Intramedullary Compartment Research Articles

Tetra-compartmental spinal infection with conus medullaris syndrome: illustrative case.

Recent literature suggests that spinal infections are increasing in prevalence. Any compartment can be infected in the spine; however, multicompartmental infections are rare. To the authors' knowledge, this report is the only reported case of a tetra-compartmental spinal infection consisting of epidural, subdural, subarachnoid, and intramedullary components with a contiguous lumbar spondylodiscitis resulting in conus medullaris syndrome requiring surgical intervention. This case highlights the importance of surgical intervention in severe cases such as the one illustrated in this report. Second, magnetic resonance imaging with and without contrast is required to check for spreading of the infection as these findings may change the surgical approach. Last, the use of intraoperative ultrasound is paramount to evaluate the subdural and intramedullary compartments in severe cases.

Spinal oncologic paraparesis: Analysis of neurological and surgical outcomes in patients with intramedullary, extramedullary, and extradural tumors.

Paraparesis due to oncologic lesions of the spine warrants swift neurosurgical intervention to prevent permanent disability and hence maintain independence of affected patients. Clinical parameters that predict a favorable outcome after surgical intervention could aid decision-making in emergency situations. Patients who underwent surgical intervention for paraparesis (grade of muscle strength <5 according to the British Medical Research Council grading system) secondary to spinal neoplasms between 2006 and 2020 were included in a single-center retrospective analysis. Pre- and postoperative clinical data were collected. The neurological status was assessed using the modified McCormick Disability Scale (mMcC) Score. In a univariate analysis, patients with favorable (discharge mMcC improved or stable at <3) and non-favorable outcome (discharge mMcC deteriorated or stable at >2) and different tumor anatomical compartments were statistically compared. 117 patients with oncologic paraparesis pertaining to intramedullary lesions (n=17, 15%), intradural extramedullary (n=24, 21%) and extradural lesions (n=76, 65%) with a mean age of 65.3 ± 14.6 years were included in the analysis. Thoracic tumors were the most common (77%), followed by lumbar and cervical tumors (13% and 12%, respectively). Surgery was performed within a mean of 36±60 hours of admission across all tumors and included decompression over a median of 2 segments (IQR:1-3) and mostly subtotal tumor resection (n=83, 71%). Surgical and medical complications were documented in 9% (n=11) and 7% (n=8) of cases, respectively. The median hospital length-of-stay was 9 (7-13) days. Upon discharge, the median mMcC score had improved from 3 to 2 (p<0.0001). At last follow-up (median 180; IQR 51-1080 days), patients showed an improvement in their mean Karnofsky Performance Score (KPS) from 51.7±18.8% to 65.3±20.4% (p<0.001). Localization in the intramedullary compartment, a high preoperative mMcC score, in addition to bladder and bowel dysfunction were associated with a non-favorable outcome (p<0.001). The data presented on patients with spinal oncologic paraparesis provide a risk-benefit narrative that favors surgical intervention across all etiologies. At the same time, they outline clinical factors that confer a less-favorable outcome like intramedullary tumor localization, a high McCormick score and/or bladder and bowel abnormalities at admission.

Transcriptomic Portraits and Molecular Pathway Activation Features of Adult Spinal Intramedullary Astrocytomas.

In this study, we report 31 spinal intramedullary astrocytoma (SIA) RNA sequencing (RNA-seq) profiles for 25 adult patients with documented clinical annotations. To our knowledge, this is the first clinically annotated RNA-seq dataset of spinal astrocytomas derived from the intradural intramedullary compartment. We compared these tumor profiles with the previous healthy central nervous system (CNS) RNA-seq data for spinal cord and brain and identified SIA-specific gene sets and molecular pathways. Our findings suggest a trend for SIA-upregulated pathways governing interactions with the immune cells and downregulated pathways for the neuronal functioning in the context of normal CNS activity. In two patient tumor biosamples, we identified diagnostic KIAA1549-BRAF fusion oncogenes, and we also found 16 new SIA-associated fusion transcripts. In addition, we bioinformatically simulated activities of targeted cancer drugs in SIA samples and predicted that several tyrosine kinase inhibitory drugs and thalidomide analogs could be potentially effective as second-line treatment agents to aid in the prevention of SIA recurrence and progression.

