Lessons Learned in Building Expertly Annotated Multi-Institution Datasets and Hosting the RSNA AI Challenges

The Radiological Society of North America (RSNA) has held artificial intelligence competitions to tackle real-world medical imaging problems at least annually since 2017. This article examines the challenges and processes involved in organizing these competitions, with a specific emphasis on the creation and curation of high-quality datasets. The collection of diverse and representative medical imaging data involves dealing with issues of patient privacy and data security. Furthermore, ensuring quality and consistency in data, which includes expert labeling and accounting for various patient and imaging characteristics, necessitates substantial planning and resources. Overcoming these obstacles requires meticulous project management and adherence to strict timelines. The article also highlights the potential of crowdsourced annotation to progress medical imaging research. Through the RSNA competitions, an effective global engagement has been realized, resulting in innovative solutions to complex medical imaging problems, thus potentially transforming health care by enhancing diagnostic accuracy and patient outcomes. Keywords: Use of AI in Education, Artificial Intelligence © RSNA, 2024.

ATF3 is a neuron-specific biomarker for spinal cord injury and ischaemic stroke

BACKGROUND

Although many molecules have been investigated as biomarkers for spinal cord injury (SCI) or ischemic stroke, none of them are specifically induced in central nervous system (CNS) neurons following injuries with low baseline expression. However, neuronal injury constitutes a major pathology associated with SCI or stroke and strongly correlates with neurological outcomes. Biomarkers characterized by low baseline expression and specific induction in neurons post-injury are likely to better correlate with injury severity and recovery, demonstrating higher sensitivity and specificity for CNS injuries compared to non-neuronal markers or pan-neuronal markers with constitutive expressions.

METHODS

In animal studies, young adult wildtype and global Atf3 knockout mice underwent unilateral cervical 5 (C5) SCI or permanent distal middle cerebral artery occlusion (pMCAO). Gene expression was assessed using RNA-sequencing and qRT-PCR, while protein expression was detected through immunostaining. Serum ATF3 levels in animal models and clinical human samples were measured using commercially available enzyme-linked immune-sorbent assay (ELISA) kits.

RESULTS

Activating transcription factor 3 (ATF3), a molecular marker for injured dorsal root ganglion sensory neurons in the peripheral nervous system, was not expressed in spinal cord or cortex of naïve mice but was induced specifically in neurons of the spinal cord or cortex within 1 day after SCI or ischemic stroke, respectively. Additionally, ATF3 protein levels in mouse blood significantly increased 1 day after SCI or ischemic stroke. Importantly, ATF3 protein levels in human serum were elevated in clinical patients within 24 hours after SCI or ischemic stroke. Moreover, Atf3 knockout mice, compared to the wildtype mice, exhibited worse neurological outcomes and larger damage regions after SCI or ischemic stroke, indicating that ATF3 has a neuroprotective function.

CONCLUSIONS

ATF3 is an easily measurable, neuron-specific biomarker for clinical SCI and ischemic stroke, with neuroprotective properties.

HIGHLIGHTS

ATF3 was induced specifically in neurons of the spinal cord or cortex within 1 day after SCI or ischemic stroke, respectively. Serum ATF3 protein levels are elevated in clinical patients within 24 hours after SCI or ischemic stroke. ATF3 exhibits neuroprotective properties, as evidenced by the worse neurological outcomes and larger damage regions observed in Atf3 knockout mice compared to wildtype mice following SCI or ischemic stroke.

Diffusion Imaging of the Spinal Cord: Clinical Applications

Spinal cord pathologic condition often presents as a neurologic emergency where timely and accurate diagnosis is critical to expedite appropriate treatment and minimize severe morbidity and even mortality. MR imaging is the gold standard imaging technique for diagnosing patients with suspected spinal cord pathologic condition. This review will focus on the basic principles of diffusion imaging and how spinal anatomy presents technical challenges to its application. Both the promises and shortcomings of spinal diffusion imaging will then be explored in the context of several clinical spinal cord pathologies for which diffusion has been evaluated.

Safety and comparative efficacy of initiating low-molecular-weight heparin within 24 hours of injury or surgery for venous thromboembolism prophylaxis in patients with spinal cord injury: a prospective TRACK-SCI registry study

OBJECTIVE

Venous thromboembolism (VTE) following traumatic spinal cord injury (SCI) is a significant clinical concern. This study sought to determine the incidence of VTE and hemorrhagic complications among patients with SCI who received low-molecular-weight heparin (LMWH) within 24 hours of injury or surgery and identify variables that predict VTE using the prospective Transforming Research and Clinical Knowledge in SCI (TRACK-SCI) database.

METHODS

The TRACK-SCI database was queried for individuals with traumatic SCI from 2015 to 2022. Primary outcomes of interest included rates of VTE (including deep vein thrombosis [DVT] and pulmonary embolism [PE]) and in-hospital hemorrhagic complications that occurred after LWMH administration. Secondary outcomes included intensive care unit and hospital length of stay, discharge location type, and in-hospital mortality.

RESULTS

The study cohort consisted of 162 patients with SCI. Fifteen of the 162 patients withdrew from the study, leading to loss of data for certain variables for these patients. One hundred thirty patients (87.8%) underwent decompression and/or fusion surgery for SCI. DVT occurred in 11 (7.4%) of 148 patients, PE in 9 (6.1%) of 148, and any VTE in 18 (12.2%) of 148 patients. The analysis showed that admission lower-extremity motor score (p = 0.0408), injury at the thoracic level (p = 0.0086), admission American Spinal Injury Association grade (p = 0.0070), and younger age (p = 0.0372) were significantly associated with VTE. There were 3 instances of postoperative spine surgery-related bleeding (2.4%) in the 127 patients who had spine surgery with bleeding complication data available, with one requiring return to surgery (0.8%). Thirteen (8.8%) of 147 patients had a bleeding complication not related to spine surgery. There were 2 gastrointestinal bleeds associated with nasogastric tube placement, 3 cases of postoperative non-spine-related surgery bleeding, and 8 cases of other bleeding complications (5.4%) not related to any surgery.

CONCLUSIONS

Initiation of LMWH within 24 hours was associated with a low rate of spine surgery-related bleeding. Bleeding complications unrelated to SCI surgery still occur with LMWH administration. Because neurosurgical intervention is typically the limiting factor in initializing chemical DVT prophylaxis, many of these bleeding complications would have likely occurred regardless of the protocol.

Hypotension requiring vasopressor treatment and increased cardiac complications in elderly spinal cord injury patients: a prospective TRACK-SCI registry study

OBJECTIVE

Increasing life expectancy has led to an older population. In this study, the authors analyzed complications and outcomes in elderly patients following spinal cord injury (SCI) using the established multi-institutional prospective study Transforming Research and Clinical Knowledge in SCI (TRACK-SCI) database collected in the Department of Neurosurgical Surgery at the University of California, San Francisco.

METHODS

TRACK-SCI was queried for elderly individuals (≥ 65 years of age) with traumatic SCI from 2015 to 2019. Primary outcomes of interest included total hospital length of stay, perioperative complications, postoperative complications, and in-hospital mortality. Secondary outcomes included disposition location, and neurological improvement based on the American Spinal Injury Association Impairment Scale (AIS) grade at discharge. Descriptive analysis, Fisher's exact test, univariate analysis, and multivariable regression analysis were performed.

RESULTS

The study cohort consisted of 40 elderly patients. The in-hospital mortality rate was 10%. Every patient in this cohort experienced at least 1 complication, with a mean of 6.6 separate complications (median 6, mode 4). The most common complication categories were cardiovascular, with a mean of 1.6 complications (median 1, mode 1), and pulmonary, with a mean of 1.3 (median 1, mode 0) complications, with 35 patients (87.5%) having at least 1 cardiovascular complication and 25 (62.5%) having at least 1 pulmonary complication. Overall, 32 patients (80%) required vasopressor treatment for mean arterial pressure (MAP) maintenance goals. The use of norepinephrine correlated with increased cardiovascular complications. Only 3 patients (7.5%) of the total cohort had an improved AIS grade compared with their acute level at admission.

CONCLUSIONS

Given the increased frequency of cardiovascular complications associated with vasopressor use in elderly SCI patients, caution is warranted when targeting MAP goals in these patients. A downward adjustment of blood pressure maintenance goals and prophylactic cardiology consultation to select the most appropriate vasopressor agent may be advisable for SCI patients ≥ 65 years of age.

Parieto-Occipital Injury on Diffusion MRI Correlates with Poor Neurologic Outcome following Cardiac Arrest

BACKGROUND AND PURPOSE

MR imaging of the brain provides unbiased neuroanatomic evaluation of brain injury and is useful for neurologic prognostication following cardiac arrest. Regional analysis of diffusion imaging may provide additional prognostic value and help reveal the neuroanatomic underpinnings of coma recovery. The purpose of this study was to evaluate global, regional, and voxelwise differences in diffusion-weighted MR imaging signal in patients in a coma after cardiac arrest.

