Электромиография в диагностике дистальной полинейропатии

[EVP]

Уважаемые коллеги, появилась интересная статья, где указывается на важность и необходимость включения ЭНМГ (NCS) в комплекс диагностики при дистальных полинейропатиях, в т.ч. и при сахарном диабете.

Distal symmetric polyneuropathy:
A definition for clinical research

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Report of the American Academy of Neurology, the American Association of Electrodiagnostic Medicine, and the American Academy of Physical Medicine and Rehabilitation

J.D. England, MD; G.S. Gronseth, MD; G. Franklin, MD, MPH; R.G. Miller, MD; A.K. Asbury, MD;
G.T. Carter, MD; J.A. Cohen, MD; M.A. Fisher, MD; J.F. Howard, MD; L.J. Kinsella, MD; N. Latov, MD;
R.A. Lewis, MD; P.A. Low, MD; and A.J. Sumner, MD

Abstract—The objective of this report was to develop a case definition of distal symmetric polyneuropathy to standardize and facilitate clinical research and epidemiologic studies. A formalized consensus process was employed to reach agreement after a systematic review and classification of evidence from the literature. The literature indicates that symptoms
alone have relatively poor diagnostic accuracy in predicting the presence of polyneuropathy; signs are better predictors of polyneuropathy than symptoms; and single abnormalities on examination are less sensitive than multiple abnormalities in predicting the presence of polyneuropathy. The combination of neuropathic symptoms, signs, and electrodiagnostic
findings provides the most accurate diagnosis of distal symmetric polyneuropathy. A set of case definitions was rank ordered by likelihood of disease. The highest likelihood of polyneuropathy (useful for clinical trials) occurs with a combination of multiple symptoms, multiple signs, and abnormal electrodiagnostic studies. A modest likelihood of polyneuropathy
(useful for field or epidemiologic studies) occurs with a combination of multiple symptoms and multiple signs when the results of electrodiagnostic studies are not available. A lower likelihood of polyneuropathy occurs when electrodiagnostic studies and signs are discordant. For research purposes, the best approach to defining distal symmetric
polyneuropathy is a set of case definitions rank ordered by estimated likelihood of disease. The inclusion of this formalized case definition in clinical and epidemiologic research studies will ensure greater consistency of case selection.
NEUROLOGY 2005;64:199–207

Electrodiagnostic studies. No single reference standard defines distal symmetric polyneuropathy.
The most accurate diagnosis of distal symmetric polyneuropathy comprises a combination of clinical symptoms, signs, and electrodiagnostic findings. Electrodiagnostic findings should be included as part of the case definition since they provide a higher level of specificity for the diagnosis.4,5,12,17

Electrodiagnostic studies are sensitive, specific, and validated measures of the presence of polyneuropathy. 3-5,8,12,16,17,20,21
Electrodiagnostic evaluations commonly include both nerve conduction studies (NCSs) and needle EMG. In the diagnosis of polyneuropathy, NCSs are the most informative part of the electrodiagnostic evaluation.5,8,12,16,17,20,21
NCSs are noninvasive, standardized, and provide a sensitive
measure of the functional status of sensory and motor nerve fibers.
NCSs are also widely performed and suitable for population studies or longitudinal evaluations. The inclusion of NCSs in the assessment of polyneuropathy adds a higher level of specificity to the diagnosis.4,5,12,17 For these reasons, NCSs are included as an integral part of the case definition of polyneuropathy.

The protocol for performing NCSs was determined by the structured consensus process described previously. There are many previous recommendations regarding NCS criteria for the diagnosis of poly-neuropathy,
but no formal consensus exists. The recommendations that follow are based on electrophysiologi principles that combine both the highest sensitivity and specificity as well as the highest efficiency for the diagnosis of distal symmetric polyneuropathy.

Recommended protocol for nerve conduction studies.

