Objective—To determine the relationship between different body positions during recumbency on the cranial migration of epidurally injected methylene blue in canine cadavers.
Sample Population—21 fresh cadavers of clinically normal adult female mixed-breed dogs.
Procedure—Dogs were randomly assigned to the following 3 groups: dogs remaining in right lateral recumbency (n = 7), dogs rotated from left to right lateral recumbency (7), and dogs rotated from dorsal to right lateral recumbency (7). Each dog received an epidural injection of 0.05% methylene blue (0.1 mL/kg) at the lumbosacral space. A dorsal laminectomy of the vertebral column was made, and cranial extent of methylene blue in 4 quadrants (right lateral, left lateral, ventral, and dorsal) was determined by examining dura mater staining.
Results—No significant difference was found among groups in regard to body weight or body condition score. Epidural cranial migration of methylene blue in the right lateral quadrant was significantly greater in dogs that remained in right lateral recumbency than in dogs that were rotated from left to right lateral recumbency. No significant difference was found within groups for epidural cranial migration of methylene blue between each quadrant. No significant relationship was found between body weight or body condition score and epidural cranial migration of methylene blue.
Conclusions and Clinical Relevance—Body positioning and amount of recumbency time influence cranial migration of epidurally injected methylene blue. If greater cranial migration of an epidurally administered drug is desired, placing the patient in lateral recumbency with the surgical site on the dependent side may precede surgery.
Objective—To measure concentrations of glutamate, aspartate, γ-aminobutyric acid (GABA), and glycine in CSF of dogs with experimentally induced subarachnoid hemorrhage (SAH) and to assess effects of cyclosporine and simvastatin on these concentrations.
Sample—CSF samples from 13 dogs.
Procedures—In a previous study, SAH was induced in dogs via 2 injections of autologous blood into the cerebellomedullary cistern 24 hours apart. Dogs were untreated (control; n = 5) or received simvastatin alone (4) or simvastatin in combination with cyclosporine (4). Samples of CSF were collected before the first blood injection (baseline; time 0), before the second blood injection, and on days 3, 7, and 10. For the study reported here, neurotransmitter concentrations in CSF were analyzed via high-performance liquid chromatography. Data were analyzed with a repeated-measures model with adjustments for multiple comparisons by use of the Tukey method.
Results—In control dogs, the glutamate concentration peaked on day 3 and there was a significant increase in GABA and glutamate concentrations. Glutamate concentrations were significantly lower and glycine concentrations significantly higher on day 3 after administration of simvastatin alone or simvastatin in combination with cyclosporine, compared with concentrations for the control group. No significant differences in GABA and aspartate concentrations were detected among treatment groups at any time point.
Conclusions and Clinical Relevance—Glutamate concentrations were increased in the CSF of dogs with SAH. Simvastatin administration attenuated high glutamate concentrations. A combination of immunosuppression and upregulation of nitric oxide synthase may be useful in lowering high glutamate concentrations in ischemic CNS conditions.
Objective—To investigate differences in CSF concentrations of excitatory and inhibitory neurotransmitters in dogs with and without T2-weighted (T2W) MRI hyperintense areas in the limbic system.
Sample—Archived CSF samples and stored brain MRI images of 5 healthy research dogs (group 1), 8 dogs with idiopathic epilepsy (IE) with no abnormal MRI findings (group 2), and 4 dogs with IE with hyperintense areas in the limbic system detected by means of T2W MRI (group 3).
Procedures—Archived CSF samples and stored MRI images obtained from all dogs were evaluated. Dogs in groups 2 and 3 were matched on the basis of age and breed. High-performance liquid chromatography was used to evaluate glutamate and γ-aminobutyric acid (GABA) concentrations in CSF samples.
Results—Glutamate concentrations were higher in CSF of both groups of dogs with IE than in healthy dogs. However, glutamate concentrations in CSF were not significantly higher in dogs with IE and with hyperintense areas than in dogs with IE but no abnormal MRI findings. Concentrations of GABA in CSF were higher in group 3 than in group 2 and in group 2 than in group 1.
Conclusions and Clinical Relevance—No significant difference was evident between glutamate concentrations in CSF of dogs with IE and with and without hyperintense areas detected by means of T2W MRI. However, glutamate concentrations typically were higher in CSF of dogs with IE and MRI hyperintense areas. Future studies with larger sample sizes should be conducted to confirm this finding and to determine the clinical importance of high glutamate concentrations in CSF of dogs with IE.
Case Description—A 17-month-old 7-kg (15.4-lb) Shih Tzu was evaluated because of progressive thoracic limb weakness of 3 months' duration.
Clinical Findings—Neuroanatomic diagnosis was consistent with a lesion affecting the cervicothoracic (C6 through T2) spinal cord segments. Electrophysiologic testing revealed abnormal spontaneous activity in the thoracic limbs. Via magnetic resonance (MR) imaging, a lesion in the spinal cord that extended from the C5 through C7 vertebrae was detected, as were symmetric lesions in the cranial portion of the cervical spinal cord, caudal colliculi, and vestibular and cerebellar nuclei. Tests to detect metabolites indicative of inborn errors in metabolism revealed no abnormalities.
Treatment and Outcome—Prior to undergoing MR imaging, the dog received clindamycin (14 mg/kg [6.4 mg/lb], PO, q 12 h), trimethoprim-sulfadiazine (17 mg/kg [7.7 mg/lb], PO, q 12 h), and prednisone (1 mg/kg [0.45 mg/lb], PO, q 24 h). Because of its deteriorating condition, the dog was euthanized. During necropsy, gross lesions were identified in the cervical spinal cord, caudal colliculi, and vestibular and cerebellar nuclei (corresponding to lesions detected via MR imaging). Microscopic evaluation of the brain and spinal cord revealed polioencephalomyelopathy; there was severe spongiosis of the neuropil with reactive astrocytes (many with high numbers of swollen mitochondria) and preservation of large neurons.
Clinical Relevance—The form of polioencephalomyelopathy in the Shih Tzu of this report was similar to that described for Australian Cattle dogs; the similarity of findings in dogs with those in humans with Leigh disease is suggestive of a mitochondrial defect.