Neurofilament-light in former athletes: a potential biomarker of neurodegeneration and progression.

BACKGROUND/OBJECTIVE: This study aimed to evaluate serum neurofilament light chain (NF-L) levels in former professional contact sports athletes with multiple concussions (ExPro) as a potential biomarker of neurodegeneration and predictor of white-matter (WM) abnormality progression. METHODS: Concentrations of NF-L in the serum of fifty-two cognitively normal ExPro and twenty-one healthy controls (HC) with no history of concussions were measured using single molecule array (Simoa) technology. Both groups underwent neuroimaging at the time of serum collection. Eighteen of the participants in the ExPro underwent follow-up imaging after 2 years. RESULTS: Levels of serum NF-L were not significantly different between the ExPro and HC. However, in the ExPro group, NF-L levels were positively correlated with the mean diffusivity (MD) of corpus callosum (CC) and fornix, and total ventricular volume. Moreover, NF-L levels in the ExPro group at the first visit were positively correlated with the amount of increase in CC MD at the 2-year follow-up. CONCLUSIONS: NF-L levels reflect neuronal changes in the ExPro group and predict the extent of decrease in white matter integrity over time. Serum NF-L might be a biomarker of neurodegeneration and WM abnormality progression in ExPro.

Injectable hydrogel promotes early survival of induced pluripotent stem cell-derived oligodendrocytes and attenuates longterm teratoma formation in a spinal cord injury model.

Transplantation of pluripotent stem cells and their differentiated progeny has the potential to preserve or regenerate functional pathways and improve function after central nervous system injury. However, their utility has been hampered by poor survival and the potential to form tumors. Peptide-modified biomaterials influence cell adhesion, survival and differentiation in vitro, but their effectiveness in vivo remains uncertain. We synthesized a peptide-modified, minimally invasive, injectable hydrogel comprised of hyaluronan and methylcellulose to enhance the survival and differentiation of human induced pluripotent stem cell-derived oligodendrocyte progenitor cells. Cells were transplanted subacutely after a moderate clip compression rat spinal cord injury. The hydrogel, modified with the RGD peptide and platelet-derived growth factor (PDGF-A), promoted early survival and integration of grafted cells. However, prolific teratoma formation was evident when cells were transplanted in media at longer survival times, indicating that either this cell line or the way in which it was cultured is unsuitable for human use. Interestingly, teratoma formation was attenuated when cells were transplanted in the hydrogel, where most cells differentiated to a glial phenotype. Thus, this hydrogel promoted cell survival and integration, and attenuated teratoma formation by promoting cell differentiation.

Frontotemporal correlates of impulsivity and machine learning in retired professional athletes with a history of multiple concussions.

The frontotemporal cortical network is associated with behaviours such as impulsivity and aggression. The health of the uncinate fasciculus (UF) that connects the orbitofrontal cortex (OFC) with the anterior temporal lobe (ATL) may be a crucial determinant of behavioural regulation. Behavioural changes can emerge after repeated concussion and thus we used MRI to examine the UF and connected gray matter as it relates to impulsivity and aggression in retired professional football players who had sustained multiple concussions. Behaviourally, athletes had faster reaction times and an increased error rate on a go/no-go task, and increased aggression and mania compared to controls. MRI revealed that the athletes had (1) cortical thinning of the ATL, (2) negative correlations of OFC thickness with aggression and task errors, indicative of impulsivity, (3) negative correlations of UF axial diffusivity with error rates and aggression, and (4) elevated resting-state functional connectivity between the ATL and OFC. Using machine learning, we found that UF diffusion imaging differentiates athletes from healthy controls with significant classifiers based on UF mean and radial diffusivity showing 79-84 % sensitivity and specificity, and 0.8 areas under the ROC curves. The spatial pattern of classifier weights revealed hot spots at the orbitofrontal and temporal ends of the UF. These data implicate the UF system in the pathological outcomes of repeated concussion as they relate to impulsive behaviour. Furthermore, a support vector machine has potential utility in the general assessment and diagnosis of brain abnormalities following concussion.

