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EMG laboratory considerations – Demyelinating neuropathies. Weakness. Shawn Jorgensen Albany Medical Center AAPM&R Annual Assembly 2014. Financial disclosures. None. Possible neuropathy.

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emg laboratory considerations demyelinating neuropathies
EMG laboratory considerations –

Demyelinating neuropathies

Weakness

Shawn Jorgensen

Albany Medical Center

AAPM&R Annual Assembly 2014

possible neuropathy
Possible neuropathy
  • When assessing whether someone presenting with weakness may have a neuropathic cause, main two questions are:
    • Is there any sensory deficit (by history, physical, and EDX)?
    • Time frame (acute/chronic)
possible neuropathy1
Possible neuropathy
  • Sensory deficit
    • Is it real?
      • Is this likely to be related to the process, or an incidental, pre-existing process
      • Time frame
        • coincides with weakness
      • Degree of symptoms or findings
        • Major – more likely related
possible neuropathy2
Possible neuropathy
  • Sensory involvement
    • Acute
      • AIDP
      • AMSAN
    • Chronic
      • CIDP
possible neuropathy3
Possible neuropathy
  • No sensory involvement
    • Acute
      • AMAN
    • Chronic
      • MMN
guillain barre syndrome gbs
Guillain-Barre Syndrome (GBS)
  • Acute, autoimmune, inflammatory neuropathy (polyradiculoneuropathy)
  • Most common cause of acute flaccid paralysis in the world (Ropper 1992)
  • Caused by molecular mimicry
  • 2/3 triggered by preceding infection or other process in the 6 weeks prior (Jacobs 1998)
guillain barre syndrome gbs1
Guillain-Barre Syndrome (GBS)
  • Collection of three different subtypes, all with essentially the same clinical presentation
    • AIDP – acute inflammatory demyelinating polyradiculoneuropathy
    • AMSAN – acute motor and sensory axonal neuropathy
    • AMAN – acute motor axonal neuropathy
guillain barre syndrome gbs2
Guillain-Barre Syndrome (GBS)
  • Typical presentation is acute ascending weakness and sensory complaints
  • Clinical criteria include
    • Weakness in proximal and distal muscles
    • Hyporeflexia
    • Progressing in less than 4 weeks
guillain barre syndrome gbs3
Guillain-Barre Syndrome (GBS)
  • Diagnosis
    • A combination of:
      • Clinical criteria above
      • EDX
      • CSF profile
        • Elevated protein, normal cell count (cytoalbuminic dissociation)
guillain barre syndrome gbs4
Guillain-Barre Syndrome (GBS)
  • Treatment
    • Intravenous immunoglobulin (IVIg)
    • Plasma exchange (PEX)/plasmapheresis
    • NOT steroids
slide12
AIDP
  • Demyelinating form of GBS
  • Sensory and motor
  • 90% of GBS in North America and Europe (Vucic 2009)
slide13
AIDP
  • Electrodiagnostics
    • Patchy, then diffuse, sensorimotor acquired demyelination
      • Sensorimotor
      • Demyelination
        • Acquired
      • Initially patchy, then diffuse
        • Predilection for nerve roots and distal motor terminals initially
slide14
AIDP
  • Electrodiagnostics
    • Demyelination
      • Inherited (uniform)
        • Prolonged motor, sensory, late response latencies
        • Decreased motor, sensory conduction velocities
      • Acquired (segmental)
        • Above, plus
        • Abnormal temporal dispersion
        • Conduction block
slide15
AIDP
  • Electrodiagnostics
    • Acquired demyelination
      • Abnormal temporal dispersion
        • Decreased amplitude
        • Increased duration
        • No change in area
slide16
AIDP
  • Electrodiagnostics
    • Acquired demyelination
      • Conduction block
        • Decreased amplitude
        • No change in duration
        • Drop in area
slide17
AIDP
  • Electrodiagnostics
    • Special considerations
      • “Sural sparing”
        • 2/3 will have a normal sural, abnormal upper limb sensory study (Gordon 2001)
slide18
AIDP
  • Electrodiagnostics
