The term cervical spondylomyelopathy (CSM) defines a series of pathological alterations in the osteoarticular and ligamentous structures of the cervical portion of the spinal column that result in a static and/or dynamic compression of the spinal cord and of the corresponding nerve roots and which typically affect medium and large sized dogs. CSM produces neurological symptoms of variable severity, more or less associated with cervical pain, often characterized by a particular type of gait, defined as "wobbly”. This is the origin of one of the most well-known terms under which this pathology is referred to: Wobbler Syndrome.
In the literature, cervical spondylomyelopathy has been called with an extensive variety of terms mediated (often inadequately) from human medicine, terms that basically describe the pathological entities at the base of the disorder. Cervical spondylolisthesis, Cervical spondylosis, Caudal cervical subluxation, Cervical vertebral instability, Caudal cervical spondylopathy, Caudal cervical malformation-malarticulation and Caudal cervical spondylomyelopathy are just some of the terms that have been used to describe this syndrome in veterinary literature.
Today, the aetiopathogenesis, diagnosis and treatment of CSM are still the subject of controversy, since the origin of this disease has not yet been clarified, in spite of the numerous studies.
Cervical spondylomyelopathy was described for the first time in 1967 in Basset Hounds. The disease has been reported with particular relevance in Great Danes at first and then in Dobermann Pinschers. The two most typical clinical forms with characterize this disease are present in these two breeds: in Great Danes, the symptoms appear early and are largely due to compressions of the spinal cord by altered bone structures, while in Dobermann Pinschers the symptoms, which appear later, result for the most part from osteoligamentous and intervertebral disc alterations that mainly affect the caudal segments of the cervical spine.
AETIOLOGY
Although CSM is a long known problem, its aetiology is still unknown today.
As gathered from the varied nomenclature with which this syndrome has been described, numerous causes are at the basis of the symptoms of CSM, including (Figs. 1, 2 and 3):
- vertebral malformations,
- malformations or arthritis of the articular facets,
- disc protrusions and, more rarely, extrusions,
- diseases of the articular facets,
- hypertrophy of the long dorsal ligament and of the ligamentum flavum.
The common result of the interaction of one or more of the above factors is always a compressive lesion of the cervical spinal cord. The compression can be static, i.e. not affected by the position of the neck, or dynamic, when particular positions of the neck (hyperflexion or hyperextension) may cause temporary spinal cord compression.
The aetiological theories proposed to explain the disease, described briefly below, include genetic, congenital, nutritional and conformational hypotheses.
Genetic hypothesis – A genetic cause, in reality never confirmed, has been proposed by several researchers, given that some breeds, like Dobermann Pinschers and Great Danes, appear to be particularly prone to this disease.Two studies carried out on more than 370 Dobermanns, although rather dated, were not able to confirm this theory.
Congenital hypothesis – A congenital origin of the disease has been proposed, based on the results resulting from a CT study performed on Dobermann puppies which showed the presence of spinal canal stenosis at the last cervical vertebrae, stenosis which was not detectable in the control group made up of puppies of other breeds of the same age.
Conformational and biomechanical hypothesis – This hypothesis considers the dynamic and mechanical forces that are generated along the cervical section of the spinein breeds with a long and thin neck, heavy head and fast growth. According to this theory, the forces generated at this level are such as to be able to cause morphological variations of the anatomical structures involved, causing spinal cord compression. This hypothesis has not been confirmed to date.
Nutritional hypothesis – This hypothesis, by now quite dated, has never been confirmed by scientific evidence.This theory implicated abnormal and too rapid growth aided by an excessive dietary intake of calcium and energy. Today, in spite of a better understanding of the dietary requirements of growing dogs of giant breeds and the consequent use of balanced diets, the incidence rate of Wobbler Syndrome has not decreased in the least.
