Adjunctive Use of Bone Growth Stimulation Increases Cervical Spine Fusion Rates in Patients at Risk for Pseudarthrosis

STUDY DESIGN

A prospective multicenter clinical trial (NCT03177473) was conducted with a retrospective cohort used as a control arm.

OBJECTIVE

The purpose of this study was to evaluate cervical spine fusion rates in subjects with risk factors for pseudarthrosis who received pulsed electromagnetic field (PEMF) treatment.

SUMMARY OF BACKGROUND DATA

Certain risk factors predispose patients to pseudarthrosis, which is associated with prolonged pain, reduced function, and decreased quality of life.

METHODS

Subjects in the PEMF group were treated with PEMF for 6 months postoperatively. The primary outcome measure was fusion status at the 12-month follow-up period. Fusion status was determined using anterior/posterior, lateral, and flexion/extension radiographs and computed tomography (without contrast).

RESULTS

A total of 213 patients were evaluated (PEMF, n=160; Control, n=53). At baseline, the PEMF group had a higher percentage of subjects who used nicotine ( P =0.01), had osteoporosis ( P <0.05), multi-level disease ( P <0.0001), and were >65 years of age ( P =0.01). The PEMF group showed over two-fold higher percentage of subjects that had ≥3 risk factors (n=92/160, 57.5%) compared with the control group (n=14/53, 26.4%). At the 12-month follow-up, the PEMF group demonstrated significantly higher fusion rates compared with the control (90.0% vs. 60.4%, P <0.05). A statistically significant improvement in fusion rate was observed in PEMF subjects with multi-level surgery ( P <0.0001) and high BMI (>30 kg/m 2 ; P =0.0021) when compared with the control group. No significant safety concerns were observed.

CONCLUSIONS

Adjunctive use of PEMF stimulation provides significant improvements in cervical spine fusion rates in subjects having risk factors for pseudarthrosis. When compared with control subjects that did not use PEMF stimulation, treated subjects showed improved fusion outcomes despite being older, having more risk factors for pseudarthrosis, and undergoing more complex surgeries.

Pulsed Electromagnetic Field Stimulation in Lumbar Spine Fusion for Patients With Risk Factors for Pseudarthrosis

BACKGROUND

Lumbar spinal fusion surgeries are increasing steadily due to an aging and ever-growing population. Patients undergoing lumbar spinal fusion surgery may present with risk factors that contribute to complications, pseudarthrosis, prolonged pain, and reduced quality of life. Pulsed electromagnetic field (PEMF) stimulation represents an adjunct noninvasive treatment intervention that has been shown to improve successful fusion and patient outcomes following spinal surgery.

METHODS

A prospective, multicenter study investigated PEMF as an adjunct therapy to lumbar spinal fusion procedures in patients at risk for pseudarthrosis. Patients with at least 1 of the following risk factors were enrolled: prior failed fusion, multilevel fusion, nicotine use, osteoporosis, or diabetes. Fusion status was determined by radiographic imaging, and patient-reported outcomes were also evaluated.

RESULTS

A total of 142 patients were included in the analysis. Fusion status was assessed at 12 months follow-up where 88.0% (n = 125/142) of patients demonstrated successful fusion. Fusion success for patients with 1, 2+, or 3+ risk factors was 88.5%, 87.5%, and 82.3%, respectively. Significant improvements in patient-reported outcomes using the Short Form 36, EuroQol 5 Dimension (EQ-5D) survey, Oswestry Disability Index, and visual analog scale for back and leg pain were also observed compared with baseline scores (P < 0.001). A favorable safety profile was observed. PEMF treatment showed a positive benefit-risk profile throughout the 6-month required use period.

CONCLUSIONS

The addition of PEMF as an adjunct treatment in patients undergoing lumbar spinal surgery provided a high rate of successful fusion with significant improvements in pain, function, and quality of life, despite having risk factors for pseudarthrosis.

CLINICAL RELEVANCE

PEMF represents a useful tool for adjunct treatment in patients who have undergone lumbar spinal surgery. Treatment with PEMF may result in improved fusion and patient-reported outcomes, regardless of risk factors.

TRIAL REGISTRATION

NCT03176303.

Self-reported concussion history among midwestern skiers and snowboarders

Aim

To assess the rate of self-reported concussion in midwestern skiers and snowboarders.

Patients

Recreational skiers and snowboarders between the ages of 14 and 69 years during a single winter ski season (2020-2021) at a ski area in Wisconsin, USA.

Methods

Survey study.

Results

Among this survey population (n = 161), 9.32 and 19.25% reported one or more diagnosed concussion and suspected concussion respectively as a result of a skiing- or snowboarding-related incident. Skiers and snowboarders that self-identified as advanced, those who utilized terrain park features, and those that participated in freestyle competition had significantly higher self-reported rates of concussion.

Conclusion

Self-reported concussion history indicates a concussion prevalence that is higher than expected based on previous studies. Participants reported significantly more suspected concussions than diagnosed concussions, indicating a possible issue with underreporting in this population.

Forme sévère de COVID-19 pendant la première vague épidémique en France : rôle des facteurs sociaux et des traitements empiriques

Introduction

La COVID-19 est une maladie multiforme, allant d’un rhume banal au syndrome de détresse respiratoire aiguë. L’identification précoce des patients à risque de forme sévère est cruciale. Le sexe masculin, l’âge, l’obésité et diverses comorbidités sont maintenant clairement reconnus comme associés à une évolution défavorable. La vaste étude britannique OpenSafely suggère qu’au-delà de l’état de santé individuel, l’ethnicité et le désavantage social sont associés significativement avec la mortalité hospitalière au cours des infections par le SARS-CoV-2, mais très peu de données sont disponibles en France à ce sujet.

L’objectif principal de ce travail était d’étudier les facteurs, notamment socioéconomiques, associés à la survenue d’une forme grave. L’objectif secondaire était d’étudier le rôle des traitements empiriques utilisés par les praticiens.

Matériels et méthodes

Tous les patients adultes ayant eu un diagnostic par PCR d’infection à SARS-CoV-2 de mars à mai 2020 dans un hôpital français ont été inclus. Les femmes enceintes et les cas nosocomiaux ont été exclus. Les données des dossiers médicaux ont été recueillies de manière anonymisée via un e-CRF. L’adresse du patient a été utilisée pour obtenir l’IRIS du domicile et la correspondance avec deux indicateurs socioéconomiques validés : FDEP et French EDI. Les traitements empiriques utilisés par les praticiens ont été recueillis. Les facteurs associés à une forme grave, définie par la survenue du décès ou la nécessité d’une ventilation mécanique, ont été étudiés à l’aide de modèles de Cox.

