Sciatic Nerve Cross-sectional Area Research Articles

Magnetic resonance neurography in spinal cord injury: Imaging findings and clinical significance.

It is unknown whether changes to the peripheral nervous system following spinal cord injury (SCI) are relevant for functional recovery or the development of neuropathic pain below the level of injury. Magnetic resonance neurography (MRN) at 3 T allows detection and localization of structural and functional nerve damage. This study aimed to combine MRN and clinical assessments in individuals with chronic SCI and nondisabled controls. Twenty participants with chronic SCI and 20 controls matched for gender, age, and body mass index underwent MRN of the L5 dorsal root ganglia (DRG) and the sciatic nerve. DRG volume, sciatic nerve mean cross-sectional area (CSA), fascicular lesion load, and fractional anisotropy (FA), a marker for functional nerve integrity, were calculated. Results were correlated with clinical assessments and nerve conduction studies. Sciatic nerve CSA and lesion load were higher (21.29 ± 5.82 mm2 vs. 14.08 ± 4.62 mm2 , p < 0.001; and 8.70 ± 7.47% vs. 3.60 ± 2.45%, p < 0.001) in individuals with SCI compared to controls, whereas FA was lower (0.55 ± 0.11 vs. 0.63 ± 0.08, p = 0.022). DRG volumes were larger in individuals with SCI who suffered from neuropathic pain compared to those without neuropathic pain (223.7 ± 53.08 mm3 vs. 159.7 ± 55.66 mm3 , p = 0.043). Sciatic MRN parameters correlated with electrophysiological results but did not correlate with the extent of myelopathy or clinical severity of SCI. Individuals with chronic SCI are subject to a decline of structural peripheral nerve integrity that may occur independently from the clinical severity of SCI. Larger volumes of DRG in SCI with neuropathic pain support existing evidence from animal studies on SCI-related neuropathic pain.

Ultrasonic visualization technique for anatomical and functional analyses of the sciatic nerve in rats.

Ultrasound has been widely used in the diagnosis and minimally invasive treatment of peripheral nerve diseases in the clinic, but there is still a lack of feasibility analysis in rodent models of neurological disease. The purpose of this study was to investigate the changes in the cross-sectional area of the sciatic nerve of different genders and body weights and to explore the effectiveness and reliability of an ultrasound-guided block around the sciatic nerve in living rats. Using ultrasound imaging anatomy of the sciatic nerve of rats, the cross-sectional area of the sciatic nerve in rats of different genders from 6 to 10 weeks old was calculated, and then analyzed its correlation with body weight. Further analyses were conducted through behavioral and cadaveric studies to evaluate the feasibility of ultrasound-guided perineural injection of the sciatic nerve in rats. We first reported that the sciatic nerve cross-sectional area of rats was increased with age (F = 89.169, P < 0.001), males had a higher sciatic nerve cross-sectional area than females (F = 60.770, P < 0.001), and there was a positive correlation with body weight (rMale = 0.8976, P < 0.001; rFemale = 0.7733, P < 0.001). Behavioral observation of rats showed that the lower extremity complete block rate was 80% following the administration of drugs around the sciatic nerve under ultrasound guidance and staining with methylene blue occurred in all sciatic nerves and surrounding muscles and fascia using 20 ultrasound-guided injections. Ultrasound visualization technology can be used as a new auxiliary evaluation and intervention therapy for animal models of peripheral nerve injury, and will provide overwhelming new references for the basic research of neurological diseases.

Morphological Changes on Neuromuscular Ultrasound in Nerves Distal to Gunshot Injuries (P14-8.003)

