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Biomedical subjects

W B Thomas

Publications and source records attributed to W B Thomas.

At least 19 recordsLinked to original sources

Initial assessment of patients with neurologic dysfunction.

This article describes a practical approach to the initial assessment of patients with neurologic dysfunction. First, the patient's clinical signs are determined by obtaining a medical history and performing an examination. Based on these results, the disease is localized to a particular region of the nervous system. Analysis of the neuroanatomic diagnosis in conjunction with the history is used to establish a list of differential diagnoses. The clinician then recommends appropriate laboratory tests to confirm or exclude the diagnostic possibilities. By following a logical process of clinical reasoning, the practitioner is often able to deduce a clinical diagnosis and prognosis and offer recommendations for treatment.

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Degenerative lumbosacral stenosis.

This article reviews the management of degenerative lumbosacral stenosis. Degenerative lumbosacral stenosis occurs when soft tissue and bony changes, possibly in conjunction with abnormal motion of the lumbosacral joint, impinge on the nerve roots or vasculature of the cauda equina. It occurs most frequently in middle-aged dogs of medium to large breed, especially the German Shepherd dog. Common signs are lumbosacral pain, lameness, pelvic limb weakness and ataxia, and urinary incontinence. Diagnosis is based on clinical features and imaging studies. Decompressive surgery is effective in most patients.

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Diskospondylitis and other vertebral infections.

This article discusses infections of the spine, including diskospondylitis, vertebral osteomyelitis, and vertebral physitis. Spinal pain is the most common clinical sign. Plain radiography is usually diagnostic; computed tomography and magnetic resonance imaging are useful when the diagnosis is unclear. Serology for Brucella canis and cultures of blood and urine are important in identifying the cause. Appropriate antibiotic therapy is successful in the majority of cases of bacterial spinal infection.

Animals↗

Idiopathic epilepsy in dogs.

Idiopathic epilepsy is a chronic condition characterized by recurrent seizures for which there is no identifiable cause. It is the most common neurologic disorder in the dog. This article discusses the diagnostic evaluation and rational treatment of dogs with recurrent seizures. Types of seizures, client education, choice of therapy, use of specific drugs, therapeutic monitoring, and nondrug treatments are reviewed.

Animals↗

Vestibular dysfunction.

Vestibular dysfunction can be caused by damage to the peripheral or central components of the vestibular system. Signs of vestibular disease include ataxia, head tilt, and abnormal nystagmus. This article reviews the pathophysiology, diagnosis, and management of common vestibular disorders in dogs and cats.

Animals↗

Nonneoplastic disorders of the brain.

Computed tomography (CT) and magnetic resonance imaging (MRI) are helpful in the diagnosis of many nonneoplastic brain disorders in the dog and cat. The ability of CT and MRI to depict normal and abnormal anatomy facilitates the identification of developmental anomalies, including hydrocephalus, Chiari malformations, arachnoid cysts, and cerebellar hypoplasia. These imaging modalities also allow the detection of hemorrhage and infarction and are therefore useful in the evaluation of spontaneous cerebrovascular disorders and head trauma. Finally, many inflammatory diseases, such as encephalitis, brain abscess, and parasite migration, cause abnormalities detectable by CT and MRI. Although more research on the imaging features of specific nonneoplastic brain disorders is needed, current information indicates that CT and MRI are useful in the management of these disorders.

Animals↗

Inflammatory diseases of the central nervous system in dogs.

Inflammatory diseases of the central nervous system (CNS) are important causes of seizures in dogs. Specific diseases include canine distemper, rabies, cryptococcosis, coccidioidomycosis, toxoplasmosis, neosporosis, Rocky Mountain spotted fever, ehrlichiosis, granulomatous meningoencephalomyelitis, and pug dog encephalitis. Inflammatory disorders should be considered when a dog with seizures has persistent neurological deficits, suffers an onset of seizures at less than 1 or greater than 5 years of age, or exhibits signs of systemic illness. A thorough history, examination, and analysis of cerebrospinal fluid are important in the diagnosis of inflammatory diseases. However, even with extensive diagnostic testing, a specific etiology is identified in less than two thirds of dogs with inflammatory diseases of the CNS.

Animals↗

Cerebrovascular disease.

Cerebrovascular disease may be secondary to various disorders including hypothyroidism, sepsis, neoplasia, hypertension, vascular malformation, and coagulopathy. Brain infarction or hemorrhage should be suspected in an animal with a sudden onset of a focal brain lesion. The recent availability of CT and MRI has improved our ability to diagnose cerebrovascular disease in animals. Treatment is directed at maintaining adequate oxygenation of the brain, controlling elevations of ICP, treating seizures, and identifying and treating any underlying disease. With appropriate care, many animals can recover.

