How a combination of photobiomodulation and rehabilitation therapy may positively impact symptom progression and survival times in dogs with a presumptive diagnosis of degenerative myelopathy.
Degenerative myelopathy (DM) is a disease that affects the spinal cord of older dogs, leading to hind limb weakness and paralysis. Most of us are used to seeing DM patients decline from the initial stages of generalized proprioceptive ataxia to non-ambulation within six to nine months, a clinical course consistent with what is reported in the literature.1 This is a grim reality that anyone dealing with DM patients has to come to terms with, as we watch alert, willing, and often otherwise healthy dogs succumb to motor degeneration, incontinence, loss of quality of life, and ultimately, euthanasia. In this paper, we’ll focus on a retrospective study suggesting that a combination of photobiomodulation and intensive rehabilitation therapy may slow the progress of DM and increase longevity.
How the study got started
“I think I’m seeing a difference in these patients,” said my colleague, Debbie (Gross) Torraca, DPT, MSPT, Diplomat ABPTS, CCRP, referring to her canine patients with DM. As the owner of a referral rehabilitation facility for animals in Connecticut, Debbie has treated many DM cases. She has a large number of very compliant clients whose pets were referred to her for the purposes of palliating their symptoms and attempting to slow disease progression as much as possible using intensive rehabilitation therapy.2 As we continued our discussion, it became clear that the results Debbie was seeing in a subset of her patients over the past few years were not typical.
Debbie posited that a change in the photobiomodulation (PBM), or laser therapy, protocol she was using was the only difference for the patients in which she was seeing slowed symptom progression and increased survival times. Otherwise, she had utilized the same rehabilitation therapy regimen and home exercise recommendations for pet owners that she had used for years. The results she was seeing were remarkable, but I was admittedly still skeptical. This was, after all, DM we were talking about. But as Debbie shared her data and we started examining it in detail, it became clear that the results were different for this subset of patients treated with a different PBM protocol.
Data analysis
As this was a retrospective analysis, we were able to gather information on patient demographics, disease progression, and survival in the presumed DM patients treated at the facility over a nine-year period, and then analyze it to determine if there were any differences in outcomes between the two PBM treated groups, as well as compared to historical data expectations.
Twenty dogs ultimately met all the inclusion criteria set forth, and these were sorted into two different groups, labeled PTCL-A and PTCL-B, for analysis based on the PBM protocol used in their treatment. At the time, only three other studies existed in the published literature containing information on the progression of clinical symptoms and/or survival data for larger groups of dogs with DM.2-4 Even though the baseline characteristics of patients from those studies may have been different, along with the treatment interventions applied, we believed they provided a set of historical “expectations” for disease progression and survival information, which was important for comparison purposes.
Data analysis revealed statistically significant differences in the mean times between symptom onset or start of treatment, and both non-ambulation and euthanasia, in one treatment group compared to both the other treatment group and the historical published expectations.
- The mean time between onset of clinical signs and non-ambulation was significantly longer in the PTCL-B group (31.76 ± 12.53 months) than in the PTCL-A group (8.79 ± 1.60 months) (p < 0.05).
- The mean time between onset of clinical signs and time of euthanasia was significantly longer in the PTCL-B group (38.2 ± 14.67 months) than in the PTCL-A group (11.09 ± 2.68 months) (p < 0.05).
The data analysis suggested that the combination of PBM consistent with PTCL-B parameters (980 nm wavelength, delivered on contact to the skin surface of the thoracic and lumbar spine at 6 to 12 W power [1.2 to 2.4 w/cm2] with a corresponding energy density of 14 to 21 J/cm2 over the entire treatment area) and intensive rehabilitation therapy delays the progression of clinical signs and extends the survival time of dogs with DM.
Light energy delivered to the spinal cord
In examining possible reasons for response differences between the groups, the most obvious is that the light parameters in one group (PTCL-B), but not the other (PTCL-A), were sufficient to not only reach the tissues of interest in the spinal cord, but to be absorbed there and exert effects. When transcutaneously delivering light to the deep tissues, the light energy is attenuated in the hair coat as well as in the intervening tissues of the skin and muscle. Previous published work 5-6 has reported quantitatively the amount of light transmitted to the level of the spinal cord in cadaver dogs under safe, clinically acceptable, skin-applied irradiance, and showed that there is a linear correlation between the irradiance of the light at the skin and that of the light measured at the spinal canal.
A large body of evidence in the published literature demonstrates that PBM can effectively modulate the inflammatory response after both peripheral nerve injury and in spinal cord injury (SCI). Many studies provide evidence that light confers specific beneficial effects on the response of cells in the CNS to injury, leading to alteration of the secondary injury response and progression of the injury process.7
Going forward
We acknowledge the retrospective nature of this study, its small sample size, and the dearth of historical data from studies with similar parameters that could be used for comparison. While all these factors suggest caution in drawing conclusions from the results presented, the retrospectively collected data showed that the combination of PTCL-B PBM and intensive rehabilitation therapy had a significant beneficial impact on the clinical symptom progression and survival times of dogs with a presumptive diagnosis of DM. As there are no other effective treatments, we suggest here that this combination should be considered for dogs with a presumptive diagnosis of this disease. Further research on this therapy in a more controlled setting is warranted for dogs, and potentially for humans with ALS. It is our sincere hope that this information will help our colleagues “see a difference” in their patients as well, and give hope for a disease that has long frustrated veterinarians, rehabilitation therapists, and pet owners alike.
The complete published Open Access study, including more detailed information on the PBM and rehabilitation protocols may be viewed here: https://www.liebertpub.com/doi/full/10.1089/photob.2019.4723.
Drs. Lisa Miller and Debbie Torraca have also recorded a webinar presenting the findings from this study and discussing further detailed recommendations for managing patients with DM in practice. This webinar is available on-demand at: https://www.companionanimalhealth.com/webinar/new-degenerative-myelopathy-research-a-review-from-th/true.
Author disclosure statement: Dr. Miller is currently employed by LiteCure and was involved in the collection of data from hospital records, data analysis, and article preparation; however, she was not employed by LiteCure at the time the patients in this study were treated. She declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest.
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6Piao D, Sypniewski LA, Dugat D, Bailey C, Burba D, De Taboada L. “Transcutaneous transmission of photobiomodulation light to the spinal canal of dog as measured from cadaver dogs using a multi-channel intra-spinal probe”. Lasers Med Sci 2019;34:1645–1654.
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