MRI of secondary cervical syringomyelia in four cats

Low-field magnetic resonance imaging and computed tomography of a calf with aqueductal stenosis caused by web: comparison with normal calves

A 6-day-old female Holstein displayed a dome-shaped skull and cardiac murmur on physical examination. Neurological abnormalities included progressive ataxia, decreased pupillary light reflex, and blindness soon after birth. On diagnostic imaging, CT identified expanded ventricles and thyroid hypoplasia on the left side. MRI detected expanded ventricles, especially in the rostral cerebrum at the mesencephalic aqueduct, compared with normal calves, so we suspected hydrocephalus causing stenosis of the mesencephalic aqueduct. Postmortem examination revealed a structure in the mesencephalic aqueduct resembling the “web” type of aqueductal stenosis described in humans. This case report indicates the utility of describing mesencephalic aqueductal stenosis by web and detection of other malformations on CT and MRI for antemortem diagnosis in calves.

Shape of the feline cerebellum and occipital bone related to breed on MRI of 200 cats

Objectives The MRI features of the feline cerebellum and occipital bone have not previously been described in the literature. The aims of this study were three-fold. Firstly, to document variations in cerebellar shape on MRI in neurologically normal cats to support our hypothesis that crowding of the contents of the caudal fossa or herniation of the cerebellar vermis through the foramen magnum occurs frequently as an anatomical variant. Secondly, to document variations in the morphology of the occipital bone. Thirdly, to see whether these variations in shape of the feline cerebellum and occipital bone could be associated with head conformation, such as brachycephaly. Methods The imaging records of the small animal clinic at the Animal Health Trust between 2000 and 2013 were searched retrospectively to identify adult cats that had undergone high-field (1.5 T) MRI investigation which included the brain. Exclusion criteria included evidence of intracranial disease or the presence of cervical syringomyelia. Midline sagittal T2-weighted and transverse images were used to assess the occipital bone morphology and cerebellar shape, and to measure the width to length ratio of the cranial cavity. Results Fourteen different breeds were represented. A cerebellar shape consistent with crowding of the contents of the caudal fossa, or herniation through the foramen magnum was present in 40% of the entire population. Persians (recognised as a brachycephalic breed) had a higher proportion of cerebellar crowding or herniation than all other breeds. There was no significant difference in the distribution of occipital bone morphology between these breed groups. Conclusions and relevance It is important to recognise morphological variations of the feline cerebellum and occipital bone in order to avoid false-positive diagnoses of raised intracranial pressure and pathological herniation on MRI.

Quantification of cerebral lateral ventricular volume in cats by low- and high-field MRI

Objectives The aim of this study was to evaluate variations in lateral ventricles in the examined feline population with the use of quantitative analysis methods to determine whether sex or body weight influenced the size of the ventricles, and to identify any significant differences in the results of low- and high-field MRI. Methods Twenty healthy European Shorthair cats, aged 1-3 years, with body weights ranging from 2.85-4.35 kg, were studied. MRI of brain structures was performed in a low- and a high-field MRI system. The height of the brain and lateral ventricles at the level of the interthalamic adhesion, and volume of the lateral ventricles were determined in T2-weighted images in the transverse plane. The degree of symmetry of lateral ventricles was analysed based on the ratio of right to left ventricular volume. The measured parameters were processed statistically to determine whether sex and body weight were significantly correlated with variations in ventricular anatomy. The results of low- and high-field MRI were analysed to evaluate for any significant differences. Results The average brain height was determined to be 27.79 mm, and the average height of the left and right ventricles were 2.98 mm and 2.89 mm, respectively. The average ventricle/brain height ratio was 10.61%. The average volume of the left ventricle was 134.12 mm3 and the right ventricle was 130.49 mm3. Moderately enlarged ventricles were observed in two cats. Moderate ventricular asymmetry was described in four cats. Sex and body weight had no significant effect on the evaluated parameters. The differences in the results of low- and high-field MRI were not statistically significant. Conclusions and relevance This study has determined reference intervals for ventricular volume in a population of European Shorthair cats without brain disease, which will facilitate the interpretation of MRI images and the characterisation of brain abnormalities in cats with neurological disease. Further research involving larger animal populations, including other breeds, is required to compare the measured parameters between breeds and to determine reference values for other breeds.