MATERIALS AND METHODS

We retrospectively analyzed diffusion MR imaging data from 81 subjects who were comatose for >48 hours following cardiac arrest. Poor outcome was defined as the inability to follow simple commands at any point during hospitalization. ADC differences between groups were evaluated across the whole brain, locally by using voxelwise analysis and regionally by using ROI-based principal component analysis.

RESULTS

Subjects with poor outcome had more severe brain injury as measured by lower average whole-brain ADC (740 [SD, 102] × 10-6 mm2/s versus 833 [SD, 23] × 10-6 mm2/s, P < .001) and larger average volumes of tissue with ADC below 650 × 10-6 mms/s (464 [SD, 469] mL versus 62 [SD, 51] mL, P < .001). Voxelwise analysis showed lower ADC in the bilateral parieto-occipital areas and perirolandic cortices for the poor outcome group. ROI-based principal component analysis showed an association between lower ADC in parieto-occipital regions and poor outcome.

CONCLUSIONS

Brain injury affecting the parieto-occipital region measured with quantitative ADC analysis was associated with poor outcomes after cardiac arrest. These results suggest that injury to specific brain regions may influence coma recovery.

Spinal epidural arteriovenous fistula with nerve root enhancement mimicking myeloradiculitis: a case report

BACKGROUND

Gadolinium enhancement of spinal nerve roots on magnetic resonance imaging (MRI) has rarely been reported in spinal dural arteriovenous fistula (SDAVF). Nerve root enhancement and cerebrospinal fluid (CSF) pleocytosis can be deceptive and lead to a misdiagnosis of myeloradiculitis. We report a patient who was initially diagnosed with neurosarcoid myeloradiculitis due to spinal nerve root enhancement, mildly inflammatory cerebrospinal fluid, and pulmonary granulomas, who ultimately was found to have an extensive symptomatic SDAVF.

CASE PRESENTATION

A 52-year-old woman presented with a longitudinally extensive spinal cord lesion with associated gadolinium enhancement of the cord and cauda equina nerve roots, and mild lymphocytic pleocytosis. Pulmonary lymph node biopsy revealed non-caseating granulomas and neurosarcoid myeloradiculitis was suspected. She had rapid and profound clinical deterioration after a single dose of steroids. Further work-up with spinal angiography revealed a thoracic SDAVF, which was surgically ligated leading to clinical improvement.

CONCLUSIONS

This case highlights an unexpected presentation of SDAVF with nerve root enhancement and concurrent pulmonary non-caseating granulomas, leading to an initial misdiagnosis with neurosarcoidosis. Nerve root enhancement has only rarely been described in cases of SDAVF; however, as this case highlights, it is an important consideration in the differential diagnosis of non-inflammatory causes of longitudinally extensive myeloradiculopathy with nerve root enhancement. This point is highly salient due to the importance of avoiding misdiagnosis of SDAVF, as interventions such as steroids or epidural injections used to treat inflammatory or infiltrative mimics may worsen symptoms in SDAVF. We review the presentation, diagnosis, and management of SDAVF as well as a proposed diagnostic approach to differentiating SDAVF from inflammatory myeloradiculitis.

Decision tree–based machine learning analysis of intraoperative vasopressor use to optimize neurological improvement in acute spinal cord injury

OBJECTIVE

Previous work has shown that maintaining mean arterial pressures (MAPs) between 76 and 104 mm Hg intraoperatively is associated with improved neurological function at discharge in patients with acute spinal cord injury (SCI). However, whether temporary fluctuations in MAPs outside of this range can be tolerated without impairment of recovery is unknown. This retrospective study builds on previous work by implementing machine learning to derive clinically actionable thresholds for intraoperative MAP management guided by neurological outcomes.

METHODS

Seventy-four surgically treated patients were retrospectively analyzed as part of a longitudinal study assessing outcomes following SCI. Each patient underwent intraoperative hemodynamic monitoring with recordings at 5-minute intervals for a cumulative 28,594 minutes, resulting in 5718 unique data points for each parameter. The type of vasopressor used, dose, drug-related complications, average intraoperative MAP, and time spent in an extreme MAP range (< 76 mm Hg or > 104 mm Hg) were collected. Outcomes were evaluated by measuring the change in American Spinal Injury Association Impairment Scale (AIS) grade over the course of acute hospitalization. Features most predictive of an improvement in AIS grade were determined statistically by generating random forests with 10,000 iterations. Recursive partitioning was used to establish clinically intuitive thresholds for the top features.

RESULTS

At discharge, a significant improvement in AIS grade was noted by an average of 0.71 levels (p = 0.002). The hemodynamic parameters most important in predicting improvement were the amount of time intraoperative MAPs were in extreme ranges and the average intraoperative MAP. Patients with average intraoperative MAPs between 80 and 96 mm Hg throughout surgery had improved AIS grades at discharge. All patients with average intraoperative MAP > 96.3 mm Hg had no improvement. A threshold of 93 minutes spent in an extreme MAP range was identified after which the chance of neurological improvement significantly declined. Finally, the use of dopamine as compared to norepinephrine was associated with higher rates of significant cardiovascular complications (50% vs 25%, p < 0.001).

CONCLUSIONS

An average intraoperative MAP value between 80 and 96 mm Hg was associated with improved outcome, corroborating previous results and supporting the clinical verifiability of the model. Additionally, an accumulated time of 93 minutes or longer outside of the MAP range of 76–104 mm Hg is associated with worse neurological function at discharge among patients undergoing emergency surgical intervention for acute SCI.

Topological network analysis of patient similarity for precision management of acute blood pressure in spinal cord injury

Background:

Predicting neurological recovery after spinal cord injury (SCI) is challenging. Using topological data analysis, we have previously shown that mean arterial pressure (MAP) during SCI surgery predicts long-term functional recovery in rodent models, motivating the present multicenter study in patients.

Methods:

Intra-operative monitoring records and neurological outcome data were extracted (n = 118 patients). We built a similarity network of patients from a low-dimensional space embedded using a non-linear algorithm, Isomap, and ensured topological extraction using persistent homology metrics. Confirmatory analysis was conducted through regression methods.

Results:

Network analysis suggested that time outside of an optimum MAP range (hypotension or hypertension) during surgery was associated with lower likelihood of neurological recovery at hospital discharge. Logistic and LASSO (least absolute shrinkage and selection operator) regression confirmed these findings, revealing an optimal MAP range of 76–[104-117] mmHg associated with neurological recovery.

Conclusions:

We show that deviation from this optimal MAP range during SCI surgery predicts lower probability of neurological recovery and suggest new targets for therapeutic intervention.

Funding:

NIH/NINDS: R01NS088475 (ARF); R01NS122888 (ARF); UH3NS106899 (ARF); Department of Veterans Affairs: 1I01RX002245 (ARF), I01RX002787 (ARF); Wings for Life Foundation (ATE, ARF); Craig H. Neilsen Foundation (ARF); and DOD: SC150198 (MSB); SC190233 (MSB); DOE: DE-AC02-05CH11231 (DM).

Spinal cord injury is a devastating condition that involves damage to the nerve fibers connecting the brain with the spinal cord, often leading to permanent changes in strength, sensation and body functions, and in severe cases paralysis. Scientists around the world work hard to find ways to treat or even repair spinal cord injuries but few patients with complete immediate paralysis recover fully.

Immediate paralysis is caused by direct damage to neurons and their extension in the spinal cord. Previous research has shown that blood pressure regulation may be key in saving these damaged neurons, as spinal cord injuries can break the communication between nerves that is involved in controlling blood pressure. This can lead to a vicious cycle of dysregulation of blood pressure and limit the supply of blood and oxygen to the damaged spinal cord tissue, exacerbating the death of spinal neurons. Management of blood pressure is therefore a key target for spinal cord injury care, but so far, the precise thresholds to enable neurons to recover are poorly understood.

To find out more, Torres-Espin, Haefeli et al. used machine learning software to analyze previously recorded blood pressure and heart rate data obtained from 118 patients that underwent spinal cord surgery after acute spinal cord injury.

The analyses revealed that patients who suffered from either low or high blood pressure during surgery had poorer prospects of recovery. Statistical models confirming these findings showed that the optimal blood pressure range to ensure recovery lies between 76 to 104-117 mmHg. Any deviation from this narrow window would dramatically worsen the ability to recover.

These findings suggests that dysregulated blood pressure during surgery affects to odds of recovery in patients with a spinal cord injury. Torres-Espin, Haefeli et al. provide specific information that could improve current clinical practice in trauma centers. In the future, such machine learning tools and models could help develop real-time models that could predict the likelihood of a patient’s recovery following spinal cord injury and related neurological conditions.

