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ORIGINAL RESEARCH
Ultrasound-Guided Treatment of Meralgia
Paresthetica (Lateral Femoral Cutaneous
Neuropathy)
Technical Description and Results of Treatment in
20 Consecutive Patients
Alberto Tagliafico, MD, Giovanni Serafini, MD, Francesca Lacelli, MD, Nadia Perrone, MD,
Valtero Valsania, MD, Carlo Martinoli, MD
Article includes CME test
Objectives—The purposes of this study were to describe a technique for treatment of
meralgia paresthetica (lateral femoral cutaneous neuropathy) using ultrasound guidance and to report the results of treatment.
Methods—Twenty consecutive patients (7 male and 13 female; age range, 23–66 years;
mean, 39 years) with meralgia paresthetica confirmed by electromyography were
treated with perineural injection of 1 mL of methylprednisolone acetate (40 mg/mL)
and 8 mL of mepivacaine, 2%, under direct ultrasound guidance. Main outcome measures included the technical success of the procedure, visual analog scale score for the lateral femoral cutaneous nerve (pain, burning sensation, and paresthesia), and visual
analog scale global quality of life score.
Results—Technical success (successful nerve block at the distribution of the lateral
femoral cutaneous nerve) was achieved in all patients. Five patients felt slight sharp pain
during needle insertion. The symptoms in 16 patients (80%) diminished progressively
after the first week. The 4 remaining patients (20%) required a further perineural injection. The symptoms disappeared in all patients 2 months after injection (mean visual
analog scale score ± SD for lateral femoral cutaneous neuropathy at baseline, 8.1 ± 2.1;
at 2 months, 2.1 ± 0.5; t = 6.2; P < .001). The mean visual analog scale quality of life
scored decreased from 6.9 ± 3.2 to 2.3 ± 2.5 (t = 5.3; P < .002).
Received March 31, 2011, from the Department of
Radiology, National Institute for Cancer Research,
Genoa, Italy (A.T.); Departments of Radiology
(G.S., F.L., N.P.) and Neurology (V.V.), Santa
Corona Hospital, Pietra Ligure, Italy; and Department of Radiology, Department of Surgical
Sciences and Integrated Diagnostics, University of
Genoa, Genoa, Italy (C.M.). Revision requested
April 15, 2011. Revised manuscript accepted for
publication May 2, 2011.
Preliminary data from this article were presented as a scientific communication at the 96th
Scientific Assembly and Annual Meeting of the Radiological Society of North America; November
30, 2010; Chicago, Illinois.
Address correspondence to Alberto Tagliafico,
MD, Institute of Anatomy, Department of Experimental Medicine, University of Genoa, Largo
Rosanna Benzi 8, 16132 Genoa, Italy.
E-mail: [email protected]
Conclusions—Treatment of meralgia paresthetica with ultrasound-guided perineural
injections resulted in substantial symptom relief in most patients 2 months after injection. Randomized placebo-controlled trials of this treatment should be considered in the
future.
Key Words—injection; lateral femoral cutaneous nerve; meralgia paresthetica; ultrasound
L
ateral femoral cutaneous nerve compression and entrapment
are rare and occur more commonly in obese patients and in
pregnancy because of abdominal bulging over the inguinal
ligament, with subsequent compression of the nerve at the lateral
end of the inguinal ligament. Symptoms may be worsened by walking or prolonged standing and typically disappear with weight loss,
abdominal muscles exercises, or delivery. Lateral femoral neuropathy causes the syndrome of meralgia paresthetica, which is characterized by numbness, hypersensitivity, and paresthesia in the
anterolateral region of the thigh which, is the area of distribution of
©2011 by the American Institute of Ultrasound in Medicine | J Ultrasound Med 2011; 30:1341–1346 | 0278-4297 | www.aium.org
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Tagliafico et al—Ultrasound-Guided Treatment of Meralgia Paresthetica
this nerve.1 Local anesthetics are usually used to block the
lateral femoral cutaneous nerve before surgical procedures
and to confirm lateral femoral cutaneous neuropathy.
