Page 1101 - Small Animal Internal Medicine, 6th Edition

CHAPTER 59 Diagnostic Tests for Nervous System and Neuromuscular Disorders 1073

BIOPSY OF MUSCLE AND NERVE NERVE BIOPSY
It may be useful to obtain nerve biopsy specimens in an
VetBooks.ir Muscle biopsy specimens should be evaluated when there is effort to evaluate peripheral nerve disorders. Nerves are
MUSCLE BIOPSY
biopsied by transecting approximately one third of the
clinical and electrophysiologic evidence of muscular disease.
length, leaving most of the nerve trunk intact. It is impor-
A biopsy may provide a definitive diagnosis or indicate the width of the nerve and removing fascicles about 1 cm in
nature of the disease process. For best results, muscle that tant to biopsy nerves that are affected. The common pero-
is affected should be biopsied, and in generalized disorders neal nerve and the ulnar nerve are the mixed (i.e., motor
two different muscles should be sampled. For investigation and sensory) nerves most commonly biopsied. As with
of myopathic disorders, proximal limb muscles such as the muscle biopsy specimens, nerve biopsy specimens require
vastus lateralis or triceps should be biopsied, whereas neu- special handling to ensure that maximal information is
ropathies are more evident in distal limb muscles such as obtained. Samples should be laid out on a piece of wooden
the cranial tibial or extensor carpi radialis. Because complete tongue depressor and pinned at each end to keep them
histopathologic examination of muscle requires fresh-frozen oriented longitudinally, but they should not be stretched.
tissue, most laboratories request that fresh muscle samples They should then be fixed in 2.5% glutaraldehyde or buff-
be wrapped in a saline-moistened gauze and shipped over- ered 10% formalin for light microscopy. Fresh nerve
night under refrigeration. Whenever formalin-fixed samples samples can be frozen in liquid nitrogen and stored for
are submitted, the sample should be attached to a splint, biochemical analysis.
such as a tongue depressor, to prevent contraction during
fixation. Routine histologic studies may reveal inflammatory
or neoplastic changes and the etiologic agent if the disease Suggested Readings
is infectious. Bohn A, et al. Cerebrospinal fluid analysis and magnetic resonance
When fresh-frozen tissue is evaluated using a full range imaging in the diagnosis of neurologic diseases in dogs: a retro-
of enzymatic and immunohistochemical techniques, many spective study. Vet Clin Pathol. 2006;35:315.
characteristics of the muscle can be determined. Based on da Costa RC, Samii VF. Advanced imaging of the spine in small
animals. Vet Clin North Am Small Anim Pract. 2010;40:765.
enzymatic staining characteristics, muscle fibers can be clas- Dickinson PJ, LeCouter RA. Muscle and nerve biopsy. Vet Clin
sified according to type and the proportion and distribution North Am Small Anim Pract. 2002;32:63.
of myofiber types described. Some myopathies result in a Fry MM, Vernau W, Kass PH. Effects of time, initial composition
selective loss of one fiber type. Denervation with reinnerva- and stabilizing agents on the results of canine cerebrospinal fluid
tion, as occurs in many neuropathies, results in “type group- analysis. Vet Clin Pathol. 2006;35:72.
ing,” wherein the normal checkerboard pattern disappears Hecht S, Adams WH. MRI of brain disease in veterinary patients:
and large clusters of fibers of the same type appear. Muscle part 1: basic principles and congenital brain disorders. Vet Clin
fiber shape and size, the presence of degeneration or necro- North Am Small Anim Pract. 2010;40:21.
sis, the location of nuclei, the presence of vacuoles or inclu- Olby NJ, Thrall DE. Neuroimaging. In: Platt SR, Olby NJ, eds.
sions, and the presence of cellular infiltrates are all evaluated. BSAVA manual of canine and feline neurology. 4th ed. Gloucester:
Immunostains are also available to identify some parasites BSAVA; 2013.
(Neospora) and evaluate muscles for normal structural com- Sharp NJH, Wheeler SJ. Diagnostic aids. In: Sharp NJH, Wheeler
ponents. Muscle samples should be sent to a laboratory with SJ, eds. Small animal spinal disorders: diagnosis and surgery. 2nd
ed. St Louis: Mosby; 2005.
a special interest and expertise in muscle disorders to ensure Taylor SM. Cerebrospinal fluid collection. In: Taylor SM, eds. Small
that optimal results are obtained and accurately interpreted. animal clinical techniques. 2nd ed. Philadelphia: Elsevier;
Clinicians should consult the laboratory that will process the 2016.
biopsy to learn the proper technique of obtaining, preparing, Wamsley H, Alleman AR. Clinical pathology. In: Platt SR, Olby NJ,
and submitting specimens and the other procedures to be eds. BSAVA manual of canine and feline neurology. Gloucester:
followed. BSAVA; 2004.