A spinal thecal sac constriction model supports the theory that induced pressure gradients in the cord cause edema and cyst formation

Predictive value of magnetic resonance imaging indications of spinal cord swelling for cervical spondylotic myelopathy prognosis

BACKGROUND

Magnetic resonance imaging (MRI) is the preferred examination approach for patients with suspected cervical spondylotic myelopathy (CSM).

OBJECTIVE

To investigate the predictive value of MRI spinal cord swelling on the prognosis of decompression surgery in patients with CSM.

METHODS

A retrospective analysis of 115 patients with CSM who underwent decompression surgery was performed. According to whether cervical MRI showed spinal cord swelling, they were divided into a spinal cord swelling group and non-swelling group. The Modified Japanese Orthopaedic Association (MJOA) score, MJOA improvement rate and abnormal spinal cord enhancement rate in the two groups were compared before and after surgery. Multiple linear regression was used to analyse the influencing factors of the MJOA improvement rate.

RESULTS

The time from symptom onset to operation (t= 2.400, p= 0.018) and preoperative MJOA score in the spinal cord swelling group were lower than those in the non-swelling group (t= 3.253, p= 0.002). The body mass index (t= 2.895, p= 0.005), anteroposterior diameter of the spinal canal (t= 4.421, p< 0.001), cross-sectional area (t= 3.136, p= 0.002), postoperative improvement rate (t= 4.277, p< 0.001) and proportion of abnormal enhancement of the spinal cord in the swelling group were higher than those in the non-swelling group (χ2= 3.136, p= 0.002). The preoperative MJOA score in the swelling group was lower than that in the non-swelling group (t= 2.583, p= 0.013). A multivariate linear regression model revealed that age and spinal cord swelling were independent predictors of MJOA score improvement, explaining 33.2% of the total variation.

CONCLUSION

Patients with CSM with spinal cord swelling have less time from symptoms to surgery, and the degree of preoperative neurological deterioration is more obvious. Spinal cord swelling is an independent predictor of surgical prognosis in patients with CSM.

Challenges in Translating Regenerative Therapies for Spinal Cord Injury

Regenerating the injured spinal cord is a substantial challenge with many obstacles that need to be overcome to achieve robust functional benefits. This abundance of hurdles can partly explain the limited success when applying regenerative intervention treatments in animal models and/or people. In this article, we elaborate on a few of these obstacles, starting with the applicability of animal models and how they compare to the clinical setting. We then discuss the requirement for combinatorial interventions and the associated problems in experimental design, including the addition of rehabilitative training. The article expands on differences in lesion sizes and locations between humans and common animal models, and how this difference can determine the success or failure of an intervention. An additional and frequently overlooked problem in the translation of interventions that applies beyond the field of neuroregeneration is the reporting bias and the lack of transparency in reporting findings. New data mandates are tackling this problem and will eventually result in a more balanced view of the field. Finally, we will discuss strategies to negotiate the challenging course of successful translation to facilitate successful translation of regeneration promoting interventions.

Genetic animal modeling for idiopathic scoliosis research: history and considerations

PURPOSE

Idiopathic scoliosis (IS) is defined as a structural lateral spinal curvature ≥ 10° in otherwise healthy children and is the most common pediatric spinal deformity. IS is known to have a strong genetic component; however, the underlying etiology is still largely unknown. Animal models have been used historically to both understand and develop treatments for human disease, including within the context of IS. This intended audience for this review is clinicians in the fields of musculoskeletal surgery and research.

METHODS

In this review article, we synthesize current literature of genetic animal models of IS and introduce considerations for researchers.

RESULTS

Due to complex genetic and unique biomechanical factors (i.e., bipedalism) hypothesized to contribute to IS in humans, scoliosis is a difficult condition to replicate in model organisms.

CONCLUSION

We advocate careful selection of animal models based on the scientific question and introduce gaps and limitations in the current literature. We advocate future research efforts to include animal models with multiple characterized genetic or environmental perturbations to reflect current understanding of the human condition.

The Histopathology of Severe Graded Compression in Lower Thoracic Spinal Cord Segment of Rat, Evaluated at Late Post-injury Phase

Spontaneous recovery of lost motor functions is relative fast in rodent models after inducing a very mild/moderate spinal cord injury (SCI), and this may complicate a reliable evaluation of the effectiveness of potential therapy. Therefore, a severe graded (30 g, 40 g and 50 g) weight-compression SCI at the Th9 spinal segment, involving an acute mechanical impact followed by 15 min of persistent compression, was studied in adult female Wistar rats. Functional parameters, such as spontaneous recovery of motor hind limb and bladder emptying function, and the presence of hematuria were evaluated within 28 days of the post-traumatic period. The disruption of the blood-spinal cord barrier, measured by extravasated Evans Blue dye, was examined 24 h after the SCI, when maximum permeability occurs. At the end of the survival period, the degradation of gray and white matter associated with the formation of cystic cavities, and quantitative changes of glial structural proteins, such as GFAP, and integral components of axonal architecture, such as neurofilaments and myelin basic protein, were evaluated in the lesioned area of the spinal cord. Based on these functional and histological parameters, and taking the animal’s welfare into account, the 40 g weight can be considered as an upper limit for severe traumatic injury in this compression model.

Harnessing cerebrospinal fluid circulation for drug delivery to brain tissues

Initially thought to be useful only to reach tissues in the immediate vicinity of the CSF circulatory system, CSF circulation is now increasingly viewed as a viable pathway to deliver certain therapeutics deeper into brain tissues. There is emerging evidence that this goal is achievable in the case of large therapeutic proteins, provided conditions are met that are described herein. We show how fluid dynamic modeling helps predict infusion rate and duration to overcome high CSF turnover. We posit that despite model limitations and controversies, fluid dynamic models, pharmacokinetic models, preclinical testing, and a qualitative understanding of the glymphatic system circulation can be used to estimate drug penetration in brain tissues. Lastly, in addition to highlighting landmark scientific and medical literature, we provide practical advice on formulation development, device selection, and pharmacokinetic modeling. Our review of clinical studies suggests a growing interest for intra-CSF delivery, particularly for targeted proteins.

The Role of Astrogliosis in Formation of the Syrinx in Spinal Cord Injury

A massive localized trauma to the spinal cord results in complex pathologic events driven by necrosis and vascular damage which in turn leads to hemorrhage and edema. Severe, destructive and very protracted inflammatory response is characterized by infiltration by phagocytic macrophages of a site of injury which is converted into a cavity of injury (COI) surrounded by astroglial reaction mounted by the spinal cord. The tissue response to the spinal cord injury (SCI) has been poorly understood but the final outcome appears to be a mature syrinx filled with the cerebrospinal fluid with related neural tissue loss and permanent neurologic deficits. This paper reviews known pathologic mechanisms involved in the formation of the COI after SCI and discusses the integrative role of reactive astrogliosis in mechanisms involved in the removal of edema after the injury. A large proportion of edema fluid originating from the trauma and then from vasogenic edema related to persistent severe inflammation, may be moved into the COI in an active process involving astrogliosis and specifically over-expressed aquaporins.

