Unusual NCS

Question 1

Superficial peroneal sensory study is a _____ study to which nerve root?

Answer 1

pure sensory

L5

Question 2

Helpful with diagnosis of where pathology is in _____

Answer 2

footdrop

could be from lumbosacral plexus injury, peroneal motor nerve injury, sciatic nerve injury (lateral devision) or from L5 radiculopathy

Question 3

Why is the superficial peroneal nerve not compressed in tarsal tunnel?

Answer 3

passes superior to tarsal tunnel.

Question 4

What is the anatomy of the peroneal nerve (superficial branch)

Answer 4

branch off the common peroneal just below the fibular head. It goes into the lateral leg and innervates (motor wise) the peroneus longus and peroneus brevis It pierces the deep fascia in the lower part of the leg and comes back superficial. It crosses above the extensor retinaculum at the ankle. The superficial peroneal sensory nerve would be normal in anterior tarsal tunnel syndrome. When it pierces through the distal fascia, it branches into two peripheral branches: medial dorsal cutaneous nerve and the intermediate dorsal cutaneous nerve. Those two branches innervate sensation to the entire dorsal aspect of the foot except for the first web space (deep peroneal nerve).

Question 5

How do you set up for superficial peroneal sensory study

Answer 5

bimalleolar line. You feel for the edge of the tibia and to the lateral malleolus you go halfway along that line. You go 3 cm proximal to the bimalleolar line. Lateral malleolus, and the edge of the tibia (bimalleolar line), go 3 cm proximal and place the active electrode. The reference is 4 cm distal to that. Put the ground on the leg, measure back 14 cm from the active electrode (sensory study), and palpate the shaft of the fibula, and stimulate anterior over the shaft of the fibula. We’re basically picking up over the intermediate dorsal cutaneous nerve when we do that.

Question 6

The superficial peroneal sensory nerve is absent bilaterally in ____% of people

Answer 6

2

Question 7

people > ____ yoa may not have findings for superficial peroneal and sural nerves

Answer 7

65, due to age; small nerves

Question 8

femoral nerve motor study is used for femoral neuropathy which can be caused by which two major things

Answer 8

femoral art line with hematoma after

pelvic cancer with radiation to the area

Question 9

loss of femoral nerve would cause which sensory loss?

Answer 9

loss of sensation down medial leg/foot (saphenous nerve is terminal extension of the femoral nerve)

Question 10

how do you set up for femoral motor nerve test?

Answer 10

do the test with a monopolar needle pickup. Put the needle into the vastus medialis obliquis (VMO). Put reference over superior patella. Stimulate along the ilioinguinal ligament. Feel for femoral artery (NAVEL). Stimulate over nerve both above and below the ilioinguinal ligament (3 cm above and 3 cm below)

- do normal leg first
- if conduction block - Stimulate below ilioinguinal ligament – should be normal.   - Stimulate above ilioinguinal ligament, it should be abnormal - pickup with monopolar needle.  Can use it to find conduction block (greater than 50% reduction in amplitude) because you don’t move the pickup (monopolar needle).  You can compare amplitudes along the femoral nerve on the side you’re testing.  You can’t compare amplitudes from one leg to the other (because you will have moved the needle and can’t be sure you’re the same depth from the nerve).

Question 11

Can confuse femoral nerve injury with ______.

how do you tell the difference

Answer 11

• can confuse femoral nerve injury with diabetic amyotrophy (lumbar polyradiculopathy affecting L2-4 roots)
• In diabetic amyotrophy, both the adductors and femoral nerve affected.
• In femoral nerve entrapment – only the femoral nerve affected.
  
  • reminder: adductor magnus is dual innervated with obturator and sciatic component

Question 12

NCS for lateral femoral cutaneous nerve?

Answer 12

• NCS: Feel for ASIS, go 1 cm midline to that, and stimulate. Go distal 14 cm, put pickup surface electrode on the lateral thigh, with reference 4 cm distal to that
• side to side comparison
• most efficacious way to identify this pathology: [TQ] Somatosensory Evoked Potentials
• Can also diagnose with a diagnostic block to see if it improves

Question 13

most efficacious way to diagnose lateral femoral cutaneous nerve pathology?

Answer 13

somatosensory evoked potentials

Question 14

How do you perform the saphenous sensory study?

what is it the terminal extension of?

