Pain in the crural area should alert the clinician. Its definition is precise but its presentation often requires a discussion of the differential and etiological diagnosis.
From an anatomical point of view, the crural is the largest terminal branch of the lumbar plexus,
born from the third and fourth lumbar roots and incidentally from the second. It is constituted by the union of these roots in the depth of the psoas muscle, then descends to the external edge of this muscle in the internal iliac fossa, then in front of the psoas, it passes under the crural arch and penetrates the thigh outside. femoral vessels and divides into its terminal branches.
The painful path is from the outer part of the buttock to the anterior part of the knee and then antero-internally, or even along the tibial crest depending on whether the path is L3 or L4.
The pain usually settles quickly, it is quickly permanent, it reaches a high intensity and very often has a nocturnal character. The dysesthesias are frequent and their topography on the antero-internal face of the knee sign the high radicular damage.
It brings few topographical and etiological arguments. The Léri (Inverse Laségue) maneuver can trigger the pain.
He objectifies the suffering of the crural nerve:
– very frequent motor deficiency requiring testing to highlight it sometimes inducing steal and fall;
– abolition or diminution of the patellar reflex, which one will look for by comparison with the opposite side;
– dysaesthesia or hypoesthesia of the anterior aspect of the thigh or anterior leg.
It allows to eliminate a coxopathy.
It eliminates another neuralgia:
– paresthetic meralgia;
– obturator neuralgia;
– genitocrural neuralgia.
Benign vertebral origin is the most common:
The advent of imaging has made it possible to:
– make the diagnosis of foraminal hernia L2-L3 or L3-L4, or even extraforaminal L4-L5 at the origin of cruralgia;
– appreciate the impact of a static disorder or a pagetic vertebra;
– measure ductal stenosis, particularly common in L3-L4;
– more rarely, highlight a spondylodiscitis.
The fear of a tumoral attack must always be present:
Lymphomas, myeloma, metastases, intraspinal tumor.
The slightest doubt about standard snapshots makes it necessary to move rapidly towards additional examinations and in particular to MRI.
Various extraspinal causes (anatomical path of the crural):
They must be sought after any cruralgia that does not give way or if the spinal signs are absent from the outset.
– A visceral, renal, pelvic or ganglionic cause:
• abdominopelvic ultrasound by an informed operator remains the first step of the additional examinations to be requested,
• the biological assessment looking for an inflammatory syndrome is required faster than in the presence of sciatica;
– vascular disease: aneurysm of the abdominal aorta or aortic dissection, vascular pressure or iatrogenic involvement after pelvic surgery;
An exceptionally post-traumatic hematoma of the psoas, which is essentially iatrogenic, linked to an unbalanced anticoagulant treatment to be systematically evoked in a pharmacy treated with anti-vitamin K;
– a bone disorder of the femur revealed by a femoral radio or bone scan.
– Lyme radiculitis.
– Radiculitis zosterian.
– Neuralgia with or without diabetic amyotrophy recalling the importance of the biological assessment in cruralgia. It must be kept in mind that this is a diagnosis of elimination.
Cruralgia is often hyperalgic and requires the use of Level III analgesics more often than sciatica.
The treatment of the cause is often essential to obtain sedation.
Complementary examinations are more often and more rapidly prescribed than in other types of radiculalgia.
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