Neuroimaging of Spinal Cord and Cauda Equina Disorders.

This article reviews the neuroimaging of disorders of the spinal cord and cauda equina, with a focus on MRI. An anatomic approach is used; diseases of the extradural, intradural-extramedullary, and intramedullary (parenchymal) compartments are considered, and both neoplastic and non-neoplastic conditions are covered. Differentiating imaging features are highlighted. Although T2-hyperintense signal abnormality of the spinal cord can have myriad etiologies, neuroimaging can provide specific diagnoses or considerably narrow the differential diagnosis in many cases. Intradural-extramedullary lesions compressing the spinal cord have a limited differential diagnosis and are usually benign; meningiomas and schwannomas are most common. Extradural lesions can often be specifically diagnosed. Disk herniations are the most commonly encountered mass of the epidural space. Cervical spondylotic myelopathy can cause a characteristic pattern of enhancement, which may be mistaken for an intrinsic myelopathy. A do-not-miss diagnosis of the extradural compartment is idiopathic spinal cord herniation, the appearance of which can overlap with arachnoid cysts and webs. Regarding intrinsic causes of myelopathy, the lesions of multiple sclerosis are characteristically short segment but can be confluent when multiple. Postcontrast MRI can be particularly helpful, including when attempting to differentiate the long-segment myelopathy of neurosarcoidosis and aquaporin-4 (AQP4)-IgG-seropositive neuromyelitis optica spectrum disorder (NMOSD) and when characterizing spinal cord tumors such as primary neoplasms and metastases. Spinal dural arteriovenous fistula is another do-not-miss diagnosis, with characteristic MRI features both precontrast and postcontrast. Tract-specific white matter involvement can be a clue for diseases such as subacute combined degeneration, paraneoplastic myelopathy, and radiation myelitis, whereas gray matter-specific involvement can suggest conditions such as cord infarct, viral myelitis, or myelin oligodendrocyte glycoprotein (MOG)-IgG associated disorder. Knowledge of the neuroimaging findings of the many causes of spinal cord and cauda equina dysfunction is critical for both neurologists and neuroradiologists. A structured approach to lesion compartmental location and imaging feature characterization is recommended.

Predictive modeling of long-term opioid and benzodiazepine use after intradural tumor resection

BACKGROUND CONTEXTDespite increased awareness of the ongoing opioid epidemic, opioid and benzodiazepine use remain high after spine surgery. In particular, long-term co-prescription of opioids and benzodiazepines have been linked to high risk of overdose-associated death. Tumor patients represent a unique subset of spine surgery patients and few studies have attempted to develop predictive models to anticipate long-term opioid and benzodiazepine use after spinal tumor resection. METHODSThe IBM Watson Health MarketScan Database and Medicare Supplement were assessed to identify admissions for intradural tumor resection between 2007 and 2015. Adult patients were required to have at least 6 months of continuous preadmission baseline data and 12 months of continuous postdischarge follow-up. Primary outcomes were long-term opioid and benzodiazepine use, defined as at least 6 prescriptions within 12 months. Secondary outcomes were durations of opioid and benzodiazepine prescribing. Logistic regression models, with and without regularization, were trained on an 80% training sample and validated on the withheld 20%. RESULTSA total of 1,942 patients were identified. The majority of tumors were extramedullary (74.8%) and benign (62.5%). A minority of patients received arthrodesis (9.2%) and most patients were discharged to home (79.1%). Factors associated with postdischarge opioid use duration include tumor malignancy (vs benign, B=19.8 prescribed-days/year, 95% confidence interval [CI] 1.1–38.5) and intramedullary compartment (vs extramedullary, B=18.1 prescribed-days/year, 95% CI 3.3–32.9). Pre- and perioperative use of prescribed nonsteroidal anti-inflammatory drugs and gabapentin/pregabalin were associated with shorter and longer duration opioid use, respectively. History of opioid and history of benzodiazepine use were both associated with increased postdischarge opioid and benzodiazepine use. Intramedullary location was associated with longer duration postdischarge benzodiazepine use (B=10.3 prescribed-days/year, 95% CI 1.5–19.1). Among assessed models, elastic net regularization demonstrated best predictive performance in the withheld validation cohort when assessing both long-term opioid use (area under curve [AUC]=0.748) and long-term benzodiazepine use (AUC=0.704). Applying our model to the validation set, patients scored as low-risk demonstrated a 4.8% and 2.4% risk of long-term opioid and benzodiazepine use, respectively, compared to 35.2% and 11.1% of high-risk patients. CONCLUSIONSWe developed and validated a parsimonious, predictive model to anticipate long-term opioid and benzodiazepine use early after intradural tumor resection, providing physicians opportunities to consider alternative pain management strategies.

