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
What is the course of the ulnar nervee
continuation of the medial cord, carries C8/T1 fibers
name the branches of the ulnar nerve
- Flexor carpi ulnaris
2 4th and 5th digits to the Flexor Digitorum Profundus
3 Dorsal ulnar cutaneous branch. If Comes off before
the wrist and does the back of the hand (dorsal surface) of the
4th and 5th digits up to the DIP joints
4 Palmar cutaneous branch – variable distribution of the hypothenar eminence
5 superficial branch – palmar aspect to 4th and 5th digits (Sensory nerve)
6 motor branch to pisiform bone and hook of the hamate
and there’s a variability there: one branch might come off to the hypothenar muscles the ADM. It can come off before it passes through the slip or it can come off before (see figure 2: anatomy of the canal of n) with a continuation to the deep motor branch which goes to the interossei muscles and the 3rd and 4th lumbrical muscles. -that variation there can give you multiple clinical variations when you do your study depending on where the compression may be for the ulnar neuropathy at the wrist.
name the locations where ulnar entrapment can occur (4)
- internal bracial ligament & arcade of struthers
- tardy ulnar palsy
- cubital tunnel syndrome
- guyons canal
which entrapment?
radially deviate on WF, numbness on back of hand and palm. wartenburg sign due to unopposed extensor. Froments sign. Benedict sign when opening hand. finger flexors intact (FDS intact), hyper ext of 4th and 5th MP joints
internal brachial lig & arcade of struthers.
- Internal brachial ligament – p 876 – hasn’t seen on test question, but for completeness to know. As the ulnar nerve dives deep into the posterior nerve
- Arcade of struthers (not equal to the ligament of struthers) A and U are vowels
-if you have an arcade of struthers – abnormal FCU, FDP 4th and 5th, first DI, ADM, and when you do the study above the elbow, you’ll see slowing across that area and a drop in amplitude
-[ TQ ] Froment’s Sign – give pt a piece of paper and loss of ulnar nerve use Flexor Pollicis Longus and Flexor digitorum profundus to hold onto paper, and buckle thumb. Pt uses AIN to become pincher vs using ulnar adductor and 1st DI
Wartenbergs sign – can’t adduct 5th digit – PAD And DAB are out, Extensor digiti minimi takes over
_____– can’t adduct 5th digit – PAD And DAB are out, Extensor digiti minimi takes over
Wartenbergs sign
______ – give pt a piece of paper and loss of ulnar nerve use Flexor Pollicis Longus and Flexor digitorum profundus to hold onto paper, and buckle thumb. Pt uses AIN to become pincher vs using ulnar adductor and 1st DI
-[ TQ ] Froment’s Sign
____ is usually result of fracture typically in adolescents or youth that becomes hypercalcified and changes the carrying angle of the forearm. It gets the ulnar nerve as it goes below the medial condyle.
tardy ulnar palsy
which fractures are associated with tardy ulnar palsy
medial epicondyle in condylar groove
______ is a result of result of compression of the two heads of the flexor carpi ulnaris. Classically the branch to the FCU comes off before and so if you have compression of the FCU, the FCU will be normal on EMG. = ulnar neuropathy at the elbow. Difficulty is that you can’t localize it better than saying it’s at the elbow.
-DUC will be abnormal
-inching technique is not accurate
-> 11 m/c drop at the elbow
-FCU spared – cubital tunnel syndrome
cubital tunnel syndrome aka FCU syndrome
FCU spared
what differentiates ulnar neuropathy at the elbow from wrist?
DUC (not affected at wrist)
what are the three types of ulnar neuropathy at the wrist?
Type 1 – sensory/motor loss (main br and superficial br) (48%)
Type 2 – motor loss only (deep br ) (44%)
Type 3 – Sensory loss only (superficial br) (8%)
guyons canal is covered by
pisohamate ligament
Compression of the ulnar nerve at Guyon’s canal may spare the ___
hypothenar muscle
course of radial nerve
Upper, middle and lower trunk
Posterior divisions, posterior cord then branches into axillary nerve and the radial nerve
C5-C8
Branches off of the radial nerve
1 long head of triceps (C6,7,8)
2 lateral head of triceps (C6,7,8)
3 medial head of triceps (C6,7,8)
4 anconeus (injury at spiral groove, can still have good elbow extension) (C7,8)
-Terminal extension of elbow
5 posterior cutaneous branch to forearm
6 brachioradialis (C5,6)
-after spiral groove
7 Extensor Carpi Radialis Longus (C6,7)
8 Superficial Sensory
-(comes off before elbow)
9 Extensor Carpi Radialis Brevis (C6,7)
10 Supinator (C5,6)
-Posterior interosseous nerve through Supinator at Arcade of Frosche
11 Extensor digitorum communis/longus (C6,7,8)
12 Extensor Digiti minimi
13 Extensor Carpi Ulnaris
14 Abductor pollicis longus (C6,7,8)
15 Extensor Pollicis longus (C6,7,8)
16 Extensor Pollicis Brevis
17 Extensor indicis (C7,8)
What are the 2 sites of radial nerve entrapment
- spiral groove; honeymooners palsy
- radial tunnel/supinator syndrome
which entrapment?
