Electrical and mechanical responses in the platysma and in the adductor pollicis muscle: in patients with myasthenia gravis.

Krarup, Christian

doi:10.1136/jnnp.40.3.241

Cited by 32 publications

(9 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The PTF was larger in the platysma than in the ADP (Krarup 1977b) and similar in the elbow flexors and the ADP (Horowitz . This difference may be related to the fact that the amplitude of the action potential evoked before the tetanus was lower than normal in 10 of 24 patients in the platysma whereas it was within the normal range in the ADP ( Krarup 1977b and the elbow flexors of 31 patients (Horowitz . The rate of decay of the PTF was faster than that of the PTP and had disappeared 10-20 s after the tetanus (Krarup 1977b, Fig.…”

Section: Post-tetan Ic Faci I Itationmentioning

confidence: 96%

See 1 more Smart Citation

Evoked responses in normal and diseased muscle with particular reference to twitch potentiation

Krarup

1983

Acta Neurologica Scandinavica

View full text Add to dashboard Cite

The compound muscle action potential and isometric twitch tension evoked by single and repetitive electrical stimuli are indicators of the number of motor units activated and of the contractile properties of the muscle. The action potentials and mechanical responses were recorded in proximal and distal muscles in patients with myasthenia gravis and myopathy and compared with findings in normal subjects. In normal muscle, at low rates of stimulation (2-3 s-1) the decrement was at most 5% in the action potential and 15-24% in the twitch tension. Tetanic stimuli (50 s-1) were unsuitable for diagnostic purposes because of movement artefact. In patients with myasthenia gravis, the incidence and size of the decrement of evoked responses were greater in the platysma than in the elbow flexors and the adductor pollicis (ADP) muscles. The 2-3 times greater post-tetanic facilitation (PTF) of the action potential in the platysma than in extremity muscles also indicates a more severe functional block in facial muscle. The PTF is an indicator of recruitment of blocked fibres. The maximal decrement was grossly related to the titre of antibodies against the acetylcholine receptor. To reveal failure of neuromuscular transmission in patients with myasthenia gravis without a decrement, a small dose of d-tubocurarine (0.2 mg in 30 ml of saline) was injected i.v. in the upper arm in a regional curare test. The sensitivity was greater in patients with myasthenia gravis than in controls and in patients with myopathy. Potentiation of twitch tension reflects contractile properties. In normal muscle twitch potentiation in the staircase (1-3 s-1, 100 s in duration) and after tetanus (50 s-1, 1.5 s in duration) was 2-3 times greater in the platysma than in the elbow flexors and ADP, presumably related to the greater proportion of fast-twitch fibers in facial muscle. The amplitude of the action potential and the twitch tension varied proportionally with the number of fibers activated and the difference in the decrements of the action potential and the twitch during the staircase in some patients with myasthenia gravis showed that the staircase phenomenon was diminished suggesting abnormalities in the excitation-contraction coupling. The diminution of the staircase and post-tetanic potentiation (PTP) in myopathy also indicates impairment of the excitation-contraction coupling. In rats with severe chronic myasthenia gravis, the staircase and PTP were decreased even when the failing neuromuscular transmission was circumvented by applying direct stimuli to the extensor digitorum longus muscle (EDL).

show abstract

Section: Post-tetan Ic Faci I Itationmentioning

confidence: 96%

“…1968). We studied similar phenomena in proximal muscles (Krarup 1977b. For comparison we studied twitch potentiation in muscular dystrophy and other myopathies without abnormalities in neuromuscular transmission .…”

mentioning

confidence: 99%

Evoked responses in normal and diseased muscle with particular reference to twitch potentiation

Krarup

1983

Acta Neurologica Scandinavica

View full text Add to dashboard Cite

show abstract

“…2,16,19,22 Twelve hours was recommended as the length of time to withhold the medications. 16,19 One study did withhold medications from 4 to 18 h. 16,22 For LEMS, it was suggested that a screening test be performed to determine if RNS or SFEMG is needed. This involved recording and comparing a single pre-and postexercise supramaximal CMAP for differences in amplitude.…”

Section: Resultsmentioning

confidence: 99%

“…Krarup 16 compared RNS in a proximal muscle (platysma) to a distal muscle (adductor pollicis) in 24 patients with MG. He found that the decrement in the platysma with RNS was two to three times greater than in the adductor pollicis.…”

