Know what your EMG might miss!
 Speakers
• Tony Chiodo, MD
• Timothy Dillingham, MD
• W. David Arnold, MD
• Shawn Jorgensen, MD
 Blind
spots
 “Electrodiagnostic
Normal study…”
impression:
 “Electrodiagnostic
impression:
No generalized peripheral neuropathy…”
 Patient #1
• 29 year old female with one week of numbness,
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prickly sensation and pain in the feet, progressing to
the calves, later in the hands, lips, mouth.
Four days ago began having difficulty going up
stairs, getting out of chairs, getting her legs in her
pants, getting her arms overhead
Balancing is worsening
No oculobulbar, bowel or bladder symptoms
2 weeks prior saw PCP, diagnosed with a URI, given
a tetanus and influenza vaccine
 Patient #1
• Physical examination
 CN – normal
 Motor
 4/5 elbow extension, DIP flexion, ankle dorsiflexion, toe
extension, 5-/5 hip flexion
 Functionally could not get out of chair without using her arms
 Sensory
 Pinprick, vibration normal
 Romberg positive
 MSR
 1+ brachioradialis, others areflexic
 Patient
#1
• Electrodiagnostics
 Motor – normal except
 Left median to APB: decreased amplitude prox + distally
 Right fibular: 25% amplitude loss proximal to distal, decreased CV
 Left tibial: prolonged DML, decreased CV
 Sensory – normal except
 Right sural, bilateral medial dorsal cutaneous prolonged PL
 Late responses
 F-waves – decreased amplitude ulnar bilaterally, o/w normal
 H-reflex – absent bilaterally
 NEE
 Left upper, lower, paraspinals normal
 Patient
#1
• “Electrodiagnostic Impression:
Abnormal study. Mild generalized sensorimotor
neuropathy.”
 Guillain-Barre
Syndrome
• Acute, autoimmune neuropathy
• Clinically presents with acutely progressive sensory
dysfunction and weakness, usually in an ascending
pattern, progressing for less that four weeks
• Exam should demonstrate sensory loss (particularly
large fiber), weakness of both proximal and distal
muscles, and hyporeflexia
 Guillain-Barre
Syndrome
• EMG findings in GBS
 Sensorimotor
 Non length-dependent
 Acquired demyelination
 Abnormal temporal dispersion
 Conduction block
 Guillain-Barre
Syndrome
• EMG findings in early GBS
 Demyelination (Albers 1985)
 Week 1 - 50% meet full demyelinating criteria
 Week 5 – 87% meet criteria
 Late Responses – week 1 (Gordon 2001)
 97% abnormal H reflexes (88% day 4)
 87% abnormal F waves
 Guillain-Barre
Syndrome
• Non length-dependence
 Abnormal upper limb/normal lower limb
 “Sural sparing”
 50% of patients by week 1 (Gordon 2001)
 EMG
BLIND SPOTS!!
• Guillain-Barre syndrome
 Early normal/minimally abnormal EDX
 Look for late responses
 Normal sural
 Look for abnormal upper limb
 Patient
#1 – revised impression
• “Electrodiagnostic Impression:
Abnormal study. Mild generalized peripheral
neuropathy; cannot exclude early AIDP
• Clinical Impression:
Monitor closely for worsening neurological
symptoms and repeat NCS in one week if symptoms
don’t improve or worsen. Consider consultation
with a neuromuscular specialist.”
