IMAGING DIAGNOSIS—SPINAL EPIDURAL HEMANGIOSARCOMA IN A DOG

An 8‐year‐old, male Boxer was examined for an acute onset of ambulatory paraparesis. Neurologic examination was consistent with a T3‐L3 myelopathy. Myelography revealed an extradural spinal cord compression in the region of the T10‐T13 vertebrae. On magnetic resonance (MR) imaging, a well‐defined epidural mass lesion was detected. The mass was mildly hyperintense on T1‐weighted, hyperintense on T2‐weighted and STIR images compared to normal spinal cord and enhanced strongly and homogenously. Postmortem examination confirmed a primary epidural hemangiosarcoma. Findings indicated that the MRI characteristics of spinal epidural hemangiosarcoma may mimic other lesions including meningioma and epidural hemorrhages/hematomas of non‐neoplastic etiology.     

Conventional and functional magnetic resonance imaging features of late subacute cortical laminar necrosis in a dog

Cerebral cortical laminar necrosis (CLN) is a consequence of severe hypoxic, ischemic, or hypoglycemic events. In humans, these cortical lesions show characteristic linear T1‐weighted (T1W) hyperintensity in the late subacute stage. Limited information reporting magnetic resonance imaging (MRI) findings in dogs affected by CLN is available. A 3‐year‐old Belgian Shepherd dog was referred 8 days after sudden onset of blindness after general anesthesia. Neurological examination showed central blindness and mild ataxia. Three‐Tesla MRI examination of the brain revealed bilateral asymmetrical areas of T2‐weighted hyperintensity within the occipital, parietal, temporal, and frontal cortex, involving gray and white matter. Furthermore, linear T1W‐hyperintense lesions were found in the cerebral cortex of the same areas and showed heterogeneous contrast enhancement. Perfusion‐weighted images revealed hyperperfusion in the affected regions. Lesions were compatible with subacute CLN with corresponding edema suspected to be secondary to anesthesia‐related brain hypoxia. Three‐Tesla MRI enabled identification of the laminar pattern of the cortical lesions.     

Magnetic resonance imaging and pathological findings in a cat with brain contusions

Necropsy was performed on a mongrel male cat of unknown age weighing 1.3 kg, which probably encountered a traffic accident. Gross pathological examination of the brain revealed reddish colour of the right cerebral hemisphere and haemorrhages on the surface of the right frontal lobe to temporal lobe. Histologically, there was diffuse vacuolation in the cortex of the right frontal lobe and extensive haemorrhages in the base of brain. These histopathological findings were consistent with areas of abnormal signals found on post-mortem magnetic resonance imaging (MRI). In this study, the MRI findings were identical to that reported in human cases of head trauma as well as histopathological changes.     

Magnetic resonance imaging of two suspected cases of global brain ischemia

Objective: To describe the clinical findings and magnetic resonance imaging (MRI) characteristics of two animals with suspected global brain ischemia (GBI). Series summary: Two brachycephalic animals (Persian cat and Boston terrier) presented for altered mentation, blindness, ataxia, and seizures after being anesthetized. Common to both anesthetic protocols was ketamine. Clinically, the neurological deficits developed rapidly and did not progress after the initial 24 hours. MRI findings were most consistent with GBI. MRI, including pre‐ and post‐T1 weighted, T2 weighted, and fluid‐attenuated inversion recovery (FLAIR) studies, was used to image these animals. Abnormalities were seen post‐T1, T2, and FLAIR. Both animals improved neurologically with supportive care over several weeks, but both remained blind. New information: The use of MRI for diagnosing GBI.     

Canine insulinomas appear hyperintense on MRI T2‐weighted images and isointense on T1‐weighted images

Clinical and imaging diagnosis of canine insulinomas has proven difficult due to nonspecific clinical signs and the small size of these tumors. The aim of this retrospective case series study was to describe MRI findings in a group of dogs with pancreatic insulinomas. Included dogs were presented for suspected pancreatic insulinoma, MRI was used to assist with localization of the primary lesion, and the diagnosis was confirmed with surgical exploratory laparotomy and histopathology. The MRI studies for each dog were retrieved and the following data were recorded: T1‐weighted and T2‐weighted signal intensities, type of contrast enhancement, size and location of the primary lesion, and characteristics of metastatic lesions (if present). A total of four dogs were sampled. In all patients, the insulinoma displayed high‐intensity signal on T2‐weighted fat saturation images, similar to human studies. On postcontrast T1‐weighted fat saturation images, the tumors were primarily isointense to normal pancreatic tissue, in contrast to human studies where a low‐intensity signal is typically identified. Abnormal islet tissue was detected with MRI in all four dogs and metastases were identified in three dogs. Variations in the MRI appearance of primary and metastatic lesions were identified and could have been related to the variation of tissue composition, including the presence of neoplastic cells, hemorrhage, and fibrovascular stroma, and to the transformation of this tissue throughout the disease process.     