Exploring the potential of RhoA inhibitors to improve exercise-recoverable spinal cord injury: A systematic review and meta-analysis

BACKGROUND

The spinal cord is one of the central nervous system. Spinal cord injury (SCI) will cause loss of physical function and dysfunction below the injury site, causing them to lose sensation and mobility, thereby reducing the quality of life of patients. Although regular rehabilitation management can reduce its severity, the current effective treatment methods are limited to the treatment of secondary injuries to SCI. The purpose of treatment should not only include the restoration of the histology of the lesion, but also should focus on the restoration of sensory and mobility and. The key to effective treatment is to reduce secondary injuries. RhoA inhibitor can improve the pathophysiological changes related to secondary injury and promote the recovery of activity ability, so it may become a clinical drug for the treatment of SCI. This article systematically analyzed the effects of RhoA inhibitors on the promotion of axon regeneration and the recovery of mobility and compared the therapeutic effects of different inhibitors on SCI and their effects on physical function recovery.

METHODS

We used a meta-analysis to systematically evaluate the effects of Rho inhibitors on SCI treatment and the recovery of body function.

RESULTS

21 articles (738 animals) were identified in the literatures search. Studies were selected if they reported the therapeutic effects of RhoA/ROCK inhibitors (BA-210, EGCG, β-elemene, C3-exoenzmye, LINGO-1-Fc, Ibuprofen, SiRhoA, iRhoA + FK506, Fasudil, p21Cip1/WAF1, HA-1007, Y-27,632 and C3bot154-182). We measure the functional recovery by BBB and BMS scores. The random effect model of weighted mean difference (WMD, 95 % confidence interval) was used to analyze the effects. The WMD of the forest graph was 2.277; 95 % CI: 1.705∼2.849, P < 0.001, suggesting that RhoA inhibitors can effectively treat SCI. In addition to EGCG, all the other agents also showed the effects on the activity recovery post-SCI (P < 0.05).

CONCLUSION

β-elemene, LINGO-1-Fc, Ibuprofen, SiRhoA, RhoA + FK506, Fasudil, p21Cip1/WAF1 and Y-27,632 have similar effects to BA-210, they can promote axon germination and nerve fiber regeneration after thoracic spinal cord injury and reduce the formation of syringomyelia and protect white matter, thereby improving locomotor recovery. RhoA inhibitors have great potential to restore motor function and provide a new trend for the treatment of SCI.

Platelet-rich plasma in umbilical cord blood reduces neuropathic pain in spinal cord injury by altering the expression of ATP receptors

BACKGROUND

Neuropathic pain following injury or dysfunction of the peripheral or CNS is one of the most important medical challenges to treat. Humane platelet-rich plasma (HPRP), which is a rich source of growth factors, may be able to treat and reduce pain caused by spinal cord injury (SCI). In this study, the effect of HPRP on neuropathic pain caused by SCI was investigated.

METHODS

Sixty adult male Wistar rats were randomly divided into 6 groups: control, sham, SCI, vehicle (SCI+platelet-poor plasma), SCI+ PRP2day (injection 48 hrs after SCI) and SCI+PRP14day (injection 14 days after SCI). SCI was induced at the T12-T13 level. Behavioral tests were conducted weekly after injury for six weeks. Allodynia and hyperalgesia were assessed using acetone drops, plantar test and von Frey filament. Cavity size and the number of fibroblasts were determined by H&E stain, and the expression of mTOR, p-mTOR, P₂×₃R and P₂Y₄R were determined using the western blot technique. Data were analyzed using PRISM & SPSS software.

RESULTS

PRP injection showed a higher pain threshold in mechanical allodynia (p<0.0001), cold allodynia (p<0.0001) and thermal hyperalgesia (p<0.0001) than those in the spinal. Animals treated with PRP also reduced cavity size, fibroblast number, p-mTOR/mTOR ratio, and P₂×₃R expression, and increased P₂Y₄R expression. The difference between the two groups was not statistically significant.

CONCLUSIONS

The results showed that PRP reduced SCI-induced allodynia and hyperalgesia by regulating ATP signaling. Using HPRP can open a new window in the treatment of pain caused by damage to the nervous system.

Decompressive surgery for treatment of a dorsal compressive atlantoaxial band causing nonambulatory tetraparesis in three toy-breed dogs

CASE DESCRIPTION

3 toy-breed dogs (a 5-year-old Pomeranian, a 12-year-old Pomeranian, and a 13-year-old Yorkshire Terrier) were evaluated because of a sudden onset of nonambulatory tetraparesis.

CLINICAL FINDINGS

In all 3 dogs, MRI revealed a dorsal compressive atlantoaxial (AA) band as the cause of the neurologic deficits. Percentages of dorsal compression of the spinal cord were 28.6%, 31%, and 28.8%.

TREATMENT AND OUTCOME

All 3 dogs underwent decompressive surgery via a dorsal approach. The AA band was removed, and a durotomy was performed, which resulted in spontaneous drainage of a copious amount of CSF. Grossly, the spinal cord parenchyma appeared normal, other than the dorsal compression. To alleviate the AA instability resulting from removal of the dorsal AA ligament, 2-0 polydioxanone was placed in the dorsal cervical muscles extending from the atlantooccipital joint to C2. Postoperatively, all 3 dogs regained normal ambulation between 18 and 30 days after surgery. No complications were reported, and clinical signs did not recur during follow-up times ranging from 4 to 19 months.

CLINICAL RELEVANCE

Findings suggested that surgical treatment may be an effective option in managing dogs with a dorsal compressive AA band causing nonambulatory tetraparesis. Notably, all of the dogs had other craniocervical abnormalities, but none of these abnormalities were considered severe enough to have caused tetraparesis.

Craniovertebral Junction Arachnoiditis: An Unusual Sequelae to Tuberculous Meningitis

Adhesive arachnoiditis at the craniovertebral junction should be suspected in patients with a history of meningitis having delayed onset gradually progressive tetra paresis. Patients can present after an asymptomatic interval of 2 to 20 years. Cardiac gated cine magnetic resonance imaging is useful for its diagnosis. Posterior fossa decompression with upper cervical laminectomy and adhesiolysis appears to be a reasonable treatment for the same. We illustrate two patients who presented to us with gradually progressive spastic tetra paresis; both had prior history of cured tuberculous meningitis.

Spinal cord swelling in patients with cervical compression myelopathy

Background

Intramedullary hyperintense lesions associated with spinal cord edema on T2-weighted MR images (T2WI) are rare findings in patients with cervical spondylosis and are poorly characterized. We investigated the clinical characteristics of spinal cord edema due to cervical spondylosis (SCECS).

