The Second Lumbrical–Interosseous Latency Comparison in Carpal Tunnel Syndrome

Electrodiagnostic Testing for Carpal Tunnel Syndrome When Routine Median Sensory and Thenar Motor Responses Are Absent

PURPOSE

The cardinal symptoms of carpal tunnel syndrome (CTS) include pain in the affected hand(s). The median/second lumbrical nerve (Med2ndL) seems relatively preserved in severe CTS, with previous small studies suggesting its value in electromyogram to localize a median neuropathy to the wrist when both initial routine sensory and thenar motor responses are absent.

METHODS

This is a retrospective analysis of 208 hands in 183 patients with electrophysiologically markedly severe CTS (absent routine sensory and thenar motor median responses) who underwent stimulation of both the Med2ndL and ulnar/second dorsal interosseous (Uln2ndDIn) motor nerves. A Med2ndL distal latency of ≥ 0.5 milliseconds when compared with the Uln2ndDIn supported the diagnosis of CTS. The presence or absence of hand pain was recorded if these data were available.

RESULTS

Some 83.7% of hands (172/208) in 183 patients with markedly severe CTS had preservation of the Med2ndL meeting criteria for CTS. In those with pain data available, 77.1% (81/105) of hands had no pain. Of those 105 hands, 87 had preservation of the Med2ndL with 79.3% (69/87) demonstrating no pain.

CONCLUSIONS

This is a large study that demonstrates the relative preservation of the Med2ndL response in markedly severe CTS. Assessment of the Med2ndL should be considered to electrophysiologically support CTS when routine sensory and thenar motor responses are absent. In addition, most patients with electrophysiologically markedly severe CTS had no pain.

The sensitivity of median versus ulnar palmar mixed nerve study in the early diagnosis of carpal tunnel syndrome

Background

Electrodiagnostic tests (EDX) are the most frequent and applicable studies in early diagnosis of carpal tunnel syndrome (CTS), but the definitive sensitive and specific tests are still under study. We aimed to evaluate the role of the median versus ulnar palmar mixed nerve study (Mix M-U), and its sensitivity in comparison to other provocative comparison studies, in supporting the early diagnosis of CTS. This cross-sectional study included 142 idiopathic early CTS hands from 100 patients and 71 hands from 50 healthy subjects as a control group. We did routine median motor and sensory studies and 4 comparative tests namely median versus radial sensory study (MVR), Mix M-U, median versus ulnar sensory study (MVU), and median versus ulnar lumbrical-interossei motor study (LU-IN).

Results

The routine median motor and sensory latency and amplitude showed a statistically significant difference between CTS and control groups as (p< 0.05) and a highly statistically significant difference between the 2 groups as regards the 4 comparative tests as (p< 0.0001). The specificities of all the 4 comparative tests were higher than 90%. MVR test had the highest sensitivity (92.2%) and followed by Mix M-U study (82.2%) and MVU (78.7%), and the least sensitive test was the LM-IN (66.9%).

Conclusions

Although the patients’ results fall within the normal range according to the reference range in the literature, it showed a statistically significant difference when compared to controls. A high percentage of those symptomatic patients showed results of typical CTS when tested with the comparative studies so there is a need to use these sensitive tests to diagnose cases with early CTS. According to sensitivity studies, the selection of which tests to do in order is a challenging choice. For the diagnosis of cases with early CTS with a normal ordinary motor and sensory studies, MVR comparative technique appeared as the best sensitive and specific provocative electrophysiological test followed by the Mix M-U test. We recommend the use of a combination of both tests first in the diagnosis of early CTS and if one of them was negative we can use the other comparative studies MVU and then LM-IN studies.

Carpal tunnel syndrome in rheumatoid arthritis patients: the role of combined ultrasonographic and electrophysiological assessment

Background

Carpal tunnel syndrome (CTS) is known as one of the most common neurological extra-articular manifestations in rheumatoid arthritis (RA) patients. Studies on CTS in RA depend mostly on electrophysiological assessment. Few studies have used ultrasonography for evaluation of the local causes with much focus on wrist arthritis and tenosynovitis as the main cause of entrapment neuropathy of the median nerve in RA. The aim of our study is to assess the local causes of carpal tunnel syndrome in rheumatoid arthritis patients by ultrasonography and whether inflammatory or anomalous variations could affect decision-making and patient management.

