Electrophysiology Of Guillain-Barre Syndrome Dr. Ahsan Moosa Department Of Neurology Sree Chitra Tirunal Institute for Medical Sciences & Technology Trivandrum, Kerala, India

Guillain-Barre Syndrome Popularly known as a demyelinating disorder [AIDP] Also has other variants A cute motor axonal neuropathy –AMAN Acute motor sensory axonal neuropathy-AMSAN Miller Fisher syndrome Others

Popularly known as a demyelinating disorder [AIDP]

Also has other variants

A cute motor axonal neuropathy –AMAN

Acute motor sensory axonal neuropathy-AMSAN

Miller Fisher syndrome

Others

Diagnosis Electro-clinical diagnosis Well established clinical criteria- Asbury’s ENMG study should always be done Confirm the diagnosis Alternate diagnosis Electrophysiological classification Prognosticate

Electro-clinical diagnosis

Well established clinical criteria- Asbury’s

ENMG study should always be done

Confirm the diagnosis

Alternate diagnosis

Electrophysiological classification

Prognosticate

Parameters in ENMG Distal latency Nerve conduction velocity (NCV) CMAP amplitude CMAP duration F-waves Sensory conduction studies H-reflex Needle EMG

Distal latency

Nerve conduction velocity (NCV)

CMAP amplitude

CMAP duration

F-waves

Sensory conduction studies

H-reflex

Needle EMG

DL- latency from stimulus onset to appearance of CMAP Depends on NCV of distal segment Neuromuscular Jn. And muscle membrane transit time Abnormal ? > 125 % ULN if CMAP amplitude is normal > 150% ULN if CMAP amplitude is < 80% Distal Latency

DL- latency from stimulus onset to appearance of CMAP

Depends on

NCV of distal segment

Neuromuscular Jn. And muscle membrane transit time

Abnormal ?

> 125 % ULN if CMAP amplitude is normal

> 150% ULN if CMAP amplitude is < 80%

Nerve Conduction Velocity Slowing of NCV is one of the hallmarks of demyelinating neuropathy Normal UL > 50 m/s LL > 40 m/s Abnormal? <80% of LLN if CMAP >80% of LLN <70% of LLN if CMAP < 80% of LLN

Slowing of NCV is one of the hallmarks of demyelinating neuropathy

Normal

UL > 50 m/s

LL > 40 m/s

Abnormal?

<80% of LLN if CMAP >80% of LLN

<70% of LLN if CMAP < 80% of LLN

CMAP Amplitude Amplitude depends on the no. Of “ functioning ” motor axons with “ secure conduction ” So, Low amplitude can occur with both demyelination and axonopathy Amplitude < 20% of normal  axonopathic if there are no features of demyelination

Amplitude depends on the no. Of “ functioning ” motor axons with “ secure conduction ”

So, Low amplitude can occur with both demyelination and axonopathy

Amplitude < 20% of normal  axonopathic if there are no features of demyelination

CMAP Duration Depend on the range of conduction velocities of conducting fibers Abnormal ? >15% increase in the negative peak duration of the proximal evoked CMAP compared to distal CMAP -called Temporal Dispersion CMAP area: Amplitude X duration

Depend on the range of conduction velocities of conducting fibers

Abnormal ?

>15% increase in the negative peak duration of the proximal evoked CMAP compared to distal CMAP -called Temporal Dispersion

CMAP area: Amplitude X duration

Conduction Block Difference of CMAP amplitude between distal and proximal stimulation Value ? consensus 20%, 30%, 50% 60% for Tibial

Difference of CMAP amplitude between distal and proximal stimulation

Value ? consensus

20%, 30%, 50%

60% for Tibial

Conduction Block Amplitude fall >30% in proximal stimulation compared to distal irrespective of change in the duration [Temporal dispersion] Both TD and CB signify the same process-i.e., segmental demyelination

Amplitude fall >30% in proximal stimulation compared to distal irrespective of change in the duration [Temporal dispersion]

