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

– Can be very annoying
– 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