A decrease in the neuroprotective effects of acute spinal cord decompression according to injury severity: introducing the concept of a ceiling effect.

OBJECTIVE: Acute traumatic spinal cord injury (tSCI) is followed by a prolonged period of secondary neuroglial cell death. Neuroprotective interventions, such as surgical spinal cord decompression, aim to mitigate secondary injury. In this study, the authors explore whether the effect size of posttraumatic neuroprotective spinal cord decompression varies with injury severity. METHODS: Seventy-one adult female Long Evans rats were subjected to a thoracic tSCI using a third-generation spinal contusion device. Moderate and severe tSCI were defined by recorded impact force delivered to the spinal cord. Immediately after injury (< 15 minutes), treatment cohorts underwent either a decompressive durotomy or myelotomy. Functional recovery was documented using the Basso, Beattie, and Bresnahan locomotor scale, and tissue sparing was documented using histological analysis. RESULTS: Moderate and severe injuries were separated at a cutoff point of 231.8 kdyn peak impact force based on locomotor recovery at 8 weeks after injury. Durotomy improved hindlimb locomotor recovery 8 weeks after moderate trauma (p < 0.01), but not after severe trauma (p > 0.05). Myelotomy led to increased tissue sparing (p < 0.0001) and a significantly higher number of spared motor neurons (p < 0.05) in moderate trauma, but no such effect was noted in severely injured rats (p > 0.05). Within the moderate injury group, myelotomy also resulted in significantly more spared tissue when compared with durotomy-only animals (p < 0.01). CONCLUSIONS: These results suggest that the neuroprotective effects of surgical spinal cord decompression decrease with increasing injury severity in a rodent tSCI model.

Early Detrusor Application of Botulinum Toxin A Results in Reduced Bladder Hypertrophy and Fibrosis after Spinal Cord Injury in a Rodent Model.

Following spinal cord injury (SCI), pathological reflexes develop that result in altered bladder function and sphincter dis-coordination, with accompanying changes in the detrusor. Bladder chemodenervation is known to ablate the pathological reflexes, but the resultant effects on the bladder tissue are poorly defined. In a rodent model of contusion SCI, we examined the effect of early bladder chemodenervation with botulinum toxin A (BoNT-A) on bladder histopathology and collagen deposition. Adult female Long Evans rats were given a severe contusion SCI at spinal level T9. The SCI rats immediately underwent open laparotomy and received detrusor injections of either BoNT-A (10 U/animal) or saline. At eight weeks post injury, the bladders were collected, weighed, and examined histologically. BoNT-A injected bladders of SCI rats (SCI + BoNT-A) weighed significantly less than saline injected bladders of SCI rats (SCI + saline) (241 ± 25 mg vs. 183 ± 42 mg; p < 0.05). Histological analyses showed that SCI resulted in significantly thicker bladder walls due to detrusor hypertrophy and fibrosis compared to bladders from uninjured animals (339 ± 89.0 µm vs. 193 ± 47.9 µm; p < 0.0001). SCI + BoNT-A animals had significantly thinner bladder walls compared to SCI + saline animals (202 ± 55.4 µm vs. 339 ± 89.0 µm; p < 0.0001). SCI + BoNT-A animals had collagen organization in the bladder walls similar to that of uninjured animals. Detrusor chemodenervation soon after SCI appears to preserve bladder tissue integrity by reducing the development of detrusor fibrosis and hypertrophy associated with SCI.

Blood Flow Changes Associated with Spinal Cord Injury Assessed by Non-linear Doppler Contrast-Enhanced Ultrasound.

Contrast-enhanced ultrasound (CEUS) is clinically used to image the microcirculation at lower imaging frequencies (<2 MHz). Recently, plane-wave acquisitions and Doppler processing have revealed improved microbubble sensitivity, enabling CEUS use at higher frequencies (15 MHz) and the ability to image simultaneously blood flow in the micro- and macrocirculations. We used this approach to assess acute and chronic blood flow changes within contused spinal cord in a rodent spinal cord injury model. Immediately after spinal cord injury, we found significant differences in perfusion deficit between moderate and severe injuries (1.73 ± 0.1 mm2 vs. 3.2 ± 0.3 mm2, respectively), as well as a delay in microbubble arrival time in tissue adjacent to the injury site (0.97 ± 0.1 s vs. 1.54 ± 0.1 s, respectively). Acutely, morphological changes to central sulcal arteries were observed where vessels rostral to the contusion were displaced 4.8 ± 2.2° and 8.2 ± 3.1° anteriorly, and vessels caudal to the contusion 17.8 ± 3.9° and 24.2 ± 4.1° posteriorly, respectively, for moderate and severe injuries. Significant correlation of the acute perfusion deficit and arrival time were found with the chronic assessment of locomotive function and histological estimate of spared spinal cord tissue.

Effect of Durotomy versus Myelotomy on Tissue Sparing and Functional Outcome after Spinal Cord Injury.

