Magnetic resonance imaging of experimental subacute spinal cord compression.

To determine whether there is an association between the degree of transverse spinal cord compression detected by magnetic resonance imaging following thoracolumbar Hansen type 1 intervertebral disc disease in dogs and their presenting and postsurgical neurological status. Medical records of 67 dogs with surgically confirmed Hansen type 1 intervertebral disc disease (2000 to 2004) were reviewed to obtain the rate of onset of disease, duration of clinical signs and presurgical and postsurgical neurological grade. Percentage of spinal cord compression was determined on transverse T2-weighted magnetic resonance images. Linear regression was used to examine the association between spinal cord compression and each of the above variables. Chi-squared tests were used to examine associations among postsurgical outcome and presurgical variables. Eighty-five per cent (57 of 67) of dogs were chondrodystrophoid. Mean spinal cord compression was 53 per cent (sd=219.7, range 14.3 to 84.9 per cent). There was no association between the degree of spinal cord compression and the neurological grade at presentation, rate of onset of disease, duration of clinical signs or postsurgical outcome, with no difference between chondrodystrophoid and non-chondrodystrophoid dogs. The degree of spinal cord compression documented with magnetic resonance imaging in dogs with thoracolumbar Hansen type 1 intervertebral disc disease was not associated with the severity of neurological signs and was not a prognostic indicator in this study.

Predictive effect of cervical spinal cord compression and corresponding segmental paravertebral muscle degeneration on the severity of symptoms in patients with cervical spondylotic myelopathy

To assess influence of durotomy on spinal cord blood flow (SCBF) in chondrodystrophic dogs with thoracolumbar disk extrusion. Prospective cohort study. Chondrodystrophic dogs with thoracolumbar disk extrusion (n = 11). Diagnosis was based on neurologic signs, magnetic resonance imaging (MRI) findings, and surgical confirmation. Regional SCBF was measured 3 times intraoperatively by laser-Doppler flowmetry: (1) before surgical decompression; (2) immediately after decompression by hemilaminectomy-durotomy; and (3) after 15 minutes of lesion lavage. A standardized hemilaminectomy and durotomy performed by the same neurosurgeon, was used to minimize factors that could influence measurement readings. A significant increase in intraoperative SCBF was found immediately after spinal cord decompression and durotomy in dogs but SCBF returned to previous levels or lower after 15 minutes of lavage. Changes in SCBF were not associated with duration of clinical signs; neurologic status, degree of spinal cord compression, or signal intensity changes as assessed by MRI. Durotomy does not increase SCBF in dogs with disk extrusion associated spinal cord compression.

Retrospective analysis of kinematic magnetic resonance images. To provide baseline data on the segmental angular and translational motion of the degenerated cervical spine by subtype of kyphotic cervical deformity and to elucidate the relationship between motion and degree of spinal cord compression. Kyphotic deformities of the cervical spine are relatively common and are classified as either global or focal. Nevertheless, the effects of kyphotic subtype on cervical segmental motion and degree of spinal cord compression are unknown. A total of 1171 symptomatic patients (618 females, 553 males) underwent cervical kinematic magnetic resonance imaging in the neutral, flexion, and extension positions. Cervical spines demonstrating kyphosis were included and classified into 3 groups: (1) "global kyphotic deformity" (C-type) (n = 54); (2) "sigmoid deformity" (S-type) with kyphotic upper and lordotic lower cervical segments (n = 29); and (3) "reverse sigmoid deformity" (R-type) with lordotic upper and kyphotic lower cervical segments (n = 39). Translational motion, angular motion, and degree of spinal cord compression were evaluated for each cervical level along with the changes associated with flexion and extension. In the C- and R-types, angular motion with extension was increased in the upper cervical spine, where there was kyphosis; when compared with the S-type, in which there was lordosis in the upper segments. The results were opposite for flexion angular motion. R-type displayed more translational motion at C3-C4 and C5-C6. Degree of static spinal cord compression of R-type was higher than the others at C3-C4. The dynamic spinal cord compression increased in extension more than flexion in all subtypes. Cervical spine studies that aim to investigate kyphotic deformities should make efforts to discern the different subtypes of kyphotic deformities to more accurately characterize and study the effects that the sagittal alignment has on the kinematics of the spine and the degree of spinal cord compression.