Both TD and CB signify the same process-i.e., segmental demyelination

F-waves Antodromic impulse from the motor nerve  proximal nerve  root  AHC  motor nerve  elicits a delayed small action potential called F-wave When Distal segment study is normal, abnormal F-wave indicate proximal dysfunction Abnormal ? >120% of ULN if amp >20% LLN or in-excitable

Antodromic impulse from the motor nerve  proximal nerve  root  AHC  motor nerve  elicits a delayed small action potential called F-wave

When Distal segment study is normal, abnormal F-wave indicate proximal dysfunction

Abnormal ? >120% of ULN if amp >20% LLN or in-excitable

Abnormal F-wave

H-reflex Electrophysiological correlate of areflexia Monosynaptic spinal reflex Sensory N Dorsal Root Synapse Motor root Motor nerve H Reflex Abnormal ? Absence of H-reflex Almost an universal finding in early GBS

Electrophysiological correlate of areflexia

Monosynaptic spinal reflex

Sensory N Dorsal Root Synapse Motor root Motor nerve H Reflex

Abnormal ?

Absence of H-reflex

Almost an universal finding in early GBS

Most proximal and most distal segments are affected early NC Velocities are often normal early Motor NCV slowest-3rd week Sensory NCV slowest-4th week Change in NCV - often the last to recover When patient improves, NCV may paradoxically slow Evolution Of ENMG Features

Most proximal and most distal segments are affected early

NC Velocities are often normal early

Motor NCV slowest-3rd week

Sensory NCV slowest-4th week

Change in NCV - often the last to recover

When patient improves, NCV may paradoxically slow

Electrodiagnostic Criteria (AIDP) 120-150 >150 >120 >120 % >125 >120 F-wav 56% 63% 58% 21% 37% 72% 43 pts 30 - 30 20% 30 30 TD 30 30 30 20% 30 30 CB >125 >150 >110 >125 % >115 >110 DL <80 (70) <70 <90 (85) 80% (70%) <90 (80) <95 (85) CV (Low amp) Italy group Dutchgroup Ho et al Cornblath ( CIDP) Albers & Kelly Albers et al

Criteria For Electrophysiological Classification Primary Demyelinating At least 1 of the following in 2 nerves or 2 in 1 nerve if others are of low amplitude/ in-excitable MCV <90% LLN (85% if amp. <50% LLN) DML >110% ULN (120% if amp. < 20%LLN) C.Block 50% fall proximally if CMAP >20% LLN F-latency >120% ULN

Primary Demyelinating

At least 1 of the following in 2 nerves or 2 in 1 nerve if others are of low amplitude/ in-excitable

MCV <90% LLN (85% if amp. <50% LLN)

DML >110% ULN (120% if amp. < 20%LLN)

C.Block 50% fall proximally if CMAP >20% LLN

F-latency >120% ULN

Classification contd… Primary Axonal [AMAN/AMSAN] None of the features of demyelination in any nerve Distal CMAP amp <80% LLN in at least 2 nerves Inexcitable Distal CMAP absent in all nerves OR present in only 1 nerve with amp.<10%LLN

Primary Axonal [AMAN/AMSAN]

None of the features of demyelination in any nerve

Distal CMAP amp <80% LLN in at least 2 nerves

Inexcitable

Distal CMAP absent in all nerves

OR present in only 1 nerve with amp.<10%LLN

Classification contd… Equivocal Does not exactly fit criteria for any group Follow up studies will help in reclassifying the Inexcitable and Equivocal group into axonal/demyelinating [GBS study Group. Ann Neurol 1998]

Equivocal

Does not exactly fit criteria for any group

Follow up studies will help in reclassifying the Inexcitable and Equivocal group into axonal/demyelinating

[GBS study Group. Ann Neurol 1998]

Early diagnosis is important CSF is often normal in early stages Gordon & Wilbourn, 2001 31 patients studied within 7 days H-reflex absent 97% Absent or Low amplitude SNAPs in UE-61% Abnormal Median & Normal Sural SNAP 48% Abnormal F-waves 84% Early GBS ENMG Features

