1. Dr Parag Moon
Senior resident, Neurology
GMC, Kota

3.  Motor study -Ipsilateral to most symptomatic side
1. Median nerve- recording APB stimulating wrist
and anticubital fossa.
2. Ulnar nerve- recording ADM stimulating wrist,
below and above elbow.
3. Ulnar nerve-recording FDI stimulating wrist, below
and above elbow.
4. Peroneal nerve-recording EDB stimulating ankle,
below fibular neck,lateral popliteal fossa
5. Tibial nerve-recording AHB stimulating ankle,
popliteal fossa.

4.  Sensory study
1. Median SNAP
2. Ulnar SNAP
3. Radial SNAP
4. Sural SNAP
 Late responses
1. F response
2. H reflexes

5.  Contralateral motor studies done if
predominatly LMN signs without definite UMN
signs.
 Proximal stimulation done if predominatly
LMN signs with normal routine motor study
with abnormal late responses.

6.  Amplitude ratio of APB/ADM and FDI/ADM.
 APB/ADM <0.6
 FDI/ADM <0.9
 If both ratio are abnormal, highly suggestive
of ALS.

7.  Limb muscles
 Sample atleast 3 limbs
 Distal and proximal muscles
 Muscles with different root innervation
 Thoracic spinal segment
 Sample atleast 3 segments
 Avoid T11-T12
 Bulbar muscles
 Atleast one muscle
(tongue,masseter,stercleidomastoid,facial )

8.  ALS defined electrophysiologically by active
denervation and reinervation in three out of
four body segments(craniobulbar, cervical,
thoracic, lumbosacral)
 That cannot be explained by multiple
mononeuropathies or radiculopathies.
 Neuropathic changes -muscles innervated
both by different nerves that share same
myotome and by different myotomes.

9.  Definite- 3 region with UMN and LMN
features
 Probable-2 region with UMN and LMN
features with few UMN features rostral to
LMN
 Possible-1 region with UMN and LMN features
or UMN features in 2 regions

11. 1.Sensory potentials-lateral antebrachial
cutaneous, radial, median, ulnar, medial
antebrachial cutaneous
Compare with unaffected side
2.Median nerve- recording APB stimulating
wrist and anticubital fossa.
3.Ulnar nerve- recording ADM stimulating
wrist, below and above elbow.

12.  In suspected lower trunk/median cord injury
median and ulnar motor study also
stimulated at axilla and Erbs point
 Proximal median conduction study, collision
techniques can be used
 Compare with unaffected side
 Suspected upper/middle trunk lesion-
stimulating Erbs point recording biceps,
triceps, deltoid, supraspinatus, infraspinatus

13. SNAP Cord Trunk
Lateral antebrachial
cutaneous
Lateral Upper
Radial to thumb Posterior Upper
Median to thumb Lateral Upper
Radial to snuffbox Posterior upper/middle
Median to index finger Lateral Upper/middle
Median to middle
finger
Lateral Middle
Median to ring finger Medial middle/lower
Ulnar to ring finger Medial Lower
Ulnar to little finger Medial Lower
Dorsal ulnar
cutaneous
Medial Lower
Medial antebrachial
cutaneous
Medial Lower

14.  Atleast 1 muscle in each peripheral nerve
distribution
 All clinically weak or paralysed muscles
should be examined
 Proximal muscles including paraspinal
muscles
 Upper trunk lesion examine rhomboids
and/or serratus anterior
 If finding equivocal or borderline compare
with other side

15. Nerve Muscles
Median Pronator teres,APB
Anterior interosseous Flexor pollicis longus
Posterior interosseous Extensor indicis proprius, extensor
digitorum communis
Ulnar FDI, flexor digitorum profundus
Radial Extensor carpi radialis,
brachioradialis, triceps
Axillary Deltoid
Musculocutaneous Biceps
Suprascapular Supraspinatus, infraspinatus
Dorsal scapular Rhomboids
Dorsal rami Cervical paraspinal

17.  Routine studies
1. Median motor study recording at APB
stimulating at wrist,anticubital fossa
2. Ulnar motor study recording at ADM
stimulating at wrist, below and above elbow
3. Median and ulnar F waves
4. Median sensory recording digit2 or 3
5. Ulnar sensory recording digit 5
6. Radial sensory recording snuffbox

18. Highly suggestive of CTS if
 Median study shows prolonged distal motor
and sensory latencies
 Prolonged minimum F wave latencies
 Median CMAP and SNAP amplitudes may be
reduced
 Ulnar motor, sensory and F wave studies are
normal
 Radial sensory response is normal.

