Ultrahigh-frequency ultrasound of fascicles in the common fibular, superficial fibular, and sural nerves

INTRODUCTION/AIMS

While ultrasound assessment of cross-sectional area and echogenicity has gained popularity as a biomarker for various neuropathies, there is a scarcity of data regarding fascicle count and density in neuropathies or even healthy controls. The aim of this study was to determine whether fascicles within select lower limb nerves (common fibular, superficial fibular, and sural nerves) can be counted in healthy individuals using ultrahigh-frequency ultrasound (UHFUS).

METHODS

Twenty healthy volunteers underwent sonographic examination of the common fibular, superficial fibular, and sural nerves on each lower limb using UHFUS with a 48 MHz linear transducer. Fascicle counts and density in each examined nerve were determined by a single rater.

RESULTS

The mean fascicle number for each of the measured nerves included the following: common fibular nerve 9.85 (SD 2.29), superficial fibular nerve 5.35 (SD 1.59), and sural nerve 6.73 (SD 1.91). Multivariate linear regression analysis revealed a significant association between cross-sectional area and fascicle count for all three nerves. In addition, there was a significant association seen in the common fibular nerve between fascicle density and height, weight, and body mass index. Age and sex did not predict fascicle count or density (all p > .13).

DISCUSSION

UHFUS enabled the identification and counting of fascicles and fascicle density in the common fibular, superficial fibular, and sural nerves. Knowledge about normal values and normal peripheral nerve architecture is needed in order to further understand and identify pathological changes that may occur within each nerve in different disease states.

Positional relationship between the Achilles tendon and sural nerve on ultrasound

PURPOSE

This study sought to clarify the positional relationship between the Achilles tendon and sural nerve using ultrasound.

METHODS

We studied 176 legs in 88 healthy volunteers. The positional relationship between the Achilles tendon and sural nerve at heights of 2, 4, 6, 8, 10, and 12 cm proximal from the calcaneus' proximal margin was investigated by distance and depth. Setting the X-axis (left/right) as the horizontal axis and Y-axis (depth) as the vertical axis against ultrasound images, we investigated the distance between the lateral margin of the Achilles tendon to the midpoint of the sural nerve on the X-axis. The Y-axis was split into four zones: the part behind the center of the Achilles tendon (AS), the part in front of the center of the Achilles tendon (AD), the part behind the Achilles tendon (S), and the part in front (D). We investigated the zones through which the sural nerve passed. We also studied any significant differences between the sexes and left/right legs.

RESULTS

The mean distance on the X-axis was closest at 6 cm, with 1.1 ± 5.0 mm between them. The sural nerve's position on the Y-axis was such that at positions more proximal than 8 cm, the sural nerve ran through zone S in most legs and moved to zone AS through heights 2-6 cm. No parameters showed significant differences between the sexes or left/right legs.

CONCLUSION

We presented the positional relationship between the Achilles tendon and sural nerve and suggested some measures to prevent nerve injury during surgery.

Sural nerve: imaging anatomy and pathology

High resolution ultrasound (US) and magnetic resonance (MR) neurography are both imaging modalities that are commonly used for assessing peripheral nerves including the sural nerve (SN). The SN is a cutaneous sensory nerve which innervates the lateral ankle and foot to the base of the fifth metatarsal. It is formed by contributing nerves from the tibial and common peroneal nerves with six patterns and multiple subtypes described in literature. In addition to the SN being a cutaneous sensory nerve, the superficial location enables the nerve to be easily biopsied and harvested for a nerve graft, as well as increasing the susceptibility to traumatic injury. As with any peripheral nerves, pathologies such as peripheral nerve sheath tumors and neuropathies can also affect the SN. By utilizing a high frequency probe in US and high-resolution MR neurography, the SN can be easily identified even with the multiple variations given the standard distal course. US and MRI are also useful in determining pathology of the SN given the specific image findings that are seen with peripheral nerves. In this review, we evaluate the normal imaging anatomy of the SN and discuss common pathologies identified on imaging.