Retrospective study. Few studies have reported a relationship between central motor conduction time (CMCT), which evaluates corticospinal function, and degree of spinal cord compression in patients with myelopathy. Thus, there is no consensus on predicting the degree of prolonged CMCT on the basis of the degree of spinal cord compression. If a correlation exists between CMCT and spinal cord compression, then spinal cord compression may be a useful noninvasive clinical indicator of corticospinal function. Therefore, this study evaluated the relationship between CMCT and cervical spinal cord compression measured by magnetic resonance imaging (MRI) in patients with cervical spondylotic myelopathy (CSM). Hiroshima University Hospital in Japan. We studied 33 patients undergoing laminoplasty. Patients exhibited significant cervical spinal cord compression on both MRI and intraoperative electrophysiological examination. We assessed transcranial magnetic stimulation measurement of CMCT; spinal cord compression parameters such as area, lateral diameter, anteroposterior diameter and flattening of the spinal cord at the lesion site and C2/3 levels on MRI; and pre- versus postoperative Japanese Orthopaedic Association (JOA) scores. Correlations between CMCT and flattening as well as anteroposterior diameter of the spinal cord at the lesion level were observed. Strong correlations between CMCT and the ratio of the flattening and anteroposterior diameter parameters at the lesion level to that at the C2/3 level were also observed. Measurement of spinal cord compression may be useful for the evaluation of corticospinal function as a proxy for CMCT in patients with CSM.

Cervical spondylotic amyotrophy (CSA) is a relatively rare disorder. This study was conducted to elucidate the prognosis of proximal-type CSA after anterior decompressive surgery by evaluating clinical factors and imaging findings. Anterior decompressive surgery was performed in 40 patients with proximal-type CSA between March 2000 and December 2011. Patients were classified into 2 categories based on axial T2-weighted magnetic resonance imaging (MRI) findings: "nerve root compression (NRC)", with nerve root compressed at the intervertebral foramen, and "spinal cord compression (SCC)" with spinal cord compressed at the medial or paramedial site of spinal canal. Manual muscle testing (MMT) was used to evaluate the surgical effect. Scapular, deltoid, and biceps brachii muscles of the affected side were tested and the sum scores were calculated. Clinical factors and imaging findings, such as age, duration of disease, preoperative MMT grade, number of affected levels and signal intensity changes of spinal cord, were collected to analyze prognostic factors. After anterior decompressive surgery, 30 patients (75%) showed an improvement. NRC was observed in 6 patients and SCC in the rest 34 patients based on MRI findings. All patients (100%) with NRC had an improvement, while only 24 patients (70.6%) with SCC improved. In patients with SCC, there was a significant difference in duration of disease between patients who had an improvement and those who had not (P< 0.01). Anterior decompressive surgery is effective in the treatment of most patients with CSA. NRC on MRI may indicate a good surgical outcome. In patients with SCC, a long duration of disease is a risk factor for poor prognosis.

IntroductionAlthough magnetic resonance imaging (MRI) is an important modality for the diagnosis of metastatic spinal cord compression (MSCC), there are only a few reports on MSCC findings and symptoms after radiotherapy. We aimed to reveal the factors related to ambulatory function after treatment, including the MRI findings, in a prospective observational study.MethodsPatients with suspected MSCC who were treated with radiotherapy were included in this study. Orthopedic surgeons evaluated the neurological function according to the Frankel grade. All patients underwent spinal MRI, and the degree of spinal cord compression was assessed by a radiologist and a radiation oncologist using an MRI grading scale. One month after treatment, orthopedic surgeons reassessed the Frankel grade. Twenty-three patients who were evaluated 1 month after radiotherapy were included in the analysis.ResultsBefore radiotherapy, 17 patients were ambulatory and six were unable to walk. Furthermore, 13 patients were diagnosed with grade 3 compression on MRI (spinal cord compression with no cerebrospinal fluid seen on axial T2-weighted imaging). Patients with grade 3 MSCC were significantly more likely to be non-ambulatory at 1 month.ConclusionsThe MRI grading scale for MSCC may be a prognostic factor for ambulatory function after radiotherapy. MRI findings could aid in determining the indication for radiotherapy.

