Coonhound paralysis. Further clinical studies and electron microscopic observations

Early Neurophysiological Abnormalities in Suspected Acute Canine Polyradiculoneuropathy

Acute canine polyradiculoneuritis (ACP) is a common peripheral neuropathy in dogs, and is generally self-limiting and benign. Electrodiagnostic (EDX) tests are typically performed after 7-10 days. Delaying the definitive diagnosis may hamper the treatment of other causes of acute weakness, which may require specific treatments and may carry different prognoses. This retrospective multicenter study aims to assess whether EDX performed within the first 6 days of clinical signs onset can detect alterations indicative of ACP, and aims to characterize the most prevalent alterations. A total of 71 dogs with suspected ACP were retrospectively analyzed and classified into two groups based on EDX timing: early group (EG, 1-6 days after symptom onset) and late group (LG, 7-15 days after symptom onset). In our study, no significant differences were found between the two groups in motor nerve conduction studies (MNCSs) and F-wave analysis, indicating that EDX is able to demonstrate abnormalities even in the first 6 days from onset. Although the LG showed significantly greater degrees of electromyographic (EMG) alterations compared to the EG, frequent muscle alterations were still observed in the EG group. These findings support the use of EDX in patients with suspected ACP within the first 6 days from the clinical onset. Prompt neurophysiological examinations for suspected ACP patients can be performed effectively and can help allow for early diagnosis and facilitate appropriate treatment.

Polirradiculoneuropatia periférica desmielinizante associada ao uso de carbamazepina em cão: relato de caso

RESUMO Diversos fármacos são utilizados no tratamento da epilepsia e, assim como outros medicamentos, podem induzir a ocorrência de efeitos adversos, alguns tão graves que geram a necessidade de descontinuidade e substituição da terapia. A carbamazepina pode levar a alterações nos sistemas cardiovascular, respiratório e neurológico, sendo descritos na literatura casos de indução de miastenia gravis como distúrbio neuromuscular. Este estudo relata o caso de um cão que desenvolveu polirradiculoneuropatia desmielinizante, tendo como provável desencadeante a terapia com carbamazepina. O paciente apresentou tetraplegia, ausência de reflexos espinhais nos quatro membros, fraqueza cervical, diminuição do reflexo palpebral bilateral e esforço respiratório. A eletroneuromiografia demonstrou sinais de desmielinização. Este, portanto, é o primeiro relato de associação entre carbamazepina e polirradiculoneuropatia desmielinizante em cão.

An exploratory study into factors influencing development of acute canine polyradiculoneuritis in the UK

OBJECTIVES

To investigate whether the development of acute canine polyradiculoneuritis is associated with various putative risk factors.

MATERIALS AND METHODS

Retrospective case-control study with conditional logistic regression analysis from a referral hospital population in the UK where controls were matched for year of presentation.

RESULTS

Forty-three cases were identified with acute canine polyradiculoneuritis and 86 controls were selected. Jack Russell terriers and West Highland white terriers were found to have a significantly greater odds of developing acute canine polyradiculoneuritis compared to a mixed baseline group of dogs. The odds of developing acute canine polyradiculoneuritis were greater in the autumn and winter compared to spring. Vaccination, rural/urban habitation, sex, neuter status and age were not associated with development of acute canine polyradiculoneuritis in our population of dogs.

CLINICAL SIGNIFICANCE

Breed and season were associated with development of acute canine polyradiculoneuritis. However, this is a small sample and so this observation needs confirmation in further studies and other factors may also be involved. Nevertheless, these findings may be important in further understanding the aetiopathogenesis of this condition.

Nodo-paranodopathy, internodopathy and cleftopathy: Target-based reclassification of Guillain-Barré-like immune-mediated polyradiculoneuropathies in dogs and cats

Recent views on Guillain-Barré syndrome (GBS) question the accuracy of classification into axonal and demyelinating subtypes that represent convergent neurophysiological phenotypes rather than immunological targets. Instead it has been proposed to clarify the primarily affected fibre subunit in nerve biopsies. As nerve biopsies rarely are part of routine work-up in human patients we evaluated tissues taken from companion animals affected by GBS-like polyradiculoneuropathy to screen for distribution of immune cells, targeted fibre components and segregating non-inflammatory lesions. We identified that immune responses were directed either at Schmidt-Lanterman clefts, the paranode-node complex or both. Based on infiltrative and non-inflammatory changes, four subtypes and/or stages were distinguished, some of which indicate localisation of primary target antigens while others represent convergent late stage pictures, as a consequence to epitope spreading. The impact of histological subtyping onto clinical management and prognosis remains to be evaluated in future clinical trials. Natural development and clinical manifestation of large animal dysimmune neuropathy may reflect human Guillain-Barré syndrome more accurately than experimental models and therefore provide complementary clues for translational research.

Acute lower motor neuron tetraparesis

Flaccid nonambulatory tetraparesis or tetraplegia is an infrequent neurologic presentation; it is characteristic of neuromuscular disease (lower motor neuron [LMN] disease) rather than spinal cord disease. Paresis beginning in the pelvic limbs and progressing to the thoracic limbs resulting in flaccid tetraparesis or tetraplegia within 24 to 72 hours is a common presentation of peripheral nerve or neuromuscular junction disease. Complete body flaccidity develops with severe decrease or complete loss of spinal reflexes in pelvic and thoracic limbs. Animals with acute generalized LMN tetraparesis commonly show severe motor dysfunction in all limbs and severe generalized weakness in all muscles.