Dose-efficient multimodal microscopy of human tissue at a hard X-ray nanoprobe beamline

X-ray fluorescence microscopy performed at nanofocusing synchrotron beamlines produces quantitative elemental distribution maps at unprecedented resolution (down to a few tens of nanometres), at the expense of relatively long measuring times and high absorbed doses. In this work, a method was implemented in which fast low-dose in-line holography was used to produce quantitative electron density maps at the mesoscale prior to nanoscale X-ray fluorescence acquisition. These maps ensure more efficient fluorescence scans and the reduction of the total absorbed dose, often relevant for radiation-sensitive (e.g. biological) samples. This multimodal microscopy approach was demonstrated on human sural nerve tissue. The two imaging modes provide complementary information at a comparable resolution, ultimately limited by the focal spot size. The experimental setup presented allows the user to swap between them in a flexible and reproducible fashion, as well as to easily adapt the scanning parameters during an experiment to fine-tune resolution and field of view.

High resolution ultrasonography of peripheral nerves in diabetic patients to evaluate nerve cross sectional area with clinical profile

OBJECTIVES

The aim of this observational study was ultrasound evaluation of peripheral nerves cross-sectional area (CSA) in subjects with probable diabetic peripheral sensorimotor neuropathy (DPN). CSA was analyzed with reference to clinical and nerve conduction study's (NCS) parameters for early diagnosis and pattern of involvement.

METHODS

A total of 50 patients with probable DPN due to Type 2 diabetes and 50 age-matched healthy controls underwent sonographic examinations of ulnar nerve at the lower arm, median nerve proximal to carpal tunnel, the common peroneal nerve proximal to fibular head, tibial nerve proximal to the tarsal tunnel, and sural nerve at lower third leg.

RESULTS

CSA was increased in cases of DPN as compared to healthy controls. Area changes were more marked with demyelinating pattern. Probable DPN cases with normal NCS had significantly higher number of peripheral nerves showing increased CSA as compared to healthy control. A cut-off of >4 nerve thickening showed a sensitivity of 86 %, and specificity of 56%. The neuropathy pattern in the lower limb was axonal, whereas in the upper limb, it was demyelinating with the majority showing sonographic feature of associated compressive neuropathy.

CONCLUSION

There is an increase in CSA of peripheral nerve in diabetic patients. It can be used as a morphological marker for classifying DPN with changes being picked up earlier to NCS abnormality. Clinical neurological presentation in probable DPN can also be due to compressive neuropathy in early phases, and ultrasound can be a useful tool.

ADVANCES IN KNOWLEDGE

Early pick up of DPN cases shall be useful for early therapy and motivating the patients to actively participate in the treatment. Morphological changes on ultrasonography precedes the electrodiagnostic change in DPN. Symptoms of DPN is not only due to metabolic changes but also compressive neuropathy.

Charcot-Marie-Tooth disease type 1A: Longitudinal change in nerve ultrasound parameters

BACKGROUND

This study aimed to elucidate the longitudinal changes in nerve ultrasound parameters of adult Charcot-Marie-Tooth disease type 1A (CMT1A) patients.

METHODS

Fifteen adult patients with CMT1A prospectively underwent nerve ultrasound and clinical assessment (CMT neuropathy score [CMTNS]) at baseline and 5 y later. Nerve cross-sectional area (CSA) and echogenicity were measured in the median and sural nerves. Changes in ultrasound parameters and CMTNS and correlation between changes of ultrasound parameters and CMTNS were analyzed.

RESULTS

Median and sural nerve CSAs did not change over 5 y, although CMTNS increased (P < .01). Nerve echogenicity in the sural nerve decreased over 5 y (P = .045). No correlations between changes in nerve ultrasound parameters and CMTNS were identified.

CONCLUSIONS

No longitudinal changes in nerve size was detected in adult CMT1A. Exploring the factors that determine nerve size in childhood CMT1A may lead to the development of treatments.

High resolution real time ultrasonography of the sural nerve after percutaneous repair of the Achilles tendon

BACKGROUND

Percutaneous Achilles tendon repair has been developed to minimise soft tissue complications following treatment of tendon ruptures. However, there are concerns because of the risk of sural nerve injury. Few studies have investigated the relationship between the Achilles tendon, the sural nerve and its several anatomical course variants.

METHODS

We studied 7 cadaveric limbs (7 Achilles tendons) in which a percutaneous repair of the Achilles tendon was performed. On each tendon, high resolution real time ultrasonography examination was performed by an experienced musculoskeletal radiologist before and after the procedure, with the surgeons blind to the results of the scan both before and after surgery.

RESULTS

In two instances, high resolution real time ultrasonography examination revealed nerve entrapment at the level of most proximal lateral suture.

