Diagnosis and management of dogs with degenerative myelopathy: A survey of neurologists and rehabilitation professionals

Abstract

Background

Antemortem diagnosis of degenerative myelopathy (DM) in dogs is presumptive and there are no accepted guidelines for the management of this condition.

Hypothesis/Objectives

Describe current practices of neurology clinicians and physical rehabilitation professionals in the diagnosis and management of DM.

Animals

None.

Methods

Online surveys examining diagnosis and management of DM were constructed and distributed via neurology and rehabilitation listservs.

Results

One hundred ninety neurology and 79 rehabilitation professionals from 20 countries participated. Most neurology (142/189) and rehabilitation (23/39) respondents required genetic testing for the superoxide dismutase 1 (SOD1) mutation and 82/189 neurologists also required spinal magnetic resonance imaging (MRI) for presumptive DM diagnosis. Most neurology respondents recommended exercise (187/190) and physical rehabilitation (184/190). Over 50% (102/190) of neurology respondents perform rechecks on dogs diagnosed with DM. Rehabilitation respondents reported preservation or improvement of strength (78/79) and coordination (77/79) as therapeutic goals. At‐home exercises (75/79), underwater treadmill (64/79), gait training (55/79), and strength building exercises (65/79) were used to maintain strength (58/79), coordination (56/79), muscle mass (56/79), and improve overall wellbeing (54/79). Neurology respondents reported that owners elect euthanasia when dogs become nonambulatory paraparetic whereas rehabilitation respondents report euthanasia when paraplegia and incontinence develop.

Conclusion and Clinical Importance

The majority of dogs diagnosed with DM have not undergone advanced imaging, the combination of history, neurological findings, and genetic testing is heavily relied upon. Whereas the diagnosis of DM is frequently made by veterinary neurologists, continued care is often performed by rehabilitation professionals or primary veterinarians.

Abbreviations

ACVIM

American College of Veterinary Internal Medicine

ACVSMR

American College of Veterinary Sports Medicine and Rehabilitation

CCRP

certified canine rehabilitation practitioners

CCRT

certified canine rehabilitation therapists

DM

degenerative myelopathy

ECVN

European College of Veterinary Neurology

MRI

magnetic resonance imaging

SOD1

superoxide dismutase 1

1. INTRODUCTION

Degenerative myelopathy (DM) in dogs is a neurodegenerative disorder first described in 1973, with a breed predisposition for German Shepherds. ¹ DM is observed in many dog breeds including Boxers, Rhodesian Ridgebacks, Chesapeake Bay retrievers, and Pembroke Welsh Corgis. ² This progressive, fatal disease initially presents with asymmetric general proprioceptive ataxia and paraparesis. Signs progress to paraplegia and ultimately flaccid tetraplegia. ² Death results from respiratory dysfunction, although most dogs are euthanized before reaching that point. Homozygosity for a glutamate‐to‐lysine missense mutation in the superoxide dismutase 1 gene (SOD1) is identified as a strong risk factor for development of clinical signs of DM. There is an age‐related incomplete penetrance, with clinical signs developing variably in dogs that are homozygous for the variant. ³ Thus, genetic testing for the SOD1 mutation should be used to help support a diagnosis of DM. Ante‐mortem diagnosis remains a diagnosis of exclusion, requiring differentiation from other myelopathies such as intervertebral disc extrusion and spinal neoplasia. Nonetheless, aging dogs commonly have concurrent intervertebral disc protrusions and other diseases. The clinical contribution of each condition is difficult to gauge but CSF concentrations of phosphorylated neurofilament heavy chain are higher in dogs with DM. ⁴ As such, antemortem diagnosis is considered presumptive. Definitive diagnosis is based on histopathology of the spinal cord. ⁵ Histopathologic lesions include axonal and myelin degeneration at all levels of the spinal cord, with the most severe lesions in the dorsal portion of the lateral funiculus in the middle to caudal thoracic spinal cord. ¹ No medical therapies are shown to alter the progression of DM. Based on initial anecdotal evidence of efficacy, investigators have examined treatment with ε‐aminocaproic acid, N‐acetylcysteine, and supplementation of Vitamins C and E but found no evidence of benefit in slowing disease progression. ⁶ Daily physical rehabilitation exercises, including hydrotherapy, have been reported to increase the median survival time and delay the course of disease in a small retrospective study that included 9 dogs with intensive vs 6 dogs with moderate rehabilitation. ⁷ There are currently no guidelines regarding diagnosis and management of DM in dogs. The 2 groups of clinicians most involved with the management of this condition are board‐certified veterinary neurologists and rehabilitation professionals (a combination of board‐certified veterinarians, veterinary or veterinary technician certificate holders, and professionals with a special interest in rehabilitation, or training in human physiotherapy). Thus, the objective of this study was to describe current practices of neurology clinicians and rehabilitation professionals in the diagnosis and management of DM.

