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- Title
EVALUATION OF MYOPATHIES.
- Authors
Rösler, Kai M.
- Abstract
The cardinal symptom of myopathies is muscle weakness. Electrodiagnostic testing (EDX) in myopathies aims to elucidate the origin of muscle weakness, i.e., if the disorder is myopathic or neurogenic. It may also serve to document the distribution of muscle weakness and the disease course. Nerve conduction studies are helpful in the work-up of muscle disorders. Sensory nerve conductions should be normal, and motor nerve conduction studies may demonstrate reduced stimulation responses corresponding to muscle wasting. Needle myography can be used to estimate the size of motor units. In muscle diseases, degeneration of muscle fibres causes motor unit potentials (MUPs) to decrease in size. In neuropathies, unaffected nerve fibres may reinnervate denervated muscle fibres, hence increasing MUP size. MUPs are quantified by quantitative myography. The patient performs a liminal muscle contraction, recruiting only few MUPs at once, which can be recognized and reproduced. This lengthyand cumbersome procedure may be examiner-dependent, since recognizing and sampling of MUPs is influenced by the examiners judgement. The sensitivity of classic "Buchthal"-MUP analysis to detect myopathy or neuropathy is low. Modern automated MUP detection methods attempt to simplify the procedure and to increase its reliability. Needle myography can also show abnormal recruitment patterns in muscle disease. In myopathies, voluntary activation generates early recruitment, and dense interference patterns of small amplitude. Neuropathies generate high amplitude patterns with reduced recruitment. Recruitment anomalies can be estimated semiquantitatively or using computerized analyses (e.g., "Willison-Analysis"). In this ENMG teaching course, the EDX techniques mentioned above will be described and reviewed. Their useful ness for the work-up of muscle disorders will be critically discussed.
- Subjects
MOTOR unit; MUSCLE weakness; MUSCLE diseases; NEURAL conduction; NEEDLES &; pins
- Publication
Neurologijos Seminarai, 2018, Vol 22, Issue 3, p258
- ISSN
1392-3064
- Publication type
Article