Original article/Article originalClinical findings and electrodiagnostic testing in 108 consecutive cases of lumbosacral radiculopathy due to herniated discÉtude clinique et électrophysiologique de 108 cas consécutifs de radiculopathie lombosacrée due à une hernie discale
Introduction
Low-back pain with or without dermatomal painful lower-limb radiation is a common and disabling problem. It is estimated that 15% to 20% of adults present with low-back pain during a single year and that 50% to 80% experience at least one episode of back pain during a lifetime [33]. The incidence of symptomatic lumbar radiculopathy among individuals serving in the United States military, is 4.86 per 1000 person-years [35]. A review of epidemiological studies shows that the prevalence of symptoms of sciatica reported in the literature ranges from 1.2% to 43% [24].
As they provide structural detail of the spine and surrounding structures (CT and MRI) and physiological evidence of root injury (electromyography: EMG), neuroradiological imaging and electromyography are commonly used to correctly diagnose a radiculopathy. Numerous studies were published on the sensitivity and specificity of EMG comparing the EMG results with clinical findings, neuroradiological spine imaging or direct surgical observation [1], [3], [9], [17], [23], [26], [31], [38], [40]. Many exhaustive reviews were reported [2], [12], [16], [32], [34], [37], [39], [44]. These studies are difficult to compare because of differences in patient inclusion criteria, methods for electrodiagnosting testing (EDX), and golden standards for diagnosis of radiculopathy. Often CT/MRI showed multiple alterations of the lumbosacral spine and sometimes the symptoms that were reported by the patient and the objective findings did not match with neuroimaging. Moreover, neuroradiological abnormalities have been demonstrated in lumbosacral spine of asymptomatic subjects [5], [25].
Therefore, it is not yet clear what is the actual occurrence of EDX abnormalities (including EMG and nerve conduction studies) in radiculopathies and whether or not it varies as a function of the level of radiculopathy. The first aim of this study is to report the sensitivity of EDX in a prospective sample of patients affected by L4, L5 or S1 monoradiculopathy due to one single type of cause, i.e., compression by herniated disc (HD). Second, we want to verify whether it varies as a function of both involved root level (L5 vs. S1) and zone of HD causing radiculopathy (foraminal vs. paramedian HD). Third, we look for possible relationships between EMG abnormalities and demographic and clinical variables. For these purposes, we reviewed the database of a study that had been designed to another aim [30].
Section snippets
Patients
All patients affected by lumbosacral monoradiculopathy were prospectively and consecutively enrolled from January 2009 to December 2010 at four EMG labs. The diagnosis of radiculopathy was made on the basis of history (acute pain appearing 1–12 months before the enrolment period), pain distribution (total or partial L4, L5 or S1 dermatomeric distribution, with or without low-back pain), and MRI evidence of HD compressing the root corresponding to the painful dermatome. Foerster's map was used to
Results
The four neurophysiologists initially enrolled 161 cases, of whom 53 were excluded because MRI findings did not match with clinical features. Therefore, 108 consecutive patients (mean age 47.7 years, range 18–64, 55% males) were definitively included in the study. The affected roots, levels, and zones of HD are shown in Table 2, Table 3. The most frequent radiculopathy was L5 (53.7%) and the most frequent level of HD was L4-5 (52.8%). The most frequent zone of radicular compression was in the
Discussion
In this prospective study in a cohort of patients with lumbosacral radiculopathy due to HD, we aimed at:
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evaluating EDX sensitivity;
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looking for differences in demographic, anthropometric, clinical, and EDX findings as a function of both the HD zone and root compression level;
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and determining the predictors of EMG abnormalities.
Electrodiagnostic testing sensitivity
The reported EMG sensitivity and specificity in radiculopathy vary widely in the literature. A recent evidence-based review of the literature emphasized the difficulty of selecting studies and comparing them with each other, in the absence of a true “Gold standard” for diagnosis of lumbosacral radiculopathy [8]. The authors reviewed 335 articles dealing with EDX in patients with radiculopathies and showed that few EMG papers actually met inclusion criteria to be considered class II or III of
Influences of herniated disc zone and root compression level
There were no differences in age, gender, BMI, duration and type of symptoms, objective clinical findings as a function of the HD zone (paramedian or intraforaminal) and level of root involvement (L5 or S1). The only clinical differences between L5 and S1 radiculopathies concerned tendon reflexes. As expected, abnormalities in knee tendon reflexes were more frequent in L5, and in ankle reflexes in S1 radiculopathies. This higher frequency of abnormal knee tendon reflexes in L5 radiculopathy
Predictors of electromyography abnormalities
Unlike some previous literature data [27], our study demonstrates that EMG abnormalities can be predicted by some clinical data. The probability of abnormal EMG is 3.5 times greater in patients with paraesthesiae, 3.8 times greater in patients with abnormal tendon reflexes, and 5.5 times greater in patients with myotomal weakness. Clinical history, dermatomal radiation and some other clinical findings appeared strong predictor of root compression [9]. Careful history and neurological
Conclusions
EDX has a limited sensitivity for the diagnosis of root lesion. The most usual clinical presentation consists of sensory symptoms (paraesthesia, pain). Hence, there is no EDX to reflect increased excitability of sensory fibres at the onset of the clinical presentation. Even if there is clinical sensory deficit due to sensory nerve fibre degeneration, usually at preganglionic site, EDX remains normal and only somatosensory evoked potentials could be altered. EMG and motor neurography anomalies
Disclosure of interest
The authors declare that they have no conflicts of interest concerning this article.
Acknowledgements
The authors are very grateful to Prof. Alessandro Rossi for his helpful suggestions in the discussion of the manuscript.
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