Investigating the Feasibility of In Vivo Perfusion Imaging Methods for Spinal Cord Using Hyperpolarized [13C]t-Butanol and [13C,15N2]Urea

PURPOSE

This study examined the feasibility of using two novel agents, hyperpolarized [¹³C]t-butanol and [¹³C,¹⁵N₂]urea, for assessing in vivo perfusion of the intact spinal cord in rodents. Due to their distinct permeabilities to blood brain barrier (BBB), we hypothesized that [¹³C]t-butanol and [¹³C,¹⁵N₂]urea exhibit unique ¹³C signal characteristics in the spinal cord.

PROCEDURES

Dynamic ¹³C t-butanol MRI data were acquired from healthy Long-Evans rats using a symmetric, ramp-sampled, partial-Fourier ¹³C echo-planar imaging sequence after the injection of hyperpolarized [¹³C]t-butanol solution. In subsequent scans, dynamic ¹³C urea MRI data were acquired after the injection of hyperpolarized [¹³C,¹⁵N₂]urea. The SNRs of t-butanol and urea were calculated for regions corresponding to spine, supratentorial brain, and blood vessels and plotted over time. Mean peak SNR and AUC were calculated from the dynamic plots for each region and compared between t-butanol and urea.

RESULTS

In spine and supratentorial brain, the mean peak SNR and AUC of t-butanol were significantly higher than those of urea (p < 0.05). In contrast, urea was predominantly contained within vasculature and exhibited significantly higher levels of mean peak SNR and AUC compared to t-butanol in blood vessels (p < 0.05).

CONCLUSION

This study has demonstrated the feasibility of using hyperpolarized [¹³C]t-butanol and [¹³C,¹⁵N₂]urea for assessing in vivo perfusion in cervical spinal cord. Due to differences in blood-brain barrier permeability, t-butanol rapidly crossed the blood-brain barrier and diffused into spine and brain tissue, while urea predominantly remained in vasculature. The results from this study suggest that this technique may provide unique non-invasive imaging tracers that are able to directly monitor hemodynamic processes in the normal and injured spinal cord.

Single versus dual operative spine fractures in ankylosing spondylitis

OBJECTIVE

Ankylosing spondylitis, the most common spondyloarthritis, fuses individual spinal vertebrae into long segments. The unique biomechanics of the ankylosed spine places patients at unusually high risk for unstable fractures secondary to low-impact mechanisms. These injuries are unique within the spine trauma population and necessitate thoughtful management. Therefore, the authors aimed to present a richly annotated data set of operative AS spine fractures with a significant portion of patients with simultaneous dual noncontiguous fractures.

METHODS

Patients with ankylosing spondylitis with acute fractures who received operative management between 2012 and 2020 were reviewed. Demographic, admission, surgical, and outcome parameters were retrospectively collected and reviewed.

RESULTS

In total, 29 patients were identified across 30 different admissions. At admission, the mean age was 71.7 ± 11.8 years. The mechanism of injury in 77% of the admissions was a ground-level fall; 30% also presented with polytrauma. Of admissions, 50% were patient transfers from outside hospitals, whereas the other half presented primarily to our emergency departments. Fifty percent of patients sustained a spinal cord injury, and 35 operative fractures were identified and treated in 32 surgeries. The majority of fractures clustered around the cervicothoracic (C4-T1, 48.6%) and thoracolumbar (T8-L3, 37.11%) junctions. Five patients (17.2%) had simultaneous dual noncontiguous operative fractures; these patients were more likely to have presented with a higher-energy mechanism of injury such as a bicycle or motor vehicle accident compared with patients with a single operative fracture (60% vs 8%, p = 0.024). On preoperative MRI, 56.3% of the fractures had epidural hematomas (EDHs); 25% were compressive of the underlying neural elements, which dictated the number of laminectomy levels performed (no EDH, 2.1 ± 2.36; noncompressive EDH, 2.1 ± 1.85; and compressive EDH, 7.4 ± 4 [p = 0.003]). The mean difference in instrumented levels was 8.7 ± 2.6 with a mean estimated blood loss (EBL) of 1183 ± 1779.5 mL. Patients on a regimen of antiplatelet therapy had a significantly higher EBL (2635.7 mL vs 759.4 mL, p = 0.015). Overall, patients had a mean hospital length of stay of 15.2 ± 18.5 days; 5 patients died during the same admission or after transfer to an outside hospital. Nine of 29 patients (31%) had died by the last follow-up (the mean follow-up was 596.3 ± 878.9 days).

CONCLUSIONS

Patients with AS who have been found to have unstable spine fractures warrant a thorough diagnostic evaluation to identify secondary fractures as well as compressive EDHs. These patients experienced prolonged inpatient hospitalizations with significant morbidity and mortality.

Transforming Research and Clinical Knowledge in Spinal Cord Injury (TRACK-SCI): an overview of initial enrollment and demographics

OBJECTIVE

Traumatic spinal cord injury (SCI) is a dreaded condition that can lead to paralysis and severe disability. With few treatment options available for patients who have suffered from SCI, it is important to develop prospective databases to standardize data collection in order to develop new therapeutic approaches and guidelines. Here, the authors present an overview of their multicenter, prospective, observational patient registry, Transforming Research and Clinical Knowledge in SCI (TRACK-SCI).

METHODS

Data were collected using the National Institute of Neurological Disorders and Stroke (NINDS) common data elements (CDEs). Highly granular clinical information, in addition to standardized imaging, biospecimen, and follow-up data, were included in the registry. Surgical approaches were determined by the surgeon treating each patient; however, they were carefully documented and compared within and across study sites. Follow-up visits were scheduled for 6 and 12 months after injury.

RESULTS

One hundred sixty patients were enrolled in the TRACK-SCI study. In this overview, basic clinical, imaging, neurological severity, and follow-up data on these patients are presented. Overall, 78.8% of the patients were determined to be surgical candidates and underwent spinal decompression and/or stabilization. Follow-up rates to date at 6 and 12 months are 45% and 36.3%, respectively. Overall resources required for clinical research coordination are also discussed.

CONCLUSIONS

The authors established the feasibility of SCI CDE implementation in a multicenter, prospective observational study. Through the application of standardized SCI CDEs and expansion of future multicenter collaborations, they hope to advance SCI research and improve treatment.

Diagnostic blood RNA profiles for human acute spinal cord injury

Diagnosis of spinal cord injury (SCI) severity at the ultra-acute stage is of great importance for emergency clinical care of patients as well as for potential enrollment into clinical trials. The lack of a diagnostic biomarker for SCI has played a major role in the poor results of clinical trials. We analyzed global gene expression in peripheral white blood cells during the acute injury phase and identified 197 genes whose expression changed after SCI compared with healthy and trauma controls and in direct relation to SCI severity. Unsupervised coexpression network analysis identified several gene modules that predicted injury severity (AIS grades) with an overall accuracy of 72.7% and included signatures of immune cell subtypes. Specifically, for complete SCIs (AIS A), ROC analysis showed impressive specificity and sensitivity (AUC: 0.865). Similar precision was also shown for AIS D SCIs (AUC: 0.938). Our findings indicate that global transcriptomic changes in peripheral blood cells have diagnostic and potentially prognostic value for SCI severity.

Injury volume extracted from MRI predicts neurologic outcome in acute spinal cord injury: A prospective TRACK-SCI pilot study

Conventional MRI measures of traumatic spinal cord injury severity largely rely on 2-dimensional injury characteristics such as intramedullary lesion length and cord compression. Recent advances in spinal cord (SC) analysis have led to the development of a robust anatomic atlas incorporated into an open-source platform called the Spinal Cord Toolbox (SCT) that allows for quantitative volumetric injury analysis. In the current study, we evaluate the prognostic value of volumetric measures of spinal cord injury on MRI following registration of T2-weighted (T2w) images and segmented lesions from acute SCI patients with a standardized atlas. This IRB-approved prospective cohort study involved the image analysis of 60 blunt cervical SCI patients enrolled in the TRACK-SCI clinical research protocol. Axial T2w MRI data obtained within 24 h of injury were processed using the SCT. Briefly, SC MRIs were automatically segmented using the sct_deepseg_sc tool in the SCT and segmentations were manually corrected by a neuro-radiologist. Lesion volume data were used as predictor variables for correlation with lower extremity motor scores at discharge. Volumetric MRI measures of T2w signal abnormality comprising the SCI lesion accurately predict lower extremity motor scores at time of patient discharge. Similarly, MRI measures of injury volume significantly correlated with motor scores to a greater degree than conventional 2-D metrics of lesion size. The volume of total injury and of injured spinal cord motor regions on T2w MRI is significantly and independently associated with neurologic outcome at discharge after injury.

