The two most common peripheral nervous system disorders seen in electrodiagnostic medicine are radiculopathy and entrapment neuropathies.(1) Both conditions have pain and paresthesias in the limbs, with weakness, but the pathologies are quite different.(2) Radiculopathy is the term used to describe a nerve root within or near the intervertebral foramen, usually caused by a herniated disc, spinal stenosis or wear and tear.(3) In the event of entrapment, the peripheral nerve gets entrapped at a specific anatomic narrowing along its course (e.g. the carpal tunnel for the median nerve, the cubital tunnel for the ulnar nerve, the fibular neck for the common peroneal nerve).(4, 5) These differences have important electrodiagnostic consequences. As the pathology is located above the dorsal root ganglion (DRG), this is termed preganglionic lesion or radiculopathy.(6) As a result, the sensory nerve action potential (SNAP) is usually not altered, since the sensory fiber cell bodies and the distal axons of the sensory fibers are not compressed by the disease process.(7) Unlike entrapment neuropathy, which occurs in the peripheral nerve distal to the DRG, the SNAP amplitude may be decreased or completely absent depending on the degree of axonal loss or demyelination.

This electrophysiological difference is the inherent basis for differentiating the two conditions.(8) There is conflicting opinion in the literature regarding the usefulness of NCS in the diagnosis of radiculopathy.(9) Needle EMG is more sensitive for radiculopathy, and can localize the segment involved, by detecting denervation potentials and motor unit action potential (MUAP) changes in a myotomal distribution.(10) The role of NCS is more defined in entrapment type of neuropathies.(11) The site of compression can be precisely localized by focal conduction slowing or conduction block.(12) In the case of carpal tunnel syndrome, the most common upper extremity neuropathy, the typical findings in NCS are delayed median sensory conduction, prolonged distal motor latency, and characteristic double peak responses.(13) The use of the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM) guidelines yields a much higher diagnostic sensitivity for cubital tunnel syndrome.(14) With the AANEM guidelines, calculating across-elbow MNCV elevated sensitivity to 87.5% and 100% for clear CBTS and any ulnar neuropathy, respectively, in a study of 118 elbows with clinical CBTS.(15) These conditions should be given attention in Pakistan. In one study in Pakistan, people with type 2 diabetes mellitus developed carpal tunnel syndrome 13.2% of the time.(16) The prevalence of CTS among hospital administrative staff in the twin cities was 79.5% by using the Boston Questionnaire and Phalen's test.(17) In a study conducted in Pakistan on 300 patients with chronic low back pain, 65.7% had lumbar radicular pain, of which 79.7% had their pain radiate to the ankle or foot.(18) All these epidemiological data strengthen the burden of both these diseases in the Pakistani population.

2.1 Study Design This was an observational, comparative and cross-sectional study, which took place for six months. 2.2 Study Setting The study was carried out in 2 tertiary care centers in Abbottabad, Pakistan namely: Ayub Medical College (ATH) Abbottabad's Combined Military Hospital (CMH) is located here. 2.3 Study Duration This study was from July 2025 to December 2025. 2.4 Study Population Patients age 18 years and older, with clinical suspicion of radiculopathy (cervical or lumbosacral) or entrapment neuropathy (carpal tunnel syndrome, cubital tunnel syndrome, common peroneal neuropathy, or tarsal tunnel syndrome) and referred for electrodiagnostic evaluation were eligible for inclusion. 2.5 Inclusion Criteria Adults (Male and Female, ≥18 years) History and physical examination (dermatomal pain, positive straight leg raise test, and/or changes in reflexes) History and physical exam suggestive of entrapment neuropathy (night time paresthesias, positive Tinel's and Phalen's test, focal weakness) Agreement to full NCS and needle EMG testing Informing and obtaining written consent. Informing and getting written consent. 2.6 Exclusion Criteria Pathological condition of the nerves (e.g. diabetic, alcoholic, hereditary). Neuromuscular disorders (myasthenia gravis, motor neuron disease) affecting the whole body Previous surgery or trauma to the same (ipsilateral) side limb nerve. Coagulopathy that is too severe, or contraindication to needle EMG Pregnancy Inability to obtain full E.D. testing and/or noncompliance. 2.7 Sample Size Non-probability consecutive sampling technique was used to recruit 100 patients, 50 patients each from the two hospitals to make a balanced comparison. 2.8 Electrodiagnostic Protocol Standardized electrodiagnostic testing was performed in all patients with either the Nihon Kohden or a similar machine. Nerve Conduction Studies (NCS): Motor nerve conduction: CMAP amplitude, distal latency, conduction velocity of median, ulnar, radial, common peroneal and tibial nerves Subjective neurophysiologic evaluation of nerve conduction: SNAP (amplitude and conduction velocity of median, ulnar, superficial radial, sural, and superficial peroneal nerves) F-waves: evaluated for proximal nerve conduction of median, ulnar, and tibial nerves H-reflex: performed selectively in the evaluation of S1 radiculopathy. Needle Electromyography (EMG): Muscle biopsy (concentric needle biopsy) in appropriate myotomes and peripheral nerve territories Evaluation of spontaneous activity (fibrillation potentials, positive sharp waves), MUAP morphology and recruitment patterns 2.9 Diagnostic Criteria Electrodiagnostic criteria for radiculopathy: Fibrillation potentials/positive sharp waves OR chronic MUAP changes in a myotomal distribution (EMG evidence of denervation changes) Normal SNAP (as would be expected following a preganglionic lesion) Possible F-wave abnormalities The following are electrodiagnostic criteria for entrapment neuropathy: Conduction slowing at the site of compression or conduction block A decrease in distal SNAP amplitude (axonal loss) or a slowing of the SNAP (demyelination) Evidence of denervation on EMG in muscles supplied by the affected nerve. 2.10 Data Collection A common data collection form was employed to document: Demographic data (Age, Gender, Affected side, Hospital) Symptom distribution, duration and relevant history Eligible for use are the following NCS parameters: amplitudes, latencies, conduction velocities, F-waves. EMG findings Final clinical diagnosis Imaging results (where available) 2.11 Statistical Analysis SPSS version 25.0 was used for the analysis of data. The results of the continuous variables were expressed as mean ± standard deviation, and the categorical variables were expressed as frequency and percentages. The tests used for making between group comparisons were independent sample t-test for continuous variables and chi-square test for categorical variables. NCS and EMG were analyzed for sensitivity, specificity, positive predictive value and negative predictive value. A p-value <0.05 was considered statistically significant. 2.12 Ethical Considerations Institutional Review Boards (IRB) approval of the study protocol was obtained from Ayub Medical College and CMH Abbottabad. All participants provided written informed consent before participating. Confidentiality was respected with the patients on the study.

