Rodney S. Bagley

Practical small animal MRI.

Preface. 1. Physics. Section 1. Comparative Imaging ( Patrick R. Gavin ) Section 2. Basic Physics ( Patrick R. Gavin ). Section 3. Sequence Selection ( Patrick R. Gavin ). Section 4. Artifacts ( Patrick R. Gavin ). Section 5. Equipment Consideration and Selection ( Patrick R. Gavin ). 2. Veterinary Clinical Magnetic Resonance Imagin. Section 1. Diagnosis of Intracranial Disease ( Rodney S. Bagley, Patrick R. Gavin, and Shannon P. Holmes ). Section 2. Diagnosis of Spinal Disease ( Rodney S. Bagley, Patrick R. Gavin, and Shannon P. Holmes ). Section 3. Magnetic Resonance Imaging of Peripheral Nerve Disease ( Rodney S. Bagley, Patrick R. Gavin, and Shannon P. Holmes ). 3. Orthopedic ( Patrick R. Gavin and Shannon P. Holmes ). 4. Magnetic Resonance Imaging of Abdominal Disease ( Patrick R. Gavin and Shannon P. Holmes ). 5. Thorax ( Patrick R. Gavin and Shannon P. Holmes ). 6. Head-Non-CNS ( Patrick R. Gavin and Shannon P. Holmes ). 7. Cancer Imaging ( Susan L. Kraft ). Index.

SPINAL FRACTURE OR LUXATION

Spinal trauma is a common cause of spinal cord dysfunction in dogs and cats. When the spine is injured by exogenous injury, the impact often results in vertebral fracture or luxation. As each injury is unique, treatment guidelines have to be individualized to the animal. This article reviews the clinical management including surgical and nonsurgical treatments for animals with vertebral fracture/luxation.

P-glycoprotein contributes to the blood-brain, but not blood-cerebrospinal fluid, barrier in a spontaneous canine p-glycoprotein knockout model.

P-glycoprotein is considered to be a major factor impeding effective drug therapy for many diseases of the central nervous system (CNS). Thus, efforts are being made to gain a better understanding of P-glycoproteins role in drug distribution to brain parenchyma and cerebrospinal fluid (CSF). The goal of this study was to validate and introduce a novel P-glycoprotein–deficient (ABCB1-1Δ) canine model for studying P-glycoprotein–mediated effects of drug distribution to brain tissue and CSF. CSF concentrations of drug are often used to correlate efficacy of CNS drug therapy as a surrogate for determining drug concentration in brain tissue. A secondary goal of this study was to investigate the validity of using CSF concentrations of P-glycoprotein substrates to predict brain tissue concentrations. Loperamide, an opioid that is excluded from the brain by P-glycoprotein, was used to confirm a P-glycoprotein–null phenotype in the dog model. ABCB1-1Δ dogs experienced CNS depression following loperamide administration, whereas ABCB1 wild-type dogs experienced no CNS depression. In summary, we have validated a novel P-glycoprotein–deficient canine model and have used the model to investigate transport of the P-glycoprotein substrate 99mTc-sestamibi at the blood-brain barrier and blood-CSF barrier.

Seizures as a Complication of Brain Tumors in Dogs

Seizures are a common reflection of a variety of intracranial physiologic abnormalities in dogs. In dogs with brain tumors, seizures often provide the clinical clue to the existence of an underlying structural brain disease. The majority of brain tumors that result in seizures affect the supratentorial nervous system, especially the olfactory and frontal lobes. Diagnosis requires advanced imaging such as computed tomography (CT) or magnetic resonance imaging (MRI) to establish the presence of a structural abnormality. Therapy is directed both at tumor and seizure control to afford the best chance of successful management of dogs with brain tumors.

Outcomes and complications associated with ventral screws, pins, and polymethyl methacrylate for atlantoaxial instability in 12 dogs.

Clinical outcomes and complications of a technique used for atlantoaxial stabilization were evaluated in a group of 12 dogs. At surgery, the atlantoaxial joint was realigned and rigidly fixated using cortical bone screws, K-wire, and polymethyl methacrylate. Results in nine dogs were graded as excellent. Results in two dogs were judged as good. One dog was euthanized 17 months after surgery for recurrent cervical pain. Eight dogs had no postoperative complications. The surgical technique described provided an adaptable method for the correction of atlantoaxial instability.

