Motor unit action potential (MUAP) parameters affected by editing duration cursors

INTRODUCTION

Quantitative electromyography (QEMG) allows fast analysis of motor unit action potential (MUAP) parameters such as amplitude, duration, size index (SI), phases, turns and firing rate. When automated duration cursor placement is incorrect, the electrodiagnostician will manually edit this function potentially introducing bias to the final results.

OBJECTIVE

To identify that (1) size index is the MUAP parameter least affected by manually editing duration cursors and (2) MUAP amplitude will influence the manual cursor correction rate.

MATERIALS AND METHODS

Included were twenty-one consecutive patients who had QEMG with monopolar needle electrode for diagnostic evaluation of their myofascial pain symptoms. Evaluated for neck pain included 6 bilateral upper limb and cervical paraspinal muscles and for lower back pain were 5 bilateral lower limb and lower back muscles. Twenty MUAPs were recorded from each muscle and hardcopies of data obtained before and after manual edit.

RESULTS

Of a total of 5360 MUAPs analyzed 1764 (33%) required manual editing of duration cursors. Cursor correction rate 120 MUAP s/individual muscle analyzed was also similar at 33+/-17%. Percentage change in duration more so than turns, before and after correction, was significantly larger than that of other parameters. No significant differences in percentage changes noted between SI and phases.

CONCLUSIONS

SI and phases are least influenced by the manual correction of duration cursors since there is insubstantial amplitude and area at the tail-end of the MUAP.

Skill and selection bias has least influence on motor unit action potential firing rate/frequency

INTRODUCTION

Motor unit action potential (MUAP) rise time in quantitative electromyography (QEMG) using multi-MUAP analysis may influence neuromuscular disease diagnosis.

OBJECTIVE

To demonstrate in QEMG that MUAP firing rate/frequency (FR) is the parameter least dependent on electrodiagnostician skill (EDXc) skill and selection bias.

METHODS AND MATERIALS

During minimal contraction (< 6 MUAPs/4.8 s analysis period) of tibialis anterior, 20 MUAPs were selected for QEMG at each of the 3 insertion sites. There were three EDXcs (professor & two fellows), each an independent MUAP selector + EMG machine itself (EMGM), for a total of four independent MUAP selectors. EDXc and selector order variation at each site involved the following. At insertion site1, during EMG by EDXc 1, the MUAP selector order was EDXc 1, EMGM, EDXc 2 and EDXc 3. At the following two sites, the previous 1st selector was sequentially rotated to become the last selector during EMG by the subsequent EDXc. The protocol was repeated in two subjects. MUAP inclusion criteria by EDXcs was MUAP rise time < 1 ms by visual inspection and, by the EMGM, any and all MUAPs during the 4.8 s analysis period.

RESULTS

The reproducibility of measurements between MUAP selectors for mean frequency was satisfactory (correlation coefficient for inter-EDXc was 0.57, and 0.66 between the most experienced EDXc and EMGM. Inter- EDXc correlation coefficient was poor for amplitude (0.10), duration (0.34), size index (0.35), phases (-0.13) and turns (-0.22). Of the MUAPs collected by EMGM, the mean amplitude was smaller and mean duration was longer than those collected by the other 3 selectors with no significant differences for the other parameters.

CONCLUSIONS

FR was the only satisfactorily reproduced parameter from QEMG of MUAPs between selectors, and least dependent on skill and/or selection bias. From this, FR appears a relatively objective parameter, while other parameters appear unduly influenced by EDXc skill and/or MUAP selection bias.

Redistribution in I-123 N-isopropyl-p iodoamphetamine single-photon emission computed tomography in cerebrovascular disease and the effects of rehabilitation

We performed N-isopropyl-p (I-123) iodoamphetamine (IMP) single-photon emission computed tomography (SPECT) on 28 patients with severe cerebrovascular disease before rehabilitation, and compared the degree of redistribution and the assessment of activities of daily living (ADL). We calculated a redistribution (RD) ratio in the central and peripheral parts of the lesions: RD ratio (c) and RD ratio (p). We classified the patients into four groups based on the degree of redistribution: complete: both RD ratio (c) and (p) > or = 75; peripheral: RD ratio (c) < 75, RD ratio (p) > or = 75; incomplete: both RD ratio (c) and (p) < 75 and at least one of RD ratio (c) or (p) > or = 25; no redistribution: both RD ratio (c) and (p) < 25. We assessed the ADL using the modified Barthel index (BI). deltaBI was defined as BI after rehabilitation-BI before rehabilitation (BIpost-BIpre). The deltaBI of the four groups were as follows: complete-redistribution group (40.8 +/- 22.8), peripheral-redistribution group (40.0 +/- 15.8), incomplete-redistribution group (27.2 +/- 22.6), no-redistribution group (8.8 +/- 12.3). The deltaBI of the complete and peripheral redistribution groups were significantly higher than that of the no-redistribution group. However, deltaBI was almost the same in the complete- and peripheral-redistribution groups. This suggests that the effect of rehabilitation might be closely related to the viability of the peripheral part of the lesion.

[Relationship between redistribution rate (RD rate) of 123I-IMP SPECT and prognosis by Barthel index in cerebral infarction]

A comparative study of RD rate and the Barthel index was performed in 26 patients who had cerebral infarction. On 123I-IMP SPECT, the RD rate was calculated as follows, RD rate = (I-II)/I x 100(%). (I = (B-A)/B, where A is the mean count of the low density area (LDA) on brain CT on the early image and B the mean count of the opposite portion of LDA on the early image. II = (B'-A')/B', where A' is the mean count of the LDA on the delayed image and B' is the mean count of the opposite portion of the LDA on the delayed image. delta Barthel index (delta B. I.) was defined as follows: delta B. I. = B. I. (post-rehabilitation)-B. I. (pre-rehabilitation). In the group with B. I. (pre rehabilitation) < 85, the RD rate and delta B. I. were well correlated. In the group with B. I. (pre-rehabilitation) > or = 85, the RD rate and delta B. I. were not correlated. This result suggests that the RD rate might be useful in predicting prognosis and selecting the principle of therapy.