Imaging diagnosis--degenerative intraspinal cyst associated with an intervertebral disc

Thoracolumbar hydrated nucleus pulposus extrusion and intervertebral disc extrusion in dogs: Comparison of clinical presentation and magnetic resonance imaging findings

Thoracolumbar hydrated nucleus pulposus extrusion (TL-HNPE) is an increasingly recognised pathology with a substantial lack of literature describing its features. The aim of this retrospective case-control study was to analyse the clinical and magnetic resonance imaging (MRI) features of dogs with TL-HNPE compared to dogs affected with thoracolumbar intervertebral disc extrusion (TL-IVDE). Data from dogs diagnosed with TL-HNPE and TL-IVDE via MRI at two referral hospitals, were retrospectively collected and compared in terms of clinical signs and MRI features. Cases diagnosed with TL-IVDE were deemed controls. The MRI features of the affected IVD space, herniated IVD material, affected overlying spinal cord and local epaxial musculature were evaluated for each group. Fifty-one cases with TL-HNPE and 105 randomly selected cases of TL-IVDE were included. Several signalment and neurological signs were identified as statistically distinct between groups in univariate analysis. Multivariate analysis identified that dogs affected with TL-HNPE were typically older, less likely to be chondrodystrophic (62.2 % vs. 91 %), more frequently experiencing a peracute onset (90.2 % vs. 61.9 %) often attributed to a suspected trauma linked with exercise (37.3 % vs. 10.5 %), being less frequently progressive (41.2 % vs. 86.5 %) and with herniated disc material less frequently lateralised (72.6 % vs. 89.5 %) than cases with TL-IVDE. MRI-identifiable intervertebral disc degeneration was found in every TL-IVDE case but only in 60 % of TL-HNPE cases. TL-HNPEs were associated to significantly less spinal cord compression and less hyperalgesia than TL-IVDE.

Myelo-CT imaging findings in 15 dogs with surgically-treated cervical acute compressive hydrated nucleus pulposus extrusion

Compressive hydrated nucleus pulposus extrusion (HNPE) is a sudden extrusion of hydrated, nondegenerated nucleus pulposus material with well-known characteristic MRI findings. The appearance of compressive HNPE during contrast-enhanced CT has already been described, but never its myelo-CT characteristics. The aim of this retrospective multicenter case series is to describe the myelo-CT findings in 15 dogs with compressive HNPE confirmed with gross surgical findings. A distinctive and consistent myelo-CT appearance of cervical compressive HNPE in dogs that included a focal extradural "seagull"-shaped extradural compression dorsal to the annulus fibrosus combined with a narrowing of the affected intervertebral disc space was found. The extruded material was hypoattenuating in the soft tissue algorithm. Myelo-CT could be a useful diagnostic tool and influence the clinical decision to address cervical compressive HNPE conservatively or surgically when MRI is not available.

Clinical, magnetic resonance imaging and histologic findings of canine thoracolumbar discal pseudocyst: 8 cases (2014-2019)

OBJECTIVE

To report the clinical and MRI features, and histologic findings of thoracolumbar discal pseudocyst in dogs.

MATERIALS AND METHODS

The records of eight dogs with thoracolumbar discal cyst-like structures were retrospectively collected to record their clinical signs, MRI features and surgical and histologic findings.

RESULTS

Eight dogs with surgically and histologically confirmed thoracolumbar discal pseudocysts were included in the case series. Six dogs presented with acute onset and two dogs presented with subacute onset of thoracolumbar myelopathy. MRI showed compressive thoracolumbar myelopathy due to a round to oval-shaped epidural mass lesion communicating with the intervertebral disc, iso/hypointense on T1WI and mostly hyperintense on T2WI, associated with a variable contrast-enhancing wall, compatible with a cyst-like structure. These structures were surgically visualised and removed through a mini-hemilaminectomy or hemilaminectomy and submitted for histologic investigation. One dog also underwent cytologic examination of the cystic content. Similar to that in humans, histology revealed a cyst-like nature with a wall consisting of dense fibrous connective tissue containing clusters of chondroid cells accompanied by groups of notochordal cells and occasional erythrocytes; however, a real epithelial lining was missing and the term pseudocyst seemed more appropriate.

CLINICAL SIGNIFICANCE

This report describes clinical signs, and MRI and histologic findings of discal pseudocysts in dogs with thoracolumbar myelopathy. Despite being rare, discal pseudocysts should be considered as a differential diagnosis in dogs with acute onset thoracolumbar myelopathy.

