Concentric needle jitter using different stimulation methods in extensor digitorum communis and orbicularis oculi in healthy subjects and myasthenic patients

Abstract

WCN 2013 No: 3160 Topic: 7 — Neuromuscular disorders Neuromuscular junction autoantibodies in seronegative myasthenia gravis patients from Sudan R.M. Badi, A.M. Musa, M. Elzubier, L. Jacobson, E. Khalil, A. Vincent, A.E. Ahmed. Physiology, Faculty of Medicine, University of Khartoum, Khartoum, Sudan; Medicine/Neurology, Faculty of Medicine, University of Khartoum, Khartoum, Sudan; Clinical Neuroscience, Oxford University, Oxford, UK; Institute of Endemic Diseases, University of Khartoum, Khartoum, Sudan; Physiology/Neurology, Faculty of Medicine, University of Khartoum, Khartoum, Sudan Background: In myasthenia gravis (MG) autoantibodies target neuromuscular junction (NMJ) proteins leading to a decreased sensitivity to ACh with muscle weakness. 80–88% of MG patients have AChR antibodies (AChR-Ab). It was suggested that AChR-Ab−ve patients may have autoantibodies against otherNMJ proteins or amore sensitive assay is required to detect AChR-Abs. Hoech et al. (2001) detected muscle specific kinase antibodies (MuSK-Abs) in 70% of AChR-Ab−ve generalized MG patients (GMG). Leite et al. (2008) detected clustered AChR-Abs by the cell based assay (CBA) in 66% of AChR-Ab−ve patients. A considerable proportion of MG patients remained seronegative (SN-MG). Objectives: To identify the nature of NMJ autoantibodies in AChRAb−ve MG patients from Sudan and to relate it to their clinical presentation. Patients and methods: 96 MG patients (77 GMG and 19 OMG) were randomly recruited from two national MG referral centers in Khartoum during the period 2010–2012. All patients were screened for AChR-Abs and MuSK-Abs by radioimmunoprecipitation assay (RIPA). Negative sera were screened for clustered AChR-Abs by the CBA. Results: 62.5% (60/96) of patients were AChR-Ab by RIPA. Of the 36 AChR-Ab−ve patients, 19.4% (7/36) were MuSK-Ab, and 22.2% (8/36) were clustered AChR-Ab. 21.9% (21/96) of patients remained SN-MG. MuSK-Ab patients (MuSK-MG) represented 25.9% (7/27) of AChR-Ab−ve GMG with a female:male ratio of 1.3:1 and dominant bulbar symptoms (85.7%,6/7). Clustered AChR-Ab patients were all females (n = 8). SN-GMG were predominantly females (92.9%, 13/14)(P = 0.02). The incidence of an associated autoimmune disease (AUID) in SN-GMG females was 53.8% (7/13) compared to 17.6% (6/34) in AChR-Ab GMG females (P b .013), RR (95% CI) = 3.05 (1.3–7.38). Conclusion: The incidence of MuSK-MG was within the reported detection rates (0–50%). The association between AUID and SN-GMG females suggests the involvement of sex and predisposition to autoimmune diseases in determining the pathogenicity in MG. doi:10.1016/j.jns.2013.07.1702 Abstract — WCN 2013 No: 3162 Topic: 7 — Neuromuscular disorders Concentric needle jitter using different stimulation methods in extensor digitorum communis and orbicularis oculi in healthy subjects and myasthenic patients WCN 2013 No: 3162 Topic: 7 — Neuromuscular disorders Concentric needle jitter using different stimulation methods in extensor digitorum communis and orbicularis oculi in healthy subjects and myasthenic patients A.M. Musa, A.E. Ahmed, M. Elzubeir, R.M. Badi. Physiology, Faculty of Medicine, University of Khartoum, Khartoum, Sudan; Physiology/ Neurology, Faculty of Medicine, University of Khartoum, Khartoum, Sudan; Society of Neurosciences, Faculty of Medicine, University of Khartoum, Khartoum, Sudan; Medicine/Neurology, Faculty of Medicine, University of Khartoum, Khartoum, Sudan Background: Single fibre electromyography (SFEMG) is the most sensitive clinical neurophysiological test for neuromuscular junction disorders, particularly myasthenia gravis (MG). Objectives: No available data concerning jitter measurement in Sudan in addition to scarcity of data worldwide. The study aimed at measuring jitter values, estimating conversion factor[CF] & comparing between the standard methods of stimulation [voluntary activation (V-) & axonal stimulation (S-)] using concentric needle (CN), testing extensor digitorum communis (EDC) & orbicularis oculi (OOc) muscles in the same individual [either control or patients with MG]. Methods: Prospectively 45 MG patients (21 males & 24 females, mean age 39.1 ± 16.9 years) & 62 controls (20 males & 42 females, mean age 43.2 ± 14.0 years) were studied. Jitter values were expressed as the mean consecutive difference (MCD) of 30 potential pairs in (μs). T-test was used for comparison. Results: In the control group the mean MCD, mean MCD for individual potential pairs & mean outlier jitter values (with upper 95% confidence limit—CL) for [V-EDC]were [27.5 ± 3.4 (33.5), 26.7 ± 9.0 (43.3)& 39.3 ± 5.1 (48.2) μs respectively], for [S-EDC]were [21.2 ± 2.9 (25.8), 21.0 ± 8.1 (35.9) & 32.6 ± 4.5 (39.6) μs respectively], for [V-OOc] were [26.9 ± 3.3 (32.0), 26.1 ± 8.9 (41.8)&38.5 ± 5.7 (49.0) μs respectively] & for [S-OOc] were [21.8 ± 2.4 (25.6), 21.5 ± 7.6 (35.3) & 32.4 ± 3.5 (37.5) μs respectively]. In the patient group the mean MCD & mean MCD for individual potential pairs for [V-EDC] were [46.8 ± 18.4, 44.2 ± 30.5 μs respectively], for [S-EDC] were [27.4 ± 10.4, 27.0 ± 19.0 μs respectively], for [V-OOc] were [50.9 ± 21.8, 48.8 ± 36.8 μs respectively] & for [S-OOc] were [42.9 ± 20.4, 38.5 ± 25.4 μs respectively]. V-EDC showed statistically significant higher MCD values than S-EDC in the controls [CF = 0.78] & patients [CF = 0.64]. V-OOc showed statistically significant higher MCD values than S-OOc in controls [CF = 0.82] but not statistically significantly higher than S-OOc in patients [CF = 0.92]. In the control group, comparison of the mean MCDs for [V-EDC/V-OOc] & [S-EDC/S-OOc] revealed no significant statistical difference. In the patients, comparison of the mean MCDs for [V-EDC/V-OOc] showed no significant statistical difference as well but revealed significant difference between [S-EDC and S-OOc]. Conclusion: The suggested practical upper limits for mean MCD & for outliers were (34, 49 μs) for V-EDC, (32, 49 μs) for V-OOc, (26, 40 μs) for S-EDC and (26, 38 μs) for S-OOc. The study is unique in that it compared between jitter values of the two standard techniques using CN in EDC & OOc muscles of the same subject [recruiting large number of controls & patients]. doi:10.1016/j.jns.2013.07.1703 Abstracts / Journal of the Neurological Sciences 333 (2013) e422–e480 e479