Muscle Biopsy
A muscle biopsy involves
removal of a plug of tissue usually by a needle to be later used for
examination. Sometimes more than one needle insertion may be needed to obtain a
large enough specimen. If there is a patchy condition expected an open biopsy
may be used. Open biopsy involves a small incision through the skin and into the
muscle, so that a sample of muscle tissue can be removed from the affected area.
There may be some slight bruising or bleeding at the site but the risks are
minimal with the procedure.
Alternative
names
Biopsy - muscle
Definition
A muscle
biopsy is a procedure involving the removal and examination
of a piece of muscle tissue.
How the test
is performed
A muscle
biopsy can usually be obtained while you are awake and the
area being biopsied is numbed by local anesthesia. A needle
biopsy may be adequate in children and adults with chronic
conditions. In this procedure, a needle in inserted into the
muscle. A small "plug" of tissue remains in the needle when
it is removed from the muscle. This tissue is sent to a
pathologist for examination. More than one needle insertion
may be needed to obtain a large enough specimen for testing
and examination.
Open biopsy
involves a small incision through the skin and into the
muscle, so that a sample of muscle tissue can be removed
from the affected area.
A muscle that
has recently been traumatized, such as by an EMG needle, or
that is affected by pre-existing condition, such as nerve
compression, is not a good choice for a biopsy.
The muscle
chosen for biopsy must be appropriate for the symptoms or
suspected condition.
How to
prepare for the test
No fasting or
other special preparation is usually necessary. You may be
asked to wear loose clothing or a hospital gown so that the
muscle chosen for biopsy is easily accessible.
You must sign
an informed consent form.
How the test
will feel
During the
biopsy, there is usually minimal or no discomfort. You may
feel some pressure or "tugging" sensations.
The
anesthetic may burn or sting when injected (before the area
becomes numb). After the anesthetic wears off, the area may
be sore for about a week.
Why the test
is performed
A muscle
biopsy may be performed for many reasons, including the
following:
-
To distinguish between neurogenic (nerve)
and myopathic (primarily muscle) disorders
-
To identify specific muscular disorders
such as muscular dystrophy or congenital myopathy
-
To identify metabolic defects of the
muscle
-
To diagnose diseases of the connective
tissue and blood vessels (such as polyarteritis nodosa)
-
To diagnose infections that affect the
muscles (such as trichinosis or toxoplasmosis)
Normal Values
Normal muscle
and related tissue anatomy. A microscopic examination with
and without staining that shows no abnormalities is normal.
What abnormal
results mean
A muscle
biopsy can reveal conditions such as the following:
-
Atrophy (loss of muscle mass)
-
Necrosis (tissue death) of muscle fibers
-
Inflammation of the muscle
-
Necrotizing vasculitis
-
Myopathic changes (destruction of the
muscle)
-
Muscular dystrophy, indicated by antibody
staining of the muscle biopsy specimen that can show
deficient dystrophin
-
Traumatic muscle damage
-
Duchenne's muscular dystrophy
-
Polymyositis
-
Dermatomyositis
Additional
conditions under which the test may be performed include the
following:
-
Becker's muscular dystrophy
-
Charcot-Marie-Tooth disease (hereditary)
-
Common peroneal nerve dysfunction
-
Eosinophilic fasciitis
-
Facioscapulohumeral muscular dystrophy (Landouzy-Dejerine)
-
Familial periodic paralysis
-
Friedreich's ataxia
-
Polymyalgia rheumatica
-
Senile cardiac amyloid
-
Thyrotoxic periodic paralysis
What the
risks are
The risks are
minimal and may include the following:
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