PATHOPHYSIOLOGY
Before covering the possible pathogenetic mechanisms at the basis of CSM symptoms, it is appropriate to underline that significant percentages of clinically normal dogs show signs of spinal cord compression or changes in vertebral column structures that are compatible with the disease. In Dobermann Pinschers, given the same changes, it appears that it is the diameter of the vertebral canal that makes the difference between subjects with obvious clinical signs and asymptomatic dogs. The latter have a larger cervical spinal canal diameter compared to the symptomatic population.
For didactic purposes, the pathophysiology of compressive lesions can be divided schematically into compressive lesions resulting from changes in disc (and/or ligament) structures and compressive lesions resulting from bone alterations. As mentioned beforehand, the former are typical of CSM in Dobermanns, while the latter are usually responsible for the earlier forms characteristic of giant breeds and appear to implicate a congenital element. In any case, this distinction should not be emphasised excessively, considering that in clinical practice the disease can be a result of the coexistence of both types of changes, more or less prevalent and variously represented for each individual case.
Changes in disc structures, usually intervertebral disc protrusions, are sometimes associated with hypertrophy of the long dorsal ligamentand produce ventral or ventrolateral extradural compressions of the spinal cord (Fig. 4).
Ligamentum flavum hypertrophy may complicate the picture by causing a dorsal compression that contributes to further medullary cavity stenosis (see Fig. 8). The majority of these lesions are located at C5-C6 and C6-C7. These lesions appear to be the product of the particular biomechanical stresses affecting the caudal cervical spine, in particular of the twisting forces which act on intervertebral discs. Around 50% of Dobermanns with CSM have a single lesion while, for the other half, multiple compressions can be documented during diagnosis, which must be kept duly in mind when setting up the therapeutic plan.
Compressive lesions linked to bone changes are mainly due to abnormal proliferations of the vertebral arch and pedicles, as well as to osteoarthritic malformations and deformations of the articular facets, which result in absolute stenosis of the spinal canal. The compression on the spinal cord may be worsened by the presence of synovial cysts, resulting from facet joint osteoarthritis, which have also been documented. In the presence of caudal cervical spondylomyelopathy there can also be a remodelling of the vertebral bodies, with the protrusion of the dorsal part of the cranial epiphysis of the vertebral body into the medullary cavity (the so-called “tipping”), causing additional spinal canal stenosis (Fig. 5, see Fig. 6).
From the above we infer that the pathophysiological picture of a dog with CSM is much more complex than that of a simple compression due to an intervertebral disc disease: in particular, CSM implicates the concepts of static lesions and dynamic lesions. By dynamic compressive lesion we mean a lesion that improves or gets worse based on the different positions assumed by the neck (See Fig. 9).
In view of the obvious therapeutic implications, it is important to underline that the concept of dynamic lesion is not comparable to that of instability; by the latter we mean the loss of capability of the cervical spine, when subjected to physiological stresses, to maintain stable relationships between the vertebral structures in order to prevent injury to the spinal cord and/or to the nerve roots, cervical pain or the development of deformities. Today, there is no scientific evidence confirming that cervical instability plays an important role in the pathophysiogenesis of cervical spondylomyelopathy.
SIGNALMENT
Although CSM is considered a disease of large and giant breed dogs, it can occur in several breeds, including small ones, and at any age. Prevalence studies have not been carried out on the disease, it is however common opinion that CSM is the most common cervical disease present in medium sized and giant dog breeds. Among these, the Dobermann Pinscher is the breed most represented.
With respect to age, the average age of onset of the symptoms in giant breed dogs like Great Danes, Mastiffs, Rottweilers and Swiss Mountain Dogs is of around 3.8 years, with subjects often symptomatic already from the initial months of life. The majority of large breed dogs with CSM (Dobermann, Weimaraner and Dalmatian) become symptomatic later on, usually after 3 years of age, with a mean age for Dobermanns of 6.8 years and 7.9 years for the other breeds. In large sized breeds males and females are equally affected by the disease, while in giant breeds males seem to be more commonly affected.
