Electrodiagnosis in the
management and treatment of
cervical and lumbar spine disorders
Jonathan S. Rutchik, MD, MPH
NEUROLOGY, ENVIRONMENTAL AND OCCUPATIONAL MEDICINE
ASSOCIATES
20 Sunnyside Avenue, Suite A-321
Mill Valley, CA 94941, USA
TEL: 415-381-3133
FAX: 415-381-3131
jsrutch@neoma.com
www.neoma.com
OUTLINE
• Radiculopathy; epidemiology and EMG
• What is an EMG/ NCV?
– What is an F wave; an H reflex?
• What is the relevant anatomy?
• What are the indications in patients with
suspected cervical or lumbar radiculopathy?
• What are the relevant treatment guidelines?
– ACOEM, ODG, AANEM, AAN, ETC
• Thoracic outlet syndrome
• Interpretation of Data
JS Rutchik, MD, MPH
www.neoma.com
CERVICAL RADICULOPATHY
AND EMG
• Age adjusted annual incidence 83.2/ 100,000
– 202.94 (50 and 54), <= CTS, <50% of stroke.
• Recurrence in 31.7%. 26% undergo surgery
• False positive rate (MRI) 20 - 50% with age.
• Electrodiagnostic testing of paraspinal and limb
muscles is 50 years old.
• EMG complements MRI with its ability to localize
a lesion and assess functionality of the nerve.
• False negative studies: 50-71% sensitive, 6585% specific.
JS Rutchik, MD, MPH
www.neoma.com
EMG/NCV: TWO PARTS
“mild shocks and thin needles”
• Nerve conduction velocity: Electrical tests of the
motor and sensory nerve cables
– Conduction velocity (MYELIN)
– Distal latency (MYELIN)
– Amplitude at recording electrode (AXON)
• Electromyography: Needle placed in muscle
–
–
–
–
Spontanous activity (NERVE INJURY)
Recruitment (POWER)
Location and Chronicity of injury
Neuromuscular junction (N/A)
JS Rutchik, MD, MPH
www.neoma.com
NERVE CONDUCTION STUDIES
• Motor studies
• Sensory studies
• Late responses (F waves) that assess the
proximal motor root
• H reflexes that assess the sensory afferent and
motor effect reflex loop of S1 (*C7/C8)
JS Rutchik, MD, MPH
www.neoma.com
MOTOR STUDIES
• Motor nerve test:
– Supermaximal stimulation.
– Distal latency, Amplitude and Nerve
Conduction Velocity
• Upper Extremity:
– Median, Ulnar, Radial
• Lower Extremity:
– Peroneal, Tibial
JS Rutchik, MD, MPH
www.neoma.com
F waves
• Motor F wave studies proximal roots:
– Antidromic motor to the anterior horn of the spinal
cord; orthodromically to the muscle.
• Pure motor test.
• A prolonged asymmetric F waves suggest a
proximal root lesion.
• Clinical application best for plexopathy.
– Quite prolonged in demyelination, AIDP, mild
prolongation in axonal injury.
• Less sensitive than EMG for radiculopathy since
only short segment of nerve is demyelinated in
radiculopathy.
JS Rutchik, MD, MPH
www.neoma.com
SENSORY STUDIES
• Sensory nerve testing:
– Submaximal stimulation
– Distal latency, amplitudes and nerve
conduction velocity
• Upper Extremity:
– Median, Ulnar, Radial
• Lower Extremity:
– Superficial peroneal, sural
JS Rutchik, MD, MPH
www.neoma.com
Sensory studies
• Sensory slowing supports a localization
distal to the Dorsal Root Ganglion
• Sensory slowing in itself suggests either
two processes or NOT a pure
radiculopathy.
• Pearl: recording at thumb assesses upper
trunk and C6, D1 is C7 and middle trunk.
JS Rutchik, MD, MPH
www.neoma.com
H REFLEX
•
•
•
•
•
Reflex loop: Orthodromic sensory and motor
Utilized to assess for radiculopathy of S1, *C6/7
S1; Popliteal fossa, record in MG
C6/7; Median nerve at wrist, record at FCR
Unilateral delay, absent suggests tibial, sciatic,
sacral plexus, cord, S1 motor or sensory roots.
– Once abnormal, may not normalize; limited for
patient with prior
– Often absent in polyneuropathy or > 60.
JS Rutchik, MD, MPH
www.neoma.com
NEEDLE EMG
• Screening cervical and lumbo- sacral myotomes
– PARASPINAL, INDIVIDUAL MUSCLES
• Anatomy
• Needle insertion near motor point
– INSERTIONAL ACTIVITY AT REST
– RECRUITMENT TO FULL CONTRACTION
– SINGLE MOTOR UNIT ASSESSMENT
JS Rutchik, MD, MPH
www.neoma.com
Why is EMG helpful?
• Differentiates Nerve roots, dermatomes, both:
– C5 v C6 or Median v. Ulnar, or C8 v median
• Chronicity of problem:
– Acute (activity at rest) versus
– Chronic (abnormal wave forms in isolated muscle
fiber testing)
• F wave assesses proximal root only
• Axonopathy confirmed with needle
• Severity/ improvement; distal to proximal
JS Rutchik, MD, MPH
www.neoma.com
INDICATIONS FOR EMG/ NCV
• Pain
• Paresthesia radiating to a nerve root
distribution
• Associated sensory distrubance +/• Parspinal muscle spasm
• Motor dysfunction +/• Exam findings in specific sensory
dermatome or motor myotome
JS Rutchik, MD, MPH
www.neoma.com
AANEM* and EMG
American Academy of Neuromuscular and Electrodiagnostic MEdicine
• C radiculopathy is listed as a possible differential
diagnosis and “may be useful” in patient with
neck, shoulder or arm pain, numbness, altered
sensation (e.g., pins and needles), weakness,
cramps, fasciculations, muscle atrophy or
hypertrophy (focal or diffuse)
• L radic is listed as a possible differential
diagnosis and “may be useful” in patient with
back, hip or leg pain, numbness, altered
sensation (i.e., pins and needles), weakness,
cramps, fasciculations, muscle atrophy or
hypertrophy.