Various surgical strategies have been developed to alleviate elevated intraspinal pressure (ISP) following acute traumatic spinal cord injury (tSCI). Surgical decompression of either the dural (durotomy) or the dural and pial (myelotomy) lining of the spinal cord has been proposed. However, a direct comparison of these two strategies is lacking. Here, we compare the histological and functional effects of durotomy alone and durotomy plus myelotomy in a rodent model of acute thoracic tSCI. Our results indicate that tSCI causes local tissue edema and significantly elevates ISP (7.4 ± 0.3 mmHg) compared with physiological ISP (1.7 ± 0.4 mmHg; p < 0.001). Both durotomy alone and durotomy plus myelotomy effectively mitigate elevated local ISP (p < 0.001). Histological examination at 10 weeks after tSCI revealed that durotomy plus myelotomy promoted spinal tissue sparing by 13.7% compared with durotomy alone, and by 25.9% compared with tSCI-only (p < 0.0001). Both types of decompression surgeries elicited a significant beneficial impact on gray matter sparing (p < 0.01). Impressively, durotomy plus myelotomy surgery increased preservation of motor neurons by 174.3% compared with tSCI-only (p < 0.05). Durotomy plus myelotomy surgery also significantly promoted recovery of hindlimb locomotor function in an open-field test (p < 0.001). Interestingly, only durotomy alone resulted in favorable recovery of bladder and Ladder Walk performance. Combined, our data suggest that durotomy plus myelotomy following acute tSCI facilitates tissue sparing and recovery of locomotor function. In the future, biomarkers identifying spinal cord injuries that can benefit from either durotomy alone or durotomy plus myelotomy need to be developed.

Contrast-Enhanced Ultrasound for Assessment of Local Hemodynamic Changes Following a Rodent Contusion Spinal Cord Injury.

INTRODUCTION: Severe trauma to the spinal cord leads to a near complete loss of blood flow at the injury site along with significant hypoperfusion of adjacent tissues. Characterization and monitoring of local tissue hypoperfusion is currently not possible in clinical practice because available imaging techniques do not allow for assessment of blood flow with sufficient spatial and temporal resolutions. The objective of the current study was to determine whether ultrafast contrast-enhanced ultrasound (CEUS) imaging could be used to visualize and quantify acute hemodynamic changes in a rat traumatic spinal cord injury (SCI) model. MATERIALS AND METHODS: We used novel ultrasound acquisition and processing methods that allowed for measurements of local tissue perfusion as well as for assessment of structural and functional integrity of spinal vasculature. RESULTS: CEUS imaging showed that traumatic SCI results in (1) an area with significant loss of perfusion, which increased during the first hour after injury, (2) structural alterations of the spinal cord vasculature, and (3) significant slowing of arterial blood flow velocities around the injury epicenter. CONCLUSION: We conclude that CEUS has the spatial and temporal sensitivity and resolution to visualize local tissue perfusion and vessel architecture, which maybe useful clinically to determine injury extent and severity in patients with SCI.

Transcutaneous contrast-enhanced ultrasound imaging of the posttraumatic spinal cord.

STUDY DESIGN: Experimental animal study. OBJECTIVE: The current study aims to test whether the blood flow within the contused spinal cord can be assessed in a rodent model via the acoustic window of the laminectomy utilizing transcutaneous ultrasound. SETTING: Department of Neurological Surgery, University of Washington, Seattle WA. METHODS: Long-Evans rats (n = 12) were subjected to a traumatic thoracic spinal cord injury (SCI). Three days and 10 weeks after injury, animals underwent imaging of the contused spinal cord using ultrafast contrast-enhanced ultrasound with a Vantage ultrasound research system in combination with a 15 MHz transducer. Lesion size and signal-to-noise ratios were estimated via transcutaneous, subcutaneous, or epidural ultrasound acquisition through the acoustic window created by the original laminectomy. RESULTS: Following laminectomy, transcutaneous and subcutaneous contrast-enhanced ultrasound imaging allowed for assessment of perfusion and vascular flow in the contused rodent spinal cord. An average loss of 7.2 dB from transcutaneous to subcutaneous and the loss of 5.1 dB from subcutaneous to epidural imaging in signal-to-noise ratio (SNR) was observed. The hypoperfused injury center was measured transcutaneously, subcutaneously and epidurally (5.78 ± 0.86, 5.91 ± 0.53, 5.65 ± 1.07 mm2) at 3 days post injury. The same animals were reimaged again at 10 weeks following SCI, and the area of hypoperfusion had decreased significantly compared with the 3-day measurements detected via transcutaneous, subcutaneous, and epidural imaging respectively (0.69 ± 0.05, 1.09 ± 0.11, 0.95 ± 0.11 mm2, p < 0.001). CONCLUSIONS: Transcutaneous ultrasound allows for measurements and longitudinal monitoring of local hemodynamic changes in a rodent SCI model.

Contrast-enhanced ultrasound to visualize hemodynamic changes after rodent spinal cord injury.