Magnetic resonance imaging of a brain abscess in a 10-month-old filly

The purpose of this paper was to correlate the magnetic resonance imaging (MRI) characteristics of a mature brain abscess in a horse with histopathologic alterations of brain tissue. Eight months after the onset of clinical signs, MRI of the brain of a 10-month-old filly was performed. A large space-occupying lesion in the right cerebral hemisphere was identified. This space-occupying lesion was delineated by a thick and well-defined capsule that was isointense to brain parenchyma on the T1-weighted images and with a markedly hypointense on the T2-weighted images. The identification of such a capsule is highly diagnostic of a mature brain abscess. The lesion seen on MR images was confirmed at necropsy where a large abscess of the right hemisphere was observed. Streptococcus zooepidemicus and Pseudomonas aeruginosa were isolated from the abscess. Based on histopathologic examination, the signal characteristics of the capsule on T1-weighted and T2-weighted images were found to be due to the presence of numerous hemosiderin-laden macrophages. These results are in agreement with previous studies on human patients. This report confirms the value of MRI in the diagnosis of equine brain diseases.     

MAGNETIC RESONANCE IMAGING FINDINGS IN 15 ACROMEGALIC CATS

Feline acromegaly is characterized by chronic excessive growth hormone secretion, most commonly caused by a functional pituitary adenoma. In this study, acromegaly was diagnosed in 15 cats on the basis of compatible clinical signs, laboratory, and magnetic resonance imaging (MRI) findings. MRI findings were reviewed retrospectively. Enlargement of the pituitary gland with suprasellar extension was present in all cats. No characteristic signal patterns were identified on T1‐weighted and T2‐weighted sequences. Contrast enhancement was nonuniform in all cats, as was suspected involvement of the adjacent hypothalamus. A mass effect on the cavernous sinus and third ventricle was present in 13 cats. Mild peritumoral edema was present in four cats, and moderate edema in one cat. Transtentorial herniation was present in one cat. Histopathology confirmed the presence of a pituitary adenoma in two cases. MRI is a useful modality to establish the diagnosis of acromegaly.     

Disseminated mast cell tumor infiltrating the sphenoid bone and causing blindness in a dog

Mast cell tumors are found in most organs and tissues with variable biologic behavior in dogs. This case illustrates the clinical and magnetic resonance imaging (MRI) findings in a dog with disseminated mast cell tumor infiltrating the sphenoid bones. A 6‐year‐old male neutered Greyhound presented with a 3‐day history of acute onset of blindness. General physical examination was normal. Neurological examination revealed mildly disorientated mental status, absent menace response in both eyes, bilaterally decreased vestibulo–oculocephalic reflexes and absent direct and consensual pupillary light reflex in both eyes. An electroretinogram indicated normal retinal function in both eyes. A lesion involving the middle and rostral cranial fossa was suspected. Hematology and serum biochemistry were normal except decreased urea (1.2 mmol/L). MRI of the head revealed heterogeneous signal intensity of the sphenoid bones on T2‐weighted images and loss of their normal internal architecture. Cerebrospinal fluid analysis was normal. Abdominal ultrasound revealed hepatosplenomegaly and mesenteric lymphadenopathy. Fine needle aspirates were taken from the jejunal lymph nodes and the spleen. Results were consistent with disseminated mast cell tumor. The owner declined any treatment and the dog was euthanatized. Postmortem examination confirmed disseminated mast cell tumor affecting multiple organs, including the sphenoid bones. To our knowledge, this is the first case describing MRI features of disseminated mast cell tumor affecting the sphenoid bones and causing acute onset of blindness in a dog.     