Résultats

Parmi 399 patients inclus à partir des urgences, 78 patients sont retournés au domicile et 25 ont été transférés dans un autre hôpital. Parmi les 296 patients hospitalisés, 91 ont présenté une forme sévère (68 décès). L’origine ethnique, le FDEP et le FEDI n’étaient pas associés à la survenue d’une forme grave. Parmi les différentes comorbidités, un IMC > 25, un antécédent cardiovasculaire, au moins deux comorbidités étaient associés à la survenue d’une forme grave en analyse univariée. Les facteurs associés à la survenue d’une forme grave lors de l’analyse multivariée étaient : âge > 80 ans (HR : 2,2 [1,3–3,5]), surpoids (HR : 2,3 [1,4–3,7]), lésions sévères au TDM thoracique (HR : 3,3 [2,0–5,3]). La prescription d’une corticothérapie pendant au moins 48 h était un facteur protecteur (HR : 0,4 [0,2–0,6]).

Conclusion

Aucune association entre ethnicité ou désavantage social et survenue d’une forme sévère de COVID-19 n’a été retrouvée dans notre population. La prescription d’une corticothérapie était un facteur protecteur.

Comparison of presentations to the emergency department during the COVID-19 pandemic (COPED-C)

BACKGROUND

Concerns have been raised that patients requiring emergency care may not have accessed healthcare services during coronavirus disease 2019 (COVID-19) lockdown.

METHODS

This case control study aimed to understand changes in characteristics and diagnosis of patients attending a large UK Emergency Department (ED) during the first wave of the COVID-19 pandemic (March-May 2020) compared with equivalent weeks in 2019.

RESULTS

We found a 50.7% drop in first attendances to the ED in 2020. Likelihood of attendance and admission decreased for paediatric patients and increased for patients ≥ 46 years, and for men. Likelihood of admission increased for all Black ethnic groups and for patients from the most deprived index of multiple deprivation quintiles. This shift to an older, male, more deprived patient population with greater representation of ethnic minority groups was amplified in the 'Infections' diagnostic category.

CONCLUSIONS

COVID-19 has dramatically impacted ED usage. Our analysis contributes to local resource planning and understanding of changes in healthcare-seeking behaviour during the pandemic. Future research to identify positive behaviour changes could help sustain a reduction in non-urgent visits in the longer term.

Does the application of Opsite⋄ Flexigrid⋄ occlude the oxygen saturation readings in healthy individuals using the moorVMS-OXY machine?

Background

A proportion of people who have been diagnosed with peripheral arterial disease and diabetes mellitus will be susceptible to chronic wounds. Oxygen is vital for wound healing, so oxygen measurements should to be taken as predictive values for wound healing in patients. When measuring oxygen at the wound bed, there is potentially a risk of cross-infection if no protective barrier is used; and skin stripping if an adhesive barrier is used on the wound bed. This cross sectional within subject repeated measures pilot study, aims to determine if the application of opsite film, as an infection control measure, in one or two layers, impacts on tissue oxygenation readings obtained when using the MoorVMS-OXY.

Methods

Mean oxygen saturation percentages were measured from 29 limbs of 18 healthy participants. Oxygen saturation was measured for 20 s and analysed at the first metatarsophalangeal joint using no film, one and two layers using the MoorVMS-OXY. A one-way repeated ANOVA with a Bonferroni post hoc test was performed to test for statistically significant differences between the values of the three parameters and multiple pairwise comparisons was completed.

Results

Amongst the three layers, there was a statistically significant difference in oxygen saturation between the two layers of Opsite Flexigrid and none; and also between the two layers of Flexigrid and single layer (p < 0.05). It was also established that there was no statistically significant difference between the single layer of Opsite Flexigrid and no Flexigrid layer (p > 0.05).

Conclusions

The results imply that one layer of Opsite Flexigrid is a suitable protective barrier to use when establishing capillary bed oxygen perfusion with the MoorVMS-OXY. However, the application of two Opsite Flexigrid layers, to prevent skin stripping, decreases the recorded values of oxygen saturation percentages significantly, therefore providing inaccurate results. Indicating that a double layer cannot be used over ulceration sites if measuring oxygen levels at the wound bed.

Cardiac Response to Exercise in Normal Ageing: What Can We Learn from Masters Athletes?

BACKGROUND

Ageing is associated with an inexorable decline in cardiac and vascular function, resulting in an increased risk of Cardiovascular Disease (CVD). Lifestyle factors such as exercise have emerged as a primary therapeutic target in the prevention of CVD, yet older individuals are frequently reported as being the least active, with few meeting the recommended physical activity guidelines. In contrast, well trained older individuals (Masters athletes) have superior functional capacity than their sedentary peers and are often comparable with young non-athletes. Therefore, the 'masters' athlete may be viewed as a unique non-pharmacological model which may allow researchers to disentangle the inexorable from the preventable and the magnitude of the unavoidable 'true' reduction in cardiac function due to ageing.

CONCLUSION

This review examines evidence from studies which have compared cardiac structure and function in well trained older athletes, with age-matched controls but otherwise healthy.

Germanium-On-Insulator (GeOI) structure realized by the Smart Cut™ technology

First results on formation of thin film GeOI structures by the Smart Cut™ technology are presented in this paper. Thin single crystal layers of Ge have been successfully transferred, via oxide bonding layer, onto standard Si substrates with diameters ranging from 100 to 200 mm. Compared to SOI manufacturing, the development of GeOI requires adaptation to the available germanium material, since the starting material can be either bulk Ge or an epitaxial layer. Some results will be presented for GeOI formation according to the different technological options. Germanium splitting kinetics will be discussed and compared to already published results. To show good quality of the GeOI structures, detailed characterization has been done by TEM cross sections for defect densities, interfaces abruptness and layers homogeneities evaluation. AFM was used for surface roughness measurements. These results help define procedures that are required to achieve large diameter high quality GeOI structures.

Optical coherence refractometry

We introduce a novel approach to refractometry using a low coherence interferometer at multiple angles of incidence. We show that for plane parallel samples it is possible to measure their phase refractive index rather than the group index that is usually measured by interferometric methods. This is a significant development because it enables bulk refractive index measurement of scattering and soft samples, not relying on surface measurements that can be prone to error. Our technique is also noncontact and compatible with in situ refractive index measurements. Here, we demonstrate this new technique on a pure silica test piece and a highly scattering resin slab, comparing the results with standard critical angle refractometry.