Classification of Intervertebral Disc Disease

Intervertebral disc disease (IVDD) has been recognized in dogs since the 1800s, when the first descriptions of extruded disc material within the vertebral canal were published. In the intervening time our understanding of intervertebral disc pathology in dogs and cats has increased dramatically, with many variations of IVDD described. Whilst the volume of literature and collective understanding of IVDD has expanded, there has also been scope for confusion as the definition of intervertebral disc disease, with its myriad different manifestations, becomes more complicated. A large volume of literature has aimed to combine the use of histopathology, diagnostic imaging and clinical findings to better understand the various ways in which IVDD can be classified. Much of this research has focused on the classification of mechanisms of intervertebral disc degeneration, centering around the differences between, and overlaps in, IVDD in chondrodystrophic and non-chondrodystrophic dog breeds. However, with the increasing availability of advanced imaging modalities allowing more accurate antemortem diagnosis, the concept of IVDD has expanded to include other clinical presentations that may not fit into traditional models of classification of IVDD. This review aims to provide an up to date overview of both historical and current systems of IVDD classification, highlighting the important findings and controversies underpinning them.

Cystic Abnormalities of the Spinal Cord and Vertebral Column

Cystic lesions of the vertebral column and spinal cord are important differential diagnoses in dogs with signs of spinal cord disease. Synovial cysts are commonly associated with degenerative joint disease and usually affect the cervical and lumbosacral regions. Arachnoid diverticulum (previously known as cyst) is seen in the cervical region of large breed dogs and thoracolumbar region of small breed dogs. This article reviews the causes, diagnosis, and treatment of these and other, less common, cystic lesions.

Lumbosacral intraspinal extradural ganglion cyst in a cat

Case summary

A 16-year-old neutered female domestic shorthair cat was referred for chronic history of reluctance to jump, stiffness of the tail and lower back pain. Mild pelvic limb ataxia, reduced perianal reflex and lumbosacral discomfort were present on neurological examination. On magnetic resonance imaging, a well-defined rounded structure of 3 mm in diameter was identified on the right dorsal aspect of the epidural space at L7–S1, causing displacement of the cauda equina. The lesion was hyperintense to spinal cord parenchyma on T2-weighted images and hypointense on T1-weighted images, consistent with a fluid-filled structure. A Lumbosacral dorsal laminectomy was performed. A clear fluid-containing structure was identified between the right L7 nerve root and the cauda equina. Following surgical excision, histopathology confirmed the cystic nature of the lesion and revealed thick disorganised sheaths of fibrocollagenous tissue and flattened mesenchymal cells lining the luminal part of the cyst wall. A diagnosis of intraspinal ganglion cyst was made. The cat recovered uneventfully. Seven months after surgery euthanasia was performed for unrelated reasons; no neurological deficits were present.

Relevance and novel information

This is the first reported case of intraspinal ganglion cyst in a cat. Intraspinal extradural cysts should be considered among other differential diagnoses for cats with lumbosacral myelopathy/radiculopathy.

Hydrated nucleus pulposus extrusion in dogs: correlation of magnetic resonance imaging and microsurgical findings

Background

Magnetic resonance imaging (MRI) patterns of canine cervical hydrated nucleus pulposus extrusion (HNPE) have been described by a few reports, but the correlation between microsurgical and MRI features has never been investigated. The aim of this study was to compare the MRI features of HNPE with microsurgical findings and cytological outcomes and also to investigate the anatomical and pathophysiological aspects of the disease.

Methods

A prospective clinical study was conducted in 36 dogs suffering from HNPE. The diagnosis was based on high-field MRI findings of ventral extradural lesions, adjacent to the dorsal aspect of intervertebral discs, characterised by high signal intensity in T2-weighted sequences and hypointensity in T1-weighted sequences. MRI images were analysed with regard to the intervertebral space involved, the grading of spinal cord compression, the signal intensity and distribution of the material, and the thickness and signal intensity of the involved discs. All patients underwent microsurgical decompression and direct observations were recorded and films of the surgical procedure analysed.

Results

The majority of patients had acute onset of clinical signs (78 %), the patient did not exhibit signs of pain in 75 % of dogs and neurological deficits varied from slight tetraparesis (33 %) to tetraplegia (28 %). The localization of the extruded disc material was ventral relative to the dorsal longitudinal ligament that was lifted dorsally and appeared intact at the site of compression. Direct microsurgical observations of the HNPE sites showed that extruded disc material was collected within the fibres of the dorsal longitudinal ligament. The consistency was gelatinous in 42 %, water-like in 33 %, and lumpy liquid in 25 % of cases. Cytological samples did not detect the presence of inflammation, bacteria, fungi, neoplastic cells or foreign material.

Conclusions

Microsurgical features of HNPE suggest that the extruded disc is collected within the fibres of the dorsal longitudinal ligament and this may explain the typical MRI appearance of this disease. Further pathophysiological studies are needed to investigate why the cervical nucleus pulposus extrusion appears to occur without obvious trauma.

Electronic supplementary material

The online version of this article (doi:10.1186/s13028-015-0151-x) contains supplementary material, which is available to authorized users.

Discal cysts of the cervical spine in two dogs

Discal cysts, which lie directly over intervertebral discs, are rare. Two old dogs with tetraparesis were referred to our facility. In both animals, magnetic resonance imaging revealed intraspinal extradural cystic mass lesions that were dorsal to degenerative intervertebral discs at the C3-C4 level. These lesions had low signal intensity on T1-weighted images, and high signal intensity on T2-weighted images. A ventral slot approach was used to perform surgical decompression, after which the symptoms improved remarkably. Discal cysts should be included in the differential diagnosis of dogs with cervical pain and tetraparesis. One effective treatment for discal cysts is surgical intervention.

