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Value of EMG in Patients With Non-Migrainous, Persistent Head Pain

High cervical EMG findings not only implicate an offending degenerative lesion, but also can provide information regarding the presence of acuity and chronicity

Non-migrainous, persistent head pain can be challenging to diagnose, as both intra- and extracranial etiologies must be considered. However, when x-ray, computed tomography (CT), and magnetic resonance imaging (MRI) are ordered, degenerative lesions often are found in the high cervical region, and may be ignored, given their degenerative or spondylotic label. The high cervical electromyogram (HC-EMG) is particularly adept at assessing these lesions, given its ability to study the nerve roots that emanate from the corresponding spinal segmental levels.

The HC-EMG findings would not only implicate an offending degenerative lesion, but also can provide information regarding the presence of acuity and/or chronicity. This, in turn, may be correlated with the clinical history to determine if the temporal relationship is congruent or not, thereby assisting in resolving the primary pain generator. Once a suspect lesion is diagnosed to have acute or chronic activity on HC-EMG, a more focused approach to treatment may be initiated with a higher confidence level.

When ordering an HC-EMG, clinicians should specifically request that a paraspinal study of nerve roots C2, C3, and C4 be performed, as well as a needle study of the sternocleidomastoid (SCM) and trapezius (TPZ) muscles, as some electromyographers may not routinely include all of these levels and muscles in their testing protocol.

Cervical paraspinal EMG (C5-C7) in the diagnosis of neck and extremity pain is widely used and accepted.1-6 However, we believe our study7 is the first to address its value in assessing high cervical degenerative lesions as potential head pain generators in this patient group.

Methods
During a 30-month period, 24 patients underwent HC-EMG. In order to properly evaluate the contribution by any adjacent spinal segmental lesion, those with migraine or migraine-like syndromes were excluded. The results were then correlated with clinical findings, and where available, x-ray, CT, and MRI lesions at C1-C2, C2-C3, C3-C4, C4-C5 levels. Lesions imaged included disc bulge, protrusion, extrusion, disc osteophyte complex, listhesis, foraminal or recess narrowing, root or spinal cord impingement, thecal sac effacement, and canal stenosis (Tables 2-4; imaging abbreviations appear in Table 4).

HC-EMG Technique: C2, C3, C4 Paraspinal Muscles
To perform the paraspinal EMG at the C2, C3, and C4 levels:
Patient position: Have the patient lie in the lateral decubitus position, with the side to be studied upward.|
Needle insertion: Palpate the occiput, then drop just caudal to occiput, and the first spinous process palpated is C2. The second spinous process palpated is C3, and the third spinous process palpated is C4. Insert the needle one to two fingerbreadths from spinous process, directed slightly medially into deeper muscles to lamina; pull back slightly.
Activation: Extend the neck to activate the muscle group.
Ground electrode: Place the ground electrode over the muscle belly, adjacent to insertion point.

HC-EMG Technique: Sternocleidomastoid
To perform the SCM EMG:
Patient position: Have the patient lie in the lateral decubitus position, with the side to be studied upward.
Needle insertion: Locate the SCM by having the patient rotate his or her head toward contralateral side being tested. Then insert the needle into the belly of the SCM, 5 to 7 cm 
below the mastoid process (or near the midpoint of the SCM). Note: This is a superficial needle placement.
Activation: Turn the head to the contralateral side to activate this muscle group.

HC-EMG Technique: Trapezius
To perform the TPZ EMG:
Patient position: Have the patient lie in the lateral decubitus position, with the side to be studied upward.
Needle insertion: Locate the TPZ muscle by having the patient shrug his or her ipsilateral shoulder and confirm by having the patient laterally flex head-neck toward the shoulder. This will be near where the posterior shoulder meets the neck. Note: This is a superficial needle placement.
Activation: Shrug shoulder and/or laterally flex neck to activate this muscle group.

High Cervical Data Distribution
We found the HC-EMG to be abnormal in 58.3% of patients. Of this group, 78.6% had neuroimaging available. Of those, 63.6% had HC-EMG findings that correlated with corresponding lesions seen on x-ray, CT, or MRI at the C1-C2, C2-C3, C3-C4, and C4-C5 spinal segmental levels. Note, lesions at the C4-C5 level were included as well, as its C5 root subserves the segment above it (C3-C7), and hence, may have contributed to referred pain to the high cervical region.

Root Pain Distribution Data
Acute root findings were seen in 25% of patients at the C2 root (C1-C2 spinal segmental level); 50% of patients had acute findings at the C3 root (C2-C3 spinal segmental level), and 25% at the C4 root (C3-C4 spinal segmental level. Examples of acute findings, fibrillation potentials, and positive sharp waves are shown in Figures 7 and 8.

Chronic root findings were seen in 25% of patients at the C2 root (C1-C2 spinal segmental level); 40% of patients had chronic findings at the C3 root (C2-C3 spinal segmental level) and 35% at the C4 root (C3-C4 spinal segmental level). An example of chronic findings, a polyphasic motor unit potential, is shown in Figure 9.

Of those patients with an abnormal HC-EMG, all had pain located in the occipital region.

Summary
The HC-EMG is a valuable diagnostic tool in the assessment of non-migrainous, persistent head pain of extracranial origin. Its routine use is recommended in the evaluation of occipital head pain, particularly in patients with known high cervical spinal segmental lesions at the C2-C3 level.

 

Last updated on: December 16, 2011
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