Animal models of autoimmune neuropathy

The peripheral nervous system (PNS) comprises the cranial nerves, the spinal nerves with their roots and rami, dorsal root ganglia neurons, the peripheral nerves, and peripheral components of the autonomic nervous system. Cell-mediated or antibody-mediated immune attack on the PNS results in distinct clinical syndromes, which are classified based on the tempo of illness, PNS component(s) involved, and the culprit antigen(s) identified. Insights into the pathogenesis of autoimmune neuropathy have been provided by ex vivo immunologic studies, biopsy materials, electrophysiologic studies, and experimental models. This review article summarizes earlier seminal observations and highlights the recent progress in our understanding of immunopathogenesis of autoimmune neuropathies based on data from animal models.

Anti-GM2 ganglioside antibodies are a biomarker for acute canine polyradiculoneuritis

Acute canine polyradiculoneuritis (ACP) is considered to be the canine equivalent of the human peripheral nerve disorder Guillain-Barré syndrome (GBS); an aetiological relationship, however, remains to be demonstrated. In GBS, anti-glycolipid antibodies (Abs) are considered as important disease mediators. To address the possibility of common Ab biomarkers, the sera of 25 ACP dogs, 19 non-neurological, and 15 epileptic control dogs were screened for IgG Abs to 10 glycolipids and their 1 : 1 heteromeric complexes using combinatorial glycoarrays. Anti-GM2 ganglioside Abs were detected in 14/25 ACP dogs, and anti-GA1 Abs in one further dog. All controls except for one were negative for anti-glycolipid Abs. In this cohort of cases and controls, the glycoarray screen reached a diagnostic sensitivity of 60% and a specificity of 97%; a lower sensitivity (32%) was reported using a conventional glycolipid ELISA. To address the possible pathogenic role for anti-GM2 Abs in ACP, we identified GM2 in canine sciatic nerve by both mass spectrometry and thin layer chromatography overlay. In immunohistological studies, GM2 was localized predominantly to the abaxonal Schwann cell membrane. The presence of anti-GM2 Abs in ACP suggests that it may share a similar pathophysiology with GBS, for which it could thus be considered a naturally occurring animal model.

Clinical course of acute canine polyradiculoneuritis following treatment with human IV immunoglobulin

Treatment of dogs with acute canine polyradiculoneuritis (ACP) is restricted to physical rehabilitation and supportive care. In humans with Guillain-Barré syndrome, the counterpart of ACP, randomized trials show that IV immunoglobulin (IVIg) speeds recovery. The authors of the current study hypothesized that dogs with ACP would tolerate IVIg well and recover faster than dogs managed with supportive treatment only. Sixteen client-owned dogs with ACP were treated with IVIg, and 14 client-owned dogs served as a retrospective control group. Diagnosis was confirmed using clinical features, electrodiagnostics, cerebrospinal fluid analysis, and muscle/nerve biopsies. The duration of the initial progressive phase, the time from IVIg administration until the dogs were ambulating without assistance, and the duration of the complete episode were evaluated. Adverse reactions (anaphylaxis, mild hematuria) were observed in two dogs. Dogs treated with IVIg were ambulating without assistance after a median of 27.5 days (range, 15-127 days) from onset of clinical signs. The control group was ambulatory without assistance at a median of 75.5 days (range, 5-220 days). Even though this result is not statistically significant, there is a clear trend toward faster recovery in dogs treated with IVIg.

Trigeminal and polyradiculoneuritis in a dog presenting with masticatory muscle atrophy and Horner's syndrome

A 9-year-old, spayed female, Airedale Terrier was euthanatized and necropsied after a progressive clinical course that included Horner's syndrome of the left eye and unilateral atrophy of the masticatory muscles. Although gross lesions were limited, a polyradiculoneuritis and ganglionitis that was most severe in the trigeminal nerves and ganglia were confirmed histologically. The inflammatory infiltrate consisted predominantly of macrophages and B and T lymphocytes that were phenotypically confirmed by immunostaining. Horner's syndrome was the result of damage to postganglionic sympathetic fibers that were incorporated in segments of the inflamed trigeminal nerve and its ophthalmic branch. Histologically, the character and distribution of the inflammation was similar to previously described syndromes of suspected immune-mediated etiology in humans and animals.

Electrophysiologic assessment of acute polyradiculoneuropathy in dogs: comparison with Guillain-Barré syndrome in people

Electrophysiologic investigations of motor and sensory nerve as well as ventral nerve root function were performed on 12 dogs with suspected acute canine polyradiculoneuropathy (ACP) at different stages and with different severity of disease. The most reliable electrophysiologic indicators of ACP were electromyographic changes (occurring in 100% of affected dogs), significantly decreased compound muscle action potential amplitudes (in 75, 90, and 100% of affected dogs at all sites along the sciatic/tibial, radial, and ulnar nerves, respectively), increased minimum F-wave latencies (67%), increased F ratios (92%), and decreased F-wave amplitudes (67%). These findings suggest that ACP represents a peripheral motor axonopathy, with demyelination and axonal involvement also occurring in ventral nerve roots. Evidence of peripheral demyelination was present in some dogs although it was overshadowed by the prominent axonopathy. ACP more closely resembles the acute axonal or intermediate forms of Guillain-Barré syndrome in people.

Sensory neuronopathy in dogs: a study of four cases

A neurological disease which selectively affects the primary sensory pathways was observed in 4 dogs. Clinical signs were dominated by ataxia due to impaired position sense. Deficient or abnormal pain sensation was also observed. Difficulty in eating probably arose from oral and lingual sensory deficit. The lesions were characterized by degeneration and loss of central and peripheral primary sensory axons, with a predilection for large myelinated fibres. The concept of a sensory neuronopathy was supported by the finding of neuronal degeneration and loss in dorsal root ganglia seen in 2 dogs. The cause of the disease is not known. The presence of mononuclear inflammatory cells in acute lesions suggests an infectious or autoimmune disease. Toxic and genetic factors are also to be considered.