This was a retrospective case-control study. We aim to describe a novel 5-point grading system to determine the degree and severity of spinal cord compression secondary to a spinal epidural abscess (SEA). Secondarily, we aim to correlate the degree of compression with clinical presentation and outcomes. Mechanical compression plays an important role in the pathophysiology of neurological dysfunction in SEA. Unfortunately, no standardized classification system for describing the degree of spinal cord compression exists. The lack of a validated grading system makes it challenging to study and consistently report the relationship between cord compression and clinical presentation/outcomes in SEA. Patients 18 years and older admitted to our hospital system with a diagnosis of SEA located above the conus medullaris between 1993 and 2016 were included. Using pretreatment axial magnetic resonance images, we developed a 5-point classification scale to determine the degree of spinal cord compression. After assigning a compression grade to each abscess, we investigated the relationship between the degree of compression and presenting neurological symptoms. Furthermore, we assessed the association between compression grade and clinical outcomes. Three hundred thirty-nine patients were included in the study. Patients with high-grade cord compression (grades 4 and 5) were significantly more likely to present with pretreatment motor deficit, sensory changes, and bowel/bladder incontinence. With respect to clinical outcomes, increasing degree of compression was not associated with failure of nonoperative management, residual motor deficit, or 90-day mortality. We report a novel grading system for spinal cord compression in SEA with 5 progressively increasing grades of compression. High-grade abscesses with cord compression were significantly associated with neurological deficit at presentation but not with poor outcomes. We hope that this classification system will allow for greater consistency in reporting the association between cord compression and neurological deficit in SEA.

To find any differential magnetic resonance (MR) imaging findings between septic arthritis and transient synovitis in pediatric patients. The MR imaging findings in nine pediatric patients with septic arthritis and 14 with transient synovitis were retrospectively studied. The diagnoses were made by means of joint aspiration with bacteriologic study, arthrotomy, and clinical evaluation. MR imaging findings were analyzed with emphasis on the grade of joint effusion and alterations in signal intensity in the soft tissue and bone marrow of the affected hip joint. Signal intensity alterations in bone marrow (i.e., low signal intensity on fat-suppressed gadolinium-enhanced T1-weighted spin-echo images and high signal intensity on fat-suppressed T2-weighted fast spin-echo images) were seen in eight of nine patients with septic arthritis. These signal intensity alterations consisted of mild juxtaarticular changes in six patients without osteomyelitis and extensive changes in the femoral head and neck in two patients with coexistent osteomyelitis. Signal intensity alterations in bone marrow were not seen in the 14 patients with transient synovitis. Signal intensity alterations in the bone marrow of the affected hip joint are useful in the differentiation of septic arthritis from transient synovitis.

Fifty-seven magnetic resonance (MR) imaging examinations were obtained at 0.5 T in 19 patients before and after percutaneous ethanol injection (PEI) for 23 hepatocellular carcinoma (HCC) lesions less than 3.5 cm in diameter. Seventeen patients also underwent MR imaging 6 months after completion of therapy. In 11 patients, computed tomography was performed before and after treatment. After PEI, fine-needle biopsy specimens were obtained in all cases. Before treatment, HCC lesions had low signal intensity on T1-weighted images in 13 cases, had the same signal intensity as normal liver parenchyma in six, and had high signal intensity in four; all 23 tumors had high signal intensity on T2-weighted images. After treatment and at 6-month follow-up, all 21 lesions that contained no malignant cells at fine-needle biopsy had high signal intensity on T1-weighted images and had low signal intensity on T2-weighted images. The remaining two HCC lesions in which tumor necrosis was not achieved with PEI displayed a different MR pattern, since the residual neoplastic tissue showed no change in signal intensity on either T1- or T2-weighted images. The authors conclude that MR imaging may be useful for evaluating the effectiveness of PEI in achieving tumor regression.