19. 1. Median vs ulnar palm to wrist mixed nerve
study
 Stimulating median nerve in palm on line
connecting median nerve in middle of wrist
to web space between 2 and 3 digit
 Ulnar nerve stimulated in palm on line
connecting ulnar nerve to web space
between 4 and 5 digit
 Recording electrodes at median and ulnar
nerve
 Distance between electrodes=8 cm

20.  Antidromic technique
 Recording ring electrodes placed over 4th
digit
 G1 over metacarpophalengeal joint
 G2 over distal interphalengeal joint
 Median and ulnar nerves stimulated one at a
time at wrist
 Difference in onset or peak latencies noted

21.  Active electrode(G1) slightly distal and lateral
to midpoint of third metacarpal
 Reference electrode over proximal
interphalengeal joint of 2nd digit
 Stimulation at wrist for median and ulnar
nerve
 Difference between distal latencies is
compared

22.  Begins 4 cm proximal to distal wrist crease,
continues 6cm distal to wrist crease
 Segmental stimulation at 1 cm increments
 For each 1 cm increment latency usually
increases 0.2 to 0.3ms
 Limitation- difficulty in stimulation just distal
to wrist crease

23.  G1 over metacarpophalengeal joint of 1st digit
 G2 over interphalengeal joint of 1st digit
 Stimulation at wrist for median and radial
nerve equidistant from recording electrodes
 Difference between latencies noted

24.  G1 and G2 placed at proximal and distal
interphalengeal joint of 3rd digit
 Median nerve stimulated at wrist
 Stimulated at palm at half wrist to digit
distance
 Wrist to palm conduction velocity calculated
 P to D CV X W to D CV/2P X to D CV -W to D
CV
 Reversal seen in CTS

25. 1. Abductor pollisis brevis
2. Atleast 2 C6-C7 innervated muscle
(pronator teres,flexor carpi radialis, triceps
brachi, extensor digitorum communis)
*APB sudy is painful. So best not studied first

26. If APB is abnormal
 Atleast 1 proximal median innervated muscle
(flexor carpi radialis, pronator teres, flexor
pollicis longus) to exclude proximal
neuropathy
 Atleast 2 non median lower trunk/C8-T1
innervated muscle(FDI, extensor indicis
proprius)

28. 1. Posterior interosseous nerve
2. Radial nerve at spiral grove
3. Radial nerve in axilla
4. Posterior cord of brachial plexus
5. C7 radiculopathy

29. 1. Radial motor study-recording extensor
indicis proprius stimulating forearm, elbow,
below and above spiral grove, bilaterally
2. Ulnar motor study-recording ADM
stimulating wrist below and above groove in
flexed elbow position
3. Median motor study-recording APB
recording wrist, anticubital fossa

30. 4. Median and ulnar F waves
5. Superficial radial sensory study-recording
over extensor tendons of thumb, stimulating
forearm, bilaterally
6. Ulnar sensory study-recording 5th digit
7. Median sensory study-recording 2nd or 3rd
digit

31. 1. Posterior interosseous neuropathy(axonal)-
normal superficial radial sensory SNAP, low
amplitude distal CMAP
2. Posterior interosseous neuropathy
(demyelinating)-normal SNAP, conduction
block between forearm and elbow,normal
CMAP amplitude
3. Radial neuropathy in spiral grove(axonal)-
reduced SNAP, reduced CMAP amplitude

32. 4. Radial neuropathy at spiral grove
(demyelinating)-normal SNAP, conduction
block at spiral groove
5. Radial neuropathy in axilla(axonal)-reduced
SNAP, low amplitude CMAP
6. Radial neuropathy at axilla (demyelinating)-
normal SNAP, normal motor study above
spiral groove
7. Superficial radial sensory neuropathy-
reduced SNAP, normal radial motor study

33.  Atleast 2 posterior interosseous innervated
muscles(Extensor indicis proprius, extensor
carpi ulnaris, extensor digitorum communis)
 Atleast 1 radial innervated muscle proximal
to bifurcation of main radial nerve distal to
spiral groove(brachioradialis,extensor carpi
radialis)
 Atleast 1 radial innervated muscle proximal
to spiral groove(triceps, anconeus)

34.  Atleast 1 non radial posterior cord innervated
muscle(deltoid, lattismus dorsi)
 Atleast 2 non radial C7 innervated
muscle(flexor carpi radialis, pronator teres,
flexor digitorum sublimis, cervical paraspinal
muscles)
*Avoid supinator muscle

36. 1. Deep peroneal nerve
2. Common peroneal nerve
3. Sciatic nerve
4. Lumbosacral plexus
5. L5 radiculopathy

37. Routine studies
1. Peroneal motor study- recording extensor
digitorum brevis stimulating ankle, below
fibular head, lateral popliteal fossa
2. No conduction block or focal slowing at
fibular head then recording at Tibialis
anterior stimulating below fibular head,
lateral popliteal fossa

38. 2. Tibial motor study recording abductor
hallucis brevis stimulating medial ankle,
popliteal fossa
3. Superficial peroneal sensory study
stimulating lateral calf recording lateral ankle
4. Sural sensory study stimulating calf
recording posterior ankle
5. Tibial and peroneal F responses

39. Routine study
1. Atleast 2 muscles innervated by deep
peroneal nerve (eg. Tibialis anterior,
extensor hallucis longus)
2. Atleast 1 muscle in superficial peroneal
nerve( peroneus longus, brevis
3. Tibialis posterior and atleast 1 other tibial
innervated muscle(medial gastrocnemius,
soleus, flexor digitorum longus)
4. Short head of biceps femoris

40.  If short head of biceps femoris or any tibial
innervated muscle is abnormal then EMG
study of other sciatic muscles, gluteal,
paraspinal muscles performed

41. Thank u

42. 1. Electromyography and neuromuscular
disorders: D. Preston, B Shapiro:2013
Elsevier Inc
2. American association of Neuromuscular and
electrodiagnostic medicine;Practice
guidelines 2012