Answer 14

• terminal extension of the femoral nerve
  
  • medial leg and medial foot

-feel for medial malleolus, and the tibialis anterior tendon, go ½ way between the two and put the pickup. Put the reference 4 cm distal. Stimulate 14 cm proxima (sensory study). Feel for the medial edge of the tibia and stimulate right under the medial edge of the tibia. The nerve is very deep there, so you have to turn up the duration and intensity (painful)

Question 15

_____ is also known as backpackers palsy or ruck sac palsy

Answer 15

spinal accessory nerve

Question 16

The spinal accessory nerve has 2 components:

Answer 16

-The spinal accessory nerve has 2 components.

1. Accessory (bulbar) component
   - special visceral efferent fibers and those are rising from the nucleus ambiguous located in the medulla. (bulbar – come off brainstem) They join the spinal portion of the nerve near the jugular foramen.

-Accessory special visceral afferent fibers separate from the spinal portion near the jugular foramen and unit from the fibers of Cranial nerve 10 and go to the muscles of the pharanx. They don’t make it out to the SCM or the trapezius.

2. Spinal component
   - Consists of the first 5 cervical segments and they ascend within the spinal canal and enter the cranium through the foramen magnum and then join with the bulbar fibers to exit out the jugular foramen and innervate the
3. Sternocleidomastoid muscle
4. trapezius muscle.

• You can also see that there is a branch at C2 that exits out the foramen and merges with the spinal accessory nerve under the SCM. It moves towards the trapezius and sort of makes a plexus and then there’s some more innervation from the spinal nerves (some people say it includes C2, C3, C4 some people say it even includes C5 [controversy]). (almost dual innervated as it meets up with the C2-4). There are really two areas where they come out of the foramen and form a plexus that’s right under the trapezius muscle. One major component from C2 and then some other ones from C3, C4, C5 into this plexus
• The primary innervation is through the main spinal accessory nerve, but part of the lower trapezius get some of the fibers from C3 and C4. You could have an injury at different places and have some function of the trapezius. If you have a C2 injury that goes the major component of the trapezius muscle, you may have that upper and middle trapezius out, but there might still be some function of the lower trapezius depending on where the injury is.

Question 17

Why might the lower trap be okay with spinal accessory nerve involvement?

Answer 17

if intracranial lesion, lower trap receives more c fibers than from accessory so may have atrophy of upper and middle but not lower.

Question 18

If the trapezius is no longer working, what kind of scapular winging will you have

Answer 18

lateral winging on trap activation.

Question 19

if the serratus anterior is out, will have what kind of winging?

Answer 19

medial winging.

Question 20

What are the three locations of pathology for spinal accessory nerve?

Answer 20

1. intracranial (meningioma or acoustic neuroma)
2. intraspinal - canal (also bulbar [pertaining to the medulla oblongata] lesions) problems, syringomyelia, tumors, intracranial mass like meningioma and acoustic neuroma
   - usually SCM and trapezius affected
3. peripheral injury (SCM will be spared) secondary to something like radical neck dissection (sacrificed in posterior dissection)

(blunt trauma) radial neck dissection (head and neck cancer), lymph node biopsy. (blunt trauma) Stretch injury ie. If force on top of shoulder which depressed their shoulder can injure the spinal accessory nerve. Radiation, carotid enderaterectomy, coronary arty bypass grafts (when they do sternotomy).
-usually only trapezius affected (Can’t shrug shoulder), but SCM spared

Question 21

if spinal accessory nerve is lost will see:

1. _____ disharmony
2. ______ scapular winging

Answer 21

They will have significant scapular, scapulothoracic disharmony (no 3:2 motion). They can’t shrug and they will have lateral winging of the scapula.

Question 22

how do you test for scapular winging

Answer 22

• To test for scapular winging: Resisted forward flexion. Push on a wall, or push down if laying on belly.
• First look at them and then make a mark along the spinous process of the mid or upper thoracic spine and measure from the inferior angle to that point to see if the inferior angle is laterally deviated. Without even doing any motion, you can see it. When you ask them to do resisted forward flexion, the lateral border of the scapula will come off the thoracic cage. [drawing from board]
• Lateral scapular winging is from trapezius weakness. [TQ]
• medial scapular winging is from long thoracic nerve weakness/serratus anterior weakness
• ddx for medial scapular winging: rhomboid weakness

Question 23

how do you perform NCS for spinal accessory nerve?