Early diagnosis is important

CSF is often normal in early stages

Gordon & Wilbourn, 2001

31 patients studied within 7 days

H-reflex absent 97%

Absent or Low amplitude SNAPs in UE-61%

Abnormal Median & Normal Sural SNAP 48%

Abnormal F-waves 84%

Early GBS contd… Prolonged DL 65% Low CMAP amp 71% Temporal dispersion 58% Conduction Block 13% Slowed Motor conduction velocity 52% Definitive diagnosis in 55% usually by 5 th day [ Gordon et al . Arch Neurol 2001;58:913]

Prolonged DL 65%

Low CMAP amp 71%

Temporal dispersion 58%

Conduction Block 13%

Slowed Motor conduction velocity 52%

Definitive diagnosis in 55% usually by 5 th day

[ Gordon et al . Arch Neurol 2001;58:913]

AMNS Responses Median: Wrist-finger Sural: Calf-Lat mall In GBS most distal and prox. Segments are affected early In true sense AMNS is an artifactual finding

Median: Wrist-finger

Sural: Calf-Lat mall

In GBS most distal and prox. Segments are affected early

In true sense AMNS is an artifactual finding

Isolated Absent F-waves in GBS Kuwabara et al. studied 62 pts (Japan) 12 had Isolated F-wave absence Follow up conduction revealed 2 patterns Rapid restoration of normal F-waves ! Normal parameters in other sites too [ Rapid clinical recovery ] Evolution into AMAN!!

Kuwabara et al. studied 62 pts (Japan)

12 had Isolated F-wave absence

Follow up conduction revealed 2 patterns

Rapid restoration of normal F-waves ! Normal parameters in other sites too [ Rapid clinical recovery ]

Evolution into AMAN!!

Pathophysiology of Isolated Absent F-wave in GBS Demyelinative conduction block in proximal segment Acute axonopathy in proximal segment Reversible conduction failure at nodes of Raniver (AMAN) Impaired excitability [Kuwabara JNNP 2000;68:191]

Demyelinative conduction block in proximal segment

Acute axonopathy in proximal segment

Reversible conduction failure at nodes of Raniver (AMAN)

Impaired excitability

[Kuwabara JNNP 2000;68:191]

Inexcitable? Nerve may have conducting axons but inexcitable by conventional stimulation

Nerve may have conducting axons but inexcitable by conventional stimulation

Preferably done in all cases Denervation features may occur as early as first week of illness Indicate axonopathic process EMG

Preferably done in all cases

Denervation features may occur as early as first week of illness

Indicate axonopathic process

Sensory Axonal loss Reduced SNAPs Can be completely normal Motor: Usually Normal F-waves: Prolonged; Dispersed; Absent Serial conduction studies- more useful Miller Fisher Syndrome

Sensory

Axonal loss

Reduced SNAPs

Can be completely normal

Motor: Usually Normal

F-waves: Prolonged; Dispersed; Absent

Serial conduction studies- more useful

CMAP amplitude 0-20% LLN -poor outcome Other parameters-do not predict Recurrent GBS Vs CIDP? No electrophysiological features Rely more on clinical features A documented normal study between relapses may help Prognostic Factors

CMAP amplitude 0-20% LLN -poor outcome

Other parameters-do not predict

Recurrent GBS Vs CIDP?

No electrophysiological features

Rely more on clinical features

A documented normal study between relapses may help

Electro-clinical diagnosis No universally accepted EP criteria Majority 56-87% -AIDP Early GBS - normal study unlikely with significant deficit Axonal GBS diagnosed in the absence of demyelination features Low CMAP –only prognostic indicator Conclusion

Electro-clinical diagnosis

No universally accepted EP criteria

Majority 56-87% -AIDP

Early GBS - normal study unlikely with significant deficit

Axonal GBS diagnosed in the absence of demyelination features

Low CMAP –only prognostic indicator

Thank you

Thank you