Value of aggressive surgical and intensive care unit in elderly patients with traumatic spinal cord injury

OBJECTIVEThe elderly are a growing subpopulation within traumatic spinal cord injury (SCI) patients. Studies have reported high morbidity and mortality rates in elderly patients who undergo surgery for SCI. In this study, the authors compare the perioperative outcomes of surgically managed elderly SCI patients with those of a younger cohort and those reported in the literature.METHODSData on a consecutive series of adult traumatic SCI patients surgically managed at a single institution in the period from 2007 to 2017 were retrospectively reviewed. The cohort was divided into two groups based on age: younger than 70 years and 70 years or older. Assessed outcomes included complications, in-hospital mortality, intensive care unit (ICU) stay, hospital length of stay (LOS), disposition, and neurological status.RESULTSA total of 106 patients were included in the study: 83 young and 23 elderly. The two groups were similar in terms of imaging features (cord hemorrhage and fracture), operative technique, and American Spinal Injury Association Impairment Scale (AIS) grade. The elderly had a significantly higher proportion of cervical SCIs (95.7% vs 71.1%, p = 0.047). There were no significant differences between the young and the elderly in terms of the ICU stay (13.1 vs 13.3 days, respectively, p = 0.948) and hospital LOS (23.3 vs 21.7 days, p = 0.793). Elderly patients experienced significantly higher complication (73.9% vs 43.4%, p = 0.010) and mortality (13.0% vs 1.2%, p = 0.008) rates; in other words, the elderly patients had 1.7 times and 10.8 times the rate of complications and mortality, respectively, than the younger patients. No elderly patients were discharged home (0.0% vs 18.1%, p = 0.029). Discharge AIS grade and AIS grade change were similar between the groups.CONCLUSIONSElderly patients had higher complication and mortality rates than those in younger patients and were less likely to be discharged home. However, it does seem that mortality rates have improved compared to those in prior historical reports.

Clinical Implementation of Novel Spinal Cord Perfusion Pressure Protocol in Acute Traumatic Spinal Cord Injury at U.S. Level I Trauma Center: TRACK-SCI Study

OBJECTIVE

We sought to report the safety of implementation of a novel standard of care protocol using spinal cord perfusion pressure (SCPP) maintenance for managing traumatic spinal cord injury (SCI) in lieu of mean arterial pressure goals at a U.S. Level I trauma center.

METHODS

Starting in December 2017, blunt SCI patients presenting <24 hours after injury with admission American Spinal Injury Association Impairment Scale (AIS) A-C (or AIS D at neurosurgeon discretion) received lumbar subarachnoid drain (LSAD) placement for SCPP monitoring in the intensive care unit and were included in the TRACK-SCI (Transforming Research and Clinical Knowledge in Spinal Cord Injury) data registry. This SCPP protocol comprises standard care at our institution. SCPPs were monitored for 5 days (goal ≥65 mm Hg) achieved through intravenous fluids and vasopressor support. AISs were assessed at admission and day 7.

RESULTS

Fifteen patients enrolled to date were aged 60.5 ± 17 years. Injury levels were 93.3% (cervical) and 6.7% (thoracic). Admission AIS was 20.0%/20.0%/26.7%/33.3% for A/B/C/D. All patients maintained mean SCPP ≥65 mm Hg during monitoring. Fourteen of 15 cases required surgical decompression and stabilization with time to surgery 8.8 ± 7.1 hours (71.4% <12 hours). At day 7, 33.3% overall and 50% of initial AIS A-C had an improved AIS. Length of stay was 14.7 ± 8.3 days. None had LSAD-related complications. There were 7 respiratory complications. One patient expired after transfer to comfort care.

CONCLUSIONS

In our initial experience of 15 patients with acute SCI, standardized SCPP goal-directed care based on LSAD monitoring for 5 days was feasible. There were no SCPP-related complications. This is the first report of SCPP implementation as clinical standard of care in acute SCI.

Motor Evoked Potentials Correlate With Magnetic Resonance Imaging and Early Recovery After Acute Spinal Cord Injury

BACKGROUND

While the utilization of neurophysiologic intraoperative monitoring with motor evoked potentials (MEPs) has become widespread in surgery for traumatic spine fractures and spinal cord injury (SCI), clinical validation of its diagnostic and therapeutic benefit has been limited.

OBJECTIVE

To describe the use of intraoperative MEP at a large level I trauma center and assess the prognostic capability of this technology.

METHODS

The SCI REDCap database at our institution, a level I trauma center, was queried for acute cervical SCI patients who underwent surgery with intraoperative monitoring between 2005 and 2011, yielding 32 patients. Of these, 23 patients had severe SCI (association impairment scale [AIS] A, B, C). We assessed preoperative and postoperative SCI severity (AIS grade), surgical data, use of steroids, and early magnetic resonance imaging (MRI) findings (preoperatively in 27 patients), including axial T2 MRI grade (Brain and Spinal Injury Center score).

RESULTS

The presence of MEPs significantly predicted AIS at discharge (P< .001). In the group of severe SCI (ie, AIS A, B, C) patients with elicitable MEPs, AIS improved by an average of 1.5 grades (median = 1), as compared to the patients without elicitable MEP who improved on average 0.5 grades (median = 0, P< .05). In addition, axial MRI grade significantly correlated with MEP status. Patients without MEPs had a significantly higher axial MRI grade in comparison to the patients with MEPs (P< .001).

CONCLUSION

In patients with severe SCI, MEPs predicted neurological improvement and correlated with axial MRI grade. These significant findings warrant future prospective studies of MEPs as a prognostic tool in SCI.

Quantitative [18F]-Naf-PET-MRI Analysis for the Evaluation of Dynamic Bone Turnover in a Patient with Facetogenic Low Back Pain

Imaging techniques that reflect dynamic bone turnover may aid in characterizing a wide range of bone pathologies. Bone is a dynamic tissue undergoing continuous remodeling with the competing activity of osteoblasts, which produce the new bone matrix, and osteoclasts, whose function is to eliminate mineralized bone. [¹⁸F]-NaF is a positron emission tomography (PET) radiotracer that enables visualization of bone metabolism. [¹⁸F]-NaF is chemically absorbed into hydroxyapatite in the bone matrix by osteoblasts and can thus noninvasively detect osteoblastic activity, which is occult to conventional imaging techniques. Kinetic modeling of dynamic [¹⁸F]-NaF-PET data provides detailed quantitative measures of bone metabolism. Conventional semi-quantitative PET data, which utilizes standardized uptake values (SUVs) as a measure of radiotracer activity, is referred to as a static technique due to its snapshot of tracer uptake in time.  Kinetic modeling, however, utilizes dynamic image data where tracer levels are continuously acquired providing tracer uptake temporal resolution. From the kinetic modeling of dynamic data, quantitative values like blood flow and metabolic rate (i.e., potentially informative metrics of tracer dynamics) can be extracted, all with respect to the measured activity in the image data. When combined with dual modality PET-MRI, region-specific kinetic data can be correlated with anatomically registered high-resolution structural and pathologic information afforded by MRI. The goal of this methodological manuscript is to outline detailed techniques for performing and analyzing dynamic [¹⁸F]-NaF-PET-MRI data. The lumbar facet joint is a common site of degenerative arthritis disease and a common cause for axial low back pain.  Recent studies suggest [¹⁸F]-NaF-PET may serve as a useful biomarker of painful facetogenic disease.  The human lumbar facet joint will, therefore, be used as a prototypical region of interest for dynamic [¹⁸F]-NaF-PET-MRI analysis in this manuscript.

CT-Guided Block and Radiofrequency Ablation of the C2 Dorsal Root Ganglion for Cervicogenic Headache

The purpose of this report is to describe the technical aspects of CT-guided C2 dorsal root ganglion diagnostic block and radiofrequency ablation for refractory cervicogenic headache. CT guidance allows precise and safe positioning of a needle adjacent to the C2 dorsal root ganglion. At-risk neural and vascular structures can be avoided with CT, and it can provide a thorough understanding of upper cervical neuroanatomy.

Convolutional Neural Network-Based Automated Segmentation of the Spinal Cord and Contusion Injury: Deep Learning Biomarker Correlates of Motor Impairment in Acute Spinal Cord Injury

BACKGROUND AND PURPOSE

Our aim was to use 2D convolutional neural networks for automatic segmentation of the spinal cord and traumatic contusion injury from axial T2-weighted MR imaging in a cohort of patients with acute spinal cord injury.

MATERIALS AND METHODS

Forty-seven patients who underwent 3T MR imaging within 24 hours of spinal cord injury were included. We developed an image-analysis pipeline integrating 2D convolutional neural networks for whole spinal cord and intramedullary spinal cord lesion segmentation. Linear mixed modeling was used to compare test segmentation results between our spinal cord injury convolutional neural network (Brain and Spinal Cord Injury Center segmentation) and current state-of-the-art methods. Volumes of segmented lesions were then used in a linear regression analysis to determine associations with motor scores.