Clinicopathologic Features and Magnetic Resonance Imaging Findings in 24 Cats With Histopathologically Confirmed Neurologic Feline Infectious Peritonitis

BACKGROUND

Feline infectious peritonitis (FIP) is the most common infectious central nervous system (CNS) disease in the cat and is invariably fatal. Improved means of antemortem diagnosis is required to facilitate clinical decision making. Information regarding the magnetic resonance imaging (MRI) findings of neurologic FIP currently is limited, resulting in the need for better descriptions to optimize its use as a diagnostic tool.

OBJECTIVE

To describe the clinicopathologic features and MRI findings in cases of confirmed neurologic FIP.

ANIMALS

Twenty-four client-owned cats with histopathologic confirmation of neurologic FIP.

METHODS

Archived records from 5 institutions were retrospectively reviewed to identify cases with confirmed neurologic FIP that had undergone antemortem MRI of the CNS. Signalment, clinicopathologic, MRI, and histopathologic findings were evaluated.

RESULTS

Three distinct clinical syndromes were identified: T3-L3 myelopathy (3), central vestibular syndrome (7), and multifocal CNS disease (14). Magnetic resonance imaging abnormalities were detected in all cases, including meningeal contrast enhancement (22), ependymal contrast enhancement (20), ventriculomegaly (20), syringomyelia (17), and foramen magnum herniation (14). Cerebrospinal fluid was analysed in 11 cases; all demonstrated a marked increase in total protein concentration and total nucleated cell count. All 24 cats were euthanized with a median survival time of 14 days (range, 2-115) from onset of clinical signs. Histopathologic analysis identified perivascular pyogranulomatous infiltrates, lymphoplasmacytic infiltrates, or both affecting the leptomeninges (16), choroid plexuses (16), and periventricular parenchyma (13).

CONCLUSIONS AND CLINICAL IMPORTANCE

Magnetic resonance imaging is a sensitive means of detecting neurologic FIP, particularly in combination with a compatible signalment, clinical presentation, and CSF analysis.

Amelioration of caudal thoracic syringohydromyelia following surgical management of an adjacent arachnoid cyst

A nine-year-old male, neutered, pug was presented for investigation of progressive ambulatory paraparesis and pelvic limb ataxia of three months' duration. Magnetic resonance imaging was suggestive of caudal thoracic syringohydromyelia with an adjacent intradural arachnoid cyst. The cyst was marsupialised following dorsal laminectomy. Neurological status had improved 10 weeks following surgery when repeat magnetic resonance imaging revealed reduced spinal cord compression both as a result of resolution of the cyst and reduction in size of the syringohydromyelia. At 17 months following surgery, the dog showed further improvements in neurological status, exhibiting mild pelvic limb ataxia and proprioceptive deficits. Improved cerebrospinal fluid flow following surgery may have played a role in the improvement in both conditions. The presence of syringohydromyelia in this context does not preclude a favourable clinical outcome following surgical management.

Feline spinal cord diseases

The objective of this article is to review the recent literature that reports on the most common diseases affecting the spinal cord of cats, and to draw some general conclusions that will be useful to formulate diagnosis and prognosis for feline spinal patients. The most common types of feline spinal cord diseases documented were inflammatory/infectious diseases, and feline infectious peritonitis was the most common disease, representing approximately 50% of all feline myelitis. Neoplasms were documented in approximately 25% of cases; lymphosarcoma was the most common tumor affecting the spinal cord of cats, with reported prevalence between 28% and 40%. Cats diagnosed with spinal lymphosarcoma were significantly younger (median age 4 years) than cats with other spinal cord tumors (median age 10 years). Cats with clinical signs of intervertebral disc disease had a median age of 8 years, and 67% had Hansen type I disc protrusions. The most commonly affected intervertebral disc was at the L4 to L5 intervertebral disc space. Fibrocartilaginous embolism-affected older cats (median age 10 years), seemed to predominate in the cervicothoracic intumescence, and clinical signs were markedly lateralized, especially when the cervical region was affected.