CONCLUSIONS

Since the sural nerve can be easily visualised using high-frequency high resolution real time ultrasonography, intraoperative ultrasound can be of assistance during percutaneous repair of Achilles tendon rupture.

CLINICAL RELEVANCE

The sural nerve can be readily visualised by high-frequency high resolution real time ultrasonography probes. It could be beneficial to use high resolution real time ultrasonography intraoperatively or perioperatively to minimise the risks of sural nerve injury when undertaking percutaneous repair of Achilles tendon tears.

Ultrasonographic Imaging for Sural Nerve Injury after Achilles Tendon Repair

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Ultrasonography of the Sural Nerve: Normal and Pathologic Appearances

Ultrasonography (US) of peripheral nerves has gained wide popularity because of the increased definition of modern high-frequency electronic transducers, as well as the well-known advantages of US, which include easy availability, low cost, and the possibility of realizing a dynamic examination. Traditionally, US has been deployed to assess the major nerves of the limbs. More recently, US has also been used to assess the normal appearance and pathologic changes of smaller subcutaneous nerves. The sural nerve is a small sensory nerve in the subcutaneous tissues of the calf that can be affected by a variety of disorders. This pictorial essay illustrates the normal anatomy of the sural nerve, the technique for its examination by US, as well as the US appearance of its main pathologic changes.

Sonographic features of peripheral nerves at multiple sites in patients with diabetic polyneuropathy

OBJECTIVE

Diabetic polyneuropathy (DPN) is one of the major complications of diabetes mellitus. Ultrasound has been frequently used for evaluation of peripheral nerves. However, there are few studies that have evaluated multiple peripheral nerves in DPN. In this study, ultrasonographic features of multiple peripheral nerves in upper and lower extremities of DPN patients were investigated and compared with those of healthy controls.

METHODS

This study was a case-control study that enrolled 20 patients with confirmed diagnosis of DPN and 20 healthy controls. The ultrasonography was performed on the sural, tibial, fibular, sciatic, median, ulnar, radial, and musculocutaneous nerves. Nerve cross-sectional area (CSA) was measured at multiple points for each peripheral nerve. The CSAs were compared between DPN and control groups, and analyzed in relation to the clinical characteristics and electrophysiologic findings.

RESULTS

The CSAs were significantly larger in the DPN group for sural nerve, fibular nerve at the fibular head level, median nerve at the carpal tunnel and mid-humerus level, ulnar nerve at the cubital tunnel outlet and mid-humerus level, and radial nerve at the spiral groove. The CSAs of sural nerve, tibial nerve and median nerve were significantly correlated with electrophysiologic findings. The sural nerve CSA revealed significant correlation with HbA1c.

CONCLUSIONS

These results suggest that the ultrasonography can provide useful information in diagnosis and evaluation of DPN.

Percutaneous Ultrasound-Guided Hydrodissection of a Symptomatic Sural Neuroma

Symptomatic neuromas of the sural nerve are a rare but significant cause of pain and debilitation in athletes. Presentation is usually in the form of chronic pain and dysesthesias or paresthesias of the lateral foot and ankle. Treatment traditionally ranges from conservative measures, such as removing all external compressive forces, to administration of nonsteroidal anti-inflammatory drugs, vitamin B6, tricyclic antidepressants, antiepileptics, or topical anesthetics. This article reports a case of sural nerve entrapment in a 34-year-old male triathlete with a history of recurrent training-induced right-sided gastrocnemius strains. The patient presented with numbness in the right lateral foot and ankle that had persisted for 3 months, after he was treated unsuccessfully with extensive nonoperative measures, including anti-inflammatory drugs, activity modification, and a dedicated physical therapy program of stretching and strengthening. Orthopedic assessment showed worsening pain with forced passive dorsiflexion and manual pressure applied over the distal aspect of the gastrocnemius. Plain radiographs showed normal findings, but in-office ultrasound imaging showed evidence of sural nerve entrapment with edema and neuromatous scar formation in the absence of gastrocnemius or soleus pathology. Percutaneous ultrasound-guided hydrodissection of the sural nerve at the area of symptomatic neuroma and neural edema was performed the same day. The patient had complete relief of symptoms and full return to the preinjury level of participation in competitive sports. This case report shows that hydrodissection, when performed by an experienced physician, can be an effective, minimally invasive technique for neurolysis in the setting of sural nerve entrapment, resulting in improvement in clinical symptoms.

