To examine the usefulness of the second lumbrical-interosseous (2L-INT) distal motor latency (DML) comparison test in localizing median neuropathy to the wrist in patients with absent median sensory and motor response in routine nerve conduction studies.
Electrodiagnostic results from 1,705 hands of patients with carpal tunnel syndrome (CTS) symptoms were reviewed retrospectively. All subjects were evaluated using routine nerve conduction studies: median sensory conduction recorded from digits 1 to 4, motor conduction from the abductor pollicis brevis muscle, and the 2L-INT DML comparison test.
Four hundred and one hands from a total of 1,705 were classified as having severe CTS. Among the severe CTS group, 56 hands (14.0%) showed absent median sensory and motor response in a routine nerve conduction study, and, of those hands, 42 (75.0%) showed an abnormal 2L-INT response.
The 2L-INT DML comparison test proved to be a valuable electrodiagnostic technique in localizing median mononeuropathy at the wrist, even in the most severe CTS patients.
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Objective: To obtain reference values of early potential latency and amplitude of pudendal SEP in Korean normal women and to correlate those values with height and age.
Method: Twenty-three normal female with mean age of 45.27 years were evaluated for pudendal SEP. Stimulation was applied on the dorsal aspect of the clitoris with a bar electrode. Onset, P1, N1, P2 latencies and P0-P1, P1-N1, N1-P2 amplitudes were measured and those of both sides were analyzed.
Results: The mean latency of P0, P1, N1, P2 were 29.0⁑2.83 msec, 35.5⁑2.91 msec, 45.1⁑4.10 msec, 56.3⁑5.20 msec by the right pudendal nerve, and 28.6⁑3.11 msec, 35.2⁑2.93 msec, 45.0⁑3.83 msec, 56.5⁑5.33 msec by the left pudendal nerve. The amplitude ranges of P0-P1, P1-N1, N1-P2 were 0.31∼2.45 uV, 0.11∼2.24 uV, 0.21∼2.62 uV by the right pudendal nerve, and 0.29∼2.46 uV, 0.25∼2.21 uV, 0.12∼5.07 uV by the left pudendal nerve. There was tendency of prolongation of the latency with increasing the height. There is no difference of amplitude according to the height and the age. There was no significant difference between right and left sides in mean latency and range of amplitude of pudendal nerve SEPs, and between premenopause and postmenopause.
Conclusion: Normal reference of female pudendal SEP were established. We suggest that pudendal SEP can be used as one of useful diagnostic tools for female urogenital and neurologic disease.
Objective: To investigate the reliability of distoproximal latency ratio of median sensory nerve as a diagnostic criterion of carpal tunnel syndrome (CTS) in patients with diabetic polyneuropathy.
Subject: Electrophysiologic study was performed in 264 hands of 208 patients with diabetes. Forty eight hands (24 subjects) without diabetes mellitus or CTS were included as a normal control group. Another 48 hands having CTS without diabetes mellitus were also included as a CTS control group.
Method: Clinical and electrophysiologic findings were included to detect carpal tunnel syndrome in patients with diabetic neuropathy. Sensitivity and specificity of various electrodiagnostic parameters to confirm clinical CTS were obtained.
Results: Diabetic neuropathy was diagnosed in 66.3%, and median neuropathy was diagnosed in 52.7%. CTS was found in 32.2% as determined by the distoproximal latency ratio. The sensitivity of distoproximal latency ratio as a diagnostic tool for CTS was the highest (95.1%) and the specificity was the second highest (51.3%) among 5 different electrodiagnostic criteria of CTS.
Conclusion: The results suggest that distoproximal latency ratio is an important parameter with high sensitivity in determining CTS in the patients with diabetic polyneuropathy.
This prospective study following American Association of Electrodiagnostic Medicine recommended criteria in the diagnosis of Carpal Tunnel Syndrome(CTS) evaluated the sensitivity of multi-electrodiagnostic parameters and usefulness of residual latency in CTS.