Animals↗

Ultrasound-guided brain biopsy in dogs.

Ultrasound-guided brain biopsy of the cingulate gyrus and the head of the caudate nucleus was performed in clinically normal dogs. Dogs survived the surgery, and neurologic deficits were not detected in the 14-day postoperative period. Magnetic resonance imaging detected changes in the brain associated with biopsy in 9 dogs (90%) immediately after surgery and in 6 dogs (60%) 14 days after surgery. Fourteen days after surgery, sonography of the brain, performed through the skin overlying the burr hole, detected changes associated with biopsy in 9 dogs (90%). Histopathologic changes evident in the brain 14 days after surgery consisted of focal malacia and hemorrhage with associated subacute encephalomeningitis. Postmortem examination indicated that the biopsy specimen was accurately obtained from the desired site in 9 dogs (90%). Tissue specimens suitable for histologic examination were obtained from 10 dogs (100%). Accuracy and low morbidity of ultrasound-guided biopsy indicate that this may be a useful technique for diagnosis of focal brain disease in dogs.

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Surgical management of atlantoaxial subluxation in 23 dogs.

Twenty-eight surgical procedures were performed in 23 dogs with atlantoaxial subluxation. Dorsal stabilization in seven dogs resulted in two recoveries and five failures of fixation. Ventral decompression and stabilization in 18 dogs resulted in eight recoveries and four failures of fixation. Six dogs died or were euthanatized within 7 days of ventral stabilization. Using either technique, four of seven nonambulatory dogs recovered.

Animals↗

Parosteal osteosarcoma of the cervical vertebra in a dog.

A 12-year-old Maltese terrier was evaluated for progressive tetraparesis and neck pain. On radiographs, there was a periosteal reaction involving the fourth cervical vertebra. Myelographically, there was extradural compression of the spinal cord associated with the lesion. The dog was euthanized and necropsied. Histopathologic diagnosis was parosteal osteosarcoma of the vertebra.

Animals↗

Magnetic resonance imaging appearance of intracranial hemorrhage secondary to cerebral vascular malformation in a dog.

A 14-year-old dog developed an acute onset of depression, disorientation, left hemiparesis,left hemianopia, left facial hypoesthesia, and a tendency to turn to the right. Based on these findings, a lesion affecting the right forebrain was suspected. Magnetic resonance imaging showed a mass within the right cerebral hemisphere resulting in compression of the right lateral ventricle and shifting the longitudinal fissure to the left. The lesion was hyperintense on T1-weighted images and hyperintense with focal regions of hypointensity on proton density-, and T2-weighted images, consistent with a subacute hemorrhage. At necropsy, there was a hematoma in the parietal portion of the right cerebral hemisphere. The hemorrhage was surrounded by numerous thin-walled veins, most likely a venous malformation. Magnetic resonance imaging of intracranial hemorrhage is reviewed.

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Muscular dystrophy in female dogs.

The most common form of muscular dystrophy in dogs and humans is caused by mutations in the dystrophin gene. The dystrophin gene is located on the X chromosome, and, therefore, disease-causing mutations in dystrophin occur most often in males. Therefore, females with dystrophin deficiency or other forms of muscular dystrophy may be undiagnosed or misdiagnosed. Immunohistochemistry was used to analyze dystrophin and a number of other muscle proteins associated with muscular dystrophy in humans, including sarcoglycans and laminin alpha2, in muscle biopsy specimens from 5 female dogs with pathologic changes consistent with muscular dystrophy. The female dogs were presented with a variety of clinical signs including generalized weakness, muscle wasting, tremors, exercise intolerance, gait abnormalities, and limb deformity. Serum creatine kinase activity was variably high. One dog had no detectable dystrophin in the muscle; another was mosaic, with some fibers normal and others partly dystrophin-deficient. A 3rd dog had normal dystrophin but no detectable laminin alpha2. Two dogs could not be classified. This study demonstrates the occurrence of dystrophin- and laminin alpha2-associated muscular dystrophy and the difficulty in clinical diagnosis of these disorders in female dogs.

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Clinical features of trigeminal nerve-sheath tumor in 10 dogs.

Nerve-sheath tumor was diagnosed in 10 dogs with clinical signs of unilateral trigeminal nerve dysfunction. Unilateral temporalis and masseter muscle atrophy were present in all cases. An enlarged foramen and distorted rostral petrous temporal bone were seen with computed tomography imaging in one case. Magnetic resonance imaging was used to identify the lesion accurately in seven cases. Surgery was performed for biopsy and lesion removal in three cases. Cases not treated had a progressive course eventually resulting in euthanasia or death. Of the cases treated surgically, one case is alive without disease progression 27 months after surgery. Survival times of the nontreated cases ranged from five to 21 months.

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