<h3>Objective:</h3> The aim of this study was to describe unique morphological changes on neuromuscular ultrasound in nerves distal to gunshot injuries and to identify the frequency with which these changes occur. <h3>Background:</h3> A spectrum of peripheral nerve injuries is seen secondary to gunshot wounds. The assessment of these injuries has traditionally been limited to clinical evaluation and supplemented by electrodiagnostic testing. Neuromuscular ultrasound is a versatile imaging technique that has been used to assess peripheral nerve structural integrity, neuroma formation or other structural abnormalities following trauma. The extent of sonographic changes at nerve segments distal to gunshot injuries has not been well described. <h3>Design/Methods:</h3> A retrospective chart review was performed on all patients referred to the electromyography laboratory with peripheral nerve injuries from gunshot wounds who also had neuromuscular ultrasound performed as part of their evaluation. <h3>Results:</h3> 17 patients were evaluated. All had either a nerve transection or neuroma in continuity of a major upper or lower extremity nerve at the site of the gunshot wound. 13 (76%), however, also had significant morphological changes in distal segments of the injured nerve and 12 (71%) had changes in other nearby distal nerves. Common findings included enlarged nerve cross sectional area, enlarged fascicles and hypoechogenicity. One patient had a repeat study nine months following the initial study which demonstrated improvement in sciatic nerve cross sectional area, decreasing from 130 mm² to 79 mm². <h3>Conclusions:</h3> Following gunshot injuries, major morphological changes commonly occur in nerve segments distal to the injury; both in the injured nerve and nearby nerves. Marked enlargement of hypoechoic fascicles is seen along with enlarged cross-sectional area of nerve. We hypothesize that ballistic trauma, such as gunshot injuries, can lead to concussive damage that disrupts the normal architecture of distal nerves. Follow up ultrasound studies suggest that these changes may be partially reversible. <b>Disclosure:</b> Dr. Fagan has nothing to disclose. Dr. Geiger has nothing to disclose. Dr. Preston has received personal compensation in the range of $10,000-$49,999 for serving as an Expert Witness for FBI, US Attorney, Insurance Fraud Investigative Units. Dr. Preston has received publishing royalties from a publication relating to health care.

Evidence of nerve hypertrophy in patients with inclusion body myositis on lower limb MRI.

Inclusion body myositis (IBM) is a myopathic condition but in some patients has been associated with an axonal length-dependent polyneuropathy. In this study, we quantified the cross-sectional area of the sciatic and tibial nerves in patients with IBM comparing with Charcot-Marie-Tooth disease type 1A (CMT1A) and healthy controls using magnetic resonance neurography (MRN). MRN of the sciatic and tibial nerves was performed at 3T using MPRAGE and Dixon acquisitions. Nerve cross-sectional area (CSA) was measured at the mid-thigh and upper third calf regions by an observer blinded to the diagnosis. Correlations were performed between these measurements and clinical data. A total of 20 patients with IBM, 20 CMT1A and 29 healthy controls (age- and sex-matched) were studied. Sciatic nerve CSA was significantly enlarged in patients with IBM and CMT1A compared to controls (sciatic nerve mean CSA 62.3± 22.9 mm2 (IBM) vs. 35.5± 9.9 mm2 (controls), p< 0.001; and 96.9± 35.5 mm2 (CMT1A) vs. 35.5± 9.9 mm2 (controls); p< 0.001). Tibial nerve CSA was also enlarged in IBM and CMT1 patients compared to controls. MRN reveals significant hypertrophy of the sciatic and tibial nerves in patients with IBM and CMT1A compared to controls. Further studies are needed to correlate with neurophysiological measures and assess whether this finding is useful diagnostically.

Intraepineurial fat quantification and cross-sectional area analysis of the sciatic nerve using MRI in Charcot-Marie-Tooth disease type 1A patients

The objectives of this study were to assess the fat fraction (FF) and cross-sectional area (CSA) of the sciatic nerve in Charcot-Marie-Tooth disease type 1A (CMT1A) patients using Dixon-based proton density fat quantification MRI and to elucidate its potential association with clinical parameters. Thigh MRIs of 18 CMT1A patients and 18 age- and sex-matched volunteers enrolled for a previous study were reviewed. Analyses for FF and CSA of the sciatic nerve were performed at three levels (proximal to distal). CSA and FF were compared between the two groups and among the different levels within each group. The relationship between the MRI parameters and clinical data were assessed in the CMT1A patients. The CMT1A patients showed significantly higher FF at level 3 (p = 0.0217) and significantly larger CSA at all three levels compared with the control participants (p < 0.0001). Comparisons among levels showed significantly higher FF for levels 2 and 3 than for level 1 and significantly larger CSA for level 2 compared with level 1 in CMT1A patients. CSA at level 3 correlated positively with the CMT neuropathy score version 2 (CMTNSv2). In conclusion, the sciatic nerve FF of CMT1A patients was significantly higher on level 3 compared with both the controls and the measurements taken on more proximal levels, suggesting the possibility of increased intraepineurial fat within the sciatic nerves of CMT1A patients, with a possible distal tendency. Sciatic nerve CSA at level 3 correlated significantly and positively with CMTNSv2, suggesting its potential value as an imaging marker for clinical severity.

