Temporal evolution of spinal cord infarction in an in vivo experimental study of canine models characterized by diffusion-weighted imaging

Diffusion-Weighted Imaging Findings of Ischemic Spinal Injury in a Chondrodystrophic Dog With Fibrocartilaginous Embolism

A 9-year-old, intact male Shih Tzu dog presented with systemic weakness and peracute onset of tetraplegia. Tetraplegia with lower motor neuron signs was noted upon neurological examination. Diseases that cause acute flaccid tetraparesis, such as acute fulminating myasthenia gravis, polyradiculoneuritis, tick paralysis, and botulism, were ruled out based on the medical history, normal electrophysiological tests, and non-response to the neostigmine challenging test. Initial 0.3-Tesla (T) magnetic resonance imaging (MRI) findings included sharply demarcated intramedullary lesions at the C3-C6 level, mainly involving gray matter, which appeared hypo- to iso- intense on T1-weighted images (WIs), and hyperintense on T2-WIs and fluid-attenuated inversion recovery images. There was no enhancement on post-contrast T1-WIs. Neutrophilic pleocytosis was observed in the cerebrospinal fluid analysis. No clinical responses were observed for the treatment of non-infectious myelitis with an immunosuppressive dosage of prednisolone. A follow-up 3-T MRI 6 days later demonstrated hyperintensity on diffusion-WI (DWI) and a decreased apparent diffusion coefficient (ADC) value (0.54 × 10^-3 mm²/s) of the spinal lesions. Through histological examination, a fibrocartilaginous embolism was definitively confirmed. This is the first report to describe an ischemic spinal injury visualized by DWI and ADC mapping with high-field MRI in a chondrodystrophic dog diagnosed with a fibrocartilaginous embolism.

Reduced field-of-view diffusion-weighted MRI can identify restricted diffusion in the spinal cord of dogs and cats with presumptive clinical and high-field MRI diagnosis of acute ischemic myelopathy

Diffusion-weighted imaging MRI is the gold standard imaging technique for diagnosis of suspected acute brain ischemia in dogs and cats; however, it is technically challenging to apply to spinal cord imaging, due to its very small size, the inherent low spatial resolution of diffusion-weighted imaging, and the marked distortion resulting from magnetic field inhomogeneities caused by the osseous components of the vertebral column surrounding the spinal cord. Ischemic myelopathy is a common cause of acute non-compressive myelopathy in dogs and cats. Technological improvement in diffusion-weighted imaging pulse sequences allow imaging at smaller field of view with better spatial resolution and less image distortion. We sought to evaluate reduced field-of-view diffusion-weighted imaging MRI using a dedicated proprietary pulse sequence (FOCUS, General Electric) in a small sample of dogs and cats with a presumptive clinical and MRI diagnosis of acute ischemic myelopathy that were imaged with this pulse sequence. Five dogs and two cats fitted these inclusion criteria. In all of them, hyperintense spinal cord parenchyma signal was seen on diffusion-weighted imaging images corresponding to decreased signal on apparent diffusion coefficient map indicative of restricted diffusion, consistent with ischemia and cytotoxic edema. These areas matched the areas of abnormal T2-weighted signal and cord swelling observed on conventional spinal MRI. This small exploratory descriptive study indicates feasibility and possible usefulness of reduced field-of-view diffusion-weighted imaging MRI in dogs and cats with suspected acute ischemic myelopathy and that it may be added to the imaging protocol of the spine in such patients in an appropriate clinical setting.

Multimodal analysis of the effects of dexamethasone on high-altitude cerebral oedema: protocol for a pilot study

Background

Acute mountain sickness (AMS) is a cluster of symptoms that commonly occur in those ascending to high altitudes. Symptoms can include headaches, nausea, insomnia and fatigue. Exposure to high altitude can also lead to high-altitude cerebral oedema (HACE), which is a potential cause of death whilst mountaineering. Generally, AMS precedes the development of HACE. Historical studies have demonstrated the effectiveness of regular dexamethasone administration in reducing the symptoms of AMS. However, the mechanism by which dexamethasone works to reduce symptoms AMS remains poorly understood. Further studies, simulating altitude using hypoxic tents, have characterised the effect of prolonged exposure to normobaric hypoxia on cerebral oedema and blood flow using MRI. This randomised trial assesses the effect of dexamethasone on hypoxia-induced cerebral oedema in healthy adult volunteers.

Methods/design

D4H is a double-blind placebo-controlled randomised trial assessing the effect of dexamethasone on hypoxia-induced cerebral oedema. In total, 20 volunteers were randomised in pairs to receive either 8.25 mg dexamethasone or normal saline placebo intravenously after 8 h of hypoxia with an FiO₂ of 12%. Serial MRI images of the brain and spinal cord were obtained at hours 0, 7, 11, 22 and 26 of the study along with serum and urinary markers to correlate with the severity of cerebral oedema and the effect of the intervention.

