Neurophysiological Diagnosis of Birth

Brachial Plexus Palsy

Dr Grace NgDepartment of PaedPMH

Brachial Plexus Anatomy

Brachial Plexus CordsMedial cord: motor and sensory conduction for median and ulnar nervesPosterior cord: radial sensory and needle EMGLateral cord: musculocutaneous nerve and biceps muscle

Brachial Plexus Anatomy

Evaluation of Brachial Plexus Lesions

Neuroimaging-

preganglionic

spinal root lesion vs

postganglionic brachial plexus lesions -

MRI of nerve root avulsion:

pseudomeningocele-

CT-myelography:

brachial plexus /nerve root lesion

Pseudomeningocele

Pseudomeningocele

ElectromyographyEstablishing the level and extent of plexus involvementIdentifying the presence of a preganglioniclesion or root lesionDefining the nature of the lesion: neurapraxia, axonotmesis or neurotmesis

Preganglionic

Root AvulsionParaspinal muscle denervation: technically challenging in neonatesPreservation of sensory nerve action potential (SNAP) in the absence of any clinical sensory function Difficulties: - hard to determine sensory loss - conjoint preganglionic & postganglionic components - specific cervical level hard to comment due to segmental overlap

DifficultiesWide range of normal amplitudes for CMAPs & SNAPsmedian and ulnar mixed nerve action potentials assessing axonal loss in infantsMotor CMAP amplitude disappear within 4-5 days complete axonal disruption in older childDisappearance of SNAPs up to 10-11 days in adultNeither of these temporal relationships established for young infants

Needle EMGAssess the brachial plexus injury Axonal damage despite relatively normal CMAPsand SNAPsFibrillation potentials/Positive waves 10-14 days in older child similar to adultVery few studies on neonates and infants - positive waves as early as day 4 postinjury: i. the short distance from site of injury ii. immature or poorly myelinated nerves Early denervation & EMG patterns: prenatally occurring lesion

Fibrillation potentials

Positive waves

EMG and Timing of the onset of plexopathy

Early postpartum denervation- a case report: - shoulder dystocia, macrosomic baby with Erb-Klumpke palsy and Horner’s syndrome - D4: no CMAPs or SNAPs but - D4 positive waves in deltoid, biceps, wrist extensors and first dorsal interosseous in D5 - 3 weeks: pseudomeningocele at C6/C7 Acute signs of denervation occur earlier in neonates

EMG and Timing of the onset of plexopathy

Johnson et al: EMGs of 11 infants with OBPP: D4 no fibrillation potentials Clay: 9 week infant with lesion due to osteomyelitis; denervation potentials D10 to D12 Intrauterine onset: peroneal mononeuropathy noted at birth had fibrillation potentials in peroneal innervated muscle at 18 hour of age

Role of EMG in determining prognosis and need for surgical repair

ControversialEMG provides information about nerve pathophysiology: nerve root avulsion pre or post-ganglionic lesion upper versus lower or combined lesionSmall subgroup with OBPP who lack any functional return at 4 mos: EMG showed neurapraxic lesion with conduction block full recovery by 1st birthday with conservative approach

CASE REVIEW (1)M FT VE BW 4.15kgFracture clavicle, reduced R UL movement since birth, good recovery4 mo: Normal nerve conduction study EMG: reinnervation pattern present at right deltoid and biceps muscles

CASE REVIEW (2) F, FT NSD BW 3.75kg Shoulder dystociaLeft Erb’s palsy with poor recoveryNoticed decrease LUL at birth Decreased finger movement which subsequently “has improved”No fracture clavicleSeen at 1mo: LUL in erb’s palsy, no active shoulder mvement, no biceps contraction, wrist, thumb and fingers in flexion, strong finger flexion

Case review (2)2 mo NCS: left median and ulnar nerves showed axonal loss, F-wave mprolonged, sensory nerve study normal EMG: re-innervation at left deltoid and triceps. No MUAP at the left biceps and extensor digitorum

6mo: active deltoid fair, strong triceps contraction, active biceps contraction palpable but no elbow flexion, active finger and wrist extension EMG at 6 mo: Re-innervation present at Lt deltoid, Lt triceps, Lt biceps brachii & Lt extensor digitorum communis

Thank You