Section: Repetitive Nerve Stimulation Repetitive Nerve Stimulation Imentioning

confidence: 99%

“…Desmedt and Borenstein 5 Gilchrist and colleagues 8 Gilchrist, Massey, and Sanders 9 Grana, Chiou-Tan, and Jaweed 11 Kennett and Fawcett 15 Oh and colleagues 19 Oh and colleagues 20 Sanders, Howard, and Johns 25 Slomic, Rosenfalck, and Buchthal 28 Stålberg, Ekstedt, and Broman 30 Tim, Massey, and Sanders 31 Tim and Sanders 32 4 of 6 literature classification criteria met Blom and Rinqvist 1 Borenstein and Desmedt 2 Botelho and colleagues 4 Harvey and Masland 12 Harvey and Masland 13 Mayer and Williams 18 Ozdemir and Young 21 Ricker, Hertel, and Stodieck 22 Rivero and colleagues 23 Sanders and Howard 24 Sanders and Stålberg 26 Schwartz and Stålberg 27 3 of 6 literature classification criteria met Borenstein and Desmedt 3 Ekstedt 7 Krarup 16 Lambert and Elmquist 17 Stålberg 29 Trontelj, Khuriabet, and Mihelin 33 Trontelj and colleagues 34 Trontelj and Stålberg 35 Trontelj and colleagues 36 …”

Section: Of 6 Literature Classification Criteria Metmentioning

confidence: 99%

See 1 more Smart Citation

Literature review of the usefulness of repetitive nerve stimulation and single fiber EMG in the electrodiagnostic evaluation of patients with suspected myasthenia gravis or Lambert‐Eaton myasthenic syndrome

Chiou‐Tan¹,

Tim²,

Gilchrist³

et al. 2001

Muscle and Nerve

147

View full text Add to dashboard Cite

A retrospective literature review of the electrodiagnosis of myasthenia gravis (MG) and Lambert--Eaton myasthenic syndrome (LEMS) through July 1998 was performed for the purpose of generating evidence-based practice parameters. There were 545 articles identified, of which 13 articles met at least three of the six criteria set previously by the American Association of Electrodiagnostic Medicine (AAEM). An additional 21 articles were identified from review articles or the references of these first 13 articles leading to a total of 34 articles. Results of studies utilizing repetitive nerve stimulation (RNS) showed that a 10% decrement in amplitude from the first to fourth or fifth intravolley waveform while stimulating at 2--5 HZ is valid for the diagnosis of MG. The degree of increment needed for the diagnosis of LEMS is at least 25% but most accurate when greater than 100%. Abnormal jitter or impulse blocking are the appropriate criteria for diagnosis of neuromuscular junction (NMJ) disorders when using single fiber electromyography (SFEMG). SFEMG is more sensitive than RNS for the diagnosis of disorders of neuromuscular transmission, but may be less specific and may not be available. Therefore, RNS remains the preferred initial test for MG and LEMS.

show abstract

Rapid improvement of myasthenia gravis after plasma exchange

Nielsen

Paulson

Rosenkvist

et al. 1982

Annals of Neurology

View full text Add to dashboard Cite

Neuromuscular transmission and the staircase phenomenon in the adductor pollicis muscle were studied in six patients with myasthenia gravis before and 24 hours after single plasma exchanges given in short series over one to four weeks. An improvement in neuromuscular transmission was observed in all patients but one within 24 hours, suggesting that an immunological block of receptor sites is reversible or that acetylcholine receptors are rapidly resynthesized. In addition to a neuromuscular transmission defect, two of the patients also showed evidence of impaired excitation-contraction coupling with a negative staircase phenomenon and reduced posttetanic twitch potentiation. This condition became normal after plasma exchange, which may indicate that a reversible immunological impairment of the sarcoplasmic reticulum was present. Improvement lasted up to several months. The anti-acetylcholine receptor antibody titers were lowered in response to single plasma exchanges, but actual titer levels showed poor correlation with clinical and electrophysiological changes.

show abstract

Electrical and mechanical responses in the platysma and in the adductor pollicis muscle: in patients with myasthenia gravis.

Cited by 32 publications

References 19 publications

Evoked responses in normal and diseased muscle with particular reference to twitch potentiation

Evoked responses in normal and diseased muscle with particular reference to twitch potentiation

Literature review of the usefulness of repetitive nerve stimulation and single fiber EMG in the electrodiagnostic evaluation of patients with suspected myasthenia gravis or Lambert‐Eaton myasthenic syndrome

Rapid improvement of myasthenia gravis after plasma exchange

Contact Info

Product

Resources

About