Clinical significance of terminal syringomyelia in association with pediatric tethered cord syndrome

An association between terminal syringomyelia (TS) and tethered cord syndrome (TCS) has been recognized. The clinical significance of TS and the need for concurrent treatment is not known. Thirty-four patients with TCS undergoing surgery for tethered cord release were evaluated for the incidence of TS. The clinical and radiological response to untethering with and without syrinx drainage was assessed. The group incidence of TS was 29.4%. There were no significant differences in the sex, age, underlying pathology or preoperative symptoms between the TCS group (TCS, n = 24) and the TCS group with TS (TCS + TS, n = 10). In the TCS group, 37.5% of the patients were asymptomatic preoperatively, and in the TCS + TS group 50% were asymptomatic preoperatively. After surgery, none of these asymptomatic patients developed symptoms. All of the symptomatic TCS + TS patients improved clinically, 12 of 15 symptomatic TCS patients improved, 2 patients were unchanged and 1 had worsening scoliosis. Syrinx did not develop in patients lacking it preoperatively. In patients where postoperative imaging was available, preoperative syringes improved. TS is clearly associated with TCS. Tethered cord release alone may be sufficient to improve preoperative symptoms and TS may be an associated phenomenon that does not mandate separate treatment.

Acute subdural hematoma caused by an unruptured, thrombosed giant intracavernous aneurysm

INTRODUCTION

Acute subdural hematoma (SDH) is an infrequent complication after aneurysmal subarachnoid hemorrhage. SDH associated with unruputed intracavernous aneurysm has never been reported.

METHODS

Single patient case report and review of relevent literature.

RESULTS

A 65-year-old woman with an unruptured, thrombosed giant intracavernous aneurysm developed an acute SDH 2 days after admission for cavernous sinus syndrome. Despite emergent evacuation of the SDH, the patient never regained consciousness because of brain herniation.

CONCLUSION

Acute SDH is a rare complication of ruptured, giant intracavernous aneurysms. Erosion of the cavernous sinus wall by acute enlargement of the aneurysm after thrombosis is the proposed mechanism for development of the SDH.

Bolus tracer delivery measured by MRI confirms edema without blood-brain barrier permeability in diffuse traumatic brain injury

INTRODUCTION

Previous studies have shown that edema formation after diffuse traumatic brain injury (TBI) with secondary insult is cytotoxic and not vasogenic. This assumption is based on observations of reduced apparent diffusion coefficient (ADC) and lack of significant accumulation of intravascular tracer in brain tissue. However, ADC reduction does not exclude vasogenic edema, and intravascular tracer can only accumulate when it reaches the tissue and is not perfusion limited. This study aims to confirm tissue delivery of intravascular tracer and lack of BBB opening during a phase of rapid brain swelling after diffuse TBI.

METHODS

Rats were exposed to either TBI using the impact acceleration model combined with 30 minutes of hypoxia and hypotension, or sham injury. At 2 or 4 hours after injury, ADC and tissue water content were assessed using MRI. Gd-DTPA was given followed by a combination of rapid T2 imaging (60 seconds) and T1 imaging (30 minutes). Signal intensity changes were analyzed to determine a bolus effect (dynamic susceptibility contrast) and longer-term tissue accumulation of Gd-DTPA.

RESULTS

Mean increase in cortical water content on the left was 0.8% at 2 hours, 2.1% at 4 hours; on the right it was 0.5% at 2 hours and 1.7% at 4 hours (p < 0.05). Mean ADC reduction over 4 hours was 0.04 x 10(-3) mm2/s on the left and 0.06 x 10(-3) mm2/s on the right. Kinetic analysis of signal intensity changes after Gd-DTPA showed no significant difference in inward transfer coefficient (BBB permeability) between sham injury and 2 or 4 hours post-injury. T2 imaging showed consistent tissue delivery of a bolus of Gd-DTPA to the tissue at 2 and 4 hours post-injury, comparable to sham animals.

CONCLUSIONS

Progressive cerebral edema formation after diffuse TBI occurred during ADC reduction and without continued BBB permeability. Tissue delivery of Gd-DTPA was confirmed, verifying that lack of tracer accumulation is due to an intact BBB and not to limited perfusion.

CT prediction of contusion evolution after closed head injury: the role of pericontusional edema

BACKGROUND

Cerebral contusions have a 51% incidence of evolution in the first hours after injury. Evolution is associated with clinical deterioration and is the reason for ICP monitoring or surgical intervention. We sought to define CT features that predict cerebral contusion evolution.

METHODS

Patients treated for cerebral contusion who had 2 CT scans within 24 hours after injury were evaluated (n = 21). CT scans were analyzed for area of contusion, hemorrhagic components, and edema. Increase (%) in contusion size was recorded. Contusion evolution was defined as > 5% size increase. Ratios of hemorrhagic components to surrounding edema were calculated.

RESULTS

Ten patients (47.6%) showed contusion evolution and 11 (52.4%) did not. Age, sex ratio, or injury severity between the 2 groups did not differ. Eight of 10 patients with evolving contusions had minimal or no perilesional edema on first CT; only 2 of 11 nonevolution patients had perilesional edema (p < 0.005). Mean ratio of area of surrounding edema to area of hemorrhagic products on first CT was 0.770 in evolution group versus 2.22 in non-evolution group (p = 0.055).

CONCLUSIONS

A higher proportion of patients without contusion evolution had perilesional edema present on first CT scan. The absence of pericontusional edema on early CT may be a useful marker to predict contusion evolution.

Clinical and radiological relationship between posterior lumbar interbody fusion and posterolateral lumbar fusion

BACKGROUND

Posterolateral lumbar fusion (PLF) is the most popular technique for stabilizing the lumbar spine. Biomechanically, PLF decreases segmental motion in the posterior column, which presumably reduces facet joint pain. Posterior lumbar interbody fusion (PLIF) may decompress nerve roots by distracting the collapsed disc space, and achieving optimal fusion in relation to load-bearing capacity. The purpose of the study was to examine the role of interbody fixation vs pedicle fixation in transverse lumbar fusion and to assess treated and adjacent disc space height changes over time.

METHODS

One hundred patients who underwent PLIF and noninstrumented transverse process fusion (n = 55) or instrumented PLF (n = 45) between 1996 and 1998 were evaluated retrospectively. Outpatient charts and follow-up films were reviewed. Bone fusion was determined using Brantigan and Steffee's classification and clinical outcome by the Prolo scale. Disc space heights at the fusion and adjacent levels were measured. Analysis of variance and chi(2) statistical techniques were used for data analysis.

