Nigel R. Jones

Early Expression and Cellular Localization of Proinflammatory Cytokines Interleukin-1β, Interleukin-6, and Tumor Necrosis Factor-α in Human Traumatic Spinal Cord Injury

Study Design. Post-traumatic inflammatory response was studied in 11 human cases of acute spinal cord contusion injury. Objectives. To examine the inflammatory cellular response and the immunocytochemical expression and localization of interleukin-1β, internleukin-6, and tumor necrosis factor-&agr;in human spinal cord after contusion injury. Summary of Background Data. The post-traumatic inflammatory response plays an important role in secondary injury mechanisms after spinal cord injury, and inter-leukin-1β, internleukin-6, and tumor necrosis factor-&agr; are key inflammatory mediators. Methods. The study group comprised 11 patients with spinal cord contusion injury and 2 normal individuals. Histologic and immunocytochemical assessments were undertaken to evaluate the inflammatory cellular response and the immunoexpression of interleukin-1β, internleukin-6, and tumor necrosis factor-&agr; in the injured human spinal cord. The cellular sources of interleukin-1β, internleukin-6, and tumor necrosis factor-&agr; were elucidated by immunofluorescence double-labeled confocal imaging. Results. Increased immunoreactivity of interleukin-1β, internleukin-6, and tumor necrosis factor-&agr;was detected in neurons 0.5 hour after injury, and in neurons and microglia 5 hours after injury, but the expression of these proinflammatory cytokines was short-lived and declined sharply to baseline by 2 days after injury. In the inflammatory cellular response, as early as 0.5 hour after spinal cord injury, activated microglia were detected, and axonal swellings and axons were surrounded by microglial processes. Numerous neutrophils appeared in the injured cord 1 day after injury, and then their number declined dramatically, whereas macrophages progressively increased after day 1. Conclusions Endogenous cells (neurons and microglia) in the human spinal cord, not the blood-borne leukocytes, contribute to the early production of interleukin-1β, interleukin-6, and tumor necrosis factor-&agr; in the post-traumatic inflammatory response, and microglia are involved the early response to traumatic axonal injury.

Severity-dependent expression of pro-inflammatory cytokines in traumatic spinal cord injury in the rat.

The post-traumatic inflammatory response in acute spinal cord contusion injury was studied in the rat. Mild and severe spinal cord injury (SCI) was produced by dropping a 10 g weight from 3 and 12 cm at the T12 vertebral level. Increased immunoreactivity of TNF-alpha in mild and severe SCI was detected in neurons at 1 h post-injury, and in neurons and microglia at 6 h post-injury, with a less significant increase in mild SCI. Expression was short-lived and declined sharply by 1 d post-injury. RT-PCR showed an early significant up-regulation of IL-1 beta, IL-6 and TNF-alpha mRNAs, maximal at 6 h post-injury with return to control levels by 24 h post-injury, the changes being less statistically significantly in mild SCI. Western blot showed early transient increases of IL-1 beta, IL-6 and TNF-alpha proteins in severe SCI but not mild SCI. Immunocytochemical, western blotting and RT-PCR analyses suggest that endogenous cells (neurons and microglia) in the spinal cord, not blood-borne leucocytes, contribute to IL-1 beta, IL-6 and TNF-alpha production in the post-traumatic inflammatory response and that their up-regulation is greater in severe than mild SCI.

Upregulation of Amyloid Precursor Protein Messenger RNA in Response to Traumatic Brain Injury: An Ovine Head Impact Model

There is evidence that the amyloid precursor protein (APP) plays an important role in neuronal growth and synaptic plasticity and that its increased expression following traumatic brain injury represents an acute phase response to trauma. We hypothesized that the previously described increased APP expression in response to injury (Van den Heuvel et al., Acta Neurochir. Suppl. 71, 209-211) is due to increased mRNA expression and addressed this by examining the expression of APP mRNA and APP within neuronal cell bodies over time in an ovine head impact model. Twenty-five anesthetized and ventilated 2-year-old Merino ewes sustained a left temporal head impact using a humane stunner and 9 normal sheep were used as nonimpact controls. Following postimpact survival periods of 15, 30, 45, 60, and 120 min, brains were perfusion fixed in 4% paraformaldehyde and examined according to standard neuropathological protocol. APP mRNA and antigen expression were examined in 5-microm sections by nonisotopic in situ hybridization and APP immunocytochemistry. The percentage of brain area with APP immunoreactivity within neuronal cell bodies in the impacted animals increased with time from a mean of 7.5% at 15 min to 54.5% at 2 h. Control brains showed only very small numbers of weakly APP-positive neuronal cell bodies ranging from 2 to 14% (mean 7%). Increased expression of APP mRNA was first evident in impacted hemispheres at 30 min after impact and progressively increased over time to involve neurons in all sampled regions of the brain, suggesting increased transcription of APP. In contrast, APP mRNA was undetectable in tissue from nonimpacted sheep. These data show that APP mRNA and antigen expression are sensitive early indicators of neuronal injury with widespread upregulation occurring as early as 30 min after head impact.