EVALUATION OF COMPRESSIVE MYELOPATHY BY USING MRI AS THE MODALITY OF CHOICE

The primary purpose of the study is to discuss the causes of compressive myelopathy, characterize compressive lesions, and to localize the lesion either to extramedullary or intramedullary compartment using magnetic resonance imaging (MRI) as the modality of choice. A hundred patients who came to the hospital and are clinically suspected of having compressive myelopathy underwent MRI. The leading common cause of compressive myelopathy in this study was found to be extradural compression over the cord due to degenerative changes (50%). The second most common cause was found to be infectious spondylitis (20%), third being post-traumatic compressive myelopathy (12%), followed by primary neoplasms &amp; metastases (12%) and other causes like hindbrain and craniovertebral abnormalities(6%). MRI detected cord signal changes in cases with cord compression and also assessed the integrity of the spinal cord, intervertebral discs, and ligament after acute spinal trauma. MRI, though expensive, is a non-invasive, radiation-free modality with high sensitivity, specificity, and accuracy for the evaluation of compressive myelopathy.

Induction of periosteal bone formation by intraosseous BMP-2 injection in a mouse model of osteogenesis imperfecta.

PurposeSurgical interventions are routinely performed on children with osteogenesis imperfecta (OI) to stabilize long bones, often post fracture. We speculated that a combination of intramedullary reaming and intraosseous injection of recombinant bone morphogenetic protein-2 (BMP-2) could enhance periosteal ossification and ultimately cortical thickness and strength. This approach was conceptually tested in a preclinical model of genetic bone fragility.MethodsSix experimental groups were tested including no treatment, intramedullary reaming, and reaming with 5 µg BMP-2 injection performed in the tibiae of both wild type (WT) and Col1a2G610C/+ (OI, Amish mutation) mice. Bone formation was examined at a two-week time point in ex vivo specimens by micro-computed tomography (microCT) analysis and histomorphometry with a dynamic bone label.ResultsMicroCT data illustrated increases in tibial cortical thickness with intramedullary reaming alone (Saline) and reaming plus BMP-2 injection (BMP-2) compared to no intervention controls. In the OI mice, the periosteal bone increase was not statistically significant with Saline but there was an increase of +192% (p = 0.053) with BMP-2 injection. Dynamic histomorphometry on calcein label was used to quantify new woven bone formation; while BMP-2 induced greater bone formation than Saline, the anabolic response was blunted overall in the OI groups.ConclusionsThese data indicate that targeting the intramedullary compartment via reaming and intraosseous BMP-2 delivery can lead to gains in cortical bone parameters. It is suggested that the next step is to validate safety and functional improvements in a clinical OI setting.

Intradural Extramedullary Spinal Sarcoidosis Mimicking Meningioma

Background Spinal sarcoidosis is a rare subgroup of neurosarcoidosis. Although most sarcoid lesions develop in the intramedullary compartment, intradural extramedullary (IDEM) spinal sarcoidosis is an extremely rare entity. Case Presentation We herein report a case of IDEM spinal sarcoidosis mimicking a meningioma. A 32-year-old man presented to the hospital with clumsy hands and was unable to walk without assistance. Magnetic resonance imaging (MRI) of the cervical spine revealed a dural tail sign that is common in meningiomas. The patient underwent gross total resection. The pathological findings consisted with a sarcoid leision of the spinal cord. The patient's myelopathy recovered after surgery. Conclusions Physicians should be alert for the possibility of IDEM sarcoidosis mimicking a meningioma in the differential diagnosis of IDEM spinal cord tumors.