Reference values for the cross-sectional area of the normal sciatic nerve using high-resolution ultrasonography.

AimHigh-resolution ultrasonography is a new and promising technique to evaluate peripheral and spinal nerves. Its validity as a diagnostic tool in neurological diseases has been demonstrated in adults. The aims of study were to establish the reference values for the cross-sectional area of the normal sciatic nerve on high-resolution ultrasonography, and to determine the relationship between the cross-sectional area of the normal sciatic nerve and the subjects’ age, gender, height (in cm), weight (in kg), and body mass index.Material and methodsTwo hundred subjects of both genders and above 18 years of age were studied with high-resolution ultrasonography. The subjects had no history of peripheral neuropathy or trauma to the lower limb. The cross-sectional areas of the normal sciatic nerves were obtained at two different levels in both lower limbs. The mean cross-sectional areas of the sciatic nerves were measured at two different levels, one located at 1 cm above the bifurcation of the sciatic nerve into the tibial and common peroneal nerves, and the other 4 cm above the bifurcation of the sciatic nerve into the tibial and common peroneal nerves.ResultsA positive correlation of the mean cross-sectional area was established with height, weight, and body mass index. Women had smaller cross-sectional areas of the normal sciatic nerves than men at both measuring sites. No significant relationship was established with the age of the subjects.ConclusionsThe established reference values of the cross-sectional area of the sciatic nerve can facilitate the analysis of pathological nerve conditions.

MRI quantifies lumbosacral nerve root and sciatic nerve hypertrophy in chronic inflammatory demyelinating polyradiculoneuropathy

PurposeChronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a treatable, immune-mediated condition characterised by progressive or relapsing motor and sensory neurological deficits. The diagnosis is based on a combination of clinical, neurophysiological and supportive criteria, but can be challenging. In this study, we quantified the diameter and cross-sectional area of the lumbosacral nerve roots, and explored the imaging characteristics of the sciatic nerves, in patients with CIDP versus healthy controls using MRI. MethodsMRI of the lumbosacral plexus and both thighs was performed at 3 T. Orthogonal diameter and cross-sectional area of the lumbosacral nerve roots were measured, along with sciatic nerve cross-sectional area at the mid-thigh level. The MRI appearance of the sciatic nerves was also evaluated qualitatively. All measurements were performed by an observer blinded to the diagnosis. Results10 patients with CIDP and 10 healthy controls (age and sex-matched) were studied. Lumbosacral nerve root diameter and cross-sectional area were significantly increased in patients with CIDP compared to controls (mean diameter 6.0 ± 1.1 mm vs 4.8 ± 0.3 mm; p = 0.006), with a high sensitivity (89 %) and specificity (90 %) on ROC analysis. Sciatic nerve cross sectional area was also significantly increased in the CIDP group, and was accompanied by qualitative MRI changes. ConclusionsQuantitative MRI reveals significant hypertrophy of the lumbosacral nerve roots and sciatic nerves in patients with CIDP compared to controls. This study provides further evidence for the inclusion of lumbosacral nerve root and sciatic nerve hypertrophy on MRI as a supportive feature in the diagnostic criteria for CIDP.

Dorsal root ganglia volume is increased in patients with the Fabry-related GLA variant p.D313Y.

To examine dorsal root ganglia and proximal nerve segments in patients carrying the Fabry-related GLA-gene variant p.D313Y in comparison to patients with classical Fabry mutations and healthy controls by morphometric and functional magnetic resonance neurography. This prospective multicenter study examines the lumbosacral dorsal root ganglia and sciatic nerve in 11 female p.D313Y patients by a standardized magnetic resonance neurography protocol at 3T. Volumes of dorsal root ganglia L3 to S2, permeability of dorsal root ganglia L5 and S1, and spinal nerve L5 as well as cross-sectional area of the sciatic nerve were assessed and compared to 10 females carrying a classical Fabry mutation and 16healthy female controls. Compared to healthy controls, dorsal root ganglia volumes of p.D313Y females were enlarged by 53% (L3), 48% (L4), 43% (L5), 57% (S1)(p < 0.001), and 55% (S2) (p < 0.05), but less pronounced compared to females carrying a classical Fabry mutation. Compared to healthy controls, p.D313Y patients showed no changes of dorsal root ganglia vascular permeability, while patients with a classical Fabry mutation showed a distinct decrease (p < 0.05). Sciatic nerve cross-sectional area was mildly increased by 6% in p.D313Y as well as in classical Fabry patients (p < 0.05). Patients carrying the GLA-gene variant p.D313Y show distinctly enlarged dorsal root ganglia, while vascular permeability remains within normal limits. Overall, these alterations partially share characteristics commonly seen in patients with a mutation causing classical FD. This suggests that p.D313Y causes a potentially treatable condition resembling an early stage of Fabry disease.