RESULTS

Disc space height was increased and better maintained in PLIF patients. PLIF resulted in a nonsignificant tendency toward higher fusion rates. No differences in clinical and functional outcomes were found between the groups. There was no correlation between preservation of disc space height and clinical outcome.

CONCLUSIONS

Disc space height does not seem to impact clinical outcome in lumbar fusion, and efforts to maintain it may be unwarranted.

[Increasing cerebral perfusion pressure in serious cranial injury--contradictory effects of dopamine]

BACKGROUND

Management of cerebral perfusion pressure is an important element of the treatment of traumatic brain injury. Vasopressors are accepted as a method of choice to increase mean arterial blood pressure and thus cerebral perfusion pressure in the face of rising intracranial pressure. There are, however, some unresolved issues and potential risks to this therapy.

MATERIAL AND METHODS

This study therefore examines the effects of dopamine on physiological changes as well as on brain edema and water content that can be readily assessed by MRI/MRS in (1) a rodent model of rapidly rising intracranial pressure, caused by diffuse injury with secondary insult and (2) a model of cortical contusion.

RESULTS

Dopamine was capable of restoring cerebral perfusion pressure in the model of rapidly rising intracranial pressure. However, this was associated with only a partial restoration of cerebral blood flow. In the brain tissue two profiles of change in the apparent diffusion coefficient of water (ADCw) were seen; one in which ADCw recovered to baseline, and one in which ADCw remained persistently low. Despite that dopamine did not alter these profiles, MRI-assessed tissue water content was increased four hours after injury and dopamine increased cerebral water content in both subgroups of injury, especially in the subgroup with a persistently low ADCw (p < 0.01). In the contusion group dopamine significantly worsened the edema both in the injured and in the contralateral area of hippocampus and temporal cortex even though the ADCw values did not change, except for the contralateral hippocampus, where both water content and ADC, values rose with treatment, suggesting extracellular accumulation of water.

CONCLUSION

The results suggest that dopamine has a double effect--while it temporarily and partially restores cerebral blood perfusion, at the same time it induces an increase in brain swelling and thus an increase in intracranial pressure in some cases. It is possible that in a subgroup of patients vasopressor treatment leads to an opposite effect several hours later. Vasopressor therapy in the clinical setting therefore should be cautiously applied.

Acute subdural hematoma associated with diffuse brain injury and hypoxemia in the rat: effect of surgical evacuation of the hematoma

The aim of this study was to assess the effect of rapid or delayed surgical evacuation on the physiological consequence and brain edema formation in a rat model of acute subdural hematoma (SDH) coupled with either diffuse brain injury (DBI) or hypoxemia. The SDH was made by an autologous blood injection, while DBI was induced using the impact acceleration model (mild, 450 g/1 m; severe, 450 g/2 m). Physiological parameters measured included intracranial pressure (ICP), mean arterial blood pressure (MABP), cerebral blood flow (CBF), and brain tissue water content. At 1 h (rapid evacuation) or 4 h (delayed evacuation) after the SDH induction, surgical evacuation following a craniotomy was performed using saline irrigation and forceps. The study consisted of three different series, including 400 microL of SDH alone (Series 1), SDH400 + mild DBI (Series 2), and SDH300 + severe DBI + 20 min hypoxemia (Series 3). The hypoxemia was added in Group 3 to produce a steadily increasing ICP. In Series 1 and 2, all rats were randomized into the three following groups: non-, rapid, and delayed evacuation; Series 3 had two groups: non- and rapid evacuation. In Series 1, the surgical evacuation showed no beneficial effects on the brain edema formation assessed at 5 h post-injury. In Series 2, the rapid, but not delayed, evacuation significantly reduced both the increased ICP level and brain water content. The additional insult of hypoxemia (Series 3) resulted in a progressive ICP elevation, persistently depressed CBF, and severe brain swelling. Under this situation, the rapid evacuation exacerbated brain edema. These results have clinical implications for the management of severe traumatic SDH, especially its operative indication and timing.

A new rat model of diffuse brain injury associated with acute subdural hematoma: assessment of varying hematoma volume, insult severity, and the presence of hypoxemia

The aim of this study was to develop a new rat model of diffuse brain injury (DBI) associated with acute subdural hemorrhage (SDH). In order to make this model more clinically relevant, we determined whether the varying hematoma volume, severity of DBI, or the presence of hypoxemia could influence the physiological consequence. SDH was made by an autologous blood injection, while DBI was induced using the impact acceleration model (mild, 450 g/1 m, severe, 450 g/2 m). Physiological parameters measured included intracranial pressure (ICP), mean arterial blood pressure (MABP), cerebral blood flow (CBF), and brain tissue water content. In the first series, 23 rats were randomized into the five following groups: Group 1, sham; Group 2, 400 (microL SDH; Group 3, SDH400 + mild DBI; Group 4, SDH400 + severe DBI; and Group 5, SDH300 + severe DBI. Results suggested that SDH300 + severe DBI (Group 5) may be the most suitable model, in which the MABP and CBF temporarily decreased during the SDH induction, but thereafter recovered to the baseline. Conversely, ICP was persistently elevated throughout the experiment. The water content was also significantly higher in both hemispheres compared to that of sham. In the second series, the animal was exposed to a hypoxemic insult (10 or 30 min) in addition to SDH300 + severe DBI (Group 6). The prolonged hypoxemia caused both a severe CBF reduction without recovery and a bilateral brain swelling, whereas the brief hypoxemia showed a gradual CBF recovery from the transient reduction and an increased water content only in the SDH side. These results suggest that these models may be potentially useful to study the combination of DBI and SDH with or without hypoxemia.

Application of chemical shift imaging for measurement of NAA in head injured patients

Neurochemical damage following brain injury can be assessed non-invasively by measurement of N-Acetyl-Aspartate (NAA) using Proton Magnetic Resonance Spectroscopy (1HMRS). This report documents results of applying Chemical Shift Imaging (CSI) postprocessing for measuring NAA in traumatically injured brain. Following stabilization, severely head-injured patients (GCS 8 or less) were transported to the MRI suite. Semi-quantitative measurement of NAA, creatine (Cr/PCr) and choline (Cho) were obtained from single voxels (8 cm3) and CSI for acquisition of smaller voxels (2 cm3) throughout areas of the brain. Studies were completed with no complication. In focal injury, SVS positioned at the site of lesion demonstrated reduced NAA, compared to contralateral hemisphere. In diffuse injury, CSI demonstrated uniform reduction of NAA throughout the brain. NAA/Cho showed normal levels within 24 hours of injury averaging 2.4 and decreased over the next 10 days reaching a plateau of 0.75. At 30 days, NAA showed no recovery in poor outcome patients. In patients with good outcome, NAA initially low recovered near baseline levels. CSI provides a comprehensive neurochemical assessment of neuronal damage. NAA decreases and remains low in patients with poor outcome. NAA recovers in patients with favorable outcome, suggesting marginal metabolic impairment and possible re-synthesis of the NAA pool.