RESULTS

Compared with manual labeling, the average test set Dice coefficient for the Brain and Spinal Cord Injury Center segmentation model was 0.93 for spinal cord segmentation versus 0.80 for PropSeg and 0.90 for DeepSeg (both components of the Spinal Cord Toolbox). Linear mixed modeling showed a significant difference between Brain and Spinal Cord Injury Center segmentation compared with PropSeg (P < .001) and DeepSeg (P < .05). Brain and Spinal Cord Injury Center segmentation showed significantly better adaptability to damaged areas compared with PropSeg (P < .001) and DeepSeg (P < .02). The contusion injury volumes based on automated segmentation were significantly associated with motor scores at admission (P = .002) and discharge (P = .009).

CONCLUSIONS

Brain and Spinal Cord Injury Center segmentation of the spinal cord compares favorably with available segmentation tools in a population with acute spinal cord injury. Volumes of injury derived from automated lesion segmentation with Brain and Spinal Cord Injury Center segmentation correlate with measures of motor impairment in the acute phase. Targeted convolutional neural network training in acute spinal cord injury enhances algorithm performance for this patient population and provides clinically relevant metrics of cord injury.

Ultra-Early (<12 Hours) Surgery Correlates With Higher Rate of American Spinal Injury Association Impairment Scale Conversion After Cervical Spinal Cord Injury

BACKGROUND

Cervical spinal cord injury (SCI) is a devastating condition with very few treatment options. It remains unclear if early surgery correlated with conversion of American Spinal Injury Association Impairment Scale (AIS) grade A injuries to higher grades.

OBJECTIVE

To determine the optimal time to surgery after cervical SCI through retrospective analysis.

METHODS

We collected data from 48 patients with cervical SCI. Based on the time from Emergency Department (ED) presentation to surgical decompression, we grouped patients into ultra-early (decompression within 12 h of presentation), early (within 12-24 h), and late groups (&gt;24 h). We compared the improvement in AIS grade from admission to discharge, controlling for confounding factors such as AIS grade on admission, injury severity, and age. The mean time from injury to ED for this group of patients was 17 min.

RESULTS

Patients who received surgery within 12 h after presentation had a relative improvement in AIS grade from admission to discharge: the ultra-early group improved on average 1.3. AIS grades compared to 0.5 in the early group (P = .02). In addition, 88.8% of patients with an AIS grade A converted to a higher grade (AIS B or better) in the ultra-early group, compared to 38.4% in the early and late groups (P = .054).

CONCLUSION

These data suggest that surgical decompression after SCI that takes place within 12 h may lead to a relative improved neurological recovery compared to surgery that takes place after 12 h.

Accuracy of image-guided percutaneous injection into a phantom spinal cord utilizing flat panel detector CT with MR fusion and integrated navigational software

PURPOSE

To evaluate the accuracy of percutaneous fluoroscopic injection into the spinal cord of a spine phantom utilizing integrated navigational guidance from fused flat panel detector CT (FDCT) and MR datasets. Conventional and convection-enhanced delivery (CED) techniques were evaluated.

MATERIALS AND METHODS

FDCT and MR datasets of a swine thoracic spine phantom were co-registered using an integrated guidance system and surface to spinal cord target trajectory planning was performed on the fused images. Under real-time fluoroscopic guidance with pre-planned trajectory overlay, spinal cord targets were accessed via a coaxial technique. Final needle tip position was compared with a pre-determined target on 10 independent passes. In a subset of cases, contrast was injected into the central spinal cord with a 25G spinal needle or customized 200 µm inner diameter step design cannula for CED.

RESULTS

Average needle tip deviation from target measured 0.92±0.5 mm in the transverse, 0.47±0.4 mm in the anterior-posterior, and 1.67±1.2 mm in the craniocaudal dimension for an absolute distance error of 2.12±1.12 mm. CED resulted in elliptical intramedullary diffusion of contrast compared with primary reflux observed with standard needle injection.

CONCLUSIONS

These phantom feasibility data demonstrate a minimally invasive percutaneous approach for targeted injection into the spinal cord utilizing real-time fluoroscopy aided by overlay trajectories derived from fused MRI and FDCT data sets with a target error of 2.1 mm. Intramedullary diffusion of injectate in the spinal cord is facilitated with CED compared with standard injection technique. Pre-clinical studies in large animal models are warranted.

Utility of Repeat Head CT in Patients with Blunt Traumatic Brain Injury Presenting with Small Isolated Falcine or Tentorial Subdural Hematomas

BACKGROUND AND PURPOSE

In blunt traumatic brain injury with isolated falcotentorial subdural hematoma not amenable to neurosurgical intervention, the routinely performed, nonvalidated practice of serial head CT scans frequently necessitates increased hospital resources and exposure to ionizing radiation. The study goal was to evaluate clinical and imaging features of isolated falcotentorial subdural hematoma at presentation and short-term follow-up.

MATERIALS AND METHODS

We performed a retrospective analysis of patients presenting to a level 1 trauma center from January 2013 to March 2015 undergoing initial and short-term follow-up CT with initial findings positive for isolated subdural hematoma along the falx and/or tentorium. Patients with penetrating trauma, other sites of intracranial hemorrhage, or depressed skull fractures were excluded. Patient sex, age, Glasgow Coma Scale score, and anticoagulation history were obtained through review of the electronic medical records.

RESULTS

Eighty patients met the inclusion criteria (53 males; 27 females; median age, 61 years). Of subdural hematomas, 57.1% were falcine, 33.8% were tentorial, and 9.1% were mixed. The mean initial Glasgow Coma Scale score was 14.2 (range, 6-15). Isolated falcotentorial subdural hematomas were small (mean, 2.8 mm; range, 1-8 mm) without mass effect and significant change on follow-up CT (mean, 2.7 mm; range, 0-8 mm; P = .06), with an average follow-up time of 10.3 hours (range, 3.9-192 hours). All repeat CTs demonstrated no change or decreased size of the initial subdural hematoma. No new intracranial hemorrhages were seen on follow-up CT.

CONCLUSIONS

Isolated falcotentorial subdural hematomas in blunt traumatic brain injury average 2.8 mm in thickness and do not increase in size on short-term follow-up CT. Present data suggest that repeat CT in patients with mild traumatic brain injury with isolated falcotentorial subdural hematoma may not be necessary.

Safety and effectiveness of early chemical deep venous thrombosis prophylaxis after spinal cord injury: pilot prospective data

OBJECTIVE

Spinal cord injuries (SCIs) occur in approximately 17,000 people in the US each year. The average length of hospital stay is 11 days, and deep venous thrombosis (DVT) rates as high as 65% are reported in these patients. There is no consensus on the appropriate timing of chemical DVT prophylaxis for this critically injured patient cohort. The object of this study was to determine if low-molecular-weight heparin (LMWH) was safe and effective if given within 24 hours of SCI.

METHODS

The Transforming Research and Clinical Knowledge in SCIs study is a prospective observational study conducted by the UCSF Brain and Spinal Injury Center. Protocol at this center includes administration of LMWH within 24 hours of SCI. Data were retrospectively reviewed to determine DVT rate, pulmonary embolism (PE) rate, and hemorrhagic complications.

RESULTS

Forty-nine patients were enrolled in the study. There were 3 DVTs (6.1%), 2 PEs (4.1%), and no hemorrhagic complications. Regression modeling did not find an association between DVT and/or PE and age, American Spinal Injury Association grade, sex, race, or having undergone a neurosurgical procedure.

CONCLUSIONS

A standardized protocol in which LMWH is given to patients with SCI within 24 hours of injury is effective in keeping venous thromboembolism at the lower end of the reported range, and is safe, with a zero rate of adverse bleeding events.

Apolipoprotein E epsilon 4 (APOE-ε4) genotype is associated with decreased 6-month verbal memory performance after mild traumatic brain injury

INTRODUCTION

The apolipoprotein E (APOE) ε4 allele associates with memory impairment in neurodegenerative diseases. Its association with memory after mild traumatic brain injury (mTBI) is unclear.

METHODS

mTBI patients (Glasgow Coma Scale score 13-15, no neurosurgical intervention, extracranial Abbreviated Injury Scale score ≤1) aged ≥18 years with APOE genotyping results were extracted from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury Pilot (TRACK-TBI Pilot) study. Cohorts determined by APOE-ε4(+/-) were assessed for associations with 6-month verbal memory, measured by California Verbal Learning Test, Second Edition (CVLT-II) subscales: Immediate Recall Trials 1-5 (IRT), Short-Delay Free Recall (SDFR), Short-Delay Cued Recall (SDCR), Long-Delay Free Recall (LDFR), and Long-Delay Cued Recall (LDCR). Multivariable regression controlled for demographic factors, seizure history, loss of consciousness, posttraumatic amnesia, and acute intracranial pathology on computed tomography (CT).