In 45 symptomatic hands of 26 patients with clinical diagnosis of CTS, 8 electrodiagnostic parameters-median motor distal latency, median motor residual latency, median sensory onset latency, median sensory peak latency, median to ulnar sensory onset latency difference(digit 4), median to ulnar sensory peak latency difference(digit 4), median to radial sensory onset latency difference(digit 1), median to radial sensory peak latency difference(digit 1)-were compared to the normative data obtained from the age-matched control group.
In 31 CTS hands without polyneuropathy, median to ulnar sensory latency difference(digit 4), median to radial sensory latency difference(digit 1), median sensory peak latency have same sensitivity(71.0%).
In 8 CTS hands with delayed proximal median motor nerve conduction velocity which were indiscernible from polyneuropathy in routine nerve conduction study, residual latency was more sensitive than median to ulnar sensory latency difference and median to radial sensory latency difference.
Sensitivity difference between sensory onset latency and sensory peak latency was negligible in the electrophysiologic diagnosis of CTS.
We concluded that residual latency measurement was a very useful and convenient method in the diagnosis of CTS, especially in the patients with delayed proximal median motor conduction velocity.
Objective: To determinate the reference values of residual latencies of motor nerves and to evaluate the early diagnostic value of residual latency.
Method: The subjects were 129 diabetes mellitus patients and 60 controls with no known neurological disorders. The patients were divided into two groups based on the conventional nerve conduction study: Group 1, 75 patients without neuropathy; Group 2, 54 patients with neuropathy. The group 2 patients were subdivided into 4 sub- groups on the basis of conduction velocity and residual latency of the median nerve. Residual latencies were measured in all subjects and glycosylated hemoglobin percentages (HbA1c) were measured in the diabetes patients. In group 2, each nerve conduction parameter was correlated with the duration of diabetes and HbA1c. The duration of diabetes, HbA1c, and amplitude of median nerve response were compared between the subgroups of group 2 patients.
Results: Motor residual latencies obtained from the controls were 1.93⁑0.28 msec, 1.53⁑0.24 msec, 2.46⁑0.43 msec, 2.21⁑0.53 msec in median, ulnar, deep peroneal and posterior tibial nerves, respectively. In group 1, motor residual latencies of median & deep peroneal nerves were significantly delayed compared with those of the controls. In group 2, motor residual latencies of median, ulnar, deep peroneal and posterior tibial nerves were significantly delayed more than those of the controls and group 1.
In group 2, increased HbA1c correlated to the decreased conduction velocities of median, deep peroneal, posterior tibial nerves but not to the residual latencies.
In the subgroup of group 2 (2-D), the nerve involved more distally showing lower compound muscle action potential and higher HbA1c.
Conclusion: Residual latency measurement can be a useful diagnostic method for the early detection of diabetic neuropathy.
Residual latency is the difference between the expected and measured terminal latencies in nerve conduction study. The main contributors to the residual latency are the nerve tapering in the hand and fingers and the neuromuscular delay. We measured median motor and sensory residual latencies in the controls and in patients with diabetes mellitus(DM) to establish the normal values, to evaluate the diagnostic value of the residual latency in diabetic polyneuropathy. we studied 50 healthy controls and 100 diabetic patients with or without polyneuropathy.
The normal residual latency values were 1.42⁑0.41 msec(mean⁑SD) in motor part and 0.44⁑0.20 msec in sensory part of median nerve. The standard deviation of residual latency in median motor nerve was decreased by 12% as compared with that of distal latency in the patient with diabetic polyneuropathy. Duration of DM and age were not related to the residual latency of median nerve.
The results suggest that the residual latency of median motor nerve provides a narrower normal range in the diagnosis of diabetic polyneuropathy irrespective of duration of DM or age.