MRI characteristics of suspected acute spinal cord infarction in two cats, and a review of the literature

A 10-year-old neutered male Persian cat and a 4-year-old spayed female domestic shorthair (DSH) cat were evaluated for acute-onset severe lateralising tetraparesis and hemiplegia, respectively. Both cats also had left-sided Horner's syndrome. Neurological examination of the cats localised the lesion to cranial to C5 in the Persian and the left cervical intumescence (C6-T2) in the DSH. Physical examinations were otherwise generally unremarkable. Routine laboratory tests and spinal radiography were normal for the Persian cat and were not performed for the DSH cat. A cerebrospinal fluid (CSF) tap was attempted for the Persian cat but aborted because of gross blood contamination, and was not performed for the DSH cat. Magnetic resonance imaging (MRI) of the Persian cat revealed a lesion within the spinal parenchyma at segments C1 to C3 (slightly more left-sided) which was iso- to hypointense on T1-weighted scans and hyperintense on T2-weighted scans, and which enhanced slightly with gadolinium. MRI of the DSH cat revealed a lesion within the spinal parenchyma at segment C7 (predominantly left-sided) which was hypointense on T1-weighted scans and hyperintense on T2-weighted gradient echo scans. Contrast was not administered. The MRI findings in both cases were highly suggestive of acute spinal cord infarction, based upon comparison to human cases. Both cats made full neurological recoveries with supportive treatment only. This paper describes two cases of suspected acute spinal cord infarction in the cat, demonstrates the potential diagnostic value of MRI, and discusses the clinical syndrome of this condition with a brief review of published cases.     

Magnetic resonance imaging features of canine gliomatosis cerebri

A retrospective, case series study was undertaken to identify magnetic resonance imaging (MRI) characteristics of gliomatosis cerebri in dogs. Fourteen dogs were included by review of histopathological records and contemporaneous MRI. On MRI, all lesions presented as ill‐defined, intraaxial lesions within the left and right forebrain hemispheres with involvement of white and gray matter. Lesions presented as hyperintense areas on T2‐weighted and FLAIR sequences and as hypointense or isointense areas on T1‐weighted images, with mild parenchymal contrast enhancement in three dogs. Signal changes were noted in three to 10 cerebral lobes. Other most commonly affected structures were the thalamus (13), caudate nucleus (13), interthalamic adhesion (11), hypothalamus (11), callosal commissure (10), hippocampus (9), and quadrigeminal plate (8). Abnormalities within the caudal fossa were noted in 10 dogs. Solid tumor portions were identified in five dogs. The histopathological examination demonstrated in all dogs a widespread diffuse infiltration with neoplastic glial cells in white and gray matter with meningeal infiltration. Comparison between MRI and histopathology showed that all areas with signal changes on MRI corresponded to diffuse and dense infiltration with neoplastic cells. The signal intensity on T2‐weighted and FLAIR images reflected the density of neoplastic cells. In all dogs, MRI underestimated lesion extent and meningeal infiltration. Involvement of the caudal fossa was not seen on MRI in three dogs. Despite this, MRI allowed identification of lesions extending into at least three cerebral lobes and therefore satisfying the criteria used for diagnosis of diffuse glioma with gliomatosis cerebri growth pattern in humans.     

Ischemic Optic Neuropathy in a Dog with Acute Bilateral Blindness and Primary Systemic Hypertension

A 6‐year‐old neutered female Jack Russell terrier was investigated for sudden onset prechiasmatic bilateral blindness, left circling, reduced proprioception in the right pelvic limb and right facial allodynia. Electroretinography was normal. Magnetic resonance imaging (MRI) examination revealed that the right optic nerve and the optic chiasm were hyperintense on diffusion weighted imaging and hypointense on apparent diffusion coefficient map consistent with ischemic optic neuropathy. A concurrent lacunar infarct was detected in the left rostral colliculus. Primary systemic hypertension was diagnosed based on blood pressure measurement and no detectable abnormalities on hematology, comprehensive serum biochemistry, urinalysis including protein/creatinine and cortisol/creatinine ratios and thoracic/abdominal imaging. Prednisolone for 10 days and amlodipine long‐term were administered. Vision was not recovered after 7 months. Repeat MRI supported the diagnosis of ischemic lesions and revealed a recent striatocapsular infarct. Ischemic optic neuropathy is a well‐recognized cause of blindness in humans and should be included as a differential diagnosis for acute prechiasmatic blindness in dogs.     

