Entrapment neuropathies commonly affect the following nerves except:
|C||Lateral cutaneous nerve of thigh|
Median nerve at the wrist (carpal tunnel syndromE.
Carpal tunnel syndrome (CTS) is the most commonly encountered nerve entrapment condition.
a. Median nerve compression at the wrist is near the TCL, which attaches to and arches between the pisiform and hamate on the ulnar side and the scaphoid and trapezium on the radial portion.
b. The median palmar cutaneous nerve originates from the radial side of the median nerve proximal to or just deep to the flexor retinaculum, then transverses superficially to the flexor retinaculum to innervate the thenar eminence (thumB. and the palm roughly up to the vertical line overlying the fourth metacarpal (finger).
c. Motor nerve to the thenar muscles leaves the median nerve radially just beyond the distal edge of the flexor retinaculum, but variant nerves may pierce through the flexor retinaculum or arise from the ulnar aspect of the median nerve and an accessory motor branch may even emerge proximal to the flexor retinaculum.
d. The ulnar nerve (10%) and artery (4%) lie radial to the hook of the hamate outside of the Guyon canal, placing them at risk for injury during carpal tunnel surgery.
Lateral femoral cutaneous nerve (meralgia parestheticA.
a. The lateral femoral cutaneous nerve (LFCN) arises from the ventral rami of the L2 and L3 nerve roots. This purely sensory nerve is formed just deep to the lateral border of the psoas muscle, then descends in the pelvis over the iliacus muscle deep to the iliacus fascia.
b. Just medial to the ASIS, the nerve exits the pelvis by passing through the deep and superficial bands of the inguinal ligament as they attach to the ASIS.
c. The nerve is almost horizontal while still within the pelvis before it passes the inguinal ligament, but then it takes a vertical course out to the surface of the thigh.
Tarsal tunnel syndrome
Compression of the posterior tibial nerve behind the medial malleolus, or tarsal tunnel syndrome (TTS), is an uncommon entrapment neuropathy.
The roof of the tunnel is formed by the flexor retinaculum stretched between the medial malleolus and the calcaneus. The tarsal bones are the floor. Numerous fibrous septae between the roof and the floor subdivide the tunnel into separate compartments at various points.