Basics of Electrodiagnostic Medicine

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Basics of Electrodiagnostic Medicine

• Patrick Kortebein MD
• UAMS Department of Physical Medicine
  Rehabilitation
• 4/10/06

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Electrodiagnostic Studies

• Nerve Conduction Studies (NCS)
• Motor
• Sensory
• Other (F-wave, H-reflex)
• Electromyography (EMG)
• Needle exam

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Purpose

• 1. Confirm a tentative clinical diagnosis
• 2. Exclude other disorders
• 3. Determine stage of disease
• e.g., location, severity, rate of progression,
  
• prognosis
• 4. Characterize disease
• e.g., axonal vs demyelinating
• 5. Identify subclinical disease

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Example

• 1. NCS- Motor / Sensory
• Axonal vs Demyelinating process

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NCS Common Nerves

• Upper Extremity
• Median
• Ulnar
• Radial
• Lower Extremity
• Peroneal
• Tibial
• Sural (sensory)
• Normal Values- Variable

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Example

• 2. EMG
• Muscle Electrical Activity
• Rest
• Volitional Activity

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Reasons for Referral

• Numbness/Paresthesias
• Pain radicular
• Weakness generalized/facial (MG)
• Muscle atrophy
• Muscle twitching/
• fasciculations

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Common Referrals

• Motor Neuron ALS
• Radiculopathy (Cervical / Lumbar)
• Peripheral Nerves (Motor/Sensory)
• Carpal Tunnel Syndrome
• Foot Drop
• Polyneuropathy (except small fiber)
• AIDP (Guillain Barre)
• NMJ Myasthenia Gravis
• Muscle Myopathies

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Timing of Referral

• Acute vs Chronic
• Acute nerve injury/damage
• Nerve laceration (NCS)
• Radiculopathy (7-10 days to weeks)
• Chronic nerve injury
• Radiculopathy- persistent findings distinct from
  acute process (active vs inactive)

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Referrals

• Axial Neck / Low Back Pain
• Generally, not indicated
• Necessary?
• Will it change your treatment plan?
• Do you need assistance with diagnosis?

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Who performs NCS/EMG?

• Neurologist
• Physiatrist (PMR)- required residency
• Physical Therapist (rare)
• Technicians (NCS only)
• Additional Training
• Fellowship
• Board Certification
• AANEM (Amer Assoc Nm EDX Med)

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What tests are performed?

• Depends on
• Referral Question
• Evaluation by examiner
• EDX testing is an extension of the physical exam.
• Address the patients problem
• General
• NCS (e.g., CTS)
• EMG (e.g., cervical radiculopathy)
• NCS EMG

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Cost?

• Nerve Conduction Studies
• Motor- 90/test
• Sensory- 80/test
• EMG (minimum 5 mm per extremity)
• One extremity- 250

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Real world patient scenario

• 46 yo RH F restaurant owner
• CC Constant numbness/tingling right ulnar 2
  digits for 1 month
• HPI Carries trays at work, No clear
  aggravating/alleviating position/activities, no
  weakness
• Meds/Allergies None, PMHx None
• UExt Neuro Exam M/S/R normal, inc ulnar digits
  sensory
• Tinels at elbow- Positive ? Dx?

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Real world patient scenario

• Referral NCS
• Ulnar neuropathy at the elbow
• Primary MD
• NEUROMetrix in office
• Testing performed- Inconclusive
• Second study performed
• Time
• Expense
• Patient discomfort

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Questions?