Meralgia paraesthetica is a pain syndrome and one of many different ones potentially presenting to a physiotherapist or doctor for diagnosis and treatment. The typical symptoms are numbness, pins and needles and pain in the lateral and anterior parts of the thigh. In the 19th century this condition was described and the link made with problems to do with the lateral femoral cutaneous nerve, a purely sensory nerve. This nerve only deals with sensations and has no role with muscular action but transmits sensations from the thigh areas supplied by it. The incidence of this problem is not particularly clear but it could be under recognised.
This condition can be mistaken for a series of other musculoskeletal conditions such as nerve root compression, referred spinal pain and trochanteric bursitis and may be bilateral at times. The most common cause of this syndrome is inappropriate pressure on the on the nerve at particular points where it can be trapped. Being overweight may be a risk factor for this condition and it has been recorded as being caused by a tight belt. Various surgical procedures can be aggravating factors such as hip replacement, bone grafting and surgery to the quadriceps.
There are several areas along the length of this cutaneous nerve where it can suffer compression, as it exits from inside the psoas muscle, courses in close proximity to the inguinal ligament, runs close to the bony lip of the front of the pelvis and finally emerges into the thigh through the tough layer of connective tissue called the fascia lata. A neurapraxia is the name given to this least damaging form of nerve compressive damage in which case the nerve loses some of its sheath of insulation known as the myelin sheath.
In a neurapraxia the nerve axon itself is not damaged and this grade of injury is one which recovers completely over a relatively short period up to a few months. If the axon tube itself is disrupted then the injury is classified as an axonotmesis, with the length of nerve axon degenerating all the way up to its cell body. Regeneration from this point is extremely slow leading to a very long period the patient has to wait if the injury is to resolve over time. A nerve which has been severely injured so the cut ends do no longer contact each other has no likelihood of showing any recovery unless surgery is employed.
On examination the patient''s history should include enquiries about any traumatic events which could have a bearing on the condition. Physical examination will find altered sensibility in the front and side of the thigh, symptoms which include pain, burning, numbness, reduced feeling and pins and needles. The usual onset of symptoms is gradual and slow and they do not go beyond the knee area, with pain often sharper and burning but can also be a duller ache. The area of symptoms on the thigh can vary with the severity of the conditions, with exclusively anterior or lateral thigh symptoms reported.
Establishing and removing any obvious source of nerve compression is the initial goal of assessment and treatment, for example loosening of close fitting clothing or a tight belt or the lightening of equipment carried on the waist. Weight loss may be all that is needed for a significant reduction in symptoms in obese patients. Ergonomic evaluation of work activities and postures may be useful to identify risky patterns. Anaesthetic or corticosteroid injections may be administered to the locally inflamed area to treat this and interrupt the cycles of pain.
The variability in the position and anatomical path followed by the lateral cutaneous nerve makes the surgeon''s job difficult in deciding on the site of intervention. The nerve and the symptoms are very likely to settle without further treatment once the compression problems have been resolved. Injections or surgery can follow if modifying the patient''s day to day activities has not helped. Surgery varies but includes neurolysis, cutting the nerve, moving the nerve and decompression wherever along the track the nerve is potentially compromised. Follow up reports on patient groups after surgical intervention are generally positive.