Answer 23

• Test for NCS:
• measure from tip of shoulder (AC joint) to the midline (spinous process) and you put the active on that line at the midpoint. Put the reference over the tip of the acromion. Put the ground between the stimulation and the pickup. Stimulate behind the SCM at the level of the thyroid cartilage. (get them to turn to find the thyroid cartilage.) Anode is superior (red). It’s a motor study so measure the onset. Amplitude is baseline to peak. The key thing is…there are some normals, but best thing is to do side to side with testing the unaffected side first.
• it’s a good muscle to do repetitive stimulation on for a proximal muscle. Stabilize it by getting the pt to sit in a chair and have them hold the bottom of the chair so there is no movement.

Question 24

suprascapular nerve course

Answer 24

• branch off the upper trunk, it contains fibers from C5 and C6
  
  • goes to supraspinatous and the infraspinatous

Question 25

how to do NCS for suprascapular nerve

Answer 25

• 1. Take EMG and put pickup in supraspinatous and put reference at AC joint. Ground between and stimulate at Erb’s point. If you use needle pickup, can’t compare amplitude. You’re only looking at the latencies if one is slower than the other.
• 2. The surface pickup is that you put the pickup over the insfraspinatus midway between the scapula and the acromion, 2 cm below the spine of the scapula. Put the reference over the acromion. Stimulate Erbs point. Can compare amplitudes.

Question 26

two entrapment sites for suprascapular nerve

Answer 26

2 entrapment neuropathies of the suprascapular nerve [first branch goes to supraspinatous and the main branch goes to infraspinatous]

1. Suprascapular notch – transverse scapular ligament is the cause, where the entrapment occurs. You will have supraspinatous (abductor) problem and infraspinatous (external rotator) problem

a. Caused by: Cyst or overuse or hypertrophy.
b. Clinically, weakness in external rotation and abduction. Stick EMG needle in there, if there’s enough pressure to cause axonal damage, you’ll have fibs and PSWs in the supraspinatous and the infraspinatous.
c. Recommend to do the infraspinatous first. In reality, it doesn’t matter if it’s at the suprascapular notch or the sphenoglenoid notch. If you have infraspinatous injury, and the rhomboids, deltoid, biceps and paraspinals are ok, you have a suprascapular nerve injury. You can prevent risk from putting the needle into the supraspinatous because you don’t really need to comment if it’s at the suprascapular notch vs the sphenoglenoid notch.

2. Sphenoglenoid notch- sphenoglenoid ligament: as it comes around the medial spine of the scapula. The sphenoglenoid ligament is there as it makes that bend. Two most common reasons for entrapment: cyst and in throwing athletes [pitchers, discus, shotput, javelin throwers]. Infraspinatous affected (external rotator).

a. Weakness in external rotation but normal abduction. Clinically you could probably figure it out without doing EMG.
- Stimulation: Erb’s point: Find SCM, find clavicular component and sterna component. Go just lateral to clavicular component, 1 cm above the clavicle for the cathode, and the anode going superior to that.
- Erbs point for stimulation is not the same as Erb’s palsy or Erb’s point for anatomy

Question 27

course of axillary nerve

Answer 27

– terminal extension of the posterior cord. C5, C6. Sensory distribution is the regimental patch sign [patch in army on side of arm] on deltoid. Motor to deltoid and teres minor.

Question 28

axillary nerve passes through the _________

Answer 28

quadrilateral space

• [ TQ ] entrapment syndrome – compression at the quadrilateral space = quadra angular space
• lateral border: humerus
• superior border – supscapularis and inferior border of teres minor
• medial border – long head of triceps
• inferior border – superior border of teres major

Question 29

most common clinical scenario to give you axillary injury in the quadrilateral space:

Answer 29

anterior shoulder dislocation

• Weakness of abduction
• if entrapment of quadrilateral space of axillary nerve,
• Teres minor spared [TQ]
• deltoid affected

Question 30

how do you perform axillary study

Answer 30

-setup: active over midportion of the deltoid, reference over the distal area of the humerus where the deltoid tendon attaches to the humerus. Reference is between the two and stimulation is at Erb’s point. Basic motor study, can compare amplitudes since it’s a surface pickup. Do the unaffected side first to compare to the affected side.

Question 31

EMG abnormalities with quadrilateral space axillary injury

Answer 31

-EMG: abnormalities: fibs and PSWs of deltoid and teres minor, and other muscles would be ok such as infraspinatous and biceps, brachioradialis (other C5-6 muscles.)

