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.
Ganglion
cysts can occur anywhere. They usually occur at the wrist area, however,
ganglion cysts may occur at the foot (usually at the top of the foot). This mass
can change in size, and it may grow slowly. The patient notices a mass usually
on the top of the foot. The mass is usually asymptomatic. The patient may have
a burning sensation due to irritation of the nerve when the ganglion compresses
the nerve. The patient may have skin irritation and also may have difficulty
walking and wearing shoes. If the ganglion is pushing on a nerve and causing
irritation, aspiration or surgical removal of the cyst can help relieving the
symptoms. We need to differentiate ganglion cyst of the foot from plantar
fibromatosis. Plantar fibromatosis occurs at the bottom of the foot. Ganglion cysts
usually occur at the top of the foot. Ganglion cysts will transilluminate. Plantar
fibromatosis does not transilluminate
Ganglion Cyst of the Ankle (Tarsal Tunnel Syndrome)
What is
Tarsal Tunnel Syndrome?
Tarsal
tunnel syndrome is a compressive neuropathy which is caused by compression of
the tibial nerve around the ankle region. A ganglion cyst can be one of the
intrinsic causes of tibial nerve compression. In the tarsal tunnel, the patient
may have pain and burning sensation. An MRI is probably needed for the
diagnosis of a ganglion cyst in the tarsal tunnel. They found that they best
result after surgery occurs when there is a ganglion cyst compressing on the
nerve, and this cyst is removed.