2. METHODS

2.1. Survey development

Separate surveys were developed for neurology clinicians and rehabilitation professionals using an online survey platform (Alchemer Survey Software, formerly SurveyGizmo, Louisville, CO). A trial survey was tested and approved by the investigators before distribution. The main goals of both surveys were to determine how these groups of clinicians make a diagnosis of DM and manage these dogs after the diagnosis. Because the roles of neurology clinicians and rehabilitation professionals differ in the management of dogs with DM, each group completed a different survey.

2.2. Surveys

For each survey, the first section consisted of demographic information and experience in diagnosing DM (Data S1). The second section included closed‐ended questions with choice options concerning data on the diagnostic approach of DM. The third section included open‐ended and closed‐ended questions with choice options and write‐in options about treatment of DM. This section was expanded in the survey for rehabilitation professionals. The last section pertained to client‐based questions on methods of educating owners about DM, euthanasia decisions, and clinical trial considerations.

2.3. Survey distribution

Survey links were distributed by email to the ACVIM/ECVN neurology listserv and VetRehab rehabilitation listserv. Neurology clinicians and rehabilitation professionals were invited to complete them within 2 weeks. A single reminder was sent after the first week of opening the survey.

2.4. Data analysis

This was a descriptive study in which responses to questions were summarized and expressed as fractions and percentages.

3. RESULTS

3.1. Neurologist survey

The survey was distributed to 930 recipients in the ACVIM/ECVN listserv. One hundred ninety responses (20.4%) from 17 different countries were collected between August 17, 2021, and August 31, 2021. A majority of the responses were from clinicians in the United States of America (119/190; 62.6%), the United Kingdom (26/190; 13.7%), and Germany (8/190; 4.2%). Responses from other countries included Italy (6/190; 3.2%), France (5/190; 2.6%), Canada (5/190; 2.6%), Australia (4/190; 2.1%), Spain (3/190; 1.6%), Switzerland (3/190; 1.6%), Netherlands (3/190; 1.6%), Portugal (2/190; 1.1%), and 1 each from Japan, Finland, Belgium, Singapore, Hong Kong, and Slovenia. Of the 190 respondents, there were 168 neurologists, 17 neurology residents, and 5 clinicians with practice limited to neurology. Most (183/190; 96.3%) respondents were clinically active with 7 respondents reporting that they had retired from clinical neurology practice.

One hundred eighty‐nine (99.5%) respondents reported routinely using additional diagnostic tests beyond physical exam and history when presumptively diagnosing DM. Most (n = 142; 75.1%) report always testing for the SOD1 mutation (Table 1). Eighty‐two (43.4%) and 41 (21.7%) respondents reported always obtaining a spinal MRI and CSF analysis, respectively. The frequency of use of SOD1 testing and spinal MRI when making a diagnosis of DM was similar between North America and the rest of the world (Table 2). Electrodiagnostic testing was rarely performed, with 148 respondents (78.3%) reporting that they do not perform electrodiagnostics when trying to establish a presumptive diagnosis of DM. Thirteen respondents (6.9%) reported that they always use “other” diagnostic tests, including complete blood count and serum biochemistry (n = 9), infectious disease testing (n = 8), orthopedic examination, radiography of vertebral column, pelvic limbs and hips (n = 6), and histopathology of the spinal cord post‐mortem (n = 5).

TABLE 1.

Frequency of diagnostic tests utilized by neurology clinicians (n = 189) when making a presumptive diagnosis of DM

Diagnostics used	Always	Sometimes	Never
SOD1	142 (75.1%)	43 (22.8%)	4 (2.1%)
Spinal MRI	82 (43.4%)	101 (53.4%)	6 (3.2%)
CSF analysis	41 (21.7%)	128 (67.7%)	20 (10.6%)
Electrodiagnostics	0 (0%)	41 (21.7%)	148 (78.3%)
Other	13 (6.9%)	29 (15.3%)	147 (77.8%)

Note: The majority of clinicians always use SOD1 testing with spinal MRI and CSF analysis less commonly used. Electrodiagnostics and other tests are rarely used.

TABLE 2.

