Acta Neurochir (2005) [Suppl] 92: 61–62 6 Springer-Verlag 2005
Printed in Austria
Femoral nerve entrapment
A. Azuelos, L. Coro`, and A. Alexandre
EU.N.I. European Neurosurgical Institute, Treviso, Italy
Summary
We present 30 cases of femoral nerve entrapment (1999–2003, age range 35–65 yrs), in 13 patients with diagnosis of idiopathic com- pression and 7 patients of neurovascular conflict. The compression, in the other 10 patients, was iatrogenic: 3 patients following cardiac catheterization for balloon valvotomy, 2 patients following intra- abdominal vascular surgery and 5 patients following laparoscopic hernia treatment. Microsurgical nerve decompression, and the elim- ination of neurovascular conflict gave satisfactory results. The best result has been observed in neurovascular conflict cases.
Keywords: Femoral nerve; entrapment; lumbar plexus.
Introduction
The femoral nerve, the largest branch of the lumbar plexus, is formed in the substance of the psoas major muscle where it derives its fibres from the posterior divisions of the L2, L3, L4 nerves. This nerve has both motor and sensory functions. The motor function in- volves control of iliopsoas and quadriceps muscles and the sensory function involves skin sensation over the medial-anterior shin. The femoral nerve may be involved in open (penetrating injuries) and closed (ia- trogenous; neurovascular conflict or idiopathic) in- juries in the femoral triangle.
Pathology
All segmentary compressions in nerves are accom- panied by a component of ischemia. In front of a pro- gressive or repetitive deforming force, the nerve be- comes mechanically ‘‘ribbon like’’ [4, 8]. The increase of the intraneural pressure causes a venous slow down with oedema of the a¤ected segment, adding a greater deforming pressure [2, 9]. So, the area a¤ected by
oedema is invaded by fibroblasts that will produce a greater epineural and perineural fibrosis.
Olsson [3] has studied the anatomical details of nerve structure which may be the base for fibrotisation processes. Epineurium, is similar to other connective tissue rich parts in the body, and its extracellular fluid is free to di¤use [5]. The walls of the endoneurium are entirely covered by a basal lamina which surrounds the outer plasma membrane surface of the Schwann cells, the endoneurial vessels and the perineurial cells apparently forming a stabilizing structure.
Endoneurial fluid circulation depends on two major forces, net hydrostatic pressure and net osmotic pres- sure. The lack of lymphatics in nerve fascicles might render the removal of endoneurial fluid di‰cult [6, 7].
Perineurium creates a fluid environment around the nerve fibres of optimal composition for transmission of electrical impulses [1].
Early and late oedema of the vasogenic type is as- sociated with elevated endoneurial fluid pressure and microcirculatory disturbances. Proliferation of fibro- blasts, changes in the composition of the matrix and collagen formation may result in endoneurial fibrosis at the site of the lesion and distal to it. Nerve damage due to an injury may be further aggravated by oedema increasing endoneurial pressure which might compro- mise blood flow in the fascicles. Fibrosis, either at the site of the primary injury or in the distal part under- going Wallerian degeneration may be so marked that axonal regeneration and nerve repair are interfered with.
Clinical history and physical findings are the most important factors for diagnosis. To localize the site of the compression, the conduction velocity study by means of EMG and the Tinel sign are used.
Indications for treatment
– Persistence of an irritative syndrome that is not solved within a reasonable period of time with pos- tural treatment and anti-inflammatory drugs.
– Either motor or severe and painful sensitive deficit- ary syndrome.
The surgical technique is composed of macro and microsurgical procedures.
Materials and methods
We present 30 cases of femoral nerve entrapment (1999–2003, age range 35–65 yrs).
In 20 patients the compression of the femoral nerve was not dependent upon external factors: 13 patients with diagnosis of idio- pathic compression and 7 patients with neurovascular conflict. The compression of the other 10 patients was iatrogenic: 3 patients fol- lowing cardiac catheterization for balloon valvotomy, 2 patients following intra-abdominal vascular surgery and 5 patients following laparoscopic hernia repair.
Surgical technique
We prefer general anaesthesia with intraoperative nerve electrostimulation.
The macrosurgical procedure is performed in order to release the extrinsic cause of the nerve’s compres- sion. On the other hand, an objective of the micro- surgical approach is the detailed observation of the lesions produced by compression on the surface and within the femoral nerve.
The release of the fibrotic tissue allowed in 7 cases to separate the artery from the nerve, allowing solution of the neurovascular conflict. In these cases deformation
of the nerve structure was observed in the site of con- tinuous microtrauma due to vascular pulsation.
Results and conclusion
The outcome was simple with complete motor and pain recovery in the lower limb. The best result has been observed in neurovascular conflict cases.
Sensory recovery was rapid and rather good in ia- trogenic cases, and was obtained after 12 months in the
‘‘pure’’ entrapment cases.
References
1. Dahlin LB, Rydevik B, McLean WG (1984) Changes in fast axonal transport during experimental nerve compression at low pressures. Exp Neurol 84: 29–36
2. Millesi H (1997) Personal Communication
3. Olsson Y (1990) Microenvironment of the peripheral nervous system Gut Rev Neurobiol 5: 265–311
4. Ramon Y, Cajal S (1917) Degeneracion y regeneracion experi- mental de los nervios perifericos. Trab Lab Invest Biol XV:
301–358
5. Rydevik B, Lundborg G (1977) Permeability of intraneural mi- crovessels and perineurium following acute, graded experimental nerve compression. Scand J Plast Reconstr Surg 11: 179–187 6. Rydevik B, McLean WG, Sjostrand J (1980) Blockage of axonal
transport indiced by acute graded compression of the rabbit vagus nerve. J Neurol, Neurosurg Psychiatry 43: 690–698 7. Rydevik B, Lundborg G, Bagge U (1981) E¤ects of graded com-
pression on intraneural blood flow. J Hand Surg 6: 3–12 8. Weiss P (1943) Endoneural oedema in constricted nerve. Anat
Rec 84: 491–522
9. Weiss P (1944) Downing of axoplasm in constricted nerves, a sign of perpetual growth in nerve fibres. Anat Rec 88: 464–468
Correspondence: Alberto Alexandre, M.D., EU.N.I. European Neurosurgical Institute, Via Ghirada 2, 31100 Treviso, Italy. e-mail:
alexandre@eunionline.com
62 A. Azuelos et al.: Femoral nerve entrapment