Primary Spinal Astrocytomas: A Literature Review.

Primary spinal astrocytoma is a subtype of glioma, the most common spinal cord tumor found in the intradural intramedullary compartment. Spinal astrocytomas account for 6-8% of all spinal cord tumors and are primarily low grade (World Health Organization grade I (WHO I) or WHO II). They are seen in both the adult and pediatric population with the most common presenting symptoms being back pain, sensory dysfunction, or motor dysfunction. Magnetic Resonance Imaging (MRI) with and without gadolinium is the imaging of choice, which usually reveals a hypointense T1 weighted and hyperintense T2 weighted lesion with a heterogeneous pattern of contrast enhancement. Further imaging which may aid in surgical planning includes computerized tomography, diffusion tensor imaging, and tractography. Median survival in spinal cord astrocytomas ranges widely. The factors most significantly associated with poor prognosis and shorter median survival are older age at initial diagnosis, higher grade lesion based on histology, and extent of resection. The mainstay of treatment for primary spinal cord astrocytomas is surgical resection, with the goal of preservation of neurologic function, guided by intraoperative neuromonitoring. Adjunctive radiation has been shown beneficial and may increase overall survival. The role of adjunctive chemotherapy is employed, however, its benefit has not been clearly defined. Primary spinal cord astrocytomas are rare and challenging to treat. The gold standard treatment is surgical resection. Second-line treatments include radiation and chemotherapy, although, the optimal regimen for adjunctive therapy has not yet been clearly defined.

Resistance to Nutrient Deprivation Via Metabolic Re-Programming As Mechanism of ‘Metastasis’ Promotion in Multiple Myeloma

Aim: Multiple Myeloma (MM) is a disease of the intra-medullary (IM) compartment but with progression myeloma cells can survive in nutrient deprived extramedullary (EM) sites. Autophagy mediates the degradation and re-cycling of intra-cellular proteins and may promote tumor resistance to metabolic stressors, including nutrient deprivation. Using the MM cell lines TK1 and TK2, contemporaneously propagated from bone marrow (IM) and peripheral blood (EM), respectively, of a MM patient we investigated the role of autophagy in resistance to glutamine (Gln) deprivation.Methods & Results:TK2 but not TK1 exhibited up-regulated autophagy under both basal and Gln deprived conditions with higher LC3BII/I turnover on immunoblotting and autophagic vacuole formation on electron microscopy following chloroquine (CQ) exposure. Under conditions of Gln deprivation, TK2 was able to proliferate until day 14, whereas TK1 stopped proliferating at day 3. This proliferative advantage under Gln deprivation was abrogated by autophagy inhibitors (CQ or 3-MA) as determined by both viable cell enumeration (p=0.008 at day 7, inhibitor vs no inhibitor) and Ki67 expression (p=0.0017) only in TK2. Modulation of Gln concentration demonstrated an inverse correlation with the viability of TK1 but not TK2 - TK1 cell death increased from 36% at Gln 8mM to 56% at Gln 0mM, irrespective of autophagy inhibition. In contrast, while Gln deprivation had no significant effect on the viability of TK2, under Gln deprivation CQ exposure induced a 2-fold increase cell death measured by annexin V/PI positivity and 2.5-fold increase of cPARP expression (p=0.0045).RNAseq and GSEA analysis showed enrichment of the Krige Amino Acid Deprivation Response (AADR) pathway (ES=0.083) for TK1 with up-regulated expression of Gln transporters (SLC7A5, SLC1A5, SLC38A5 and SLC7A11). In contrast, Glutamine Synthetase (GS) expression, which is responsible for Gln synthesis, was up-regulated in TK2 cells. Interestingly, immunoblotting analysis revealed that Gln deprivation was able to induce the expression of GS while further inducing autophagic flux (2.66 fold increase of LC3II expression at Gln=0mM) only in TK2, whereas it inhibited mTOR activity in both cell lines. Additionally, GS chemical inhibition under Gln deprivation induced cell death in TK2 but not TK1 (32.56% vs 2.5% increase, respectively) demonstrating that Gln synthesis enables TK2 to overcome Gln deprivation.Conclusion. Metabolic reprogramming mitigating against nutrient deprivation may promote a more ‘metastatic’ phenotype in advanced MM. DisclosuresSpencer:Celgene: Honoraria, Research Funding, Speakers Bureau; Janssen-Cilag: Honoraria, Research Funding, Speakers Bureau; Amgen: Honoraria, Research Funding; BMS: Research Funding; Takeda: Honoraria, Research Funding, Speakers Bureau; STA: Honoraria.

