Cold elbow syndrome: spurious slowing of ulnar nerve conduction velocity

Low temperature decreases nerve conduction velocity (NCV). The across-elbow segment of the ulnar nerve is superficial and may be particularly susceptible to decreased temperature. We evaluated patients without clinical ulnar neuropathy at the elbow (UNE) but with isolated slowing of the across-elbow ulnar NCV (normal group), and patients with clinical and electrodiagnostic findings of UNE (UNE group). All subjects had ulnar motor nerve studies completed before and after warming. The mean across-elbow NCV was 43.4 m/s and 48.6 m/s (P < 0.0001) in the normal group, and 37.4 m/s and 37.7 m/s (P = 0.90) in the UNE group, before and after warming, respectively. There was no change in the forearm segment NCV in either group. Seventeen of 32 subjects in the normal group had completely normal studies after warming. No patients with UNE developed normal across-elbow NCV with warming. Low temperature slows across-elbow ulnar NCV in normal subjects without impact on the forearm segment. Warming of the elbow improves across-elbow ulnar NCV in normals, but does not reverse the abnormalities in patients with UNE. Elbow warming should become a routine part of ulnar nerve conduction studies, especially when there is isolated conduction slowing in the across-elbow segment.     

Which motor nerve conduction study is best in ulnar neuropathy at the elbow?

There is debate regarding how best to utilize ulnar motor nerve conduction velocity (MNCV) to identify ulnar neuropathy at the elbow (UNE). We used receiver operator characteristic (ROC) curves to compare absolute across-elbow MNCV with MNCV difference between elbow and forearm segments (VDIF) when recording from abductor digiti minimi (ADM) and first dorsal interosseous (FDI) muscles. Also, we determined how their utility was impacted by low amplitudes of compound muscle action potentials (CMAPs). We studied 85 subjects with UNE and 77 subjects with carpal tunnel syndrome but without clinical evidence of UNE. The UNE group was divided into three subgroups based on CMAP amplitude. At 95% specificity, MNCV sensitivities were 80% at ADM and 77% at FDI, and VDIF sensitivities were 51% at ADM and 38% at FDI. The ROC curves showed MNCV to be superior to VDIF across all amplitude subgroups; however, confidence intervals overlapped when amplitude was high.     

Short-segment nerve conduction studies in ulnar neuropathy at the elbow

The aim of the study was to assess the diagnostic value of short-segment nerve conduction studies (NCS) at 2-cm intervals from 4 cm above to 4 cm below the medial epicondyle in a large group of patients with ulnar neuropathy at the elbow (UNE). Furthermore, we wanted to compare electrodiagnostic and clinical findings. We evaluated 73 arms in 70 patients with UNE and observed the following abnormalities on short-segment NCS: focal conduction block (CB) in 1, focal CB with increased latency change in 34, and increased latency change alone in 25. Short-segment NCS had an additional localizing value in 28 arms of the 37 patients (76%) with motor conduction velocity (MCV) slowing across the elbow only or with nonlocalizing electrodiagnostic findings. The lesion was located above the elbow in 32 arms (53%), at the epicondyle in 16 arms (27%), and below the epicondyle in 12 (20%) of the 60 arms with focal CB or increased latency change on short-segment NCS. Patients with CB on routine and short-segment NCS had muscle weakness significantly more often than patients without CB. Thus, short-segment NCS are useful in localizing the lesion in patients with UNE and CB on routine NCS and have additional diagnostic value in patients with MCV slowing across the elbow or with nonlocalizing signs on routine nerve conduction studies. We recommend its use in all patients in whom UNE is suspected.     