Question 32

course of long thoracic

Answer 32

-branch that comes off proximal. C5,6,7 Wings to heaven. to serratus anterior.

Question 33

how to test for medial winging

Answer 33

long thoracic

This has medial winging on physical exam. From behind, mark spinous process and measure to inferior angle, won’t have lateral displacement side to side. It’ll be sitting where its supposed to be sitting. If you’re right hand dominant or left hand dominant, sometimes the scapula is elevated with respect to the other side. But you want to measure midline to the inferior angle.
-resisted forward flexion, push on a wall: medial scapular winging

Question 34

what type of injuries occur to long thoracic nerve

Answer 34

1. accel/decel injuries (MVC)
2. traction injury - football, wrestling
3. mastectomy
4. thoracotomy
5. brachial amyotrophy/neuritis - pain times 3 days followed by weakness
6. neurologic amyotrophy
7. parsonage turner sydrome

Question 35

set up to test long thoracic nerve

Answer 35

mid axillary line, 5th rib active
reference 8th rib; ground in b/w
stim at erbs point
sternal and clavicular head of SCM - just lateral to this

motor: onset/baseline to peak
EMG - over rib! or inferior angle of the scapular/prone, “push down”

• setup: go along the mid axillary line down to the 5th rib and put the reference 20 mm distal (put the reference over the rib). It’s a motor study. If you get too far down you wont get any branches of the serratus anterior [it looks like fingers]. Put the ground between the stimulation and the pickup. The stimulation point will be erb’s point [not the anatomical erbs point – where C5 and C6 come together].
• The EMG erbs point is: feel for the clavicular head of the SCM and just above the clavicle. Put the cathode in that little space and the anode is superior. Lateral to the clavicular head of the SCM, not in the triangle. When you do the stimulation, you stimulate the entire brachial plexus moving the whole arm. Can use the needle and pickup through the skin into the muscle. If you do the EMG, you have to put your fingers into the intercostals space. Put needle between down to the rib, hit the cortex, back up a little bit and you’re in the serratus. If you can’t palpate the intercostals space, don’t stick the needle in there or Pneumothorax.

motor study really doesn’t help you much. Stick needle in and if fibs and PSWs, you have serratus anterior injury. You’re trying to figure out if the person has voluntary MUAPs, abnormal spontaneous activity. EMG is a better test if you can get your fingers in the intercostals space.

Question 36

medial antebrachial cutaneous nerve comes from _____

study?

Answer 36

-from medial cord

medial forearm sensory. Good to look for lower trunk problem. Sometimes helpful in neurogenic thoracic outlet syndrome.

-Active on medial forearm, with reference 4 cm distal. Measure back 14 cm (sensory study) to stimulate just above the medial epicondyle (at midpoint between biceps tendon and medial epicondyle.

Question 37

Lateral antebrachial cutaneous nerve is from ______

study?

Answer 37

-continuation from musculocutaneous nerve

• lateral forearm.
• active on lateral forearm with reference 4 cm distally. Stimulate in antecubital fossa lateral to biceps tendon

Question 38

Dorsal ulnar cutaneous nerve comes from:

study?

Answer 38

• come of ulnar nerve proximal to the wrist. Supplies sensory to the back of the hand to the DIP joints
• put reference b/t 4th and 5th digit with reference 4 cm distal. Measure back 8-10 cm and stimulate under ulna (slightly proxima and inferior to the ulnar styloid with the hand pronated)
• spared in lesion of ulnar nerve at Guyon’s canal (wrist)
• may be abnormal in most cases of ulnar neuropathy at the elbow

Question 39

how to do radial motor study

Answer 39

pick up over the extensor indicis proprius. Put the pickup over, put the reference on ulnar styloid. Measure back 8 cm and stimulate. Then stimulate lateral to biceps tendon at elbow.

Question 40

musculocutaneous innervates _____

cutaneous?

study?

Answer 40

biceps

lateral antebrachial cutaneous nerve

distal wrist crease to elbow - 1/2 way, place black (radial side)????
Motor: midpoint of biceps (black) 
ref biceps tendon
erbs point stim
ground between

Question 41

study for the facial nerve to nasalis

Answer 41

stim tragus, anode superior (or mastoid process) black on nasalis, under pupil. ref on other side. ground on chin
onset latency, baseline to peak, side to side.

