Muscle Biopsy

CHAPTER 228 Muscle Biopsy



James R. Shepich


Many disorders of the motor unit can be identified by clinical presentation, but occasionally a muscle biopsy is necessary for diagnosis. Muscle biopsy is a relatively straightforward procedure that may be performed under local anesthesia. However, many authorities contend that a better-quality specimen can be obtained under general anesthesia because injudicious local infiltration can affect the histology. The site of biopsy and the type of biopsy (open vs. core needle) vary with the patient and disease.


The muscle of choice should show the effects of the disease process. However, the most severely affected muscles should be avoided because the muscle mass may be replaced by scar tissue or fat, and an adequate pathologic diagnosis may not be possible. Muscles with recent trauma, including recent electromyography (EMG) or infection, should not be sampled. Muscle in areas of tendinous transition should be avoided because the increased connective tissue may be mistaken for fibrosis during pathologic assessment. Some commonly sampled muscles include the lateral aspect of quadriceps femoris, deltoid, biceps brachii, tibialis anterior, and gastrocnemius.


The biopsy method depends on clinical judgment. Core needle biopsy is less invasive and causes less pain and scarring than open biopsy. It is easier to perform, especially in children, and allows repeat biopsy of the same muscle if necessary. Open biopsy allows a larger specimen to be taken, which increases the chance of definitive diagnosis and allows multiple modalities of pathologic preparation of the specimen if needed, including electron microscopy. Open biopsy is also ideal if disease of the motor end plate is suspected. With either approach the muscle to be sampled should be placed in an extended, relaxed position.



Indications


A muscle biopsy is performed to identify syndromes of muscle weakness that do not present with classic findings. Several diseases, such as Duchenne’s muscular dystrophy, Werdnig-Hoffmann disease, and myasthenia gravis, have classic presentations and muscle biopsy is not necessary. Muscle biopsy can be used to distinguish between neurogenic and myopathic processes, identify congenital myopathies, and diagnose connective tissue disorders and muscle infections, such as trichinosis and toxoplasmosis. Metabolic disorders of the muscle may also be found by biopsy. Biopsy is also indicated in the identification and indexing of hereditary disorders.



Contraindications



• Anticoagulation and bleeding disorders

• Recent trauma of the muscle, including EMG

• Clinical appearance of Duchenne’s muscular dystrophy (biopsy can cause scarring and contracture of muscle)

• Infection in region of proposed biopsy


Equipment



Open Biopsy



• Sterile drapes

• Povidone–iodine

• Local anesthesia (1% lidocaine without epinephrine)

• Scalpel with no. 11 or no. 15 blade

• Forceps, iris scissors, suture scissors

• 3-0 Vicryl or Monocryl sutures

• 4-0 Vicryl or Monocryl sutures

• Electrocautery or diathermy (not to be used until after biopsy sample is procured)

• 4 × 4 gauze sponges

• Tongue blade, cut into 6- to 7-cm lengths, with V-groove in ends, or 22-gauge needles to pin specimen

• 3-0 nylon or Prolene suture

• Steri-Strips, Tegaderm, Op-Site, or dressing of choice


Core Needle Biopsy



• Sterile drape

• Povidone–iodine

• Local anesthesia

• Tru-Cut, Biopty, Conchotome, or equivalent needle

• Band-Aid


Preprocedure Patient Preparation


The patient should be informed that the procedure is relatively painless, but that the biopsy site may be sore for several days. Many patients experience a sensation of muscle bruising and occasionally a pulling sensation. The patient does not need to restrict food and fluids before the procedure, but he or she should be instructed to wear loose-fitting clothes that readily allow access to the intended biopsy site. Little postprocedural disability or recovery time is expected and the patient may return to usual activity immediately. Analgesic medication is rarely needed, and when it is necessary, it is usually only for 24 to 48 hours. Risks, benefits, and potential complications should be discussed with the patient before the procedure (see the sample patient education handout online at www.expertconsult.com).

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May 14, 2017 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Muscle Biopsy

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