Neuromuscular morphometric characteristics in low back pain with unilateral radiculopathy caused by disc herniation: An ultrasound imaging evaluation

BackgroundLittle is known about the neuromuscular morphometric characteristics in patients with sciatica. ObjectiveTo evaluate the possible changes of nerve and muscle structures in patients with low back pain with unilateral radiculopathy due to lumbar disc herniation by ultrasound imaging. DesignA case-control observational study. MethodsForty individuals were divided into case (n = 20; low back pain with unilateral radiculopathy due to disc herniation), and healthy control groups (n = 20). The thickness of lumbar multifidus at L5 level, and of lower limb muscles (i.e., biceps femoris, medial gastrocnemius, and soleus) was measured during both rest and full contraction to calculate the rest/contraction ratio of these muscles. Additionally, the sciatic nerve cross-sectional area and the echogenicity of the nerve and muscles were measured based on ultrasound imaging. The association between severity of low back pain radiculopathy (i.e., pain and patients' perceived disability) and rest/contraction ratio was assessed. ResultsPatients with sciatica showed sciatic nerve enlargement, and different contraction ratios for multifidus (at L5)/ankle plantar flexors compared to the controls. The rest/contraction ratio for biceps femoris was similar between the two groups. ConclusionAccording to these findings, ultrasound imaging can be considered a useful tool to detect changes in the sciatic nerve and muscles due to disc herniation. Furthermore, regarding the observation of significant changes in muscle rest/contraction ratio in the multifidus and gastrosoleus, one might attribute these changes to the nerve root compression.

Test-retest reliability of nerve and muscle morphometric characteristics utilizing ultrasound imaging in individuals with unilateral sciatica and controls

BackgroundUltrasound imaging has been suggested for studying the structure and function of nerves and muscles; however, reliability studies are limited to support the usage. The main aim of this study was to explore the intrarater within-session reliability of evaluating the sciatic nerve and some related muscles morphology by ultrasound imaging.MethodsThree B-mode images from two scans (transverse and longitudinal) were acquired from the multifidus, biceps femoris, soleus and medial gastrocnemius muscles bilaterally from 15 participants with sciatica and 15 controls in one session, 1-h apart. The data were collected from March to July 2017. Contraction ratio was measured only by longitudinal scan, while the echo intensity was measured using maximum rectangular region of interest in two scans (transverse and longitudinal) for all muscles. Cross-sectional area, direct (tracing) and indirect (ellipsoid formula) methods were used to measure the sciatic nerve. Intraclass correlation coefficient (ICC 3,1), standard error of measurement and minimal detectable change were calculated.ResultsGood to high ICCs (0.80–0.96) were found for muscle contraction ratio in the longitudinal scans in all the muscles in both sciatica and control groups. For echo intensity measurements ICCs ranged from moderate to high, with higher ICCs seen with the maximum region of interest in the transverse scans. The minimal detectable change values ranged between 0.11 and 0.53 cm for contraction ratio.ConclusionsUltrasound imaging has high intrarater within-session reliability for assessing the sciatic nerve Cross-sectional area and muscle contraction ratios. Transverse scans with the maximum region of interest result in higher reliability. The sciatic Cross-sectional area is most accurately measured utilizing the direct tracing method rather than the indirect ellipsoid method.

Dorsal root ganglia in vivo morphometry and perfusion in female patients with Fabry disease.

