Sciatic nerve fascicle differentiation on high-resolution ultrasound with histological verification: An ex vivo study.

INTRODUCTION/AIMS: The development of high-resolution ultrasound (HRUS) has enabled the depiction of peripheral nerve microanatomy in vivo. This study compared HRUS fascicle differentiation to the structural depiction in histological cross-sections (HCS). METHODS: A human cadaveric sciatic nerve was marked with 10 surgical sutures, and HRUS image acquisition was performed with a 22-MHz probe. The nerve was excised and cut into five segments for HCS preparation. Selected HCS were cross-referenced to HRUS, with sutures to improve orientation. Sciatic nerve and fascicle contouring were performed to assess nerve and fascicular cross-sectional area (CSA), fascicle count, and interfascicular distances. Three groups were defined based on HRUS fascicle differentiation in comparison to HCS, namely single fascicle (SF), fascicular cluster (FC), and no depiction (ND) group. RESULTS: On cross-referenced HRUS to HCS images, 58% of fascicles were differentiated. On HRUS, significantly larger fascicle CSA and smaller fascicle count were observed compared with HCS. Group analysis showed that 41% of fascicles were defined as SF, 47% as FC, and 12% as ND. The mean fascicle CSA in the ND group was 0.05 mm2. Compared with the SF, the FC had significantly larger fascicle CSA (1.2 ± 0.7 vs. 0.6 ± 0.4 mm2; p < .001) and shorter interfascicular distances (0.1 ± 0.04 vs. 0.5 ± 0.3 µm; p < .001). DISCUSSION: While HRUS can depict fascicular anatomy, only half of the fascicles visualized on HRUS directly correspond to single fascicles observed on HCS. The amount of interfascicular epineurium appears to influence the ability of HRUS to differentiate individual fascicles.

Clinical and neurophysiological recovery of ulnar nerve conduction block at the elbow.

INTRODUCTION/AIMS: An important mechanism of peripheral nerve motor and sensory dysfunction is conduction block (CB). However, recovery from mechanically induced CB has been rarely studied in humans. The aim of this study was to describe clinical, electrodiagnostic (EDx), and ultrasonographic (US) characteristics of CB recovery in ulnar neuropathy at the elbow (UNE). METHODS: We recruited a group of consecutive patients presenting to our EDx laboratory with UNE and >50% motor CB. Patients' histories were obtained and neurologic, EDx, and US examinations were repeated every 1-3 mo for at least 12 mo. RESULTS: We studied 10 patients (5 men), with a mean age of 63 y (range, 51-81 y). In all affected arms CB was localized to the retrocondylar groove. Following conservative management, myometrically measured index finger abduction improved from a median of 49% to 100% relative to the contralateral index finger, and ulnar nerve CB decreased from a median of 74% to 6%. Most of the improvement took place within 8 mo of symptom onset, and 6 mo after receiving treatment instructions. Mean motor nerve conduction velocity improved from 15 to 27 m/s in the most affected 2-cm ulnar nerve segment. DISCUSSION: The resolution of CB after typical chronic compression may take longer than after acute compression. This should be considered by clinicians when estimating prognosis for discussions with patients.

Median and ulnar nerve fascicle imaging using MR microscopy and high-resolution ultrasound.

BACKGROUND AND PURPOSE: Understanding nerve microanatomy is important as different neuropathies and some nerve neoplasms present with fascicle enlargement. The aim of our study was to gain clinically oriented knowledge on nerve fascicular anatomy using imaging modalities. METHODS: On a cadaveric upper extremity, high-resolution ultrasound (HRUS) scan with 22 MHz probe was performed. Sections of the median and ulnar nerves were excised at the level of the distal arm and after magnetic resonance microscopy (MRM), histological cross-sections (HCS) were prepared. Cross-referencing of the MRM and HRUS images with HCS was performed. Fascicle and nerve contouring was performed with morphometric software in order to assess nerve and fascicular cross-sectional area (CSA), fascicle count, and interfascicular distances. Based on fascicle differentiation, factual fascicle (FF) group and fascicular cluster (FC) group were defined. RESULTS: On the cross-referenced imaging material, fascicles were differentiated in 92.7% on MRM and in 57.3% on HRUS. High to very high positive correlation among imaging material was observed for the fascicle CSA. FF depiction was 30.1% on HRUS. In comparison to the FF group, the FC group had significantly larger fascicle CSA and shorter interfascicular distances. DISCUSSION: The findings of our study contribute to understanding of fascicle depiction on imaging modalities. HRUS offers good visualization of fascicles. The capability of differentiating fascicles is modality specific and depends on the fascicle CSA and the amount of interfascicular epineurium.