CLINICAL PRESENTATION
The symptoms detected are those typical of a disease of the first section of the spinal cord and can differ slightly depending on whether the cervical section (segments C1-C5) or the cervicothoracic section (segments C6-T2) of the spinal cord are involved.
Clinical history – The onset of the symptoms may vary depending on the underlying cause and on the different pathophysiogenetic modes of development of the disease.Indeed, there can be sporadic acute presentations, but more commonly the picture is that of a chronic progressive disease, with clinical signs that can last weeks or months before the clinical examination. In many cases it becomes impossible to establish a starting date for the symptoms, and the owners’ lack of awareness seems to be due to the fact that the initial phases of the disease go unnoticed in virtue of the fact that, in giant dogs that grow rapidly, reduced coordination is considered normal for the growing animal, while in elderly dogs lack of coordination is attributed to arthritis , laziness or simply old age. Acute presentations are usually (re)aggravations of chronic subclinical or clinical forms recognised by the owners, and can be triggered by a slight trauma or an abnormal movement. The clinical signs vary considerably and go from modest cervical soreness to severe non-ambulatory tetraparesis; the most frequent presentation, however, is that of a slowly progressive incoordination, especially obvious in the hind legs.
Neurological examination – The most important and most frequent clinical signs detected during the clinical examinationare those of an alteredgait, characterised by an obvious lack of coordination, which can be more or less associated with tetraparesis.
At neurological examination dogs with CSM present normal mentation and behaviour; postural examination may detect a broad based stance of the hind limbs; the front limbs may present abduction of the elbows and internal rotation of the digits. The neck may be held lower compared to the normal position. Dogs with more severe symptoms tend to favour the sternal decubitus position or, in more extreme cases, be forced to the lateral decubitus position.
Gait analysis is the part of the neurological examination that best allows to highlight the most noticeable aspects of cervical spondylomyelopathy. A proprioceptive ataxia is typically present, much more pronounced in the hind limbs than in the front limbs.(Video 1). It is not uncommon for subjects with injuries to the most caudal segments of the cervical spinal cord to show gait alterations almost exclusively confined to the hind limbs, mimicking, in the eyes of the less expert evaluator, a thoracolumbar problem (Video 2). A marked abduction of the hind limbs is present, the stride is excessively long and the gait is plainly dysmetric. The gait is characterised by the typical swaying of the rump that has given this disease the name “Wobbler Syndrome”. In milder cases, a modest ataxia of the hind limbs is often associated with ambling. With the passing of time, the changes become more pronounced and a spastic paraparesis of the hind limbs can also become manifest; as a result of the marked abduction caused by the stiffness of the hind legs the toenails can scrape on the ground until they are excessively worn down (Video 3).
The front limbs present less pronounced changes, which are usually categorized into two different types. The first is typical of Dobermanns and, more generally, of subjects with injuries of the most caudal segments; it is characterized by relatively modest changes, with a short, under the body, hypometric stride, sometimes associated with lameness (understood as a sign of compression of a nerve root) (Videos 4 and 5; see Video 3). The impression is that of a dog whose front and rear limbs advance at different speeds, a condition also defined with the term “two-engine gait”. The second type is instead more typical of medium-high cervical lesions and is characterized by a very pronounced limb rising phase, in which the dog almost "launches" the leg in front of itself (see Video 1). When possible, it is always useful to evaluate gait on stairs which, in the presence of ataxia, exacerbate coordination defects, especially during descent (Video 4). The changes described above can have varying degrees of severity and be accompanied, in the most severe cases, by a pronounced tetraparesis.
In the presence of a pronounced ataxia it is not always possible to document proprioceptive deficits, especially of conscious proprioception. Deficits in postural and proprioceptive responses, when present, are much more marked in the rear limbs (Video 7). The proprioceptive positioning test performed on the rear legs can show an exaggerated rather than depressed response, characterized by marked abduction and an exaggerated rising response when the limb is repositioned (Video 8). The evaluation of the postural and proprioceptive reactions of the front limbs is in many instances not very significant (see Video 7).