This study was designed to verify the validity of bulbocavernosus reflex latency(BCRL) and pudendal somatosensory evoked potential(SEP) in the evaluation of neurogenic erectile dysfunction and to lay out a scheme to uplift the diagnostic accuracy of BCRL and pudendal SEP. Eighty four subjects who were referred to Seoul National University Hospital EMG laboratory for the evaluation of the erectile dysfunction were examined. At first, history taking, physical examination, measurement of serum hormone level, rigiscan with audiovisual sexual stimulation were performed. In the next step, intracorporial papaverine injection, nocturnal penile tumescence test, BCRL and pudendal SEP were performed as indicated. Then the results of BCRL and pudendal SEP were compared to the final diagnosis obtained through additional studies. Psychogenic cause was most common and neurogenic, vascular, and hormonal causes followed. The diagnostic sensitivity of BCRL and pudendal SEP in the discrimination of neurogenic cases from nonneurogenic cases was 89.5% and 93.7%, respectively. The specificity was 89.7% and 64.7% in order. Among twenty seven subjects with abnormal BCRL or pudendal SEP, eight subjects were confirmed as psychogenic impotence at the final diagnosis. But psychogenic impotence was not found among nine subjects who had abnormal BCRL and pudendal SEP. Twenty three subjects with abnormal BCRL were divided into delayed latency group and no response group. Among thirteen subjects of delayed latency group, psychogenic cases were six and among ten subjects of no response group, psychogenic case was not found. In the evaluation of neurogenic impotence, BCRL was a sensitive and specific tool while pudendal SEP was sensitive but less specific. BCRL alone or pudendal SEP alone would be inadequate for the evaluation of neurogenic impotence, especially in discrimination with psychogenic one. To improve diagnostic accuracy in the evaluation of impotence, BCRL and pudendal SEP should be checked out all together. In the situation when only BCRL is available, it is recommendable to take unevokable bulbocavernosus reflex as meaningful.
Objective: Absolute or relative increase in the latency of the major surface positive component is almost invariably found in patients with demyelination optic neuropathy. Using the pattern- reversal method, our study illustrates the significant changes in the latency of the P100 component when refractive errors are introduced to defocus in normal person.
Method: Four women and ten men aged 20 to 27 years were selected after a thorough ophthalmological assessment. Visual acuity (VA) was 6/6 or better in all subject and none had dyschromatopsia or significant astigmatism. Refractive errors were created by the combined standard lenses.
Results: The mean value of P100 latency were as follows: 93.74⁑3.30 msec, naked eyes; 98.14⁑7.37 msec, the 2/⁓90 lens; 96.50⁑3.76 msec, the 1/1⁓90 lens; 94.55⁑4.20 msec, the 1/1⁓90; 96.29⁑2.88 msec, the 2/2⁓90 lens. The P100 latencies showed singnificant standard lens except with 1/1⁓90 lens. The P100 latency was prolonged according to the progression of refractive error.
Conclusion: Because a relative or absolute prolongation of P100 latency is often found in cases of suspected multiple sclerosis, and because of their similarity to the findings of our study, we would emphasize that refractive errors should be reduced or eliminated to minimize the false-positive results.
Objective: Distance between the active and reference electrodes can affect the waveform configuration and amplitude of sensory nerve action potential (SNAP). This study was purposed to determine the change of SNAP parameters with varying interelectrode distance.
Metohod: Median sensory nerve conduction study was performed in the middle finger of 40 young healthy subjects by antidromic method. To ensure firm contact with skin, strip adhesive electrode was used for recording responses. The active electrode was fixed on 1 cm distal to the proximal flexion crease of middle finger and interelectrode separation was increased from 1 to 5 cm by 1.0 cm increments. Bar electrode was fixed 14 cm proximal from active electrode for stimulation in the wrist area.