Evidence for rapid fluid flow from the subarachnoid space into the spinal cord central canal in the rat

Horseradish peroxidase (HRP) was used as a CSF tracer in Sprague-Dawley rats. One group of rats received an injection of HRP in the cisterna magna and a second group was injected in the thoracic spinal subarachnoid space. The animals were sacrificed 0, 10 or 30 min after HRP injection by rapid perfusion with paraformaldehyde and glutaraldehyde. In both groups, there was rapid HRP labeling of brain and spinal cord perivascular spaces. HRP was present in the central canal in a pattern that was not consistent with flow from the fourth ventricle: in both groups there were segments of unlabeled central canal between the fourth ventricle and central canal segments containing HRP. HRP-labeled perivascular spaces were seen in the central gray matter adjacent to the central canal. There was a distinctive pattern of interstitial HRP between perivascular spaces and the central canal. The results suggest that there is a normal flow of fluid from the subarachnoid space, into the perivascular spaces, across the interstitial space and into the central canal. The function of this flow may be to clear metabolites from the interstitial space. The existence of such a flow would add considerable support to the theory that non-communicating syringomyelia develops in segments of central canal isolated by occlusion or stenosis at each end.

Impact mechanics and axonal injury in a sheep model.

This paper describes a biomechanical study of axonal injury due to a blunt impact to the head. The aim of the experimental model was to produce axonal injury analogous to that seen in human trauma while measuring the dynamics of the impact and the subsequent kinematics of the head. These measurements were made in a way to facilitate the simulation of these experiments using the finite element method. Sheep were anaesthetised and ventilated, and subjected to a single impact to the lateral aspect of their skull. The impact force was measured throughout the duration of the impact and the kinematics of the head was measured using a novel implementation of a nine-accelerometer array. The axonal injury was identified using amyloid precursor protein (APP) as a marker, intensified using antigen retrieval techniques. Axonal injury was consistently produced in all animals. Commonly injured regions included the sub-cortical and deep white matter, and the periventricular white matter surrounding the lateral ventricles. The observed axonal injury was mapped and quantified on three coronal sections of each brain. The measure used to describe the injury severity correlated with the peak magnitude of the impact force and with peak values of kinematic parameters, particularly the peak change of linear and angular velocity.

Cervical and thoracic juxtafacet cysts causing neurologic deficits.

Study Design. Case reports and review of the literature. Objectives. To review the clinical features, treatment, and outcome of juxtafacet cysts. Summary of Background Data. There have previously been 4 reported cases of thoracic juxtafacet cysts and 19 cases of cervical juxtafacet cysts. Cervical cysts have usually originated from the cruciate ligament and caused myelopathy. Thoracic cysts are usually signaled by myelopathy. Methods. The records of the Neurosurgery Department of Royal Adelaide Hospital from 1980 through 1995 were reviewed for cases of intraspinal juxtafacet cysts. Results. Eight cases of intraspinal juxtafacet cysts were identified; six were in the lumbar spine. One patient had a cervical cyst related to a facet joint and had unilateral radiculopathy. A second patient with a thoracic cyst had the gradual onset of myelopathy. Both patients had surgical excision of the cyst without resection of the adherent dura. The symptoms and neurologic signs improved in each case. Conclusions. Cervical and thoracic juxtafacet cysts are rare lesions that are usually signaled by myelopathy. Results of surgery are excellent in most cases, even if the cyst is not completely excised.

Excitotoxic model of post-traumatic syringomyelia in the rat.

Study Design. A rat model was developed to elucidate the role of excitatory amino acids and spinal subarachnoid block in the genesis of post-traumatic syringomyelia. This excitotoxic model produces intramedullary cavities rather than the dilation of the central canal (canalicular syringomyelia) created by previous animal models. Objectives. To produce extracanalicular cysts in the rat spinal cord with quisqualic acid, a potent agonist of multiple excitatory amino acid receptors, and to compare the effects of excitotoxic injury only with that of excitotoxic injury and subarachnoid block with kaolin. Summary of Background Data. In post-traumatic syringomyelia, primary injury and excitotoxic cell death secondary to elevated levels of excitatory amino acids may initiate a pathologic process leading to the formation of spinal cavities. Subarachnoid block by arachnoiditis may promote enlargement of the cavities. Methods. Three control rats received a unilateral injection of normal saline into the spinal cord, and another five rats received an injection of kaolin into the spinal subarachnoid space. Quisqualic acid was injected unilaterally into the spinal cord of 20 rats, and 13 additional rats received a unilateral injection of quisqualic acid into the spinal cord after injection of kaolin into the subarachnoid space. Histologic and immunocytochemical assessments were undertaken. Results. In the control groups, no parenchymal cyst developed in any of the animals. Spinal cord cyst formation was observed in 16 of 19 animals in the quisqualic acid groups, but no cysts exceeding two segments in the length of the spinal cord developed in any of the rats. Much larger cavities were seen in 9 of 11 animals in the group with quisqualic acid and kaolin, and cysts exceeding two segments developed in all 9 of these (9/11; 82%). Conclusions. In post-traumatic syringomyelia, excitotoxic cell death occurring secondarily to elevated levels of excitatory amino acids may contribute to the pathologic process leading to the formation of spinal cord cysts. Subarachnoid block by arachnoiditis is likely to cause enlargement of the cavity.

