Meralgia Paraesthetica

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Defenition / Description

Meralgia Paraesthetica (MP), also known as Bernhardt-Roth or LFCN (lateral femoral cutaneus nervus) neuralgia, comes from the greek term meros algos meaning thight pain. 
MP is caused by damage to the nervus cutaneus femoris lateralis (LFCN). The most common cause of damage to this nerve is entrapment at the level of the inguinal ligament. 

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Clinically Relevant Anatomy

The lateral femoral cutaneous nerve (LFCN) of the thigh is normally a branch of the posterior disunity of the L2 and L3 spinal nerves. It travels through the pelvis heading towards the anterior superior iliac spine (ASIS). Then it usually exits the lesser pelvis below the inguinal ligament (IL), anterior to the ASIS, bifurcates into an anterior and posterior division along the length of the thigh. There it supplies sensory innervation to the skin of the anterolateral and lateral aspects of the thigh. 

Epidemiology / Etiology

Although spontaneous MP can occur in any age group, it is most frequently noted in 30- to 40- year-olds. Its incidence in children may be higher than previously recognized. One-third of all children treated for osteoid osteoma developed MP. There is yet no consensus whether there is sex predominance. But in one study that evaluated 150 cases of MP, there was a higher incidence in men. 
As mentioned before a mononeuropathy of the LFCN, is commonly due to entrapment of this nerve as it passes through the inguinal ligament. The entrapment can have an idiopathic or iatrogenic cause.

•  Idiopathic (or spontaneous) causes

-Mechanical factors: obesity but also in other conditions that increase intra- abdominal volume such as tight clothing, pregnancy and ascites, in which the nerve may be kinked or compressed by the bulging abdomen as it leaves the pelvis. 
-Metabolic factors: diabetes mellitus, alcoholism and lead poisoning. 

•  Iatrogenic causes

Iatrogenic causes can be due to hip replacement or spine surgery. During back surgery the anterior hip can get compressed from the surgical equipment utilized during surgery when the patient is in prone. Also equipment related incidents in individuals who underwent direct lateral and posterior lumbar spinal surgery can cause MP. 

Characteristics / Clinical Presentation

Patients may have symptoms like pain, burning, numbness, muscle aches, coldness, lightning pain or buzzing on the anterolateral aspect of the thigh.  As mention before, in “clinical relevant anatomy”, there it supplies sensory innervation to the skin of the anterolateral and lateral aspects of the thigh. The patient with MP will experience symptoms, superficial as well as deep tissue, in this part of the thigh.

A patient can have light pain with spontaneous resolution or may have more severe pain that limits function. Patients may report pain when standing or walking for a long time. The pain can be reduced in a sitting position, because when sitting, the tension in the LCTN or inguinal ligament reduces. This reduction in tension may result in reduction of the symptoms.  Each patient will have their own specific clinical presentation and distribution of symptoms. 
As mentioned before in “clinical relevant anatomy”, the LFCN supplies sensory innervation to the skin of the anterolateral and lateral aspects of the thigh.

Differential Diagnosis

The differential diagnosis includes L3 lumbar radiculopathy or a femoral neuropathy, although both cause motor loss in addition to the sensory symptoms.  Radiculopathy is a disease where a compressed nerve in the spine causes pain, numbness, tingling or a weakness along the course of the nerve.  Femoral neuropathy occurs when you can’t move or feel your leg due to damaged nerves. The cause can be an injury, prolonged pressure on the nerve or damage from a disease. 

Diagnostic Procedures

The diagnosis of MP is usually clinical, based on the symptoms found at the coherent history and physically examination.  Besides the examination, diagnosis can be based on other additional test like a nerve conduction test of the LFCN.
It is very important to note that MP can sometimes occur in combination with certain red flags. These red flags can be the presence of a tumor or a herniated disc in the described area. MRI or ultrasound examinations are performed when suspecting pelvic tumors including retroperitoneal tumor. Therefore, they must be recognized during the examination and appropriately treated. 