Results: As the interelectrode distance increased from 1 cm to 5 cm, onset latency remained unchanged. The peak latency increased with increasing the distance up to 3 cm but didn't change beyond 3 cm (1 cm: 2.89⁑0.89 msec, 2 cm: 2.97⁑0.89 msec, 3 cm: 3.02⁑0.19 msec, 4 cm: 3.02⁑0.19 msec, 5 cm: 3.02⁑0.20 msec). Base-to-peak amplitude significantly increased only up to 3 cm (1 cm: 30.3⁑6.7μV, 2 cm: 43.7⁑8.6μV, 3 cm: 50.8⁑10.4μV, 4 cm: 51.1⁑10.9 μV, 5c m: 51.3⁑11.4μV) but peak-to-peak amplitude sequentially increased to 5 cm (1 cm: 49.6⁑12.1μV, 2 cm: 72.8⁑14.4μv, 3 cm: 83.6⁑19.4μV, 4 cm: 91.3⁑22.5μV, 5 cm: 93.4⁑23.9μV)(p＜.05).
Conclustion: This study showed that changing interelectrode distance altered some parameters of SNAP, especially the peak-to peak amplitude.
In diagnosis of carpal tunnel syndrome, there are many techniques with high sensitivity. Among them, the median-radial latency difference(MRLD) is one of the most useful technique in screening mild carpal tunnel syndrome with high sensitivity, no painful discomfort to patients and no motor artifact.
In this study, we examined the effect of the thumb position(radial abduction and adduction) on the MRLD. Because the stimulation sites of the median sensory and superficial radial nerves are different from each other, the free movement of the thumb in this examination is not avoidable.
The results are 1) there is no significant effect of the thumb position on median sensory latency. 2) There is no significant effect of the thumb position on superficial radial latency. 3) There is significant effect of the thumb position on MRLD(P<0.01). Therefore, if we diagnose the mild carpal tunnel syndrome with MRLD, the thumb position must be maintained in neutral position through the examination.
Objective: To explore the effects of different recording electrodes on motor nerve conduction latencies.
Method: Median motor conduction study was performed in 10 healthy subjects. Motor conduction latency was determined by placing different recording electrodes (surface disc, monopolar needle and concentric needle) at the motor point of the left abductor pollicis brevis muscle, and reference electrodes on the proximal interphalangeal joint of the thumb. Motor nerve conduction recording was performed by using a surface disc, monopolar needle, and concentric needle. For the intramuscular recordings, needles were inserted both superficially and deep. The stimulus electrodes were secured 8 cm proximal to the recording electrodes, and the same intensity was applied throughout the tests.
Results: Deep intramuscular monopolar and concentric needle electrodes recorded the shorter latencies, 3.0⁑0.4 ms and 3.0⁑0.3 ms, respectively. Superficial concentric needle electrode recorded the longest latency of 3.4⁑0.3 ms. Motor nerve conduction latencies using a surface disc and superficial monopolar electrode were 3.2⁑0.3 ms and 3.2⁑0.3 ms, respectively.
Conclusion: We conclude that the distal motor nerve conduction latency is variable depending on the type of recording electrodes.
Objective: To investigate the change of peak latency, interpeak latency and amplitude of auditory brainstem evoked potentials (AEPs) in normal preterm infants in accordance with the age, and to find out the correlation between reproducibility of AEPs and high risk of premature infants.
Method: AEP studies were performed on 266 premature infants (male 143, female 123) within a month of the birth. Acquired potentials were grouped by the reproducibility of waveforms, and latency, interpeak latency and amplitude were measured in each group of potentials to interpret age appropriate changes of AEPs.
Results: 1) Peak latency of peak I, III and V were shortened in accordance with the age, especially latency of peak V was significantly decreased from 7.42 msec to 6.84 msec. 2) There was no significant change in interpeak latency or amplitude of AEPs according to the postmenstrual age. 3) Reproducibility of AEPs was worse in premature infants with history of asphyxia.
Conclusion: Considering the results, the latency of peak V can be used as one of the useful parameter to investigate and follow up the premature infants. Significant negative correlation between low grade reproducibility and history of neonatal asphyxia was found.
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