-weak brachioradialis, finger extension, wrist extension
- cant supinate except with biceps
-triceps spared (elbow extension), everything below involved
radial nerve in spiral groove
occurs with humeral neck fractures, crutch palsy, sat night palsy, honeymooners palsy
which entrapment?
weak/ absent 2nd, 3rd, 4th and 5th finger extension and thumb extension
Radial deviation with wrist extension (ECRL and ECRB working, ECU not working)
Sensory preserved in UE
1 Supinator syndrome – arcade of Frosche
Sensory spared (numb thumb study normal)
-motor abnormal
- radial tunnel syndrome
MAY get sensory involvement with radial
course of peroneal nerve
o Sciatic nerve has lateral/peroneal division and medial/ tibial devision
o after hip dislocation or fracture ____ more likely to be involved than medial/tibial division resulting in foot drop
lateral/peroneal division
at _____ of thigh sciatic has bifurcated into common peroneal and tibial nerves
distal 1/3
Common peroneal nerve innervates only one muscle into posterior thigh which is ____
SHORT HEAD OF THE BICEPS FEMORIS [TQ] – comes off the lateral division of sciatic nerve
Then as it comes around the fibular head divides into deep and superficial peroneal nerves
name the components of the superficial peroneal nerve (3)
Peroneus Longus (L4-S1)
Peroneus Brevius (L4-S1)
Sensory to dorsum of the foot except 1st web space
name the componentsof the deep peroneal nerve (anterior compartment) (6)
Anterior Tibialis (L4-L5)
Extensor Digitorum Longus (L4-S1)
Extensor Hallucis Longus (L4-S1)
Peroneus Tertius (L4-S1)
Extensor Digitorum Brevis (L5-S1)
Sensory to 1st web space
There can be an accessory peroneal br from _____ to _____
how to find it?
from superficial peroneal to lateral portion of EDB
stim @ ankle amp 5mV
then @ head of fibula 8mV
28% of pop
what % of population has accessory peroneal
28%
Where are the 2 entrapment sites of peroneal nerve
- posterior lateral approach hip replacement
- fib head - diff b/w popliteal and stim in front of fib head.
what is the differential diagnosis for foot drop? 4
L4 or L5 radiculopathy, sciatic nerve injury (lateral) distal sciatic nerve injury, deep peroneal nerve injury)
what syndrome?
Deep peroneal nerve at ankle
Numbness 1st web space and weak/atrophy Extensor digitorum brevis
anterior tarsal tunnel syndrome - rare
what syndrome?
Compression by flexor retinaculum at the ankle – medial side.
tarsal tunnel syndrome
Difficult to diagnosis with EMG/NCS
Tibial nerve divides into medial plantar nerve, lateral plantar nerve and calcaneal branch
what is the timing outline for EMG after injury
Acute ( must wait 21 days for EMG findings to occur and 4 days for Wallerian degeneration to occur for NCS to be helpful )
Subacute ( 6-9 months )
Chronic ( 12-18 months )
Name the branches of tibial nerve (15)
- LHBF
- ST
- SM
- ADDUCTOR MAGNUS
- plantaris
- gastroc (2H)
- popliteus
- soleus
- FHL
- FDL
- TP
- Med calc br
- lateral plantar
- medial plantar
15 abductor hallicus
course of tibial nerve
medial sciatic
o Sciatic nerve has lateral/peroneal division and medial/ tibial devision
emg not useful in foot why?
people have findings in foot due to chronic overuse
Sural comes from which nerve?
tibial and common peroneal
sural serves sensory to
below knee prox calf (more tibial)
gives sensory to lateral foot/leg
Saphenous lies _____ and is more difficult to obtain
saphenous
EMG tests ____ fibers
1A myelinated fibers
can assess therapeutic benefit (ie steroid myopathy)
EMG evaluates what 4 things
motor unit, MN cell body, axon, NMJ
What is wallerian degeneration?
degeneration distal to injury and slightly proximal
decreasing sweep speed will allow:
closer look at waveforms
gain is usually ____ divisions
Sweep is typically ___ boxes
6 divisions (typ 50uV spont/100-500 to adjust for MUAP)
20 boxes (typ 10ms/div)
