A noninvasive method of neurography in meralgia paraesthetica

Effect of Fascia Penetration in Lateral Femoral Cutaneous Nerve Conduction

Objective

To evaluate the effect of fascia penetration and develop a new technique for lateral femoral cutaneous nerve (LFCN) conduction studies based on the fascia penetration point (PP) identified using ultrasound.

Methods

The fascia PP of the LFCN was localized in 20 healthy subjects, and sensory nerve action potentials (SNAPs) were obtained at four different stimulation points—2 cm proximal to the PP (2PPP), PP, 2 cm distal to the PP (2DPP), and 4 cm distal to the PP (4DPP). We compared the stimulation technique based on the fascia penetration point (STBFP) with the conventional technique.

Results

The SNAP amplitude of the LFCN was significantly higher when stimulation was performed at the PP and 2DPP than at other stimulation points. Using the STBFP, SNAP responses were elicited in 38 of 40 legs, whereas they were elicited in 32 of 40 legs using the conventional technique (p=0.041). STBFP had a comparable SNAP amplitude and slightly delayed negative peak latency compared to the conventional technique. In terms of the time required, the time spent on STBFP showed a more consistent distribution than the time spent on the conventional technique (two-sample Kolmogorov–Smirnov test, p<0.05).

Conclusion

SNAP of the LFCN significantly changed near the fascia PP, and stimulation at PP and at 2DPP provided high amplitudes. STBFP can help increase the response rate and ensure stable and consistent procedure time of the LFCN conduction study.

Inguinal segmental nerve conduction of the lateral femoral cutaneous nerve in healthy controls and in patients with meralgia paresthetica

A common entrapment site of the lateral femoral cutaneous nerve (LFCN) is in the vicinity of the inguinal ligament. However the more distal segment of this nerve can also be affected. Electrophysiological evaluation of this nerve is difficult. Additionally, available methods have failed in the lesion localization of LFCN. In this study, we aimed to evaluate nerve conduction study in different segments of the LFCN. Nerve action potentials of the LFCN were recorded with distal surface electrodes from a relatively distant point (about 30 cm caudal to the spina iliaca anterior superior). An electrical stimulus was given both 10 cm distal to the SIAS and at the level of the SIAS. Inguinal segmental and distal sensory nerve conduction studies were performed on the LFCN. Thirty-eight healthy controls and 34 patients with meralgia paresthetica (MP) were analyzed by this method. All patients with MP showed electrophysiological abnormalities. Slowed sensory conduction on the inguinal channel (p:0.0001) and loss of response were the most frequent abnormalities (44.7% and 31.6%). In one patient, the only abnormality was slowed sensory conduction at the distal site. Our findings suggest that this technique can help in diagnosis and lesion localization in MP.

Utility of ultrasound-guided surface electrode placement in lateral femoral cutaneous nerve conduction studies

INTRODUCTION

Meralgia paresthetica is a common clinical complaint for which some patients ultimately undergo surgical treatment. The lateral femoral cutaneous nerve (LFCN) has been difficult to reliably test electrophysiologically, likely due to anatomic variability and lack of responses in asymptomatic obese subjects.

METHODS

We compared a novel ultrasound-guided antidromic sensory nerve conduction study (NCS) with a technique described previously in a population of normal subjects, of whom 50% had body mass indices within the obese range (>27.5).

RESULTS

Responses were obtained in at least 92% of subjects using either technique, and 92% of normal subjects had <60% interside variability using the ultrasound-guided technique.

CONCLUSIONS

LFCN sensory nerve action potentials can be obtained in the vast majority of normal subjects, even in an obese population and can provide a useful sensory NCS for evaluation of mid-lumbar radiculopathy, plexopathy, or meralgia paresthetica.

A manual therapy and exercise approach to meralgia paresthetica in pregnancy: a case report

OBJECTIVE

To present a case of a pregnant patient with meralgia paresthetica who improved using manual therapy and exercise procedures.

CLINICAL FEATURES

A 22-year-old patient in the sixteenth week of pregnancy had low back pain, bilateral anterolateral thigh paresthesia and groin pain for a duration of 1 month. She had no motor deficits in either lower extremity and her reflexes were intact. As a standard clinic procedure, a battery of functional tests were performed including: active straight leg raise, long dorsal ligament test, and the pelvic pain provocation procedure. Based on her clinical history and physical responses to the aforementioned functional tests, the diagnosis of meralgia paresthetica was deduced.