Electrodiagnosis of ulnar neuropathy at the wrist: conduction block versus traditional tests

BACKGROUND: Compared to ulnar neuropathy at the elbow (UNE), ulnar neuropathy at the wrist (UNW) is rarer and more difficult to localize with routine electrophysiologic studies. METHODS: By stimulating the ulnar nerve at the wrist and palm, and recording from first dorsal interosseous (FDI), the sensitivity and specificity of conduction block (CB) and slow conduction velocity (CV) of FDI fibers across the wrist was compared to traditional electrodiagnostic techniques for localization of UNW. Twenty patients with clinically defined UNW (due mainly to wrist trauma), 30 normal controls, and 20 disease controls with severe (n = 10) and mild (n = 10) UNE were evaluated prospectively. The upper (mean +2.5 SD) and lower (mean -2.5 SD) limits for all measurements were derived from the normal controls. RESULTS: The UNW patients showed: slow wrist-palm FDI CV (<37 m/s) in 16 (80%); definite or probable CB in 14 (70%); prolonged distal latency (DL) to FDI (>4.5 milliseconds) in 12 (60%), to ulnar-innervated palmar interosseous (PI) versus median-innervated lumbrical (L) in 12 (60%), and to abductor digiti minimi (ADM) in 11 (55%). However, only CB and slow wrist-palm FDI CV (<37 m/s) were specific for UNW; prolonged DL to FDI was found in 4 patients (40%), to ADM in 4 patients (40%), and to PI in 1 patient (10%) with severe UNE. Overall, CB or slow wrist-palm FDI CV was present in 19 patients with UNW (95%). EMG failed to differentiate UNW from UNE, because forearm ulnar-innervated muscles were typically normal in UNW, but also often normal in mild UNE. CONCLUSIONS: In UNW, an additional palmar stimulation site improves electrodiagnostic yield, and demonstrates that CB is an important cause of muscle weakness.     

Changes in nerve conduction velocity across the elbow due to experimental error

One diagnostic criterion for ulnar nerve mononeuropathy at the elbow (UNE) is a decrease in across-elbow nerve conduction velocity (NCV) > 10 m/s compared to the forearm segment. Distance and latency measurement errors are an inherent part of NCV calculations. Twenty electromyographers measured the latencies of stored ulnar compound muscle action potentials and measured the forearm and across-elbow distances along the ulnar nerve. Based on previously published equations, experimental error in NCV was calculated for various NCVs. The mean distances and standard deviations for the forearm and elbow segments were 212.5 +/- 2.1 mm and 86.7 +/- 4.2 mm, respectively. For an NCV of 55 m/s, a difference of 14 m/s between the two segments can occur from measurement error alone. Distance measurements about the elbow are fraught with interobserver errors rendering the resultant NCV of that segment of limited value as a sole criterion for the diagnosis of UNE.     

IN-RATIO: a new test to increase diagnostic sensitivity in ulnar nerve entrapment at elbow.

OBJECTIVE: Motor conduction velocity may yield false-negative results in mild ulnar nerve entrapment at elbow (UNE). There is evidence that the clinical heterogeneity of UNE may be due to the different involvement of fascicles. We hypothesized that, if fibres to FDI are more damaged than fibres to ADM, a relative slowing of motor conduction velocity (CV) at the segment across the elbow recording from FDI (FDI-CV) versus CV at the same segment recording from ADM (ADM-CV) would occur. METHODS: We calculated the ratio between FDI-CV and ADM-CV (IN-RATIO) in 60 consecutive UNE patients, 40 norms, and 16 patients with lower cervical radiculopathy. The UNE sample consisted of (1) patients with neurophysiological evidence (UNE NF+), (2) patients without neurophysiological evidence (UNE NF-). We evaluated the possible usefulness of the IN-RATIO to increase sensitivity in diagnosing UNE. RESULTS: The IN-RATIO was lower in the UNE NF- than in norms (p<0.001) and cervicobrachialgia sample (p=0.02). We found that if the IN-RATIO is 相似文献   

Focal cooling improves neuronal conduction in peroneal neuropathy at the fibular neck.

