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Single-fiber EMG: A review.

Selvan VA - Ann Indian Acad Neurol (2011)

View Article: PubMed Central - PubMed

Affiliation: Walton Center for Neurology and Neurosurgery, Lower Lane, Fazakerley, L9 7LJ, Liverpool, UK.

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Single fiber electromyography (SFEMG) was established by Stalberg and Eskedt in the 1960s, and is of proven value in the diagnosis of neuromuscular disorders, especially myasthenia gravis... Errors may be encountered if this is higher and may produce a false jitter... In patients with myasthenia gravis, jitters are greater in the weak muscles, but they are also increased in muscles with normal strength... Extensor digitorum communis is usually tested first, unless symptoms or signs are limited to extraocular muscles when orbicicularis oculi or frontalis are tested... Jitter is increased in myasthenia gravis, but it does not correlate well with disease severity... In a few cases, SFEMG was performed before and after remission of myasthenia... Although the mean jitter values had decreased, some pairs still showed abnormalities, indicating that SFEMG did not normalize completely... Single fiber electromyography is highly sensitive, but not specific to the diagnosis of myasthenia and myasthenic syndromes... It must be emphasised that increased jitter values are not pathogonomic for myasthenia, but indicate disturbed neuromuscular transmission... However, it is also true that if SFEMG is normal in a weak muscle, it almost completely excludes the diagnosis of myasthenia... Single fiber electromyography is the most sensitive test to demonstrate an impaired neuromuscular transmission like myasthenia gravis... However, it must be emphasized that it is not specific, as SFEMG can be abnormal in other myopathic and neuropathic disorders... The test is safe, but technically demanding for both the patient and the neurologist performing it... It needs considerable experience and technical expertise.

No MeSH data available.


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Single fiber EMG recordings: (a) Normal; (b) Increased; Jitter (c) Blocking both increased jitters, and blocking is seen in the neuromuscular disorders. (With permission from EMG and Neuromuscular Disorders, Preston and Shapiro; Butterworth - Heinemann)
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Figure 0008: Single fiber EMG recordings: (a) Normal; (b) Increased; Jitter (c) Blocking both increased jitters, and blocking is seen in the neuromuscular disorders. (With permission from EMG and Neuromuscular Disorders, Preston and Shapiro; Butterworth - Heinemann)

Mentions: When neuromuscular transmission is sufficiently impaired, nerve impulses fail to elicit an action potential and this is called ‘blocking’ [Figure 8]. This usually happens when the jitter value is markedly prolonged, usually when MCD is more than 100 microseconds.[5]


Single-fiber EMG: A review.

Selvan VA - Ann Indian Acad Neurol (2011)

Single fiber EMG recordings: (a) Normal; (b) Increased; Jitter (c) Blocking both increased jitters, and blocking is seen in the neuromuscular disorders. (With permission from EMG and Neuromuscular Disorders, Preston and Shapiro; Butterworth - Heinemann)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108086&req=5

Figure 0008: Single fiber EMG recordings: (a) Normal; (b) Increased; Jitter (c) Blocking both increased jitters, and blocking is seen in the neuromuscular disorders. (With permission from EMG and Neuromuscular Disorders, Preston and Shapiro; Butterworth - Heinemann)
Mentions: When neuromuscular transmission is sufficiently impaired, nerve impulses fail to elicit an action potential and this is called ‘blocking’ [Figure 8]. This usually happens when the jitter value is markedly prolonged, usually when MCD is more than 100 microseconds.[5]

View Article: PubMed Central - PubMed

Affiliation: Walton Center for Neurology and Neurosurgery, Lower Lane, Fazakerley, L9 7LJ, Liverpool, UK.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

Single fiber electromyography (SFEMG) was established by Stalberg and Eskedt in the 1960s, and is of proven value in the diagnosis of neuromuscular disorders, especially myasthenia gravis... Errors may be encountered if this is higher and may produce a false jitter... In patients with myasthenia gravis, jitters are greater in the weak muscles, but they are also increased in muscles with normal strength... Extensor digitorum communis is usually tested first, unless symptoms or signs are limited to extraocular muscles when orbicicularis oculi or frontalis are tested... Jitter is increased in myasthenia gravis, but it does not correlate well with disease severity... In a few cases, SFEMG was performed before and after remission of myasthenia... Although the mean jitter values had decreased, some pairs still showed abnormalities, indicating that SFEMG did not normalize completely... Single fiber electromyography is highly sensitive, but not specific to the diagnosis of myasthenia and myasthenic syndromes... It must be emphasised that increased jitter values are not pathogonomic for myasthenia, but indicate disturbed neuromuscular transmission... However, it is also true that if SFEMG is normal in a weak muscle, it almost completely excludes the diagnosis of myasthenia... Single fiber electromyography is the most sensitive test to demonstrate an impaired neuromuscular transmission like myasthenia gravis... However, it must be emphasized that it is not specific, as SFEMG can be abnormal in other myopathic and neuropathic disorders... The test is safe, but technically demanding for both the patient and the neurologist performing it... It needs considerable experience and technical expertise.

No MeSH data available.


Related in: MedlinePlus