RESULTS

In 114 mTBI patients (APOE-ε4(-)=79; APOE-ε4(+)=35), ApoE-ε4(+) was associated with long-delay verbal memory deficits (LDFR: B = -1.17 points, 95% CI [-2.33, -0.01], p = .049; LDCR: B = -1.58 [-2.63, -0.52], p = .004), and a marginal decrease on SDCR (B = -1.02 [-2.05, 0.00], p = .050). CT pathology was the strongest predictor of decreased verbal memory (IRT: B = -8.49, SDFR: B = -2.50, SDCR: B = -1.85, LDFR: B = -2.61, LDCR: B = -2.60; p < .001). Seizure history was associated with decreased short-term memory (SDFR: B = -1.32, p = .037; SDCR: B = -1.44, p = .038).

CONCLUSION

The APOE-ε4 allele may confer an increased risk of impairment of 6-month verbal memory for patients suffering mTBI, with implications for heightened surveillance and targeted therapies. Acute intracranial pathology remains the driver of decreased verbal memory performance at 6 months after mTBI.

[18F]-Sodium Fluoride PET MR-Based Localization and Quantification of Bone Turnover as a Biomarker for Facet Joint-Induced Disability

Our aim was to prospectively evaluate the relationship between low back pain-related disability and quantitative measures from [¹⁸F]-sodium fluoride ([¹⁸F]-NaF) MR imaging. Six patients with facetogenic low back pain underwent dynamic [¹⁸F]-NaF PET/MR imaging. PET metrics were correlated with clinical measures and MR imaging grading of lumbar facet arthropathy. A significant positive correlation was observed between maximum facet joint uptake rate and clinical disability (P < .05). These data suggest that dynamic [¹⁸F]-NaF PET may serve as a useful biomarker for facetogenic disability.

Multivariate Analysis of MRI Biomarkers for Predicting Neurologic Impairment in Cervical Spinal Cord Injury

BACKGROUND AND PURPOSE

Acute markers of spinal cord injury are essential for both diagnostic and prognostic purposes. The goal of this study was to assess the relationship between early MR imaging biomarkers after acute cervical spinal cord injury and to evaluate their predictive validity of neurologic impairment.

MATERIALS AND METHODS

We performed a retrospective cohort study of 95 patients with acute spinal cord injury and preoperative MR imaging within 24 hours of injury. The American Spinal Injury Association Impairment Scale was used as our primary outcome measure to define neurologic impairment. We assessed several MR imaging features of injury, including axial grade (Brain and Spinal Injury Center score), sagittal grade, length of injury, maximum canal compromise, and maximum spinal cord compression. Data-driven nonlinear principal component analysis was followed by correlation and optimal-scaled multiple variable regression to predict neurologic impairment.

RESULTS

Nonlinear principal component analysis identified 2 clusters of MR imaging variables related to 1) measures of intrinsic cord signal abnormality and 2) measures of extrinsic cord compression. Neurologic impairment was best accounted for by MR imaging measures of intrinsic cord signal abnormality, with axial grade representing the most accurate predictor of short-term impairment, even when correcting for surgical decompression and degree of cord compression.

CONCLUSIONS

This study demonstrates the utility of applying nonlinear principal component analysis for defining the relationship between MR imaging biomarkers in a complex clinical syndrome of cervical spinal cord injury. Of the assessed imaging biomarkers, the intrinsic measures of cord signal abnormality were most predictive of neurologic impairment in acute spinal cord injury, highlighting the value of axial T2 MR imaging.

MRI Atlas-Based Measurement of Spinal Cord Injury Predicts Outcome in Acute Flaccid Myelitis

BACKGROUND AND PURPOSE

Recent advances in spinal cord imaging analysis have led to the development of a robust anatomic template and atlas incorporated into an open-source platform referred to as the Spinal Cord Toolbox. Using the Spinal Cord Toolbox, we sought to correlate measures of GM, WM, and cross-sectional area pathology on T2 MR imaging with motor disability in patients with acute flaccid myelitis.

MATERIALS AND METHODS

Spinal cord imaging for 9 patients with acute flaccid myelitis was analyzed by using the Spinal Cord Toolbox. A semiautomated pipeline using the Spinal Cord Toolbox measured lesion involvement in GM, WM, and total spinal cord cross-sectional area. Proportions of GM, WM, and cross-sectional area affected by T2 hyperintensity were calculated across 3 ROIs: 1) center axial section of lesion; 2) full lesion segment; and 3) full cord atlas volume. Spearman rank order correlation was calculated to compare MR metrics with clinical measures of disability.

RESULTS

Proportion of GM metrics at the center axial section significantly correlated with measures of motor impairment upon admission (r [9] = -0.78; P = .014) and at 3-month follow-up (r [9] = -0.66; P = .05). Further, proportion of GM extracted across the full lesion segment significantly correlated with initial motor impairment (r [9] = -0.74, P = .024). No significant correlation was found for proportion of WM or proportion of cross-sectional area with clinical disability.

CONCLUSIONS

Atlas-based measures of proportion of GM T2 signal abnormality measured on a single axial MR imaging section and across the full lesion segment correlate with motor impairment and outcome in patients with acute flaccid myelitis. This is the first atlas-based study to correlate clinical outcomes with segmented measures of T2 signal abnormality in the spinal cord.

In Vivo Monitoring of Rat Spinal Cord Metabolism Using Hyperpolarized Carbon-13 MR Spectroscopic Imaging

This study demonstrated the feasibility of using hyperpolarized ¹³C-MR spectroscopic imaging with [1-¹³C]-pyruvate to evaluate in vivo spinal cord metabolism. High pyruvate and relatively small lactate signal were observed in the cervical spinal cords of naive rats. Lactate and pyruvate measures were similar for spinal cord and supratentorial brain. The results from this study establish baseline measures for spinal cord hyperpolarized MRS imaging with ¹³C pyruvate. This technique holds promise as a valuable molecular imaging tool for monitoring biochemical processes in the normal and diseased spinal cord.

Imaging Evaluation of Acute Traumatic Brain Injury

Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide. Imaging plays an important role in the evaluation, diagnosis, and triage of patients with TBI. Recent studies suggest that it also helps predict patient outcomes. TBI consists of multiple pathoanatomic entities. This article reviews the current state of TBI imaging including its indications, benefits and limitations of the modalities, imaging protocols, and imaging findings for each of these pathoanatomic entities. Also briefly surveyed are advanced imaging techniques, which include several promising areas of TBI research.

T1ρ and T2 -based characterization of regional variations in intervertebral discs to detect early degenerative changes

Lower back pain is one of the main contributors to morbidity and chronic disability in the United States. Despite the significance of the problem, it is still not well understood. There is a clear need for objective, non-invasive biomarkers to localize specific pain generators and identify early stage changes to enable reliable diagnosis and treatment. In this study we focus on intervertebral disc degeneration as a source of lower back pain. Quantitative imaging markers T1ρ and T2 have been shown to be promising techniques for in vivo diagnosis of biochemical degeneration in discs due to their sensitivity to macromolecular changes in proteoglycan content and collagen integrity. We describe a semi-automated technique for quantifying T1ρ and T2 relaxation time maps in the nucleus pulposus (NP) and the annulus fibrosus (AF) of the lumbar intervertebral discs. Compositional changes within the NP and AF associated with degeneration occur much earlier than the visually observable structural changes. The proposed technique rigorously quantifies these biochemical changes taking into account subtle regional variations to allow interpretation of early degenerative changes that are difficult to interpret with traditional MRI techniques and clinical subjective grading scores. T1ρ and T2 relaxation times in the NP decrease with degenerative severity in the disc. Moreover, standard deviation and texture measurements of these values show sharper and more significant changes during early degeneration compared to later degenerative stages. Our results suggest that future prospective studies should include automated T1ρ and T2 metrics as early biomarkers for disc degeneration-induced lower back pain. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1373-1381, 2016.

Magnetic resonance neurography in the diagnosis of neuropathies of the lumbosacral plexus: a pictorial review

Magnetic resonance neurography (MRN) is an important tool to detect abnormalities of peripheral nerves. This pictorial review demonstrates the MRN features of a variety of neuropathies affecting the lumbosacral plexus (LSP) and lower extremity nerves, drawn from over 1200 MRNs from our institution and supplemented by the literature. Abnormalities can be due to spinal compression, extraspinal compression, malignancy, musculoskeletal disease, iatrogenesis, inflammation, infection, and idiopathic disorders. We discuss indications and limitations of MRN in diagnosing LSP neuropathies. As MRN becomes more widely used, physicians must become familiar with the differential diagnosis of abnormalities detectable with MRN of the LSP.