Comparison of the frequency of utilization of the SOD1 genetic test and spinal MRI between North America (NA) and the rest of the world (ROW) when making a presumptive diagnosis of DM

Frequency of use	SOD1	Spinal MRI
Always	NA: 94/123 (76.4%)	NA: 47/123 (38.2%)
	ROW: 48/66 (73%)	ROW: 35/66 (53%)
Sometimes	NA: 27/123 (22%)	NA: 75/123 (61%)
	ROW: 16/66 (24%)	ROW: 26/66 (39%)
Never	NA: 2/123 (1.6%)	NA: 1/123 (0.8%)
	ROW: 2/66 (3%)	ROW: 5/66 (7%)

Note: The frequency of use of both SOD1 testing and spinal MRI were similar between North America and the rest of the world.

In presumptively diagnosed cases of DM, 102 respondents (53.7%) reported that they performed recheck examinations after diagnosis whereas 58 respondents (30.5%) recommended that the primary care veterinarians perform recheck examinations. Thirty respondents (15.8%) reported not performing nor recommending recheck examinations. Variation between recommended timing of recheck examinations ranged from every 4 weeks to yearly. The majority (77/102; 75.5%) of neurology clinicians who performed recheck examinations themselves recommended times ranging from 2 to 6 months.

Almost all respondents routinely recommend regular exercise (187/190; 98.4%) and physical rehabilitation (184/190; 96.8%). A majority of respondents (147/190; 77.4%) recommend assistive walking devices (such as booties/socks, harnesses, wheelchairs), whereas only 17.4% (33/190) routinely recommend vitamins/supplements and 11.1% (21/190) routinely recommend diet changes (Figure 1).

FIGURE 1.

Routinely recommended therapeutic interventions by neurology respondents (n = 190). Almost all respondents recommended physical rehabilitation and regular exercise with most recommending assistive walking devices. The majority of respondents did not recommend diet changes nor vitamins/supplements

For client support, 105 (55.3%) respondents routinely provide resources about DM to owners utilizing client handouts (85/105; 81%), websites (25/105; 23.8%), primary literature (16/105; 15.2%), and information on support groups (8/105; 7.6%). Additionally, 168 respondents (88.4%) report that they or their staff provide lessons and resources for owners regarding bladder management.

One hundred fourteen (60%) neurology respondents report that owners most often euthanize when their dog becomes nonambulatory paraparetic. This was followed by development of incontinence ± paraplegia (62/190; 32.6%), ambulatory paraparesis (5/190; 2.6%), paraplegia (5/190; 2.6%), tetraplegia without respiratory compromise (2/190; 1.1%), and tetraplegia with respiratory compromise (2/190; 1.1%). Lastly, when asked how often the option of necropsy is discussed with owners for a confirmative diagnosis, respondents reported that they always (27/190; 14.2%), often (24/190; 12.6%), sometimes (55/190; 28.9%), or rarely (54/190; 28.4%) discuss necropsy, whereas 30/190 respondents (15.8%) reported that they never discuss the option of necropsy with owners.

3.2. Rehabilitation survey

Seventy‐nine responses were collected between September 13, 2021, and September 30, 2021, and included rehabilitation specialists from 8 different countries. The term specialist is used to encompass both veterinarians and nonveterinarian rehabilitation therapists. A majority of the responses were from rehabilitation specialists in the United States of America (66/79; 84%), Canada (6/79; 8%), and the United Kingdom (2/79; 3%). There was 1 response each from Greece, the Netherlands, Australia, Russian Federation, and South Africa. Of the 79 respondents, 34 (43%) were both veterinarians and certified canine rehabilitation therapists (CCRT), 18 (23%) were CCRT but not veterinarians, 6 (8%) were rehabilitation veterinary technicians and assistants, 5 (6%) were American College of Veterinary Sports Medicine and Rehabilitation (ACVSMR) board‐certified rehabilitation therapists, 4 (5%) were veterinarians without additional qualifications in rehabilitation and 12 (15%) were “other.” The “other” respondents included certified canine rehabilitation practitioners (CCRP), ACVSMR residents, certified canine pain practitioners, and a human physical therapist. Most (73/79; 92%) respondents were currently seeing dogs with neurological problems with only 6 respondents (8%) reporting that they previously worked with dogs with neurological problems.

Forty‐two respondents (53%) reported treating between 1 and 5 dogs with DM annually with 5 respondents (6%) treating more than 20 cases annually. Thirty‐nine (49%) of the rehabilitation respondents, all veterinarians, reported that they have diagnosed dogs with DM. Twenty‐three of these 39 respondents (59%) reported always testing for the SOD1 mutation. Four (10%) respondents reported always obtaining a spinal MRI and 2 (5%) reported always performing CSF analysis to diagnose dogs with DM. Most reported not utilizing electrodiagnostic testing (32/39; 82%) nor other diagnostic tests (29/39; 74%) to make a presumptive diagnosis.