Methods

In total, 214 patients with cervical spondylotic myelopathy who underwent surgery between April 2007 and March 2017 were divided into SCECS and non-SCECS groups with SCECS defined as follows: (1) intramedullary signal intensity (ISI) of the cervical spinal cord in sagittal T2WI extending to more than one vertebral body height; (2) “fuzzy” ISI, recognized as a faint intramedullary change with a largely indistinct and hazy border; and (3) a larger sagittal diameter of the spinal cord segment with ISI just above or below the cord compression area compared with areas of the cervical spine without ISI. Radiographic parameters, demographic characteristics, and the Japanese Orthopedic Association (JOA) surgical outcomes score were compared between the groups.

Results

Seventeen patients (7.9%) were diagnosed with SCECS. These patients were younger than those in the non-SCECS group [median (interquartile range), 64 (20) vs. 69 (15) years, respectively, p = 0.016], and the disease duration from onset to surgery was significantly shorter in the SCECS group than in the non-SCECS group [6 (7) vs. 20 (48) months, respectively]. No significant difference was observed between groups with respect to sex, radiologic findings, or surgical outcomes.

Conclusion

The disease showed an earlier onset and more rapid progression in the patients with SCECS than in those without SCECS.

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.

Electronic supplementary material

The online version of this article (10.1186/s12987-019-0127-8) contains supplementary material, which is available to authorized users.

Rat models of spinal cord injury: from pathology to potential therapies

A long-standing goal of spinal cord injury research is to develop effective spinal cord repair strategies for the clinic. Rat models of spinal cord injury provide an important mammalian model in which to evaluate treatment strategies and to understand the pathological basis of spinal cord injuries. These models have facilitated the development of robust tests for assessing the recovery of locomotor and sensory functions. Rat models have also allowed us to understand how neuronal circuitry changes following spinal cord injury and how recovery could be promoted by enhancing spontaneous regenerative mechanisms and by counteracting intrinsic inhibitory factors. Rat studies have also revealed possible routes to rescuing circuitry and cells in the acute stage of injury. Spatiotemporal and functional studies in these models highlight the therapeutic potential of manipulating inflammation, scarring and myelination. In addition, potential replacement therapies for spinal cord injury, including grafts and bridges, stem primarily from rat studies. Here, we discuss advantages and disadvantages of rat experimental spinal cord injury models and summarize knowledge gained from these models. We also discuss how an emerging understanding of different forms of injury, their pathology and degree of recovery has inspired numerous treatment strategies, some of which have led to clinical trials.

Summary: In this Review, we discuss the advantages and disadvantages of the rat for studies of experimental spinal cord injury and summarize the knowledge gained from such studies.

Treatment of Posttubercular Syringomyelia Not Responsive to Antitubercular Therapy: Case Report and Review of Literature

Posttubercular adhesive arachnoiditis is a rare, late complication of tubercular meningitis. Syringomyelia can develop as a consequence of intramedullary cystic lesions and cerebrospinal fluid (CSF) flow disturbance around the spinal cord, even after successful chemotherapy. We reviewed the literature related to posttubercular syringomyelia treatment and suggest a new combined surgical approach. A 25-year-old Nigerian male patient presented with legs numbness, urinary disturbance, and legs weakness. Spinal magnetic resonance revealed a T5-T7 syringomyelia, secondary to adhesive spinal arachnoiditis related to a history of tuberculous meningitis. Adhesiolysis by direct visualization with a flexible endoscope was performed and a handmade S-italic syringe-subdural shunt was placed to restore CSF flow. During the postoperative course, the neurological deficits improved together with the resolution of the syrinx. Long-term magnetic resonance imaging follow-up documented no recurrences or shunt displacements. We suggest that, when antitubercular therapy is not effective to resolve postarachnoiditis syrinx, arachnolysis with a flexible endoscope together with the placement of an S-italic shunt allowed free CSF communication between the syrinx and the subarachnoid space. Furthermore, we support that the use of an s-shaped shunt could prevent displacement or migration of the device and allows an easier revision in case of acute or late complications.

Dorsal compressive atlantoaxial bands and the craniocervical junction syndrome: association with clinical signs and syringomyelia in mature cavalier King Charles spaniels

Background

Dorsal compressive lesions at the atlantoaxial junction (ie, AA bands) occur in dogs with Chiari‐like malformations (CMs), but their clinical relevance is unclear.

Objective

Investigate the influence of AA bands on clinical status and syringomyelia (SM) in mature cavalier King Charles spaniels (CKCS).

Animals

Thirty‐six CKCS, 5–12 years of age, including 20 dogs with neuropathic pain.

Methods

Dogs were examined and assigned a neurologic grade. Magnetic resonance imaging (MRI) of the craniocervical junction was performed with the craniocervical junction extended and flexed (ie, normal standing position). Imaging studies were assessed for the presence of an AA band, CM, SM or some combination of these findings. Band and SM severity were quantified using an objective compression index and ordinal grading scale, respectively.

Results

Of 36 CKCS imaged, 34 had CM. Atlantoaxial bands were present in 31 dogs and were more prominent in extended than flexed positions. Syringomyelia was found in 26 dogs, 23 of which also had AA bands. Bands were associated with both the presence (P = .0031) and severity (P = .008) of clinical signs and SM (P = .0147, P = .0311, respectively). Higher compression indices were associated with more severe SM (P = .0137).

Conclusions

Prevalence of AA bands in older CKCS is high. Positioning of dogs in extension during MRI enhances the sensitivity of the study for detecting this important abnormality. There were significant associations among AA bands, clinical signs, and SM in dogs with CM; additional work is needed to understand whether or not this relationship is causal.

Direct-trauma model of posttraumatic syringomyelia with a computer-controlled motorized spinal cord impactor

OBJECTIVE The pathogenesis of posttraumatic syringomyelia remains enigmatic and is not adequately explained by current theories. Experimental investigations require a reproducible animal model that replicates the human condition. Current animal models are imperfect because of their low reliability, severe neurological deficits, or dissimilar mechanism of injury. The objective of this study was to develop a reproducible rodent model of posttraumatic syringomyelia using a spinal cord impactor that produces an injury that more closely mimics the human condition and does not produce severe neurological deficits. METHODS The study consisted of 2 parts. Seventy animals were studied overall: 20 in Experiment 1 and 48 in Experiment 2 after two rats with severe deficits were killed early. Experiment 1 aimed to determine the optimal force setting for inducing a cystic cavity without neurological deficits using a computer-controlled motorized spinal cord impactor. Twenty animals received an impact that ranged from 50 to 150 kDyn. Using the optimal force for producing an initial cyst determined from Experiment 1, Experiment 2 aimed to compare the progression of cavities in animals with and those without arachnoiditis induced by kaolin. Forty-eight animals were killed at 1, 3, 6, or 12 weeks after syrinx induction. Measurements of cavity size and maximum anteroposterior and lateral diameters were evaluated using light microscopy. RESULTS In Experiment 1, cavities were present in 95% of the animals. The duration of limb weakness and spinal cord cavity size correlated with the delivered force. The optimal force chosen for Experiment 2 was 75 kDyn. In Experiment 2, cavities occurred in 92% of the animals. Animals in the kaolin groups developed larger cavities and more vacuolations and enlarged perivascular spaces than those in the nonkaolin groups. CONCLUSIONS This impact model reliably produces cavities that resemble human posttraumatic syringomyelia and is suitable for further study of posttraumatic syringomyelia pathophysiology.

