Cervical spinal intradural arachnoid cysts in related,young pugs

Seven related young pugs were diagnosed with cervical spinal intradural arachnoid cysts by magnetic resonance imaging (n = 6) and myelography (n = 1). All dogs were presented with skin abrasions on their thoracic limbs and non‐painful neurological deficits, indicating a C1‐T2 myelopathy. In all six dogs examined by magnetic resonance imaging not only the spinal arachnoid cyst but also a concomitant, most likely secondary, syringohydromyelia was confirmed. Pedigree analysis suggested a genetic predisposition for spinal arachnoid cysts in this family of pugs. Generalised proprioceptive deficits more pronounced in the thoracic limbs suggesting a focal cervical spinal cord lesion, with concomitant skin abrasions on the dorsal aspect of the thoracic limbs in a young pug, should alert veterinarians to the possibility of cervical spinal arachnoid cysts.     

Toxoplasma gondii brain granuloma in a cat: diagnosis using cytology from an intraoperative sample and sequential magnetic resonance imaging

A cat with a history of seizures and clinical suspicion of forebrain disorder underwent a brain magnetic resonance imaging. A space-occupying lesion was identified in the left temporal lobe. The mass was surgically removed, and cytological, histological and immunohistochemical examinations documented the presence of Toxoplasma gondii. A definitive diagnosis of an intracranial T gondii granuloma was made. The cat was treated with clindamycin and phenobarbital and the seizures did not recur. After 10 months, a second magnetic resonance imaging showed severe brain atrophy, but T gondii granuloma recurrence was not noted. Twenty-one months after surgery, the cat's condition deteriorated, and another magnetic resonance imaging showed a presumptive recurrence of T gondii granuloma. In cats, T gondii granuloma must be considered as a differential diagnosis even when only a single intracranial mass is present. Cytology and magnetic resonance imaging can be useful in making a definitive diagnosis and to follow the evolution of the lesion.     

Computed tomographic arthrography is a useful adjunct to survey computed tomography and arthroscopic evaluation of the canine shoulder joint

The aim of this retrospective, methods comparison study was to assess the diagnostic utility of computed tomographic arthrography in the assessment of various intraarticular shoulder pathologies in dogs in comparison with survey computed tomography (CT), using arthroscopic examination as the reference standard. Computed tomography, computed tomographic arthrography, and arthroscopic findings of 46 scapulohumeral joints of dogs with forelimb lameness were reviewed retrospectively. Predefined sites were assessed for the presence or absence of disease. If a lesion was present, a prespecified pathology was designated. Computed tomographic arthrography was found to be a safe technique which provided a superior diagnostic efficacy relative to survey CT for the assessment of the biceps tendon and biceps tendon sheath (sensitivity 71%, specificity 75%, positive likelihood ratio 2.9, negative likelihood ratio 0.38) and humeral head cartilage (sensitivity 65%, specificity 97%, positive likelihood ratio 19, negative likelihood ratio 0.37). Computed tomography and computed tomographic arthrography provided additional diagnostic information to arthroscopy in regard to osteophytosis, subchondral defects, and joint mice. Computed tomographic arthrography alone was of limited diagnostic value for assessment of the medial and lateral glenohumeral ligaments (sensitivity 13% and 0%, specificity 1% and 78%, positive likelihood ratios unmeasurable and 0, negative likelihood ratios 0.88 and 1.29, respectively) and the subscapularis tendon (sensitivity 14%, specificity 98%, positive likelihood ratio 5.7, negative likelihood ratio 0.88). Computed tomographic arthrography is therefore a useful adjunct to survey CT and arthroscopic evaluation of the canine shoulder joint, however, is not a replacement for these techniques.     

Association of clinical and magnetic resonance imaging findings with outcome in dogs suspected to have ischemic myelopathy: 50 cases (2000-2006)

OBJECTIVE: To determine whether clinical signs or magnetic resonance imaging findings were associated with outcome in dogs with presumptive ischemic myelopathy. DESIGN: Retrospective case series. ANIMALS: 50 dogs. PROCEDURES: Medical records and magnetic resonance images were reviewed. A neurologic score from 1 (normal) to 5 (most severe degree of dysfunction) was assigned on the basis of neurologic signs at the time of initial examination. Follow-up information was obtained from the medical records and by means of a telephone questionnaire completed by owners and referring veterinarians. RESULTS: Median neurologic score at the time of initial examination was 3 (range, 2 to 5). Median follow-up time was 584 days (range, 4 to 2,090 days). Neurologic score at the time of initial examination and extent of the lesion seen on magnetic resonance images (quantified as the lesion length-to-vertebral length ratio and as the percentage cross-sectional area of the lesion) were significantly associated with outcome. Sensitivity of using a lesion length-to-vertebral length ratio > 2.0 or a percentage cross-sectional area of the lesion > or = 67% to predict an unsuccessful outcome was 100%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that severity of neurologic signs at the time of initial examination and extent of the lesions seen on magnetic resonance images were associated with outcome in dogs with ischemic myelopathy.     