 Patient
#2
• 67 year old patient with slowly progressive
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ambulatory decline
Thinks it has been going on for 3 years
Feels weakness is in his legs and has some in arms as
well
When asked, notes numbness in feet and hands
No oculobulbar or sphincter complaints
PMH: DM2, mild CHF
 Patient #2
• Physical examination
 Cranial nerves - normal
 Motor – normal excepts
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3+/5 right, 4/5 left arm abduction
4/5 finger abduction
2/5 hip flexion
4/5 knee extension
4/5 right, 3-/5 left ankle dorsiflexion
 MSR
 Trace in uppers, 0 in lowers
 Sensation
 Absent vibration at ankles
 Pinprick normal
 Patient
#2
• Electrodiagnostics
 Motor NCS
 Diffusely diminished conduction velocities
 Dramatic temporal dispersion across the forearm on right ulnar
motor
 Lower limb studies unobtainable
 Sensory NCS
 Lowers unobtainable
 Ulnar sensory low amplitude
 Needle EMG
 Abnormal spontaneous activity, large amplitude MUAP in distal LE
muscles
 Patient
#2
• “Electrodiagnostic Impression:
Abnormal study. Generalized sensorimotor
neuropathy with axonal and demyelinating
features.”
 CIDP
• Chronic inflammatory demyelinating
polyradiculoneuropathy
• MS of the PNS (Amato 2009)
 Autoimmune
 demyelinating
 often relapsing/remitting course, other progressive
• More common than you think!
 Of those with cryptogenic neuropathy referred for
intensive referral center investigation, about 1/5 have
CIDP (and are treatable) (Dyck 1981)
 CIDP
• Clinical features
 Progresses for 8 weeks or more
 Weakness classically proximal and distal, symmetrical
 Hyporeflexia
 Sensory complaints
• Lab features
 EDX – diffuse sensorimotor acquired demyelination
(similar to AIDP)
 CSF – cytoalbuminic dissociation
 CIDP
• Atypical forms
 Not all meet even basic clinical features
 Asymmetrical or pure sensory in 50% cases (Breiner 2014)
 CIDP
• Criteria (AAN)
 Clinical
 Motor and or sensory loss in >1 limb
 Hyporeflexic
 Over 2 months
 Electrodiagnostic
 3 out of 4
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CB/TD in >=1 nerve
CV decreased in >=2 nerves
DL prolonged in >=2 nerves
FW prolonged in >=2 nerves
 CIDP
• Criteria
 At least 15!
 No consensus
 Sensitivities range from 11-91% (Breiner 2014)
 False negatives – treatable patients missed
 Specificity range from 63-100% (Breiner 2014)
 False positives – non-treatable patients exposed to unnecessary
risks, MAJOR costs
 Of those with treatable disease (by expert consensus),
about 1/3 never met ANY criteria (Bromberg 1991)
 Patient
#2
• Diagnostics
 CSF analysis
 Protein 97, otherwise normal
• Treatment
 Moderate improvement with IVIg
 Strength improved to >=4/5 proximal muscles
 Reflexes 2+ uppers, patella
 Able to ambulate with walker and minimal assistance
 BLIND
SPOTS!!
• CIDP
 Not meeting criteria
 Consider those with basic clinical features
 Asymmetrical, no proximal and distal weakness
 Consider asymmetrical, pure sensory forms
 Patient #2 – revised impression
• “Electrodiagnostic Impression:
Abnormal study. Generalized peripheral
neuropathy with features of acquired
demyelination; suspicious for but not meeting
research criteria for chronic inflammatory
demyelinating polyneuropathy (CIDP)”
• “Clinical Impression:
This patient may have a non-classic form of CIDP.
Consultation with a neuromuscular specialist and
lumbar puncture could be considered.”
 Patient
#3
• 47 year old with 2 months of cramping, numbness
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and tingling on the anterolateral ankle and dorsal
foot
Has had numbness in the right hand for years
Balance is fine
No orthostatic hypotension, constipation, nausea
Strength is normal
Blurry vision, otherwise no oculobulbar complaints
or trouble controlling her bowel or bladder
 Patient
#3
• Physical examination
 Cranial nerves – normal
 Motor exam – normal
 Sensory exam
 Decreased pinprick sensation in the distal foot, otherwise
normal
 Normal vibration, light touch, temperature sensation
 Reflexes - normal
 Coordination - normal
 Patient
#3
• Electrodiagnostics
 CMAP – normal median, ulnar, fibular
 SNAP – normal sural, medial dorsal cutaneous, median,
ulnar, radial
 NEE – normal UE/LE
 Pictures of
EDX
 Patient
#3
• “Electrodiagnostic impression:
Normal study. No generalized peripheral
neuropathy or lumbosacral radiculopathy.”