Tapering of the cervical spinal canal in patients with distended or nondistended syringes secondary to Chiari type I malformation

BACKGROUND AND PURPOSE

Steeper tapering of the cervical spinal canal as documented in recent studies is thought to have a role in the pathophysiology of Chiari malformation-associated syringomyelia. This study aimed to determine whether taper ratio of the cervical spinal canal differs between patients with distended and nondistended syringes.

MATERIALS AND METHODS

Seventy-seven adolescents (10-18 years) were divided into 2 groups: 44 with distended syrinx and 33 with nondistended syrinx. On T2-weighted MR images, anteroposterior diameter of the spinal canal was measured at each cervical level, and a linear trend line was fit by least squares regression to calculate the taper ratio. Taper ratios were compared between the 2 groups and further evaluated with respect to age and sex.

RESULTS

In the nondistended group ND, the taper ratios for C1-C7, C1-C4, and C4-C7 averaged -0.73 ± 0.57, -1.61 ± 0.98, and -0.04 ± 0.54, respectively, all of which were significantly steeper than those observed in the distended group (P = .001, .004, and .033, respectively). Regarding the average diameters plotted by cervical level, the narrowest region of the canal was found to occur at C4 in both groups. In addition, no significant differences in taper ratio were noted between males and females, or between older (>14 years) and younger patients (≤14 years).

CONCLUSIONS

Taper ratios of the cervical spinal canal were found to be different between patients with distended and nondistended syringes, indicating a reciprocal interaction between the syrinx and the cervical spine anatomy.

Post-traumatic syringomyelia: CSF hydrodynamic changes following spinal cord injury are the driving force in the development of PTSM

Post-traumatic syringomyelia (PTSM) is a disorder that occurs infrequently following spinal cord injury (SCI), characterized by progressive neurological deterioration resulting from syrinx expansion originating in proximity to the traumatic epicenter. Several pathogenetic factors are associated with this disorder, however, the precise mechanism of the development of PTSM is controversial. Combined anatomical alterations and molecular changes following trauma to the spinal cord and arachnoid participate in the development of this condition. These factors include narrowing or obstruction of the subarachnoid space (SAS), central canal occlusion, myelomalacia, and alterations in intramedullary water permeability. If a patient sustains a SCI with delayed progressive deterioration in neurological function, in association with the MRI appearance of syringomyelia (SM), the diagnosis of PTSM is straightforward. The treatment of PTSM has not undergone any significant changes recently. The surgical treatment of PTSM consists of reconstructing the SAS or shunting fluid away from the syrinx to other locations. The advantages and disadvantages of each procedure will be discussed. With greater understanding of the mechanisms contributing to the development of SM, including advanced diagnostic methods and further advances in the development of artificial dural and shunting tubing, future therapies of PTSM will be more effective and long-lasting. Incorporation of alterations of AQP4 expression provides an intriguing possibility for future treatment of PTSM.

Syringomyelia associated with cervical spondylosis: A rare condition

Spinal spondylosis is an extremely common condition that has only rarely been described as a cause of syringomyelia. We describe a case of syringomyelia associated with cervical spondylosis admitted at our division and treated by our institute. It is the case of a 66-year-old woman. At our observation she was affected by moderate-severe spastic tetraparesis. T2-weighted magnetic resonance imaging (MRI) showed an hyperintense signal within spinal cord from C3 to T1 with a more sharply defined process in the inferior cervical spinal cord. At the same level bulging discs, facets and ligamenta flava hypertrophy determined a compression towards subarachnoid space and spinal cord. Spinal cord compression was more evident in hyperextension rather than flexion. A 4-level laminectomy and subsequent posterior stabilization with intra-articular screws was executed. At 3-mo follow up there was a regression of tetraparesis but motor deficits of the lower limbs residuated. At the same follow up postoperative MRI was executed. It suggested enlargement of the syrinx. Perhaps hyperintensity within spinal cord appeared “bounded” from C3 to C7 with clearer margins. At the level of surgical decompression, subarachnoid space and spinal cord enlargement were also evident. A review of the literature was executed using PubMed database. The objective of the research was to find an etiopathological theory able to relate syringomyelia with cervical spondylosis. Only 6 articles have been found. At the origin of syringomyelia the mechanisms of compression and instability are proposed. Perhaps other studies assert the importance of subarachnoid space regard cerebrospinal fluid (CSF) dynamic. We postulate that cervical spine instability may be the cause of multiple microtrauma towards spinal cord and consequently may damage spinal cord parenchyma generating myelomalacia and consequently syrinx. Otherwise the hemorrhage within spinal cord central canal can cause an obstruction of CSF outflow, finally generating the syrinx. On the other hand in cervical spondylosis the stenotic elements can affect subarachnoid space. These elements rubbing towards spinal cord during movements of the neck can generate arachnoiditis, subarachnoid hemorrhages and arachnoid adhesions. Analyzing the literature these “complications” of cervical spondylosis are described at the origin of syringomyelia. So surgical decompression, enlarging medullary canal prevents rubbings and contacts between the bone-ligament structures of the spine towards spinal cord and subarachnoid space therefore syringomyelia. Perhaps stabilization is also necessary to prevent instability of the cervical spine at the base of central cord syndrome or syringomyelia. Finally although patients affected by central cord syndrome are usually managed conservatively we advocate, also for them, surgical treatment in cases affected by advanced state of the symptoms and MRI.

Beneficial effect of the traditional chinese drug shu-xue-tong on recovery of spinal cord injury in the rat

Shu-Xue-Tong (SXT) is a traditional Chinese drug widely used to ameliorate stagnation of blood flow, such as brain or myocardial infarction. Whether SXT may have therapeutic value for spinal cord injury (SCI), during which ischemia plays an important role in its pathology, remains to be elucidated. We hypothesized that SXT may promote SCI healing by improving spinal cord blood flow (SCBF), and a study was thus designed to explore this possibility. Twenty-five male Sprague-Dawley rats were used. SCI was induced by compression, and SXT was administrated 24 h postinjury for 14 successive days. The effects of SXT were assessed by means of laser-Doppler flowmetry, motor functional analysis (open-field walking and footprint analysis), and histological analysis (hematoxylin-eosin and thionin staining and NeuN immunohistochemistry). SXT significantly promoted SCBF of the contused spinal cord and enhanced the recovery of motor function. Histological analysis indicated that the lesion size was reduced, the pathological changes were ameliorated, and more neurons were preserved. Based on these results we conclude that SXT can effectively improve SCI.