    • Special considerations
      • Early GBS
        • Only 50% meet demyelinating criteria in first week (Albers 1985)
          • May need to study many motor nerves, including proximal stimulation sites to find subtle areas of acquired demyelination
        • Late responses high yield
          • H-reflex abnormal in 97% in first week (Gordon 2001)
slide19
AIDP
  • Electrodiagnostics
    • Special considerations
      • Prognosis
        • CMAP amplitudes (Hadden 1998)
          • Inexcitable – poor prognosis at 2 weeks and beyond
          • Very low amplitude (<20% LLN) – poor prognosis at 2 weeks and beyond
          • Low amplitude (<80% LLN) – not a prognosticator in 2 weeks, poor prognosis at 6
slide20
AIDP
  • EDX assessment of possible AIDP
    • Technique
      • Include multiple motor studies, with multiple motor stimulation sites, loooking for evidence of acquired demyelination
      • Include late responses (especially H-reflex)
    • Interpretation
      • Don’t exclude AIDP if full criteria aren’t met
      • Don’t exclude AIDP if lower limb sensory studies are normal
      • Inexcitable CMAP and amplitude <20%LLN at 2 weeks indicates bad prognosis
amsan
AMSAN
  • Acute motor and sensory axonal neuropathy
  • One of the three subtypes of Guillain-Barre syndrome (GBS)
  • “Axonal GBS”
amsan1
AMSAN
  • Electrodiagnostics
    • Sensorimotor axonopathy
    • Widespread and severe axonopathy, not necessarily length-dependent
    • NCS
      • Motor
        • Decreased amplitudes
      • Sensory
        • Decreased amplitudes
      • Needle EMG
        • Abnormal spontaneous activity
amsan2
AMSAN
  • EDX assessment of AMSAN
    • Technique
      • Utility of NEE before 21 days have elapsed due to distal axonopathy
      • Consider direct motor stimulation to distinguish motor axon loss and muscle denervation from conduction block at the distal motor terminal
    • Interpretation
      • Pay close attention to sensory studies to distinguish from AMAN / other pure motor phenomenon
slide24
AMAN
  • One of the three subtypes of Guillain-Barre syndrome (GBS)
  • Most common variety in China, other parts of the world
  • Pure motor, axonal variant
slide25
AMAN
  • Electrodiagnostics
    • Diffuse, widespread motor axonopathy with sensory sparing!
    • NCS
      • Motor
        • Decreased amplitudes
      • Sensory
        • Normal!!
    • Needle EMG
        • Abnormal spontaneous activity
amsan aman
AMSAN/AMAN
  • EDX assessment of AMSAN/AMAN
    • Technique
      • Utility of NEE before 21 days have elapsed due to distal axonopathy
      • Consider direct motor stimulation to distinguish motor axon loss and muscle denervation from conduction block at the distal motor terminal
    • Interpretation
      • Pay close attention to sensory studies to distinguish from AMAN / other pure motor phenomenon
slide27
CIDP
  • Chronic inflammatory demyelinatingpolyneuropathy
slide28
CIDP
  • Chronic inflammatory demyelinatingpolyneuropathy
  • “MS of the PNS” (Amato 2008)
    • Autoimmune
    • Demyelinating
    • Treatable
    • Can be relapsing / remitting
slide29
CIDP
  • Clinical features
    • Classic presentation
      • Progresses for >=8 weeks
      • Sensory dysfunction
      • Weakness – proximal and distal
      • Hyporeflexic
    • Unusual features
      • Asymmetrical
      • Distal weakness only
slide30
CIDP
  • Laboratory studies
    • CSF
      • Cytoalbuminic dissociation (high protein, normal cells)
    • EDX
      • Diffuse
      • Sensorimotor
      • Acquired demyelination
      • Non length-dependent
      • Secondary axon loss
slide31
CIDP
  • Diagnosis
    • Clinical and EDX criteria
      • Used for research studies
      • >= 17 different sets!
      • Miss treatable patients (low sensitivity)
      • include non-treatable patients (low specificity)
slide32
CIDP
  • Treatment
    • IVIg
    • PEX
    • Can use corticosteroids
