The most common muscles biopsies for small animals are the triceps, quadriceps, and cranial tibial muscles, and the common peroneal nerve, if needed. For horses, the semimembranous/tendinosus muscles, gluteal, and sacrocaudalis muscles are often the most accessible. Detailed instructions on how to collect and package a muscle biopsy are found here[pdflink].|
The muscle biopsy should be obtained from a muscle that is definitely affected but not so severely wasted that much of it is replaced by fatty or fibrous tissue. Ideally, the muscle should be one that has not been traumatized by injections or EMG studies. For suspected masticatory myositis cases (MMM), the temporalis is typically biopsied (be sure to retract the more superficial caudoauricular muscle prior to excising the sample). Often, MMM can be diagnosed by detection of antibodies in the serum alone, without submitting a muscle biopsy.
A specimen approximately 1 cm long, by 0.5 cm wide and 0.5 cm deep should be removed with minimal trauma (no cautery, please). It should be dissected along the long axis of the muscle, as myofiber orientation is crucial in obtaining diagnostic sections. Immediately after removal, the sample should be rolled up in a saline moistened (not dripping wet) gauze sponge. Place the sample and sponge into a suitable container (i.e. small specimen jar or petri dish) and keep it cold on crushed ice, ice packs, or in a refrigerator.
What is the difference between a fresh vs. formalin fixed muscle biopsy?
One is not ‘better’ than the other they just evaluate different features of muscle pathology. The chemical formalin essentially kills the muscle and is best only for structural and anatomical evaluation. Fresh muscle is enzymatically ‘alive’, and our histochemical techniques show this activity, whether normal or abnormal. The advantage of fresh, frozen muscle histochemistry is that we can assess both the structure and the various enzymatic functions of the myofibers. The routine histochemical staining panel at the NDL includes 14 different staining techniques for each muscle, compared to just one routine stain for formalin-fixed muscle.
I have only formalin fixed muscle. Where can I send it for interpretation?
The NDL only processes fresh muscle tissue, we cannot process fixed tissue. Options for interpretation of formalin fixed muscle include any commercial lab (IDEXX, etc.), or the UC Davis VMTH Anatomic Pathology service.
How & when do I ship a fresh muscle biopsy?
Because a fresh muscle biopsy is essentially a living tissue, appropriate packaging and rapid transport to the laboratory is imperative to permit adequate processing of the sample. Plan the timing of collection of your sample appropriately.
UNITED STATES
For shipment, securely sandwich the container between cold packs in a Styrofoam box, along with the NDL Biopsy Request form. Label the package refrigerate upon arrival and ship the same day by priority overnight Monday-Thursday (no Fridays, please). All histochemical and immunocytochemical studies are performed on fresh tissue.
INTERNATIONAL
Equine
Contact the lab prior to shipment, so we can expect the package, AND you must request the USDA permit for importation and transportation of controlled materials and organisms and vectors (total of 2 pages). We will fax or email you the permit, and it MUST accompany your shipment or it will be held at Customs.
For tissue that will not arrive within 24 hours or less, follow the guidelines for removal of the biopsy from the patient. Instead of wrapping the sample in saline moistened gauze, place it directly on a piece of aluminum foil. Fold the foil around the tissue and secure the edges (by rolling them tightly). If possible, freeze the sample packet in liquid nitrogen, then ship on dry ice; if liquid nitrogen is not available, the sample can just be shipped on dry ice. Place this in the middle of a medium to large styrofoam box filled with dry ice (minimum 3-4 kg). The dry ice should be in thick slabs, do not use pellets, as they sublimate too rapidly. Position the sample such that it is surrounded by dry ice on all sides, including the top but try not to crush the sample. Include the patient information, as well as the NDL Biopsy Request form, with the sample. Ship as quickly as possible! Make sure it is set to arrive on a weekday. Notify the lab so we can be on the lookout for your shipment and let you know if there is a problem.
All other animals
For tissue that will not arrive within 24 hours or less, follow the guidelines for removal of the biopsy from the patient. Instead of wrapping the sample in saline moistened gauze, place it directly on a piece of aluminum foil. Fold the foil around the tissue and secure the edges (by rolling them tightly). If possible, rapidly freeze the sample in the foil packet in liquid nitrogen, then ship on dry ice; if liquid nitrogen is not available, the sample can just be shipped on dry ice. Place this in the middle of a medium to large styrofoam box filled with dry ice (minimum 3-4 kg). The dry ice should be in thick slabs, do not use pellets, as they sublimate too rapidly. Position the sample such that it is surrounded by dry ice on all sides, including the top but try not to crush the sample. Include the patient information, as well as the NDL Biopsy Request form, with the sample. Ship as quickly as possible! Make sure it is set to arrive on a weekday. Notify the lab so we can be on the lookout for your shipment and let you know if there is a problem.
How long until I receive my results?
Because the processing and staining of fresh muscle is more time consuming than fixed muscle, it may take up to 2 weeks to receive a report. The report will be faxed or emailed to you as soon as completed. All human and small animal samples are interpreted by Dr. Marguerite Knipe and equine samples are interpreted by Dr. Monica Aleman, our large animal neurologist.
I am a researcher interested in fresh muscle processing for a research project. Will the NDL process outside research samples?
Yes – we have research rates for projects, and we are happy to discuss your goals for your samples. Based on your research questions, a limited staining panel may be appropriate, and you may choose to have the slides returned to you for your own data collection. Please contact us for more information.
I’m not sure if my patient has neuromuscular disease or if I need to do a muscle/nerve biopsy. How can I find out if this is the next best diagnostic step?
One of the advantages of the NDL is that it is part of the Neurology/Neurosurgery Service at UC Davis, so you can contact clinical neurologists for consultation and even referral for assessment for neuromuscular disease, including electrodiagnostics and biopsies.
Some clinical signs that can be associated with neuromuscular diseaseinclude:
Exercise intolerance (hallmark sign)
Generalized weakness (hallmark sign)
Focal or generalized muscle atrophy/hypertrophy
Gait abnormalities and/or lameness
Megaesophagus/regurgitation/dysphagia
Stridor/roaring/dysphonia
Elevated muscle enzymes on blood work (CK, AST)
Please contact us for more details on arranging a consultation or referral.
I need to send serum for a titer – 2M antibody (MMM) or Acetylcholine receptor (AChR) antibody (myasthenia gravis).