Altered subarachnoid space compliance and fluid flow in an animal model of posttraumatic syringomyelia.

Study Design. A histologic study of cerebrospinal fluid tracers in Sprague-Dawley rats undergoing lumboperitoneal shunt insertion in the excitotoxic animal model of posttraumatic syringomyelia (PTS). Objectives. To determine the effects of cerebrospinal fluid (CSF) diversion from the subarachnoid space on perivascular flow (PVS) and syrinx formation in posttraumatic syringomyelia. Summary of Background Data. In an animal model of PTS, fluid enters syringes from the subarachnoid space via perivascular spaces. Preferential PVS flow occurs at the level of the syrinx. It has been suggested that arachnoiditis predisposes to posttraumatic syringomyelia formation by obstructing subarachnoid cerebrospinal fluid flow and enhancing perivascular flow. Materials and Methods. Thirty-two male Sprague-Dawley rats were investigated using the CSF tracer horseradish peroxidase (HRP), the excitotoxic model of PTS, and lumboperitoneal shunt insertion. Five experimental groups consisted of normal controls, syrinx only and shunt only controls, and shunt insertion before or after syrinx formation. In all groups except normal controls, CSF flow studies were performed 6 weeks after the final intervention. Grading scales were used to quantify HRP staining. Results. All excitotoxic model animals formed syringes. Perivascular flow was greatest at the level of the syrinx. Cerebral cortex perivascular flow was significantly reduced after shunt insertion in animals with a syrinx (P < 0.05). Shunt insertion did not alter syrinx length or size. There were no significant differences between shunt and syrinx first groups. Conclusions. Increasing caudal subarachnoid space compliance with a shunt does not affect local CSF flow into the spinal cord and syrinx. These results suggest that localized alterations in compliance, as opposed to obstruction from traumatic arachnoiditis, may act as an important factor in syrinx pathogenesis.

The role of excitotoxic injury in post-traumatic syringomyelia

Fifty percent of patients with neurological deterioration from post-traumatic syringomyelia do not respond to treatment. Treatment failure is due in part to an incomplete understanding of the underlying aetiology. An animal model that mimics the human disease is required to investigate underlying pathophysiology and treatment options. A previous study was designed to mimic trauma-induced effects on the spinal cord that result in syringomyelia, combining an excitotoxic insult with kaolin-induced arachnoiditis. In this excitotoxic model, syringes were produced in 82% of animals. The aims of the current study were to improve the model to produce syringes in all animals treated, to examine the relative influences of excitotoxic injury and neuronal loss on syrinx formation, and to use magnetic resonance imaging (MRI) to examine syringes non-invasively. A temporal and dose profile of intraparenchymal quisqualic acid (QA) and subarachnoid kaolin was performed in Sprague Dawley rats. MRI was used to study four syrinx and six control animals. In one subgroup of animals surviving for 6 weeks, 100% (eight of eight) developed syringes. Syrinx formation and enlargement occurred in a dose and time dependent manner, whilst significant neuronal loss was only dose dependent. Animal syrinx histology closely resembled human post-traumatic syringomyelia. Axial T2-weighted MR images demonstrated syrinx presence. The results suggest that the formation of an initial cyst predisposes to syrinx formation in the presence of subarachnoid adhesions.

Cerebrospinal Fluid Leaks in Orbital and Lacrimal Surgery

Cerebrospinal fluid leakage is an uncommon but significant complication of orbital and rarely lacrimal surgery which may have serious consequences including death. In a retrospective review of four orbital units, we report an incidence of cerebrospinal fluid leak (diagnosed intraoperatively) during exenteration, orbital decompression, and dacryocystorhinostomy of 1/154 (0.6%), 4/397 (1%), and 0/3,504 (0%), respectively. We found two additional cases of cerebrospinal fluid leaks associated with excision of orbital masses involving the orbital roof. In the literature, the incidence of cerebrospinal fluid leaks associated with orbital exenterations and decompressions was 1.6-16.7% and 0-10%, respectively. Cerebrospinal fluid leaks occur very rarely in dacryocystorhinostomies with only a few case reports found in the literature. Preventative measures, diagnosis, and management of this complication are discussed. Knowledge of anatomy and thorough preoperative assessment may predict areas at high risk for encountering cerebrospinal fluid leaks. Proper surgical technique further minimizes the risk for this complication. If a cerebrospinal fluid leak occurs, however, prompt diagnosis and management usually results in uncomplicated recovery.