The following set of sensory and motor NCSs should be performed if patients are entering a clinical research trial in which NCSs will be tracked longitudinally. This protocol includes unilateral studies of
sural sensory, ulnar sensory, and median sensory nerves, and peroneal, tibial, median, and ulnar motor nerves with F waves. Other NCSs may be necessary as determined by clinical judgment. The minimum case definition criterion for electrodiagnostic confirmation of distal symmetric polyneuropathy
is an abnormality (
99th or 1st percentile) of any attribute of nerve conduction in two separate nerves,one of which must be the sural nerve. Electrodiagnostic studies should follow rigorous guidelines such as those set by the AAEM.22 Variables such as skin temperature, age, height, sex, and weight should be measured and accounted for when reporting a NCS as normal or abnormal.22 A simplified NCS protocol may be used for the purpose of defining the presence of distal symmetric polyneuropathy. However, the abbreviated protocol is not sufficient to determine the subtype or severity
of the polyneuropathy. For these purposes as well as for clinical trials in which electrodiagnostic measures will be tracked serially, the more comprehensive set of NCSs is recommended.

The simplified NCS protocol is as follows:
1. Sural sensory and peroneal motor NCSs are per-formed in one lower extremity. Taken together, these NCSs are the most sensitive for detecting a distal symmetric polyneuropathy. If both studies are normal, there is no evidence of typical distal symmetric polyneuropathy. In such a situation, no further NCSs are necessary.
2. If sural sensory or peroneal motor NCSs are abnormal, the performance of additional NCSs is recommended. This should include NCS of at least the ulnar sensory, median sensory, and ulnar motor nerves in one upper extremity. A
contralateral sural sensory and one tibial motor NCS may also be performed according to the discretion of the examiner. Caution is warranted when interpreting median and ulnar studies since there is a possibility of abnormality due to compression of these nerves at the wrist or ulnar neuropathy at the elbow.
3. If a response is absent for any of the nerves studied (sensory or motor), a NCS of the con-tralateral nerve should be performed.
4. If a peroneal motor response is absent, an ipsi-lateral tibial motor NCS should be performed.
Minimal criteria for the electrodiagnostic confir-mation of distal symmetric polyneuropathy are the same as listed previously.
Combining evidence and consensus: case definition of distal symmetric polyneuropathy.
The best approach to defining distal symmetric polyneuropathy is an ordered set of definitions ranked by likelihood of disease. The likelihood of distal symmetric polyneuropathy was rated on an ordinal scale from highest likelihood to lowest likelihood . Since diagnostic certainty for polyneuropathy follows a continuum of probability, this manner of definition is the most sensible. In each set of case definitions, a hierarchy of parameter combinations was established to provide the most relevant combinations for the diagnosis of distal symmetric polyneuropathy.
Combinations of parameters that were considered clinically unusual and not appropriate for research studies were not included. For these reasons not every possible combination of parameters is presented.

The essential characteristics of the case definition are contained in tables 1 and 2.
Important aspects of the case definition that warrant emphasis are the following:
1. The combination of neuropathic symptoms, signs, and abnormal electrodiagnostic studies provides the most accurate diagnosis of distal symmetric polyneuropathy
2. Electrodiagnostic studies are recommended as part of the clinical research case definition since they are objective and validated tests of peripheral nerve function. Abnormal electrodiagnostic studies increase the likelihood
of the presence of distal symmetric polyneuropathy and provide a higher level of specificity to the case definition. Electrodiagnostic studies should not be used alone to make the diagnosis since their sensitivity and specificity are not perfect.
3. Electrodiagnostic studies are not required for field or epidemiologic studies, but the likelihood of diagnosis must be downgraded accordingly.
4. For research studies enrollment should be lim-ited to cases that are most likely to have distal symmetric polyneuropathy (i.e., those that achieve the highest specificity for the diagnosis).
For clinical research studies, this consists of cases with an ordinal likelihood of ++++ . For epidemiologic studies, this consists of cases with an ordinal likelihood of++ .