Click-crosslinked injectable hyaluronic acid hydrogel is safe and biocompatible in the intrathecal space for ultimate use in regenerative strategies of the injured spinal cord.

Traumatic spinal cord injury (SCI) causes damage and degeneration at and around the lesion site resulting in a loss of function. SCI presents a complex regenerative problem due to the multiple aspects of growth inhibition and the heterogeneity in size, shape and extent of injury. Currently, there is no widely accepted treatment strategy available and delivering biomolecules to the central nervous system remains a challenge. With a view towards achieving local release, we designed a hydrogel that can be injected into the intrathecal space. Here we describe the synthesis and characterization of a click-crosslinked hyaluronic acid hydrogel and demonstrate controlled in vitro release of bioactive brain derived neurotrophic factor. Importantly, we demonstrate that this new hydrogel is both biocompatible in the intrathecal space based on immunohistochemistry of the host tissue response and safe based on behavioral analysis of locomotor function.

Intrathecal transplantation of stem cells by lumbar puncture for thoracic spinal cord injury in the rat.

STUDY DESIGN: Experimental investigation of intrathecal transplantation of stem cells by lumbar puncture (LP) in a rat model that simulates human thoracic spinal cord injury (SCI). OBJECTIVES: To examine the distribution and phenotype of spinal cord-derived neural stem/progenitor cells (NSPCs) and bone marrow-derived mesenchymal stromal cells (BMSCs) following LP transplantation in SCI rats. SETTING: Toronto Western Research Institute, Toronto, Ontario, Canada. METHODS: NSPCs or BMSCs were transplanted via LP at level L3-5 1 week after compression SCI at T8. Rats were killed at 3, 17 and 27 days after LP transplantation and the relative distribution of cells at C4, T8 and L3-5 was quantitated. The phenotype of the NSPC and BMSC was assessed with immunocytochemistry in vitro and following LP transplantation. RESULTS: By 4 weeks, more NSPC migrated to the lesion site relative to BMSC and uninjured animals. However, there was no preferential homing of either of these types of cells into the parenchyma of the injury site, and most of the transplanted cells remained in the intrathecal space. In vitro, spinal cord-derived NSPC proliferated and expressed nestin, but after LP transplantation, NSPC became post-mitotic and primarily expressed oligodendrocyte markers. In contrast, BMSC did not express any neural antigens in vivo. CONCLUSION: LP is a minimally invasive method of cell transplantation that produces wide dissemination of cells in the subarachnoid space of the spinal cord. This is the first study to report and quantify the phenotype and spatial distribution of LP transplanted NSPC and BMSC in the intact and injured spinal cord.

Transplanted adult spinal cord-derived neural stem/progenitor cells promote early functional recovery after rat spinal cord injury.

We examined the effect of spinal cord-derived neural stem/progenitor cells (NSPCs) after delayed transplantation into the injured adult rat spinal cord with or without earlier transplantation of bone marrow-derived mesenchymal stromal cells (BMSCs). Either BMSCs or culture medium were transplanted immediately after clip compression injury (27 g force), and then, 9 days after injury, NSPCs or culture medium were transplanted. Cell survival and differentiation, functional recovery, retrograde axonal tracing, and immunoelectron microscopy were assessed. A significant improvement in functional recovery based on three different measures was seen only in the group receiving NSPCs without BMSCs, and the improved recovery was evident within 1 week of transplantation. In this group, NSPCs differentiated mainly into oligodendrocytes and astrocytes, there was ensheathing of axons at the injury site by transplanted NSPCs, an increase in host oligodendrocytes, and a trend toward an increase in retrogradely labeled supraspinal nuclei. Transplantation of the BMSC scaffold resulted in a trend toward improved survival of the NSPCs, but there was no increase in function. Thus, transplantation of adult rat NSPCs produced significant early functional improvement after spinal cord injury, suggesting an early neuroprotective action associated with oligodendrocyte survival and axonal ensheathment by transplanted NSPCs.