Canine intracranial neoplasia: clinical risk factors for development of epileptic seizures

Objectives : To identify clinical risk factors for seizures in dogs with intracranial neoplasia. Methods : A cross‐sectional retrospective study of 68 dogs with histopathologically confirmed primary or secondary intracranial neoplasia, complete clinical history and magnetic resonance imaging of the brain was conducted. Signalment and clinical history were retrieved from clinical records and magnetic resonance images of the brain were re‐evaluated. Prevalence of findings was compared between dogs with and without seizures. Results : Forty‐two dogs had tumour‐related seizures, the remaining 26 were seizure‐free. Tumour types included meningioma (23 dogs with and 5 without seizures), glioma (9 dogs with and 6 without seizures), choroid plexus tumour (2 dogs without seizures), neuroblastoma (1 dog with seizures) and metastatic/invasive tumours including lymphoma (9 dogs with and 13 without seizures). On the basis of multi‐variable logistic regression analysis, risk factors for seizures associated with intracranial neoplasia were magnetic resonance imaging findings consistent with the presence of neoplastic tissue in frontal lobe [odds ratio (OR) 9·61; 95% confidence interval (CI) 2·59 to 35·61], marked gadolinium enhancement (OR 10·41; 95% CI 2·07 to 52·30) and magnetic resonance imaging findings of subfalcine and/or subtentorial herniation (OR 3·88; 95% CI 1·10 to 13·71). Clinical Significance : Dogs with primary or secondary intracranial neoplasia are at risk of seizures, particularly those with tumours that affect the frontal lobe, enhance markedly with gadolinium, or cause subfalcine and/or subtentorial herniation.     

Abnormalities of serum electrolyte concentrations in dogs with hypoadrenocorticism

BACKGROUND: The sensitivity and specificity of the sodium to potassium ratio (Na:K ratio) as a cutoff for recommendation of an adrenocorticotropic hormone (ACTH) stimulation test in dogs suspected of having hypoadrenocorticism (HA) is unknown. Additionally, abnormalities in plasma ionized calcium (iCa2+) and ionized magnesium (iMg2+) concentrations and venous pH of dogs with HA are incompletely documented. OBJECTIVES: To define the sensitivity and specificity of the Na:K ratio as a diagnostic aid for HA in dogs and to examine for associations between venous pH and the Na:K ratio, iCa2+ concentration, or iMg2+ concentration in dogs with HA. ANIMALS: Seventy-six dogs with HA and 200 dogs randomly selected from the general hospital population. METHODS: Retrospective study. Dogs were included in the study if results of an ACTH stimulation test confirmed a diagnosis of HA, the dog had a serum sodium concentration below the reference range or a serum potassium concentration above the reference range, and the dog was treated with mineralocorticoids. Receiver operating curve analysis was used to determine optimal cutoffs of sensitivity and specificity for the Na:K ratio in diagnosing HA. RESULTS: Use of Na:K ratios of 27 or 28 classified 95% of dogs correctly as diseased or not diseased. The sensitivity of a Na:K ratio of 28 was 93% (CI, 85-98%) and that of 27 was 89% (CI, 80-95%). The specificity of a Na:K ratio of 28 was 96% (CI, 92-98%) and that of 27 was 97% (CI, 93- 99%). The sensitivity and specificity of a Na:K ratio of 24 were 79% (95% CI, 67-86%) and 100% (98%, CI, 97%-100%), respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: Na:K ratios of 27 or 28 identify the highest percentage of dogs with suspected mineralocorticoid and glucocorticoid deficiency correctly. In dogs with a Na:K ratio of 24 or less, the likelihood of confirming a diagnosis of HA with an ACTH stimulation test is high.     