    • Maintenance agents (methotrexate, azathioprine)
slide33
CIDP
  • Electrodiagnostic considerations
    • Acquired demyelination
      • Conduction slowing
        • Conduction velocity
          • <80%LLN (CMAP amplitude >80% LLN)
          • <70% LLN (CMAP amplitude <80% LLN)
        • CMAP, F-wave distal latency
          • >125% ULN (CMAP amplitude >80% LLN)
            • 120% for F-waves (Neuropathy association 2003)
          • >150% ULN (CMAP amplitude <80% LLN)
  • Sources: AAN 1991, Saperstein 2001, Neuropathy Association 2003
slide34
CIDP
  • Electrodiagnostic considerations
    • Acquired demyelination
      • Drop CMAP amplitude
        • >20% (AAN 1991)
        • >30% (Neuropathy association 2003)
        • >50% (Saperstein 2001, EFNS/PNS 2010, Koski 2009)
        • >30% probably, >50% definite (Van den bergh 2004)
      • Increase duration
        • >15% (AAN 1991, Neuropathy Association 2003)
        • >30% (Saperstein 2001, Van den bergh 2004, EFNS/PNS 2010)
slide35
CIDP
  • Electrodiagnostic considerations
    • Acquired demyelination
      • Distal CMAP duration (EFNS/PNS 2010)
        • Median >6.6ms
        • Ulnar >6.7ms
        • Fibular >7.6ms
        • Tibial >8.8ms
slide36
CIDP
  • EDX assessment of possible CIDP
    • Technique
      • Include multiple motor studies, with multiple motor stimulation sites, loooking for evidence of acquired demyelination
      • Include late responses (especially F-wave)
    • Interpretation
      • Don’t exclude CIDP if full criteria aren’t met
      • Don’t exclude CIDP if lower limb sensory studies are normal
      • Look for evidence of acquired demyelination, including increased duration of distal CMAP
multifocal motor neuropathy mmn
Multifocal Motor Neuropathy (MMN)
  • Chronic demyelinating neuropathy
  • Involves primarily conduction block
  • ONLY MOTOR FIBERS!!
  • ?Variant of CIDP
multifocal motor neuropathy mmn1
Multifocal Motor Neuropathy (MMN)
  • Clinical features
    • Chronic, progressive weakness
      • Usually distal muscles of upper limbs initially
    • Fasciculations
    • Eventually atrophy
    • In discrete peripheral nerve distributions, non-entrapment sites
    • NO SENSORY SYMPTOMS!!
multifocal motor neuropathy mmn2
Multifocal Motor Neuropathy (MMN)
  • Laboratory features
    • CSF
      • Normal
    • Anti GM-1 antibodies
      • High titers are specific, low non-specific (Kornberg 1994)
multifocal motor neuropathy mmn3
Multifocal Motor Neuropathy (MMN)
  • Treatment
    • IVIg
    • NOT PEX, corticostroids (can worsen)
multifocal motor neuropathy mmn4
Multifocal Motor Neuropathy (MMN)
  • Electrodiagnostic considerations
    • Conduction block (AANEM consensus criteria, Olney 2003)
      • Median, ulnar, fibular across fibular head
        • >50% amplitude, 40% area
      • Tibial, fibular across leg
        • >60% amplitude, 50% area
    • Can be other parameters of demyelination
multifocal motor neuropathy mmn5
Multifocal Motor Neuropathy (MMN)
  • Electrodiagnostic considerations
    • Test asymptomatic sites
      • May show abnormalities (Van Asseldonk 2003)
    • In areas of motor conduction block, test sensory study across same area
multifocal motor neuropathy mmn6
Multifocal Motor Neuropathy (MMN)
  • EDX assessment of possible MMN
    • Technique
      • Test asymptomatic sites
        • May show abnormalities (Van Asseldonk 2003)
      • In areas of motor conduction block, test sensory study across same area
demyelinating neuropathies
Demyelinating neuropathies
  • Conclusions
    • In patients diffuse weakness and “real” sensory complaints, demyelinating neuropathies need to be considered
    • There are many subtleties in the EDX technique and interpretation of demyelinating neuropathies
      • Look for evidence of acquired demyelination
      • Use many motor studies
      • Use late responses
    • Do not dismiss cases that do not meet criteria
references
References