Conservative management of vestibular schwannomas: third review of a 10-year prospective study.

Seventy-two patients with a unilateral vestibular schwannoma have been treated conservatively for a median of 121 months. They have been followed prospectively by serial clinical examination, MRI scans and audiometry. Twenty-five patients (35%, 95% CI: 24-47) failed conservative management and required active intervention during the study. No factors predictive of tumour growth or failure of conservative management could be identified. Seventy-five per cent of failures occurred in the first half of the 10-year study. The median growth rate for all tumours at 10 years was 1 mm/year (range -0.53-7.84). Cerebellopontine angle tumours grew faster (1.4 mm/year) than intracanalicular tumours (0 mm/year, P < 0.01); 92% had growth rates under 2 mm/year. Hearing deteriorated substantially even in tumours that did not grow, but did so faster in tumours that grew significantly (mean deterioration in pure tone average at 0.5, 1, 2 and 3 kHz was 36 dB; speech discrimination scores deteriorated by 40%). Patients who failed conservative management had clinical outcomes that were not different from those who underwent primary treatment without a period of conservative management.

An international review of head and spinal cord injuries in alpine skiing and snowboarding.

BACKGROUND: Alpine skiing and snowboarding are popular winter activities worldwide, enjoyed by participants of all ages and skill levels. There is some evidence that the incidence of traumatic brain injury (TBI) and spinal cord injury (SCI) in these activities may be increasing. These injuries can cause death or severe debilitation, both physically and emotionally, and also result in enormous financial burden to society. Indeed, TBI is the leading cause of death and catastrophic injury in the skiing and snowboarding population. Furthermore, there are severe limitations to therapeutic interventions to restore neurological function after TBI and SCI, and thus the emphasis must be on prevention. OBJECTIVES: (1) To examine the worldwide epidemiology of TBI and SCI in skiing and snowboarding; (2) to describe and examine the effectiveness of prevention strategies to reduce the incidence of TBI and SCI in skiing and snowboarding. SEARCH STRATEGY: Searches were performed on a variety of databases to identify articles relevant to catastrophic central nervous system injury in skiing and snowboarding. The databases included PubMed, Medline, EMBASE, CDSR, ACP Journal Club, DARE, CCTR, SportDiscus, CINAHL, and Advanced Google searches. SELECTION CRITERIA AND DATA COLLECTION: After initial prescreening, articles included in the review required epidemiological data on SCI, TBI, or both. Articles had to be directly associated with the topic of skiing and/or snowboarding and published between January 1990 and December 2004. RESULTS: 24 relevant articles, from 10 different countries, were identified. They indicate that the incidence of TBI and SCI in skiing and snowboarding is increasing. The increases coincide with the development and acceptance of acrobatic and high-speed activities on the mountains. There is evidence that helmets reduce the risk of head injury by 22-60%. Head injuries are the most common cause of death among skiers and snowboarders, and young male snowboarders are especially at risk of death from head injury. CONCLUSIONS: There should be enhanced promotion of injury prevention that includes the use of helmets and emphasizes the skier's and snowboarder's responsibility code.

Bone marrow-derived mesenchymal stromal cells for the repair of central nervous system injury.

Transplantation of bone marrow-derived mesenchymal stromal cells (MSCs) into the injured brain or spinal cord may provide therapeutic benefit. Several models of central nervous system (CNS) injury have been examined, including that of ischemic stroke, traumatic brain injury and traumatic spinal cord injury in rodent, primate and, more recently, human trials. Although it has been suggested that differentiation of MSCs into cells of neural lineage may occur both in vitro and in vivo, this is unlikely to be a major factor in functional recovery after brain or spinal cord injury. Other mechanisms of recovery that may play a role include neuroprotection, creation of a favorable environment for regeneration, expression of growth factors or cytokines, vascular effects or remyelination. These mechanisms are not mutually exclusive, and it is likely that more than one contribute to functional recovery. In light of the uncertainty surrounding the fate and mechanism of action of MSCs transplanted into the CNS, further preclinical studies with appropriate animal models are urgently needed to better inform the design of new clinical trials.