Results

Carpal tunnel syndrome was diagnosed in 71 out of 74 examined RA wrists by nerve conduction studies (NCSs) and was categorized from minimal to severe according to Padua et al.’s (Ital J Neurol Sci 18:145–50, 1997) grading criteria. Median nerve CSA at the level of the carpal tunnel inlet and flattening ratio showed statistically significant relation with CTS severity. Bifid MN was found in 20 wrists (10 mild CTS wrists and 10 moderate CTS wrists), a persistent median artery was found in 4 wrists with moderate CTS, and an accessory muscle bundle was present in 3 wrists (2 mild CTS and 1 moderate CTS). The majority of the examined hands (85.1%) showed flexor tendon tenosynovitis at the wrist level and radio-carpal joint synovitis. The US7-joint score using GSUS7 & PDUS7 for synovitis, tenosynovitis and erosions showed significant relation with patients’ disease activity by DAS28 score. Significant relations between CTS severity and the following nerve conduction studies’ parameters, median nerve distal motor latency (DML), motor/sensory NCV, peak sensory latency, amplitude of SNAP, and median-radial latency difference test, were observed.

Conclusion

Synovial inflammation and local causes of median nerve compression such as bifid median nerve, persistent median artery, and accessory muscle bundle are collectively contributing factors in the etiology of carpal tunnel syndrome in rheumatoid arthritis patients. Ultrasonographic visualization of these inflammatory and anomalous variations enables early detection of CTS and highlights the possibility of non-arthritic-related causes. Using the 7-joint ultrasound (US7) score for assessment of synovitis, tenosynovitis, and erosions in rheumatoid arthritis patients is of valuable role in reflecting inflammation and its relation to the development of CTS in RA patients.

Cerebellar glutamatergic system impacts spontaneous motor recovery by regulating Gria1 expression

Peripheral nerve injury (PNI) often results in spontaneous motor recovery; however, how disrupted cerebellar circuitry affects PNI-associated motor recovery is unknown. Here, we demonstrated disrupted cerebellar circuitry and poor motor recovery in ataxia mice after PNI. This effect was mimicked by deep cerebellar nuclei (DCN) lesion, but not by damaging non-motor area hippocampus. By restoring cerebellar circuitry through DCN stimulation, and reversal of neurotransmitter imbalance using baclofen, ataxia mice achieve full motor recovery after PNI. Mechanistically, elevated glutamate-glutamine level was detected in DCN of ataxia mice by magnetic resonance spectroscopy. Transcriptomic study revealed that Gria1, an ionotropic glutamate receptor, was upregulated in DCN of control mice but failed to be upregulated in ataxia mice after sciatic nerve crush. AAV-mediated overexpression of Gria1 in DCN rescued motor deficits of ataxia mice after PNI. Finally, we found a correlative decrease in human GRIA1 mRNA expression in the cerebellum of patients with ataxia-telangiectasia and spinocerebellar ataxia type 6 patient iPSC-derived Purkinje cells, pointing to the clinical relevance of glutamatergic system. By conducting a large-scale analysis of 9,655,320 patients with ataxia, they failed to recover from carpal tunnel decompression surgery and tibial neuropathy, while aged-match non-ataxia patients fully recovered. Our results provide insight into cerebellar disorders and motor deficits after PNI.

Comparison of the modified method and the median sensory-ulnar motor latency difference in the diagnosis of carpal tunnel syndrome

OBJECTIVES

This study aimed to compare the modified method and the median sensory-ulnar motor latency difference in the diagnosis of carpal tunnel syndrome.

METHODS

The study recruited the electromyography results of 105 hands of 60 patients who had a complaint of carpal tunnel syndrome (CTS) on the hand diagram. The average sensory-ulnar motor delay difference (MSUMLD) was determined by simple subtraction, and the modified method was calculated based on the results of the classic method. The modified method and the MSUMLD were compared according to their sensitivity and specificity in the diagnosis of CTS.

RESULTS

In this study, 54 hands were evaluated with a unilateral nerve conduction study (45 right; 9 left). A total of 23 hands with CTS and 31 hands without CTS were diagnosed electrophysiologically. The MSUMLD had 91.3% sensitivity and 93.5% specificity; however, the modified method showed 95.7% sensitivity and 96.8% specificity in the diagnosis of CTS. Moreover, the modified method had 100% sensitivity and specificity in the diagnosis of moderate CTS.

CONCLUSIONS

The modified method may have higher diagnostic accuracy than the MSUMLD for diagnosing CTS.