Examination of the cranial nerves does not allow to detect abnormalities worthy of note. Spinal reflexes in the hind legs can be normal or increased, while in the front legs several possibilities are possible. A decrease in the reflexes in the front limbs is evidence of an injury to the cervicothoracic intumescence, typical of caudal cervical compressions. Absence of the cutaneous trunci muscle reflex, along the entire back of the animal, can occur for the same reason. Conversely, in the case of cranial cervical injuries at C6, a normal to increased extensor tone may be present, due to injuries to the upper motor neuron system.
Cervical stiffness and pain, the latter never particularly pronounced, can be induced by palpation and manipulation of the neck. More than soreness, affected subjects show reluctance and resistance to passive manipulation of the neck (Video 9). Energetic manipulations of the neck are not necessary for the evaluation of cervical pain; if performed incorrectly they can in fact cause a significant worsening of the clinical picture. During the clinical examination it is therefore just as useful to thoroughly evaluate the posture and range of motion of the neck shown by the animal during voluntary movements, from side to side, ventrally and dorsally, with the aid of a morsel of food.
In the course of CSM atrophy of the supraspinatus muscle is often observed, reflecting the involvement of the suprascapular nerve, whose motor neurons reside in the sixth cervical segment of the spinal cord.
Cervical spondylomyelopathy and hypothyroidism. In addition to cervical spondylomyelopathy, Dobermann Pinschers have a particular breed predisposition for hypothyroidism. The possible presence of this disease must be duly taken into account, in view of the possible implications that this may have on the therapeutic approach. Apart from the previously described symptoms, subjects affected by both CSM and hypothyroidism may show skin alterations (dandruff, hair coat thinning, which may appear lacklustre and dull, seborrhoea, blackheads), recurrent outer ear infections, changes in body profile, lethargy and a particular intolerance to cold temperatures (Video 10). It should not be forgotten that hypothyroidism can be responsible for a neuromuscular syndrome characterized by tetraparesis, exercise intolerance, voice loss and, above all, a generalized decrease in spinal reflexes.
DIFFERENTIAL CLINICAL DIAGNOSES AND DIAGNOSTIC PROTOCOL
In large dogs, cervical spondylomyelopathy must be included in the list of differential diagnoses together with all those chronic/subacute diseases that can produce neurological and painful alterations attributable to cervical spine involvement. Many disorders can produce at least some of the signs described, however the diseases that are mainly to be included in the list of differential diagnoses with CSM are spinal column or spinal cord tumours, intervertebral disc degeneration, discospondylitis and meningomyelitis. It is also important to exclude the presence of peripheral nervous system diseases that typically induce weakness in the four legs but not ataxia.
The diagnostic suspicion of CSM is confirmed by diagnostic imaging studies. Conventional radiology is capable of showing the bone components of the cervical spinal column, thus giving indications on the relationships existing between the vertebrae, however it is not capable of providing information on the spinal cord, nor on the ligamentous components. Myelography is therefore necessary or, better still, an advanced diagnostic imaging technique such as Magnetic Resonance Imaging (MRI) or Computerised Tomography (CT).
Radiology – To confirm a suspicion of CSM, [20] conventional radiology still plays an important role as it is an excellent screening tool both as regards the exclusion of other cervical bone diseases such as bone tumours, vertebral fractures, osteomyelitis and discospondylitis, and to have confirmation of the possible presence of bone changes ascribable to CSM. In giant breed dogs the radiographic findings detectable in the presence of CSM are represented above all by osteoarthritic changes in the articular facets; caudal cervical spondylomyelopathies are instead characterized by changes in the shape of the vertebral body, which in more severe cases tends to acquire a triangular appearance, with a reduction of intervertebral spaces and spinal canal stenosis (Fig. 6). It should be underlined, however, that these radiographic changes can also be found in clinically normal dogs and thus do not constitute an element of certain confirmation of the presence of CSM.