Almost all of the respondents agreed that preservation/improvement of strength (78/79; 99%) and coordination (77/79; 98%) were the goals of their therapeutic protocols. Twenty‐four (30%) and 34 respondents (43%) reported treatment of spasticity and pain as their goals, respectively. Of the 26 respondents who answered “other” regarding goals of treatment, 9/26 (35%) involved some aspect of client education and support of owners in helping with management and quality of life for their dogs. Various answers included helping to treat pain from compensation in other areas, delaying progression of the disease, maintaining activities of daily life, and helping provide support with assistive walking devices (such as booties/socks, harnesses, and wheelchairs). Respondents most commonly recommended at‐home exercises (75/79; 95%), followed by strength building exercises (65/79; 82%), underwater treadmill (64/79; 81%), and gait training exercises (55/79; 70%; Figure 2). Only 9/79 (11%) respondents reported routinely recommending overland treadmill use as part of their rehabilitation protocol. Additionally, most (69/79; 87%) respondents utilize adjunctive modalities such as laser (67/69; 97%), acupuncture (49/69; 71%), and pulsed electromagnetic fields (39/69; 57%). All respondents recommend regular exercise at home. The most common form of exercise recommended for owners was regular walking, often with suggestions of hill walking (46/79; 58%). Other at‐home exercise regimens included simple exercises like sit‐to‐stand and perturbation of balance, with many respondents noting that they tailored the regimens to the dog. Ninety‐four percent (74/79) recommend assistive walking devices whereas only 52% (41/79) and 35% (28/79) routinely recommend vitamins/supplements and diet changes respectively as at‐home management strategies.

FIGURE 2.

Routinely recommended treatments by rehabilitation respondents (n = 79). The majority of respondents recommended at‐home exercises, strength building exercises, underwater treadmill and gait training exercises. Few recommended the use of overland treadmill

All but 1 respondent routinely recommends that dogs with DM be treated with in‐clinic rehabilitation and the majority recommend once weekly (34/79; 43%) or twice weekly (25/79; 32%) sessions. Only 4/79 (5%) routinely recommend that dogs return for in‐clinic rehabilitation once every 2 weeks and 1/79 (1%) recommend once per month. Of the 13 (17%) respondents who chose “other” regarding frequency of in‐clinic rehabilitation, 7/13 (54%) reported that it depends on the individual dog and owner needs/requirements. Most respondents believed their treatment helps the dogs maintain strength (58/79; 73%), coordination (56/79; 71%), and muscle mass (56/79; 71%) with 68% (54/79) perceiving an improvement in overall wellbeing. Most (72/79; 91%) also believed that their treatment helps delay disease progression.

When asked about the stage at which most owners elect euthanasia, 38/79 (48%) respondents reported that it occurs when the dogs develop incontinence ± paraplegia. This was followed by nonambulatory paraparesis and by tetraplegia without respiratory compromise (14/79; 18% each), paraplegia (7/79; 9%), tetraplegia with respiratory compromise (3/79; 4%), and ambulatory paraparesis (2/79; 3%). Most respondents reported never (30/79; 38%) or rarely (27/79; 34%) discussing the option of necropsy with owners for a more confirmative diagnosis. The remaining 22 respondents reported that they sometimes (15/22; 68%), often (3/22; 14%), or always (3/22; 14%) discuss the option of necropsy.

4. DISCUSSION

The goal of this study was to describe current practices of neurology clinicians and rehabilitation professionals in the diagnosis and management of DM. Our study found that most neurology clinicians use testing for the SOD1 mutation to establish a presumptive diagnosis of DM, while substantially fewer additionally require either MRI or CSF analysis to establish the diagnosis. In addition, nearly 50% of rehabilitation professionals (all of whom were veterinarians) reported that they presumptively diagnose the condition, typically with SOD1 testing alone. Neurology clinicians do not routinely use any specific medical therapies but recommend routine exercise and refer dogs to rehabilitation clinicians for ongoing care. Rehabilitation professionals then provide ongoing management of DM. Rehabilitation professionals use a combination of exercises and reported that their treatment delays progression. The stage at which owners elect euthanasia differs between neurologists and rehabilitation professionals, with the former reporting nonambulatory paraparesis whereas the latter report incontinence ± paraplegia as the most common endpoints. Our study highlights the current approach to diagnosis and management of DM, assisting with the development of future clinical guidelines.

