What is Meralgia Paresthetica

What is involved?

Lateral Cutaneaous Nerve of Thigh

Location

Lateral Cutaneaous Nerve of Thigh in the upper and outer thigh

Common symptoms

• Pain, burning in the thigh
• Poor tolerance to touch, clothes, cover or anything that rubs against thigh
• In mothers (or fathers) pain/burning with children sitting on lap
• No thigh or leg weakness or atrophy
• Usually unilateral
• Symptoms always present, no night/day preference

Onset

• Usually Gradual over days, weeks
• May be Sudden

Risk factors

• No gender preference
• Diabetes or family history of Diabetes, Alcoholism or other occupational or nutritional causes of Neuropathies, HIV infection
• Overweight
• Tight undergarments or clothing in the inguinal area

Exam

• Decreased sensation over upper and lateral area of thigh
• Sometimes decreased sensation all the way to the patella
• Difficult to examine because of pain/burning induced by touching or rubbing
• Normal strength, no atrophy in thigh muscles
• Preserved Knee Jerk (if absent or unilaterally decreased suspect L3 root lesion)

Localization

Pure sensory branch involvement at the upper and lateral end of the inguinal ligament

EMG

• Study Lateral Cutaneous Nerve of Thigh, usually small amplitude (<10 μV)
• Study both sides to compare amplitudes
• Response may be absent or significantly (<50%) smaller than healthy side
• Nerve Conductions may be difficult to perform in overweight subjects
• Rule out L3 root lesion by studying other Femoral and non-Femoral innervated muscles to include:
  • Vastus Lateralis (derived from Femoral Nerve below Inguinal ligament)
  • Ilio-Psoas (from Femoral Nerve above Inguinal ligament)
  • Thigh Adductors (from Obturator Nerve)
• In Meralgia Paresthetica, the needle exam of the Thigh muscles will be normal
• In L3 root lesions, Vastus Lateralis, Ilio-Psoas, Thigh Adductors and/or paraspinals could be involved
• In Femoral Nerve lesions, Vastus Lateralis and Ilio-Psoas, but not Thigh Adductors, are involved
• In Obturator Neuropathy, only Thigh Adductors are involved

Recommendations

• Symptomatic treatment
• Stop/decrease cause, tight undergarments, clothing
• Lose weight
• Anti epileptics, tricyclics have been tried with various degrees of success
• Nerve blocks/Injections

What else could it be?

• Could be an L3 root lesion if associated muscle weakness (Vastus Lateralis, Ilio-Psoas and/or Thigh adductors) or absent or unilaterally decreased Knee jerk
• Few other conditions can cause the same symptoms