Heat can induce conduction block (CB) in demyelinated neurons; whether cooling can reverse CB and increase strength is uncertain. In six patients with electrophysiologic evidence of peroneal neuropathy at the fibular neck with definite motor CB, standard motor nerve conduction studies were performed at 32 degrees C and then after the fibular neck region was cooled with an ice pack to 8 degrees -12 degrees C. In all patients, cooling increased the amplitude and area of the compound motor action potential obtained with popliteal fossa stimulation, decreasing the relative amplitude drop across the fibular neck from a mean of 78% to 55%. A concomitant increase in foot dorsiflexor strength was clearly observed in three of the six patients. Both the electrophysiologic and clinical changes readily reversed upon rewarming. These data support the belief that, in compressive neuropathies, cooling relieves conduction block in selected motor neurons, improving strength.     

Pseudofacilitation: A temperature-sensitive phenomenon

With sustained isometric exercise, compound muscle action potential (CMAP) amplitude of normal subjects may increase, a phenomenon known as pseudofacilitation. To explore the mechanism of pseudofacilitation, the effect of exercise combined with focal heating and cooling of abductor pollicis brevis was examined in 10 normal subjects. After 10 s of isometric exercise, CMAP amplitude increased by 3.6% (median value) at 32 degrees C and 6.4% at 40 degrees C, and decreased by 9.1% at 20 degrees C. Duration decreased by 12.6% at 32 degrees C and 11.7% at 42 degrees C, but increased by 12.4% at 20 degrees C. Area decreased by 9.8% at 32 degrees C and 8. 6% at 42 degrees C, and increased by 1.1% at 20 degrees C. Changes with cooling were significant (P < 0.01) as compared to baseline (32 degrees C); changes with heating were not. Thus, cooling reverses the expected increase in CMAP amplitude normally seen with exercise. Although providing only indirect evidence, these findings are consistent with the hypothesis that increased activity of muscle Na(+),K(+)-pump plays a role in producing pseudofacilitation.     

尺神经复合肌肉动作电位改变在吉兰-巴雷综合征和慢性炎性脱髓鞘性周围神经病中的特点

目的：探讨节段和短段刺激尺神经后不同节段复合肌肉动作电位（CMAP）负波各参数变化及传导阻滞在吉兰-巴雷综合征（GBS）和慢性炎性脱髓鞘性周围神经病（CIDP）中的意义。方法：20例GBS和12例CIDP患者行尺神经5点分段刺激（腕、肘下、肘上、腋和Erb＇s点）和短段刺激，记录CMAP负波波幅、时程和面积的变化，分析各参数与临床肌力的相关性。结果：在GBS中，尺神经CMAP负波的时程、波幅和面积的变化在Erb’s点到腕部的各节段中差异很大；波幅与面积的衰减与临床肌力呈高度相关（r=-0.905和-0.907）；传导阻滞多见于近端和肘部，时程离散不明显。在CIDP中，各节段中的参数变化差异不大；远端波幅与临床肌力相关（r=0.586）；传导阻滞在各节段均可出现，常伴明显的时程延长。结论：GBS和CIDP中尺神经CMAP负波的波幅、面积和时程3个参数，可从电生理角度帮助我们认识脱髓鞘疾病的特点。     

Electrodiagnosis of ulnar neuropathy at the elbow (Une): A bayesian approach

Introduction: In ulnar neuropathy at the elbow (UNE), we determined how electrodiagnostic cutoffs [across‐elbow ulnar motor conduction velocity slowing (AECV‐slowing), drop in across‐elbow vs. forearm CV (AECV‐drop)] depend on pretest probability (PreTP). Methods: Fifty clinically defined UNE patients and 50 controls underwent ulnar conduction testing recording abductor digiti minimi (ADM) and first dorsal interosseous (FDI), stimulating wrist, below‐elbow, and 6‐, 8‐, and 10‐cm more proximally. For various PreTPs of UNE, the cutoffs required to confirm UNE (defined as posttest probability = 95%) were determined with receiver operator characteristic (ROC) curves and Bayes Theorem. Results: On ROC and Bayesian analyses, the ADM 10‐cm montage was optimal. For PreTP = 0.25, the confirmatory cutoffs were >23 m/s (AECV‐drop), and <38 m/s (AECV‐slowing); for PreTP = 0.75, they were much less conservative: >14 m/s, and <47 m/s, respectively. Conclusions: (1) In UNE, electrodiagnostic cutoffs are critically dependent on PreTP; rigid cutoffs are problematic. (2) AE distances should be standardized and at least 10 cm. Muscle Nerve 49 :337–344, 2014     