Myelography – Myelography, in whicha contrast medium is used to opacify the subarachnoidspace, outlines the spinal cordand allows to identify the site or sites responsible for the compression. The lines of contrast medium are diverted dorsally, ventrally or laterally, depending on the anatomical structure exerting compression in the different projections (latero-lateral and ventro-dorsal) (Fig. 7). Myelography can document single or multiple, dorsal, lateral or ventral compressions. Dorsal compressions are usually caused by hypertrophy of the ligamentum flavum (Fig. 8), ventral compressions by intervertebral disc protrusions while lateral compressions are the result of deformation of the articular facets.
In order to study the static and dynamic components of the compression “stressed” myelographic projections are also possible, exerting traction on the cervical column, or bending and extending the neck in latero-lateral projections (Fig. 9). Myelography is therefore capable of documenting “static” compressions, i.e. present even with the neck in neutral position, or “dynamic” compressions, i.e. evident only when the neck is kept in a bent or extended position.
In view of its greater invasiveness and the risks connected with the execution of a myelographic study, such as the deterioration of clinical conditions or the onset of seizures, myelography has progressively been abandoned as a diagnostic tool in cases of suspected CSM. The technique has been abandoned in favour of advanced diagnostic imaging studies such as Magnetic Resonance Imaging (MRI) or Computerised Tomography (CT).
Computerised Tomography (CT) – Although based on the same principles of radiology, Computerised Tomography provides a much greater detail of the different compression sites, as well as of bone structures and of their relationships.However in reality, even with CT, for an optimal visualisation of injuries the use of an iodised contrast medium injected into the subarachnoid space is necessary (Myelo-CT) (Fig. 10). As a result, a Myelo-CT presents the same problems already mentioned for myelography. It is basically for these reasons that, when able to choose, Magnetic Resonance Imaging is preferred, as it is non-invasive, has fewer risks for the patient and is able to provide more information on the nervous system parenchyma and on the adjacent ligamentous structures.
Magnetic Resonance Imaging (MRI) - Magnetic Resonance Imagingis currently considered the “gold standard” in the diagnosis of CSMin both human and veterinary medicine. This advanced diagnostic imaging technique allows to detect changes in the spinal cord itself, as well as to provide indications on the different compression sites. MRI images, especially in T2-weighted scans, take advantage of a natural “myelography effect”, thus allowing the documentation of compression sites. Typically, in T2-weighted sequences degenerated vertebral discs appear hypointense (Fig. 11). Spinal cord signal variations, meaning hyperintensity in T2-weighted images, are considered evidence of chronic suffering of the parenchyma, with the development of gliosis following chronic compression (Fig. 11). Hyperintensity in T2-weighted images, combined with hypointensity in T1-weighted images, underlines severe suffering of the spinal cord and is associated with a tendentiously poor prognosis in terms of a possible functional recovery.
Given the compressive nature of CSM, with Magnetic Resonance Imaging, which allows to acquire images in all spatial dimensions, it is possible to document dorsal, ventral and lateral compressions. Similarly to what has been reported for myelography, dorsal compression is linked to hypertrophy of the ligamentum flavum, lateral compression to hypertrophy of the articular capsules of the articular processes and bone proliferations, while ventral compression is linked to disc protrusions, change in the relationships between vertebrae or to hypertrophy of the longitudinal dorsal ligament. When reading the MRI scan it is important to evaluate the diameter of the intervertebral foramina, since the cause of cervical pain in a subject with CSM could reside precisely in stenosis of one or more intervertebral foramina.