Moreover, local anesthetics may also be used to treat lateral
femoral cutaneous neuropathy.2–4 Blockade of the lateral
femoral cutaneous nerve has been classically described
using anatomic landmarks, but the anatomic variability of
the nerve may be responsible for failure rates as high as
60%.5
Ultrasound guidance has been shown to be particularly suitable for injection of tiny and superficial structures
such as the lateral femoral cutaneous nerve, overcoming
the anatomic variability in most patients.6–10 It has recently
been suggested that ultrasound guidance can facilitate
blockade of the nerve for diagnostic and therapeutic purposes and may be particularly beneficial in patients with
challenging surface anatomic landmarks and when lowvolume injections are desired.10 However, that suggestion
arose from a retrospective evaluation of 10 patients treated
without a standardized protocol.10 Moreover, in a very preliminary study, it was reported that treatment of lateral
femoral cutaneous neuropathy under ultrasound guidance was effective in reducing patient discomfort.11,12
No defined “evidence-based” treatment exists for this condition. Its has been suggested that injection of the lateral
femoral cutaneous nerve may be attempted to treat patients with meralgia paresthetica who do not respond to
oral medications or conservative measures.11 Given the
limited experience existing in the literature and in clinical
practice regarding ultrasound-guided treatment of this
condition, the purposes of our study were to describe a
technique for treatment of meralgia paresthetica under
ultrasound guidance and to report the outcomes obtained
with this technique.
Materials and Methods
Between June 2009 and January 2011, 20 consecutive patients (7 male and 13 female; age range, 23–66 years;
mean, 39 years; body mass index range, 20.14–31.12
kg/m2; mean, 25.22 kg/m2) with a diagnosis of meralgia
paresthetica (bilateral in 1 patient) were included in this
prospective study. Patients were referred to the sonography unit for treatment with ultrasound-guided percutaneous perineural injection of methylprednisolone acetate
and a local anesthetic. The diagnosis of meralgia paresthetica was established from the following indicators: clinical history, physical examination, electromyographic
findings (lateral cutaneous nerve amplitude potential <10
μV, latency >3.5 milliseconds, and normal thigh muscle
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needle examination findings), symptoms lasting for at least
6 weeks, no evidence of other specific diseases of the musculoskeletal system after physical examination (eg, normal
strength and no thigh muscle atrophy), and exclusion of
other causes of pain or sensory disturbances.13,14 The diagnosis was made by a neurologist and a neurosurgeon
with 15 and 11 years of experience, respectively.
The patients were given detailed information on the
procedure, and informed written consent was obtained
from all of them. The study was approved by the Institutional Review Board.
Technique
The procedure in all cases was performed by 3 sonographers with expertise in interventional musculoskeletal
procedures (G.S., F.L., and A.T.) using a commercially
available ultrasound scanner equipped with a 7- to 17MHz transducer. The anterior superior iliac spine was
palpated and visualized with the ultrasound probe as a hyperechoic structure with posterior acoustic shadowing.
The technical approach described was adapted from previous studies.13
The perineural injection technique involved the following steps:
Location of the Anterior Superior Iliac Spine
With the patient in the supine position, the transducer was
placed over the pathologic superior iliac region at the level
of the anterior superior iliac spine. The lateral end of the
probe was placed on the anterior superior iliac spine, and
the medial end extended medially in an anatomic transverse
plane. With the probe in this position, the medial end of the
probe was angled slightly in a caudal direction so the transducer was parallel with the inguinal ligament. The transducer
was gently moved in a mediocaudal direction while the operator searched for the echo signature of the lateral femoral
cutaneous nerve. Using this approach, the nerve appeared
in cross section as an oval structure on short-axis images and
tubular on longitudinal images (Figure 1).
Several sweeps were occasionally necessary to visualize the lateral femoral cutaneous nerve because of the
anatomic variability of the nerve. Once the nerve was visualized in a transverse plane, the nerve was traced proximally
and distally to confirm its appropriate course toward the
lateral thigh. The nerve was visualized in a longitudinal
plane for confirmation as well.
