Spinal sensory transmission is under descending biphasic modulation, and descending facilitation is believed to contribute to chronic pain. Descending modulation from the brainstem rostral ...ventromedial medulla (RVM) has been the most studied, whereas little is known about direct corticospinal modulation. Here, we found that stimulation in the anterior cingulate cortex (ACC) potentiated spinal excitatory synaptic transmission and this modulation is independent of the RVM. Peripheral nerve injury enhanced the spinal synaptic transmission and occluded the ACC-spinal cord facilitation. Inhibition of ACC reduced the enhanced spinal synaptic transmission caused by nerve injury. Finally, using optogenetics, we showed that selective activation of ACC-spinal cord projecting neurons caused behavioral pain sensitization, while inhibiting the projection induced analgesic effects. Our results provide strong evidence that ACC stimulation facilitates spinal sensory excitatory transmission by a RVM-independent manner, and that such top-down facilitation may contribute to the process of chronic neuropathic pain.
To detect and quantify lesions of the small-caliber sural nerve (SN) in symptomatic and asymptomatic transthyretin familial amyloid polyneuropathy (TTR-FAP) by high-resolution magnetic resonance ...neurography (MRN) in correlation with electrophysiologic and histopathologic findings.
Twenty-five patients with TTR-FAP, 10 asymptomatic carriers of the mutated transthyretin gene (mut
), and 35 age- and sex-matched healthy controls were prospectively included in this cross-sectional case-control study. All participants underwent 3T MRN with high-structural resolution (fat-saturated, T2-weighted, and double-echo sequences). Total imaging time was ≈45 minutes per patient. Manual SN segmentation was performed from its origin at the sciatic nerve bifurcation to the lower leg with subsequent evaluation of quantitative microstructural and morphometric parameters. Additional time needed for postprocessing was ≈1.5 hours per participant. Detailed neurologic and electrophysiologic examinations were conducted in the TTR group.
T2 signal and proton spin density (ρ) reliably differentiated between TTR-FAP (198.0 ± 13.3, 429.6 ± 15.25), mut
carriers (137.0 ± 16.9,
= 0.0009; 354.7 ± 21.64,
= 0.0029), and healthy controls (90.0 ± 3.4, 258.2 ± 9.10;
< 0.0001). Marked differences between mut
carriers and controls were found for T2 signal (
= 0.0065) and ρ (
< 0.0001). T2 relaxation time was higher in patients with TTR-FAP only (
= 0.015 vs mut
carriers,
= 0.0432 vs controls). SN caliber was higher in patients with TTR-FAP vs controls and in mut
carriers vs controls (
< 0.0001). Amyloid deposits were histopathologically detectable in 10 of 14 SN specimens.
SN injury in TTR-FAP is detectable and quantifiable in vivo by MRN even in asymptomatic mut
carriers. Differences in SN T2 signal between controls and asymptomatic mut
carriers are derived mainly from an increase of ρ, which overcomes typical limitations of established diagnostic methods as a highly sensitive imaging biomarker for early detection of peripheral nerve lesions.
This study provides Class III evidence that MRN accurately identifies asymptomatic mut
carriers.
To investigate variations regarding the formation and course of the sural nerve (SN). We dissected 60 formalin-fixed Brazilian fetuses (
n
= 120 lower limbs) aged from the 16
th
to 34
th
weeks of ...gestational age. Three incisions were made in the leg to expose the SN, and the gastrocnemius muscle was retracted to investigate the SN course. Statistical analyses regarding laterality and sex were performed using the Chi-square test. Eight SN formation patterns were classified after analysis. Type 4 (in which the SN is formed by the union of the MSCN with the LSCN) was the most common SN formation pattern. Although there was no statistical association between the formation patterns and the lower limb laterality (
p
= 0.9725), there was as to sex (
p
= 0.03973), indicating an association between anatomical variation and sex. The site of branch joining was in the distal leg most time (53.75%). In all lower limbs, the SN or its branches crossed from the medial aspect of the leg to the lateral margin of the calcaneal tendon (CT). Most often, the SN is formed by joining the MSCN and the LSCN in the distal leg. The SN or its branches ran close to the saphenous vein, crossed the CT from medial to lateral, and distributed around the lateral malleolus.
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.
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.