 Subtle
neuropathies
• EDX techniques to increase sensitivity
 Medial plantar
 Mild diabetics – 50% with prolonged sural latency, 70%
prolonged/absent medial plantar (Reeves 1984)
 Small
fiber neuropathy
• Sensory fibers for pain, temperature, autonomic
fibers
• Clinical presentation with pain, burning
• Usually no numbness, tingling, weakness
• Physical examination
 Loss of pinprick and temperature sensation with normal
light touch, proprioception and vibration
 Normal strength
 Normal MSR
 Small
fiber neuropathy
• Studies
 Electrodiagnostics – normal!!!
 Skin biopsy
 Measurement of intraepidermal nerve fiber density
 Decreased in 77% of patients at the distal calf with clinical
suspicion of small fiber neuropathy (Holland 1998)
 Autonomic testing
 Different tests, yields
 EMG
BLIND SPOTS!!
• Subtle neuropathies
 Consider tests with increased sensitivity (medial plantar)
• Small fiber neuropathy
 Remember standard EDX only tests large fibers
 Patient
#3 – revised impression
• “Electrodiagnostic Impression:
Normal study. No generalized peripheral
neuropathy affecting large fibers.
• Clinical Impression:
A neuropathy primarily affecting small fibers
cannot be excluded with standard electrodiagnostic
studies. Specialized testing (skin biopsy, autonomic
testing) could be considered to further assess this
possibility.”
 EMG
BLIND SPOTS!! – summary
• GBS
 Be aware of low yield in early testing – use H-reflex
 Be aware of non length-dependent findings (sural sparing)
• CIDP
 Be aware of low sensitivity of research criteria
 Be aware of relatively high frequency of atypical presentations
• Possible subtle neuropathies
 Consider testing with increased sensitivity (i.e. medial plantar)
 Remember small fiber neuropathies have negative EDX!
Thank you!!
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Asbury AK, Cornblath DR. Assessment of current diagnostic criteria for Guillain-Barre
syndrome. Ann Neurol 1990;27(suppl):S21-S24.
Albers JW, Donofrio PD, McGonagle TK. Sequential electrodiagnostic abnormalities in acute
inflammatory demyelinating polyradiculoneuropathy. Muscle Nerve 1985;8:528-539.
Gordon PH, Wilbourne AJ. Early electrodiagnostic findings in Guillain-Barre syndrome. Arch
Neurol 2001;58:913-917.
Amato AA, Russell JA. Neuromuscular disorders. New York: McGraw Hill Medical; 2008.
Dyck PJ, Oviatt KF, Lambert EH. Intensive evaluation of referred unclassified neuropathies
yields improved diagnosis. Ann Neurol 1981; 10: 222-226.
AAN – change to EFNS
Breiner A, Brannigan TH. Comparison of sensitivity and specificity among 15 criteria for
chronic inflammatory demyelinating polyneuropathy. Muscle Nerve 2014;50:40-46.
Bromberg M. Comparison of electrodiagnostic criteria for primary demyelination in chronic
polyneuropathy. Muscle Nerve 1991;14:968-976.
Reeves ML, Seigler DE, Ayyar DR, et al. Medial plantar sensory response. Sensitive indicator of
peripheral nerve dysfunction in patients with diabetes mellitus. Am J Med 1984;76(5):842-846.
Holland NR, Crawford TO, Hauer P, Cornblath DR, Griffin JW, McArthur JC. Small-fiber
sensory neuropathies: clinical course and neuropathyology of idiopathic causes. Ann Neurol
1988;55(1):47-59.