Location of the Puncture Site
Axial sonographic sections were obtained on the anterior
superior iliac spine, and once situated with the nerve in the
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center of the probe, we moved the transducer medially to
allow easier needle access. The needle was inserted by a
lateral or coaxial approach. The approach was tailored depending on the position of the lateral femoral cutaneous
nerve relative to the anterior superior iliac spine.
Figure 1. A, Short-axis sonogram over the anterior superior iliac spine
(ASIS) showing the inguinal ligament (arrowheads) and the normal lateral femoral cutaneous nerve (arrow). B, Confirmatory long-axis sonogram over the lateral femoral cutaneous nerve at the level of the anterior
superior iliac spine showing the nerve as a tiny structure (arrows).
C, Anatomic position of the nerve.
Perineural Injection
A
Under rigorous aseptic conditions, the transducer was inserted into a sterile bag, and sterile gel was applied to the
area of interest. The needle was advanced under direct
ultrasound visualization in a longitudinal view, whereas the
lateral femoral cutaneous nerve was visualized in a shortaxis view. Injection of the drug mixture resulted in perineural spreading that resembled a donut (Figure 2). We
then performed percutaneous perineural injection of 1 mL
of methylprednisolone acetate (40 mg/mL) and 8 mL of
mepivacaine, 2%, using a 22-gauge spinal needle under
direct ultrasound guidance. Needle insertion was performed by a freehand technique With this method, one
hand held the transducer, and the free hand inserted the
needle. This technique allowed changes in the needle
direction during puncture. Moreover, the needle had to be
inserted at an angle that normally is not supported by commercially available devices.
All of the patients were followed weekly for the first 3
months by their referring physicians (neurologists and
neurosurgeons).
Main Outcome Measures
Two parameters were measured before the first treatment
and during follow-up. First, lateral femoral cutaneous neuropathy symptoms (pain, burning sensation, and paresthesia) were evaluated by a 10-point visual analog scale
ranging from 0 (no symptoms) to 10 (intolerable symptoms). Second, the influence of lateral femoral cutaneous
neuropathy on the global quality of life was evaluated by a
10-point visual analog scale ranging from 0 (no influence
on quality of life) to 10 (very low quality of life). This
method showed good validity and excellent reliability.14 A
repeated (dependent) measures t test was used to evaluate the differences before and after the treatment. P < .05
was considered statistically significant. Moreover, the technical success of the procedure was assessed at the time of
injection. The procedure was considered successful when
an effective block in the distribution of the lateral femoral
cutaneous nerve was obtained. The average time of time
of the procedure was recorded with a stopwatch. Local and
general complications related to the local anesthetic and
corticosteroid were recorded.
J Ultrasound Med 2011; 30:1341–1346
B
C
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Tagliafico et al—Ultrasound-Guided Treatment of Meralgia Paresthetica
Results
All patients had satisfactory ultrasound-guided perineural
injections. The average time for the procedure was 12 minutes (range, 5–14 minutes), mainly depending on the time
Figure 2. Ultrasound-guided injection around the lateral femoral cutaneous nerve. A, The needle (arrows) reaches the nerve (arrowhead).
B, The therapeutic solution is injected in the perineural tissues (star) and
spaces the nerve out from the adjacent structures. C, Illustration of the
procedure.
A
needed to find the lateral femoral cutaneous nerve. Five
patients felt slight sharp pain in the anterolateral thigh during needle insertion; the pain disappeared immediately
after needle repositioning. After injection, no local or general complications were observed. The symptoms diminished progressively after the first week in 16 patients
(80%). The 4 remaining patients (20%) required a further
injection because the pain had not remitted. The symptoms disappeared in all patients 2 months after perineural
injection (mean visual analog scale score ± SD related to
lateral femoral cutaneous neuropathy at baseline: 8.1 ± 2.1;
at 2 months: 2.1 ± 0.5; t = 6.2; P < .001). The mean visual
analog scale quality of life decreased from 6.9 ± 3.2 to 2.3
± 2.5 (t = 5.3; P < .002).
