Anatomic description and clinical relevance of the meningovertebral ligament in dogs.

OBJECTIVE: To determine whether dogs have a meningovertebral ligament (MVL) and to assess the effect that structure may have on pathological lesions within the ventral epidural space. SAMPLE: Cadaveric specimens from 6 neurologically normal dogs and 2 dogs with vertebral neoplasms that extended into the epidural space and MRI sequences and cytologic preparations from 2 dogs with compressive hydrated nucleus pulposus extrusion that underwent decompressive surgery. PROCEDURES: The vertebral column was removed for gross and histologic examination from the cadavers of neurologically normal dogs and dogs with vertebral neoplasms. For dogs with hydrated nucleus pulposus extrusion, MRI sequences to assess lesion location and topography and cytologic preparations of material surgically extirpated from the ventral epidural space were reviewed. RESULTS: All dogs had an MVL, which formed the ventral boundary of the epidural space and consisted of fibrous bands that attached the external ventral surface of the dura mater of the spinal cord to the dorsal surface of the vertebral bodies throughout the length of the vertebral canal. Both vertebral neoplasms had a bilobed appearance as did the extruded nucleus pulposus lesions on MRI sequences. CONCLUSIONS AND CLINICAL RELEVANCE: Results of the present study indicated that dogs have an MVL, which creates an anatomic barrier within the ventral epidural space and causes pathological lesions to adopt a bilobed shape regardless of the pathogenic process. Further anatomic studies of the MVL and vertebral canal of dogs are necessary to elucidate how those structures affect lesion progression within the ventral epidural space.

A Salivation Abnormality with Trigeminal Nerve Dysfunction in Dogs.

Trigeminal nerve pathology can lead to sensory and motor dysfunction to structures of the head that are easily recognized. The trigeminal nerve is a conduit for the distribution of postganglionic parasympathetic innervation to structures of the head. Parasympathetic innervation to the salivary glands is provided by preganglionic parasympathetic neurons of the facial and glossopharyngeal nerves. Postganglionic axons course with branches of the mandibular branch of the trigeminal nerve to reach the salivary glands. Denervation of the salivary glands impacts glandular function, leading to a reduction in the volume and composition of the saliva produced. Saliva plays an important role in oral health. Poor oral health has widespread systemic implications. This article describes a group of dogs with unilateral or bilateral dysfunction of the trigeminal nerve and/or its branches. In all dogs, an accumulation of thick, foamy saliva was observed accumulating in the dorsal aspect of the caudal oral cavity on the ipsilateral side to the affected nerve. In dogs with magnetic resonance imaging (MRI), there was a reduction in size based on the largest cross-sectional area measurement and an increase in mean signal intensity of the salivary glands ipsilateral to the affected nerves compared to the glands on the normal side. The authors hypothesize that the abnormal saliva and MRI changes observed were consequent to parasympathetic denervation of the salivary glands. The recognition of this clinical observation is the first step in understanding the impact that denervation has on salivation and ultimately on overall oral and systemic health in dogs.

Correlation of MRI with the Neuropathologic Changes in Two Cats with Bromethalin Intoxication.

Two cats were presented with multifocal neurological signs. One cat's signs progressed over 2 wk; the other cat progressed over 5 days. Examinations were consistent with a process involving the prosencephalon, vestibular system, and general proprioceptive/upper motor neuron systems. MRI of the brain and cervical spinal cord reveal widespread T2 hyperintensity of the white matter. Affected areas included the cerebrum, cerebral peduncles, corticospinal tracts of the pons and medulla, and the cerebellum. T2 hyperintensity was present in all funiculi of the spinal cord. Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps were consistent with cytotoxic or intramyelinic edema. Differential diagnosis included toxic or metabolic/degenerative leukoencephalopathies. Necropsies revealed widespread spongy degeneration of the central nervous system white matter. Toxicologic assays of liver specimens revealed desmethylbromethalin, a metabolite of bromethalin. Bromethalin is a rodenticide that causes uncoupling of oxidative phosphorylation. Antemortem diagnosis is challenging. DWI and ADC maps were instrumental in narrowing the differential diagnosis and raised the index of suspicion for bromethalin. Bromethalin intoxication should be considered in all animals with a progressive course of multifocal neurologic deficits. MRI, specifically, DWI and ADC maps, may serve as a biomarker of cytotoxic or intramyelinic edema associated with spongiform leukoencephalomyelopathy.

Adaptation of the Basso-Beattie-Bresnahan locomotor rating scale for use in a clinical model of spinal cord injury in dogs.