Aquaporins in spinal cord injury: the janus face of aquaporin 4

Although malfunction of spinal cord water channels (aquaporins, AQP) likely contributes to severe disturbances in ion/water homeostasis after spinal cord injury (SCI), their roles are still poorly understood. Here we report and discuss the potential significance of changes in the AQP4 expression in human SCI that generates glial fibrillary acidic protein (GFAP)-labeled astrocytes devoid of AQP4, and GFAP-labeled astroglia that overexpress AQP4. We used a rat model of contusion SCI to study observed changes in human SCI. AQP4-negative astrocytes are likely generated during the process of SCI-induced replacement of lost astrocytes, but their origin and role in SCI remains to be investigated. We found that AQP4-overexpression is likely triggered by hypoxia. Our transcriptional profiling of injured rat cords suggests that elevated AQP4-mediated water influx accompanies increased uptake of chloride and potassium ions which represents a protective astrocytic reaction to hypoxia. However, unbalanced water intake also results in astrocytic swelling that can contribute to motor impairment, but likely only in milder injuries. In severe rat SCI, a low abundance of AQP4-overexpressing astrocytes was found during the motor recovery phase. Our results suggest that severe rat contusion SCI is a better model to analyze AQP4 functions after SCI. We found that AQP4 increases in the chronic post-injury phase are associated with the development of pain-like behavior in SCI rats, while possible mechanisms underlying pain development may involve astrocytic swelling-induced glutamate release. In contrast, the formation and size of fluid-filled cavities occurring later after SCI does not appear to be affected by the extent of increased AQP4 levels. Therefore, the effect of therapeutic interventions targeting AQP4 will depend not only on the time interval after SCI or animal models, but also on the balance between protective role of increased AQP4 in hypoxia and deleterious effects of ongoing astrocytic swelling.

Role of the blood-spinal cord barrier in posttraumatic syringomyelia

OBJECT

Posttraumatic syringomyelia produces a significant burden of pain and neurological deficits in patients with spinal cord injury. The mechanism of syrinx formation is unknown and treatment is often ineffective. A possible explanation for syrinx formation is fluid leakage from the microcirculation in the presence of a compromised blood-spinal cord barrier (BSCB). The aim of this study was to investigate the structural and functional integrity of the BSCB in a model of posttraumatic syringomyelia.

METHODS

The excitotoxic amino acid and arachnoiditis model of syringomyelia was used in 27 Sprague-Dawley rats. Structural integrity of the BSCB was assessed using immunoreactivity to endothelial barrier antigen (EBA), and loss of functional integrity was assessed by extravasation of intravascular horseradish peroxidase. Animals were studied after 3 days, or at 1, 3, 6, or 12 weeks after surgery. There were laminectomy-only and saline injection control animals for comparison at each time point.

RESULTS

Syrinxes formed in 16 of the 17 animals injected with excitotoxic amino acid. Loss of structural and functional integrity of the BSCB in syrinx animals was noted at all time points. Disruption of the BSCB was most dramatic in tissue adjacent to the syrinx, and in the central and dorsal gray matter. Changes in EBA expression generally corresponded with altered vascular permeability, although in the acute stages, widespread vascular permeability occurred without a corresponding decrease in EBA expression. At the later time points (3-12 weeks) EBA expression was often absent, although no vascular leakage was observed.

CONCLUSIONS

This study demonstrated a prolonged structural and functional disruption of the BSCB in this model of posttraumatic syringomyelia. Loss of functional integrity of the BSCB, with fluid entering the interstitial space of the spinal cord, may contribute to initial cyst formation after spinal cord injury and subsequent enlargement of the cyst, to produce posttraumatic syringomyelia.

Cortical Changes Following Spinal Cord Injury with Emphasis on the Nogo Signaling System

After spinal cord injury, structural as well as functional modifications occur in the adult CNS. Sites of plastic changes include the injured spinal cord itself as well as cortical and subcortical structures. Previously, cortical reorganization in response to sensory deprivation has mainly been studied using peripheral nerve injury models, and has led to a degree of understanding of mechanisms underlying reorganization and plastic changes. Deprivation or damage-induced CNS plasticity is not always beneficial for patients, and may underlie the development of conditions such as neuropathic pain and phantom sensations. Therefore, efforts not only to enhance, but also to control the capacity of plastic changes in the CNS, are of clinical relevance. Novel methods to stimulate plasticity as well as to monitor it, such as transcranial magnetic stimulation and functional magnetic resonance imaging, respectively, may be useful in diverse clinical situations such as spinal cord injury and stroke. Here, human and animal studies of spinal cord injury are reviewed, with special emphasis on the contribution of the Nogo signaling system to cortical plasticity.

Mechanistic insights into posttraumatic syringomyelia based on a novel in vivo animal model. Laboratory investigation

OBJECT

Although posttraumatic syringomyelia (PTS) develops in up to 30% of patients after spinal cord injury (SCI), the pathophysiology of this debilitating complication is incompletely understood. To provide greater insight into the mechanisms of this degenerative sequela of SCI, the authors developed and characterized a novel model of PTS.

METHODS

The spinal cords of 64 female Wistar rats were injured by 35-g modified aneurysm clip compression at the level of T6-7. Kaolin (5 microl of 500 mg/ml solution) was then injected into the subarachnoid space rostral to the site of the injury to induce inflammatory arachnoiditis in 22 rats. Control groups received SCI alone (in 21 rats), kaolin injection alone (in 15 rats), or laminectomy and durotomy alone without injury (sham surgery in 6 rats).

RESULTS

The combination of SCI and subarachnoid kaolin injection resulted in a significantly greater syrinx formation and perilesional myelomalacia than SCI alone; SCI and kaolin injection significantly attenuated locomotor recovery and exacerbated neuropathic pain (mechanical allodynia) compared with SCI alone. We observed that combined SCI and kaolin injection significantly increased the number of terminal deoxytransferase-mediated deoxyuridine triphosphate nick-end labeled-positive cells at 7 days after injury (p<0.05 compared with SCI alone) and resulted in a significantly greater extent of astrogliosis and macrophage/microglial-associated inflammation at the lesion (p<0.05).

CONCLUSIONS

The combination of compressive/contusive SCI with induced arachnoiditis results in severe PTS and perilesional myelomalacia, which is associated with enhanced inflammation, astrogliosis, and apoptotic cell death. The development of delayed neurobehavioral deficits and neuropathic pain in this model accurately reflects the key pathological and clinical conditions of PTS in humans.

