A muscle biopsy is a medical procedure that involves taking a small sample of muscle tissue for examination under a microscope. This tissue sample helps medical professionals diagnose various muscle-related conditions, also known as myopathies. By analyzing the cellular structure and composition of the muscle tissue, doctors can gain insights into the underlying cause of symptoms like muscle weakness or pain.
Reasons for a Muscle Biopsy
A muscle biopsy is recommended when a doctor suspects an underlying muscle condition based on a patient’s symptoms, physical examination, or initial blood tests. Conditions that can cause these symptoms might involve problems with the nervous system, connective tissue, vascular system, or the muscles themselves.
The biopsy helps differentiate between myopathies, where the issue is within the muscle tissue, and neuropathies, which involve the nerves supplying the muscles. It can also distinguish among various types of myopathies through microscopic analysis. For example, a muscle biopsy can diagnose muscular dystrophies, a group of genetic disorders where muscles break down and are replaced by fatty deposits.
Other conditions a muscle biopsy can help identify include inflammatory muscle diseases like polymyositis and dermatomyositis, which cause inflammation of skeletal muscles or skin and muscles, respectively. It can also detect metabolic disorders affecting muscles, such as Pompe disease, or parasitic infections like trichinosis. The procedure provides insights into muscle fiber degeneration, inflammation, or the presence of specific proteins.
How a Muscle Biopsy is Performed
A muscle biopsy procedure involves either a needle biopsy or an open biopsy, with the chosen method depending on the amount of tissue needed and the specific condition being investigated. Before the procedure, patients may be asked to fast for about six hours and review their current medications with their doctor, especially blood thinners. Patients are advised to arrange for transportation home afterward due to the effects of medication.
Needle Biopsy
For a needle biopsy, the healthcare provider cleans the biopsy site, often in the thigh, upper arm, or shoulder, with an antiseptic solution. A local anesthetic is then injected to numb the area, which might cause a brief stinging sensation. A small incision is made, and a hollow needle is inserted into the muscle to collect small pieces of tissue. Multiple insertions might be necessary to gather a sufficient sample, and patients may feel pressure or a “nipping” sensation as the tissue is collected.
Open Biopsy
An open biopsy is a more involved surgical procedure, performed when a larger muscle sample is required. After the area is cleaned and numbed with local anesthesia, an incision is made through the skin to access the muscle. The surgeon directly removes a small section of muscle tissue. The incision is then closed with stitches, and a sterile dressing is applied. The entire procedure is quick, lasting 10 minutes for a needle biopsy or 30 minutes for an open biopsy, and is performed on an outpatient basis.
After the Biopsy: Recovery and Understanding Results
After a muscle biopsy, patients receive instructions for wound care to promote healing and prevent complications. The biopsy site should be kept clean and dry for a few days, and strenuous activities, including heavy lifting or intense exercise, should be avoided for at least a week or two. Pain and soreness at the site are common for 2 to 3 days, and over-the-counter pain relievers, as recommended by the doctor, can help manage discomfort.
Patients should monitor the biopsy site for any signs of infection, such as increased redness, swelling, warmth, or discharge, and contact their healthcare provider if these symptoms appear. If stitches were used, they may need to be removed in 10 days, while adhesive strips fall off on their own within a few days. For leg biopsies, it is recommended to minimize weight-bearing for 2 to 3 days, gradually increasing activity.
The muscle tissue sample is sent to a laboratory for detailed analysis by a pathologist. Initial reports of the findings are available within a few weeks, though complex analyses might take longer. The pathologist examines the tissue under a microscope and may perform additional tests, such as applying stains or checking for specific proteins or antibodies. The results are then sent to the referring doctor, who will explain the findings and discuss what they mean for the patient’s health and any subsequent treatment plans.
Possible Complications
While muscle biopsies are considered safe, some risks are associated with the procedure. Bruising and localized pain at the biopsy site are frequently experienced. Mild bleeding or discharge from the wound can occur for a few days after the procedure.
Less common but more serious complications include infection at the biopsy site. Excessive bleeding is also a possibility. Nerve damage may occur, leading to temporary numbness, tingling, or weakness in the affected area. A small scar is expected at the incision site, and a hard lump, known as a hematoma, may develop under the skin due to a collection of blood.