Meralgia Paraesthetica

Condition

Compression of the ‘lateral cutaneous nerve of the thigh’ where is enters the upper thigh through an opening between a strong ligament (inguinal ligament) and most upper and frontal bone of the pelvis (anterior superior iliac spine). The nerve only has fibres for sensation of a patch of skin just above the knee and does not supply any muscles. There is a long list of possible causes and sometimes, no cause is found. Causes include wearing of tight belts or girdles, diabetes, obesity, pregnancy or after surgery in this area. Massaging the area and lying flat can improve the symptoms.

Symptoms

Patients notice numbness or burning sensation in patch just above the knee. There might be an increased sensation and the area can become painful to touch (hyperaesthesia or dysaesthesia). Walking or prolonged standing can worsen the symptoms.

Clinical signs

Numbness of a patch just above the knee (the area can considerable vary in size).

Complications

Permanent numbness and pain of this area.

Investigations

A thorough clinical examination is important. A trapped nerve in the upper lumbar spine (L2/L3) can cause similar symptoms but in contrast to the meralgia paraesthetica can cause weakness. If there is only numbness – which is usually not troublesome – and no pain and otherwise a completely normal neurological examination, no further investigation is required. If there is any doubt about the clinical diagnosis and before any surgical intervention patients should have neurophysiological tests (nerve conduction studies). An MRI scan of the lumbar spine (lower back) might also be indicated in unclear cases.

Treatment

Non-surgical treatment includes weight loss, removing offending articles like belts and strengthening of abdominal muscles can improve the condition. In many cases the symptoms resolve spontaneously without any specific treatment. It there is pain or dysaesthesia surgical exploration and decompression or in some case cutting (sectioning) is indicated.

Outlook

Conservative treatment can often lead to significant improvement and avoid surgery. However, surgery can be effective and has very small risks. Surgery involves exploring the nerve and freeing it up. It some cases, the nerve is sectioned (cut). This will leave the patient with a numb but painless area in most cases.