"MERALGIA PARESTHETICA" or

LATERAL FEMORAL CUTANEOUS NERVE SYNDROME

 

KEYPOINTS:

• Characterized by pain, burning, and decreased sensation over the anterolateral aspect of the thigh in the distribution of the lateral femoral cutaneous nerve (LFCN).

• Since this is a purely sensory nerve, muscle weakness and reflex changes are absent.

• LFCN enters the thigh region deep to the lateral end of the inguinal ligament, near the anterior superior iliac spine; it supplies the skin on the anterior and lateral aspect of the thigh.

• Occurs secondary to compression or entrapment of the LFCN.

• Often occurs as people get older and gain weight when the abdomen bulges over the inguinal ligament and compresses the nerve.  In addition to obesity, can also be caused by pregnancy, compression from tight clothing or straps around the waist (e.g. tool belt, backpack), scar tissue from previous operations, or trauma, especially involving the hip.

• Rarely, pathologic intra-pelvic or intra-abdominal processes can cause compression of the LFCN.

 

EXAM:

• On exam, decreased sensation (hypoesthesia) or burning (dysesthesia) in distribution of LFCN is typical.  Most reproducible spot of decreased sensation is above and lateral to the knee.  No muscle weakness or reflex changes.

• Pressure over the nerve as it exits the pelvis just medial to or directly over the ASIS can produce tenderness or reproduce paresthesias along the nerve distribution.

• Abdominal and pelvic exams needed to exclude intra-abd process.

 

DIAGNOSTIC TESTS:

•  AP pelvis radiographs will r/o any bony abnormality, and AP/Lateral hip films may be needed if there is restriction of internal rotation of the hip and groin pain. 

• Consider CT of abd/pelvis to investigate a suspected intra-abd or intra-pelvic mass.

 

DIFFERENTIAL DIAGNOSIS:

• DM or other causes of peripheral neuropathy

• Hip arthritis

• Intra-abd tumor (? Wt loss, melena, etc)

• Lumbar disc herniation

• Trochanteric bursitis (tenderness over trochanter, stiffness when rising)

 

TREATMENT:

Removing the source of compression, such as a tight waistband or mild repetitive trauma to the nerve, can relieve the symptoms of burning.  In obese patients, significant weight loss often relieves symptoms.  Infiltration of the area around the nerve as it exits the pelvis near the anterosuperior iliac spine with a corticosteroid preparation may reduce symptoms.  Operative release of the nerve is most commonly needed in patients with persistent burning dysesthesia.

 

 

  

 

 

LGK 10/01