Ultrasound-guided injections in pelvic entrapment neuropathies.

Pelvic entrapment neuropathies represent a group of chronic pain syndromes that significantly impede the quality of life. Peripheral nerve entrapment occurs at specific anatomic locations. There are several causes of pelvic entrapment neuropathies, such as intrinsic nerve abnormality or inflammation with scarring of surrounding tissues, and surgical interventions in the abdomen, pelvis and the lower limbs. Entrapment neuropathies in the pelvic region are not widely recognized, and still tend to be underdiagnosed due to numerous differential diagnoses with overlapping symptoms. However, it is important that entrapment neuropathies are correctly diagnosed, as they can be successfully treated. The lateral femoral cutaneous nerve, ischiadic nerve, genitofemoral nerve, pudendal nerve, ilioinguinal nerve and obturator nerve are the nerves most frequently causing entrapment neuropathies in the pelvic region. Understanding the anatomy as well as nerve motor and sensory functions is essential in recognizing and locating nerve entrapment. The cornerstone of the diagnostic work-up is careful physical examination. Different imaging modalities play an important role in the diagnostic process. Ultrasound is a key modality in the diagnostic work-up of pelvic entraptment neuropathies, and its use has become increasingly widespread in therapeutic procedures. In the article, the authors describe the background of pelvic entrapment neuropathies with special focus on ultrasound-guided injections.

Differentiation of ulnar neuropathy at the wrist due to ganglion cyst from ulnar neuropathy at the elbow.

OBJECTIVE: Here, we aimed to describe the clinical, electrodiagnostic (EDx) and ultrasonographic (US) findings in a series of patients with ulnar neuropathy at the wrist (UNW) due to compression by a ganglion cyst. We also sought features that differentiate UNW from ulnar neuropathy at the elbow (UNE). METHODS: We reviewed electronic medical records of consecutive patients with UNW caused by ganglion cysts. We compared their clinical, EDx and US findings to findings in our previously reported prospective series of UNE patients. RESULTS: We identified 10 patients with UNW caused by ganglion cyst compression, who all presented with intrinsic hand muscle weakness and atrophy. Compared to 175 UNE patients they less often complained of paresthesia (60% vs. 98%) and presented less sensory loss in the palm (30% vs. 96%) and little finger (50% vs. 95%). They more often had distal ulnar motor latency recorded from the abductor digiti minimi (ADM)>3.6ms (80% vs. 30%), and denervation activity on needle EMG in the first dorsal interosseous (FDI) compared to ADM (100% vs. 60%). Only 20% of our UNW patients had ulnar nerve swelling at the site of compression on US. CONCLUSION: UNW potentially caused by ganglion cyst should be suspected in patients presenting with intrinsic hand muscle atrophy and weakness, particularly in cases with normal sensation, increased distal ulnar motor latency recorded from ADM and more severe neuropathic changes in FDI compared to ADM muscle.

Utility of nerve conduction studies and ultrasonography in ulnar neuropathies at the elbow of different severity.

OBJECTIVE: To report the sensitivity and the ability to precisely localize ulnar neuropathies at the elbow (UNE) of different severity by ultrasonography (US) and compare it to standard 10-cm nerve conduction studies (NCSs), and 2-cm short-segment NCSs (SSNCSs) across the elbow. METHODS: In a group of consecutive UNE patients, a prospective and blinded study was performed. The evaluation included clinical examination, electrodiagnostic (EDx) and US studies. We compared US and NCSs for sensitivity and the ability to precisely localize the UNE of different clinical severity. RESULTS: We studied 202 affected arms of 197 UNE patients. Clinically very mild UNE was diagnosed in seven, mild in 43, moderate in 99 and severe in 53 arms. The sensitivities of SSNCSs were 14%, 67%, 93% and 100%, of 10-cm NCSs, 29%, 44%, 80% and 96%, and of US 14%, 47%, 59% and 89%, respectively. Precise UNE localization was possible using SSNCSs in 29%, 56%, 78% and 85%, and using US in 29%, 44%, 70% and 98%, respectively. CONCLUSION: The present study demonstrated that NCSs are more sensitive than US for the diagnosis of UNE of all clinical grades of severity. US was more efficient in localizing clinically severe, and SSNCSs in localizing mild or moderate UNE. SIGNIFICANCE: We recommend SSNCSs as the first confirmatory test in UNE across all grades of severity.