Apparent conduction block in patients with ulnar neuropathy at the elbow and proximal Martin-Gruber anastomosis

A Martin-Gruber anastomosis (MGA) commonly results in an abnormal decline in amplitude across the forearm segment when ulnar motor nerve conduction studies are performed. A recent report described a proximal MGA resembling partial conduction block in a patient with ulnar neuropathy at the elbow (UNE). As a result, we screened patients with similar findings. We detected a proximal MGA in three patients over a period of 2 years, which suggests that this may be an under-recognized anomaly. We conclude that a proximal MGA must be excluded in all cases of UNE showing apparent partial conduction block across the elbow segment.     

Heat sensitivity of sensory fibers in carpal tunnel syndrome

Elevations in temperature may produce conduction block in demyelinated neurons. A well‐described phenomenon in multiple sclerosis, it has also been reported in some patients with inflammatory demyelinating polyneuropathies. We used carpal tunnel syndrome (CTS) as a model to study the effect of heat on nerves with focal demyelination secondary to chronic compression. Compound motor and sensory responses were measured in 12 CTS patients and 12 normal subjects at 32°C and with heating to 42°C. Changes in relative motor response amplitude and area were similar for both normal subjects and CTS patients. In CTS patients, however, sensory response amplitude and area decreased 34.3% and 48.9%, significantly more than the 25.2% and 39.1% reductions in normal subjects (P = 0.021 and P = 0.018 respectively). We hypothesize that these reductions in response amplitude are secondary to the occurrence of heat‐induced conduction block in demyelinated sensory neurons. © 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 37–42, 1999     

Effect of heating on nerve conduction in carpal tunnel syndrome.

The effect of temperature on normal nerves is well known, i.e., an increase in conduction velocity and a decrease in amplitude with an elevation in temperature. There are few reports examining the effect of temperature on abnormal nerves, e.g., in demyelination. To study the effect of increased temperature on demyelinating nerves in entrapment syndromes, the authors investigated 55 median and 48 ulnar nerves of 48 patients with carpal tunnel syndrome, and 48 median and 48 ulnar nerves of 26 healthy subjects. All measurements were obtained at 32 degrees C and 37 degrees C. Mean reductions in median sensory amplitude occurring with heating were significantly greater in the patient group than in the control group (P = 0.000). For median sensory response amplitude, the mean decrease was 32.1% in patients with carpal tunnel syndrome and 10.7% in the control subjects. The difference between median and ulnar nerves in the latency was significantly decreased (P = 0.027) after the nerves had heated to 37 degrees C. It is concluded that the elevation in temperature leads to conduction block in demyelinated sensory nerves, and that temperature provocation may be useful in the diagnosis of nerve disorders. The effect may be different in axonal and demyelinating disorders.     

