Clinical examination versus routine and paraspinal electromyographic studies in predicting the site of lesion in brachial plexus injury 1
Article Outline
Abstract
Purpose
To study the role of clinical examination, routine electromyography (EMG), and paraspinal EMG individually and in combination to predict the site of lesion in brachial plexus injury.
Methods
Forty cases of brachial plexus injury were evaluated clinically. They then were subjected to routine and paraspinal EMG. All of them underwent surgical exploration and the intraoperative findings were correlated.
Results
The combination of clinical examination, routine EMG, and paraspinal EMG was able to localize the site of the lesion in 80% of patients in both intra- and extraforaminal injury and in 67% in those with a combination type of lesion. The individual parameter predictability was less; paraspinal EMG had the highest individual predictability (67%).
Conclusions
EMG of the paraspinal muscles helps differentiate between root avulsion and distal rupture. It is useful in the planning for surgery, especially when the lesions are evaluated in combination with clinical examination and routine EMG.
Keywords: Brachial plexus, injury, paraspinal electromyography
Brachial plexus injury often results from motor vehicle accidents and high-velocity trauma.1 This is common in the younger population, leading to disabling and devastating neurologic dysfunction.
The pathoanatomic site of injury can be either supraclavicular or infraclavicular. The supraclavicular injuries can be either supraganglionic (intraforaminal) or infraganglionic (extraforaminal). Supraganglionic injuries result from avulsion of the involved nerve roots whereas infraganglionic injuries are caused by distal rupture. Most of these are closed and traction injuries.
Differentiating an intraforaminal lesion from an extraforaminal lesion before surgery helps in reducing the surgical time and proper planning of the reconstruction. Once the diagnosis of extraforaminal lesion is made it implies that proximal donor nerve root is available for exploration and repair. If a diagnosis of intraforaminal lesion is made there would be no need for exploration of the brachial plexus and one can proceed to neurotization (eg, if the C5 or C6 nerve roots are ruptured (extraforaminal) then it can be repaired with the anterior and posterior divisions of the upper trunk, but if they are avulsed (intraforaminal) then neurotization of spinal accessory to suprascapular and 2 fascicles of ulnar nerve to musculocutaneous nerve can be used).
A preoperative diagnosis is useful for effective surgical management. Clinical evaluation including detailed history and physical examination can predict the site of the lesion in 30% to 50% of occasions.2, 3 Routine electromyography (EMG) (EMG of the limb muscles) is helpful to identify the involved nerve roots but its role in differentiating intraforaminal and extraforaminal lesions is minimal.3
The deep posterior muscles of the neck are innervated by the posterior branches of spinal nerves, which branch off immediately after the root emerges from the intervertebral foramen. EMG study of these muscles (paraspinal EMG) helps one to differentiate intraforaminal and extraforaminal brachial plexus lesions.1, 2
The aim of the present study was to assess the efficiency individually and in combination with 3 investigative tools namely-clinical examination, routine EMG, and paraspinal EMG in preoperative differentiation of extraforaminal and intraforaminal lesions and to correlate these with the peroperative findings.
Clinical methods
Forty patients with brachial plexus injuries initially underwent a detailed clinical examination and were documented in a D’Aubigné chart (Fig. 1). 4 These patients then were subjected to preoperative electrophysiologic studies including routine EMG of the upper limb and shoulder girdle musculature followed by paraspinal EMG of the deep cervical musculature.
Figure 1.
D’Aubigné Chart.
Paraspinal electromyography: procedure
After disinfection of the skin, one needle electrode was inserted into the paravertebral region of the neck and a reference electrode was placed. The first tracing was detected at the level of spinous process of C4 and subsequent tracings were obtained by placement of the needles 1 cm lateral and below the level of the spinous processes up to C7. The needles were introduced deeply until contact was made with the bone and then were withdrawn slightly to ensure recording of the electrical activity from the muscles. The amplitude, velocity, and latency of the action potentials obtained were compared with those of the opposite side, which served as the control.
Lesions were classified as intraforaminal and extraforaminal injury based on clinical examination and marked on the D’Aubigné chart (Fig. 1) (ie, presence or absence of winging of scapula, Horner’s syndrome, and severe neuropathic pain in an anesthetized limb). Paralysis of the serratus anterior, rhomboids, supraspinatus, and diaphragm were suggestive of an intraforaminal lesion. The presence of Tinel’s sign in the supraclavicular fossa would indicate an extraforaminal lesion. In addition, partial contraction of sternal and/or clavicular fibers of the pectoralis major and the lattissmus dorsi would suggest an extraforaminal lesion. Patients with mixed findings were categorized as the combined lesion group.
By using routine EMG of the limb muscles patients with denervated muscles (serratus anterior, supraspinatus, and rhomboids) were grouped as having an intraforaminal lesion; patients in whom these muscles were normal but other limb muscles were denervated were categorized as those with an extraforaminal lesion, and those with combination findings were grouped as suffering from combined lesions.
By using paraspinal EMG patients with normal innervated paraspinal muscles detected by an isoelectric line (Fig. 2) were grouped as the extraforaminal lesion group. Those with denervated muscles showing fibrillation potentials at EMG (Fig. 3) were grouped in the intraforaminal group and those with mixed findings were included in the combined lesion group.
Figure 2.