Diffuse brain injury complicated by acute subdural hematoma in the rodents: the effect of early or delayed surgical evacuation

Of all the possible clinical factors affecting the outcome of patients suffering acute subdural hematomas (SDH), timing of surgical evacuation is certainly the most debated. The purpose of this study was to develop an experimental model able to reproduce the clinical behavior of post-traumatic SDH as observed in head injured patients. We present a novel model of SDH combined with diffuse brain injury (DBI), and investigate the effects of early and delayed surgical evacuation. Following Impact Acceleration DBI, adult Sprague-Dawley rats were given a 400 microliters SDH. Hematoma was then evacuated at one (rapid evacuation) or four hours (delayed evacuation) post-injury. Physiological parameters were measured for 5 hours, followed by the assessment of brain water content. In this experimental model, there is strong evidence that trauma acts synergistically with SDH enhancing brain edema formation and increasing ICP. In absence of secondary insult, rapid evacuation of traumatic SDH limits exposure to high ICP, reduces brain edema and is beneficial.

Approximate entropy: a regularity statistic for assessment of intracranial pressure

INTRODUCTION

Waveform analysis of ICP and mABP provideqs important information about cerebrovascular reactivity and intracranial compliance. Traditionally spectral analysis and correlation statistics have been used despite certain limitations. Approximate entropy (ApEn) is an established measure of system regularity; which can change with pathology. This study defines a novel method for application of ApEn to the ICP/mABP waveform, and reports changing ApEn with pathophysiology in the rodent brain.

METHODS

Nine Sprague-Dawley rats were anesthetized for mABP, and ICP recording. Rats were exposed to 15 minutes hypotension (45-50 mmHg), followed by resuscitation, equilibration and infusion of a 500 ul subdural hematoma. Raw data, ApEn(RAW), and wave-period, ApEn(PERIOD), were assessed for stochastic fluctuations using ApEn (m = 2, r = 0.2 SD). Results were compared with the established parameters: standard deviation, harmonic transfer function, Pressure Reactivity Index and Correlation Coefficient.

RESULTS

At baseline, ApEn(ABP-PERIOD) and ApEn(ICP-PERIOD) were 1.464 +/- 0.003, and 0.690 +/- 0.020 respectively, suggesting that random heart rate fluctuations are damped during transfer to the ICP waveform. ApEn(ICP-PERIOD) consistently rose during hypotension (ICP 7 +/- 2: ApEn(ICP-PERIOD) 1.086 +/- 0.074, p < 0.05) and after SDH infusion (ICP 35 +/- 12: ApEn(ICP-PERIOD) 1.24 +/- 0.03, p < 0.01). These values were closer to mABP and suggest enhanced transfer of random fluctuations. Significant changes in ApEn were seen in the absence of significant changes in other parameters.

CONCLUSIONS

This study defines a system for analyzing the transfer of random fluctuations in mABP waveform to the ICP waveform. ApEn appears to be responsive to changes in intracranial compliance and/or cerebrovascular resistance, therefore more formal studies of the sensitivity and specificity of this novel measure are warranted. These initial findings suggest that ApEn may be a useful adjunct measure of the ICP waveform.

Secondary insults worsen blood brain barrier dysfunction assessed by MRI in cerebral contusion

OBJECT

Understanding the cause of post-traumatic intracranial hypertension requires information about the pathophysiology of edema formation. Secondary insults are known to exacerbate edema formation following experimental contusion, however the influence of these insults on blood brain barrier (BBB) integrity is not known. This study non-invasively assesses the influence of hypoxia and hypotension on BBB permeability following experimental cortical contusion.

METHODS

Sprague-Dawley rats (350-380 g) were divided into three groups. Group A: (n = 3) Sham, Group B (n = 8) focal injury (controlled cortical impact 6.0 m/sec, 3 mm depth), Group C (n = 8), focal injury with secondary insult. Cortical BBB integrity was assessed four hours post-trauma using an i.v. bolus of 0.2 mmol/kg Gd-DTPA with serial T1 MR images, over 30 minutes. Absolute tissue concentrations of Gd were measured empirically using known references. The time course of accumulation was analyzed with respect to BBB permeability.

RESULTS

BBB permeability was greatest in the site of contusion, and Gd accumulation was greatly enhanced by secondary insult (p < 0.01). Regions of lowest ADC and maximal swelling correlated with regions of maximal BBB permeability (p < 0.05).

CONCLUSIONS

Secondary insults enhance BBB dysfunction in contusion. Positive relationships between low ADC, tissue swelling and BBB dysfunction suggest synergy between underlying cytotoxic swelling and BBB permeability in contusion. These data also suggest that restoration of BBB integrity after injury may be an energy dependent process. These findings have important implications for the pathophysiology of ICP elevations following cerebral contusion.

Diffuse brain injury complicated by acute subdural hematoma and secondary insults in the rodents: the effect of surgical evacuation

Head Trauma associated with acute sudural hematoma (SDH) and complicated by secondary insult is a grave clinical combination with complex pathophysiology. The aim of this study was to develop a clinically relevant injury model, which can be used to study the interaction between injury mechanisms. We present a novel model of SDH combined with diffuse brain injury (DBI) and a hypoxic secondary insult, and investigate the effects of surgical evacuation. Adult Sprague-Dawley rats were given a 300 microliters SDH and 20 minute-hypoxia following Impact Acceleration DBI. Hematoma was evacuated at one hour post-injury. Physiological parameters were measured for 5 hours, together with assessment of brain water content. Secondary insult after traumatic SDH was associated with significant brain swelling and stimulated refractory rise in ICP. In traumatic SDH complicated by secondary insult, brain swelling is exacerbated by surgical evacuation.