Anatomy of the sural nerve and its relation to the achilles tendon by ultrasound examination

Sural nerve injury is a relatively common complication after surgery on the Achilles tendon. Studies to determine the course of the sural nerve have been performed on cadaveric specimens. The purpose of this cross-sectional study was to use ultrasound to determine the relations of the sural nerve in a healthy population. The authors performed ultrasound examination of the posterior triangle of the ankle and Achilles tendon to determine the course of the sural nerve relative to the Achilles tendon in healthy participants. The mean distance between the nerve and the tendon was 21.48, 11.47, 5.8, and 0.81 mm lateral to the Achilles tendon as measured at the insertion and 4, 8, and 11 cm proximally, respectively. Male participants tended to have a nerve that was initially more lateral to the Achilles insertion compared with women. The distance between the sural nerve and the Achilles tendon was found to be lower in older participants, with the nerve passing significantly closer to the tendon at all levels (P<.01). Three anatomical variants were reported, with the nerve crossing the lateral border of the Achilles low or high or with multiple branches yet to converge. The course of the sural nerve can be visualized and plotted relative to the Achilles tendon using ultrasound examination in healthy participants. Older patients may be at an increased risk of iatrogenic nerve injury because the nerve courses closer to the Achilles tendon than that in young patients. Intraoperative ultrasound examination may be a useful modality to prevent sural nerve injury during Achilles tendon surgery.

[Polyneuropathy associated with monoclonal gammopathy of undetermined significance]

The prevalence of polyneuropathy in patients with monoclonal gammopathy of undetermined significance (MGUS) has been reported to be 10-50%. The majority of patients have a chronic, slowly progressive, distal, symmetric and predominantly sensory polyneuropathy. A caused relationship between polyneuropathy and immunoglobulin (Ig)M MGUS is better established than the relationship between polyneuropathy and IgG/IgA MGUS because of the observed binding of IgM to myelin sheaths and widening of myelin lamellae. In randomized controlled trials plasma exchange, immunosuppressive, rituximab and intravenous Ig have been found to have a clinical meaningful effect.

Preliminary evaluation of the sural nerve using 22-MHz ultrasound: a new approach for evaluation of diabetic cutaneous neuropathy

BACKGROUND

The application of 22-MHz high-frequency ultrasound allows for visualization of the inner part of the sural nerve. The aim of this study was to evaluate the morphological changes of sural nerves in patients with type 2 diabetes mellitus using ultrasound.

MATERIALS AND METHODS

The thickness/width (T/W) ratio, the cross-sectional area (CSA) of the sural nerves and the maximum thickness (MT) of the nerve fascicles were measured in 100 patients with type 2 diabetes mellitus and 50 healthy volunteers using 22-MHz ultrasound. Receiver operating characteristic (ROC) curves were plotted to determine the optimal cut-off values as well as the sensitivities and specificities. All parameters were significantly different between the subject and control groups. The ROC curves demonstrated that the MT was the most predictive of diabetic cutaneous neuropathy, with an optimal cut-off value of 0.365 mm that yielded a sensitivity of 90.3% and a specificity of 87.7%.

CONCLUSIONS

The results of this study suggest that 22-MHz ultrasound may be a valuable tool for evaluating diabetic cutaneous nerve neuropathy.

[The sural nerve as a contributing factor in chronic achillodynia - an explorative ultrasound study]

BACKGROUND AND AIM

Achillodynia is often seen as a sign of repetitive strain of dorsal tissue of the calf. A neurogene component is also considered for this disease pattern. This association haven`t been investigated yet. The major goal of this study was the investigation of the dynamics of the sural nerve by ultrasonography with regard to movements of ankle, knee and hip. This concerns the physiological situation and pathological aspects of achillodynia.

SUBJECTS/METHOD

In this cross sectional study without a blinding-assay 29 sural nerves of 15 healthy subjects (group A) and 6 sural nerves of 3 subjects with pain or dysaesthesia at the achilles tendon or the lateral foot (group B) have been investigated by diagnostic ultrasonography.

RESULTS

The sural nerve has an average size of 3.7 mm (2) (± 0.05 mm (2)) for healthy subjects and 4.1 mm (2) (± 0.1 mm (2)) for those with achillodynia. The lateral (Mlat = 3.89 mm) and anterio-posterior (Map = 0.56 mm) movement of the sural nerve has a statistic significantly greater extent by the whole range of motion of dorsalflexion and plantarflexion than by flexion and extension of the kneejoint (Mlat: p = 0.008; Map: p = 0.0115) or by abduction and adduction of the hipjoint (Mlat: p = 0.0025; Map: p = 0.002) for group A. Within this study, no statistic significant differences between both groups could be observed regarding the dynamics and concerning the size of the sural nerve.