Proliferation, migration, and differentiation of endogenous ependymal region stem/progenitor cells following minimal spinal cord injury in the adult rat.

Ependymal cells of the adult mammalian spinal cord exhibit stem/progenitor cell properties following injury. In the present study, we utilized intraventricular injection of 1,1'-dioctadecyl-6,6'-di(4-sulfophenyl)-3,3,3',3'-tetramethylindocarbocyanine (DiI) to label the ependyma lining the central canal to allow tracking of the migration of endogenous ependymal cells and their progeny after spinal cord injury (SCI). We developed a minimal injury model that preserved the integrity of the central canal and did not interfere with ependymal cell labeling. Three days following SCI, there was an 8.6-fold increase in the proliferative labeling index of the ependymal cells at the level of the needle track based on bromodeoxyuridine labeling, compared with 1 day post-injury. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positive cells were not detected in the ependyma or surrounding gray matter, indicating that ependymal cells do not undergo apoptosis in response to minimal injury. Nestin was rapidly induced in the ependyma by 1 day and expression peaked by 7 days post-injury. We quantitated the number and distance of ependymal cell migration following minimal injury. The number of ependymal cells migrating from the region of the central canal increased by 3 days following minimal injury and DiI-labeled glial fibrillary acidic protein expressing cells were detected 14 days post-SCI, most of which migrated within 70 microm of the region of the central canal. These results show that a minimal SCI adjacent to the ependyma is sufficient to induce an endogenous ependymal cell response where ependymal stem/progenitor cells proliferate and migrate from the region of the central canal, differentiating primarily into astrocytes.

Endogenous and exogenous CNS derived stem/progenitor cell approaches for neurotrauma.

Neural stem/progenitor cells capable of generating new neurons and glia, reside in specific areas of the adult mammalian central nervous system (CNS), including the ependymal region of the spinal cord and the subventricular zone (SVZ), hippocampus, and dentate gyrus of the brain. Much is known about the neurogenic regions in the CNS, and their response to various stimuli including injury, neurotrophins (NFs), morphogens, and environmental factors like learning, stress, and aging. This work has shaped our current views about the CNS's potential to recover lost tissue and function post-traumatically and the therapies to support the intrinsic regenerative capacity of the brain or spinal cord. Recently, intensive research has explored the potential of harvesting, culturing, and transplanting neural stem/progenitors as a therapeutic intervention for spinal cord injury (SCI) and traumatic brain injury (TBI). Another strategy has focused on maximizing the potential of this endogenous population of cells by stimulating their recruitment, proliferation, migration, and differentiation in vivo following traumatic lesions to the CNS. The promise of such experimental treatments has prompted tissue and biomaterial engineers to implant synthetic three-dimensional biodegradable scaffolds seeded with neural stem/progenitors into CNS lesions. Although there is no definitive answer about the ideal cell type for transplantation, strong evidence supports the use of region specific neural stem/progenitors. The technical and logistic considerations for transplanting neural stem/progenitors are extensive and crucial to optimizing and maintaining cell survival both before and after transplantation, as well as for tracking the fate of transplanted cells. These issues have been systematically addressed in many animal models, that has improved our understanding and approach to clinical therapeutic paradigms.

Spinal injuries in Canadian ice hockey: documentation of injuries sustained from 1943-1999.