Table 1 shows the demographic and clinical features of the study population (100 patients).

*Statistically significant (p<0.05)

Table 2: Final Diagnosis Distribution (n=100)

Table 3: Electrodiagnostic Findings in Radiculopathy vs Entrapment Neuropathy

*Statistically significant (p<0.05)

Table 4: Diagnostic Performance of NCS and EMG in Radiculopathy and Entrapment Neuropathy

This study is an extensive systematic analysis of the diagnostic role of nerve conduction studies in diagnosing radiculopathy from entrapment neuropathy and a comparison of electrodiagnostic practice between two tertiary care hospitals in Abbottabad. The results offer significant information about the advantages and disadvantages of electrodiagnostic testing in both of these common neurological disorders. The mean age of our study group was 47.3 ± 12.8 years, which is similar to the typical age of presentation in clinical practice, where males predominate (58%). This marked difference in duration of symptoms at ATH (10.2 ± 7.1 months) and CMH (7.2 ± 4.8 months, p=0.017) may be due to differences in referral patterns and health care-seeking at the two hospital types. While the number of patients at ATH may lead to delays in accessing specialist care, it is possible that the structured referral system at CMH could lead to earlier electrodiagnostic evaluation.

Diagnostic breakdown showed that our population was almost equally divided between a diagnosis of radiculopathy (52%) and entrapment neuropathy (48%).(19) The most prevalent radiculopathy subtype was lumbosacral radiculopathy (34 cases) which matched the epidemiological studies of Pakistan that 65.7% of chronic pain patients with LBP had pain in their lumbar spine.(20) The most frequent entrapment neuropathy was carpal tunnel (28 cases) and this is the most common peripheral neuropathy in the world.(21)

The most important result of this study relates to the different electrodiagnostic patterns in the two. The percentage of patients with SNAP abnormalities was significantly higher in entrapment neuropathy (85.4%) patients than in radiculopathy (11.5%) patients (p<0.001).(22) This remarkable difference is consistent with the basic electrophysiology knowledge that preganglionic lesions (radiculopathy) have normal sensory nerve action potentials while peripheral nerve (distal to the dorsal root ganglion) entrapment has SNAP abnormalities.(8) Our results corroborate the study by Fayaz A et al., which showed that nerve conduction studies recorded epidurally in radiculopathy were normal.(23)

The diagnostic performance metrics offer additional insight into the complementary use of NCS and EMG in these settings.(24) NCS alone was less sensitive (11.5%) but highly specific (85.4%) for the diagnosis of radiculopathy, indicating that a positive NCS supports another diagnosis but a normal NCS does not preclude the diagnosis of radiculopathy.(25) The EMG alone had a sensitivity of 84.6% for radiculopathy, and the addition of the NCS to EMG resulted in a sensitivity of 86.5% and a specificity of 87.5% in our study. These findings suggest that EMG is an important tool in the diagnosis of radiculopathy and that NCS is only used in order to exclude associated entrapment neuropathies and/or polyneuropathy.(26)