IMAGING DIAGNOSIS—MAGNETIC RESONANCE IMAGING FEATURES OF A CEREBRAL HEMANGIOBLASTOMA IN A DOG

The magnetic resonance (MR) imaging features of a cerebral hemangioblastoma in a 9‐year‐old dog are described. Imaging revealed a well‐defined contrast‐enhancing lesion of the rostral forebrain that appeared extraparenchymal. Histopathology of the excised mass showed clusters of small blood vessels interspersed with interstitial cells staining positive for neuronal specific enolase, features consistent with a cerebral hemangioblastoma; the mass also appeared intraparenchymal after further immunohistochemistry study. This neoplasm should be considered a rare differential diagnosis for intracranial masses in dogs.     

Fecal incontinence and spinal cord abnormalities in seven dogs

Seven dogs with fecal incontinence and abnormal gaits were evaluated. Fecal incontinence was characterized as defecation of normal stools without posturing. Duration of clinical signs prior to evaluation ranged from 5 months to 3 years. Five dogs had upper motor neuron (UMN) paraparesis, and 2 dogs had UMN tetraparesis. With magnetic resonance imaging, spinal cord abnormalities primarily involving the dorsal aspect of the spinal cord were identified in all dogs. Five dogs had focal abnormalities, and 2 dogs had diffuse abnormalities of the spinal cord. Of the dogs with focal spinal cord lesions, 4 had cystic spinal cord abnormalities and 1 had a meningioma. Surgery was performed on all dogs with focal lesions; 4 of the 5 dogs had resolution of fecal incontinence after surgery. Results in these dogs suggest that fecal incontinence can be associated with spinal cord abnormalities and, depending on the characteristics of the lesion, can resolve after surgical treatment of the abnormality.     

Prospective evaluation of techniques for differentiating shoulder pathology as a source of forelimb lameness in medium and large breed dogs

Objective— To assess lameness evaluation, shoulder abduction angles, radiography, and ultrasonography for determining presence, location, and severity of forelimb pathology. Study Design— Prospective cohort study. Animals— Dogs ≥20 kg (n=30). Methods— Each dog was assigned lameness scores. Shoulder abduction angles were determined. Radiographs of shoulders and elbows were subjectively graded for pathology. One investigator unaware of dog history (lameness, radiographic findings) performed ultrasonographic assessment of shoulders with subjective grading of pathology. Another investigator unaware of dog history (lameness, radiographic, ultrasonographic findings) performed arthroscopic assessment of shoulders with subjective grading of pathology. Elbows were disarticulated and evaluated for gross pathology. Histologic pathology scoring of shoulder tissues was performed. Data were compared for differences among groups, sensitivities, specificities, positive and negative predictive values, and positive and negative likelihood ratios were calculated. Results— Twenty‐seven forelimbs were considered clinically normal, 26 had shoulder pathology, 5 had elbow pathology, and 2 had pathology of both the shoulder and elbow. Dogs with shoulder pathology were twice as likely to be lame compared with dogs with elbow pathology. Limbs with medial shoulder instability had significantly higher abduction angles than normal limbs and those with elbow pathology. Radiographs were clinically useful for diagnosing elbow, but not shoulder, pathology. Ultrasonography was clinically useful for diagnosing shoulder pathology other than instability. Abduction angles, ultrasonographic evaluation, and arthroscopic assessments had strong, significant correlations with reference standards. Conclusions— Clinically relevant diagnostic techniques yielded characteristic, repeatable differences in objective and subjective assessments for distinguishing presence, location, and severity of forelimb lameness in dogs. Clinical Relevance— The diagnostic approach to forelimb lameness in dogs should include shoulder pathology as a differential with multiple assessments used to determine the clinical cause of lameness.     

Clinical and magnetic resonance imaging characteristics of quadrigeminal cysts in dogs