Hypophysitis,Panhypopituitarism, and Hypothalamitis in a Scottish Terrier Dog

A 6‐year old male neutered Scottish Terrier was referred with a 1 week history of progressive lethargy and anorexia. Neurological examination localized a lesion to the forebrain and hormonal testing showed panhypopituitarism. Magnetic resonance imaging (MRI) of the brain revealed a rounded, well‐defined, suprasellar central mass. The mass was slightly hyperintense to the cortical grey matter on T2‐weighted (T2W), hypointense on T1‐weighted (T1W) images and without T2* signal void. There was a central fusiform enhancement of the mass after contrast administration which raised the suspicion of a pituitary neoplasm. Rapid deterioration of the dog prevented further clinical investigations. Histopathologic examination revealed a lymphocytic panhypophysitis of unknown origin suspected autoimmune involving the hypothalamus (hypothalamitis). This is a unique case report of a dog presenting with inflammatory hypophysitis and hypothalamitis of suspected autoimmune origin with detailed clinical, MRI, histology and immunohistochemistry findings.     

Ocular angiosarcoma in a pony ‐ MRI and histopathological appearance

Ocular angiosarcomas are an infrequent aetiology of exophthalmus in the horse. In the case presented here, a pony was referred with a history of supraorbital swelling, exophthalmus and conjunctivitis of the right eye. Radiographic and ultrasonographic examinations were used for diagnosis; however, the exact definition of the retrobulbar changes could only be made by magnetic resonance imaging (MRI). MRI shows anatomic and physiological detail in both the osseous and soft tissue structures. Only 3 sequences were used in this case: a transverse T2‐weighted and a dorsal high resolution, T1‐weighted gradient echo with multiplanar reconstruction capability pre‐ and post contrast application. This case report suggests that MRI should be used more frequently in the diagnosis of head tumours in horses.     

Rostral cerebellar arterial infarct in two cats

A 10-year-old female neutered domestic shorthair (DSH) cat and a 6-year-old female neutered Siamese cat were presented following a peracute onset of decerebellate rigidity and a cerebellar vestibular syndrome, respectively. In both cats, physical examination and routine blood tests were unremarkable, as was routine analysis of cerebrospinal fluid obtained from the DSH cat. Based on the magnetic resonance imaging (MRI) features - focal wedge-shaped lesion in the cerebellum characterised by hyperintensity in T2-weighted, T2( *)-gradient echo and fluid attenuated inversion recovery (FLAIR) images - a presumptive diagnosis of cerebellar infarct was made in both cases. In the DSH cat, the post-mortem examination confirmed the diagnosis of cerebellar infarct and additionally found acute renal infarcts and a pulmonary neoplasia. In the Siamese cat, ultrasonographic evaluation of the heart revealed a probable low-grade chronic valvular endocarditis which was thought to be a potential source of thromboembolism. This paper describes the first two cases - one confirmed and the other suspected - of cerebellar infarct in the cat. The in vivo potential diagnostic value of the MRI study is highlighted. Cerebellar infarcts should be included in the differential diagnosis of cat with a peracute onset of cerebellar signs regardless of the severity of neurological deficits.     

Susceptibility weighted imaging at 1.5 Tesla magnetic resonance imaging in dogs: Comparison with T2*‐weighted gradient echo sequence and its clinical indications

Susceptibility weighted imaging (SWI) is a high resolution, fully velocity‐compensated, three‐dimensional gradient echo (GE) MRI technique. In humans, SWI has been reported to be more sensitive than T2*‐weighted GE sequences in the identification of both intracranial hemorrhage and intra‐vascular deoxyhemoglobin. However, published clinical studies comparing SWI to T2*‐weighted GE sequences in dogs are currently lacking. The aim of this retrospective, observational study was to compare SWI and T2*‐weighted GE sequences in a group of dogs with intracranial disease. Medical records were searched for dogs that underwent a brain MRI examination that included T2*‐weighted GE and SWI sequences. The presence and appearance of non‐vascular and vascular signal voids observed on T2*‐weighted GE and SWI were compared. Thirty‐two dogs were included with the following diagnoses: presumed and confirmed intracranial neoplasia (27), cerebrovascular accidents (3), and trauma (2). Hemorrhagic lesions were significantly more conspicuous on SWI than T2*‐weighted GE sequences (P < .0001). Venous structures were well defined in all SWI sequences, and poorly defined in all dogs on T2*‐weighted GE. Susceptibility weighted imaging enabled identification of vascular abnormalities in 30 of 32 (93.8%) dogs, including: neovascularization in 19 of 32 (59.4%) dogs, displacement of perilesional veins in five of 32 (15.6%) dogs, and apparent dilation of perilesional veins in 10 of 32 (31.3%) dogs. Presence of neovascularization was significantly associated with T1‐weighted post‐contrast enhancement (P = .0184). Hemorrhagic lesions and venous structures were more conspicuous on SWI compared to T2*‐weighted GE sequences. Authors recommend adding SWI to standard brain protocols in dogs for detecting hemorrhage and identifying venous abnormalities for lesion characterization.     