The surgical treatment of metastatic spine tumors within the intramedullary compartment.

OBJECTIVE Metastasis to the spinal cord is rare, and optimal management of this disease is unclear. The authors investigated this issue by analyzing the results of surgical treatment of spinal intramedullary metastasis (IM) at a major cancer center. METHODS The authors retrospectively reviewed the medical records of 13 patients who underwent surgery for IM. Patients had renal cell carcinoma (n = 4), breast carcinoma (n = 3), melanoma (n = 2), non-small cell lung cancer (n = 1), sarcoma (n = 1), adenoid cystic carcinoma (n = 1), and cervical cancer (n = 1). Cerebrospinal fluid was collected before surgery in 11 patients, and was negative for malignant cells, as was MRI of the neuraxis. Eleven patients presented with neurological function equivalent to Frankel Grade D. RESULTS Radiographic gross-total resection was achieved in 9 patients, and tumor eventually recurred locally in 3 of those 9 (33%). Leptomeningeal disease was diagnosed in 4 patients after surgery. In the immediate postoperative period, neurological function in 6 patients deteriorated to Frankel Grade C. At 2 months, only 2 patients remained at Grade C, 8 were at Grade D, and 1 had improved to Grade E. One patient developed postoperative hematoma resulting in Frankel Grade A. Radiotherapy was delivered in 8 patients postoperatively. The median survival after spine surgery was 6.5 months. Three patients are still living. CONCLUSIONS Surgery was performed as a last option to preserve neurological function in patients with IM. In most patients, neurological function returned during the immediate postoperative period and was preserved for the patients' remaining lifetime. The data suggest that surgery can be effective in preventing further decline in selected patients with progressive neurological deficit.

Time-SLIP Reveals Intramedullary Flow in Syringomyelia

Case Presentation Magnetic resonance imaging (MRI) using a time-spatial labeling inversion pulse (Time-SLIP) method permits visualization of cerebrospinal fluid (CSF) dynamics noninvasively. Time-SLIP enables quantitative and qualitative CSF flow analysis without any limitations in flow velocity or direction. An 85-year-old old male: Syringomyelia (C7-T12) Conventional MRI revealed syringomyelia with multiple syrinx cavities. Time SLIP can detect the CSF flow dynamics in both the intra- and peri-spinal cord simultaneously. The basic CSF flow pattern in the syringomyelia cavity was pulsatile motion in the Cranio-caudal direction and harmonious with the flow in subarachnoid space (Figure 1). Time-SLIP also detected over flow through septum or web. The unique flow across the intramedullary compartments indicated several paths throughout the septum of syrinx (Figure 2). These findings may improve our understanding of disease pathology of syringomyelia and be useful in surgical planning MRI imaging technique 1.5-T MR imager with quadrature-detected phased-array coils Sphygmographic gated single-shot half Fourier fast spin-echo (FSE) sequence. Representative imaging parameters TR: 12−13P−P intervals, TE: 80 msec, BBTI: 1500-4400 msec (100 msec interval), Tag pulse thickness: 30 mm, ETS 6.5 msec, MTX: 256 × 288, FOV: 25 × 25 cm, Slice thickness 5 mm.