Dyck PJ, Thomas PK. Peripheral Neuropathy. Philadelphia, PA:Elsevier Saunders, 2005.

Jacobs BC, Rothbarth PH, Van derMeche, et al. The spectrum of antecedent infections in Guillain-Barre syndrome. A case-control study. Neurology 1998;51:1110-1115.

Vucic S, Kiernan MC, Cornblath DR. Guillain-Barre syndrome: an update. J ClinNeurosci 2009;16(6):733-741.

Gordon PH, Wilbourne AJ. Early electrodiagnostic findings in Guillain-Barre syndrome. Arch Neurol 2001;58:913-917.

Albers JW, Donofrio PD, McGonagle TK. Sequential electrodiganostic abnormalities in acute inflammatory demyelinatingpolyradiculoneuropathy. Muscle Nerve 1985;8:528-539.

Hadden RD, Cornblath DR, Hughes RA, Zielasek J, Hartung HP, Toyka KV, Swan AV. Electrophysiological classification of Guillain-Barre syndrome: clinical associations and outcome. Plasma Exchange/SandoglobulinGuillain-Barre Syndrome Trial Group. Ann Neurol 1998;44:780-788.

Cornblath DR, Asbury AK, Albers JW, et al. Research criteria for diagnosis of chronic inflammatory demyelinatingpolyneuropathy (CIDP). Neurology 1991;41:617-618.

Saperstein DS, Katz JS, Amato AA, Barohn RJ. Clinical spectrum of chronic acquired demyelinatingpolyneuropathies. Muscle Nerve 2001:24:311-324.

Berger AR, Bradley WG, Brannagan TH, Busis NA, Cros DP, Dalakas MC, Danon MJ, Donofrio P, Engel WK, England JD, Feldman EL, Freeman RL, Kinsella LJ, Lacomis D, Latov N, Menkes DL, Sander HW, Thomas FP, Triggs WJ, Windebank AJ. Wolfe GI; Neuropathy Association, Medical Advisory Committee. Guidelines for the diagnosis and treatment of chronic inflammatory demyelinatingpolyneuropathy. J Peripher Nerve Syst 2003;8:282-284.

references1
References

Koski CL, Baumgarten M, Magder LS, Barohn RJ, Goldetein J, Graves M, Gorson K, Hahn AF, Hughes RA, Katz J, Lewis RA, Parry GJ, van Doorn P, Cornblat DR. Derivation and validation of diagnostic criteria for chronic inflammatory demyelinatingpolyneuropathy. J NeurolSci 2009;277:1-8.

Van den bergh PY, Pieret F. Electrodiagnostic criteria for acute and chronic inflammatory demyelinatingpolyradiculoneuropathy.. Muscle Nerve 2004;29:565-574.

Joint Task Force of the EFNS and the PNS. European Federation of Neurological Societies/Peripheral Nerve Society Guideline on management of chronic inflammatory demyelinatingpolyradiculoneuropathy: report of a joint task force of the European Federation of Neurological Societies and the Peripheral Nerve Society – First Revision. J PeripherNervSyst 2010;15:1-9.

Kornberg AJ, Pestronk A. The clinical and diagnostic role of anti-GM1 antibody testing. Muscle Nerve 1994;17:100-104.

Olney RK, Lewis RA, Putnam TD, Campelione JV Jr, American Association of Electrodiagnostic Medicine. Consensus criteria for the diagnosis of multifocal motor neuropathy. Muscle Nerve 2003:27:117-121.

Van asseldonk JTH, Van den Berg LH, Van den Berg-Vos RM, Wieneke GH, Wokke JHJ, Franssen H. Demyelination and axon loss in multifocal motor neuropathy: distribution and relation to weakness. Brain 2003;126:186-198.