Contribution of ultrasonography in evaluating traumatic lesions of the peripheral nerves.

OBJECTIVE: To assess the indications for and utility of diagnostic ultrasonography (US) in a series of consecutive patients with suspected traumatic peripheral nerve lesions (TPNL). METHODS: We retrospectively reviewed the electronic medical records of consecutive patients referred from February 2013 to May 2018 to our US laboratory. All included patients were examined using standard US equipment, with a 4-13MHz linear array transducer. RESULTS: In the analyzed period, we performed US examinations in 143 patients with 149 suspected TPNL. Electrodiagnostically (EDx) complete TPNL were found in 63 (45%), partial in 59 (42%), and only demyelination (i.e., neurapraxia) in four (3%) patients. TPNL could not be confirmed in 14 (10%) patients. Nerve discontinuity was not demonstrated by US in any of the patients with EDx incomplete nerve lesions. Contact of the nerve with osteosynthetic material (OSM) was found in eight of 33 patients (24%). In five patients, the nerve could not be adequately evaluated throughout its course due to extensive changes in the surrounding tissues. DISCUSSION: In acute situations, US is most useful in EDx complete TPNL to differentiate between nerve axonotmesis and neurotmesis. High-velocity trauma, lacerations, and bone fractures are all risk factors for neurotmesis. In chronic situations, US is useful in cases of functionally inefficient reinnervation, neuropathic pain, or progressive nerve dysfunction. In such patients, the surrounding tissues and the relation of the nerve to any OSM need to be carefully examined. US examination is probably not needed in patients with TPNL following acute blunt trauma, only minor clinical deficits and/or slightly/moderately abnormal EDx findings.

Long-term outcomes in patients with ulnar neuropathy at the elbow treated according to the presumed aetiology.

OBJECTIVES: Ulnar neuropathy at the elbow (UNE) consists mainly of two conditions: entrapment under the humeroulnar aponeurosis (HUA) and extrinsic compression in the retrocondylar (RTC) groove. These in our opinion need different treatment: surgical HUA release and avoidance of inappropriate arm positioning, respectively. We treated our UNE patients accordingly, and studied their long-term outcomes. METHODS: We invited our cohort of UNE patients to a follow-up examination consisting of history, neurological, electrodiagnostic (EDx) and ultrasonographic (US) examinations performed by four blinded investigators. RESULTS: At a mean follow-up time of 881 days, we performed a complete evaluation in 117 of 165 (65%) patients, with 96 (90%; 35 HUA and 61 RTC) treated according to our recommendations. An improvement was reported by 83% of HUA and 84% of RTC patients. In both groups the ulnar nerve mean compound muscle action potential (CMAP) amplitude, and the minimal motor nerve conduction velocity increased, while the maximal ulnar nerve cross-sectional area (CSA) decreased. CONCLUSION: After 2.5 years similar proportions of HUA and RTC patients reported clinical improvement that was supported by improvement in EDx and US findings. SIGNIFICANCE: These results suggest that patients with UNE improve following both surgical decompression and non-operative treatment. A clinical trial comparing treatment approaches in neuropathy localised to the HUA and RTC will be needed to possibly confirm our opinion that the therapeutic approach should be tailored according to the presumed aetiology of UNE.

Neurologic examination and instrument-based measurements in the evaluation of ulnar neuropathy at the elbow.

INTRODUCTION: The aim of the study was to compare the utility of instrument-based assessment of peripheral nerve function with the neurologic examination in ulnar neuropathy at the elbow (UNE). METHODS: We prospectively recruited consecutive patients with suspected UNE, performed a neurologic examination, and performed instrument-based measurements (muscle cross-sectional area by ultrasonography, muscle strength by dynamometry, and sensation using monofilaments). RESULTS: We found good correlations between clinical estimates and corresponding instrument-based measurements, with similar ability to diagnose UNE and predict UNE pathophysiology. DISCUSSION: Although instrument-based methods provide quantitative evaluation of peripheral nerve function, we did not find them to be more sensitive or specific in the diagnosis of UNE than the standard neurologic examination. Likewise, instrument-based methods were not better able to differentiate between groups of UNE patients with different pathophysiologies. Muscle Nerve 57: 951-957, 2018.

Nerve conduction velocity and cross-sectional area in ulnar neuropathy at the elbow.