BACKGROUND: Quadrigeminal cysts (QC) are the most common intracranial intra-arachnoid cysts in dogs, primarily affecting small breeds. Clinical significance is controversial. HYPOTHESIS: Male, brachycephalic, small breed dogs are predisposed to QC, and objective measurement of parenchymal compression can distinguish clinically relevant QC from incidental findings. ANIMALS: A total of 4,100 client-owned dogs. METHODS: A retrospective study that recorded signalment, history, clinical signs, and magnetic resonance imaging features. The degree of brain compression was evaluated in the presence of relevant clinical signs. The percentage compression of cerebellum and forebrain was calculated by comparing the expected to the actual diameter and longitudinal dimension, respectively. RESULTS: QC were diagnosed in 28 dogs, of which 21 (75%) were small breed dogs. Fifteen dogs (54%) were brachycephalic. Eighteen dogs were male, and 10 were female. Cerebellar, occipital lobe, or compression in both areas occurred in 86% (24/28 dogs). Clinical signs included focal and generalized seizures in 5 dogs and cerebellar signs in 6 dogs. Mean occipital lobe compression was 17% (SD = 4) in clinically affected and 10% (SD = 3) in normal dogs (P = .006). Occipital lobe compression >14% was always associated with clinical signs. The mean cerebellar compression was 18%, but there was no association between compression and clinical signs. The animals were more likely to develop clinical signs if both areas were compressed (P = .04). CONCLUSIONS AND CLINICAL IMPORTANCE: Parenchymal compression by QC can be incidental, and other central nervous system diseases must be excluded when assessing the clinical significance of QC. However, occipital lobe compression over 14% is likely to cause clinical signs.     

Magnetic resonance imaging in two dogs with central nervous system disease

Accurate localization of the lesions in two dogs with progressive neurological disease was demonstrated with magnetic resonance imaging (MRI). The first dog had unilateral cerebellar signs with associated paradoxical vestibular symptoms. The CSF tap and clinical localization suggested a right-sided cerebellar tumour and this was confirmed with MRI scanning. The second dog had predominantly asymmetrical fore-brain signs with circling, personality changes, seizures and contralateral proprioceptive deficits. CSF analysis suggested an inflammatory or neoplastic condition. MRI showed a diffuse oedematous lesion of the left cerebral hemisphere which corresponded exactly with the lesions seen at necropsy. The advantages of MRI over CT scans are discussed.     

Rapid diagnosis of retina and optic nerve abnormalities in canine patients with and without cataracts using chromatic pupil light reflex testing

Objective To develop fast and reliable testing routines for diagnosing retina and optic nerve diseases in canine cataract patients based on chromatic properties of the pupillary light reflex response. Procedures Seventy‐seven canine patients with a history of cataract and decreased vision (43 patients with cataracts and no evidence of retina or optic nerve disease, 21 patients with cataracts and retinal degeneration [RD], 13 patients with cataracts and retinal detachment [RDT]), 11 canine patients with optic neuritis (ON) and 23 healthy dogs were examined using chromatic pupillary light reflex (cPLR) analysis with red and blue light and electroretinography. Results Electroretinography analysis showed statistically significant deficits in a‐ and b‐wave amplitudes in dogs with cataracts and RD, or cataracts and RDT, when compared to dogs with cataracts without evidence of retinal abnormalities. Evaluation of b‐wave amplitudes showed that presence of 78.5‐μV (or lower) amplitudes had high sensitivity of 100% (95% CI: 87.2–100%) and high specificity of 96.7% (95% CI: 88.4–100%) in RD and RDT. Evaluation of cPLR responses using red light showed that presence of the pupil end constriction diameter of 5.5 mm (or higher) had moderately high sensitivity of 76.5% (95% CI: 50.1–93.2%) and high specificity of 100% (95% CI: 91.2–100%) in detecting RD and RDT. Optic neuritis patients had absent cPLR responses, regardless of the visual status. Conclusions and Clinical Relevance Chromatic evaluation of the pupillary light reflex is a rapid and accurate test for diagnosing retina and optic nerve diseases in canine patients.     

Intramedullary epidermoid cyst in the thoracic spine of a dog

A 5 yr old female spayed mastiff was evaluated for a 3-4 mo history of paraparesis and 3 days of acutely worse paraparesis and incontinence. On magnetic resonance imaging, a spinal cord lesion was present at the ninth thoracic vertebra. The lesion was hyperintense on T2-weighted images (T2-W), and a hyperintense rim was present on T1-weighted postcontrast images. Histologic examination showed a cystic mass lined by squamous epithelial cells. Histopathologic diagnosis was an intramedullary epidermoid spinal cyst. Epidermoid cyst should be a differential diagnosis in young dogs with a myelopathy and an intramedullary spinal cord lesion on magnetic resonance imaging examination.     