BACKGROUND: Naturally occurring acute spinal cord injury (SCI) in pet dogs provides an important clinical animal model through which to confirm and extend findings from rodent studies; however, validated quantitative outcome measures for dogs are limited. NEW METHOD: We adapted the Basso Beattie Bresnahan (BBB) scale for use in a clinical dog model of acute thoracolumbar SCI. Based on observation of normal dogs, modifications were made to account for species differences in locomotion. Assessments of paw and tail position, and trunk stability were modified to produce a 19 point scale suitable for use in dogs, termed the canine BBB scale (cBBB). Pet dogs with naturally occurring acute SCI were assigned cBBB scores at 3, 10 and 30days after laminectomy. RESULTS: Scores assigned via the cBBB were stable across testing sessions in normal dogs but increased significantly between days 3 and 30 in SCI-affected dogs (p=0.0003). The scale was highly responsive to changes in locomotor recovery over a 30day period, with a standardized response mean of 1.34. COMPARISON WITH EXISTING METHODS: Concurrent validity was good, with strong correlations observed between the cBBB and two other locomotor scales, the OSCIS (r=0.94; p<0.001) and the MFS (r=0.85; p<0.0001). cBBB scores inversely correlated with other assessments of recovery including mechanical sensory threshold (r=-0.68; p<0.0001) and coefficient of variation of stride length (r=-0.49; p<0.0001). CONCLUSIONS: These results support the use of the cBBB to assess locomotor recovery in canine clinical translational models of SCI.

Spina Bifida, Meningomyelocele, and Meningocele.

Spina bifida with or without meningocele or meningomyelocele is encountered infrequently in small animal practice. The English bulldog and Manx cat are breeds predisposed. Although often silent clinically, in those animals with clinical signs, it is important to recognize the signs early and to understand the appropriate imaging modalities employed in establishing a diagnosis. In a select population of affected animals, proposed surgical intervention may be considered to prevent neurologic decline, prevent secondary complications, and potentially improve outcomes.

Long-term survival in a dog with meningoencephalitis and epidural abscessation due to Actinomyces species.

A 2-year-old, female spayed Golden Retriever dog was presented to The Ohio State University Veterinary Medical Center for evaluation of ataxia, cervical pain, 1 episode of acute collapse, dull mentation, and inappetence. Physical examination revealed an elevated temperature of 39.7°C and severe cervical pain. Blood work revealed a mature neutrophilia. Cerebrospinal fluid (CSF) analysis revealed nondegenerative neutrophilic pleocytosis with no infectious agents. A presumptive diagnosis of steroid-responsive meningitis-arteritis was made, and corticosteroid therapy was started. The patient improved initially but experienced a vestibular episode characterized by falling and vertical nystagmus. A magnetic resonance imaging of the brain revealed an epidural abscess in the cervical vertebral canal and diffuse meningeal enhancement in the brain and cranial cervical spine. Abscess drainage revealed degenerate neutrophils and several filamentous, branching organisms. Culture of the initial CSF using an enrichment broth revealed growth of a Gram-positive organism 5 days after fluid collection. The isolate was identified by partial 16S ribosomal DNA sequencing as Actinomyces spp. The patient was successfully treated with long-term antibiotics. Our study reports the long-term survival after medical treatment of bacterial meningoencephalitis and epidural abscessation due to Actinomyces sp. infection in a dog. Bacterial meningoencephalitis should be included as a differential diagnosis in patients with cervical pain and fever, even when a nondegenerative neutrophilic pleocytosis is found on CSF analysis. Culture of the CSF with use of an enrichment broth should be considered in all cases of neutrophilic pleocytosis to rule out infections of the central nervous system.

Surgical correction of a sacral meningomyelocele in a dog.

A 15 wk old male unilateral cryptorchid German shepherd dog weighing 18 kg was referred for a nonhealing cutaneous lesion dorsally at the level of the sacrum, urinary incontinence, and a deviated tail. MRI revealed spina bifida and meningomyelocele continuous with the skin surface. Surgical correction of the meningomyelocele involved closure of the open meningeal defect, transection of the abnormal spinal nerves to the skin surface, and closure of the skin defect with a good outcome. Histopathology confirmed a meningomyelocele. This case report describes the MRI findings, surgical procedure, and proposed pathogenesis of spina bifida and meningomyelocele in a dog.

Suspected epidural morphine analgesia induced chronic urinary and bowel dysfunction in a cat.

A 12-year-old male castrated domestic shorthair developed chronic urinary retention, constipation and a decreased perineal reflex following a single lumbo-sacral epidural injection of morphine during general anesthesia. Similar adverse effects have been reported in humans following epidural analgesia, but this is the first reported case of both urinary and bowel dysfunction in a cat purportedly from an epidural. The cat was medically managed with manual bladder expressions, intermittent enemas, and various medications including bethanechol, cisapride and stool softeners. The cat continues to have long-term neurologic dysfunction 15 months post-onset. This case report describes a rare but serious potential risk of lumbo-sacral epidural injections in cats.