JS Rutchik, MD, MPH
www.neoma.com
AANEM, C spine and EMG
Muscle Nerve 22: supp 8, S209-211, 1999
• Guideline:
• Needle: >= one muscle innervated by each spinal root,
cervical 5, 6, 7, 8, and thoracic 1 in asymptomatic limb.
• Cervical paraspinals at 1 or more levels should be
examined
– Not in prior posterior approach of laminectomy.
• >= one motor and one sensory NCV study to determine
if concomitant polyneuropathy or nerve entrapment
exists.
• Median and ulnar nerves M and S studies; if symptoms
suggest CTS or ulnar neuropathy.
• NCV abnormal, or suggestion of polyneuropathy, NCV of
other ipsilateral and contralateral nerves to define the
cause of any abnormalities.
JS Rutchik, MD, MPH
www.neoma.com
AANEM, C spine and EMG
Muscle Nerve 22: supp 8, S209-211, 1999
• Option:
• If needle abnormal, one or more contralateral muscles to
exclude bilateral radiculopathy
• Differentiate between radiculopathy and polyneuropathy,
motor neuron disease, spinal cord lesion, or other
neuromuscular disorders.
• Median and ulnar F wave studies for suspected C8 or T1
radiculopathy; compare with contralateral side.
• Perform H reflects of the FCR to assist in identifying
pathology of the cervical 6 and 7 nerve root.
JS Rutchik, MD, MPH
www.neoma.com
EMG and Radiculopathy
• Indicated often to rule out other conditions
• Upper extremity nerve entrapments, brachial
plexopathy, thoracic outlet syndrome, hereditary
or acquired neuropathies
• Lower extremity entrapments, cauda equina
syndrome, conus medullaris, spinal cord
conditions, polyneuropathy
• These disorders are important considerations in
the electrodiagnostic evaluation of patients with
a suspected radiculopathy.
JS Rutchik, MD, MPH
www.neoma.com
ACOEM, EMG and
Neck Pain
• When the neurologic examination is less clear, however,
further physiologic evidence of nerve dysfunction can be
obtained before ordering an imaging study.
Electromyography (EMG), and nerve conduction
velocities (NCV), including H-reflex tests, may help
identify subtle focal neurologic dysfunction in patients
with neck or arm symptoms, or both, lasting more than
three or four weeks.
• Absence of progression motor weakness in 4-6 weeks.
(Table 8-3)
• Clarify nerve root dysfunction preoperative or preepidural
Not if history, physical exam and imaging consistent (D)
(Table 8-8)
JS Rutchik, MD, MPH
www.neoma.com
ACOEM, EMG and
Lower Back Pain
• EMG may assist in identifying/ defining low back
pathology such as disc protrusion, cauda
equina, spinal stenosis and post laminectomy
syndrome (Table 12-7).False-positive rate is
30% for imaging studies > 30 w/o sx, risk of dx
confusion is great.
• Needle EMG and H reflexes to clarify nerve root
dysfunction (C) (Table 12-8)
– Not rec for clinically obvious radiculopathy (D)
JS Rutchik, MD, MPH
www.neoma.com
Official Disability Guidelines, EMG
and Cervical spine
• “Not necessary for 4-6 weeks. Not necessary for the
diagnosis of intervertebral disk disease with
radiculopathy”
• Usefulness in differentiating neuritis, neuropathy, or
muscle abnormalities from radicular neuropathy and for
cases where the etiology of the pain is not clear.
• Cites AANEM guidelines.
• Issue of requirement of positive EMG for diskectomy or
laminectomy. Washington State
• Recommended (needle, not surface) as an option in
selected cases.
• Odd mention of no indication for F waves or NCV (only in
CTS?) but indication for H reflexes.
JS Rutchik, MD, MPH
www.neoma.com
Official Disability Guidelines, EMG
and Lumbar spine
• May be useful to obtain unequivocal
evidence of radiculopathy, after 1-month
conservative therapy, “but not necessary if
radiculopathy is already clinically obvious”
• EMG’s may be required by the AMA
Guides for an impairment rating of
radiculopathy.
– (Note: Needle EMG and H-reflex tests are
recommended, but Surface EMG and F-wave
tests are not very specific and therefore are
not recommended
JS Rutchik, MD, MPH
www.neoma.com
Thoracic Outlet Syndrome/
Brachial Lumbosacral plexopathy
•
•
•
•
•
Controversy: true neurogenic rare
Sensory and motor loss in C8-T1 distribution
Fibrous band over T1.
Weakness in thenar and hypothenar, atrophy.
Protocol includes antebrachial studies (SNAP) to
assess lower and upper truck.
– Ulnar and medial antebrachial SNAP abn, median
SNAP normal. Median MUAP reduced > ulnar MUAP.
• Collision studies?
• Thorough needle examination
JS Rutchik, MD, MPH
www.neoma.com