To examine dorsal root ganglia and the proximal nerve segments in female patients with Fabry disease by functional and morphometric magnetic resonance neurography. In this prospective multicenter study the lumbosacral dorsal root ganglia and proximal sciatic nerve were examined in ten female patients with Fabry disease by a standardized magnetic resonance neurography protocol at 3T. Volumes of dorsal root ganglia L3-S2, permeability of dorsal root ganglia L5 and S1 and the spinal nerve L5 as well as the cross-sectional area of the proximal sciatic nerve were compared to 16 gender-matched healthy controls. Dorsal root ganglia were symmetrically enlarged by 54% (L3), 79% (L4), 60% (L5), 94% (S1), and 106% (S2) (p < 0.001). Additionally, permeability of the blood-tissue interface was decreased by 47% (p < 0.001). This finding was most pronounced in the peripheral zone of the dorsal root ganglia, where the cell bodies of the primary sensory neurons are located (p < 0.001). While spinal nerve permeability showed no differences compared to healthy controls, proximal sciatic nerve cross-sectional area was mildly increased by 6% (p < 0.01). Although heterozygous, Fabry females show severe enlarged dorsal root ganglia with a concomitant dysfunctional perfusion, even in patients with minor disease progression and in patients who are not considered for enzyme replacement therapy yet. Alterations in dorsal root ganglia volume and perfusion might serve as a very early in vivo marker for involvement of the peripheral nervous system in Fabry disease, even in patients with residual enzyme activity.

Ultrasonographic evaluation of the median and sciatic nerves in hemiplegic patients after stroke.

The aim of this study was to evaluate morphologically and electrophysiologically the peripheral nerves of hemiplegic patients. Thirty-three (18 women and 15 men) stroke patients were recruited. The mean (SD) age was 55.6 (11.3) yrs, and the mean (SD) disease duration was 14.2 (16.0) mos. Motor nerve conduction study of the median, ulnar, fibular, and tibial nerves as well as sensory nerve conduction study of the median, ulnar, and sural nerves were performed. Diameters and cross-sectional area (CSA) measurements of the median (wrist/midarm levels) and sciatic nerves (midthigh level) were acquired using a 7- to 12-MHz linear probe. The values of the nonparetic limbs were taken as controls. Prolonged distal latency and slowed motor conduction velocity of the tibial nerve as well as reduced amplitudes of the median and ulnar nerves were observed on the paretic sides when compared with those of the nonparetic sides (all P < 0.05). The median and sciatic nerve cross-sectional area values were found to be smaller on the paretic sides when compared with the nonparetic sides (all P < 0.05). The median and ulnar nerve compound muscle action potential amplitudes (paretic side) were positively correlated with arm/hand Brunnstrom Motor Recovery Stage, disease duration, motor Functional Independence Measure score, and Functional Ambulation Category. The peripheral nerves of stroke patients seem to be affected--morphologically and electrophysiologically--on the paretic side.

Preliminary study of high frequency ultrasound in sciatic nerve of rat with diabetic neuropathy

Objective To evaluate the value of high frequency ultrasound in sciatic nerve of rat with diabetic neuropathy.Methods Fifty male Sprague-Dawley rats were divided into 4 groups:Diabetic animals were induced by intravenous injection of streptozotocin after high fat feed for 1 month,after which rats were grouped as 3-month (n =12) and 5-month (n =20) diabetes.Control group were received the streptozotocin vehicle and were classified as 3-month group (n =8) and 5-month group (n =10).Ultrasounic study of cross sectional area (CSA) and pathologic study including number and area of nerve fiber were performed at 3 and 5 months according to the disigned.Results The CSA,number and area of nerve fiber in 5 month diabetes were significantly reduced than 5-month control group (t =5.121,P ＜ 0.05; t =7.113,P ＜0.05; t =6.328,P ＜0.05).The CSA were statistically with the number and area of nerve fiber in 5 month diabetic group (r =0.732,P ＜0.05 ; r =0.715,P ＜0.05).However,the CSA had no significant correlation with the number and area of nerve fiber between 3-month diabetes and control group (P ＞0.05).Conclusions The CSA of sciatic nerve can evaluate the diabetic neuropathy of rat,which might be regarded as a potential index in diagnose of diabetic neuropathy. Key words: Ultrasonography; Peripheral neuropathy; Diabetic mellitus; Sciatic nerve; Rat

P90 Magnetic resonance imaging and sciatic nerve cross-sectional area in inherited and inflammatory neuropathies

P90 Magnetic resonance imaging and sciatic nerve cross-sectional area in inherited and inflammatory neuropathies