Intracranial extension of retrobulbar blastomycosis (Blastomyces dermatitidis) in a dog

Blastomycosis (Blastomyces dermatitidis) is a fungal disease that is endemic in the southern United States. This case report illustrates the clinical, MRI and histopathologic findings in a dog with invasion of a retrobulbar blastomycotic lesion into the calvarium. A 5‐year‐old intact female Weimaraner was referred for a 2‐month history of change in behavior and recent onset of visual deficits. Magnetic resonance imaging (MRI) examination revealed a large (5.8 × 2.0 × 2.5 cm) mass extending from the left orbit through a circular defect in the left cranioventral aspect of the calvarium caudally to the level of the pituitary fossa and interthalamic adhesion. The mass was heterogeneously iso‐ to hypointense on T2‐W images, slightly hypointense on T1‐W images, did not attenuate on fluid attenuated inversion recovery (FLAIR) images, and did not show evidence of susceptibility artifact on T2*‐W gradient recalled echo (GRE) images. Vasogenic edema and associated mass effect were noted. The mass showed strong homogeneous contrast enhancement with well‐defined margins and had thickening of the adjacent meninges (dural tail sign). Based on MRI findings a malignant neoplastic process was considered most likely and the patient was placed on oral prednisone to decrease peri‐tumoral inflammation. The dog initially improved but was euthanized 3 weeks later for worsening clinical signs. Histopathologic assessment of the mass revealed marked pyogranulomatous optic neuritis with intralesional fungal yeasts consistent with blastomycosis (Blastomyces dermatitidis). To our knowledge this is the first report of invasion of a retrobulbar blastomycotic lesion into the calvarium in a dog.     

Adenocarcinoma metastasis of the intertransversarius cervicis muscle eliciting a right forelimb lameness in a dog

This article describes identification of a metastatic adenocarcinoma to the intertransversarius cervicis muscle using magnetic resonance imaging (MRI) in a dog that presented with chronic lameness of the right forelimb. Magnetic resonance imaging revealed a right sided, ovoid signal abnormality within the intertransversarius cervicis muscle lateral to the sixth cervical (C6) vertebra. The lesion was uniform, hyperintense on T2- and isointense on T1-weighted images to muscle and exhibited uniform contrast enhancement on T1-weighted images. The MRI findings were consistent with a neoplasia. Surgical excision was performed. Histopathological diagnosis was metastatic fibrous adenocarcinoma. The dog recovered rapidly but 6 months post-operatively he was killed because of lung metastases. Necropsy was declined and the primary tumour could not be identified.     

Three‐dimensional T1‐weighted gradient echo is a suitable alternative to two‐dimensional T1‐weighted spin echo for imaging the canine brain

Volumetric imaging (VOL), a three‐dimensional magnetic resonance imaging (MRI) technique, has been described in the literature for evaluation of the human brain. It offers several advantages over conventional two‐dimensional (2D) spin echo (SE), allowing rapid, whole‐brain, isotropic imaging with submillimeter voxels. This retrospective, observational study compares the use of 2D T1‐weighted SE (T1W SE), with T1W VOL, for the evaluation of dogs with clinical signs of intracranial disease. Brain MRI images from 160 dogs who had T1W SE and T1W VOL sequences acquired pre‐ and postcontrast, were reviewed for presence and characteristics of intracranial lesions. Twenty‐nine of 160 patients were found to have intracranial lesions, all visible on both sequences. Significantly better grey‐white matter (GWM) differentiation was identified with T1W VOL (P < .001), with fair agreement between the two sequences (weighted κ = 0.35). Excluding a mild reduction in lesion intensity in three dogs precontrast on the T1W VOL images compared to T1W SE, and meningeal enhancement noted on the T1W VOL images in one dog, not identified on T1W SE, there was otherwise complete agreement between the two sequences. The T1W VOL sequence provided equivalent lesion evaluation and significantly improved GWM differentiation. Images acquired were of comparable diagnostic quality to those produced using a conventional T1W SE technique, for assessment of lesion appearance, number, location, mass effect, and postcontrast enhancement. T1W VOL, therefore, provides a suitable alternative T1W sequence for canine brain evaluation and can facilitate a reduction in total image acquisition time.