In some cases the degree of spinal cord compression evident at the MRI examination is minimal compared to the importance of the clinical signs: in these subjects it is assumed that the dynamic component may play a greater clinical role than the static component. For all those cases in which a “dynamic” injury can be hypothesised, the MRI examination should be carried out with sequences with the cervical spinal column first in the neutral position and then under traction, in order to evaluate any differences (Fig. 12). This information is extremely important when choosing the therapeutic protocol.
Additional diagnostic tests – Considering that breeds suffering from CSMare also proneto other diseases that can have important implications in the management and treatment of these patients, additional tests, aimed at excluding or confirming the presence of such diseases, are also to be considered.
Hypothyroidism: hypothyroidism is frequently present, especially in Dobermanns, to the point that some authors have hypothesised a possible correlation between hypothyroidism and CSM. Establishing whether an animal suffers or not from hypothyroidism is extremely important as it has a major impact on the therapeutic protocol, be it conservative or surgical.
Von Willebrand Disease: in Dobermanns the prevalence of this disease has been estimated at around 73%; given that surgery is often the option chosen to treat CSM, it is absolutely advisable to assess the bleeding time of the buccal (oral) mucosa or the titration of the von Willebrand factor.
Cardiological evaluation: an evaluation of cardiac function through clinical examination, electrocardiogram and echocardiography is recommended when preparing a candidate for surgery, especially in the case of Dobermanns, given the high prevalence of cardiomyopathies in this breed.
THERAPEUTIC PROTOCOL
From the therapeutic point of view, there are several treatment options for CSM and the choice of one or the other depends heavily on the clinical presentation of each individual patient, as well as on the age, on the general conditions (understood as the presence or not of concomitant pathologies) and on the owner’s economic situation. The first disctinction is to be made between medical treatment, of the conservative type, or surgical treatment, which considers several techniques depending on the different presentations of the CSM. The choice between the two types of intervention will be dictated by the patient’s clinical conditions, as well by the factors listed above: medical treatment can be considered in subjects with slight ataxia and tetraparesis, whereas the surgical solution becomes the most advisable option in subjects with more severe symptoms.
Conservative treatment - Medical therapyenvisages limiting the subject’s movement, i.e. the so-called “cage rest” for at least 4 weeks, and the use of a harness to prevent tractionson the neck during outings. During this period the dog should be taken outdoors by its owner only to fulfil its physiological needs, avoiding more demanding exercises. The use of anti-inflammatory drugs, nonsteroidal but especially steroidal, is reported in the literature even though there is no scientific evidence of their actual usefulness and there is the problem of the side effects that can develop with prolonged administrations. Prednisolone has mainly been used in the conservative management of CSM, at an anti-inflammatory dose (1mg/kg/day), decreased progressively over two/three weeks.
When conservative treatment is successful, the dog can return to a normal activity level in around 4-6 weeks. However, also in the following weeks the return to normal physical activity should be gradual. Hypothyroid animals with concomitant CSM benefit considerably from supplementation with levothyroxine.
Surgical treatment – The decision to perform surgery should be based on several aspects, including the severity of the symptoms, the presence of chronic pain, the lack of response to medical treatment and the concomitant presence of extraneurological diseases (e.g.dilated cardiomyopathy). Numerous surgical techniques have been proposed over the years by different authors: we shall limit ourselves here to briefly describing the main ones.
The surgical techniques can be divided into direct decompression techniques, which include dorsal laminectomy, ventral slot procedure and hemilaminectomy, as well as indirectdecompression techniques, typically grouped into the so-called distraction-stabilisation techniques (which use pins or screws and cement [PMMA: polymethyl methacrylate], metal plates and spacers), normally associated with discectomy or with a total or partial ventral slot pocedure.
From a schematic point of view the different techniques may be classified also on the basis of the type of approach used for the removal of the compression: ventral, dorsal or lateral. The use of one or the other will be dictated by the origin of the spinal cord compression.
Ventral approach – The ventral approach is used to resolve medullary compressions resulting from disc protrusions; this approcach envisages the use of direct or distraction-stabilisationdecompressiontechniques. The direct decompression technique which is most often used is the ventral slot procedure (Fig. 13).