Prognostic indicators from electrodiagnostic studies for ulnar neuropathy at the elbow

Introduction: We examined the prognostic value of electrodiagnostic (EDX) studies for ulnar neuropathy at the elbow (UNE). Methods: In this retrospective study, EDX results were compared with subjective recovery (resolution of symptoms) and surgery in patients diagnosed with UNE. Results: Of the 193 patients, 59 with “definite” UNE were included in the analysis. The combination of conduction block across the elbow to the first dorsal interosseous (FDI) and normal distal compound muscle action potential (CMAP) amplitude from the abductor digiti minimi (ADM) was strongly associated with recovery: 86% of these subjects achieved full subjective recovery compared to only 7% without conduction block and with an abnormal CMAP. There were no EDX predictors of surgery. Conclusion: EDX results contain useful prognostic information in UNE. Muscle Nerve, 2011     

Effect of body mass index on ulnar nerve conduction velocity, ulnar neuropathy at the elbow, and carpal tunnel syndrome

Both high and low body mass index (BMI) have been reported as risk factors for ulnar neuropathy at the elbow (UNE), and a high BMI as a risk factor for carpal tunnel syndrome (CTS). To determine whether the extremes of BMI are risk factors for UNE or CTS, and whether BMI affects calculation of median and ulnar motor nerve conduction velocity (NCV), we retrospectively analyzed the electrodiagnostic records of control patients, UNE patients, and CTS patients. The BMI was calculated for 50 patients with a sole diagnosis of UNE and compared to the BMI of 50 patients with CTS and 50 control subjects. The mean BMIs were 25.9 +/- 4.4, 30.1 +/- 5.5, and 28.3 +/- 5.6 for the UNE, CTS, and controls, respectively. By one-way analysis of variance, the difference in BMI between the UNE patients and the normal patients was significant (P < 0.01). In the control groups, increasing BMI directly correlated with increasing ulnar motor NCV across the elbow but not with forearm NCV. Across-elbow (AE) ulnar motor NCV may be falsely increased in patients with a high BMI, probably due to distance measurement factors. Not only do relatively slender individuals have comparatively slower AE ulnar NCVs, they are also at increased risk for developing UNE. Patients with a high BMI are at increased risk for CTS.     

Short segment sensory nerve stimulation in suspected ulnar neuropathy at the elbow: A pilot study

Introduction: Routine ulnar nerve conduction studies may be normal in very mild ulnar neuropathies at the elbow (UNE). Short segment ulnar sensory stimulation across the elbow may detect mild abnormalities in these cases. Methods: Short segment ulnar sensory nerve stimulation was performed in 20 controls and 15 patients with clinically suspected mild UNE. Greatest peak latency shift and amplitude drop between 2 adjacent stimulation sites were calculated. Results: The upper limit of normal for peak latency shift and amplitude reduction between sites was 0.7 ms and 15%, respectively. Abnormal latency shift was detected in 12 of 15 patients and focal sensory conduction block in 6 of 15 patients. In 5 of 7 patients in whom all other studies were normal, sensory inching was abnormal. Discussion: Ulnar sensory short segment stimulation may provide diagnostic confirmation and localization of the site of nerve compression in mild UNE, and may improve UNE detection when all other studies are normal. Muscle Nerve 59 :125–129, 2019     

Clinical, electrodiagnostic, and sonographic studies in ulnar neuropathy at the elbow

The aim of this study was to determine possible correlations between the clinical characteristics, electrophysiological features, and sonographic ulnar-nerve diameter in patients with ulnar neuropathy at the elbow (UNE). We prospectively performed clinical, electrodiagnostic, and sonographic studies in 102 patients having either purely sensory signs (35%) or sensorimotor signs (65%) of UNE. Nerve conduction studies had a sensitivity of 78%, and the addition of sonography increased this to 98%. The diagnostic value of both tests was not different among cases with and without motor deficit. Motor studies with recording from the abductor digiti minimi and first dorsal interosseous muscles were equally sensitive for the detection of conduction block or velocity slowing across the elbow, but the combination yielded more positive cases than when only one study was performed. There were modest negative correlations between the electrodiagnostic parameters and the sonographic ulnar-nerve diameter. Electrodiagnostically and sonographically, there were no significant differences between clinically pure sensory and mixed sensorimotor cases of UNE, except for electrodiagnostic findings suggesting loss of motor axons in cases with motor signs. Almost half the patients with only sensory signs had electromyographic evidence of motor axonal loss. We conclude that, although UNE is clinically heterogeneous, the electrophysiological and sonographic findings are fairly consistent despite the clinical manifestations.     