Discussion
B
C
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The lateral femoral cutaneous nerve is purely sensory; it
arises from the L2 and L3 spinal nerve roots, travels downward lateral to the psoas muscle, and then crosses the iliacus muscle. Near the anterior superior iliac spine, the nerve
courses in contact with the lateral aspect of the inguinal ligament and innervates the lateral thigh. Finally, the nerve
divides into anterior and posterior branches; however,
these terminal branches are not visible on sonography.
Anatomic studies showed that the distance from the lateral femoral cutaneous nerve to the anterior superior iliac
spine at the inguinal ligament can range from 3 mm to 7.3
cm.6,8,15 In a study by Hospodar et al,6 the course of the
nerve was variable but was most commonly found 10 to
15 mm from the anterior superior iliac spine, although it
was found as far medially as 46 mm. Meralgia paresthetica
is a lateral femoral cutaneous nerve entrapment syndrome
causing burning, numbness, and paresthesias along the
proximolateral aspect of the thigh. It is idiopathic most patients but can also be caused by trauma (avulsion fracture
of the anterior superior iliac spine), pelvic and retroperitoneal tumors, stretching of the nerve due to prolonged leg
and trunk hyperextension, leg length discrepancies, prolonged standing, external compression by belts, weight
gain, and tight clothing.16 The initial treatment of meralgia paresthetica is conservative.17 Patients who do not respond to conservative measures may be considered for
surgical decompression.
An alternative to surgery may be administration of
local lidocaine with steroids around the course of the lateral
femoral cutaneous nerve.15 Ultrasound-guided injections
allow real-time visualization of relevant anatomy and needle positioning. In this study, real-time visualization of the
nerve resolved the problem of anatomic variability and
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probably increased the effectiveness of the procedure.
However, we reported a sonographic Tinel sign in 5 patients. This phenomenon was probably due to the wavy
course of the nerve. On the contrary, no patient reported
paresthesia during injection, suggesting that the needle did
not come in direct contact with the nerve for a time sufficient to cause sensory alterations. In this study, sonography identified the nerve in all cases, including 4 obese
patients. This approach guaranteed successful treatment
in every patient. This result was better in comparison to
blind injection of the nerve, in which failure rates reached
60%.5 The success rate in this study was similar to the result obtained previously in a series of 10 patients who underwent sensory blockade of the lateral femoral cutaneous
nerve.10 In this study, the patient population had a lower
body mass index than previously reported.10 No notable
postprocedural short- or long-term complications were observed. It has been reported that femoral and obturator
nerve involvements are possible complications of lateral
femoral cutaneous nerve injections.10 A possible explanation for this difference may have been that the injectate volume was less than the 10- to 15-mL range that has been
considered as a cutoff to avoid complications. Moreover,
the operator ability in performing this kind of procedure is
important for minimizing complications.
Several limitations of the study should be taken into
account. First, we did not have a control group, and the
follow-up duration was short. Another limitation was that
the study evaluated only the effects of 1 or 2 injections.
From this study, it is not possible to determine whether
some patients might benefit from more than 2 injections.
However, after 2 injections, all patients reported improvement of symptoms, and none of them required a
third injection. Another possible limitation was the relatively low number of patients evaluated; however, to the
best of our knowledge, this study included the largest
number of patients treated under ultrasound guidance to
date. Moreover, the results of this study were both clinically and statistically significant. Ultrasound guidance is
thought to be superior to blind techniques. However, the
efficacy of this procedure is yet to be proven; no randomized controlled or quasirandomized controlled trials are
available.17 A strength of the study was that the accuracy
of needle placement near the lateral femoral cutaneous
nerve was proven, and the study design was prospective
using a standardized protocol. The study provides another
example of how a ultrasound-guided technique increases
accuracy.18 We believe that an ultrasound-guided approach may enhance the therapeutic effect of the injected
drugs.
J Ultrasound Med 2011; 30:1341–1346
In conclusion, we believe that ultrasound-guided
perineural injection of the lateral femoral cutaneous nerve
is quick, simple, economical, and effective. This procedure
may be an interesting option in the percutaneous treatment of meralgia paresthetica. Randomized placebo-controlled trials of this treatment should be considered in the
future.
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