In a muscle biopsy, the physicians take muscle tissue from the skeletal muscle for the diagnosis of neuromuscular diseases, for example in the presence of myopathies. Another task of muscle biopsy is the examination of the preserved tissue material. Closely related fields are neurology, neuropathology and pathology.

What is the muscle biopsy?

In a muscle biopsy, the physicians take muscle tissue from the skeletal muscle for the diagnosis of neuromuscular diseases, for example in the presence of myopathies.

Various disease processes can cause pain or muscle weakness. These abnormalities lead to permanent problems and diseases of connective tissue, nervous system, vascular system or musculoskeletal system. In the field of sports medicine, muscle biopsies are performed to gain insights into muscle metabolism during and after exercise.

Muscle biopsy is induced in the case of atypical or abnormal discomfort or when symptoms are predominantly confined to proximal muscles. Tissue sampling is an important medical instrument for the differential diagnosis of suspected ALS (degenerated motor neurological disease). Not in every case, however, it is necessary. The findings regarding the changes in muscle tissue, especially in second motoneuron diseases, are based on the evaluation of frozen muscle sections, which are routinely stained and examined with certain reagents for the existence of specific enzymes. In ALS, only slightly weakened muscles are selected for biopsy.

As a rule, the four-headed thigh muscle (quadriceps muscle), the anterior tibial muscle (tibialis anterior muscle) or the upper arm flexor muscle (biceps muscle) are used for a biopsy. Muscles that are damaged by nonspecific effects such as direct trauma, entrapment of a nerve or nerve root lesion are unsuitable. A muscle that has been injured, has been the subject of an EMG within the past three weeks, or has recently been the site of frequent injections, is unsuitable for performing the biopsy.

Function, effect & goals

The aim of the muscle biopsy is to ensure the initiation of appropriate treatment after diagnosis. It allows physicians to detect anomalies in the examined musculoskeletal system. Muscle biopsy is straightforward and performed under local anesthesia. The doctor chooses a clearly diseased muscle for this process, which, however, is not completely fatigued or atrophic.

The clinical aspect or the results of examinations (sonography, magnetic resonance tomography) are the basis for the selection of the appropriate muscle. If the choice of tissue can not be conclusively clarified, an electromyography (EMG) or an MRI is used. In order to avoid erroneous findings, the biopsy is not performed in areas where EMG electrodes have been set or intramuscular injections have been made because the muscle tissue is damaged. There are two biopsy types: open biopsy and punch biopsy. Open tissue sampling is the standard procedure. The local anesthetic is not injected into the directly affected tissue, but into the adjacent skin structures.

This is followed by a small incision that exposes the affected muscle. From this a tissue sample is taken and the wound closed after hemostasis by suture. She uses punch biopsy to remove tissue using a biopsy needle inserted percutaneously (under the skin) into the muscle. This tissue sampling is less invasive than the open method, but only a very small sample can be obtained.

If there is a suspicion of connective tissue disease of the vessels, in addition to the muscle, areas of the surrounding skin, the fascia and the subcutaneous fatty tissue are removed. Further processing of the obtained biopsy material takes place in a pathological institute. Preferably, a 2 to 3 centimeter long and 0.3 to 0.5 centimeter thick muscle bundle is applied in situ to the muscle fibers in situ (on site) at two ends on a rod (sterile cotton swab) to obtain the orientation of the tissue fibers Chopsticks excised and fixed immediately.

As a means of fixation, a buffered six percent glutaraldehyde solution consisting of 20 to 30 millimeters of phosphate buffer is suitable for the electron microscopic examination and the semi-thin section method. A similar preparation in paraffin embedding fixed in a four percent formaldehyde solution is suitable for light microscopic examination. Subsequently, an about 1 x 0.5 x 0.5 cm large muscle section for immunohistochemical, enzyme-histochemical and molecular-biological examination is excised. This piece is not to fix and not to bind to a rod, but must be frozen immediately in liquid nitrogen or immediately placed in a closed container with a damp cloth to avoid dehydration in the pathology.

The pathologists undertake the work-up and carry out the histological examination. Due to the limited shelf life, shipping is by courier. The glutaraldehyde and formalin-fixed samples are sent separately from the frozen muscle section. The containers with the inserted in the fixation muscle sections are attached to the outside of the Styrofoam box by means of adhesive strips. If they are in close proximity to the dry ice, the solutions freeze and serious artifacts occur.

Tissue sampling is induced in the following diseases:

  • Inflammation of the musculature (polymyositis, inclusion body myositis)
  • systemic inflammatory diseases (vasculitis, eosinophilic syndromes)
  • Muscular dystrophies (limb dystrophy, Duchenne muscular dystrophy, )
  • Congenital myopathies (nemaline myopathy, central-core myopathy)
  • neurogenic muscle atrophy (amyotrophic lateral sclerosis, spinal muscular atrophy)
  • Myopathies in metabolic disorders (lipid storage myopathies)
  • mitochondrial diseases (myoclonus epilepsy with ragged red fibers)
  • toxic myopathies (chloroquine, colchicine, statins)
  • Rhabdomyolysis, muscular dystrophy (muscle atrophy)
  • unclear musculoskeletal disorders

Pathological routine examinations are:

  • Elastika van Gieson staining (EvG) (fibrosis of endomysial connective tissue in myopathies)
  • Modified Gömöri trichrome staining (inclusion body in nemaline myopathy)
  • Hematoxylin-eosin staining (inflammatory infiltrates of myositis)
  • Oil-red staining (lipid storage in deficiency symptoms of carnitine palmitoyltransferase)
  • Acid phosphatase reaction (increased macrophage activity in inflammatory myopathies)
  • ATPase reaction at different pH values ​​(different fiber types and their disturbed distribution in chronic neurogenic damage)
  • NADH reaction (representation of the oxidative, intermyofibrillar network and its disorders in multicore myopathy, central-core myopathy)
  • PAS Staining (Increased Glycogen Intake in McArdle Disease)

Risks, side effects & dangers

Rare complications are infections and wound healing disorders. Since skeletal muscle tissue reacts irritable and artifact-sensitive, there is a risk of contusion or further injury to the tissue. Bruising, discomfort and easier bleeding at the donor site are possible. Before the procedure, the doctor explains the patient about the individual risks and asks for contraindications, for example, allergies to the anesthetics used. Bleeding disorders, aspirin and anticoagulants (blood thinning drugs) are important contraindications that may allow surgery only with discontinuation of the medication.

To ensure that the patient is physically fit for the procedure, the physician performs a physical examination in addition to the medical history. After the procedure, the patient can resume his normal everyday life quickly, there are only minor restrictions. He must keep the interface sterile and dry and must not burden the affected muscle tissue too much.

Typical & common muscle diseases

  • Hamstring
  • muscle weakness
  • compartment syndrome
  • Muscle inflammation (myositis)
  • Muscle atrophy (muscular dystrophy)
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