The technique involves the opening of a window along the midline (no more extensive than a third of the length and of the width of the vertebral body) that includes part of the vertebral body of two adjacent vertebrae, in order to create an access, and the removal of the disc protrusion and/or the hypertrophy of the long dorsal ligament. A relatively frequent complication is the possible damage to the internal vertebral venous plexus, which produces profuse haemorrhages. The technique has a 72% long-term success rate. Distraction or stabilisation of the intervertebral space requires the use of screws and polymethyl methacrylate can be associated or not with the ventral slot procedure.
Dorsal approach – In this approach the decompression technique consists in creating an opening of the vault of the medullary cavity (dorsal laminectomy). This operation is indicated for dorsal compressions resulting from osteoarthritic alterations of the articular facets or from hypertrophy of the ligamentum flavum. Dorsal laminectomy can also be used to resolve multiple ventral compressions, more or less associated with ligamentum flavum hypertrophy (Fig. 14).
Lateral approach – A hemilaminectomyfollowing a dorso-lateral approach has recently been proposed, however this approach involves greater technical difficulties compared to the techniques illustrated above. This technique can be used whenever diagnostic imaging has documented a very lateralised compression of the spinal cord or of the nerve roots, a compression difficult to resolve with the traditional dorsal or ventral approaches (Fig. 15).
COMPLICATIONS AND PROGNOSIS
Intra- and perioperative complications are rare, but they can have devastating effects, including death of the patient. In the case of surgical stabilisation, it is important to recall that the forces that were previously absorbed by one joint are now distributed on the joint that precedes and on the one that follows; this could cause pathological changes over the long term, with recurrence of the symptoms, following the so-called “domino effect”. Owners must clearly be informed about this possibility, however the complications over time caused by the domino effect should not be overemphasised.
The prognosis for patients undergoing surgery is generally good, with an improvement reported in around 80% of subjects; it should be recalled, however, that many dogs require prolonged treatment and physiotherapy during the post-operative period before recovering completely. The prognosis is less favourable and the recovery time is longer in dogs which are nonambulatory or in which there is more than one compression site involved. Today surgery appears to offer a better percentage of resolution compared to conservative treatment; it should however be underlined that the median survival times reported in the literature for dogs that undergo surgery compared to those treated conservatively is identical.
Suggested readings
- Bagley R.: Small Animal Neurology: Acute spinal disease. Proceedings of the North American Veterinary Conference, Orlando Florida 2006.
- Da Costa R.C.: Cervical Spondylomyelopathy: recent advances. Proceedings of the World Small Animal Veterinary Association, Sao Paul, Brazil 2009.
- Da Costa R.C.: Cervical Spondylomyelopathy (Wobbler Syndrome) in Dogs.
- The Veterinary Clinics of North America: Small Animal Practice - 40 (2010) - 881–913
- De Decker S., Bhatti S.F.M., Duchateau L., Martlé V.A., Van Soens I., Vanmeervenne S.A.E., Saundersy J.H., Van Ham L.: Clinical evaluation of 51 dogs treated conservatively for disc-associated wobbler syndrome Journal of Small Animal Practice (2009) 50, 136–142.
- Trotter E.J.J., 1985: Textbook of small animal Orthopaedics. C. D. Newton and D. M. Nunamaker (Eds.) Publisher: International Veterinary Information Service (www.ivis.org), Ithaca, New York, USA.
- Sharp N.J.H., Wheeler S.J., 2005: Cervical spondylomyelopathy. In: Small Animal Spinal Disorders. Diagnosis and Surgery. 2nd ed. ElsevierMosby, St Louis, MO, USA. pp 211-246.
- VanGundy T.E.: Disc-associated wobbler syndrome in the Doberman pinscher. The Veterinary Clinics of North America: Small Animal Practice 18, (1988), 667-696.