29 Nov 2022
Alex Gough MA, VetMB, CertSAM, CertVC, PGCert(Neuroimaging), MRCVS, runs the rule of the latest studies in veterinary medicine in his latest Research Review.
Alex Gough
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Image: © Lunja / Adobe Stock
Necrotising meningoencephalitis (NME) is a nasty inflammatory disease of the CNS that is rapidly progressive, hard to treat and often fatal.
Because of its rapid progression, by the time a diagnosis is made, severe neurological problems are often already present. Pug dogs are genetically predisposed to the disease.
Windsor et al1 performed a prospective observational cohort study with genome‑wide genotyping to assess whether pugs at genetic risk of NME show neurological abnormalities prior to developing severe clinical signs typical of NME.
A total of 36 pugs younger than four years of age and free of signs of NME were included in the study.
Neurological examinations were performed four weeks apart, along with MRI, CSF analysis and infection disease testing in all dogs that had abnormalities detected on both neurological examinations.
The frequency of the risk allele was 40%, with 14% at high risk, 53% at medium risk and 33% at low risk.
A third of the genetically at‑risk pugs had reproducible neurological abnormalities, compared to none of the low‑risk dogs. Neurological abnormalities detected included multifocal spinal pain (found in all the dogs with abnormalities), reduced menace response in five of the eight dogs, and lateralising postural reaction deficits, also in five of the dogs.
The authors noted the finding of this early clinical phenotype in apparently asymptomatic, genetically at‑risk pugs may help with the planning of diagnostic and therapeutic clinical trials.
A similar disease to NME is meningoencephalitis of unknown origin (MUO), an inflammatory CNS disease, although the prognosis is not quite as poor as for NME.
Previous studies have been inconsistent with regards to identifying risk factors for early death, and prognosis and optimal treatment selection is still difficult to ascertain in MUO cases.
Lawn and Harcourt-Brown2 performed a study to assess the effect of possible prognostic factors on survival in 98 dogs with MUO.
The effect of clinical and MRI findings, and the type of treatment given on survival time at 7, 30 and 100 days after diagnosis was examined.
Obtundation at presentation was found to increase the odds of death by 6.6 times in the first 7 days, 2.1 times at days 8 to 30 and 1.9 times at days 31 to 100. However, no other clinical, MRI or treatment factor was found to be associated with survival.
In particular, addition of an IV infusion of cytarabine to immune-suppressive treatment with corticosteroids did not improve survival.
Lymphoma is a common haematological neoplasia in dogs, affecting a variety of breeds and ages. Miniature dachshunds are thought to be predisposed.
Rimpo et al3 performed a retrospective study to compare lymphoma in miniature dachshunds with the disease in other breeds. A total of 108 miniature dachshunds and 149 dogs of other breeds, all of which had lymphoma, were included in the study.
Gastrointestinal lymphomas were found to be the most common type in miniature dachshunds, with 53 of 108 dogs affected compared to 41 of 149 of other breeds.
Multicentric lymphoma was more common in other breeds, accounting for 74 of 149 cases in this cohort compared to 33 of 108 miniature dachshunds.
Although the median age of dogs developing lymphoma was the same in both cohorts, it was found that lymphomas were more frequently observed in dachshunds younger than four years of age compared to young dogs of other breeds.
Most lymphomas were B-cell type. An age of younger than four and a B-cell type were favourable prognostic factors for miniature dachshunds with large cell gastrointestinal lymphoma.
The authors recommended clinicians are aware of the specific presentation of lymphoma in miniature dachshunds, which may help guide treatment decisions.
Lymphoma is also common in golden retrievers – it is the second most common neoplasm of this breed. It is thought to arise due to both genetic and environmental factors.
Leuthcke et al4 performed a nested case‑control study to investigate the association between environmental pollution and lymphoma in golden retrievers.