Motor Unit Number Estimation of the Second Lumbrical Muscle in Human Hand

The number of motor units of the lumbrical muscles in human hand has not been explored. The objective of this study was to fill this gap by estimating the number of motor units in the second lumbrical muscle. Compound muscle action potential scan of the second lumbrical muscle was performed in 12 healthy subjects, with 10 of them being tested on two separate occasions. Motor unit number estimation (MUNE) was derived from the MScanFit program. The average MUNE of the second lumbrical muscle was 41.6 ± 2.1 (mean ± standard error) from 12 subjects in the first test, and 42.0 ± 2.2 from 10 of the 12 subjects in the retest, demonstrating excellent measurement reliability. Findings of the study provide novel information about the motor unit number of the second lumbrical muscle in human hand. The relatively low motor unit number in the muscle can facilitate motor unit investigations, especially at high level muscle activation.

Diagnostic utility of median nerve CSA to ulnar nerve CSA ratio in the diagnosis of mild idiopathic carpal tunnel syndrome

Background

Ultrasonography (US) measurement of median nerve cross-sectional area (m-CSA) at pisiform is increasingly utilized in identification of carpal tunnel syndrome (CTS), but there is still no agreement about the ideal cut-off value to employ. The aim of the study was to explore whether the median CSA to ulnar CSA ratio at the level of pisiform may yield a more accurate diagnosis of CTS. The study included 50 patients with mild idiopathic CTS (ICTS), assessed clinically and by nerve conduction studies, and 50 matched controls. M-CSA, median nerve flattening ratio and swelling ratio (m-SR), palmer bowing, and median CSA to ulnar CSA ratio (m-CAS:u-CSA) were measured for patients and controls. The cutoff values for the US parameters for the diagnosis of ICTS were evaluated.

Results

Compared to the control group, the ICTS group had significantly higher m-CSA (p < 0.001), higher m-CSA:u-CSA ratio (p < 0.001), higher m-SR (p = 0.012, and higher palmar bowing (p < 0.001). Use of m-CSA cutoff value of 11.78 mm2 and CSA:u-CSA ratio cut-off point of 2.97 yielded the greatest sensitivity and specificity for the diagnosis of ICTS.

Conclusion

The m-CSA:u-CSA ratio is slightly superior to the m-CSA in the diagnosis of CTS in terms of sensitivity and specificity.

A study to further develop and refine carpal tunnel syndrome (CTS) nerve conduction grading tool

Background

The severity of carpal tunnel syndrome (CTS) may be categorised in a number of ways utilising one of a range of presently available grading tools. The grading systems proposed by Bland and Padua are the most commonly used, however, both have limitations, which are discussed in detail in this paper.

The aim of this research is to establish, using the best available evidence, a clinically appropriate revision of the current CTS nerve conduction grading tool, and to compare with existing grading tools used in UK Neurophysiology clinics. The revised scale is designed from a clinical physiologist perspective and based on the numerical values of nerve conduction findings.

The proposed revised grading system is based on more nuanced, descriptive categories, ranging from Normal to Early, Mild Sensory, Mild Sensory Motor, Moderate Sensory, Moderate Sensory Motor, Severe Sensory Motor, Extremely Severe Sensory Motor, and Complete absence.

Method

A total of 1123 patients (2246 hands) were included in this study, with the aim of evaluating the revised grading system. Data was collected based on the extensive and detailed grading systems previously described by Bland and Padua. All data was recorded numerically to ensure methodological reliability.

Result

Of the 2246 patients’ hands tested, the nerve conduction was graded as normal in 968 hands; nerve conduction showed early changes in 271 hands; mild sensory changes in 215 hands, mild changes in both motor and sensory response in 51 hands; moderate sensory changes in 134 hands; moderate sensory and motor changes in 356 hands; severe changes in motor and sensory responses in 204 hands; extremely severe sensory and motor changes in 33 hands and complete absence of response in 14 hands.

Conclusion

The revised grading tool could offer a more numerical grading to the Clinical Physiologist and could help the surgeon to ascertain the level of severity in order to decide on either a conservative or surgical approach to treatment if they decide to use the proposed grading which could support them to defend their decision in cases of litigation.

Lumbrical-interosseous recording technique versus routine electrodiagnostic methods in the diagnosis of carpal tunnel syndrome

Objectives

We aimed to evaluate the sensitivity of second lumbrical-interosseous (L-I) technique and to compare the results with other electrophysiological methods in patients with carpal tunnel syndrome (CTS).

Patients and methods

This cross-sectional study was conducted in an electrophysiology laboratory of a university hospital between January 2003 and January 2004. A total of 102 patients with CTS (174 hands) and 40 healthy controls (80 hands) were included. Median motor nerve conduction studies were obtained with recordings from the abductor pollicis brevis (APB), median sensory nerve conduction studies from digits I-III and at palm-wrist segment (P-W), median-ulnar sensory comparison at digit IV (M-U), and median-radial sensory comparison at digit I (M-R) were along with L-I technique.

