Entrapment Neuropathy Flashcards
course of median nerve
medial and lateral branch, from medial and lateral cord, encompasses C5-T1
1st branch:
three places it can branch in order
pronator teres
prior to medial condyle (40-58%)
at medial condyle (13-20%)
distal to medial condyle (40-45%
What are the 12 branches of the median nerve.
- pronator teres (medial condyle)
- FCR
- palmaris longus
- flexor digitorum superficialis
- AIN (OK Sign)
- FDP (2 and 3)
- Flexor pollicis longus
- pronator quadratus - Palmar cutaneous branch
- Recurrent branch
- Abductor pollicis brevis
- Opponens pollicis
- Superficial head (SH) to flexor pollicis brevis
- sensory branch to palmar surface of 1st, 2nd, and 3rd digits but also comes over and goes to back side of DIP joint of the 1st, 2nd, and 3rd digits and 1/2 the 4th digit.
- 1st 2 lumbricals
AIN has some sensory input although thought to be pure motor: where?
wrist capsule; no cutaneous
AIN from median
____ branch of median nerve can be injured during CTR and patient will have numbness at base of the thumb but will be better otherwise
palmar cutaneous branch
What is the most common complication after CTR?
recurrent motor branch for open CTR
palmar cutaneous branch for endoscopic release
what are the borders of the carpal tunnel
Roof flexor retinaculum
Base: 4 bones: trapezium, trapezoid, capitate, hamate
What travels through the carpal tunnel?
FDP (4 tendons), FDS (4 tendons), flexor pollicis longus, median nerve (9 tendons, 1 nerve)
FCR is part of the wall and goes through its own tunnel
distal sensory branch of median reaches what dermatome?
sensory branch to palmar surface of 1st, 2nd, and 3rd digits but also comes over and goes to back side of DIP joint of the 1st, 2nd, and 3rd digits and 1/2 the 4th digit.
Where is the entrapment?
wont be able to pronate BR intact wrist will ulnarly deviate on wrist flexion benedict sign when closing fist thenar wasting loss of thumb opposition
median nerve at lacertus fibrosus/bicipital aponeurosis
OR
ligament of struthers - found in 1% of the population; bony spicule off of the distal humerus (lig—> humerus) affects PT
All muscles lost
— cant distinguish on EMG unless bad enough to get axonal injury
Where are the 6 places the median nerve can be entrapped?
- lacertus fibrosus/bicip aponeurosis
- ligament of struthers
- PT syndrome - between 2 heads and underneath the fibrous portion of FDS
- AIN
- median neuropathy of the wrist
- damage to recurrent motor branch
what is out when benediction sign is apparent when closing a fist
AIN
FDS
FDP
FPL
____ is the spicule that comes off the shaft of the humerus. It goes over to the epicondyle and then the median nerve runs underneath that and gets pinched.
what muscle is typically affected
Ligament of struthers
pronator teres
1% of population
Where is the entrapment?
hypertrophy, grocery bag palsy. presents with dull insidious forearm pain with forced pronation
pronator teres syndrome
Where are the two sites where pronator teres syndrome can occur
- between the two heads of PT
- at the fibrous arch of FDS as it dives deeper in the forearm.
PT is not affected bc branch comes off before it gets to the compression area.
where is the entrapment?
OK sign positive
cant pick up pennies and small things because they cant get FPL and FP to work well. Clinically dull forearm pain.
AIN syndrome
what would EMG/NCS look like in AIN syndrome?
would be normal bc we cant assess the AIN on normal routine median nerve study.
have to stick the needle into the three muscles the AIN innervates (FPL, FDP (2-3) and PQ) on EMG
which muscle should you test in suspected AIN syndrome?
if you use the needle for NCS you can’t compare amplitdues but you can compare ____
flexor pollicis longus
latency, look for slowing side to side
what is the most sensitive test for median neuropathy at the wrist
mid-palmar comparison study median to ulnar >.2msec is positive
what is the combined sensory index?
study to thumb, midpalmar study, and ring finger (.3, .2, .4)
equals
median neuropathy at the wrist is bilateral in ____% of patients
68 with or without symptoms
how do you classify median neuropathy at the wrist?
Mild
Mod
Severe
mild: sensory only
Mod: sensory and motor
severe: sensory and motor with emg findings
What is the recovery time for the following after CTR: median neuropathy at the wrist: 1. ischemia to nerve 2. axonal injury 3. myelin damage
- within 30 mins
- months
- weeks
should retest at 6 wks post op
will never return to normal
3 findings on EMG/NCS with martin gruber anastomosis
- Positive deflection at the elbow
- Slightly higher amplitude at the elbow
- Supratherapeutic velocity.
- What happens is that when you stimulate below the branch you get normal findings. When you stimulate above it you a positive deflection with increased amplitude.
- When you do calculations for conduction velocity, you get a supra velocity in the upper 90’s to 100’s. The amplitude is slightly higher.
what is martin gruber anasatomosis
-ulnar nerve fibers (C8-T1) that travel along the median nerve and cross over in the forearm from the AIN (anterior interosseous nerve) cross in the forearm into the ulnar nerve and then enter into the hand through the ulnar `nerve. They go to ulnar innervated muscles FDI, ADM, deep head of FPB and the adductor pollicis.
martin gruber anastomosis will be most apparent with ____
median neuropathy at the wrist
He’s had several people come to him after carpal tunnel release and ask him to assess the recurrent motor branch.
Basically, you do the regular median study to the ABP above the wrist and in the mid palm and stick the needle in the Abductor pollicis brevis. If they have fibs and positive sharp waves (PSWs) and show a drop in amplitude then they’ve probably had an injury to the recurrent motor branch. Especially if you knew what they were before. If they didn’t have fibs and PSWs and they have them now then probably injury occured. It’s nice to have the data before from the pre test.
how do you tell acute, subacute and chronic on EMG
-1. Acute – fibs, PSWs, decreased recruitment, no polyphasics, no large amplitude
7-21 days
-2. Subacute – fibs, PSWs, decreased recruitment, polyphasic
3-6 months
-3. Chronic – fibs, PSWs, decreased recruitment, polyphasic, large amplitude
9-12 months