An Imaging-Based Approach to Spinal Cord Infection

Infections of the spinal cord, nerve roots, and surrounding meninges are uncommon, but highly significant given their potential for severe morbidity and even mortality. Prompt diagnosis can be lifesaving, as many spinal infections are treatable. Advances in imaging technology have now firmly established magnetic resonance imaging (MRI) as the gold standard for spinal cord imaging evaluation, enabling the depiction of infectious myelopathies with exquisite detail and contrast. In this article, we aim to provide an overview of MRI findings for spinal cord infections with special focus on imaging patterns of infection that are primarily confined to the spinal cord, spinal meninges, and spinal nerve roots. In this context, we describe and organize this review around 5 distinct patterns of transverse spinal abnormality that may be detected with MRI as follows: (1) extramedullary, (2) centromedullary, (3) eccentric, (4) frontal horn, and (5) irregular. We seek to classify the most common presentations for a wide variety of infectious agents within this image-based framework while realizing that significant overlap and variation exists, including some infections that remain occult with conventional imaging techniques.

Multidimensional Analysis of Magnetic Resonance Imaging Predicts Early Impairment in Thoracic and Thoracolumbar Spinal Cord Injury

Literature examining magnetic resonance imaging (MRI) in acute spinal cord injury (SCI) has focused on cervical SCI. Reproducible systems have been developed for MRI-based grading; however, it is unclear how they apply to thoracic SCI. Our hypothesis is that MRI measures will group as coherent multivariate principal component (PC) ensembles, and that distinct PCs and individual variables will show discriminant validity for predicting early impairment in thoracic SCI. We undertook a retrospective cohort study of 25 patients with acute thoracic SCI who underwent MRI on admission and had American Spinal Injury Association Impairment Scale (AIS) assessment at hospital discharge. Imaging variables of axial grade, sagittal grade, length of injury, thoracolumbar injury classification system (TLICS), maximum canal compromise (MCC), and maximum spinal cord compression (MSCC) were collected. We performed an analytical workflow to detect multivariate PC patterns followed by explicit hypothesis testing to predict AIS at discharge. All imaging variables loaded positively on PC1 (64.3% of variance), which was highly related to AIS at discharge. MCC, MSCC, and TLICS also loaded positively on PC2 (22.7% of variance), while variables concerning cord signal abnormality loaded negatively on PC2. PC2 was highly related to the patient undergoing surgical decompression. Variables of signal abnormality were all negatively correlated with AIS at discharge with the highest level of correlation for axial grade as assessed with the Brain and Spinal Injury Center (BASIC) score. A multiple variable model identified BASIC as the only statistically significant predictor of AIS at discharge, signifying that BASIC best captured the variance in AIS within our study population. Our study provides evidence of convergent validity, construct validity, and clinical predictive validity for the sampled MRI measures of SCI when applied in acute thoracic and thoracolumbar SCI.

Failure of Mean Arterial Pressure Goals to Improve Outcomes Following Penetrating Spinal Cord Injury

BACKGROUND:

Increased spinal cord perfusion and blood pressure goals have been recommended for spinal cord injury (SCI). Penetrating SCI is associated with poor prognosis, but there is a paucity of literature examining the role of vasopressor administration for the maintenance of mean arterial pressure (MAP) goals in this patient population.

OBJECTIVE:

To elucidate this topic and to determine the efficacy of vasopressor administration in penetrating SCI by examining a case series of consecutive penetrating SCIs.

METHODS:

We reviewed consecutive patients with complete penetrating SCI who met inclusion and exclusion criteria, including the administration of vasopressors to maintain MAP goals. We identified 14 patients with complete penetrating SCIs with an admission American Spinal Injury Association grade of A from 2005 to 2011. The neurological recovery, complications, interventions, and vasopressor administration strategies were reviewed and compared with those of a cohort with complete blunt SCI.

RESULTS:

In our patient population, only 1 patient with penetrating SCI (7.1%) experienced neurological recovery, as determined by improvement in the American Spinal Injury Association grade, despite the administration of vasopressors for supraphysiological MAP goals for an average of 101.07 ± 34.96 hours. Furthermore, 71.43% of patients with penetrating SCI treated with vasopressors experienced associated cardiogenic complications.

CONCLUSION:

Given the decreased likelihood of neurological improvement in penetrating injuries, it may be important to re-examine intervention strategies in this population. Specifically, the use of vasopressors, in particular dopamine, with their associated complications is more likely to cause complications than to result in neurological improvement. Our experience shows that patients with acute penetrating SCI are unlikely to recover, despite aggressive cardiopulmonary management.

(18)F-Sodium Fluoride PET-CT Hybrid Imaging of the Lumbar Facet Joints: Tracer Uptake and Degree of Correlation to CT-graded Arthropathy

We aim to evaluate ¹⁸F-NaF uptake by facet joints with hybrid PET-CT technique. Specifically, we evaluate NaF uptake in the facet joints of the lower lumbar spine, and correlate with the morphologic grade of facet arthropathy on CT. 30 consecutive patients who underwent standard vertex to toes NaF PET-CT for re-staging of primary neoplastic disease without measurable or documented bony metastases were identified. Maximum (SUVmax) and average (SUVavg) standardized uptake values were calculated for each L3-4, L4-5, and L5-S1 facet joint (n = 180) and normalized to average uptake in the non-diseased femur. A Pathria grade (0-3) was assigned to each facet based upon the CT morphology. Spearman's rank correlation was performed for normalized SUVmax and SUVavg with Pathria grade. ANOVA was performed with Tukey-Kramer pairwise tests to evaluate differences in uptake between Pathria groups. Facet normalized SUVmax (r = 0.31, P < 0.001) and SUVavg (r = 0.28, P < 0.001) demonstrated a mild positive correlation with CT Pathria grade. There was a wide range of uptake values within each Pathria grade subgroup with statistically significant differences in uptake only between Pathria grade 3 as compared to grades 0, 1, and 2. In conclusion, NaF uptake and morphologic changes of the facet joint on CT are weakly correlated. Physiologic information provided by NaF uptake is often discrepant with structural findings on CT suggesting NaF PET may supplement conventional structural imaging for identification of pain generating facet joints. Prospective investigation into the relationship of facet joint NaF uptake with pain and response to pain interventions is warranted.

Diffusion-Weighted Magnetic Resonance Imaging Characterization of White Matter Injury Produced by Axon-Sparing Demyelination and Severe Contusion Spinal Cord Injury in Rats

Alterations in magnetic resonance imaging (MRI)-derived measurements of water diffusion parallel (D∥) and perpendicular (D⊥) to white matter tracts have been specifically attributed to pathology of axons and myelin, respectively. We test the hypothesis that directional diffusion measurements can distinguish between axon-sparing chemical demyelination and severe contusion spinal cord white matter injury. Adult rats received either unilateral ethidium bromide (EB) microinjections (chemical demyelination) into the lateral funiculus of the spinal cord at C5 or were subjected to unilateral severe contusion spinal cord injury (SCI). Diffusion MRI metrics in the lateral funiculus were analyzed at early and late time-points following injury and correlated with histology. Early EB-demyelination resulted in a significant elevation in D⊥ and significant reduction in D∥ at the injury epicenter, with histological evidence of uniform axon preservation. Alterations in D⊥ and D∥ at the epicenter of early EB-demyelination were not significantly different from those observed with severe contusion at the epicenter, where histology demonstrated severe combined axonal and myelin injury. Diffusion abnormalities away from the injury epicenter were seen with contusion injury, but not with EB-demyelination. Chronic EB lesions underwent endogenous remyelination with normalization of diffusion metrics, whereas chronic contusion resulted in persistently altered diffusivities. In the early setting, directional diffusion measurements at the injury epicenter associated with chemical demyelination are indistinguishable from those seen with severe contusive SCI, despite dramatic pathologic differences between injury models. Caution is advised in interpretation of diffusion metrics with respect to specific white matter structural alterations. Diffusion analysis should not be limited to the epicenter of focal spinal lesions as alterations marginal to the epicenter are useful for assessing the nature of focal white matter injury.

Complications and outcomes of vasopressor usage in acute traumatic central cord syndrome

OBJECT

The optimal mean arterial pressure (MAP) for spinal cord perfusion after trauma remains unclear. Although there are published data on MAP goals after spinal cord injury (SCI), the specific blood pressure management for acute traumatic central cord syndrome (ATCCS) and the implications of these interventions have yet to be elucidated. Additionally, the complications of specific vasopressors have not been fully explored in this injury condition.

METHODS

The present study is a retrospective cohort analysis of 34 patients with ATCCS who received any vasopressor to maintain blood pressure above predetermined MAP goals at a single Level 1 trauma center. The collected variables were American Spinal Injury Association (ASIA) grades at admission and discharge, administered vasopressor and associated complications, other interventions and complications, and timing of surgery. The relationship between the 2 most common vasopressors—dopamine and phenylephrine—and complications within the cohort as a whole were explored, and again after stratification by age.