Discussion

MRI has been used to identify changes in cerebral vasculature in the development of AMS and HACE. Dexamethasone is effective at reducing the symptoms of AMS; however, the mechanism of this effect is unknown. If this study demonstrates a clear objective benefit of dexamethasone in this setting, future studies may be able to demonstrate that dexamethasone is an effective therapy for oedema associated with brain and spinal cord ischaemia beyond AMS.

Trial registration

Clinicaltrials.gov, NCT03341676. Registered on 14 November 2017.

Spinal cord watershed infarction: Novel findings on magnetic resonance imaging

Spinal cord watershed ischemia is a rare phenomenon often associated with cardiac arrest, prolonged hypotension, and atherosclerotic disease. It can manifest as central necrosis with peripheral sparing in the transverse axis, and central lesion with rostral and caudal sparing in the longitudinal axis. Few reports provide detailed imaging findings of spinal cord watershed ischemia lesions. We present a patient who experienced watershed infarcts of the brain and spinal cord following prolonged hypotension due to blood loss after an aortic aneurysm repair. The patient experienced loss of neurologic function of the lower extremities and left arm that did not recover following spinal cord ischemia protocol. MRI revealed spinal cord watershed ischemia in both the longitudinal and axial planes with the point of maximal T2 signal hyperintensity in the central cord at T10-T11. Unique findings included zones of central maximal T2 signal hyperintensity with peripheral sparing, and moderate T2 intensity representing partial ischemia between regions of maximal T2 intensity unaffected peripheral regions. Thoracoabdominal computed tomography angiogram revealed extensive intraluminal thrombus and bilateral spinal artery occlusion from T8 to L2 and bilateral severe renal artery stenosis. T7 and L3 spinal arteries were patent. We suspect preexisting atherosclerotic disease played a significant role in the development of widespread watershed lesions following prolonged hypotension and resulted in a clinical and imaging presentation distinct from that seen with isolated anterior spinal artery occlusion. Our unique MRI findings portray a rarely documented pattern of spinal cord watershed ischemia and prompt questions about the role of anatomic idiosyncrasies and preexisting vascular disease in the development of spinal cord watershed ischemia.

Diagnostic and Prognostic Relevance of Magnetic Resonance Imaging and Electrophysiological Findings in Acute Spinal Ischemia

OBJECTIVE

Our purpose was to classify the rare entity of spontaneous spinal ischemia with clinical, magnetic resonance-tomographic, and electrophysiological parameters to determine criteria for outcome prediction.

METHODS

We analyzed the stroke registry database of the University Hospital Mannheim, Germany, from 2004 to 2010 for patients with a diagnosis of vascular spinal cord ischemia.

RESULTS

Ten patients were identified (mean age 65 years [range 50-83], 5 women). In 5 patients an etiology was found. Spinal diffusion-weighted magnetic resonance imaging revealed acute ischemia in 7 patients at initial imaging and this diagnosis was confirmed during the first week in the remaining 3 patients. Electrophysiological studies showed abnormal motor evoked potentials (MEPs) in 8 patients and abnormal somatosensory evoked potentials (SSEPs) in 7 patients. After rehabilitation, 5 patients had regained walking ability, whereas 5 patients stayed wheelchair bound. All patients with unfavorable outcome (American Spinal Injury Association (ASIA) Impairment score [AIS] score of ≤C) showed severe pyramidal tract lesions in MEPs during the first week. All patients with normal MEPs had an excellent outcome (AIS of E, P < .05).

CONCLUSIONS

Diffusion-weighted imaging (DWI) is a useful tool to confirm acute spinal ischemia suspected in patients within the first days after symptom onset. Poor outcome was associated with severe electrophysiological abnormalities in MEPs and SSEPs. Normal MEPs were significantly predictive of an excellent prognosis. A multimodal diagnostic approach combining DWI and electrophysiological evaluation facilitates the prediction of the individual clinical outcome.