Background:Atlanto-axial (AA) subluxation can be a complex syndrome in dogs. Accurate identification and assessment of this condition are key to providing treatment and resolution.Aim:The purpose of this retrospective study was to describe the magnetic resonance imaging (MRI) characteristics of AA subluxation and associated neurologic deficits. Methods:A multicenter review of dogs with a diagnosis of AA subluxation was conducted, evaluating signalment, neurologic grade, duration of signs, and MRI characteristics. MRI characteristics included degree of spinal cord compression and joint subluxation, integrity of odontoid ligaments, presence of a dens, spinal cord signal intensity, and presence of syringohydromyelia, hydrocephalus, and Chiari-like malformation. A control population with normal AA joints was also evaluated. MR images of 42 dogs with AA subluxation were compared to 26 age and breed-matched control dogs. Results:Affected dogs had a median age of 27 months and a median weight of 2.7 kg, and the most commonly affected breed was the Yorkshire terrier (47.5%). Spinal cord signal hyperintensity, increased AA joint size, and cross-sectional cord compression at the level of the dens and mid-body C2 were associated with AA subluxation. No associations were found between cord compression, the appearance of the dens, or cord signal intensity and neurologic grade. Affected dogs did not have a higher incidence of Chiari-like malformation, syringohydromyelia, or hydrocephalus than control dogs, and their neurologic grade was not associated with MRI findings. Lack of dens and/or odontoid ligaments was associated with larger subluxations. Conclusion:Dogs with clinical signs of AA subluxation were significantly more likely to have intramedullary hyperintensity at the level of compression ( p = 0.0004), an increased AA joint cavity size ( p = 0.0005), and increased spinal cord compression at the level of dens and mid-body C2 (p ≤ 0.05). The authors suggest an AA joint cavity size >1.4 mm and a subluxation distance >2.5 mm as cutoffs for MRI diagnosis of AA subluxation in dogs. No differences were noted between dogs with AA subluxation and control dogs regarding syringohydromyelia, hydrocephalus, and Chiari-like malformation.

To assess intrathecal pressure (ITP) in chondrodystrophic dogs with thoracolumbar disk extrusion. Prospective cohort study. Group 1: 11 chondrodystrophic dogs with thoracolumbar disk extrusion and present deep pain sensation. Group 2 (control): 3 healthy chondrodystrophic laboratory dogs without spinal disease. Diagnosis was based on neurologic signs, magnetic resonance imaging (MRI) findings, and surgical confirmation. Blood pressure was maintained within physiologic range during anesthesia. A standardized surgical procedure was applied to minimize factors that could influence measurement readings. An extended hemilaminectomy was performed and ITP was measured with a fiber optic catheter. The catheter was inserted in the subarachnoid space 1 spinal segment caudal to the level of herniation and its tip was advanced to the site of compression. Significantly higher ITP occurred in chondrodystrophic dogs with acute thoracolumbar disk disease compared with controls. ITP was not associated with duration of clinical signs, neurologic status, outcome, degree of spinal cord compression, or signal intensity changes as assessed by MRI. Acute thoracolumbar disk disease leads to elevated ITP in chondrodystrophic dogs, which may contribute to increased compression of spinal cord parenchyma.

The mechanisms of injury in spinal cord injury in dogs are similar to those in human patients and the dog is considered to be a valuable translational model for new treatment modalities. Studies regarding the quantitative characteristics of magnetic resonance imaging (MRI) findings in spinal cord injury in a uniform cohort of patients are lacking. The aim of this retrospective study was to evaluate the quantitative MRI signal characteristics of the spinal cord in T2-weighted (T2W) sequences, degree of spinal cord compression, and functional outcome in paraplegic dogs with thoracolumbar disk herniation proving the usefulness of imaging before treatment studies. MR images of 63 paraplegic dogs with intact or absent deep pain perception due to thoracolumbar disk herniation examined between January 2005 and June 2009 were reviewed blinded to clinical information. The presence and degree of spinal cord compression, and the presence and length of an intramedullary hyperintensity on T2W images were correlated to clinical signs and outcome. A statistically significant correlation was seen between the neurological status before surgery and the presence and extent of the intramedullary hyperintensity adjacent to the disk herniation in T2W sequences. In dogs with a longer duration of clinical signs, the degree of spinal cord compression was statistically significantly higher. The extent of hyperintensity and the degree of spinal cord compression presented a positive correlation, whereas improvement in the neurological score for each grade was faster with no or a smaller size of T2W intramedullary hyperintensity. In conclusion, a direct correlation between neurological status and MRI signal intensity and extent was proven. Moreover, the presence and extent of T2W hyperintensity can help determine the prognosis before surgery and to decide, whether new therapeutical strategies in dogs as a translational model should be evaluated.