Ventral occipito-atlanto-axial fluid-filled lesion causing dynamic spinal cord compression in a cat

Cystic lesions affecting the vertebral canal or spinal cord have rarely been reported in cats. A 3-year-old female neutered domestic longhair cat presented for evaluation of a 2-year-history of episodes of ataxia and paresis affecting all limbs. Neurological examination was consistent with a lesion in the C1-C5 spinal cord segments. Magnetic resonance imaging (MRI) showed a fluid-filled lesion at the occipito-atlanto-axial region causing dynamic spinal cord compression on flexion of the neck. The imaging characteristics were compatible with a juxta-articular cyst. To our knowledge, this is the first report of a fluid-filled lesion causing dynamic cervical spinal cord compression in a cat and highlights the importance of performing flexion-extension MRI views in diagnosing cases with dynamic spinal cord compression.

Extramedullary spinal cysts in dogs

OBJECTIVE

To (1) synthesize the terminology used to classify extramedullary spinal cysts in dogs to clarify some of the commonly reported misconceptions, and (2) propose a classification scheme to limit confusion with terminology.

STUDY DESIGN

Literature review.

METHODS

An online bibliographic search was performed in January 2013 for articles relating to extramedullary spinal cysts in dogs using PubMed (http://www.pubmed.gov/) and Google Scholar (http://scholar.google.com/) databases. Only peer-reviewed clinical literature describing cystic lesions pertaining to the spinal cord and associated structures was included.

RESULTS

From 1962 to 2013, 42 articles were identified; 25 (95 dogs) reported meningeal cysts, 10 (24 dogs) described 60 extradural cysts, 3 reports (18 dogs) described discal cysts or acute compressive hydrated nucleus pulposus extrusions (HNPE). Spinal cysts were categorized by location based on cross-sectional imaging as meningeal or extradural non-meningeal. Sub-classification was then performed based on surgical findings and pathology. Meningeal cysts included arachnoid diverticulae and Tarlov (perineural) cysts. Extradural non-meningeal cysts included intraspinal cysts of the vertebral joints, ligaments and discs. Discal cysts also fit this category and have been reported extensively in humans but appear rare in dogs.

CONCLUSIONS

Extramedullary spinal cysts should be first classified according to location with a sub-classification according to pathologic and surgical findings. Previous canine cases of discal cysts appear to represent a different disease entity and the term acute compressive HNPE is therefore preferred.

Spinal cord compression in two related Ursus arctos horribilis

Two 15-yr-old grizzly bear littermates were evaluated within 9 mo of each other with the symptom of acute onset of progressive paraparesis and proprioceptive ataxia. The most significant clinical examination finding was pelvic limb paresis in both bears. Magnetic resonance examinations of both bears showed cranial thoracic spinal cord compression. The first bear had left-sided extradural, dorsolateral spinal cord compression at T3-T4. Vertebral canal stenosis was also observed at T2-T3. Images of the second bear showed lateral spinal cord compression from T2-T3 to T4-T5. Intervertebral disk disease and associated spinal cord compression was also observed at T2-T3 and T3-T4. One grizzly bear continued to deteriorate despite reduced exercise, steroid, and antibiotic therapy. The bear was euthanized, and a necropsy was performed. The postmortem showed a spinal ganglion cyst that caused spinal cord compression at the level of T3-T4. Wallerian-like degeneration was observed from C3-T6. The second bear was prescribed treatment that consisted of a combination of reduced exercise and steroid therapy. He continued to deteriorate with these medical therapies and was euthanized 4 mo after diagnosis. A necropsy showed hypertrophy and protrusion of the dorsal longitudinal ligament at T2-T3 and T3-T4, with resulting spinal cord compression in this region. Wallerian-like degeneration was observed from C2-L1. This is one of few case reports that describes paresis in bears. It is the only case report, to the authors' knowledge, that describes spinal magnetic resonance imaging findings in a grizzly bear and also the only report that describes a cranial thoracic myelopathy in two related grizzly bears with neurologic signs.

Intraaxial Spinal Cord Hemorrhage Secondary to Atlantoaxial Subluxation in a Dog

A 1-year-old, 3.5-kg, spayed female, toy poodle was presented for acute-onset tetraplegia and neck pain. Neuroanatomical diagnosis was consistent with a first through fifth cervical (C1 through C5) spinal cord lesion. Radiographs of the cervical vertebral column revealed atlantoaxial (AA) subluxation. Magnetic resonance imaging revealed abnormalities consistent with intraaxial spinal cord hemorrhage at the level of the AA articulation. The dog was treated with external coaptation. After 8 days, the dog regained voluntary motor function in all four limbs. Surgical stabilization was pursued. Postoperatively, the dog regained the ability to ambulate. This report details the imaging findings and management of a dog with intraaxial spinal cord hemorrhage secondary to AA subluxation.