As the median nerve travels through the carpal tunnel, it
may become compressed. Carpal tunnel syndrome is the condition of pressure
being placed on the median nerve. The transverse carpal ligament is usually
thickened at the wrist and this causes the compression of the nerve. The condition
usually occurs due to an overuse injury such as repetitive hand grip movements.
The predisposing factors for carpal tunnel syndrome include trauma, fractures,
pregnancy, diabetes, rheumatoid arthritis, ganglion cyst, smoking, alcoholism,
advanced age, and obesity. As a result of this compression, the patient may
experience pain and paresthesia in the median nerve distribution as well as
weakness in the hand. The median nerve is inside the carpal canal. The transverse
carpal ligament covers the median nerve and if this ligament is thickened, it
can compress the median nerve. It is almost like a narrow tunnel, and the
median nerve is much like a truck passing through the narrow tunnel. o angle to the skin of the wrist. Next, direct the needle
towards the base of the thumb and advance the needle distally and slowly. You should
mark the site 4-5 cm proximal to the distal palmar crease between the palmaris
longus and the flexor carpi radialis tendons. For the proximal approach, you
should advance the needle distally towards the wrist at about a 20o
angle to the skin, keep the needle between the two tendons, be aware that the
nerve is in between the two tendons (the nerve is really superficial) and
adjust the needle as needed, and then inject the desired fluid.
We try to
make room for the nerve to past through. The tunnel is widened by doing carpal
tunnel surgery. Cutting the transverse carpal ligament, as seen in this
example. We can possibly make room for the median nerve with steroid injection,
because injection will decrease the inflammation. The typical patient with
carpal tunnel syndrome will have hand pain, numbness and tingling in the radial
3 ½ fingers (median nerve distribution). These symptoms may wake the patient up
at night. Treatment is usually a night splint or anti-inflammatory medication. Sometimes
we give some patients a steroid injection which can be helpful. In general, you
will know which patients will have a good prognosis from the treatment of
carpal tunnel, and these are the patients who will have night symptoms. Another
indication for a good prognosis is the response to steroid injection. If the
steroid injection helps the symptoms, then the patient will do well from the
carpal tunnel surgery. Failure to improve after steroid injection indicates a
less favorable outcome from the surgery. The injection is usually helpful when
it is not clear to the clinician where the symptoms are coming from. If you
inject the carpal tunnel and the patient improves, then you know the
predominant problem is the carpal tunnel, because all of the three conditions
can give the same symptoms. This is especially important in double crush
syndrome where the median nerve can be compressed at two different places along
its course, and one of these places can be the carpal tunnel. Injection also
has therapeutic value. Injection allows a period of relief in patients with
mild or moderate carpal tunnel symptoms. 80% of the patients will have some
transient improvement with injection and 20% of the patients will improve up to
1 year. The median nerve is located between the palmaris longus and flexor
carpi radialis tendons. You can give the injection by ultrasound or you can do
it blindly. When you do blind injection, you can do it by the usual approach or
by the proximal approach. With the usual approach, you should mark the
intersection of the palmaris longus tendon and the distal palmar crease. Next,
go 1 cm proximal and 1 cm ulnar to that site, this will be the point of the
injection.
Use a 25 gauge needle with the preferred brand and amount of
steroids and 1 mL of 1% lidocaine. The physician should warn the patient before
the injection that if any feeling of numbness, paresthesia, or sever pain
exists to let the physician know about it. If the symptoms exist, the doctor
should withdraw the needle or adjust it before injection. You may use local
anesthesia or a spray. You should use a sterile field, make sure that you have
a consent, make sure that you have a time-out sheet, and mark the site before
injection. To administer a usual approach injection, you should put the needle
at a 45
Ganglion Cysts Pressure Motor Branch of Median Nerve
After passing through the carpal tunnel, the median nerve
gives a branch on the radial side called the recurrent motor branch. The recurrent
motor branch innervates the abductor pollicis brevis, the flexor pollicis
brevis (superficial head), and the opponens pollicis muscles.