RESULTS

The mean age of the ATCCS patients was 62 years. Dopamine was the most commonly used primary vasopressor (91% of patients), followed by phenylephrine (65%). Vasopressors were administered to maintain MAP goals fora mean of 101 hours. Neurological status improved by a median of 1 ASIA grade in all patients, regardless of the choice of vasopressor. Sixty-four percent of surgical patients underwent decompression within 24 hours. There was no observed relationship between the timing of surgical intervention and the complication rate. Cardiogenic complications associated with vasopressor usage were notable in 68% of patients who received dopamine and 46% of patients who received phenylephrine. These differences were not statistically significant (OR with dopamine 2.50 [95% CI 0.82–7.78], p = 0.105). However, in the subgroup of patients > 55 years, dopamine produced statistically significant increases in the complication rates when compared with phenylephrine (83% vs 50% for dopamine and phenylephrine, respectively; OR with dopamine 5.0 [95% CI 0.99–25.34], p = 0.044).

CONCLUSIONS

Vasopressor usage in ATCCS patients is associated with complication rates that are similar to the reported literature for SCI. Dopamine was associated with a higher risk of complications in patients > 55 years. Given the increased incidence of ATCCS in older populations, determination of MAP goals and vasopressor administration should be carefully considered in these patients. While a randomized control trial on this topic may not be practical, a multiinstitutional prospective study for SCI that includes ATCCS patients as a subpopulation would be useful for examining MAP goals in this population.

The caverno-apical triangle: anatomic-pathological considerations and pictorial review

BACKGROUND

The caverno-apical triangle (CAT) is defined from the components that define its contours: the cavernous sinus and the orbital apex. A wide range of pathologies arise from the space between the cavernous sinus and the orbital apex.

OBJECT

To better define radiologically this critical anatomic landmark and establish an organized approach for image analysis to help generate focused differential diagnoses and accurately characterize lesions found on imaging.

CONCLUSION

We have identified common imaging characteristics of frequently encountered lesions and divided them into specific categories to facilitate creation of logical and focused differential diagnoses.

The Brain and Spinal Injury Center score: a novel, simple, and reproducible method for assessing the severity of acute cervical spinal cord injury with axial T2-weighted MRI findings

OBJECT

Previous studies that have evaluated the prognostic value of abnormal changes in signals on T2-weighted MRI scans of an injured spinal cord have focused on the longitudinal extent of this signal abnormality in the sagittal plane. Although the transverse extent of injury and the degree of spared spinal cord white matter have been shown to be important for predicting outcomes in preclinical animal models of spinal cord injury (SCI), surprisingly little is known about the prognostic value of altered T2 relaxivity in humans in the axial plane.

METHODS

The authors undertook a retrospective chart review of 60 patients who met the inclusion criteria of this study and presented to the authors’ Level I trauma center with an acute blunt traumatic cervical SCI. Within 48 hours of admission, all patients underwent MRI examination, which included axial and sagittal T2 images. Neurological symptoms, evaluated with the grades according to the American Spinal Injury Association (ASIA) Impairment Scale (AIS), at the time of admission and at hospital discharge were correlated with MRI findings. Five distinct patterns of intramedullary spinal cord T2 signal abnormality were defined in the axial plane at the injury epicenter. These patterns were assigned ordinal values ranging from 0 to 4, referred to as the Brain and Spinal Injury Center (BASIC) scores, which encompassed the spectrum of SCI severity.

RESULTS

The BASIC score strongly correlated with neurological symptoms at the time of both hospital admission and discharge. It also distinguished patients initially presenting with complete injury who improved by at least one AIS grade by the time of discharge from those whose injury did not improve. The authors’ proposed score was rapid to apply and showed excellent interrater reliability.

CONCLUSIONS

The authors describe a novel 5-point ordinal MRI score for classifying acute SCIs on the basis of axial T2-weighted imaging. The proposed BASIC score stratifies the SCIs according to the extent of transverse T2 signal abnormality during the acute phase of the injury. The new score improves on current MRI-based prognostic descriptions for SCI by reflecting functionally and anatomically significant patterns of intramedullary T2 signal abnormality in the axial plane.

Diagnostic Performance of Brain MRI in Immune Reconstitution Inflammatory Syndrome

BACKGROUND AND PURPOSE

Central nervous system immune reconstitution inflammatory syndrome (CNS-IRIS) significantly negatively impacts the human immunodeficiency virus (HIV)-infected population on combination antiretroviral therapy (cART). We sought to determine the diagnostic performance of several magnetic resonance imaging (MRI) features for CNS-IRIS in a cohort of HIV+ patients recently started on cART.

METHODS

Our radiologic database was searched from January 2003 to September 2014 retrospectively for patients diagnosed with HIV and worsening symptoms on cART. A total of 20 patients with HIV were identified; patients were classified as having CNS-IRIS on the basis of established clinical criteria (8 patients; 12 age- and sex-matched controls). Brain MR images were obtained at a single post-cART timepoint during hospitalization for acute neurologic deterioration and blindly interpreted by two experienced neuroradiologists for the presence of four variables: intrinsic T1 hyperintensity, marginal reduced diffusion, and marginal enhancement or perivascular enhancement.

RESULTS

Although each individual finding showed moderate predictive accuracy, the combination of MR findings demonstrated good test characteristics: sensitivity 88% (confidence interval [CI] 62-98), specificity 79% (58-93), positive predictive value 71% (44-90%), and negative predictive value 83% (CI 52-98%). In addition, this final diagnosis demonstrated good predictive accuracy, area under curve .78 (CI .63-.91), and moderate inter-reader agreement, κ = .55.

CONCLUSIONS

Our findings suggest that although each individual MR finding shows only moderate diagnostic performance, the combined assessment of experienced neuroradiologists has good predictive accuracy. The absence of any described MRI findings makes the diagnosis of CNS-IRIS highly unlikely.

Accuracy of flat panel detector CT with integrated navigational software with and without MR fusion for single-pass needle placement

PURPOSE

Fluoroscopic systems in modern interventional suites have the ability to perform flat panel detector CT (FDCT) with navigational guidance. Fusion with MR allows navigational guidance towards FDCT occult targets. We aim to evaluate the accuracy of this system using single-pass needle placement in a deep brain stimulation (DBS) phantom.

MATERIALS AND METHODS

MR was performed on a head phantom with DBS lead targets. The head phantom was placed into fixation and FDCT was performed. FDCT and MR datasets were automatically fused using the integrated guidance system (iGuide, Siemens). A DBS target was selected on the MR dataset. A 10 cm, 19 G needle was advanced by hand in a single pass using laser crosshair guidance. Radial error was visually assessed against measurement markers on the target and by a second FDCT. Ten needles were placed using CT-MR fusion and 10 needles were placed without MR fusion, with targeting based solely on FDCT and fusion steps repeated for every pass.

RESULTS

Mean radial error was 2.75±1.39 mm as defined by visual assessment to the centre of the DBS target and 2.80±1.43 mm as defined by FDCT to the centre of the selected target point. There were no statistically significant differences in error between MR fusion and non-MR guided series.

CONCLUSIONS

Single pass needle placement in a DBS phantom using FDCT guidance is associated with a radial error of approximately 2.5-3.0 mm at a depth of approximately 80 mm. This system could accurately target sub-centimetre intracranial lesions defined on MR.

Ex-PRESS glaucoma filter: an MRI compatible metallic orbital foreign body imaged at 1.5 and 3T

AIM

To report on the MRI compatibility of the Ex-PRESS glaucoma filtration device, a tiny metallic implant placed into the anterior chamber of the eye that is much smaller than traditional glaucoma shunts, and to educate the radiology community regarding its appearance.

MATERIALS AND METHODS

Seven patients with Ex-PRESS glaucoma filtration devices were identified that had undergone MRI at San Francisco General Hospital/University of California San Francisco Medical Center by searching and cross-referencing the radiology reporting system and the electronic medical record. MRI images were reviewed for artefact interfering with interpretation. Ophthalmology examinations were reviewed for evidence of complications.

RESULTS

Eighteen individual MRI examinations were performed during 12 unique MRI events on these 7 patients. 13/18 individual MRI examinations and 7/12 MRI events were performed at 3 T with the others performed at 1.5 T. Mean time from Ex-PRESS implantation to MRI was 17.5 months. Mean time from MRI to first ophthalmology examination was 1.1 months and from MRI to latest ophthalmology examination was 6.6 months. Susceptibility artefact did not interfere with image interpretation and no complications related to MRI were encountered.

CONCLUSION

The Ex-PRESS glaucoma filtration device appears to be safe for MRI at 1.5 and 3 T and does not produce significant susceptibility artefact to affect diagnostic interpretation adversely.