There is a lack of information regarding magnetic resonance imaging (MRI) features of polyostotic vertebral lesions in dogs. The aim of this retrospective study was to identify and differenciate low-field MRI features of aggressive versus benign multifocal vertebral diseases in dogs. MRI examinations from 49 dogs with polyostotic vertebral lesions were reviewed. Images were evaluated for vertebral intensity changes, expansile lesions, new bone formation, cortical bone interruption, paravertebral musculature changes, lymphadenomegaly, spinal cord compression and spinal cord signal changes. Twenty-nine dogs with non-aggressive bone lesions and 20 dogs with aggressive vertebral lesions were included. Non-aggressive lesions had variable T2-weighted fast spin-echo (T2W) signal intensity and the majority displayed low signal intensity on short tau inversion recovery (STIR). Aggressive lesions predominantly had high T2W and STIR signal intensity, with variable signal intensity on T1-weighted spin-echo and contrast enhancement. Aggressive lesions were associated with spinal pain (p < 0.01), new bone formation (p = 0.02), spinal cord compression (p < 0.01) and lymphadenomegaly (p < 0.01). Cortical interruption (p < 0.01) and paravertebral musculature changes (p < 0.01) were the strongest indicative imaging features for aggressive lesions. Spinal pain, spinal cord compression, new bone formation, lymphadenomegaly and especially cortical interruption and paravertebral musculature signal intensity changes were the best discriminators for differentiating malignant from benign vertebral lesions.

Purpose: To determine the magnetic resonance imaging (MRI) findings and natural history of cerebral fat embolism in a cat model, and to correlate the MRI and histologic findings. Materials and Methods: Using the femoral arterial approach, the internel carotid artery of 11 cats was injected with 0.1 ml of triolein. T2-weighted (T2WI), T1-weighted (T1WI) and Gd-enhanced T1-weighted (Gd-T1WI) images were obtained serially at 2 hours, 1 and 4 days and 1, 2 and 3 weeks after embolization. Any abnormal signal intensity (SI) was evaluated. After MR imaging at 3 weeks, brain tissue was obtained for light microscopic (LM) examination using hematoxylin-eosin and Luxol fast blue staining, and for electron microscopic (EM) examination. The histologic and MRI findings were correlated. Results: At 2 hours, lesions showed high SI at T2WI, iso- or low SI at T1WI, and strong enhancement at Gd-T1WI. The high SI seen at T2WI decreased thereafter, and most lesions became iso-intense. At week 3, however, small focal areas of high SI were seen in the grey matter of eight cats and in the white matter of three. The low SI noted at acute-stage T1W1 subsequcntly became normal, though in the areas in which T2W1 had depicted high SI, focal areas of low SI remained. Lesion enhancement demonstrated by Gd-T1WI decreased continuously from day 1, and at week 3, weak enhancement was seen at the margin of the remained hypointense lesions in the gray matter in five cats. At LM examination with hematoxylin-eosin staining revealed normal histologic findings in the greater park of an embolized lesion. Cystic change was observed in the gray matter of eight cats, and in the gray and white matter of three of the eight. At LM examination, Luxol fast blue, staining demonstrated demyelination around the cystic change occurring in the white matter, and EM examination of the embolized cortex revealed sporadic intracapillary fat vacuoles (n=11) and disruption of the blood-brain barrier (n=4). Most lesions were normal, however, and perivascular interstitial edema and cellular swelling were mild compared with the control side. Conclusion: Experimental cerebral fat embolism was clearly demonstrated by T2WI and Gd-T1WI images obtained at all time points. The greater part of an embolized lesion showed reversible findings at MR and histologic examination; irreversible focal necrosis was, however, observed in gray and white matter at week 3.