M. P. Targett

Neurological signs and results of magnetic resonance imaging in 40 cavalier King Charles spaniels with Chiari type 1-like malformations

In human beings a Chiari type 1 malformation is a developmental condition characterised by cerebellar herniation and syringohydromyelia. Abnormalities compatible with such a malformation were identified by magnetic resonance imaging in 39 cavalier King Charles spaniels with neurological signs and in one neurologically normal cavalier King Charles spaniel that was examined postmortem. The dogs with these abnormalities had a wide variety of neurological signs, but there was no apparent correlation between the neurological signs and the severity of cerebellar herniation, syringohydromyelia or hydrocephalus.

Failure to achieve remyelination of demyelinated rat axons following transplantation of glial cells obtained from the adult human brain

The ability of transplanted glial cells to myelinate axons in experimental animals offers the prospect that it may be possible to achieve remyelination in human demyelinating disease by the implantation of oligodendrocyte lineage cells. Autologous normal white matter could represent a potential source of cells whose use would avoid tissue rejection and overcome ethical and practical constraints associated with the use of fetal tissue. To determine the remyelinating potential of cells isolated from adult human CNS, a cell preparation prepared from adult human white matter which contained 56% oligodendrocytes, 3% preoligodendrocytes and 1% precursor cells was transplanted into non-repairing demyelinating lesions in immunosuppressed rats created by the injection of ethidium bromide into x-irradiated spinal cord white matter. The extent of remyelination was examined 3 and 5 weeks after transplantation. Although the transplanted oligodendrocytes survived in the area of demyelination, associated with demyelinated axons and produced myelin membranes, no myelin sheaths were produced and there was no evidence of cell migration or division. The failure of human oligodendrocytes to form myelin sheaths may reflect the poor remyelinating potential of post mitotic oligodendrocytes, and the failure of the small number of co-transplanted bipotential oligodendrocyte progenitor cells to differentiate and myelinate axons may be a consequence of lack of appropriate environmental factors within the rat lesion required for expansion and differentiation of these cells.

MRI features of CNS lymphoma in dogs and cats.

The magnetic resonance (MR) imaging features of central nervous system lymphoma in eight dogs and four cats are described. Intracranial lesions affected the rostrotentorial structures in six dogs and caudotentorial structures in two cats. Lesions affected the spinal cord in two dogs and in two cats. One dog and one cat with intracranial lymphoma had signs of local extracranial extension and lymphadenopathy. Lesions were considered extraparenchymal in four dogs and three cats, intraparenchymal in two dogs and one cat, and appeared to have both intra- and extraparenchymal components in two dogs. All lesions were hyperintense in T2-weighted images when compared to white matter, most were hypointense in T1-weighted images (7/12), and most were hyperintense in fluid-attenuated inversion recovery (FLAIR) images (5/9). When compared to grey matter, these lesions appear either isointense (5/12) or hyperintense (7/12) on T2-weighted images, half of them were hypointense in T1-weighted images (6/12), and most were isointense in FLAIR images (7/9). Lesion margins were usually indistinct in T2-weighted images (10/12) and had perilesional hyperintensity in FLAIR images (7/9). The majority of lesions (10/12) had abnormal meninges around the lesion and half (6/12) had generalized contrast enhancement. Mass effect was evident in all lesions. Although not specific, when combined with the history and neurologic signs, MR features aid presumptive diagnosis that should be confirmed by cytology or histopathology.

Acute intervertebral disc extrusion in a cat: clinical and MRI findings

A 5 year old, neutered male, domestic shorthaired cat had acute left hemiparesis and Horners syndrome. Magnetic resonance imaging (MRI) revealed a loss of the normal signal from the nucleus pulposus of the intervertebral disc at C3/4, narrowing of the ventral subarachnoid space and slight dorsal displacement of the spinal cord and a focal hyperintense lesion affecting the left side of the spinal cord at the same level. The presumptive diagnosis was focal spinal cord oedema associated with intervertebral disc extrusion. A traumatic aetiology was suspected. The cat was treated conservatively and improved gradually over a period of 6 months.

MRI findings in a dog with otitis media and suspected otitis interna

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The use of xenografting to evaluate the remyelinating potential of glial cell cultures.