Association between frontal-sinus size and syringohydromyelia in small-breed dogs

OBJECTIVE: To determine whether frontal-sinus size is associated with syringohydromyelia. SAMPLE POPULATION: Medical records and magnetic resonance images of 62 small-breed dogs. PROCEDURES: Medical records and magnetic resonance images were reviewed retrospectively for evaluation of frontal-sinus size and syringohydromyelia. A Yates-corrected 2-tailed chi2 test was used to determine whether an association existed between absent or miniscule frontal sinuses and syringohydromyelia. The strength of the association was evaluated by means of prevalence and odds ratios. RESULTS: Absent or miniscule air-filled frontal sinuses were detected in 28 of 62 (45%) dogs, and syringohydromyelia was detected in 12 of 62 (19%) dogs. Syringohydromyelia was detected in 10 of 28 dogs with absent or miniscule frontal sinuses (prevalence, 36%; 95% confidence interval, 16% to 55%) and in 2 of 34 dogs with larger frontal sinuses (prevalence, 6%; confidence interval, 0% to 15%). The probability of detecting syringohydromyelia in dogs with absent or miniscule air-filled frontal sinuses was significantly greater than the probability of detecting it in dogs with larger frontal sinuses. The prevalence ratio was 6.1, and the odds ratio was 8.9. CONCLUSIONS AND CLINICAL RELEVANCE: An association between frontal-sinus size and syringohydromyelia was identified in small-breed dogs, suggesting that the pathogenesis of syringohydromyelia in some instances may involve abnormal development of the entire or supratentorial part of the cranium, as opposed to being limited to the infratentorial part.     

Evaluation of magnetic resonance imaging for the differentiation of inflammatory,neoplastic, and vascular intradural spinal cord diseases in the dog

Magnetic resonance imaging (MRI) is a common test for dogs with suspected intradural spinal cord lesions, however studies on diagnostic performance for this test are lacking. Objectives of this multi‐institutional, retrospective, case‐control study were to estimate sensitivity and specificity of MRI for (1) distinguishing between histopathologically confirmed intradural spinal cord disease versus degenerative myelopathy in dogs, (2) categorizing intradural spinal cord diseases as neoplastic, inflammatory, or vascular; and (3) determining tumor type within the etiologic category of neoplasia. Additional aims were to (1) determine whether knowledge of clinical data affects sensitivity and specificity of MRI diagnoses; and (2) report interrater agreement for MRI classification of intradural spinal lesions. Cases were recruited from participating hospital databases over a 7‐year period. Three reviewers independently evaluated each MRI study prior to and after provision of clinical information. A total of 87 cases were sampled (17 degenerative myelopathy, 53 neoplasia, nine inflammatory, and eight vascular). Magnetic resonance imaging had excellent (>97.6%) sensitivity for diagnosis of intradural spinal cord lesions but specificity varied before and after provision of clinical data (68.6% vs. 82.4%, P = 0.023). Magnetic resonance imaging had good sensitivity (86.8%) and moderate specificity (64.7–72.5%) for diagnosing neoplasia. Sensitivity was lower for classifying inflammatory lesions but improved with provision of clinical data (48.1% vs. 81.5%, P = 0.015). Magnetic resonance imaging was insensitive for diagnosing vascular lesions (25.0%). Interrater agreement was very good for correctly diagnosing dogs with intradural lesions (? = 0.882–0.833), and good (? = 0.726–0.671) for diagnosing dogs with neoplasia.     

Brain abscess in seven cats due to a bite wound: MRI findings, surgical management and outcome

PRESENTATION AND LESION LOCALISATION: Seven adult domestic shorthair cats were presented with a 1- to 6-day history of progressive neurological signs. A focal skin puncture and subcutaneous swelling over the dorsal part of the head were detected on physical examination. Neurological examination indicated lesion(s) in the right forebrain in four cats, multifocal forebrain in one cat, left forebrain in one cat, and multifocal forebrain and brainstem in the remaining cat. In all cats, magnetic resonance imaging revealed a space-occupying forebrain lesion causing a severe mass effect on adjacent brain parenchyma. CLINICAL APPROACH AND OUTCOME: All cats were managed with a combination of medical and surgical treatment. At surgery a small penetrating calvarial fracture was detected in all cats, and a tooth fragment was found within the content of the abscess in two cats. The combination of surgical intervention, intensive care and intravenous antimicrobials led to a return to normal neurological function in five cats. PRACTICAL RELEVANCE: As this series of cases indicates, successful resolution of a brain abscess due to a bite injury depends on early recognition and combined used of antimicrobials and surgical intervention. A particular aim of surgery is to remove any skull and foreign body (tooth) fragments that may represent a continuing focus of infection.     