Infections of the Spinal Subdural Space in Children: A Series of 11 Contemporary Cases and Review of all Published Reports. A Multinational Collaborative Effort

Positioned anatomically between the spinal epidural space and the intramedullary compartment, the spinal subdural space remains the least common area of localized infection in the central nervous system. Infectious processes of the subdural spinal space include subdural spinal empyema, subdural spinal abscess, infected spinal subdural cyst, and infectious spinal subdural cyst. To date, there has been no systematic review of these entities in children, with the cumulative knowledge of the pathophysiologic, microbiologic, and demographic characteristics of these infections relegated solely to few small series and case reports. A series of 11 recent cases culled from the collaboration of international authors are presented. In addition, an exhaustive MEDLINE search and manual review of the international literature was performed, identifying a total of 73 cases of spinal subdural infections in patients under the age of 21. Data of interest include the age, sex, signs, and symptoms at presentation, spinal location of infection, presence of spinal dysraphism, and other comorbidities, offending organism, treatment, outcome, and follow-up. Patients ages ranged from 4weeks to 20years (mean, 6.5years). Males outnumbered females by a ratio of 2:1. Over half (53%) of spinal subdural infections in children were associated with spinal dysraphism or other congenital abnormalities of the spine. The commonest organism to infect the spinal subdural space in children is mycobacterium tuberculosis and the thoracic spinal region was most commonly infected. The disease is usually treated surgically, although a more expectant approach consisting of antibiotics and observation has also been proposed.

Microfluidic enhancement of intramedullary pressure increases interstitial fluid flow and inhibits bone loss in hindlimb suspended mice

Interstitial fluid flow (IFF) has been widely hypothesized to mediate skeletal adaptation to mechanical loading. Although a large body of in vitro evidence has demonstrated that fluid flow stimulates osteogenic and antiresorptive responses in bone cells, there is much less in vivo evidence that IFF mediates loading-induced skeletal adaptation. This is due in large part to the challenges associated with decoupling IFF from matrix strain. In this study we describe a novel microfluidic system for generating dynamic intramedullary pressure (ImP) and IFF within the femurs of alert mice. By quantifying fluorescence recovery after photobleaching (FRAP) within individual lacunae, we show that microfluidic generation of dynamic ImP significantly increases IFF within the lacunocanalicular system. In addition, we demonstrate that dynamic pressure loading of the intramedullary compartment for 3 minutes per day significantly eliminates losses in trabecular and cortical bone mineral density in hindlimb suspended mice, enhances trabecular and cortical structural integrity, and increases endosteal bone formation rate. Unlike previously developed modalities for enhancing IFF in vivo, this is the first model that allows direct and dynamic modulation of ImP and skeletal IFF within mice. Given the large number of genetic tools for manipulating the mouse genome, this model is expected to serve as a powerful investigative tool in elucidating the role of IFF in skeletal adaptation to mechanical loading and molecular mechanisms mediating this process. © 2010 American Society for Bone and Mineral Research.

Extraarticular proximal-tibial fractures——Treatment with intramedullary nail versus plate fixation

Limited, poor evidence is available for comparing the treatment of extraarticular proximal tibial fractures by intramedullary nail or plate fixation. There was no difference in the rates of nonunion for either treatment. Significantly less patients treated by intramedullary nailing experience infection than patients treated by plating, whereas more patients treated by intramedullary nailing experienced malunion or compartment syndrome than those treated by intramedullary nailing. Implant failure occurred only in patients treated by intramedullary nailing. However,definitive conclusions cannot be drawn from this collection of case-series and a well-conducted prospective or randomized controlled trial would be a significant addition to this subject. 比较髓内钉与钢板内固定治疗胫骨近端关节外骨折的研究很少,且质量较低.两种方法发生骨折不愈合的几率无差异.与钢板内固定相比,髓内钉治疗的患者感染发生率较低,但是骨折畸形愈合和筋膜室综合征的发生率较高.采用髓内钉治疗的患者有内固定失败的报道.通过目前的病例报道,暂时不能得出确切的结论,所以应进一步做前瞻性或随机对照研究来说明该问题.……

Histopathologic, Immunohistochemical, and Cytologic Analysis of Feline Myeloma-Related Disorders: Further Evidence for Primary Extramedullary Development in the Cat