The SOD1 test was the most commonly utilized diagnostic test by both neurology and rehabilitation clinicians when diagnosing dogs with DM. Approximately 45% of neurology and 10% of rehabilitation clinicians reported always obtaining spinal MRI. This is important to note because the SOD1 testing only identifies dogs at risk of developing DM because of incomplete penetrance of the mutation. ⁴ Consequently, the test is inadequate as a sole diagnostic test. The reliance on SOD1 testing alone for presumptive diagnosis likely reflects a combination of owner reluctance to pursue MRI because of anesthesia risks and costs, as well as clinician preference. Regardless, reports of outcomes in dogs that have not undergone spinal MRI in addition to genetic testing should be interpreted with caution because of the risk of misdiagnosis.

Because of the chronic, progressive disease course, the question of follow‐up and ongoing care provided to dogs that have been diagnosed with DM is important. Based on responses by the neurology clinicians, this care is often passed on to a rehabilitation professional. Because neurology clinicians frequently do not reevaluate their DM dogs, most are unable to accurately document neurological progression beyond major thresholds (such as inability to walk without support); therefore, concurrent conditions and secondary complications also are not well documented. Recommendations for recheck examination timing varied from every 4 weeks to yearly. In the absence of being able to offer an effective treatment, dogs affected with DM and their owners fall into a care void. It would be interesting to poll the owners of dogs diagnosed with DM about their perception of the follow‐up care and the impact of caring for a dog with DM on the carer's quality of life.

The majority of the rehabilitation professionals were in agreement on most commonly used treatments, suggesting there is a core, standard protocol that could include at‐home exercises, strength building exercises, and underwater treadmill use. The majority of respondents also reported anecdotally that their exercise regimens were effective. One study reported that 9 dogs treated with intensive daily physical rehabilitation (gait exercise 3‐5 times daily and either passive range of motion and massage 3‐5 times daily or daily hydrotherapy) survived longer and remained ambulatory longer than 6 dogs with moderate or no rehabilitation. ⁷ This small study provides the basis for the common recommendation to provide exercise and rehabilitation treatment. However, the observational (retrospective) nature of the study results in unavoidable biases that could affect the outcome. Nevertheless, these initial findings warrant further investigation into the efficacy of physical rehabilitation in dogs affected with DM. ⁸

Median survival time of dogs with DM is from 10 to 36 months. ² , ⁹ Given the progressive, fatal nature of DM, humane euthanasia is most often pursued before the end‐stage of disease. The current study found that neurology clinicians report euthanasia is most often pursued when dogs become nonambulatory paraparetic whereas rehabilitation specialists report incontinence (±paraplegia) as the stage at which owners decide to euthanize. Owners who pursue physical rehabilitation programs might also be more motivated to manage dogs with DM longer than those who do not. However, the support that a rehabilitation facility provides to an owner who is managing a dog with a progressive neurodegenerative condition likely plays a role in their threshold for euthanasia.

5. CONCLUSION

This study identified the most common diagnostic tools and management strategies used by neurology and rehabilitation clinicians for dogs with DM. Most clinicians use SOD1 testing for a presumptive diagnosis whereas fewer perform spinal MRI, particularly among the rehabilitation clinicians who report diagnosing DM. While many neurology clinicians reevaluate dogs diagnosed with DM, continued care is often referred to rehabilitation professionals or primary care veterinarians. Treatment recommendations most often include regular exercise and rehabilitation. Many rehabilitation professionals report stabilization of progression and improved well‐being of dogs with DM undergoing physical rehabilitation.

CONFLICT OF INTEREST DECLARATION

Authors declare no conflict of interest.

OFF‐LABEL ANTIMICROBIAL DECLARATION

Authors declare no off‐label use of antimicrobials.

INSTITUTIONAL ANIMAL CARE AND USE COMMITTEE (IACUC) OR OTHER APPROVAL DECLARATION

Authors declare no IACUC or other approval was needed.

HUMAN ETHICS APPROVAL DECLARATION

Authors declare human ethics approval was not needed for this study.

Supporting information

Data S1: Supporting Information.

Bouché TV, Coates JR, Moore SA, Faissler D, Rishniw M, Olby NJ. Diagnosis and management of dogs with degenerative myelopathy: A survey of neurologists and rehabilitation professionals. J Vet Intern Med. 2023;37(5):1815‐1820. doi: 10.1111/jvim.16829