A clinical test to avoid sural nerve injuries in percutaneous Achilles tendon repairs

Percutaneous repairs of Achilles tendon ruptures has gained popularity due the reduced incidence of wound complications, however its use is still limited by the high incidence of sural nerve injuries associated with these repairs. The only technique described to avoid this adverse event is to surgically expose the nerve peri-operatively. In our study, we describe and validate a clinical technique to identify the sural nerve. The sural nerve was mapped using this technique both clinically and by Ultrasound (US) in a cohort of male subjects with intact Achilles tendons. We demonstrated an excellent correlation between the clinical and US mapping. This study demonstrates an accurate and repeatable clinical technique for mapping the sural nerve in conjunction with percutaneous Achilles tendon repairs.

Misdiagnosis of lumbar-sacral radiculopathy: usefulness of combination of EMG and ultrasound

In the presence of sensitive symptoms along the lumbar-sacral dermatomeric region, it is easy to suspect a lumbar-sacral radiculopathy, it being a very common disease. Clinical evaluation, neurophysiology and magnetic resonance imaging are common tools in diagnosing lumbosacral radiculopathy. Nevertheless, sometimes tumour may mimic radiculopathy. With the improvement of ultrasound, most peripheral nerves may be virtually identified. We describe two patients where tumour of sural nerve and tibial nerve mimicked S1 radiculopathy. We diagnosed the tumours only through a comprehensive nerve assessment combining clinical evaluation, US and neurophysiology. The association of neurophysiological and imaging US assessments, possibly in the same session, may avoid misdiagnosis.

Neurophysiological and ultrasound findings in sural nerve lesions following stripping of the small saphenous vein

We describe the neurophysiological and ultrasound (US) findings in two patients with right sural nerve lesions following stripping of the small saphenous vein for varicose vein treatment. In the first case, US showed a tear of the nerve proximal to the lateral malleolus and a hypoechoic swelling of the proximal stump, likely related to a terminal bulb neuroma. A sural conduction study performed distally and proximally to the lesion through a near-nerve needle technique showed absent responses. In the second case, US showed a deep subcutaneous extension of a postsurgical scar placed behind the lateral malleolus close to the sural nerve, but no nerve discontinuity. Sural conduction study showed absent responses distal to the scar. Sural stimulation immediately above the scar yielded a small response at the sciatic nerve. A subsequent investigation performed 15 months after the operation showed absent proximal and distal responses. The combination of US and sural conduction study, including recording at the sciatic nerve, to our knowledge has not been described previously, and may yield important complementary information in the diagnosis of sural nerve lesions.

Impaired blood flow and arterio-venous shunting in human diabetic neuropathy: a novel technique of nerve photography and fluorescein angiography

New techniques of sural nerve photography and fluorescein angiography which are able to provide an index of nerve blood flow have been developed. Under local anaesthetic, 3 cm of sural nerve was exposed at the ankle using an operating microscope. Without disturbing the epineurium, vessels were identified and photographed at a standard magnification (x 30). These were independently graded by an ophthalmologist not otherwise involved with the study. Fluorescein angiography was then carried out on the exposed nerve. The fluorescein appearance time and intensity of fluorescence were quantified, using computer analysis of digitised images. Thirteen subjects with chronic sensory motor neuropathy, five non-neuropathic diabetic and nine normal control subjects were studied. The mean epineurial vessel pathology score of the neuropathic group was significantly higher than the combined normal control and non-neuropathic diabetic groups (p < 0.01). Direct epineurial arteriovenous shunting was observed in six neuropathic and one non-neuropathic diabetic patients and not in any of the normal control subjects. The nerve fluorescein appearance time was significantly delayed in subjects with chronic sensory motor neuropathy (51.5 +/- 12 s) compared to both normal (34.7 +/- 9 s, p < 0.01) and non-neuropathic diabetic subjects (33.4 +/- 11 s, p < 0.025). The mean intensity of fluorescence at 96, 252 and 576 s, was significantly lower in subjects with chronic sensory motor neuropathy compared with both of the other groups (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)