OBJECTIVES: Study objectives were: (a) to examine the causes and incidence of major spinal cord injuries sustained by ice hockey players; and (b) to add recently reported Canadian cases to the Canadian Ice Hockey Spinal Injury Registry to determine the effectiveness of prevention efforts. METHODS: The study was a review of questionnaires returned retrospectively by physicians and other sources reporting ice hockey related spinal injuries in Canada. Physicians reported on the mechanism of injury, vertebral level of injury, presence of neurologic deficit, type of event, and type of fracture. RESULTS: Between 1943 and 1999, 271 major spinal injuries were reported in Canadian ice hockey players, of which 49.0% occurred to players 16-20 years of age. Ontario has had a disproportionately large number of injuries compared to some provinces, especially Quebec. Of the spinal cord injuries, 65.8% resulted from colliding with the boards, and 36.6% were due to players being pushed or checked from behind. The recent survey shows that there has been a decline in the number of major spinal cord injuries in Canadian ice hockey, especially those causing paralysis due to checking or pushing from behind. CONCLUSIONS: Impact of the head with the boards after being checked or pushed from behind was the most common mechanism of spinal cord injury. Injury prevention programs are becoming effective in reducing the overall number of injuries, especially those due to checking from behind. Greater awareness of the occurrence and mechanisms of injury through educational programs and rules changes by organized hockey have reduced the annual incidence of catastrophic spinal injuries in Canadian ice hockey.

Conservative management of vestibular schwannomas - second review of a prospective longitudinal study.

Vestibular schwannomas have been traditionally managed with microsurgical removal and in recent years, stereotactic radiotherapy. However, there is a group of patients in whom a conservative management approach might represent a desirable alternative. The aim of this study was to determine the natural history and outcome following the conservative management of 72 patients with unilateral vestibular schwannomas. This is a prospective cohort review of a previously published group of patients [Clin. Otolaryngol. (2000) 25, 28-39] with unilateral vestibular schwannoma that were initially analysed at our institution in 1998 [Walsh R.M., Bath A.P., Bance M.L. et al., Clin. Otolaryngol. (2000) 25, 28]. The mean duration of follow-up was 80 months (range 52-242 months). All the patients in the study underwent serial magnetic resonance imaging (MRI) for assessment of tumour growth. Patients were deemed to have failed conservative management if there was evidence of rapid radiological tumour growth and/or increasing signs and symptoms, which necessitated active intervention. The mean tumour growth rate for the entire group at the second review was 1 mm/year (range -0.84-9.65 mm/year). The mean growth rate for cerebellopontine angle tumours (1.3 mm/year) was significantly greater than that of internal auditory canal (IAC) tumours (0 mm/year) (P = 0.005). The majority of tumours (87.14%) grew <2 mm/year. There was significant tumour growth seen in 38.9%, no or insignificant growth in 41.7%, and negative growth in 19.4%. Twenty-three patients (32%) failed conservative management at the second review. There was no difference in the outcome of these failed patients in comparison with patients who underwent primary treatment without a period of conservative management. The mean growth rate of tumours in patients that failed conservative management (3.1 mm/year) was significantly greater than that in patients who did not fail (0.2 mm/year) (P < 0.001). No factors predictive of tumour growth or failure of conservative management were identified. Hearing deterioration with pure tone averages (0.5, 1, 2, 3 kHz) and speech discrimination scores occurred irrespective of tumour growth. This prospective study further emphasizes the role of conservative management in selected cases of vestibular schwannomas. Tumours in this study confined to the IAC typically demonstrated minimal or no growth on serial MRI scanning. Regular follow-up with interval scanning is mandatory in all patients.

Evaluation of the ThinkFirst Canada, Smart Hockey, brain and spinal cord injury prevention video.

OBJECTIVE: The ThinkFirst Canada Smart Hockey program is an educational injury prevention video that teaches the mechanisms, consequences, and prevention of brain and spinal cord injury in ice hockey. This study evaluates knowledge transfer and behavioural outcomes in 11-12 year old hockey players who viewed the video. DESIGN: Randomized controlled design. SETTING: Greater Toronto Minor Hockey League, Toronto Ontario. SUBJECTS: Minor, competitive 11-12 year old male ice hockey players and hockey team coaches. INTERVENTIONS: The Smart Hockey video was shown to experimental teams at mid-season. An interview was conducted with coaches to understand reasons to accept or refuse the injury prevention video. MAIN OUTCOME MEASURES: A test of concussion knowledge was administered before, immediately after, and three months after exposure to the video. The incidence of aggressive penalties was measured before and after viewing the video. RESULTS: The number of causes and mechanisms of concussion named by players increased from 1.13 to 2.47 and from 0.67 to 1.22 respectively. This effect was maintained at three months. There was no significant change in control teams. There was no significant change in total penalties after video exposure; however, specific body checking related penalties were significantly reduced in the experimental group. CONCLUSION: This study showed some improvements in knowledge and behaviours after a single viewing of a video; however, these findings require confirmation with a larger sample to understand the sociobehavioural aspects of sport that determine the effectiveness and acceptance of injury prevention interventions.

