Letter to the Editor. Meralgia paresthetica: what to do?

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  • University of Wisconsin, Madison, WI
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TO THE EDITOR: I read the interesting article by Malessy et al. describing the technique and results of dynamic decompression of the lateral femoral cutaneous nerve (LFCN) to treat meralgia paresthetica (MP) (Malessy MJA, Eekhof J, Pondaag W. Dynamic decompression of the lateral femoral cutaneous nerve to treat meralgia paresthetica: technique and results. J Neurosurg. 2019;131(5):1552–1560).1 The article describes a layer of fascia superficial to the LFCN and another layer deeper to the nerve. These were previously clearly described as the LFCN canal by our group and independently confirmed by Xu et al.2,3 The LFCN canal is an anatomical fact that cannot be ignored and should be the basis of any surgical approach. It clearly defines the planes that need to be decompressed in surgery on the LFCN without the need for dynamic testing. In addition, many patients with MP have the nerve in proximity to or riding over the iliac crest at the region of the anterior superior iliac spine (ASIS). The technique described by Malessy et al. does not address this patient population since it does not tell us how to deal with the bone. The dynamic decompression as described raises some concerns. Most MP patients have a high body mass index, so taking that heavy lower limb and moving it in flexion, abduction, and extension seems impractical and not reproducible and presents the risks of breaking sterility and inflicting injury to the person while lifting up the leg. The LFCN canal has well-defined anterior and posterior walls that must be decompressed regardless of the findings with limb mobilization.2 The LFCN transposition as described by Hanna addresses the issue of proximity to bone by mobilizing the LFCN medially for about 2 cm, which will eliminate the nerve rubbing against the bone.4–6 This situation was not observed in the authors’ series either because of ethnic differences or more likely due to a lack of intraoperative measurements prior to decompression. While proximity of the LFCN to the ASIS is rare in human cadavers, it is very common in MP patients. This means it is part of the pathology and needs to be addressed by transposition. It is likely that Malessy and colleagues actually performed transpositions, but it is hard to confirm since no measurements were taken. This is very obvious in their Fig. 1A, where the nerve is very close to the ASIS (labeled 2) prior to deep decompression, then is clearly medialized after deep decompression in Fig. 1C.1

Disclosures

The author reports no conflict of interest.

References

  • 1

    Malessy MJA, Eekhof J, Pondaag W. Dynamic decompression of the lateral femoral cutaneous nerve to treat meralgia paresthetica: technique and results. J Neurosurg. 2019;131(5):15521560.

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  • 2

    Hanna A. The lateral femoral cutaneous nerve canal. J Neurosurg. 2017;126:972978.

  • 3

    Xu Z, Tu L, Zheng Y, Fine architecture of the fascial planes around the lateral femoral cutaneous nerve at its pelvic exit: an epoxy sheet plastination and confocal microscopy study. J Neurosurg. 2019;131(6):18601868.

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  • 4

    Hanna A. Transposition of the lateral femoral cutaneous nerve. J Neurosurg. 2019;130(2):496501.

  • 5

    Hanna A, Hanna B. Response To: Anatomical considerations on transposition of the lateral femoral cutaneous nerve. Clin Anat. 2018;31(8):12221224.

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  • 6

    Hanna AS. Lateral femoral cutaneous nerve transposition: renaissance of an old concept in the light of new anatomy. Clin Anat. 2017;30(3):409412.

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  • 1 Leiden University Medical Center, Leiden, The Netherlands, and
  • 2 Alrijne Medical Center, Leiden, The Netherlands
Keywords:

Response

We have read with interest the letter from Dr. Hanna. Since our publication in 2018, in which we reported the outcome of dynamic decompression of the LFCN in idiopathic MP, the total number of surgically treated patients with sufficient follow-up has amounted to 30. In the vast majority of patients, the pain completely disappeared and skin sensation recovered to (near) normal. As described, we first decompress the LFCN with the leg in a neutral position. Subsequently, we move the leg in extension and abduction. In doing so, we observed that fibers located dorsal to the LFCN tighten and cause compression at various locations. These could be fibers of the musculotendinous origin of the sartorius muscle at the level of the ASIS, the iliac fascia proximal to the ASIS, or the lateral aspect of the fascia of the sartorius muscle distal to the ASIS. Additionally cutting these fibers, which we call “dynamic decompression,” is likely the distinctive factor that positively distinguishes our results from those of others who perform the same decompression but only with the leg in a neutral position.1,2 The good results following dynamic decompression encourages us to continue using this technique.

