ENMG of Brachial Plexus F Wang To exclude

ENMG of Brachial Plexus F. Wang To exclude To localize To assess severity

Easy diagnosis ? 1. Post- ganglionic multitroncular mononeuropathy 2. Sensory and motor neuropathy or pure motor neuropathy (Parsonage & Turner, MMN) 3. Axonal or demyelinating neuropathy (dysimmune neuropathies) 4. SNAP/CMAP : absent or reduced in amplitude MCV & distal latency : usually normal Erb’s point stimulation : sometimes prolonged latency or conduction block (MMN, plexopathy due to radiations) F wave : prolonged if demyelination in C 7 -D 1 territory EMG : acute, subacute or chronic neurogenic traces

Tricky diagnosis ? The main difficulty is related to : - Anatomy

Three questions 1. Pre- or post-ganglionic lesion ? 2. Spinal nerve or plexus ? 3. Trunk or cord ? or SUPER root or SUPER nerve ? And then you realized that things are more complicated…

Pre- or post-ganglionic lesion ? 1. Paravertebral muscles 2. SNAPs There is not sensory axonal degeneration in the case of pre -ganglionic lesion, even if this nervous lesion is complete. • 1 or 2 cm out of • the median line At the intervertebral space

Pre- or post-ganglionic lesion ? SNAP s Radial nerve – Posterior cord – Upper/Middle trunks – C 6(C 7) Thumb – Radial nerve – posterior cord – upper trunk – C 6 LABC nerve – Lateral cord – Upper trunk – C 6 MABC – C 8 TPSnerve – Medial cord – Lower trunk TSAE Thumb Upper trunk – C 6 TPM– Median nerve – Lateral cord –TSAE 3 rd. TPI finger – Median nerve – Lateral cord. TSAI – Middle trunk – C 7 5 th finger – Ulnar nerve – Medial cord – Lower trunk – C 8 Right/Left difference in amplitude : ≥ 50% is abnormal

Spinal nerve or plexus ? Ventral rami Dorsal scapular nerve Nerve to subclavius muscle Long thoracic nerve

Spinal nerve or plexus ? 1. Long thoracic nerve (C 5, C 6, C 7) : serratus anterior 2. Dorsal scapular nerve (C 5) : rhomboid minor and major and levator scapulae 3. Nerve to subclavius muscle (C 5, C 6)

Trunks or Cords ? Anatomical classification of lesions • Trunks : supraclavicular and pass between scalenus medius and scalenus anterior • Cords : infraclavicular • Divisions (between trunks & cords) : retroclavicular

SUPER root or SUPER nerve ? Simplified view Upper trunk TPS Middle trunk TPM Lower trunk TPI C 5 C 6 C 7 C 8 T 1 Lateral cord TSAE Posterior cord TSP Medial cord TSAI Musculocutaneous Median (C 6 -C 7) Radial Axillary Ulnar Median (C 8 -T 1) Medial antebrachial cutaneous

Upper trunk C 5 + C 6 C 5 Suprascapular nerve C 6

Upper trunk C 5 + C 6 1. C 5 & C 6 post-ganglionic lesion 2. With suprascapular nerve lesion (most often) 3. Without involvement of long thoracic & dorsal scapular nerves

Upper trunk C 5 + C 6 1. C 5 mot. : deltoid (CMAP) 2. C 6 mot. : biceps (CMAP, T), ext. carpi rad. brevis, pronator teres 3. C 5/C 6 SNAPs: radial, median/R 1 lateral antebrachial cutaneous 4. Suprascapular nerve (C 5, C 6) 5. Tendon reflex: biceps & brachioradialis

Upper trunk lesions C 5 + C 6 1. Moto crash 2. Obstetrical trauma 3. Parsonage & Turner 4. Infiltrative plexopathy 5. Rucksack paralysis 6. “Burner syndrome (sport trauma) 7. Post-anesthesia 8. Infection : Lyme 9. Vasculitis 10. Heroin

Upper trunk lesions C 5 + C 6 Schwannome

Lateral cord musculocutaneous + median (C 6 C 7) nerves Lateral pectoral nerve Musculocutaneous nerve Median nerve

Lateral cord musculocutaneous + median (C 6 C 7) nerves 1. Musculocutaneous mot. : biceps (CMAP), brachialis 2. Median (C 6 C 7) mot: pronator teres, flexor carpi radialis (H) 3. Median R 1 -R 4/lateral antebrachial cutaneous SNAPs 4. Lateral pectoral nerve : pectoralis major 5. Tendon reflex: biceps

Middle trunk C 7

Middle trunk C 7 1. C 7 post-ganglionic lesion

Middle trunk C 7 1. C 7 mot. : triceps (T), flexor carpi radialis (H), extensor digitorum, anconeus (CMAP/F) 2. C 7 SNAPs: median/R 2+R 3, radial, PABC 3. Tendon reflex: triceps

Posterior cord radial + axillary nerves Axillary Radial Axillary nerve Thoracodorsal nerve Lower subscapular nerve Radial nerve

Posterior cord radial + axillary nerves 1. Radial mot: triceps (T), extensor digitorum, extensor indicis, ECU(CMAP), anconeus (CMAP/F) 2. Axillary mot: deltoid (CMAP), teres minor 3. Thoracodorsal mot: latissimus dorsi 4. Lower subscapular mot: teres major, (subscapularis) 5. Radial SNAP 6. Triceps and brachoradialis reflexes are abnormal