In the case of entrapment neuropathy, the NCS had a high diagnostic value for both sensitivity (91.7%) and specificity (96.2%).(27) This is similar to the combined EMG/NCs pooled sensitivity and specificity value of 0.89 and 0.77 respectively in the diagnosis of carpal tunnel syndrome reported by El-Najjar AR et al.(28) In our study, the higher specificity could be due to the use of thorough NCS protocols such as across-elbow stimulation for cubital tunnel syndrome, which has been shown to have a dramatic effect on the diagnostic sensitivity. According to a study of 118 patients with cubital tunnel syndrome, use of the AANEM guidelines and calculation of motor nerve conduction velocity across the elbow improved the sensitivity for clear diagnosis of CBTS from 11.7% to 87.5%.(29) The high localization rate of entrapment neuropathies (91.7%) corroborates the localization value of NCS in these diseases.(30) There were a number of significant differences between the use of electrodiagnostics by ATH and CMH. The overall diagnostic distribution of the two hospitals is similar with lower rates of NCS abnormality detected in the CMH (52% of cases vs 44% in ATH). This difference could be due to the presentation of the disease, with a tendency to present earlier in the disease course for CMH which may lead to earlier conduction abnormalities being identified. Another possible reason for this discrepancy is electrodiagnostic technique and/or interpretation criteria being different at both institutions.(31) The increased EMG use at ATH (78.4% vs 58.3%) may reflect a greater dependence upon the use of needle examination for the diagnosis of radiculopathy, possibly owing to differences in equipment availability or physician training.(32)

The results of our study have implications for clinical practice. For one thing, the high specificity of NCS for entrapment neuropathy makes it the most important localizing diagnostic test for these disorders. Second, NCS alone has a poor sensitivity for radiculopathy, further confirming the need for needle EMG to achieve a good assessment of suspected radiculopathy. Third, the complementary nature of NCS and EMG is apparent from the fact that the combined use of both modalities improves the diagnostic accuracy. These results support evidence-based reviews of the utility of EMG in screening and differential diagnosis for suspected cervical and/or lumbosacral radiculopathy, which state EMG is highly useful.(33,35) Further improvements to diagnostics can be made using emerging technologies. The advantages of ultrasound such as patient comfort and the direct visualization of nerve anatomy has increased the use in the diagnosis of entrapment neuropathy.(34.36) Research has shown that there is a strong correlation between motor nerve conduction velocity slowing and the ulnar nerve cross-sectional area on ultrasound in CTS, with a 70.83% sensitivity and 66.67% specificity at the cut-off value of ≥11 mm². There are some limitations however, and ultrasound cannot at this time be used to replace NCS and EMG, especially for cases in doubt or as a secondary test. Future studies need to investigate how ultrasound can be used in conjunction with electrodiagnostic testing in our population.

In entrapment neuropathies, nerve conduction studies are very sensitive and specific and have a definite localizing value; in radiculopathy, on the other hand, the SNAP is preserved and the study is not of much value alone. Needle electromyography is still a critical part of diagnosing radiculopathy, and the NCS/EMG is the best test to make a diagnosis for both radiculopathy and needle electromyography. The finding of differences in electrodiagnostic practice between Ayub Teaching Hospital and CMH Abbottabad emphasizes the importance of standardizing electrodiagnostic practice and establishing inter-institutional cooperation to maximize the diagnostic yield.

Limitations

There are some limitations of this study that should be taken into account. The cross-sectional design did not allow the assessment of longitudinal changes as well as treatment results, and thus restrict the assessment of the prognostic value of the electrodiagnostic parameters. The use of clinical diagnosis as a reference standard and imaging as a reference standard may have introduced verification bias because not all patients had surgery confirmation of their diagnosis. The number of patients in each group (n = 100) was satisfactory for a comparative analysis, but restricted subgroup analyses for any individual nerve or grade. In addition, the electrodiagnostic testing was carried out by various physicians in the two hospitals, adding interrater variability in technique and interpretation.

Recommendations

Prospective designs with surgical confirmation as the gold standard should be used in future to confirm the diagnostic accuracy of NCS and EMG in our population. There is a need for consistency in electrodiagnostic protocols and reporting parameters across institutions in order to maintain consistent electrodiagnostic quality. AANEM guidelines should be stressed during training of electrodiagnostic technologists and physicians, especially for cubital tunnel syndrome, where the sensitivity for that condition increases dramatically with good technique. Lastly, the potential of using ultrasound as an adjunct to electrodiagnostic testing should be explored in resource-limited environments in which full-length NCS and EMG might not be available.