Results

The highest sensitivities were found in the median sensory conduction velocity across the palm-wrist (88%), and digit I-wrist segments (80%), median motor distal latency over the APB (77%), and L-I study (76%). The specificities of conventional tests were higher than the sensitivity of L-I method (63%).

Conclusion

L-I method has a good diagnostic sensitivity in CTS; however, P-W, median sensory nerve conduction velocity at digit I and median distal motor latency are more sensitive than L-I method. Therefore, L-I method can be applied as a supportive technique in the evaluation of patients with CTS.

Diffusion-weighted MR neurography of median and ulnar nerves in the wrist and palm

OBJECTIVES

To investigate the feasibility of diffusion-weighted magnetic resonance neurography (DW-MRN) in the visualisation of extremity nerves in the wrist and palm.

METHODS

Thirty-two volunteers and 21 patients underwent imaging of the wrist and palm on a 3-T MR scanner. In all subjects, two radiologists evaluated the image quality on DW-MRN using a four-point grading scale. Kappa statistics were obtained for inter-observer performance. In volunteers, the chi-squared test was used to assess the differences in nerve visualisation on DW-MRN and axial fat-suppressed proton density weighted imaging (FS-PDWI).

RESULTS

In volunteers, the mean image quality scores for the median nerve (MN) and ulnar nerve (UN) were 3.71 ± 0.46 and 3.23 ± 0.67 for observer 1, and 3.70 ± 0.46 and 3.22 ± 0.71 for observer 2, respectively. The inter-observer agreement was excellent (k = 0.843) and good (k = 0.788), respectively. DW-MRN provided significantly improved visualisations of the second and the third common palmar digital nerves and three branches of UN compared with FS-PDWI (P < 0.05). In patients, the mean image quality scores for the two observers were 3.24 ± 0.62 and 3.10 ± 0.83, inter-observer performance was excellent (k = 0.842).

CONCLUSIONS

DW-MRN is feasible for improved visualisation of extremity nerves and their lesions in the wrist and palm with adequate image quality, thereby providing a supplementary method to conventional MR imaging.

KEY POINTS

• DW-MRN provides adequate image quality for wrist and palm neurography • DW-MRN performs similarly to FS-PDWI in nerve visualisation at the wrist • DW-MRN provides improved visualisation of small nerves in the palm • DW-MRN serves as a supplementary method to evaluate peripheral neuropathies.

Diagnosis of Severe Carpal Tunnel Syndrome Using Nerve Conduction Study and Ultrasonography

This study investigated the correlation between nerve conduction study and ultrasonographic findings for assessment of the usefulness of ultrasonography in determining carpal tunnel syndrome severity. Hands of adults with carpal tunnel syndrome were assessed using ultrasound and nerve conduction studies and grouped according to median nerve cross-sectional area (CSA). There were significant differences (p < 0.01) in mean median nerve CSA between controls, patients with median sensory nerve conduction velocity ≤40 m/s and patients with absent sensory nerve action potential and between controls, patients with median nerve distal motor latency ≥4.5 ms and patients with absent compound muscle action potentials of the abductor pollicis brevis. This is the first report to define median nerve CSA cutoff values (18 mm(2)) for determining carpal tunnel syndrome severity in patients with absent compound muscle action potentials of the abductor pollicis brevis. Median nerve CSA values below the cutoff values should prompt clinicians to consider other disorders, such as cervical compressive myelopathy.

Ultrasound elastographic evaluation in the diagnosis of carpal tunnel syndrome: initial findings

The purpose of this study was to investigate ultrasound (US)- and US elastography-detected changes in the median nerve of patients with carpal tunnel syndrome (CTS). Seventy-four wrists of 41 female patients with CTS (mean age, 47.73 ± 11.45 y) and 45 wrists of 24 asymptomatic female controls (mean age, 42.83 ± 10.66 y) were examined with US and US elastography. Electromyography results confirmed the diagnosis of CTS in the patients. The mean median nerve perimeter (MN-P = 15.26 ± 2.18 mm) and median nerve cross-sectional area (MN-CSA = 11.81 ± 4.05 mm²) of patients with CTS were higher than those of controls (12.08 ± 1.54 mm and 7.76 ± 1.40 mm², respectively) (p < 0.05). Mean tissue strain was lower in the patients with CTS (0.094 ± 0.045 than in the controls (0.145 ± 0.068) (p < 0.05). The most sensitive cut-off value for tissue strain was 0.0635, and the most specific was 0.19. US and US elastography, in addition to electromyography, proved to be beneficial in the diagnosis of CTS. US elastography is a new technique that may well find a place in the diagnosis of nerve entrapment syndromes.