Referral Guidelines for Electrodiagnostic Evaluations

I have summarized guidelines for when to refer patients for nerve conduction studies (NCS) and EMG based on standards established by the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM) and modified when appropriate to coverage by Medicare. Most insurance companies use Medicare and/or the AANEM guidelines to approve or deny payment.

In general EMG/NCS is utilized in pain management to differentiate between musculoskeletal and neurological/neuromuscular conditions:

•  Make or confirm a suspected diagnosis 

• Define severity of nerve or nerve root injury 

• Differentiate acute from chronic lesions

AANEM GUIDELINES FOR EDX REFERRAL

• To establish or confirm a clinical diagnosis

• To localize nerve lesions

• To determine the extent of nerve or muscle injury 

• To correlate findings on anatomic studies 

• To assist in prognosis (estimate axonal repair after injury or surgical repair) 

• To guide in patient management (example: evidence for repair may justify therapy)

MEDICARE INDICATIONS/GUIDELINES MEETING MEDICAL NECESSITY (Based on a typical Medicare review policy)

• Indentify normal/abnormal function of sensory/motor nerves, muscles 

• Localize peripheral nerve lesions and/or sites of abnormal function 

• Define the type of abnormal function: neuropraxia, axonotmesis, etc. 

• Determine the distribution and severity of abnormalities 

• Estimate the date and/or duration of a nerve injury or disease 

• Determine the progression and/or recovery of abnormal function 

• Aid in specific diagnosis and prognosis of disease 

• Aid in selecting treatment options 

• Aid in following treatment with objective evidence 

• Localize correct areas for IM administration of agents such as Botox

INDICATIONS FOR REPEATED ELECTRODIAGNOSTIC TESTS

• To confirm an initial test or for a second opinion 

• To repeat a test with equivocal results 

• To monitor marked clinical changes in a condition

• To follow conditions that are expected to respond to surgical or medical treatments 

• To evaluate a new set of symptoms

SYMPTOMS/SIGNS THAT MAY INDICATE THE NEED FOR EDX

• Numbness, tingling, pins and needles, burning 

• Weakness, wrist drop, foot drop 

• Neck or back pain, wrist pain, foot pain 

• Muscle atrophy, reflex loss, cramping 

• Unequivocal neurological findings 

• Unclear neuromuscular examination 

• Clarify differential diagnosis and/or define degree of impairment 

• No response to treatment or a progression of symptoms after treatment 

• Rule out a non-structural disorder in the absence of a structural lesion

MORE SPECIFIC CLASSIFICATION OF FINDINGS:

• NEGATIVE FINDINGS: (ABSENCE OF SENSATION) Numbness (stocking and glove due to susceptibility of longer nerves) Injury insensitivity Sensory symptoms in the toes

• POSITIVE FINDINGS: (PARESTHESIAS) Prickling, tingling, “pins and needles”, burning, crawling, itching, Abnormal sensation to temperature, pain 

• NEUROPATHIC PAIN: Describe feet as “tight” Prominent symptoms at night Painful prickling, burning, electrical, sharp or jabbing sensations

• ALLODYNIA Provocation of pain by mechanical stimuli (bed covers, shoes, walking) Walking may be painful and hesitant or unsteady Predisposed to falling in later stages due to impaired proprioception

• MOTOR MANIFESTATIONS Loss of reflexes Atrophy of the FDI, APB, or EDB muscles Weakness of grip, opposition, toe and ankle dorsiflexors

• AUTONOMIC NEUROPATHY Distal anhidrosis or inappropriate truncal sweating Constipation, sometimes alternating with diarrhea Less frequent: fecal incontinence, dysphagia, heartburn, nausea & vomiting, bloating Impotence Postural hypotension with orthostatic dizziness or occasional fainting

WHEN LOOKING AT OUTSIDE EMG REPORTS:

What to look for in the NCS report:

• Motor latency, conduction velocity, and amplitude

• Sensory latency and amplitude

• Fwave and Hwave latencies

• Right to left comparisons

• Nerve to nerve comparisons

• Are findings motor or sensory or both

• Are findings demyelinating (conduction slowing) or axonal (reduced amplitudes) or a combination of both

• EMG findings: abnormal “denervation” (positive sharp waves, fibrillations), motor unit analysis, statement of normal or abnormal recruitment, outline of nerve root levels that are normal versus abnormal to define level and severity of radiculopathy

What to expect from an NCS report:

• Clinically and physiologically relevant interpretation and diagnosis

• Outline of the localization, severity, and acuity of the abnormal findings

• Notation of other diagnosis detected and/or excluded 

• Explanation of any technical problems 

• Need for re-evaluation in the future 

• Urgent need for medical/surgical intervention

Limitations of NCS: not generally helpful in the evaluation/diagnosis of:

• Pain from joint disease 

• Fibromyalgia or myofascial pain syndromes 

• Central nervous system disorders 

• Disorders that do not arise from the neuromuscular system In summary, always document extremity to test and diagnosis to rule in or out. Include any abnormal neurological exam findings including motor, sensory, reflex, atrophy, etc..

Case examples:

Patient has axial neck pain with nocturnal hand numbness. Order EDX to rule out carpal tunnel syndrome. CTS is the great masquerader most frequently overlooked in upper extremity pain syndromes involving neck, shoulder, and elbow.

Patient has HNP with referred extremity pain. Order EDX to confirm level and severity of cervical or lumbar radiculopathy. Severe nerve root dysfunction might indicate surgery.