The neuromuscular system is comprised of the peripheral nerves, the muscles in the body, and the junction between the muscle and nerve. Several different disease processes can affect the neuromuscular system, and can cause a variety of clinical signs (see below).
Diagnosis of neuromuscular disease in animals is made by evaluating history, physical and neurological examinations, and then often electrodiagnostic evaluation (electrical testing of muscles and/or nerves), followed by muscle and nerve biopsies.
At the UC Davis Neuromuscular Disease Laboratory, we provide processing, histochemical staining, and interpretation of fresh muscle biopsies of both small and large animals. The NDL is supported by the UC Davis Neurology/Neurosurgery Service, with faculty board-certified neurologists, a board-certified specialist in large animal medicine, and a PhD candidate with training in histochemical staining techniques.
The Neuromuscular Disease Laboratory no longer processes serum samples for myasthenia gravis and masticatory muscle myositis. The following link has information regarding the submission of these samples to the Comparative Neuromuscular Laboratory at UC San Diego. http://vetneuromuscular.ucsd.edu
Instructions and sample submission forms:
What is the difference between fresh frozen muscle processing and sending a muscle biopsy to a commercial laboratory, preserved in a formalin biopsy container?
The chemical formalin can preserve a muscle biopsy indefinitely, but to do this, it essentially “kills” the muscle cells. On a formalin-fixed specimen, we can tell the structure of the muscle cells, but we never get an idea of their function. 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.
There is still a place for fixed muscle in the diagnosis of neuromuscular disease – electron microscopy, if needed, is done on fixed muscle rather than frozen. For clinicians collecting muscle biopsies, we recommend collecting at least a piece of one of the muscles in formalin in case EM is needed.
If I don’t submit a muscle sample in a formalin biopsy container, how do I package it to send to the NDL?
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. Detailed instructions on shipping are found here.
Which muscles should I biopsy?
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 and the gluteal muscles are often the most accessible. Detailed instructions on how to collect and package a muscle biopsy are found here.
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.
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 clinicians for consultation and even referral for assessment for neuromuscular disease, electrodiagnostics, and biopsies.
For small animal patient consults, please contact the Neurology/Neurosurgery Service at 530-754-0606 or 530-752-1393.
For equine and food animal patient consults, please contact the Equine Medicine or Food Animal Medicine services at 530-752-0290.
Contact us: 530-752-1170
Clinical signs that can be associated with neuromuscular disease.
*Generalized or focal weakness
Focal or generalized muscle atrophy
Focal or generalized muscle hypertrophy
Gait abnormalities and/or lameness
Dysphagia (difficulty eating)
Stridor/roaring (noisy breathing originating from the throat)
Dysphonia (change or loss of voice)
Elevated muscle enzymes on blood work (CK, AST)
* hallmarks of neuromuscular disease