Isoelectric line. The tracing of the paraspinal EMG, which is called electrical silence or the isoelectric line, indicates that the posterior spinal nerve supplying the paraspinal muscles is intact, implying that the root is not avulsed.
Figure 3.
Fibrillation potentials. The paraspinal EMG tracing shows the fibrillation potentials that indicate that the posterior spinal nerve supplying the paraspinal muscles is not intact, implying that the root is avulsed.
All 40 patients underwent surgical exploration of the brachial plexus and the intraoperative findings were documented.
The significance of each of the 3 parameters namely clinical examination, routine EMG, and paraspinal EMG was correlated individually and in combination with the surgical findings, the latter being taken as the standard.
Results
Of the 40 patients included in this study, 34 were men, 4 were women, and 2 were children. The mean age of the adult patients was 30.4 years. Thirtyfour patients had closed injuries and 6 had open injuries, 14 had single or multiple fractures of long bones, 6 patients had a clavicle fracture. The interval between injury and clinical examination varied from 1 to 18 months.
At surgery 14 patients had intraforaminal, 20 had extraforaminal, and 6 patients had combined lesions. Clinical examination alone could identify the site of the lesion correctly in 6 of 14 in the intraforaminal group, 10 of 20 in the extraforaminal group, and 2 of 6 in the combined lesion group. Routine EMG identified 2 of 14 in the intraforaminal group, 10 of 20 in the extraforaminal group, and 0 of 6 in the combined group; paraspinal EMG identified the site of the lesion accurately in 9 of 14 in the intraforaminal group, 14 of 20 in the extraforaminal group, and 4 of 6 in the combined group (Table 1).
Table 1. Brachial Plexus Injuries: the Predictability of Clinical Versus EMG in Identifying the Site of the Lesion
| Site of Lesion Intraoperative Finding | Intraforaminal 14 (35%) | Extraforaminal 20 (50%) | Combined 6 (15%) |
|---|---|---|---|
| Clinical | 6 (43%) | 10 (50%) | 2 (33%) |
| Routine EMG | 2 (14%) | 10 (50%) | 0 (0%) |
| Clinical and routine EMG | 6 (43%) | 11 (55%) | 2 (33%) |
| Routine and paraspinal EMG | 9 (64%) | 14 (70%) | 4 (67%) |
| Clinical and routine and paraspinal EMG | 11 (80%) | 16 (80%) | 4 (67%) |
It can be observed from the table that when used alone clinical examination, routine EMG, and paraspinal EMG could not locate the site of lesion in 22 of 40, 28 of 40, and 13 of 40 patients, respectively.
Combination of clinical and routine EMG or routine and paraspinal EMG did not improve the predictability of the site of the lesion (Table 1). A combination of all 3 modalities of investigation; however, could predict the site of the lesion in 11 of 14 in the intraforaminal group, 16 of 20 in the extraforaminal group, and 4 of 6 in the combined group, indicating the complementary role of each of the 3 tests.
Discussion
Preoperative diagnosis of the site of the lesion in brachial plexus injury always has posed problems in management of these patients.3 Studies worldwide clearly have shown that clinical examination alone has several limitations.1, 3 For example, patients with upper-root avulsion develop a trick movement for the action of rhomboids. The middle fibers of the trapezius act with rhomboids to produce retraction of the scapula. Therefore testing of the rhomboids is not reliable in differentiating root avulsions and distal injuries. Individuals with upper-root avulsion do not develop winging of scapula because the serratus anterior is supplied by 3 roots (C5, 6, 7) and avulsion of all 3 roots is rare.5, 6 Also clinically there are no definite means to differentiate extraforaminal from intraforaminal and combination lesions.
When all 3 investigative modalities were used individually the paraspinal EMG was found to have the highest predictive value (67%). The combination of any 2 investigations did not improve the predictive value considerably in our study. All 3 tests together yielded the highest predictability of 80% for both the intraforaminal and extraforaminal group and 67% for the combination group. These 3 tests could serve as a simple, inexpensive modality of preoperative evaluation of patients with brachial plexus injury. Computed tomography myelography and magnetic resonance imaging can be reserved for those patients with multiple-level lesions.7, 8 The accuracy of detection of nerve-root injury for magnetic resonance myelography was 92% and for computed tomography myelography was 92%.9
The addition of paraspinal EMG to the existing armamentarium of clinical and routine EMG of the paraspinal muscles serves as a simple bedside investigative procedure and is able to differentiate between root avulsion and distal rupture.2 It also establishes the presence of an intact donor root if neurotization is planned.
There are, however, a few limitations using paraspinal EMG. Being an invasive technique it is not reliable in children younger than 5 years. Retraction of the proximal nerve root into the intervertebral foramen may give a false identification of an extraforaminal lesion.2 This has been noted in 3 patients in the present study. A normal paraspinal EMG only suggests that 2 or more roots may be intact as was noticed in 4 patients in the present series. Also it does not provide a definite diagnosis on the affected root or roots affected. It is definitely a more reliable investigation modality in complete brachial plexus injury rather than an incomplete injury.
Acknowledgements
The authors are extremely thankful to M. Dhanraj, Professor and Head, Department of Neurology, and Arul Mozhi, Resident, Department of Neurology, Stanley Medical College and Hospital, for their service in performing the EMG studies, evaluation, and valuable contribution.
References
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- 1 No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
PII: S0363-5023(03)00423-4
doi:10.1016/j.jhsa.2003.08.004
© 2004 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.
