Large Animal Neurology. Joe Mayhew

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Figure 3.1 In the appropriate clinical setting, red to brown discoloration to urine normally indicates the presence of globin pigments that is positive for same on a dip stick assay and is an excellent ancillary aid to diagnosis. Myoglobinuria is seen in these urine samples from a horse recovering from acute rhabdomyolysis. The acute sample taken is on the left through to the sample taken after recovery on the right. Although myoglobin is usually brown and hemoglobinuria is usually red, as seen here there can be poor distinction based on color alone.

      Selection of neuromuscular genetic tests that are available

      Selection of Large Animal Veterinary Genetic Testing Laboratories (URLs logged March 2022)

Cerebrospinal fluid analysis

The routine collection procedures for cerebrospinal fluid (CSF) sampling from large animals (Figure 3.2) have been described and simplified,^7–12 and techniques for the analysis of CSF samples have also been published.^12–19 Techniques for CSF collection from the horse are shown in Figures 3.3, 3.4, and 3.5, and those described for other large animals (Figure 3.6) can be extrapolated directly from the horse and from ruminants.^20–22 Ultrasound‐guided collection of CSF can also be considered,^23,24 and such ultrasound‐guided techniques for the collection of fluid from the atlantooccipital (Figure 3.7) and atlantoaxial spaces (Figure 3.8) in standing, adult horses can be useful in certain circumstances.^20–22,25 These are safe procedures using effective chemical restraint, although the possibility of inadvertent movement resulting in spinal cord penetration is always of concern. It is likely that worrisome signs of somnolence, stiff neck, and fever that resolves in a day or so following the cervical centesis occurs in a few cases. In neonatal foals, calves, camelids, and piglets, as well as sheep and goats, it is advantageous to use a 40–50 mm (1.5–2 inches), 20 ga disposable hypodermic needle with a plastic hub for all atlantooccipital CSF collections. These needles are exceedingly atraumatic, and in obtunded and in lightly sedated recumbent patients they cause minimal or no patient reaction. More importantly, CSF appears in the hub of the needle immediately after it enters the subarachnoid space. A sample can be obtained, and the needle withdrawn much more rapidly than if a styletted needle is used—very important in nonanesthetized patients. Indeed, during CSF collection from the cisterna magna of anesthetized dogs, it was shown that a stylet‐out technique was performed more rapidly and yielded a sample with less cellular debris than a stylet‐in technique using a standard CSF styletted needle.²⁶

Figure 3.2 Multiple tests were performed on this patient suspected of having a neuromuscular disorder. These included lumbosacral cerebrospinal fluid collection (1), needle electromyography (2), and muscle biopsies of type I and type II muscle‐fiber‐predominant muscles taken from sacrocaudalis dorsalis medialis and semitendinosus muscles at sites (indicated by 3 and 4), respectively.

Figure 3.3 Atlantooccipital cerebrospinal fluid collection from the recumbent horse. Spinal needle in position with stilette removed. Palpable landmarks are the cranial borders of the atlas (filled circles) and the external occipital protuberance (cross) on the dorsal midline.

      (Source: From Mayhew¹¹ with permission.

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