Section 4 Neck Pain With Radiating Features

Question 1

What is EMG?

Answer 1

Electrophysiological tool used to help diagnose neuromuscular diseases and radiculopathy by measuring motor unit activity

Can be used to guide intramuscular injections

Used intraoperatively for neuromuscular monitoring of neuromuscular blocking drugs

Often performed with nerve conduction studies NCS

Question 2

Primary categories of the neuromuscular pathological processes which EMG can differentiate are the following?

Answer 2

Neuropathic and myopathic

Question 3

Myelopathy appearance on EMG

Answer 3

Short duration and longer amplitude

Question 4

Myopathy on EMG

Answer 4

Short duration and lower amplitude

A normal number of voluntary motor units generate reduced force, requiring a greater number of motor units to be activated and for those to fire at a faster rate

Question 5

Neuropathic on EMG

Answer 5

Larger motor unit action potential, reduced recruitment.

Can be polyphasic due to desynchronization of individual potentials

Question 6

Indications for EMG

Answer 6

Peripheral neuropathies
Entrapment neuropathies
Muscle disorders
Radiculopathies
-EMG is greater than NCS for radiculopathy

Question 7

Why use EMG

Answer 7

Can help in differentiating neuropathic disorders from myopathic disorders

Help exclude neuromuscular conditions that can mimic myopathy such as motor, neuron disease and neuromuscular junction disorders

Confirmed diagnosis of muscle disorder when motor units with characteristic morphology and recruitment patterns are identified.
Add diagnostic information relating to location, type, severity of underlying process

Useful for identifying target muscles for biopsy

Question 8

Contraindications to EMG

Answer 8

Significant coagulopathies, extra care is taken if a patient is on anticoagulation

Blood dyscrasias

Implanted cardiac defibrillator

Question 9

Risks/ complications of EMG

Answer 9

Infection via traumatic introduction of skin bacteria, especially in patients with lymphedema

Question 10

EMG limitations

Answer 10

*EMG is helpful for identifying the presence of radiculopathy, but it does not rule out radiculopathy. In patients with radiculopathy, the EMG will only be positive IF there is demyelination or axonal degeneration affecting motor neurons

EMG is best used for superficial muscle, signals from superficial muscles can cause interference in the signal generated from deep muscles, recording is weakened by excess adipose tissue

Question 11

EMG summary

Answer 11

EMG assists in the detection of electrical abnormalities within specific target muscles, and can support the presence or absence of nerve damage or pathological processes.

Basically, EMG is done to find diseases that damage muscle tissues, nerves, or the junctions between the nerve and the muscle:

Radiculopathy due to disc compression
ALS
Myasthenia gravis
To find the cause of muscle weakness
It does not show brain or spinal cord diseases

Question 12

Interscalene triangle

Answer 12

Anterior and middle scalenes, first rib

Question 13

Costoclavicular space

Answer 13

Clavicle, first rib, superior scapula

Question 14

Thoracocoracopectoral space

Answer 14

Pectoralis minor, coracoid process, ribs 2-4