Dr. Hanna does not move the leg out of fear of infection and physical strain and therefore misses the observation of the dynamics of compression of the LFCN. This is unfortunate because this relatively easy and simple procedure takes only a few minutes to perform, is reproducible, and does not break sterility. Additionally, it is not a burdensome procedure regardless of body mass index. More importantly, moving the leg provides important information.

In our consecutive series, the entrapment site of the LFCN was consistently found medial to the ASIS. By observing the LFCN during limb movement at the end stage of dynamic decompression, it becomes clear that “riding” over the ASIS does not occur, nor did we see “rubbing against the bone.” Complete dorsal decompression and release induce a posterior shifting of the LFCN. We did not perform medial transposition as was first described by Keegan and Holyoke in the Journal of Neurosurgery3 and now proposed again by Dr. Hanna.4 In view of our observations and results, there is no need for medial transposition. Fixation of the LFCN in this position with a stitch is, in view of the dynamics, in fact contraindicated.

References

  • 1

    Siu TL, Chandran KN. Neurolysis for meralgia paresthetica: an operative series of 45 cases. Surg Neurol. 2005;63(1):1925.

  • 2

    Son BC, Kim DR, Kim IS, Neurolysis for meralgia paresthetica. J Korean Neurosurg Soc. 2012;51(6):363366.

  • 3

    Keegan JJ, Holyoke EA. Meralgia paresthetica. An anatomical and surgical study. J Neurosurg. 1962;19(4):341345.

  • 4

    Hanna A. Transposition of the lateral femoral cutaneous nerve. J Neurosurg. 2019;130(2):496501.

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Contributor Notes

Correspondence Amgad Hanna: ah2904@yahoo.com.

INCLUDE WHEN CITING Published online March 20, 2020; DOI: 10.3171/2019.10.JNS192708.

Disclosures The author reports no conflict of interest.

  • 1

    Malessy MJA, Eekhof J, Pondaag W. Dynamic decompression of the lateral femoral cutaneous nerve to treat meralgia paresthetica: technique and results. J Neurosurg. 2019;131(5):15521560.

    • Search Google Scholar
    • Export Citation
  • 2

    Hanna A. The lateral femoral cutaneous nerve canal. J Neurosurg. 2017;126:972978.

  • 3

    Xu Z, Tu L, Zheng Y, Fine architecture of the fascial planes around the lateral femoral cutaneous nerve at its pelvic exit: an epoxy sheet plastination and confocal microscopy study. J Neurosurg. 2019;131(6):18601868.

    • Search Google Scholar
    • Export Citation
  • 4

    Hanna A. Transposition of the lateral femoral cutaneous nerve. J Neurosurg. 2019;130(2):496501.

  • 5

    Hanna A, Hanna B. Response To: Anatomical considerations on transposition of the lateral femoral cutaneous nerve. Clin Anat. 2018;31(8):12221224.

    • Search Google Scholar
    • Export Citation
  • 6

    Hanna AS. Lateral femoral cutaneous nerve transposition: renaissance of an old concept in the light of new anatomy. Clin Anat. 2017;30(3):409412.

    • Search Google Scholar
    • Export Citation
  • 1

    Siu TL, Chandran KN. Neurolysis for meralgia paresthetica: an operative series of 45 cases. Surg Neurol. 2005;63(1):1925.

  • 2

    Son BC, Kim DR, Kim IS, Neurolysis for meralgia paresthetica. J Korean Neurosurg Soc. 2012;51(6):363366.

  • 3

    Keegan JJ, Holyoke EA. Meralgia paresthetica. An anatomical and surgical study. J Neurosurg. 1962;19(4):341345.

  • 4

    Hanna A. Transposition of the lateral femoral cutaneous nerve. J Neurosurg. 2019;130(2):496501.

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