Neuronal and vascular biomarkers in syringomyelia: investigations using longitudinal MRI

Aims: Syringomyelia is a formation of fluid-filled cavities in the spinal cord, caused by a number of situations including trauma. To understand the origin and progression of syringomyelia, animal models were developed to mimick the condition and computer models were implemented for performing numerical analysis. This article characterizes the neuropathological stages of a contused spinal cord before and after the syringomyelia formation using longitudinal in vivo MRI. Materials & methods: Rat was subject to a contusion-type spinal cord injury (SCI) at the T12 level. MRI data were gathered on post-injury days 3, 14, 28, 72, 94 and 404 using a 9.4 T scanner. In addition, neurobehavioral tests were performed prior to the scans on these days. Results: Pathological consequences of SCI included significant edema and, to a lesser degree, hemorrhage in the acute phase, followed by neuronal loss, tissue alterations and vascular changes in the late stages. The images from the post-injury day 14 indicated shrinkage of the injured tissue and occlusion of the central canal. Subsequently, syringomyelia was initiated cranial to the occlusion and the fluid-filled cavities enlarged with time. The neurologic deficits of the injured rat also worsened over time. Conclusion: The inflammatory, but not the hemostatic, component seems to be a prerequisite for syringomyelia proceeding contusive SCI and abnormal flow of the cerebrospinal fluid (CSF) is likely the main factor. Bioimaging markers from high-resolution MRI sensitized to inflammation and CSF flow may be used for early detection of syringomyelia and assessing its prognosis.

Complete Spinal Cord Transection Treatedby Implantation of a Reinforced Synthetic Hydrogel Channel Results in Syringomyelia and Caudal Migration of the Rostral Stump

OBJECTIVE

Previously, we reported that synthetic poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (PHEMA-MMA) channels promoted regeneration of a small number of axons from brainstem motor nuclei yet provided limited functional recovery after complete spinal cord transection at T8 in rats. However, we found that these modulus channels partially collapsed over time. Therefore, we synthesized coil-reinforced PHEMA or PHEMA-MMA channels with greater elastic moduli and introduced a new spinal fixation technique to prevent collapse. We also assessed axonal regeneration within the new channels containing a cocktail of autologous peripheral nerve grafts, fibrin matrix, and acidic fibroblast growth factor.

METHODS

After spinal cord transection, rats were divided into six groups: Groups 1 and 2 had either a PHEMA or PHEMA-MMA reinforced channel implanted between the stumps of the transected spinal cord with the cocktail; Groups 3 and 4 had either an unfilled reinforced PHEMA or PHEMA-MMA channel similarly implanted; Group 5 had an spinal cord transection without channel implanted, and Group 6 underwent the identical procedure to Group 1, but rats were sacrificed by 8 weeks for early histological assessment. Groups 1 to 5 were sacrificed at 18 weeks.

RESULTS

There was no channel collapse at any time. However, there was no improvement in axonal regeneration or functional recovery among Groups 1 to 4 because of the unexpected development of syringomyelia and caudal migration of the rostral stump. Functional recovery was better in Groups 1 to 4 compared with Group 5 (P < 0.05).

CONCLUSION

The use of channels to enhance regeneration of axons is promising; however, improvement of the design of the channels is required.

The post-syrinx syndrome: stable central myelopathy and collapsed or absent syrinx

Among 168 cases with neurologic findings of cervicothoracic syringomyelia and MRI findings of Chiari 1 malformation and/or underdevelopment of the posterior cranial fossa, 15 patients (9.1 %) had collapsed, flat syrinxes and 14 patients (8.3 %) did not have syrinxes. Both groups of patients had clinical findings of central myelopathy that had been stable for at least 3 years. Magnetic resonance imaging detected atrophy of the cervical spinal cord in both groups and spontaneous communications between the syrinx and the subarachnoid space in 3 patients of the group with collapsed syrinxes. Analysis of these results and review of the literature suggest that patients with clinical signs of syringomyelia and Chiari 1 malformation or underdeveloped posterior fossa, but with small or absent syringomyelitic cavities, have the "postsyrinx" state as a result of spontaneous collapse of distended syrinxes.

Unraveling the riddle of syringomyelia

The pathophysiology of syringomyelia development is not fully understood. Current prevailing theories suggest that increased pulse pressure in the subarachnoid space forces cerebrospinal fluid (CSF) through the spinal cord into the syrinx. It is generally accepted that the syrinx consists of CSF. The here-proposed intramedullary pulse pressure theory instead suggests that syringomyelia is caused by increased pulse pressure in the spinal cord and that the syrinx consists of extracellular fluid. A new principle is introduced implying that the distending force in the production of syringomyelia is a relative increase in pulse pressure in the spinal cord compared to that in the nearby subarachnoid space. The formation of a syrinx then occurs by the accumulation of extracellular fluid in the distended cord. A previously unrecognized mechanism for syrinx formation, the Bernoulli theorem, is also described. The Bernoulli theorem or the Venturi effect states that the regional increase in fluid velocity in a narrowed flow channel decreases fluid pressure. In Chiari I malformations, the systolic CSF pulse pressure and downward motion of the cerebellar tonsils are significantly increased. This leads to increased spinal CSF velocities and, as a consequence of the Bernoulli theorem, decreased fluid pressure in narrow regions of the spinal CSF pathways. The resulting relatively low CSF pressure in the narrowed CSF pathway causes a suction effect on the spinal cord that distends the cord during each systole. Syringomyelia develops by the accumulation of extracellular fluid in the distended cord. In posttraumatic syringomyelia, the downwards directed systolic CSF pulse pressure is transmitted and reflected into the spinal cord below and above the traumatic subarachnoid blockage, respectively. The ensuing increase in intramedullary pulse pressure distends the spinal cord and causes syringomyelia on both sides of the blockage. The here-proposed concept has the potential to unravel the riddle of syringomyelia and affords explanations to previously unanswered clinical and theoretical problems with syringomyelia. It also explains why syringomyelia associated with Chiari I malformations may develop in any part of the spinal cord including the medullary conus. Syringomyelia thus preferentially develops where the systolic CSF flow causes a suction effect on the spinal cord, i.e., at or immediately caudal to physiological or pathological encroachments of the spinal subarachnoid space.

Clinical features and pathomechanisms of syringomyelia associated with spinal arachnoiditis

BACKGROUND

Syringomyelia is a common intramedullary lesion associated with spinal arachnoiditis and obstruction of the foramen magnum such as in Chiari's malformation. Disturbance of cerebrospinal fluid flow around the spinal cord has an important role in the development of syringomyelia due to spinal arachnoiditis; however, the exact mechanisms have not been clarified. The purpose of this retrospective study is to understand the clinical features and pathomechanisms of syringomyelia secondary to spinal arachnoiditis and to provide the current choice of surgical treatment in this difficult clinical entity.

METHODS

Clinical and radiological findings in 15 patients with syringomyelia associated with spinal arachnoiditis who underwent surgical treatment in our institutes between 1982 and 2000 were reviewed. All patients presented with paraparesis or tetraparesis on admission.