Contrasting effects of dopamine therapy in experimental brain injury

Management of cerebral perfusion pressure (CPP) is thought to be important for the treatment of traumatic brain injury (TBI). Vasopressors have been advocated as a method of increasing mean arterial blood pressure (mABP) and cerebral perfusion pressure (CPP) in the face of rising intracranial pressure (ICP). There are unresolved issues and theoretical risks about this therapy. This study therefore examined the effects of dopamine on physiological and MRI/MRS parameters in (1) a rodent model of rapidly rising intracranial pressure, caused by diffuse injury with secondary insult and (2) a model of cortical contusion. Dopamine was capable of restoring CPP in the model of rapidly rising ICP. This CPP restoration was associated with a partial restoration of CBF. Two profiles of change in the Apparent Diffusion Coefficient of water (ADCw) were seen; one in which ADCw recovered to baseline, and one in which ADCw remained persistently low. Dopamine did not alter these profiles. MRI assessed tissue water content was increased four hours after injury and dopamine increased cerebral water content in both subgroups of injury; significantly in the group with a persistently low ADCw (p < 0.01). In contusional injury, dopamine significantly worsened edema in both the ipsi- and contralateral hippocampus and temporal cortex. This occurred in the absence of ADCw changes, except in the contralateral hippocampus, where both water content and ADCw values rose with treatment, suggesting extracellular accumulation of water. In conclusion, although dopamine is capable of partially restoring CBF after injury, situations exist in which dopamine therapy worsens the swelling process. It is possible therefore that subgroups of patients exist who experience adverse effects of vasopressor treatment, and consequently the effects of vasopressor therapy in the clinical setting need to be more carefully evaluated.

N-Acetylaspartate reduction as a measure of injury severity and mitochondrial dysfunction following diffuse traumatic brain injury

N-Acetylaspartate (NAA) is considered a neuron-specific metabolite and its reduction a marker of neuronal loss. The objective of this study was to evaluate the time course of NAA changes in varying grades of traumatic brain injury (TBI), in concert with the disturbance of energy metabolites (ATP). Since NAA is synthesized by the mitochondria, it was hypothesized that changes in NAA would follow ATP. The impact acceleration model was used to produce three grades of TBI. Sprague-Dawley rats were divided into the following four groups: sham control (n = 12); moderate TBI (n = 36); severe TBI (n = 36); and severe TBI coupled with hypoxia-hypotension (n = 16). Animals were sacrificed at different time points ranging from 1 min to 120 h postinjury, and the brain was processed for high-performance liquid chromatography (HPLC) analysis of NAA and ATP. After moderate TBI, NAA reduced gradually by 35% at 6 h and 46% at 15 h, accompanied by a 57% and 45% reduction in ATP. A spontaneous recovery of NAA to 86% of baseline at 120 h was paralleled by a restoration in ATP. In severe TBI, NAA fell suddenly and did not recover, showing critical reduction (60%) at 48 h. ATP was reduced by 70% and also did not recover. Maximum NAA and ATP decrease occurred with secondary insult (80% and 90%, respectively, at 48 h). These data show that, at 48 h post diffuse TBI, reduction of NAA is graded according to the severity of insult. NAA recovers if the degree of injury is moderate and not accompanied by secondary insult. The highly similar time course and correlation between NAA and ATP supports the notion that NAA reduction is related to energetic impairment.

The permissive nature of blood brain barrier (BBB) opening in edema formation following traumatic brain injury

The contribution of blood brain barrier opening to traumatic brain edema is not known. This study compares the course of traumatic BBB disruption and edema formation, with the hypothesis that they are not obligately related. Sprague-Dawley rats were divided into three groups: Group A (n = 47)--Impact Acceleration (IAM); Group B (n = 104)--lateral cortical impact (CCI); Group C (n = 26)--IAM + hypoxia & hypotension (THH). BBB integrity was assessed using i.v. markers (Evan's Blue, or gadolinium-DTPA). Edema formation was evaluated with gravimetry, and T1-weighted MRI. In IAM, BBB opened immediately but closed rapidly, and remained closed for at least the next 36 hours whilst 24-hour hemispheric water content (HWC) rose by 0.9% (p < 0.01). In CCI, BBB opened in both hemispheres for up to 4 hours; four hour HWC in the uninjured hemisphere was indistinguishable from Sham, where HWC in the injured hemisphere rose by approximately 1.5% (p < 0.005). We distinguished two THH animals based on Apparent Diffusion Coefficient (ADC) recovery: in ADC-recovery animals 4 hour cortical water content (CWC) was 80.4 +/- 0.6%, cf 81.4 +/- 1.3% in ADC-non-recovery (p < 0.05). In all animals the BBB was open, however two populations of permeability were seen which likely related to flow-limited extravasation of gadolinium. In IAM edema forms despite only brief BBB opening. Although there is diffuse BBB opening with lateral contusion, edema only forms in the injured hemisphere. In THH, edema formation in the face of a widely permeable barrier is driven by ADC changes or cell swelling. Edema formation clearly does not correspond with BBB opening and an open BBB is clearly not required for edema formation. However we hypothesize that a permeable BBB permissively worsens the process, by acting as a low resistance pathway for ion and water movement. These findings are consistent with our general hypothesis that edema formation after TBI is mainly cytotoxic.

Distinguishing between cellular and vasogenic edema in head injured patients with focal lesions using magnetic resonance imaging

Having determined that edema and not vascular engorgement is the major factor leading to traumatic brain swelling, the objective of this study was to determine which type of edema, cellular or vasogenic, is responsible for increased tissue water in patients with focal lesions. Severely head injured patients (GCS 8 or less) were transported to imaging suites for measurement of brain water and apparent diffusion coefficient (ADC) using magnetic resonance technique. Cerebral blood flow by stable Xenon method was also measured in the regions of interest. Brain water was increased significantly in the hemisphere with lesion. The increase in water was associated with reduced ADC signifying a predominant cellular edema. The ADC in the contralateral hemisphere was near normal value. Cerebral blood flow values in the regions of interest were above ischemic levels suggesting that factors other than ischemia are responsible for the cytotoxic swelling in patients with focal injury.