Outcome Measures

To quantify overall health
• SF-12
• Neuropathic pain score To quantify activity level
• UCLA activity scale

To quantify pain, stiffness and physical function
• WOMAC

Examination

• Coherent History Examination

MP is characterized by the presence and history of different symptoms mentioned in “Characteristics & Clinical Presentation”.

• Physical examination

During physical examination, palpation on the lateral part of the inguinal ligament — at the point where the nerve crosses the inguinal ligament — is usually painful. Some patients also present with hair loss in the areas of the LFCN because they constantly rub this area.

• Additional tests

To exclude red flags, pelvic radiography is used to rule out bone tumors. Blood tests and thyroid function tests are used when a metabolic cause is expected.

Medical Management

The aim of treatment for MP is focused on relieving the compression of the LFCN. The first step would be conservative treatment. If this doesn’t help, the next step would be medical treatment. A surgical treatment is indicated when all the above don’t reduce symptoms.

• Conservative management

With the conservative management, the causing factors are identified. We try to influence these factors with a conservative approach. This conservative management entails f.e. weight loss, informing and advising the patient (encourage wearing loose clothing and no tight belts). Pain can be reduced by applying cold packs in the painful area.  (Level of evidence 2c)

•  Medical management

Nerve block: a localized infiltration of the LFCN. This injection with corticosteroids and an analgesic, or more commonly, corticosteroids and local anesthetic agent will reduce pain and improve mobility in most of the MP patients. (level of evidence 2c)
Anti-inflammatory medication and pain medication to reduce (inflammatory) pain. (level evidence 2b)
In patients with MP that were intractable to conservative treatment and had no other cause, we considered pulsed radiofrequency (PRF) neuromodulation of the LFCN.  (level of evidence 4) PRF is a treatment method that reduces pain by generating radio waves
that produce heat. These radio waves are applied through needles into the skin, above the spine. The use of imaging scans can help in determining where the needles should be inserted.

•  Surgery

Surgery should only be adopted when all nonoperative therapies have failed.[3] (level of evidence 4) Conservative management of MP is effective in over 90% of patients, but patients with severe and persistent pain despite adequate conservative management should consider surgical treatment.  (level of evidence 4)
Two surgical techniques have been developed to cure MP.  (level of evidence 4)
• Decompression (also known as neurolysis): a procedure in which the nerve is released from surrounding tissue.
• Neurectomy: a small segment of the nerve is excised at its passage through the inguinal ligament.  (level of evidence 4)

Neurectomy eliminates the positive symptoms but leaves a patch of numbness in the anterolateral thigh which usually reduces in size with time and is often reserved for patients with MP of long duration, especially for those who failed early decompression.  (level of evidence 4)
Successful pain relief is significantly higher with neurectomy than with neurolysis.  (level of evidence 4)

Physical Therapy Management

• Kinesio-Taping

Small-scale pilot studies assert that Kinesio-Taping must be part of the therapy in patients with MP. Kinesio-Taping would reduce the symptoms experienced by a patient. The exact physiological mechanisms are still unknown. This method is hypothesized to help increase lymphatic and vascular flow, decrease pain, enhance normal muscle function, increase proprioception, and help correct possible articular malalignments. Despite the hypothesized benefits, the current evidence is insufficient for MP. Future randomized placebo controlled trials are needed. (level of evidence 5)

•  Acupuncture

The benefits of Acupuncture as an intervention (e.g. needling and cupping) for MP has been shown in clinical trials. The available literature suggests that acupuncture may be effective in the treatment of MP. However, the exact physiological mechanisms are still under investigation. Further investigation is needed.  (level of evidence 5)

•  Transcutaneous Electrical Nerve Stimulation

Transcutaneous electrical nerve stimulation (TENS or TNS) is effective in the treatment of painful peripheral neuropathy like MP. (Level of evidence 1a) It is suggested that TENS activates central mechanisms to provide analgesia. Low frequency TENS activates μ-opioid receptors in spinal cord and brain stem while high frequency TENS produces its effect via δ-opioid receptors.  (level of evidence 1a)