Feline myeloma-related disorders (MRD) are rare neoplasms of plasma cells. The multistep transformation model of myeloma in humans is based on the premise that plasma cells undergo neoplastic transformation primarily within the intramedullary compartment and that over time they become poorly differentiated and metastasize to extramedullary locations. Historically, diagnostic criteria used for human multiple myeloma have been applied to the cat, with the assumption that feline MRD commonly arises in the intramedullary compartment. Our objectives were to describe the features of feline MRD confirmed by cytology, histopathology, histochemistry, and immunohistochemistry and to categorize these tumors. A priori hypotheses were 1) tumor category predicts survival and 2) cats with well-differentiated tumors commonly have extramedullary involvement in contrast to human myeloma patients. This multicenter, retrospective study identified 26 MRD cases. There was good agreement between histopathologic and cytologic tumor categorization. Histochemistry and immunohistochemistry were shown to be valuable adjunct tests in the diagnosis of MRD. Cats with well-differentiated tumors had increased median survival relative to those with poorly differentiated tumors (254 versus 14 days). We have reported that marked extramedullary involvement at initial clinical presentation is significantly more common in the cat than in human MRD patients. In this study, we demonstrate that cats with well-differentiated tumors more commonly have extramedullary involvement than human myeloma patients with well-differentiated tumors (90% versus 20%, P < 0.0002). These results contrast strongly with the human myeloma model of primary intramedullary neoplastic transformation and suggest that primary extramedullary neoplastic transformation may be more common in feline MRD.

Spinal infections

Spinal infections have an increasing prevalence among the general population. Definitive diagnosis based solely on clinical grounds is usually not possible and radiological imaging is used in almost all patients. The primary aim of the authors is to present an overview of spinal infections located in epidural, intradural and intramedullary compartments and to provide diagnostic clues regarding different imaging modalities, particularly MRI, to the practicing physicians and radiologists.

Use of gadolinium chelates in MR imaging of the spine.

Spinal disease can be divided into intramedullary, extramedullary-intradural, and extradural compartments. In the cord (intramedullary compartment), gadolinium chelates are useful to diagnose primary and metastatic tumors, inflammation, and demyelination, and to evaluate syringomyelia when a Chiari I malformation is not present. In the extramedullary-intradural compartment, gadolinium chelates are useful for the diagnosis of drop metastases, meningiomas, and schwannomas. In the extradural compartment, gadolinium chelates are most useful to distinguish recurrent disc herniation from epidural fibrosis in the postoperative back and may be useful to diagnosis the soft tissue component of osseous metastases.

Classification of histopathologic changes following chemotherapy in Ewing's sarcoma of bone.

A uniform classification of response to chemotherapy is essential to allow comparison of local effect and ultimate prognosis between different therapy schedules. We define a histological grading system for assessment of the response to chemotherapy in Ewing's sarcoma, based on the amount and architectural pattern of residual histologically viable-appearing tumour, the preferential sites of minimal residual tumour and the amount of tumour necrosis. Twenty-six consecutive patients with a biopsy-proven Ewing's sarcoma were treated with chemotherapy prior to surgery. The effect of chemotherapy was evaluated microscopically on the specimens obtained after surgery. Response to chemotherapy was classified as minimal or no effect (< 10% tumour necrosis), moderate effect (solid areas of remnant viable tumour), minimal residual disease, and no evidence of disease (100% tumour necrosis or well-vascularized fibrous tissue). The subperiosteal area in particular and, less frequently, soft tissues and intramedullary compartment were identified as sites of predilection for persistence of microscopic viable tumour foci, frequently depicted as pseudo-rosettes in a characteristic scattered pattern. Although it is not well known whether morphological viability of these residual clusters in Ewing's sarcoma indicates biological viability, accurate preoperative local staging, with special attention to preferential sites of residual viable tumour, is essential. The proposed grading system can be used to standardize assessment of chemotherapy in trials, and may serve as a standard for non-invasive monitoring of preoperative chemotherapy with magnetic resonance imaging.

Clinical Experience With Gadolinium Contrast Agents in Spinal MR Imaging

Gadolinium contrast agents represent one of the most important advances in MR imaging of spinal disease. Many abnormalities that affect the epidural, intradural extramedullary, and intramedullary compartments demonstrate contrast enhancement, the pattern of which often provides specific diagnostic information. This is particularly true of neoplastic diseases such as primary glioma and leptomeningeal tumor spread. Gadolinium contrast also finds vital application in differentiating herniated disc from epidural fibrosis in the failed-back surgery syndrome, as well as hypointense disc from enhancing tumor in select cases. Certain demyelinating and inflammatory processes also have predictable MR manifestations that facilitate accurate diagnosis.