The synergistic effect of acute subdural hematoma combined with diffuse traumatic brain injury on brain edema

It is well-documented that acute subdural hematoma (ASDH) following diffuse traumatic brain injury (dTBI) contributes to severe disability and high mortality. The objective of this study was to characterize edema formation in a model of ASDH and ASDH following dTBI. Eighteen Sprague-Dawley rats were separated into three groups: Sham operated (n = 6), ASDH (n = 6), ASDH following dTBI (n = 6). Diffuse TBI was produced via the Impact-Acceleration Model [10]. ASDH was induced in the left hemisphere using the well-described method [11]. Total tissue water content was determined 4 hours after TBI utilizing wet-weight/dry-weight assessment. Our results show that ASDH causes a significant increase in tissue water content in the left hemisphere (79.2 +/- 0.7%) compared with the contralateral hemisphere (78.5 +/- 0.5%, p = 0.009). Animals exposed to ASDH following dTBI had significantly greater edema formation than those with ASDH (right: 80.9 +/- 0.4%, left: 80.5 +/- 0.7, p = 0.008). There was no significant difference between the left and right hemisphere. We conclude that edema formation in ASDH is worsened by the combination of dTBI and ASDH. Furthermore a diffuse and focal injury in combination retain the features of the diffuse injury, but with increased severity. Further studies are required to elucidate the synergistic mechanisms involved in these pathological processes.

Characterizing edema associated with cortical contusion and secondary insult using magnetic resonance spectroscopy

It is traditionally believed that edema associated with brain contusion is vasogenic. The objective of this study was to quantify and characterize the edema in cortical contusion coupled with early hypoxia and hypotension. Sprague-Dawley rats were randomised into six groups: Sham, Trauma moderate (Tm), Trauma severe (Ts), Hypoxia and Hypotension (HH), Tm and Ts with HH (THHm; THHs). Trauma was induced with controlled cortical impact; associated secondary insults lasted 30 minutes. Water content was measured using tissue longitudinal relaxation time (T1). Apparent diffusion coefficient of water (ADC) was calculated from diffusion-weighted imaging and single voxel spectroscopy. In the trauma groups ICP increased at 30 minutes post trauma (p < 0.05) and then gradually decreased. Only in the THH groups, ICP showed a trend to continually rise. No ICP variations were seen in the others groups. The increase in water content at 4 hours post trauma was inversely related to ADC variation (p < 0.0001). A significant increase in water content with low ADC, developed in the injured region in Ts, THHm (p < 0.05) and THHs (p < 0.01) compared to Sham. Intracellular water rose in the whole brain in THH groups although more severely in the THHs (p < 0.01). Immediately after trauma ADC fell in the THH groups, but gradually increased in the THHm, whereas there was no recovery in THHs. The results indicate that the type of edema in the injured area, with and without superimposed secondary insult, is predominantly cytotoxic (cellular). Moreover, secondary insults act synergistically with focal injury to increase cellular water in both injured tissue and remote regions.

Comparison of NAA measures by MRS and HPLC

This work investigates the accuracy of an in vivo estimation of absolute N-acetyl aspartate (NAA) concentrations by magnetic resonance spectroscopy (MRS) using cerebral water as an internal reference standard. Single-voxel, proton spectroscopy was carried out in two groups of rats (normal and diffuse head injury), using a PRESS sequence with TR = 3 s, TE = 135 ms. Fully relaxed water spectra and water-suppressed proton spectra were obtained from a 7 x 5 x 5 mm3 volume of tissue. MRI-based brain water content measurements were also performed. Following MRS, HPLC determinations of NAA were carried out. In the normal rats the MRS yielded 10.98 +/- 0.83 mmol/kg w.w. vs 10.76 +/- 0.76 for HPLC with a mean absolute difference of 0.8. In the injured rats the corresponding results were 9.41 +/- 1.78 (MRS) and 8.16 +/- 0.77 (HPLC) with a mean absolute difference of 1.66. The in vivo absolute method accurately documented the temporal NAA changes compared to the NAA/Cr approach.

The effects of dopamine on edema formation in two models of traumatic brain injury

The risk of vasopressors worsening cerebral edema has been raised. Previously we have reported that dopamine was able to restore cerebral blood flow in a model of monotonically rising intracranial pressure. In this study the effects of dopamine on cortical contusion and diffuse injury with secondary insult are examined. Adult male rats were divided into two groups: group 1 (n = 32)--Impact Acceleration Injury (IAM) with 30 minutes hypoxia and hypotension; group 2 (n = 12)--controlled cortical impact (6.0 m/sec, 3 mm depth). Dopamine was administered 2 hours post-injury (10-60 micrograms/kg/min i.v.). Cerebral water content and apparent diffusion coefficients (ADC) values were measured at baseline and four hours post-injury using MRI. Preinjury water content was the same in each group. Group 1 was subdivided into Groups 1A & 1B based on the ADC profile. Post-injury water content in Group 1A did not differ between saline or dopamine treated animals. Water content was higher in Group 1B-dopamine (83.4 +/- 1.1%) than Group 1B-saline animals (81.4 +/- 1.3%, p = 0.006). Contusion caused significant edema formation, however there was no significant difference between the dopamine treated or untreated group when considering either ipsilateral or contralateral cortex. Dopamine however significantly worsened edema in ipsilateral and contralateral hippocampus and both temporal cortices. ADC remained unchanged except in the contralateral hippocampus where both water content and ADC rose with dopamine suggesting precipitation of a vasogenic edema. In this study dopamine clearly worsened edema formation in two models of traumatic brain injury, and we conclude that there may be analogous clinical situations; therefore pressors should not be considered a 'blanket' therapy for all patients with a low cerebral perfusion pressure.

The effects of human corticotrophin releasing factor on motor and cognitive deficits after impact acceleration injury

Corticotrophin releasing factor has been shown in several models of tissue injury to be an effective treatment for edema. In a previous study we demonstrated this ability in two models of traumatic brain injury (TBI). The aim of this study was to assess whether human corticotrophin releasing factor (hCRF) could additionally improve motor and cognitive deficits. Adult male Sprague-Dawley rats were randomised into five groups and injured with the Impact Acceleration Model of TBI. Groups I and II received sham injury followed by treatment with either drug vehicle or 100 micrograms kg-1 hCRF respectively. Group III was injured with no treatment; Group IV animals were injured and treated with 50 micrograms kg-1 hCRF and Group V were injured and treated with 100 micrograms kg-1 hCRF. Animals were assessed both before and after injury with a battery of standardised neuropsychological tests including the Morris Water Maze, the Beam Walk Test, the Beam Balance Test and the Inclined Plane Test. Both 50 micrograms kg-1 and 100 micrograms kg-1 hCRF caused significant improvements in motor and cognitive functioning, confirming that in addition to edema-reducing properties, human corticotrophin releasing factor is also capable of improving motor and cognitive functioning. Given the beneficial experimental effects of this compound, hCRF may be a useful clinical treatment, which requires formal evaluation.

