Meralgia paraesthetica

Introduction

Meralgia paraesthetica comes from the Greek words meros for thigh and algos for pain and is often described as a syndrome of paraesthesia or anaesthesia in the distribution of the lateral femoral cutaneous nerve (LFCN). It is an entrapment mononeuropathy of the LFCN, but can also be iatrogenic after a surgical procedure, or result from a neuroma. Although uncommon, meralgia paraesthetica is not rare and is hence probably underdiagnosed.

Epidemiology

Incidence: 43.00 cases per 100,000 person-years
Peak incidence: 30-40 years
Sex ratio: 1:1





















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Aetiology

Risk factors

Obesity
Pregnancy
Tense ascites
Trauma
Iatrogenic, such as pelvic osteotomy, spinal surgeries, laparoscopic hernia repair and bariatric surgery. In some cases, may result from abduction splints used in the management of Perthe's disease.
Various sports have been implicated, including gymnastics, football, bodybuilding and strenuous exercise.
Some cases are idiopathic.

Pathophysiology

Anatomy

The LFCN is primarily a sensory nerve, carrying no motor fibres.
It most commonly originates from the L2/3 segments.
After passing behind the psoas muscle, it runs beneath the iliac fascia as it crosses the surface of the iliac muscle and eventually exits through or under the lateral aspect of the inguinal ligament.
As the nerve curves medially and inferiorly around the anterior superior iliac spine (ASIS), it may be subject to repetitive trauma or pressure.
Compression of this nerve anywhere along its course can lead to the development of meralgia paraesthetica.

Clinical features

Patients typically present with the following symptoms in the upper lateral aspect of the thigh:

Burning, tingling, coldness, or shooting pain
Numbness
Deep muscle ache
Symptoms are usually aggravated by standing, and relieved by sitting
They can be mild and resolve spontaneously or may severely restrict the patient for many years.

Signs:

Symptoms may be reproduced by deep palpation just below the ASIS (pelvic compression) and also by extension of the hip.
There is altered sensation over the upper lateral aspect of the thigh.
There is no motor weakness.

Investigations

Investigations:

The pelvic compression test is highly sensitive, and often, meralgia paraesthetica can be diagnosed based on this test alone
Injection of the nerve with local anaesthetic will abolish the pain. Using ultrasound is effective both for diagnosis and guiding injection therapy in meralgia paraesthetica
Nerve conduction studies may be useful.