INTERVENTION AND OUTCOME

Treatment was provided at 6 visits over a 6-week period where the patient underwent evaluation, manual intervention, and exercise prescription. Active Release Technique (ART) was performed to the restricted right sacroiliac (SIJ) complex and quadratus lumborum muscles. ART and post-isometric relaxation were applied to the illiopsoas muscles. The home exercise program consisted of pelvic/low back mobility, stabilization and relaxation exercises. After 6 treatments, the patient reported complete resolution of low back pain and left lower extremity symptoms and a 90% improvement in the right thigh symptoms. At her one-year follow-up, the patient reported no further complications and the absence of pain.

CONCLUSIONS

Manual therapy and exercises may serve as an effective treatment protocol for pregnant patients experiencing low back pain complicated by paresthesia. Because these conservative procedures offer a low-risk intervention, additional clinical studies are warranted to further study this treatment.

Variability in conduction of the lateral femoral cutaneous nerve

The purpose of this study was to establish a reliable technique for assessing conduction in the lateral femoral cutaneous nerve (LFCN), bearing in mind its anatomical variation. Based on our anatomical study, normative values were obtained in 40 healthy nerves. The optimal stimulation site was located 1 cm or more media 16470526 l to the anterior superior iliac spine (ASIS) in 93% of cases and over the ASIS in 7%. Sensory nerve action potentials (SNAPs) were recorded simultaneously along an imaginary line between the ASIS and the lateral border of the patella and 2 cm medial to this line. Side-to-side variability in amplitude was 31% for the recording from the line and 30% for the medial recording. The variability significantly decreased to 16% when the higher value of each side was compared. Therefore, the measurement of higher amplitude recorded at two different sites may minimize interside variability and improve the diagnostic utility of the LFCN conduction study.

Cutaneous silent periods of the vastus medialis evoked by the stimulation of lateral femoral cutaneous nerve

OBJECTIVE

Cutaneous silent period (CSP), which is a spinal reflex mediated by A-delta cutaneous afferents, is transient suppression of the electromyographic activity. In this study, our aim is to investigate CSPs of vastus medialis muscle (vm-CSP) evoked by the stimulation of the lateral femoral cutaneous nerve (LFCN) in healthy controls and in patients with meralgia paresthetica (MP).

METHODS

Twenty-one patients with MP (17 unilateral, 4 bilateral) and 27 healthy controls were included. Nerve conduction studies of LFCN and vm-CSP were analyzed in all subjects. A stimulus train consisting of five electrical shocks was applied to the skin at the anterolateral side of the thigh for recording of the vm-CSP.

RESULTS

Nerve conduction abnormalities of LFCN were observed in all patients with MP. Mean duration of vm-CSP was 69.7+/-9.2ms, and mean onset latency was 44.7+/-6.9 in healthy controls. Onset latency of vm-CSP was significantly prolonged and the duration of vm-CSP was significantly shortened in patients with MP. Vm-CSP abnormalities were observed in 20/25 extremities with MP.

CONCLUSIONS

Dysfunction of A-delta afferents may cause these findings in patients with MP. Additionally, spinal modulation of pain may also play a role in the explanation of our findings.

SIGNIFICANCE

The present study demonstrates the CSP alterations in the patients with entrapment neuropathy of a cutaneous nerve.

The lateral femoral cutaneous nerve: nerve conduction technique

In 58 subjects without signs or symptoms of peripheral nerve disorders, an antidromic sensory nerve conduction study was performed on the lateral femoral cutaneous nerve. Anatomic dissections were performed on two cadavers to reveal the course of the nerve and to localize the optimal stimulation and recording sites. Mean sensory nerve action potential latency was measured at 1.7 msec (SD = 0.23) with a mean amplitude of 10.5 microV (SD = 4.0). The optimal localization of recording and stimulating surface electrodes and nerve conduction technique procedures are discussed. Reliable electrophysiologic criteria, according to age and body mass index, are obtained.