RESULTS

Magnetic resonance imaging (MRI) or computed tomography-myelography revealed that the syrinx predominantly existed at the thoracic levels. Five patients showed complete block of the thoracic subarachnoid space by conventional myelography. T2-weighted MRI showed diffuse intramedullary hyperintensity at the level of arachnoiditis. As the first surgical treatment, 10 patients underwent syringo-peritoneal shunt placement. Three patients were treated with a syringo-subarachnoid shunt, and 2 patients were treated with a ventriculoperitoneal shunt. Eight patients required further shunting operations for syringomyelia 2 months to 12 years after the first surgery. Neurologic improvement was obtained in 9 patients (60%) with decreased size of the syrinx. One patient remained stable; 5 patients showed gradual deterioration.

CONCLUSIONS

The syrinx originated from the thoracic levels where severe adhesion of the subarachnoid space was present. The mechanisms of syrinx formation may be based on the increased interstitial fluid in the spinal cord. Shunting procedures were effective in some population of the patients. Decompression procedures of the spinal subarachnoid space may be an alternative primary surgical treatment except for patients with longitudinally extensive arachnoiditis.

Acute brainstem dissection of syringomyelia associated with cervical intramedullary neurinoma

Intramedullary tumors and syringomyelia typically present with slowly progressing deficits. More rarely, they are characterized by acute presentation or worsening, at times mimicking other more common etiologies. The acute onset of syringomyelia is most likely attributable to an acute increase in cerebrospinal fluid and epidural venous pressure that results in impulsive fluid movement and, ultimately, in the rupture of the syrinx and dissection into the spinal cord or brainstem. Reported here is a case of acute presentation of a small cervical intramedullary neurinoma due to the upward dissection of its associated syrinx. Critical questions are: (1) how can a small tumor produce a large syrinx? and (2) in the absence of craniospinal interferences, which mechanism underlies the acute expansion of the cavity, resulting in a rapid onset? The authors examined the pathophysiology of syrinx formation and enlargement in intramedullary tumors and reviewed the literature, emphasizing the relationship between spinal cord movements and intramedullary pressure. On the basis of current pathogenetic concepts, the authors concluded that tumor-related syringomyelia might be caused by an association of mechanisms, both from within (obstruction of perivascular spaces; increase in extracellular fluid viscosity due to the tumor itself; intramedullary pressure gradients among different cord levels and between the cord and the subarachnoid space) and from without (the cerebrospinal fluid entering the tissue). All these factors may be amplified, as in the reported case, by a tumor located dorsally at the cervical level. Abnormal postures of the spine, such as a prolonged and excessive flexed neck position, may ultimately contribute to the acute dissection of the syrinx.

Partial recovery after treatment of chronic paraplegia in rat

While acute spinal cord injury has been the object of intensive research, chronic spinal cord injury has received less attention although most clinical cases of spinal cord injury become chronic. We attempted to surgically "repair" chronic and acute spinal cord injury in a complete transection rat model using a multiple peripheral nerve grafting protocol. The lesion extent was assessed by magnetic resonance imaging (MRI) before the repair procedure. Rats were treated immediately after injury or at 2, 4, or 8 months postinjury. Standard behavioral methods were used to evaluate functional recovery. Two novel tests, the Bipedal Test and the Head-scratch test, were also employed to evaluate hindpaw positioning, interlimb coordination, and stepping rhythmicity, and to indicate rostrocaudal pathway regeneration. MRI helped guide the treatment procedure that was applied to animals with chronic injury. Treated animals demonstrated significant motor recovery. Axonal regeneration resultant to treatment was demonstrated histologically. The results suggest that not only acute but also chronic total paraplegia can be reversed to a moderate degree in rats with regard to hindlimb motor function.

Vascular endothelial growth factor improves functional outcome and decreases secondary degeneration in experimental spinal cord contusion injury

Spinal cord injury leads to acute local ischemia, which may contribute to secondary degeneration. Hypoxia stimulates angiogenesis through a cascade of events, involving angiogenesis stimulatory substances, such as vascular endothelial growth factor (VEGF). To test the importance of angiogenesis for functional outcome and wound healing in spinal cord injury VEGF165 (proangiogenic), Ringer's (control) or angiostatin (antiangiogenic) were delivered locally immediately after a contusion injury produced using the NYU impactor and a 25 mm weight-drop. Rats treated with VEGF showed significantly improved behavior up to 6 weeks after injury compared with control animals, while angiostatin treatment lead to no statistically significant changes in behavior outcome. Furthermore, VEGF-treated animals had an increased amount of spared tissue in the lesion center and a higher blood vessel density in parts of the wound area compared with controls. These effects were unlikely to be due to increased cell proliferation as determined by bromo-deoxy-uridine-labeling. Moreover, VEGF treatment led to decreased levels of apoptosis, as revealed by TUNEL assays. In situ hybridization demonstrated presence of mRNA for VEGF receptors Flt-1, fetal liver kinase-1, neuropilin-1 and -2 in several important cellular compartments of the spinal cord. The different experiments indicate that beneficial effects seen by acute VEGF delivery was attributable to protection/repair of blood vessels, decreased apoptosis and possibly also by other additional effects on glial cells or certain neuron populations.

Spontaneous resolution of syringomyelia: report of two cases and review of the literature

OBJECTIVE AND IMPORTANCE

The natural history of syringomyelia is highly unpredictable, and some patients experience improvement or stabilization without surgery. However, the mechanisms of the formation and spontaneous resolution of syringomyelia remain controversial. This report concerns two patients with syringomyelia who demonstrated spontaneous reductions in syrinx size, accompanied by symptomatic improvement.

CLINICAL PRESENTATION

One patient was a 10-year-old girl with syringomyelia associated with a tight cisterna magna and basilar impression, who demonstrated a spontaneous decrease in syrinx size, accompanied by symptomatic improvement, in 22 months. The other patient was a 39-year-old man with syringomyelia associated with a Chiari I malformation, who demonstrated a spontaneous reduction in syrinx size and neurological improvement, accompanied by elevation of the cerebellar tonsils, 6 months after diagnosis.

INTERVENTION

The patients were monitored.

CONCLUSION

The mechanisms of spontaneous resolution of syringomyelia, as well as the factors leading to the cerebrospinal fluid flow disturbances that cause syringomyelia, may vary. Resolution of foramen magnum lesion-related syringomyelia may be the result of spontaneous correction of the abnormal cerebrospinal fluid flow, as observed in our cases, or of cavity fluid drainage into the spinal arachnoid space because of spinal cord fissuring.

Spinal cord edema: unusual magnetic resonance imaging findings in cervical spondylosis

OBJECT

Spinal cord edema is a rare radiological finding in chronic degenerative disorders of the spine. Between 1997 and 2001, the authors treated six patients with cervical spondylotic myelopathy in whom postoperative spinal cord edema was demonstrated. The authors describe the radiological and clinical features of this unusual condition.