-This is the picture with setup that I use. There are lots of different ways you can do it. We could spend an hour talking about the pathway of the facial nerve and how it gets out. Nasalis muscle directly below the pupil. Pickup on the side you’ll stimulate. Put reference on the opposite side nasalis muscle directly below the pupil. from where you’ll stimulate. Ground on chin. Stimulate in either 1. Below the ear anterior to the mastoid or 2. Directly anterior to the tragus

Question 42

what is the most common cause of facial nerve abnormalities?

Answer 42

MC cause of facial nerve abnormalities (25-35/100,000). Males = females.

57% idiopathic bells palsy
17% trauma
7% herpes zoster
6% CPA tumors
- cerebellar pontine angle
- acoustic neuroma
-Ramsey-hunt herpes zoster (eruption in ext canal) ringing of the ear and facial droop

Can have vertico, hyperacussisus or tinnitus. Alteraltion in taste in anterior 2/3 tongue. pain behind ear, Increased tearing of eye.

Question 43

what is modified schermers test? for facial nerve

Answer 43

not on test

litmus paper and hang off inferior angle of eyelid. Take a swab and irritate their nose. Wait 5 minutes and see how much tears produced from inferior angle to litmus paper. Compare it to the good side. If Bell’s Palsy, less tear production. Significant if the good side is 25% more than the bad side

checks tear development. localizes lesion before geniculate ganglion

Question 44

what is the stapedius test for facial nerve

Answer 44

not on test

• electroacoustic impedence thing and put on the ear. They give you a high decibel sound and calculate whether your stapedius is working.

Question 45

EMG is helpful for prognosis of facial nerve

Compare motor study at day _____ which is the _____

What indicates good prognosis and bad prognosis?

Answer 45

• Dimitri recommends to use the same criteria for bells palsy as the prognostigator which is: [ TQ ] if you have > 90% axonal loss (amplitude) at day 5 [bells palsy or trauma], then poor prognosis.
• [day 5 Wallerian Degeneration takes 4 days to reach peak] Determine side to side, compare good side amplitude to bad side amplitude at day 5. If normal side has amplidute of 10 mV and the symptomatic side is 1mV or nothing, call the ENT.
• if you do the study later than day 5, if there is less than 25% difference in amplitude, then 77% of the people will have good recovery.
• Controversy of steroids in idiopathic Bell’s Palsy. Nickerson always errored on the side of giving the medrol dose pack because if they don’t have a reason to have a contraindication like uncontrolled diabetes, the if it might help them is worth it. Even if statistically they haven’t been able to show that it’s significantly better. Theoretically it takes care of inflammation.

Question 46

______ is the result of reinnervation (collateral sprouting) of the facial nerve to different facial muscles. The classic case is that you close your eye and your mouth goes up. Some of the fibers that go to the obicularis oculi now go to the obicularis oris. It’s not bad or good just know. Common in idiopathic Bell’s palsy.

Answer 46

synkinesis

Question 47

pathology?

involuntary. Contracture of the facial muscle that is ongoing. According to Dimitri, if you stick the needle in a facial muscle and have this, it is MUAPs that completely fill the screen. Its involuntary contraction of motor unit action potentials. (no bursts of MUAPs)

Answer 47

hemifacial spasms - indicates incomplete recovery from significant injury

Question 48

blink reflex is ____ in and ____ out

active goes on:

Reference:

stim over:

ground

Answer 48

5 in 7 out

orbic occuli muscles on both sides

lateral canthus bilaterally

supraorbital nerve (at an angle)

ground on chin

Question 49

blink reflex is equal to what physiologic reflex?

Answer 49

physiologic blink reflex, cornael reflex

Question 50

Which nerve is the problem in the blink reflex?

1. Everything is delayed. The R1 is delayed, R2 on ipsilateral side is delayed and the R2 on the contralateral side is delayed. #1 (shifts right)
   - potentials have 5 and 7 in them. On the side that you do the stimulation on, the R1 is delayed, the R2 ipsilateral is delayed, but the contralateral R2 is normal.

Answer 50

• CN 5 problem, that’s going in. Everything is delayed. The R1 is delayed, R2 on ipsilateral side is delayed and the R2 on the contralateral side is delayed. #1 (shifts right) *Trigeminal neuralgia
• CN 7 problem, getting out problem. Potentials have 5 and 7 in them. On the side that you do the stimulation on, the R1 is delayed, the R2 ipsilateral is delayed, but the contralateral R2 is normal. That tells you for sure that its getting in ok. Its delayed on the output side.