Experiments in rodents have shown a potential role for glial cell transplantation as a means of influencing repair in the central nervous system of man. A crucial step in developing human therapy is to establish whether knowledge gained from studies in rodents is applicable to larger mammalian species. In order to explore this issue we examined the ability of cat glial cell cultures to remyel-inate areas of ethidium-bromide-induced demyelination in the spinal cord of immunosuppressed rats and cats. Transplantation of density-gradient-isolated glial cells obtained from the forebrain of 7-day-old kittens resulted in enhanced oligodendrocyte remyelination in the rat but failed to enhance oligodendrocyte remyelination in the cat. The feasibility of enhancing oligodendrocyte remyelination in the cat lesion was demonstrated by transplanting a rat culture containing a high proportion of cells of the oligodendrocyte lineage. Tissue culture of the density-gradient-isolated cell preparations suggested that the failure of the kitten glial preparation to enhance oligodendrocyte remyelination in the cat was most probably due to its poor oligodendrocyte-generating capacity. However, our lack of understanding of the biology of feline glial cells precludes a full understanding of these experiments.

STIR muscle hyperintensity in the cervical muscles associated with inflammatory spinal cord disease of unknown origin.

OBJECTIVES To assess the relation of a distinctive pattern of short tau inversion recovery muscle hyperintensity with inflammatory cerebrospinal fluid result in dogs. METHODS All dogs that had a short tau inversion recovery sequence performed in addition to other magnetic resonance sequences of the cervical spine and concurrent cerebrospinal fluid evaluation during the study period were included. All magnetic resonance studies were anonymised and reviewed by a board certified radiologist and board certified neurologist. A board certified pathologist examined the cerebrospinal fluid and the results were reviewed. RESULTS Forty-nine cases fulfilled the inclusion criteria. Repeatable patterns of short tau inversion recovery hyperintensity were identified in 20 dogs. The clinical diagnosis in all these 20 cases was of meningoencephalomyelitis of unknown origin. This diagnosis was confirmed by inflammatory cerebrospinal fluid changes in 18 and suspected from clinical presentation and response to therapy in the remaining 2. CLINICAL SIGNIFICANCE In this study, the short tau inversion recovery changes identified were restricted to cases with inflammatory spinal cord disease. The short tau inversion recovery change had a sensitivity of 78%, and a specificity of 92% in predicting inflammatory cerebrospinal fluid, suggesting that short tau inversion recovery sequences are a useful addition to the investigation of suspected inflammatory spinal cord disease.

Haemophilia A (factor VIII deficiency) in a litter of Weimaraners

Inherited coagulopathies are reported in a number of dog breeds. However, to date, there is no report of Weimaraners suffering factor VIII deficiency (haemophilia A). We report the discovery of haemophilia A in both males from a single litter of Weimaraners. Haemophilia A in human beings often results from a de novo stochastic mutation. We found no evidence using currently available screening tests of haemophilia A in relatives as far back as three generations making a stochastic mutation possible in this litter.

Long-term outcome following lateral foraminotomy as treatment for canine degenerative lumbosacral stenosis

Lateral foraminotomy has been described as an effective surgical treatment for foraminal stenosis in the treatment of degenerative lumbosacral stenosis (DLSS) in dogs. Clinical records were reviewed from 45 dogs which had undergone lateral foraminotomy at the lumbosacral junction either alone or in combination with decompressive midline dorsal laminectomy. Short-term outcome at six weeks was assessed by the surgeon to be good (11.1 per cent) or excellent (88.9 per cent) in all 45 cases. Long-term outcome beyond six months for lumbosacral syndrome was assessed by the owner as excellent in all 34 cases for which follow-up was available despite recurrence in five cases. Recurrence of clinical signs was not related to re-establishment of foraminal compression at the surgical site when assessed on repeat MRI and was managed by either contralateral foraminotomy in one case or conservative management with excellent response. This study confirms lateral foraminotomy as an effective procedure in the management of DLSS-affected dogs suffering from foraminal stenosis and demonstrates that initial good short-term results are maintained long term despite some treatable recurrences. Lateral foraminotomy is an effective procedure when used appropriately in DLSS with foraminal stenosis either alone or in combination with midline dorsal laminectomy.

Gainfully employing descending controls in acute and chronic pain management

Specific primary afferent fibres termed nociceptors are responsible for transmitting nociceptive information. Centrally the axonal terminals of these fibres synapse with secondary projection neurones in the spinal dorsal horn to transmit nociceptive information to the higher centres in the brain. Irrespective of the presence or absence of nociceptive inflow the activity of dorsal horn neurones is modulated by, amongst other things, local interneurones and descending midbrain and brainstem networks which can inhibit or facilitate dorsal horn transmission. These pathways therefore set the threshold for information inflow to the CNS. This review article summarises the anatomy, physiology and pharmacology particularly of these descending inhibitory and facilitatory pathways and explains why the study of descending modulation is essential if we are to develop more efficacious interventions for treating pain and relieving suffering.