METHODS

The six patients were all men, and ranged in age from 44 to 72 years. All patients presented with mild quadriparesis and underwent laminoplasty or anterior fusion. Preoperative magnetic resonance (MR) imaging revealed marked spinal cord compression with intramedullary hyperintensity on T2-weighted sequences and spinal cord enhancement at the compression level after administration of Gd. After surgery, spinal cord edema was observed in all patients; the spinal cord appeared swollen on the postoperative MR images. Preoperative and postoperative Gd-enhanced MR imaging demonstrated clear enhancement of the white matter at the compressed segment Neurologically, five of six patients experienced good improvement of symptoms; however, the spinal cord edema as documented on follow-up MR imaging persisted for several months after surgery.

CONCLUSIONS

The radiological characterization of spinal cord edema was based on the reversible white matter lesion most likely caused by disturbed local venous circulation induced by chronic spinal cord compression. Such unusual MR findings in cervical spondylotic myelopathy should be differentiated from intramedullary spinal cord tumors, demyelinating disorders, or inflammatory processes.

Nogo-receptor gene activity: cellular localization and developmental regulation of mRNA in mice and humans

Nogo (reticulon-4) is a myelin-associated protein that is expressed in three different splice variants, Nogo-A, Nogo-B, and Nogo-C. Nogo-A inhibits neurite regeneration in the central nervous system. Messenger RNA encoding Nogo is expressed in oligodendrocytes and central and peripheral neurons, but not in astrocytes or Schwann cells. Nogo is a transmembraneous protein; the extracellular domain is termed Nogo-66, and a Nogo-66-receptor (Nogo-R) has been identified. We performed in situ hybridization in human and mouse nervous tissues to map the cellular distribution of Nogo-R gene activity patterns in fetal and adult human spinal cord and sensory ganglia, adult human brain, and the nervous systems of developing and adult mice. In the human fetus Nogo-R was transcribed in the ventral horn of the spinal cord and in dorsal root ganglia. In adult human tissues Nogo-R gene activity was found in neocortex, hippocampus, amygdala, and a subset of large and medium-sized neurons of the dorsal root ganglia. Nogo-R mRNA was not expressed in the adult human spinal cord at detectable levels. In the fetal mouse, Nogo-R was diffusely expressed in brain, brainstem, trigeminal ganglion, spinal cord, and dorsal root ganglia at all stages. In the adult mouse strong Nogo-R mRNA expression was found in neurons in neocortex, hippocampus, amygdala, habenula, thalamic nuclei, brainstem, the granular cell layer of cerebellum, and the mitral cell layer of the olfactory bulb. Neurons in the adult mouse striatum, the medial septal nucleus, and spinal cord did not express Nogo-R mRNA at detectable levels. In summary, Nogo-66-R mRNA expression in humans and mice was observed in neurons of the developing nervous system Expression was downregulated in the adult spinal cord of both species, and specific expression patterns were seen in the adult brain.

Solid human embryonic spinal cord xenografts in acute and chronic spinal cord cavities: a morphological and functional study

While therapeutic spinal cord grafting procedures are of interest in the chronic spinal cord injury stage, previous experimental grafting studies, including human spinal cord tissue, have mainly focused on the acute stage. Therefore, solid human embryonic spinal cord grafts were implanted in acute or chronic spinal cord aspiration cavities of immunodeficient rats to compare the morphological and locomotor outcome to that of lesion alone cases. Locomotor function was assessed using the Basso, Beattie, and Bresnahan open-field locomotor rating scale up to 6 months, while the morphological evaluation of graft survival, growth, and integration was performed at 6 weeks or 6 months after implantation. Graft survival was 94% in both lesion models, while graft growth was enhanced in the chronic compared to the acute cavity group. Human specific Thy-1 and neurofilament immunoreactive fibers were observed up to 7 mm into host white matter, while aminergic fibers were observed up to 1 mm into the grafts. Abundant calcitonin gene-related peptide immunoreactive fibers in the grafts in the absence both of immunoreactive cell bodies and colocalized human-specific neurofilament immunoreactivity, suggested host fiber ingrowth. At 6 months, the grafted cases presented less central canal deformation and lower glial fibrillary acidic protein immunoreactivity at the host cavity border compared to that of the nongrafted cases. The strong compensatory regain of locomotor function after unilateral spinal cord lesions was not affected by the human spinal cord grafts. In conclusion, solid human embryonic spinal cord tissue transplanted to a cavity in the adult injured spinal cord results in beneficial morphological effects in both the acute and chronic spinal cord lesion.

NOGO mRNA expression in adult and fetal human and rat nervous tissue and in weight drop injury

Nogo is a myelin-associated protein known to inhibit growth of neurites. In order to understand possible physiological roles of Nogo, we performed in situ hybridization using rat and human probes complementary to a Nogo-A-specific sequence and a sequence shared by all known Nogo transcripts recognizing nogo-A, -B, and -C. We studied the cellular distribution of nogo-mRNA in fetal and adult human and rat tissues, with a focus on the spinal cord and ganglia. Rat mRNA expression was also studied in a spinal cord weight-drop model and in animals exposed to kainic acid. In human fetal tissue, nogo-A was strongly expressed in the ventral two-thirds of the spinal cord, the dorsal root ganglia, and autonomic ganglia. Similarly, nogo-A mRNA expression was observed in the adult human spinal cord and ganglia. High levels of nogo-A message were observed in neurons, such as motor neurons and sensory ganglia neurons. The distribution of nogo message in rats resembled that seen in human tissues. Thus, nogo mRNA was expressed in neurons and oligodendrocytes, but not astrocytes or Schwann cells. In addition, expression of nogo-A mRNA was observed in human and rat developing muscle tissue. High level of nogo-mRNA were also expressed in the rat trigeminal ganglion and trigeminal pontine nucleus. In fetal rats the adrenal gland and cell clusters in the liver were positive for the nogo-ABC pan-probe, but negative for the nogo-A probe. While neurons in the adult rat brain were generally positive, very prominent nogo-A mRNA and nogo-ABC mRNA signals were obtained from neurons of the hippocampus, piriform cortex, the red nucleus, and the oculomotor nucleus. Nogo-A mRNA expression was markedly reduced in the epicenter of a lesion in the spinal cord of adult rats 6 and 24 h after a weight-drop injury, while no perifocal upregulation of nogo mRNA was seen. No obvious change of nogo expression was detected in kainic acid exposed animals. In conclusion our in situ hybridization study has demonstrated widespread expression of nogo mRNA in the fetal, developing and adult nervous system of rat and man. In addition to oligodendroglial cells, high levels of nogo-A mRNA expression were found in neurons, raising important questions about the function of neuronal nogo mRNA. No obvious regulation of nogo was detected following injury.