inflow. This study uses an idealised computational model of the PVS to investigate the factors that influence peri-arterial fluid flow. First, we used three sample patient-specific models to explore whether changes in subarachnoid space (SAS) pressures in individuals with and without syringomyelia could influence PVS inflow. Second we conducted a parametric study to determine how features of the CSF pulse altered perivascular fluid, including alterations to timing and magnitude of the peak SAS pressure, the timing of reversal from high to low pressure (diastolic phase), and the area under the pressure-time curve. The model for the patient with syringomyelia had higher net CSF inflow to the PVS than the two subjects without syringomyelia. In the parametric study, only increasing the area under the high pressure region of the SAS pulse substantially increased PVS inflow, when coupled with a temporal shift in arterial and SAS pulses. This suggests that a period of sustained high SAS pressure while arterial diameter is low may increase net CSF pumping into the PVS.

Aeromedical Evaluation for an F-16 Candidate with Incomplete Paraplegia.

BACKGROUND: A candidate with paraplegia contacted the Institute of Aviation Medicine, Oslo, requesting a medical examination and medical certification for flying back seat on an F-16 Fighting Falcon. Thorough aeromedical examinations, including specialist evaluations, were initiated for the final decision to be made. CASE REPORT: Almost 13 yr earlier the candidate had acquired spinal cord damage at neurological level L1 after falling 4 m (13 ft) from out of a window. The CT scans showed luxation of the 12th thoracic vertebra with fracture and dislocation of the 1st lumbar vertebra. He went for surgery, where fixation of the 12th thoracic vertebra to the 1st lumbar vertebra was performed. He developed syringomyelia 1 yr postoperatively and was re-operated on twice in the following years. He was now in a wheelchair, but engaged himself in several sport activities such as sledge-hockey and sit-skiing, participating in several Paralympics. DISCUSSION: With respect to the general principles of aviation medicine, several considerations had to be taken into account before a medical certification could be given. The risks associated with an F-16 flight in relationship to the candidate's general health and the fixation of his spinal cord had to be evaluated. Also, his ability to perform required tasks during the flight and in case of an emergency was an important issue discussed. Finally, the candidate's medical and physical condition should not present a considerable risk to flight safety. After extensive specialist consultations and in-depth discussions, the candidate was given medical certification to fly back seat in a F-16. Chahal-Kummen M, Strand T-E, Owe JO, Gulliksen E, Wagstaff AS. Aeromedical evaluation for an F-16 candidate with incomplete paraplegia. Aerosp Med Hum Perform. 2016; 87(11):968-971.