A Review of Fibrocartilaginous Embolic Myelopathy and Different Types of Peracute Non-Compressive Intervertebral Disk Extrusions in Dogs and Cats

This review discusses terminology, pathological, clinical, and magnetic resonance imaging (MRI) findings, treatment, outcome, and prognostic factors of fibrocartilaginous embolic myelopathy (FCEM), acute non-compressive nucleus pulposus extrusion (ANNPE), and intradural/intramedullary intervertebral disk extrusion (IIVDE). FCEM, ANNPE, and IIVDE have a similar clinical presentation characterized by peracute onset of neurological dysfunction that is generally non-progressive after the initial 24-48 h. Differentiating between these conditions can be challenging, however, certain clinical and imaging findings can help. FCEM can occur in both adult and immature animals, whereas ANNPE or IIVDE have been reported only in animals older than 1 year. In dogs, ANNPE and IIVDE most commonly occur in the intervertebral disk spaces between T12 and L2, whereas FCEM has not such site predilection. In cats, FCEM occurs more frequently in the cervical spinal cord than in other locations. Data on cats with ANNPE and IIVDE are limited. Optimal MRI definition and experience in neuroimaging can help identify the findings that allow differentiation between FCEM, ANNPE, and IIVDE. In animals with ANNPE and IIVDE, the affected intervertebral disk space is often narrowed and the focal area of intramedullary hyperintensity on T2-weighted images is located above the affected intervertebral disk space. In dogs with ANNPE signal changes associated with the extruded nucleus pulposus and epidural fat disruption can be identified in the epidural space dorsal to the affected intervertebral disk. Identification of a linear tract (predominantly hyperintense on T2-weighted images, iso to hypointense on T1-weighted images and hypointense on T2*-weighted gradient recall echo images) extending from the intervertebral disk into the spinal cord parenchyma is highly suggestive of IIVDE. Treatment of FCEM and ANNPE is conservative. Dogs reported with IIVDE have been managed either conservatively or surgically. Prognostic factors include degree of neurological dysfunction (particularly loss of nociception) and disease-specific MRI variables.

Multishot diffusion-weighted MR imaging features in acute trauma of spinal cord

OBJECTIVES

To analyse diffusion-weighted MRI of acute spinal cord trauma and evaluate its diagnostic value.

METHODS

Conventional MRI and multishot, navigator-corrected DWI were performed in 20 patients with acute spinal cord trauma using 1.5-T MR within 72 h after the onset of trauma.

RESULTS

Twenty cases were classified into four categories according to the characteristics of DWI: (1) Oedema type: ten cases presented with variable hyperintense areas within the spinal cord. There were significant differences in the apparent diffusion coefficients (ADCs) between lesions and unaffected regions (t = -7.621, P < 0.01). ADC values of lesions were markedly lower than those of normal areas. (2) Mixed type: six cases showed heterogeneously hyperintense areas due to a mixture of haemorrhage and oedema. (3) Haemorrhage type: two cases showed lesions as marked hypointensity due to intramedullary haemorrhage. (4) Compressed type (by epidural haemorrhage): one of the two cases showed an area of mild hyperintensity in the markedly compressed cord due to epidural haematoma.

CONCLUSIONS

Muti-shot DWI of the spinal cord can help visualise and evaluate the injured spinal cord in the early stage, especially in distinguishing the cytotoxic oedema from vasogenic oedema. It can assist in detecting intramedullary haemorrhage and may have a potential role in the evaluation of compressed spinal cord.

KEY POINTS

• Multishot, navigator-corrected diffusion-weighted MRI is helpful when evaluating spinal cord injury (SCI). • Four types of SCI may be classified according to the DWI characteristics. • DWI differentiates cytotoxic from vasogenic oedema, thereby determining the centre of SCI. • DWI can assist in detecting intramedullary haemorrhage. • DWI can help evaluate the degree of compressed spinal cord.

Fibrocartilaginous embolic myelopathy in small animals

Fibrocartilaginous embolic myelopathy (FCEM) typically results in peracute onset of nonpainful, nonprogressive (after the first 24 hours), and often asymmetric neurologic deficits. Definitive diagnosis can be reached only through histologic examination of the affected spinal cord segments. Although MRI is the preferred diagnostic imaging modality for the antemortem diagnosis of FCEM, it may not show any changes in the first 24 to 72 hours of disease. Severity of neurologic signs at initial examination and extent of the lesions seen on MRI can help predict outcomes in dogs with FCEM.

Diffusion-weighted imaging, diffusion-tensor imaging, and fiber tractography of the spinal cord

In the brain, diffusion-weighted imaging (DWI) is an established and reliable method for the characterization of neurologic lesions. Although the diagnostic value of DWI in the early detection of ischemia has not diminished with time, many new clinical applications of DWI have also emerged. Diffusion-tensor imaging and fiber tractography have more recently been developed and optimized, allowing quantification of the magnitude and direction of diffusion along three principal eigenvectors. Diffusion-tensor imaging and fiber tractography are proving to be useful in clinical neuroradiology practice, with application to several categories of disease, and to be a powerful research tool. This article describes some of the applications of DWI and diffusion-tensor imaging in the evaluation of the diseases of the spinal cord.