Surgical Treatments for Seizure: Adaptability for Dogs

Surgical treatments are often used for human epileptics who are refractory to more conventional anticonvulsant therapies. The goals of surgery are to decrease seizure morbidity or, ideally, bring about a cure to the seizure disorder. As a sizable subpopulation of dogs with seizures are also refractory to currently available anticonvulsant therapies, consideration has been given to evaluating alternative treatments for seizures in dogs. This article discusses the adaptability of surgical treatments used in humans for use in seizure control in affected dogs.

In vitro biomechanical evaluations of screw-bar-polymethylmethacrylate and pin-polymethylmethacrylate internal fixation implants used to stabilize the vertebral motion unit of the fourth and fifth cervical vertebrae in vertebral column specimens from dogs.

OBJECTIVE To determine the change in stiffness as evaluated by the dorsal bending moment of cervical vertebral specimens obtained from canine cadavers after internally stabilizing the vertebral motion unit (VMU) of C4 and C5 with a traditional pin-polymethylmethacrylate (PMMA) fixation implant or a novel screw-bar-PMMA fixation implant. SAMPLE POPULATION 12 vertebral column specimens (C3 through C6) obtained from canine cadavers. PROCEDURES A dorsal bending moment was applied to the vertebral specimens before and after fixation of the VMU of C4 and C5 by use of a traditional pin-PMMA implant or a novel screw-bar-PMMA implant. Biomechanical data were collected and compared within a specimen (unaltered vs treated) and between treatment groups. Additionally, implant placement was evaluated after biomechanical testing to screen for penetration of the transverse foramen or vertebral canal by the pins or screws. RESULTS Treated vertebral specimens were significantly stiffer than unaltered specimens. There was no significant difference in stiffness between vertebral specimen groups after treatment. None of the screws in the novel screw-bar-PMMA implant group penetrated the transverse foramen or vertebral canal, whereas there was mild to severe penetration for 22 of 24 (92%) pins in the traditional pin-PMMA implant group. CONCLUSIONS AND CLINICAL RELEVANCE Both fixation treatments altered the biomechanical properties of the cervical vertebral specimens as evaluated by the dorsal bending moment. There was reduced incidence of penetration of the transverse foramen or vertebral canal with the novel screw-bar-PMMA implant, compared with the incidence for the traditional pin-PMMA implant.

REALIGNMENT OF A SEVENTH LUMBAR VERTEBRAL FRACTURE/LUXATION USING A SENN RETRACTOR IN TWO PUPPIES

Two puppies, each with fractures of the seventh lumbar (L7) vertebra, had their vertebral canals aligned surgically with the aid of a Senn retractor. The retractor was used to provide leverage during vertebral manipulations. Surgical fixation was achieved using Steinmann pins and polymethylmethacrylate. Both puppies were improved immediately after surgery and were clinically normal six months after surgery.Two puppies, each with fractures of the seventh lumbar (L7) vertebra, had their vertebral canals aligned surgically with the aid of a Senn retractor. The retractor was used to provide leverage during vertebral manipulations. Surgical fixation was achieved using Steinmann pins and polymethylmethacrylate. Both puppies were improved immediately after surgery and were clinically normal six months after surgery.

Gamma-irradiated calvarium allograft cranioplasty in a cat following brain tumor removal.

A 14-year-old domestic shorthair cat was evaluated for a 3-month history of head pressing and circling. Neurological examination suggested a supratentorial problem, predominantly on the left side. An extradural mass extending from the rostral frontal lobes caudally to the level of the caudal aspect of the corpus callosum was found with magnetic resonance imaging. A bilateral rostrotentorial craniectomy combined with a frontal sinus craniectomy was performed for mass removal. A gamma-irradiated calvarial allograft was used to repair the calvarial defect. At 14 months following surgery, the cat had no neurological abnormalities, and the skull and facial appearance was normal.

Common Neurologic Diseases of Older Animals

Of the various neurologic diseases that affect dogs and cats, some are more often encountered in older animals. Physical diagnosis may be challenging, as multiple disease processes that may minic neurologic disease can be present in the same animal. A diligent, complete neurologic examination should lend for an accurate neuroanatomical diagnosis. Once a level of involvement is determined, knowledge of diseases affecting the particular area of the nervous system will provide for appropriate diagnosis, treatment, and prognosis. Although neurologic diseases are still often devastating, successful management of many of these diseases will afford better quality of life during the geriatric years.