CASE DESCRIPTION A 5-year-old castrated male Maltese was evaluated for intermittent clinical signs of muscle cramping and abnormal movements of the skin of the right pelvic limb at the site where an infiltrative lipoma had twice been resected. After the second surgery, the surgical field was treated with radiation therapy (RT). The clinical signs developed approximately 14 months after completion of RT.
CLINICAL FINDINGS When clinical signs were present, the right biceps femoris and semitendinosus muscles in the area that received RT were firm and had frequently visible contractions, and the skin overlying those muscles had episodic vermiform movements. Electromyography of those muscles revealed abnormal spontaneous activity with characteristics consistent with myokymic discharges and neuromyotonia. Magnetic resonance imaging of the affected leg revealed no evidence of tumor regrowth. The myokymia and neuromyotonia were considered secondary to RT.
TREATMENT AND OUTCOME 4 U of Clostridium botulinum toxin type A (BoNT-A) neurotoxin complex was injected into the affected muscles at each of 6 sites twice during a 24-hour period (ie, 48 U of BoNT-A were administered). The clinical signs were completely resolved 10 days after BoNT-A treatment and were controlled by repeated BoNT-A treatment every 3 to 4 months for > 1 year.
CLINICAL RELEVANCE To our knowledge, this is the first report of myokymia and neuromyotonia secondary to RT in a dog. For the dog of this report, injection of BoNT-A into the affected muscles was safe, effective, and easy to perform.
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.
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.
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.
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.
Objective—To compare the pharmacokinetics of a novel bioadhesive gel formulation of midazolam after intranasal (IN) administration with that of midazolam solution after IN, IV, and rectal administration to dogs.
Animals—10 (5 males and 5 females) healthy adult Beagles.
Procedures—Dogs were assigned to 4 treatment groups for a crossover study design. Initially, midazolam solution (5 mg/mL) was administered (0.2 mg/kg) IV to group 1, rectally to group 2, and IN to group 3; a 0.4% hydroxypropyl methylcellulose midazolam gel formulation (50 mg/mL) was administered (0.2 mg/kg, IN) to group 4. Each dog received all 4 treatments; there was a 7-day washout period between subsequent treatments. Blood samples were collected before and after midazolam administration. Plasma concentration of midazolam was determined by use of high-performance liquid chromatography.
Results—The peak plasma concentration after IN administration of the gel formulation was significantly higher than that after IN and rectal administration of the solution. Mean ± SD time to peak concentration was 11.70 ± 2.63 minutes (gel IN), 17.50 ± 2.64 minutes (solution IN), and 39 ± 14.49 minutes (solution rectally). Mean bioavailability of midazolam was 70.4% (gel IN), 52.0% (solution IN), and 49.0% (solution rectally). Bioavailability after IN administration of the gel formulation was significantly higher than that after IN and rectal administration of the solution.
Conclusions and Clinical Relevance—IN administration of midazolam gel was superior to both IN and rectal administration of midazolam solution with respect to peak plasma concentration and bioavailability.
Objective—To determine complications and neurologic outcomes associated with dexamethasone administration to dogs with surgically treated thoracolumbar intervertebral disk herniation, compared with dogs not receiving dexamethasone.
Design—Retrospective case series.
Animals—161 dogs with surgically confirmed thoracolumbar disk herniation.
Procedures—Medical records from 2 hospitals were used to identify dogs that had received dexamethasone < 48 hours prior to admission (dexamethasone group dogs), dogs that received glucocorticoids other than dexamethasone < 48 hours prior to admission (other-glucocorticoid group dogs), and dogs that received no glucocorticoids (nontreatment group dogs). Signalment, neurologic injury grade, laboratory data, and complications were extracted from medical records.
Results—Dexamethasone group dogs were 3.4 times as likely to have a complication, compared with other-glucocorticoid or nontreatment group dogs. Dexamethasone group dogs were 11.4 times as likely to have a urinary tract infection and 3.5 times as likely to have diarrhea, compared with other-glucocorticoid or nontreatment group dogs. No differences in neurologic function at discharge or recheck evaluation were detected among groups.
Conclusions and Clinical Relevance—Results indicated that treatment with dexamethasone before surgery is associated with more adverse effects, compared with treatment with glucocorticoids other than dexamethasone or no treatment with glucocorticoids, in dogs with thoracolumbar intervertebral disk herniation. In this study population, no difference in outcome was found among groups. These findings suggest that the value of dexamethasone administration before surgery in dogs with thoracolumbar disk herniation should be reconsidered.
To determine the most common indications for cranial surgery and identify risk factors associated with the occurrence of complications and death in the perioperative period following cranial surgery.
150 dogs and 15 cats.
For this multi-institutional retrospective case series, medical records of dogs and cats that underwent cranial surgery at any of the 4 participating institutions between 1995 and 2016 were reviewed. Variables were evaluated included species, sex, age, neurolocalization, history of preoperative seizures, surgical approach, histological results, perioperative complications, and outcome. Logistic regression analysis was performed to assess for risk factors for complications.
The most common neurolocalization was the forebrain (110/165 [66.7%]), with 94 (57.0%) animals having had seizures preoperatively. The rostrotentorial (116/165 [70.3%]) and caudotentorial (32/165 [19.4%]) surgical approaches were most commonly reported. The most common indication was the treatment of meningioma (75/142 [52.8%]). Complications arose in 58 of the 165 (35.2%) cases within 24 hours and in 86 (52.1%) cases 1 to 10 days postoperatively. Perioperative complications included hypotension (38/165 [23.0%]) and anemia (27/165 [16.4%]). During the postoperative period, the most common complications were neurologic deficits, seizures, postoperative anemia, and aspiration pneumonia. The mortality rate with death or euthanasia perioperatively or ≤ 10 days postoperatively was 14.5% (24/165). Long-term complications occurred in 65 of the 165 (39.4%) animals, with seizures and neurologic deficits being the most common.
Cranial surgery was performed most commonly for the removal of neoplastic lesions in dogs and cats, and most complications were not life-threatening.
3 dogs were examined because of a sudden onset of signs of pain (1 dog) or paraparesis (2 dogs).
Neurologic findings consisted of myelopathy affecting the lumbar intumescence (1 dog) and T3-L3 myelopathy (2 dogs). In all dogs, MRI revealed spinal cord compression caused by L3-4 disk herniation. All dogs underwent routine surgical decompression of the intervertebral disk herniation. During MRI and decompressive surgery, physiologic variables were monitored. Immediately after surgery, all dogs were paraplegic with pelvic limb neurologic dysfunction consistent with myelopathy affecting the L4 through caudal spinal cord segments.
TREATMENT AND OUTCOME
Within 24 hours after surgery, repeated MRI in all dogs revealed hyperintensity in the spinal cord gray matter of the lumbar intumescence on T2-weighted images. In the absence of neurologic improvement, dogs were euthanized at 3, 91, and 34 days after surgery. Postmortem microscopic examination of each dog's spinal cord at the lumbar intumescence revealed necrosis of the gray matter with relative white matter preservation suggestive of an ischemic injury.
Dramatic neurologic deterioration following decompressive surgery for intervertebral disk herniation in dogs may be associated with the development of poliomyelomalacia secondary to ischemia. In these 3 dogs, ischemia developed despite probable maintenance of normal spinal cord blood flow and perfusion during anesthesia. To exclude other causes, such as compression or hemorrhage, MRI was repeated and revealed hyperintensity of the spinal cord gray matter on T2-weighted images, which microscopically corresponded with ischemic neurons and neuronal loss.