Does choice of imaging modality affect outcome in dogs with thoracolumbar spinal conditions?

Objectives : A retrospective cross-sectional study was done to look for differences in outcome in canine spinal patients that had myelography compared to those that had magnetic resonance imaging. Methods : Medical records of dogs with spinal conditions in the period January 2004 to December 2007 were reviewed. Data on patient age, gender, breed, size, neurolocalisation, rate of onset, imaging modality, time taken to image, type of treatment, neurological grade at admission and discharge, length and cost of hospitalisation and status at discharge were collected. Only dogs with neurological grade 3 to 6 with signs referable to the thoracolumbar spine were included. Results : Of 107 dogs that met the inclusion criteria, 66 (62%) had myelography and 41 (38%) had magnetic resonance imaging. Using multivariable analyses, non-chondrodystrophoid breed, increasing age and higher neurological grade at admission were found to be associated negatively with survival. Neurological grade 5 at admission was found to be associated positively with likelihood of neurological improvement. Male gender, higher neurological grade at admission and medical treatment were associated negatively with length of hospitalisation. magnetic resonance imaging, surgical treatment and period of hospitalisation were associated positively with total cost of hospitalisation. Clinical Significance : No significant association was found between type of imaging and any patient outcome variables except cost of hospitalisation, which was higher for dogs having magnetic resonance imaging. Although magnetic resonance imaging may be considered advantageous compared to myelography because it is non-invasive and provides superior anatomical detail for surgical guidance, no beneficial effect on outcome of dogs with non-ambulatory thoracolumbar spinal disease was found.     

Magnetic resonance imaging findings and clinical associations in 52 dogs with suspected ischemic myelopathy

BACKGROUND: The magnetic resonance imaging (MRI) features of ischemic myelopathy have been described in the human literature and in a small number of cases in the veterinary literature. HYPOTHESIS: The aims of this study were to identify associations among MRI findings, timing of imaging, and presenting neurologic deficits in a large series of dogs with a presumptive diagnosis of ischemic myelopathy. ANIMALS AND METHODS: The medical records and MR images of dogs with a presumptive diagnosis of ischemic myelopathy (2000-2006) were reviewed retrospectively. Inclusion criteria were acute onset of nonprogressive and nonpainful myelopathy, 1.5-tesla MRI of the spine performed within 7 days of onset, and complete medical records and follow-up information. Presumptive diagnosis was based on history, as well as clinical, MRI, and cerebrospinal fluid (CSF) findings. The extent of the lesion on MRI was assessed as the following: (1) the ratio between the length of the hyperintense area on sagittal T2-weighted images and the length of C6 or L2 vertebral body, and (2) the maximal cross-sectional area of the hyperintense area on transverse T2-weighted images as a percentage of cross-sectional area of the spinal cord. RESULTS: Fifty-two dogs met the inclusion criteria. MRI findings were abnormal in 41 dogs and normal in 11 dogs. The presence of MRI abnormalities was not significantly associated with the timing of imaging (P = .3) but was associated with ambulatory status on presentation (P = .04). Severity of signs on presentation was associated with extent of the lesion on MRI (P = .02). CONCLUSION AND CLINICAL IMPORTANCE: The severity of signs on presentation is associated with the presence and the extent of the lesion on MRI.     

MAGNETIC RESONANCE IMAGING AND PATHOLOGIC FINDINGS ASSOCIATED WITH NECROTIZING ENCEPHALITIS IN TWO YORKSHIRE TERRIERS

Two young adult Yorkshire terriers had neurologic signs consistent with forebrain and brainstem involvement or forebrain involvement alone. On magnetic resonance imaging studies there were asymmetric bilateral lesions mainly in the cerebral cortex, and in the diencephalon. These areas were hyperintense on T2-weighted and FLAIR images, but hypointense or isointense on T1-weighted images. Lesions had a varying degree of contrast enhancement. Areas which were isointense on T1-weighted images had no contrast enhancement or only foci of contrast enhancement. Lesions with hypointensity in T1-weighted images had no enhancement or more frequently ring-like enhancement around the lesion. Necrotizing encephalitis was confirmed pathohistologically in both dogs. The degree of contrast enhancement appeared to be related to the degree of lymphohistiocytic inflammation on histologic examination.