The recurrent
motor branch of the median nerve has multiple variations of the nerve. 50% are
extraligamentous with recurrent innervation. 30% are subligamentous with
recurrent innervation. 20% are transligamentous with recurrent innervation. When
you release the carpal tunnel, it is important to cut the transverse carpal
ligament far ulnarly to avoid cutting the recurrent motor branch of the median
nerve. These are the patients that will get motor symptoms after you do carpal
tunnel release. There is another entity similar to this entity, and these are
the patients that have symptoms similar to carpal tunnel syndrome, but their presentation
is not classic. These are the patients that you may need to get an MRI or
ultrasound to check the carpal tunnel area. Pain symptoms of carpal tunnel
syndrome occur more at night. Self-administered hand diagram is extremely
helpful (most specific test for carpal tunnel syndrome). The patient should
highlight the areas where they are experiencing the symptoms. The patient may
complain of thenar atrophy, weakness, or clumsiness of the hand. The positive
compression test (Durkan’s test) is the most sensitive test. You can see the
Tinel’s Sign, do the Phalen’s test, or the Semmes Weinstein test. Some physicians
believe that EMG doesn’t really increase the diagnostic value of these tests
(if you have a combination of these test), and you will proceed with surgery
even if the EMG is normal. The problem is, that you will find a group of
patients that have weakness and atrophy of the thumb muscles, and the
provocative and sensory tests for carpal tunnel syndrome are negative. These are
the patients that you will get an MRI to rule out pressure on the motor branch
of the median nerve. These are the patients that you will probably find a
ganglion cyst pressuring the motor branch of the median nerve.
The nerve that is involved in pronator teres syndrome is the
median nerve. Pronator Teres Syndrome is caused by a compression of the median
nerve at the level of the elbow which occurs more in women. In the forearm, the
median nerve runs between the two heads of the pronator teres muscle and then
it lies between the flexor digitorum superficialis and flexor digitorum
profundus muscles. This syndrome may be associated with medial epicondylitis.
The principle symptoms of numbness in the radial 3 ½ fingers as well as thenar
weakness which may be mistakenly attributed to carpal tunnel syndrome.
The most common cause of entrapment is due to compression of
the median nerve between the two heads of the pronator teres muscle. This
commonly occurs in people who perform repetitive forceful pronation of the
forearm. Compression may be due to the thickening of the bicipital aponeurosis.
The aponeurosis crosses from lateral to medial over the antecubital fossa and
may irritate the median nerve. Compression of the nerve may also occur due to
the fibrous arch of the origin of the flexor digitorum superficialis (FDS).
The median nerve runs down the medial side of the arm and
passes 2 ½ to 4 cm below the level of the medial epicondyle before it enters
between the two heads of the pronator teres. About 1% of
patients have a medial
supracondylar humeral spur about 5cm proximally to the medial epicondyle. The
ligament of Struthers is attached to this bony projection which connects the
process to the medial epicondyle. The bony process points towards the elbow
joint and the median nerve can become compressed by the supracondylar spur. The
median nerve can also become trapped by the ligament of Struthers that extends
from the supracondylar process to the medial epicondyle. The ligament of
Struthers is different from the arcade of Struthers, which deals with the
compression of the ulnar nerve around the elbow.
Paresthesia in these lateral 3 ½ fingers may occur with the compression
of the median nerve at the elbow region or at the carpal tunnel region. These symptoms are similar to carpal tunnel syndrome but the symptoms are worse with
rotation of the forearm. The patient will complain of dull aching pain over the
proximal forearm with no nighttime symptoms. The pain is usually worsened by
repetitive or forceful pronation. Tenderness of palpation to the pronator teres
muscle will be detected. The median nerve gives off a palmar cutaneous branch
before entering the carpal tunnel. Sensory disturbances over the palm of the
hand occur due to involvement of the palmar cutaneous branch of the medial
nerve and this occurs proximal to the carpal tunnel. Sensory disturbances in
this area indicates median nerve problems proximal to the carpal tunnel. This differentiates
between carpal tunnel syndrome and pronator teres syndrome.