OBJECTIVE Traumatic spinal cord injury (tSCI) causes an almost complete loss of blood flow at the site of injury (primary injury) as well as significant hypoperfusion in the penumbra of the injury. Hypoperfusion in the penumbra progresses after injury to the spinal cord and is likely to be a major contributor to progressive cell death of spinal cord tissue that was initially viable (secondary injury). Neuroprotective treatment strategies seek to limit secondary injury. Clinical monitoring of the temporal and spatial patterns of blood flow within the contused spinal cord is currently not feasible. The purpose of the current study was to determine whether ultrafast contrast-enhanced ultrasound (CEUS) Doppler allows for detection of local hemodynamic changes within an injured rodent spinal cord in real time. METHODS A novel ultrafast CEUS Doppler technique was developed utilizing a research ultrasound platform combined with a 15-MHz linear array transducer. Ultrafast plane-wave acquisitions enabled the separation of higher-velocity blood flow in macrocirculation from low-velocity flow within the microcirculation (tissue perfusion). An FDA-approved contrast agent (microbubbles) was used for visualization of local blood flow in real time. CEUS Doppler acquisition protocols were developed to characterize tissue perfusion both during contrast inflow and during the steady-state plateau. A compression injury of the thoracic spinal cord of adult rats was induced using iris forceps. RESULTS High-frequency ultrasound enabled visualization of spinal cord vessels such as anterior spinal arteries as well as central arteries (mean diameter [± SEM] 145.8 ± 10.0 µm; 76.2 ± 4.5 µm, respectively). In the intact spinal cord, ultrafast CEUS Doppler confirmed higher perfusion of the gray matter compared to white matter. Immediately after compression injury of the thoracic rodent spinal cord, spinal cord vessels were disrupted in an area of 1.93 ± 1.14 mm2. Ultrafast CEUS Doppler revealed a topographical map of local tissue hypoperfusion with remarkable spatial resolution. Critical loss of perfusion, defined as less than 40% perfusion compared to the surrounding spared tissue, was seen within an area of 2.21 ± 0.6 mm2. CONCLUSIONS In our current report, we introduce ultrafast CEUS Doppler for monitoring of spinal vascular structure and function in real time. Development and clinical implementation of this type of imaging could have a significant impact on the care of patients with tSCI.

Temporal and Spatial Evolution of Raised Intraspinal Pressure after Traumatic Spinal Cord Injury.

Traumatic spinal cord injury (SCI) often leads to permanent neurological impairment. Currently, the only clinically effective intervention for patients with acute SCI is surgical decompression by removal of impinging bone fragments within 24 h after injury. Recent clinical studies suggest that elevated intraparenchymal spinal pressure (ISP) limits functional recovery following SCI. Here, we report on the temporal and spatial patterns of elevated ISP following a moderate rodent contusion SCI. Compared with physiological ISP in the intact cord (2.7 ± 0.5 mm Hg), pressures increase threefold 30 min following injury (8.9 ± 1.1 mm Hg, p < 0.001) and remain elevated for up to 7 days (4.3 ± 0.8 mm Hg). Measurements of rostrocaudal ISP distribution reveal peak pressures in the injury center and in segments rostral to the injury during the acute phase(≤ 24 h). During the subacute phase(≥ 72 h), peak ISP decreases while a 7.5 mm long segment of moderately elevated ISP remains, centered on the initial contusion site. Interestingly, the contribution of the dural and pial compartments toward increased ISP changes with time after injury: Dural and pial linings contribute almost equally to increased ISP during the acute phase, whereas the dural lining is primarily responsible for elevated ISP during the subacute phase (78.9%). Our findings suggest that a rat contusion SCI model in combination with novel micro-catheters allows for direct measurement of ISP after SCI. Similarly to traumatic brain injury, raised tissue pressure is likely to have detrimental effects on spontaneous recovery following SCI.

Effects of lurasidone in behavioral models of depression. Role of the 5-HT7 receptor subtype.

Major depression is a common psychiatric disorder associated with high symptomatic and functional burdens. Pharmacological treatment is often effective, but there remain substantial unmet needs in the form of non-responders, delayed onset of clinical effect, and side effects. Recent studies have positioned the serotonin 5-HT7 receptor as a new target for the treatment of depression. Preclinical studies have shown that antagonists induce an antidepressant-like response, a phenotype that can also be observed in mice lacking the receptor. Lurasidone is a new atypical antipsychotic agent with very high affinity for the 5-HT7 receptor. Patients in clinical trials have reported improved scores in depression ratings. We have tested lurasidone in both acute and chronic mouse models of depression. In the tail suspension and forced swim tests lurasidone decreased immobility, an antidepressant-like response. The effect required functional 5-HT7 receptors as it was absent in mice lacking the receptor. In the repeated open-space swim test lurasidone was able to reverse the despair induced by repeated swims in a manner similar to the commonly used antidepressant citalopram. The results provide evidence that lurasidone can act as a 5-HT7 receptor antagonist and provide a possible explanation for the antidepressant effect data currently emerging from lurasidone clinical trials. Additionally, the results give further support for targeting the 5-HT7 receptor in the treatment of depression. It will be of interest to clinically evaluate lurasidone as an antidepressant either as monotherapy or as an adjunctive therapy to available drugs.