INTRODUCTION: In the precise localization of ulnar neuropathy at the elbow (UNE) we have noted discrepancies between electrodiagnostic (EDx) and ultrasonographic (US) findings. We aimed to explore the relationship between the 2 techniques. METHODS: Four study-blind examiners took a history and performed neurologic, EDx, and US examinations of a group of prospectively recruited patients with UNE. They assessed the relationship between ulnar nerve cross-sectional area (CSA) and motor nerve conduction velocity (MNCV). RESULTS: In 106 patients with UNE at the retrocondylar (RTC) groove, the highest CSA and lowest MNCV were noted in the same short segment. In 54 patients with UNE at the humeroulnar aponeurosis (HUA), the highest CSA and lowest MNCV were noted proximal to the HUA. DISCUSSION: MNCV and CSA were highly correlated in UNE. Ulnar nerve slowing proximal to the entrapment at the HUA was surprising, but consistent with previous studies done on carpal tunnel syndrome. Muscle Nerve 56: E65-E72, 2017.

Peripheral nerve ultrasonography in patients with transthyretin amyloidosis.

OBJECTIVE: To systematically study peripheral nerve morphology in patients with transthyretin (TTR) amyloidosis and TTR gene mutation carriers using high-resolution ultrasonography (US). METHODS: In this prospective cross-sectional study we took a structured history, performed neurological examination, and measured peripheral nerve cross-sectional areas (CSAs) bilaterally at 28 standard locations using US. Demographic and US findings were compared to controls. RESULTS: Peripheral nerve CSAs were significantly larger in 33 patients with familial amyloid polyneuropathy (FAP) compared to 50 controls, most dramatically at the common entrapment sites (median nerve at the wrist, ulnar nerve at the elbow), and in the proximal nerve segments (median nerve in the upper arm, sciatic nerve in the thigh). Findings in 21 asymptomatic TTR gene mutation carriers were less marked compared to controls, with CSAs being larger only in the median nerve in the upper arm. Nerve CSAs correlated with abnormalities on nerve conduction studies. CONCLUSION: Using US, we confirmed previous pathohistological and imaging reports in FAP of the most pronounced peripheral nerve thickening in the proximal limb segments. SIGNIFICANCE: Similar to US findings in diabetic and vasculitic neuropathies these predominantly proximal locations of nerve thickening may be attributed to ischaemic nerve damage caused by poor perfusion in the watershed zones along proximal limb segments.

Complete dislocation of the ulnar nerve at the elbow: a protective effect against neuropathy?

INTRODUCTION: Recurrent complete ulnar nerve dislocation has been perceived as a risk factor for development of ulnar neuropathy at the elbow (UNE). However, the role of dislocation in the pathogenesis of UNE remains uncertain. METHODS: We studied 133 patients with complete ulnar nerve dislocation to determine whether this condition is a risk factor for UNE. In all, the nerve was palpated as it rolled over the medial epicondyle during elbow flexion. RESULTS: Of 56 elbows with unilateral dislocation, UNE localized contralaterally in 17 elbows (30.4%) and ipsilaterally in 10 elbows (17.9%). Of 154 elbows with bilateral dislocation, 26 had UNE (16.9%). Complete dislocation decreased the odds of having UNE by 44% (odds ratio = 0.475; P = 0.028), and was associated with less severe UNE (P = 0.045). CONCLUSIONS: UNE occurs less frequently and is less severe on the side of complete dislocation. Complete dislocation may have a protective effect on the ulnar nerve. Muscle Nerve 56: 242-246, 2017.

Validation of preoperative nerve conduction studies by intraoperative studies in patients with ulnar neuropathy at the elbow.

OBJECTIVE: To validate the findings of preoperative motor short-segment nerve conduction studies (SSNCSs) by intraoperative SSNCSs in patients with cubital tunnel syndrome. METHODS: We prospectively recruited patients with ulnar neuropathy at the elbow (UNE) localized distal to the medial epicondyle (ME). Preoperatively, motor SSNCSs and ultrasonography (US) were performed. Immediately after surgical dissection of the humeroulnar aponeurotic arcade (HUA), intraoperative near-nerve motor SSNCSs were performed, and compared to preoperative findings. RESULTS: We studied 36 arms with UNE in the cubital tunnel. Preoperative US localized UNE distal to ME in all operated arms, and demonstrated ulnar nerve constriction in 19 of them. Visual inspection confirmed ulnar nerve swelling in all studied nerves, but was unreliable with regard to ulnar nerve constriction. In all 5 (14%) arms with inconclusive localization by SSNCSs, intraoperative SSNCSs confirmed the preoperative US diagnosis of cubital tunnel syndrome. Intraoperative SSNCSs confirmed the preoperative localization in 24 (67%) arms, and were non-contributive in 7 (19%) arms with intraoperatively non-recordable responses. CONCLUSION: Intraoperative near-nerve SSNCSs did not change the localization in any of 36 arms with UNE distal to ME. Therefore, our data indicate that a combination of preoperative SSNCSs and US reliably localizes UNE in the cubital tunnel. SIGNIFICANCE: Our present study suggests that in arms with consistent preoperative SSNCSs and US studies, no intraoperative near-nerve SSNCSs are needed to confirm ulnar nerve entrapment under the HUA.