There are specific provocative tests that produce the pain
and distal paresthesia that are used to localize the site of compression. The
Tinel’s sign at the wrist and the Phalen’s test will be negative. The Median
nerve compression tests are negative at the carpal tunnel; however, there will
be a positive Tinel’s sign at the proximal forearm. There will be abnormal
sensation in the “palmar triangle”. When compression of the nerve involves the
supracondylar process, the test is considered positive if symptoms of tingling
worsen while tapping on the spur.
Occassionally, the spur can be felt. The
pronator teres muscle can be assessed as the cause of the median nerve
compression in different ways. Resisted forearm pronation with elbow flexion
will test for compression at the two heads of the pronator teres muscle. During
this test, the patient’s forearm is held in resisted pronation and flexion.
While remaining in a pronated position, the forearm is gradually extended.
Compression of the median nerve may also be tested by: resisted elbow flexion
with forearm supination (compression at the bicipital aponeurosis) and resisted
contraction of the FDS to the middle finger (compression at the FDS arch).
Differential Diagnosis
C6/C7 Radiculopathy occurs due to involvement of the nerves
at these levels which will cause numbness of the thumb, index, and long
fingers, as well as weakness of the muscles of the forearm that are innervated
by the median nerve. The radial nerve part of C6-C7 will show normal function
of the wrist extensors and the triceps.
X-rays, imaging and nerve conduction studies may be helpful
in the diagnosis.
Treatment typically consists of rest, splints, and NSAIDs.
Surgical decompression of the median nerve through all 4 or 5 possible sites of
compression when non-operative management fails for 3-6 months. The results of
surgery are variable. Full recovery is not always seen in all patients as only
about 80% of patients improve from surgery. The skin incision may leave an
unsatisfactory scar.
There are eight carpal bones of the wrist that fit into a
shallow socket formed by the bones of the forearm. Carpal Tunnel Syndrome
occurs when there is pressure placed on the median nerve due to thickening of
the transverse carpal ligament.
Thenar atrophy is commonly associated with
severe carpal tunnel syndrome. Carpal tunnel syndrome can occur during pregnancy
due to swelling, which compresses the median nerve in the hand, causing the
fingers to feel numb. These symptoms typically go away after the delivery of
the baby. Common causes of Carpal Tunnel syndrome are: obesity, hypothyroidism,
arthritis, diabetes, trauma, and repetitive work (typing and lifting). Carpal Tunnel Syndrome can lead to numbness,
tingling, or weakness in the hand and fingers. The numbness usually occurs at
night because we tend to sleep with our wrists flexed.
The Tinel’s test is used to determine symptoms of carpal
tunnel syndrome. The test is considered positive if symptoms of tingling worsen
while tapping on the median nerve at the wrist. The Phalen’s maneuver is a
diagnostic test performed to determine if the patient has carpal tunnel
syndrome. During this test, the back of the hands are pressed together,
compressing the nerve, which may cause the symptoms of carpal tunnel syndrome.
Treatment for Carpal Tunnel Syndrome includes:
anti-inflammatory medications, a splint, therapy, injections, and carpal tunnel
release surgery. A carpal tunnel release is performed by cutting through the
transverse carpal ligament. A carpal tunnel release allows the median nerve to
pass freely through the tunnel to receive sensations from the thumb, index, and
middle fingers of the hand. The idea is similar to a tunnel being widened so a
large truck can pass through.
Professor and chairman of the Department of Orthopaedic Surgery at the University of Toledo Medical Center, Dr. Nabil Ebraheim provides care to patients with complex fractures involving the ankles and joints. Additionally, Dr. Nabil Ebraheim maintains a YouTube channel that provides viewers an in-depth look at various issues in his area of medical focus, such as carpal tunnel syndrome.
Situated on the palmar side of the wrist, the carpal tunnel is a narrow passageway of ligaments and bones. The median nerve passes through this area, as do nine flexor tendons that help control finger and thumb movements. Carpal tunnel syndrome occurs when the transverse carpal ligament places pressure on structures such as the median nerve. Symptoms include numbness, tingling, weakness, and pain in certain regions of the hand.
In certain cases, the carpal tunnel needs to be released, or widened, to provide more space for the ligaments and nerve to pass. A key surgical concern is avoiding cutting the recurrent motor branch of the median nerve, which allows for opposition of the thumb.