A total of 49 golden retrievers with non‑cutaneous lymphoma and 98 golden retrievers without a history of cancer – matched by age, sex and neuter status – were included in the study.
The geographic proximity of the dog’s home address to nine different sources of environmental pollution was assessed, together with information on local ozone and airborne fine particulate matter levels.
Chemical plants, rubbish dumps, manufacturing plants, railways, power plants and high-voltage power lines were among the possible sources of pollution considered.
A cumulative exposure burden (a household close to three or more pollution sources) was nearly significant with a p=0.053 for the multicentric lymphoma subgroup.
The authors recommended further research into whether environmental factors may be associated with lymphoma, but this study – although suggestive of certain patterns – was not strong evidence for the association of pollution with lymphoma.
Medical futility is the concept that a particular treatment in a particular case would not improve a patient’s condition and, therefore, should not be provided. This is controversial, since it is unclear at what statistical threshold a treatment should be considered futile, and because some clinicians may claim a treatment is futile without possessing all the relevant data to make this judgement.
In human medicine, disagreement often occurs between medical professionals and patients, or their surrogates, regarding futility.
Peterson et al5 performed a cross‑sectional online anonymous questionnaire‑based study. A total of 477 vets in small animal general and specialty practice were included – 99% of respondents believed that futile care occurs in veterinary practice, with 42% believing it occurs commonly.
A total of 99% reported witnessing futile care at least once within their careers and 85% reported they had seen it within the previous year, with most seeing it occur in both inpatient and outpatient settings.
In total, 69% disagreed with a statement that futile care is always wrong and 71% thought situations existed when provision of futile care was appropriate.
The authors noted it is important to find a definition of medical futility in veterinary medicine, given how commonly it is encountered, and that ethical guidance regarding medical futility is needed.
Myxomatous mitral valve disease (MMVD) is common in small‑breed dogs and can lead to secondary cardiomegaly as the disease progresses.
Clark et al6 performed a study to assess whether cardiac MRI and other biomarkers can detect myocardial ischaemia and fibrosis in dogs with cardiomegaly secondary to MMVD.
Six dogs with stage B2 MMVD were included in the study. They were being treated with pimobendan with or without enalapril. Six healthy controls were also included.
Cardiac troponin I was measured and cardiac MRI – including T1‑weighted and T2‑weighted images, and post-gadolinium contrast images – were acquired.
Dogs with MMVD had significantly higher cardiac troponin I levels than control dogs. Four dogs with MMVD and three control dogs had myocardial fibrosis. None of the dogs were found to have myocardial diffusion deficits. No differences were found in measurements of the MRI images, nor in an estimate of the extracellular volume.
The authors noted that at least some dogs with cardiomegaly secondary to MMVD do not appear to have clinically relevant myocardial fibrosis.
Laryngeal paralysis is a neurodegenerative disease seen commonly in older medium and large‑breed dogs.
Surgical treatment – for example, with laryngeal tieback – is usually recommended for treatment of symptomatic cases; however, risks and possible long‑term complications exist with surgery, and not all owners elect for this treatment.
Théron and Lahuerta‑Smith7 performed a preliminary study to assess the use of laryngeal silicone stents in this condition. Six dogs diagnosed with bilateral laryngeal paralysis, for which classic surgical treatment by arytenoid lateralisation had been declined, were treated with the laryngeal stents.
All dogs showed immediate clinical improvement – and in four dogs, no clinical signs or radiographic abnormalities were found at a follow‑up visit one week later.
One dog was thought to be aspirating water while drinking, but repositioning of the stent resolved this problem. Another dog had a recurrence of signs due to stent migration. Since a larger stent was not available, this dog underwent arytenoid lateralisation.
In the four dogs without initial complications, no further complications have been noted at a follow‑up of 7 to 13 months and the owners report quality of life as satisfactory.
The authors concluded that laryngeal silicone stenting is a viable alternative to arytenoid lateralisation surgery, both for short‑term relief and long‑term treatment.