Can neurologic examination predict pathophysiology of ulnar neuropathy at the elbow?

OBJECTIVE: To explore the utility of neurologic examination to predict the pathophysiology of ulnar nerve lesions in patients with ulnar neuropathies at the elbow (UNE). METHODS: We prospectively recruited consecutive patients with suspected UNE. Four blinded investigators took a history and performed neurologic, electrodiagnostic (EDx) and ultrasonographic (US) examinations. In patients with axonal UNE, conduction block and conduction slowing, the pathophysiologies of UNE and neurologic examination findings were compared. RESULTS: We found significant differences in muscle bulk and strength of the ulnar hand muscles between 96 arms with axonal UNE, 34 with conduction block, and 45 with isolated conduction slowing. Severe muscle atrophy and weakness (0-3/5 on MRC) predicted axonal UNE, and moderate weakness (-4/5 on MRC) with normal muscle bulk predicted UNE with conduction block. Using more restrictive criteria for axonal and conduction block UNE, muscle strength of 4-5/5 on MRC was predictive of isolated conduction slowing. CONCLUSION: Although we found significant differences in patterns of muscle bulk and strength between groups of UNE patients with different UNE pathophysiologies, in the majority of arms, neurologic examination could not reliably predict UNE pathophysiology. SIGNIFICANCE: Results confirm that nerve conduction studies are essential for determination of the pathophysiology of ulnar neuropathy at the elbow.

Proposal for electrodiagnostic evaluation of patients with suspected ulnar neuropathy at the elbow.

OBJECTIVE: To develop an evidence-based electrodiagnostic (EDx) approach to patients with suspected ulnar neuropathy at the elbow (UNE). METHODS: We prospectively recruited patients with suspected UNE, took a history and performed clinical neurologic, EDx and ultrasonographic (US) examinations. Ulnar motor and mixed nerve 5 × 2 cm, 2 × 4 cm and 10 cm studies across the elbow were compared regarding sensitivity and precise localization of UNE. RESULTS: In 175 evaluated patients, the highest sensitivity/precise localization was demonstrated by the motor 5 × 2 cm study (93%/92%), followed by the 2 × 4 cm study (89%/83%) and the 10-cm study (82%/0%). The sensitivities of mixed ulnar nerve studies to diagnose/precisely localize UNE were 12-23%/27-36% lower than the corresponding motor studies. CONCLUSIONS: Based on our data, we suggest starting EDx evaluation of UNE with a motor 2 × 4 cm study (recording from either the abductor digiti minimi or the first dorsal interosseous muscles), with two additional stimulation sites being added if the initial result is negative. This results in a motor 4 × 2 cm study. In all suspected UNE patients, an antidromic sensory study to the 5th finger should also be performed. SIGNIFICANCE: The proposed EDx protocol is robust, sensitive and time efficient. We hope that it will improve the diagnosis of UNE.

Does ulnar nerve dislocation at the elbow cause neuropathy?

INTRODUCTION: The role of ulnar nerve dislocation in the pathogenesis of ulnar neuropathy at the elbow (UNE) is not clear. Data exist for and against a causal relationship. METHODS: We studied UNE patients and controls divided into 4 groups consisting of 203 UNE patient arms (185 with abnormal and 18 with normal diagnostic studies) and 49 controls (10 with abnormal and 39 with normal studies). In all arms we performed neurologic examination, short-segment nerve conduction studies (SSNCS), and ultrasonography (US). The frequency of partial and complete nerve dislocation was calculated in each group. RESULTS: Dislocation tended to be more common in controls compared with UNE patients (P = 0.056). It was particularly common in controls with subclinical UNE and patients with UNE symptoms but normal diagnostic studies. CONCLUSION: Our data speak against a causal relationship between ulnar nerve dislocation and UNE. However, the findings also suggest that dislocation may cause mild ulnar nerve damage.