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At a glance

Entrapment neuropathy of the lateral femoral cutaneous nerve resulting in discomfort and numbness.

Synonym

Familial Meralgia Paraesthetica.

History

First described in 1895 by the German pathologist Martin Bernhardt and later by the Russian neuropathologist Vladimir Karlovich Roth in cavalry soldiers with tight belts. Also in 1895, P. Näcke and Sigmund Freud independently described similar cases on a few patients and themselves.

Incidence

The familial type of meralgia paraesthetica is extremely rare and limited to case reports of familial occurrence in several families.

Genetic inheritance

Inheritance is most likely autosomal dominant. However, the vast majority of cases are acquired and not inherited. Sigmund Freud and one of his sons were affected by this disorder.

Diagnosis

Based on the clinical findings and family history. Ultrasound imaging can be used to visualize entrapment of the nerve.

Clinical aspects

This sensory entrapment mononeuropathy is caused by compression of the lateral femoral cutaneous nerve at the level of the Poupart ligament (inguinal ligament) or in the fascia lata just after entering the thigh beneath the lateral end of the inguinal ligament. Pain, paresthesias, and numbness over the anterolateral aspect of the thigh, accompanied by decreased objective sensation to touch, pain, and sometimes temperature. Standing, walking, or lying with the leg extended can exacerbate the symptoms. The nerve compression initially causes perineurial edema and eventually fibrosis with progression to focal and then diffuse demyelination and finally axonal loss and inflammation. Histopathological examination of the affected nerve segment (in nonfamilial) meralgia paresthetica reveals axonal loss and demyelination with scattered regeneration clusters (similar to findings in the median nerve in carpal tunnel syndrome).

Risk factors for nonfamilial meralgia paresthetica include mechanical pressure on the region where the nerve crosses the inguinal ligament secondary to obesity, intraabdominal disease, diabetic polyneuropathy, and/or external pressure by tight fitting clothing. Treatment options include pregabalin, antidepressants, surgical decompression with neurolysis, but often infiltration with local anesthetics and corticosteroids in combination with a lifestyle change (eg, weight loss, wearing different clothing) can significantly reduce the symptoms.

Precautions before anesthesia

Routine preoperative assessment.

Anesthetic considerations

Caution in transfer and positioning the patient. Avoid further compression over the area through which the nerve travels, that is, the lateral aspect of the inguinal ligament and lateral aspect of the thigh.

Pharmacological implications

None specific to this disorder.

References

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Bernhardt  M: Ueber isoliert im Gebiete des N. cutaneus femoris externus vorkommende Parasthesien. Neurol Cent 14:242–244, 1895.
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Malin  JP: Familial meralgia paresthetica with an autosomal dominant trait. J Neurol 221:133–136, 1979.  [PubMed: 92542] ...

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