The lack of a clinically relevant animal models for research in facial nerve reconstruction is challenging. In this study, we investigated the surgical anatomy of the ovine sural nerve as a potential ...candidate for facial nerve reconstruction, and performed its histological quantitative analysis in comparison to the buccal branch (BB) of the facial nerve using cadaver and anesthetized sheep. The ovine sural nerve descended to the lower leg along the short saphenous vein. The length of the sural nerve was 14.3 ± 0.5 cm. The distance from the posterior edge of the lateral malleolus to the sural nerve was 7.8 ± 1.8 mm. The mean number of myelinated fibers in the sural nerve was significantly lower than that of the BB (2,311 ± 381vs. 5,022 ± 433, respectively. p = 0.003). The number of fascicles in the sural nerve was also significantly lower than in the BB (10.5 ± 1.7 vs. 21.3 ± 2.7, respectively. p = 0.007). The sural nerve was grafted to the BB with end-to-end neurorrhaphy under surgical microscopy in cadaver sheep. The surgical anatomy and the number of fascicles of the ovine sural nerve were similar of those reported in humans. The results suggest that the sural nerve can be successfully used for facial nerve reconstruction research in a clinically relevant ovine model.
Abstract A schwannoma or neurilemmoma is a benign, isolated, noninvasive, and encapsulated tumor originating from Schwann cells of the peripheral nerve sheath. The incidence of a schwannoma occurring ...in the foot and ankle is rare, with prevalence rate of 1% to 10%. Schwannomas have no sex predilection, and they commonly occur in patients in their fourth decade. Malignant transformation of benign schwannoma is unusual; however, it is important to note that malignant variants of schwannomas do exist and account for about 5% to 10% of all soft tissue sarcomas. We present 3 cases of benign schwannoma in the lower extremity. All 3 patients presented with varying clinical symptoms, including pain, paresthesia, weakness, and a palpable mass. A schwannoma was eventually diagnosed in all 3 patients. We discuss and review the known entities of peripheral nerve schwannoma and describe the clinical and imaging findings and therapeutic strategies for treating and diagnosing peripheral nerve schwannoma.
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.
Introduction/Aims
Lower limb sensory nerve action potentials are an important component of nerve conduction studies. Most testing of the sural and superficial fibular nerves involves antidromic ...techniques above the ankle, which result in a falsely unobtainable response in 2%–6% of healthy people. Cadaver, surgical, and more recent ultrasound series suggest this may relate to the site of fascia penetration of the nerve, and it is hypothesized that a modified technique may be more likely to produce reliable responses and reduce false‐negative errors.
Methods
This article evaluates a variety of recording distances for both nerves in 100 healthy controls, including varying recording electrode positions and techniques, to provide the optimal electrodiagnostic information in healthy control subjects.
Results
Shorter stimulation distances produce higher‐amplitude responses but become confounded by increasing stimulation artifact at very short distances, with the best balance found at around 10 cm. In both sural and superficial fibular nerves, amplitude increases by approximately 10%/cm compared with the standard 14 cm distance. The Daube superficial fibular technique produced a higher amplitude than the Izzo Intermediate technique (by 22.46%, p < .001). The calculated upper limit of normal for side‐to‐side variation in amplitude was around 50% in the sural nerve but over 70% in the superficial fibular nerve.
Discussion
It is proposed that the 10 cm recording distance for both nerves is optimal, with minimal false‐negatives and a higher amplitude elicited than with existing techniques.
Abstract Introduction The sural nerve is a sensitive nerve whose function is to provide sensory supply for the posterolateral aspect of the distal third of the leg and the lateral side of the dorsum ...of the foot. This nerve is formed in the upper third of the calf from the terminal branches of the tibial and common peroneal nerves and the communicating branch of the sural nerve. Objectives The aim of our study is to showcase two anatomical variants of the sural nerve. Materials and methods Two formalin-preserved cadavers, one male and one female, embalmed using formalin 4% were dissected with the intent of being used as teaching materials for the students attending anatomy classes at the “George Emil Palade” University of Medicine, Pharmacy, Science and Technology of Târgu Mureș, Romania. Results In both cases, less common anatomical variations of the formation of sural nerve were discovered. On the male cadaver, we identified the sural nerve as a continuation of the medial sural cutaneous nerve. The lateral sural cutaneous nerve and the communicating branch of the sural nerve were both absent. On the female cadaver, we identified both the medial sural cutaneous nerve and the lateral sural cutaneous nerve. The sural nerve was, however, a continuation of only the lateral sural cutaneous nerve, with the medial sural cutaneous nerve as an independent branch. Conclusions We described two anatomical variants of the sural nerve, which are less common than those documented in the literature.
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