Posterior cord lesions radial + axillary nerves 1. Humeral head fracture/luxation 2. Supra-clavicular wounds

Lower trunk C 8 + D 1 C 8 D 1 Medial pectoral nerve Medial antebrachial cutaneous nerve Medial brachial cutaneous nerve

Lower trunk C 8 + D 1 1. C 8 & D 1 post-ganglionic lesion 2. With medial brachial & antebrachial cutaneous With medial pectoral Reminder : APB & medial brachial cutaneous D 1 > C 8 ulnar nerve C 8 > D 1

Lower trunk C 8 + D 1 1. C 8/D 1 mot. : APB (CMAP/F), ADM (CMAP/F) Interosseous I, extensor indicis, pectoralis minor & major (sternocostal portion) 2. C 8/D 1 SNAPs: ulnar/R 4+R 5, medial brachial & antebrachial cutaneous 3. No reflex abnormalities

Lower trunk C 8 + D 1 1 2 3 4 Pectoralis major 1 Clavicula Nipple anterior axillary line Pectoralis major (clavicular part, C 5 C 6) 5 Pectoralis major (sternocostal part, C 7 C 8) 6 Pectoralis minor (C 7 C 8) Pectoralis minor 1 4 6 5 2 3 3 Right TOS

Medial cord Ulnar + median (C 8 D 1) nerves Medial pectoral nerve Median nerve Ulnar nerve Medial antebrachial cutaneous nerve Medial brachial cutaneous nerve

Medial cord Ulnar + median (C 8 D 1) nerves 1. Ulnar & median (C 8 D 1) 2. With medial brachial & antebrachial cutaneous (sometimes) With medial pectoralis nerve (sometimes) 3. Without C 8 radial muscles

Medial cord Ulnar + median (C 8 D 1) nerves 1. C 8/D 1 mot. : APB (CMAP/F), ADM (CMAP/F) Interosseous I, pectoralis minor 2. C 8/D 1 SNAPs: ulnar/R 4+R 5, medial brachial & antebrachial cutaneous 3. No reflex abnormalities

Lower trunk or medial cord lesions 1. TOS 2. Pancoast Tobias 3. Metastatic 4. Neurofibroma Schwannoma Meningioma 5. Trauma in abd. 6. Post-sternotomy 7. Radiotherapy 8. Dys. neuropathy

Lower trunk or medial cord lesions Dys. neuropathy

Lower trunk or medial cord lesions Non small-cell lung tumor

Upper T Middle T Lower T Lateral C Posterior C Medial C 1. Deltoid (C 5 C 6) : CMAP, EMG _ _ _ 2. Infraspinatus (C 5 C 6) : CMAP (needle), EMG _ _ _ 3. Biceps (C 5 C 6) : CMAP, T, EMG + 4. Pronator teres (C 6 C 7) : EMG + _ _ _ _ + _ _ 5. Flexor carpi radialis (C 6 C 7) : H, EMG 6. Triceps (C 6 C 7 C 8) : T, EMG 7. Extensor indicis (C 7 C 8 D 1) : EMG _ _ 8. Abductor pollicis brevis (C 8 D 1) : CMAP, F, EMG _ _ 9. Abductor digiti minimi (C 8 D 1) : CMAP, F, EMG _ _ + 12. Teres major (C 5 C 6 C 7) : EMG _ _ + _ 1. Radial (C 6 C 7) : SNAP _ _ 10. Pectoralis major (C 5 C 6 C 7 C 8) : EMG 11. Pectoralis minor (C 7 C 8) : EMG _ _ 2. R 1/median (C 6) : SNAP + _ _ 3. R 3/median (C 7) : SNAP _ + _ _ 4. Medial antebrachial cut. (D 1) : SNAP _ _ 5. R 5/ulnar (C 8) : SNAP _ _ + 6. Lateral antebrachial cut. (C 6) : SNAP + _ _

Simplified view Lesion Motor Sensory Tendon Reflex LOWER TRUNK C 8 + D 1 APB-ADM MABC Extensor indicis R 5 No reflex abnormalities MEDIAL CORD Ulnar + Median C 8 D 1 APB-ADM MABC R 5 No reflex abnormalities UPPER TRUNK C 5 + C 6 Deltoid Infraspinatus Radial R 1/LABC Biceps Brachioradialis POSTERIOR CORD Radial + Axillary Deltoid Radial only Extensor indicis Brachioradialis Triceps MIDDLE TRUNK C 7 Triceps FCR Radial R 3 Triceps only LATERAL CORD Musculocutaneous + Median C 6 C 7 Biceps Pronator teres Median (R 1 -R 4) Biceps only LABC

The simplest view 1. Inferior plexus : hand intrinsic muscles APB, ADM, MABC, R 5 with EI => LT without EI => MC 2. Superior plexus : elbow and wrist flexion BB, FCR, PT with D and radial SNAP => UT without D, with median SNAP => LC 3. Middle/posterior plexus : elbow and wrist extension TB, radial SNAP without EI => MT with D => PC

Thanks E Fournier JF Camdessanché AL Derelle et al A Echaniz-Laguna HW van Es et al MI Vargas et al http: //www. rad. washington. edu http: //enmgblogspot. com