Expert consensus on the combined investigation of ulnar neuropathy at the elbow using electrodiagnostic tests and nerve ultrasound

The addition of ultrasound (US) to electrodiagnostic (EDX) tests can significantly enhance the accuracy of testing for ulnar neuropathy at the elbow (UNE). We aimed to obtain expert consensus to guide clinicians on the combined use of EDX and US in UNE investigation.Consensus was achieved using the Delphi method. Two consecutive anonymised questionnaires were submitted to 15 experts, who were asked to choose their level of agreement with each statement. Consensus was pre-defined as ≥ 80% rating agreement.The experts concluded that all investigations of UNE should include both nerve conduction studies and US. There was consensus that US should include cross-sectional area measurement and assessment of nerve mobility at the elbow, and that the entire ulnar nerve should be imaged.This study defined expert opinion on the ‘core’ techniques that should be used routinely in the UNE investigation using EDX and US. Areas with lack of consensus highlighted some controversial issues in the current use of these diagnostic modalities and the need for future research.This document is an initial step to guide clinicians on the combined investigation of UNE using EDX and US, to be regularly updated as new research emerges.     

Utility of magnetic resonance imaging in diagnosing ulnar neuropathy at the elbow.

OBJECTIVE: Magnetic resonance imaging (MRI) of the ulnar nerve is being increasingly employed in the diagnosis of ulnar neuropathy at the elbow (UNE). Our aims were to: (i) assess the sensitivity of MRI in diagnosing UNE, especially in cases where neurophysiologic studies were non-localizing, (ii) determine the spectrum of MRI abnormalities in patients presenting with symptoms and signs of ulnar neuropathy, (iii) assess whether MRI findings differ between grades of UNE severity, and (iv) to see if MRI findings give an input into the pathological mechanisms of UNE. METHODS: Clinical, neurophysiologic, and radiologic (MRI) records were reviewed in 52 patients with symptoms and signs of ulnar neuropathy. Ulnar nerve MRI studies were assessed by an unblinded observer. RESULTS: The sensitivity of MRI at diagnosing UNE was higher than conventional nerve conduction studies, 90 versus 65%, respectively. In patients with non-localizing neurophysiologic studies (n=19), MRI disclosed changes consistent with UNE in 16 (84%) cases. The most frequent MRI findings included a combination of high signal intensity and nerve enlargement (63%), followed by nerve compression (27%) and isolated high signal intensity (23%), and isolated nerve enlargement (2%). There was no significant difference between patients with localizing and non-localizing neurophysiologic testing. Lastly, there were no differences between different grades of UNE, suggesting that UNE may be a neurophysiologically heterogeneous disorder. CONCLUSIONS: MRI studies proved to be more sensitive than conventional nerve conduction studies at diagnosing UNE. In addition, the MRI studies were highly sensitive in patients with non-localizing UNE. SIGNIFICANCE: Our study shows that MRI of the ulnar nerve should be used in patients with clinical features of UNE especially in those with non-localizing neurophysiologic testing.     

The evaluation of suspected ulnar neuropathy at the elbow. Normal conduction study values

Local compression of the ulnar nerve occurs at several points, with the elbow region being the most common. Nerve conduction studies can be useful in identifying and localizing such lesions; however, the specifics of the technique, including normal values, have not been firmly established. We evaluated the effect of elbow position on segmental conduction velocities (CVs), the influence of elbow, nerve segment length on CV calculations, the change in compound action potential amplitude at sites along the nerve, and the use of performing segmental sensory CVs. Conductions done with the elbow flexed produced less segment-to-segment CV variation than those obtained with the elbow extended. The influence of using overlapping nerve segments compared with short adjacent ones for segmental CV comparison is discussed.