The pathogenesis of tumour associated epilepsy

Tumour associated epilepsy (TAE) is a poorly understood manifestation of many gliomas, meningiomas and metastatic brain tumours that has important clinical and social implications. Etiological mechanisms underlying tumour associated epilepsy include theories invoking peritumoural amino acid disturbances, local metabolic imbalances, cerebral oedema, pH abnormalities, morphological changes in the neuropil, changes in neuronal and glial enzyme and protein expression and altered immunological activity. It has also been suggested that the pathology involves perturbations in distribution and function of the NMDA subclass of glutamate receptors. The often capricious response of the seizure disorder following removal of the causative neoplasms suggests multiple factors are involved. Further understanding about the pathogenesis of TAE will await the development and characterisation of suitable animal models that demonstrate the clinical manifestations and physiological changes comparable to those seen in human cerebral tumours. With such a model it is hoped that progress may one day be made in understanding and subsequently treating this debilitating clinical problem.

The impact-acceleration model of head injury: injury severity predicts motor and cognitive performance after trauma

This study examines neuropsychological dysfunction after varying severities of the Impact Acceleration Model of diffuse traumatic brain injury. Adult rats (340 g-400 g) were divided into five groups, and exposed to varying degrees of Impact Acceleration Injury (1 m, 2 m, 2.1 m/500 g and second insult). After injury, animals were allowed to recover; acute neurological reflexes, beam walk score, beam balance score, inclined plane score, and Morris Water Maze score were then assessed at multiple time points. Injury of all severities caused significant motor and cognitive deficits. With milder injuries these effects were transient; however, with more severe injuries no recovery in function was seen. The addition of hypoxia and hypotension made a moderate injury worse than a severe injury. The acute neurological reflexes, the beam balance test and the inclined plane test distinguished between the more severely injured groups, but were affected less by mild injury. The beam walk test was sensitive to mild injury, but appeared unable to distinguish between the severe groups. The Morris Water Maze was sensitive for all injury groups, but appeared to adopt a different response profile with secondary insult. This study has for the first time characterized the degree of motor and cognitive deficits in rodents exposed to differing severities of Impact Acceleration Injury. These data confirm that the tests considered, and the Injury Model used, provide a useful system for the consideration of potential therapies which might ameliorate neuropsychological deficits in diffuse brain injury.

Treatment of raised intracranial pressure following traumatic brain injury

Appropriate treatment of raised intracranial pressure (ICP) after traumatic brain injury (TBI) remains a controversial topic in neurotraumatology. Several techniques are employed clinically, which include vasopressors, osmotically active substances, hyperventilation, and decompressive surgery. This article reviews six recent papers that have examined alternative methods of treating elevated ICP. The first two papers consider a new and controversial alternative to cerebral perfusion pressure (CPP) management, which involves mild hypotension coupled with pre-capillary vasoconstriction using dihydroergotamine. The authors claim success with this treatment, and although the patient numbers are small, there is no evidence that they fare any less well than patients treated with conventional techniques. The third and fourth papers consider hypertonic saline (HTS) as a possible osmotic treatment for raised ICP. The third examines HTS given as a 23.4% bolus and found beneficial effects. The fourth examines HTS as a 1.6% constant infusion for fluid replacement and found that patients fared less well. The reason for this difference between the results for the two administration methods is unknown, although it may relate to the triggering of body homeostatic mechanisms in the case of constant infusion. The fifth paper compares glycerol and mannitol as osmotic ICP agents and found no significant differences between them. The final study reports for the first time a series of patients treated for refractory elevations in ICP with bifrontal craniectomy. They report good results, and suggest that this therapy should be formalized as a treatment option for severely elevated ICP. The pathophysiological mechanisms underlying the generation of a raised ICP belie the use of one therapy to treat all cases. Analysis of these studies demonstrates how problematic heterogeneity in the injury population can be for the assessment of possible treatments. It is clear, therefore, that effective analysis of treatments for raised ICP requires appropriate subdivision of the injured population into common pathophysiological processes and, furthermore, that the future of clinical TBI management may well require a similar stratification in order to tailor treatments for the individual patient.

Neuroprotective effect of hypothermia on neuronal injury in diffuse traumatic brain injury coupled with hypoxia and hypotension

It is well established in mechanical head trauma that posttraumatic secondary insults, such as hypoxia and hypotension exacerbate neuronal injury and lead to worse outcome. In this study, the neuroprotective effect of hypothermia on the reduction of supraventricular subcortical neuronal damage was evaluated using an impact-acceleration model of diffuse traumatic brain injury coupled with both moderate and severe periods of hypoxia and hypotension. A total of 135 adult male Sprague-Dawley rats (340-375 g) were divided into three experimental studies: (I) physiological evaluation (n = 36); (II) quantitative analysis of the effect of trauma coupled with moderate and severe hypotension on neuronal damage assessed at 4 (n = 39) and 24 h (n = 24); and (III) the neuroprotective effect of hypothermia following moderate secondary insult (n = 36). Induction of hypothermia occurred at 15 min postinjury, to a level of 30 degrees C for 60 min. At the designated time points (4 and 24 h), the animals were sacrificed via standard transcardial perfusion techniques for histological processing. Quantitative assessment of neuronal damage using routine H&E staining at 4 hours showed neuronal damage which correlated with the severity of secondary insult. Animals exposed to trauma alone had a mean number of damaged neurons of 7.61 +/- 3.08/high powered field (hpf) compared with a mean of 1.21 +/- 0.30/hpf in the sham operated group (p = 0.015). Animals exposed to trauma with 10 min of hypoxia and hypotension (THH-10) showed a statistically significant number of damaged neurons compared to the sham-operated animals (7.50 +/- 2.15 damaged neurons/hpf, p = 0.013), whereas, neuronal damage in animals undergoing trauma with a 30-min secondary insult of hypoxia and hypotension (THH-30) was markedly increased (100 +/- 30.20/hpf, p = 0.002). Statistical analysis showed no significant difference in neuronal damage in animals subjected to secondary insult alone. At 24 h, the evolution of neuronal damage in the trauma alone group (5.08 +/- 1.63/hpf) was relatively static; however, there was a remarkable increase in the neuronal damage of the THH-10 group (29.88 50 +/- 8.20/hpf). However, hypothermia provided nearly complete protection against secondary insults, and neuronal damage was equal to that of the trauma alone group (p = 0.42). The results of this study confirm that hypothermia provides remarkable protection against the adverse effects of neuronal damage exacerbated by secondary injury. This study also presents a new model of secondary insult, which can be used experimentally to further define the mechanism of increased vulnerability of the injured brain.