•  Neurostimulation Techniques

Neurostimulation techniques including transcranial magnetic stimulation (TMS) and cortical electrical stimulation (CES), spinal cord stimulation (SCS) and deep brain stimulation (DBS) have also been found effective in the treatment of neuropathic pain as MP.  (level of evidence 1a)

•  Exercise

Exercising for just 30 minutes a day on at least three or four days a week will help you with chronic pain management by increasing: (level of evidence 5)

-Muscle Strength
-Endurance
-Stability in the joints
-Flexibility in the muscles and joints

Possible examples of exercise training are:
1. Aerobic Exercise  (Level of evidence 5)
-Take a brisk walk (outside or inside on a treadmill)
-Take a low-impact aerobics class
-Swim or do water aerobic exercises
-Stationary bicycle indoors

2. Flexibility Exercise (Stretching) (Level of evidence 5) This includes exercising against increasing resistance, use of weights, and isometric exercise.  Nerve stretches can reduce the tightness in the nerves and also help relieve pain that is associated with tight nerves. (Level of evidence 5)

3. Strength Training Exercise  (Level of evidence 5)
Muscle training programs (using a linear pressure resistance device) can improve the inspiratory muscle strength and modulate autonomic function in patients with DAN (diabetic autonomic neuropathy). [25] (Level of evidence 1B)

4. Balance Exercise  (Level of evidence 5)
Programs that incorporate multisensory balance training have a potential to induce adaptive responses in neuromuscular system that enhances postural control, balance and functional ability of women. The training using BOSU may help improve static balance and functional ability in women.  (Level of Evidence 2B)

•  Low level laser therapy (LLLT)

According to the available research, LLLT has positive effects on the control of analgesia for neuropathic pain, but further studies with high scientific rigor are needed in order to define treatment protocols that optimize the action LLLT in neuropathic pain.  (level of evidence 4)

• Weight loss in obese patients

Physiotherapists aim to promote successful weight management and improved general health by appropriately increasing patients’ levels of physical activity. Their assessments are carried out to establish the patients’ current activity levels and any barriers the patient has to increased activity. The physiotherapists then offer a treatment plan aimed at tackling these barriers and promoting the optimal activity for the patient.  (level of evidence 5)

• Manual therapy

There are some case studies regarding MP using manual therapy. The techniques used in these studies are: Active_Release_Techniques (ART), mobilization/manipulation for the pelvis, myofascial therapy for the rectus femoris and illiopsoas, transverse friction massage of the inguinal ligament, stretching exercises for the hip and pelvic musculature and pelvic stabilization/abdominal core exercises. According to available evidence, these interventions may be effective and safe in relieving symptoms of MP. Further high quality research is needed to assess these therapy options. There is a study by Terret citing a case where chiropractic manual treatment of the hip and pelvis resulted in MP.  (level of evidence 4)

Key Research

Jin DM, Xu Y, Geng DF, Yan TB (2010) Effect of transcutaneous electrical nerve stimulation on symptomatic diabetic peripheral neuropathy: a metaanalysis of randomized controlled trials. Diabetes Res Clin Pract 89: 10- 15

Clinical Bottom Line

MP is also known as Bernhardt-Roth or LFCN neuralgia. It is caused by a damage to the nervus cutaneus femoris lateralis. Diagnosis is made on a coherent history and physical examination. MP is mainly treated by physiotherapists using TENS. All other treatment techniques like KT, Acupuncture, LLT and Manual therapy lack strong scientific evidence and need further investigation. Besides the use of TENS, physical therapists can also treat the causes of MP by increasing the activity level of patients suffering from obesity.

Recent Related Research (from Pubmed)

Cheatham SW, Kolber MJ, Salamh PA. MERALGIA PARESTHETICA: A REVIEW OF THE LITERATURE. International Journal of Sports Physical Therapy. 2013;8(6):883- 893

References

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