National Hockey League reported concussions, 1986-87 to 2001-02.

OBJECTIVES: To examine the longitudinal media reported rate of concussions in the National Hockey League (NHL) over the period 1986-87 to 2001-02. METHODS: All injury reports published in the weekly sports newspaper The Hockey News for the 16 seasons 1986-87 through 2001-02 were reviewed for reported concussions. The Hockey News reports are based on weekly injury reports released by the NHL, which derive from reports submitted to the league by individual team offices. RESULTS: Adjusted for changes in the number of teams and games per season over the 16 year study period, and expressed as: number of concussions per 1000 games, results by season (starting with 1986-87) were 4, 8, 7, 7, 5, 5, 7, 7, 6, 8, 13, 20, 30, 27, 30, 25. Comparing each season with the prior season, significant increases were reported in 1997-98 and 1998-99 (p < 0.05 and 0.025, respectively), with no change since 1998-99. CONCLUSIONS: The reported concussion rate in the NHL during the last five years is more than triple that of the previous decade. Bigger, faster players, new equipment and harder boards and glass have all theoretically increased the risk of concussion in the NHL in recent years. However, the abrupt increase and subsequent plateau in concussion rate since 1997 suggests that increased recognition and reporting may be primarily responsible for the apparent increase in incidence.

Strategies for recovery and regeneration after brain and spinal cord injury.

Current knowledge of the epidemiology and pathophysiology of neurotrauma and the key clinical and experimental strategies for promoting recovery and regeneration after brain and spinal cord trauma are reviewed. Brief overviews of the epidemiology and pathophysiology of neurotrauma are presented, and the key experimental and clinical treatments for the promotion of recovery and regeneration after brain and spinal cord trauma are discussed.

Treatment of severe double spinal cord injuries.

This is a case report describing an injury--sustained by a 25-year-old man during a car accident, and characterized by fracture dislocation of the spine at the level of C7 and T4 accompanied by pulmonary contusion. He had an incomplete spinal cord lesion at the level of C7 and a complete lesion at the level of T4 (T4 ASIA A). Imaging of the spine showed three column fractures with ventral spinal cord compression at both levels. Discussants of this case comment on the concept of acute treatment of severe double spinal cord injuries, and present their chosen way of management in this particular case.

A novel method for simultaneous anterograde and retrograde labeling of spinal cord motor tracts in the same animal.

Examination of repaired spinal cord tracts has usually required separate groups of animals for anterograde and retrograde tracing owing to the incompatibility of techniques such as tissue fixation. However, anterograde and retrograde labeling of different animals subjected to the same repair may not allow accurate examination of that repair strategy because widely variable results can occur in animals subjected to the same strategy. We have developed a reliable method of labeling spinal cord motor tracts bidirectionally in the same animal using DiI, a lipophilic dye, to anterogradely label the corticospinal tract and Fluoro-Gold (FG) to retrogradely label cortical and brainstem neurons of several spinal cord motor tracts in normal and injured adult rats. Other tracer combinations (lipophilic dyes or fluorescent dextrans) were also investigated but were less effective. We also developed methods to minimize autofluorescence with the DiI/FG technique, and found that the DiI/FG technique is compatible with decalcification and immunohistochemistry for several markers relevant for studies of spinal cord regeneration. Thus, the use of anterograde DiI and retrograde FG is a novel technique for bidirectional labeling of the motor tracts of the adult spinal cord with fluorescent tracers and should be useful for demonstrating neurite regeneration in studies of spinal cord repair.(J Histochem Cytochem 49:1111-1122, 2001)