History

Fact Explanation
Typically unilateral pain, paresthesia and numbness of upper lateral thigh area. This is a mononeuropathy of the lateral femoral cutaneous nerve (LFCN), resulting in dysesthesia or anesthesia in the distribution of the nerve (the anterolateral thigh area) [1]. This occurs frequently due to compression of the LFCN as it crosses the anterior superior iliac spine under the inguinal ligament to enter the thigh [2].
History of diabetes mellitus. Chronic hyperglycemia increases susceptibility to nerve injury [3].
Symptoms aggravated by walking and relieved by sitting. The iliopsoas muscle and the tensor fascia lata are stretched during walking. This may result in compression of the LFCN in the inguinal canal [4].
History of wearing tight garments, braces or direct trauma. These have the potential to cause compression and stretching injuries to the LFCN, when it exits the pelvis [1].
History of abdominal or pelvic surgeries. The LFCN can be injured when making incisions during these surgeries [1].
References
  1. IVINS GK. Meralgia Paresthetica, The Elusive Diagnosis: Clinical Experience With 14 Adult Patients Ann Surg [online] 2000 Aug, 232(2):281-286 [viewed 18 November 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1421141
  2. SCHESTATSKY PEDRO, LLADó-CARBó ESTELA, CASANOVA-MOLLA JORDI, ÁLVAREZ-BLANCO SILVIO, VALLS-SOLé JOSEP. Small fibre function in patients with meralgia paresthetica. PAIN [online] 2008 October, 139(2):342-348 [viewed 19 November 2014] Available from: doi:10.1016/j.pain.2008.05.001
  3. PARISI T. J., MANDREKAR J., DYCK P. J. B., KLEIN C. J.. Meralgia paresthetica: Relation to obesity, advanced age, and diabetes mellitus. Neurology [online] December, 77(16):1538-1542 [viewed 19 November 2014] Available from: doi:10.1212/WNL.0b013e318233b356
  4. KHO KUAN H., BLIJHAM PAUL J., ZWARTS MACHIEL J.. Meralgia paresthetica after strenuous exercise. Muscle Nerve [online] December, 31(6):761-763 [viewed 19 November 2014] Available from: doi:10.1002/mus.20271

Examination

Fact Explanation
Numbness of upper lateral thigh area. This is a mononeuropathy of the LFCN, resulting in dysesthesia or anesthesia in the distribution of the the nerve (the anterolateral thigh area) [1]. This occurs frequently due to compression of the LFCN as it crosses the anterior superior iliac spine under the inguinal ligament to enter the thigh [2].
Obesity. Obesity is associated with mechanical compression of the nerve [3].
Pain on palpation of the lateral part of the inguinal ligament. This is usually the point where the nerve crosses the inguinal ligament [4].
Hair loss in the area of skin supplied by the LFCN. It occurs due to constant rubbing of the area by the patient [4].
Normal motor strength in the involved lower limb. The LFCN is primarily a sensory nerve [1].
References
  1. IVINS GK. Meralgia Paresthetica, The Elusive Diagnosis: Clinical Experience With 14 Adult Patients Ann Surg [online] 2000 Aug, 232(2):281-286 [viewed 18 November 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1421141
  2. SCHESTATSKY PEDRO, LLADó-CARBó ESTELA, CASANOVA-MOLLA JORDI, ÁLVAREZ-BLANCO SILVIO, VALLS-SOLé JOSEP. Small fibre function in patients with meralgia paresthetica. PAIN [online] 2008 October, 139(2):342-348 [viewed 19 November 2014] Available from: doi:10.1016/j.pain.2008.05.001
  3. PARISI T. J., MANDREKAR J., DYCK P. J. B., KLEIN C. J.. Meralgia paresthetica: Relation to obesity, advanced age, and diabetes mellitus. Neurology [online] December, 77(16):1538-1542 [viewed 19 November 2014] Available from: doi:10.1212/WNL.0b013e318233b356
  4. PATIJN JACOB, MEKHAIL NAGY, HAYEK SALIM, LATASTER ARNO, VAN KLEEF MAARTEN, VAN ZUNDERT JAN. 20. Meralgia Paresthetica. [online] December, 11(3):302-308 [viewed 19 November 2014] Available from: doi:10.1111/j.1533-2500.2011.00458.x

Differential Diagnoses

Fact Explanation
Femoral mononeuropathy. It also presents with sensory changes in the thigh, but motor changes such as quadriceps weakness and decreased or absent patellar reflex may also be present [1].
References
  1. GENC HAKAN, BALABAN OZLEM, KARAGOZ AYNUR, ERDEM HATICE RANA. Femoral Neuropathy in a Patient with Rheumatoid Arthritis. Yonsei Med J [online] 2007 December [viewed 19 November 2014] Available from: doi:10.3349/ymj.2007.48.5.891

Investigations - for Diagnosis

Fact Explanation
Diagnosis is primarily clinical. A consistent and reliable diagnosis can be made by accurately mapping the area of dysesthesia, which would correspond to the area supplied by the LFCN [1].
Nerve conduction testing of the LFCN. This can demonstrate meralgia paraesthetica, as well as provide information and locate the lesion in the LFCN [2].
Blockade of LFCN with 8ml of local anesthetic by locating the nerve with a nerve stimulator. A positive diagnostic blockade can confirm the diagnosis [2].
References
  1. IVINS GK. Meralgia Paresthetica, The Elusive Diagnosis: Clinical Experience With 14 Adult Patients Ann Surg [online] 2000 Aug, 232(2):281-286 [viewed 19 November 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1421141
  2. PATIJN JACOB, MEKHAIL NAGY, HAYEK SALIM, LATASTER ARNO, VAN KLEEF MAARTEN, VAN ZUNDERT JAN. 20. Meralgia Paresthetica. [online] December, 11(3):302-308 [viewed 19 November 2014] Available from: doi:10.1111/j.1533-2500.2011.00458.x

Investigations - Screening/Staging

Fact Explanation
Magnetic resonance imaging, Computed tomograghy. Imaging may be used to assess for intra-abdominal disease that increases intrapelvic pressure resulting in meralgia paraesthetica, as well as assess for lesions that may cause upper lumbar nerve compression which may mimic the condition [1].
Fasting blood glucose levels. Chronic hyperglycemia increases susceptibility to nerve injury [2].
References
  1. HAIM AMIR, PRITSCH TAMIR, BEN-GALIM PELEG, DEKEL SAMUEL. Meralgia paresthetica: A retrospective analysis of 79 patients evaluated and treated according to a standard algorithm. Acta Orthop [online] 2006 January, 77(3):482-486 [viewed 19 November 2014] Available from: doi:10.1080/17453670610046433
  2. PARISI T. J., MANDREKAR J., DYCK P. J. B., KLEIN C. J.. Meralgia paresthetica: Relation to obesity, advanced age, and diabetes mellitus. Neurology [online] December, 77(16):1538-1542 [viewed 19 November 2014] Available from: doi:10.1212/WNL.0b013e318233b356

Management - General Measures

Fact Explanation
Weight loss. Obesity is associated with mechanical compression of the nerve [1].
Wearing loose clothing. Tight clothes have the potential to cause compression injuries to the LFCN, when it exits the pelvis [2].
References
  1. PARISI T. J., MANDREKAR J., DYCK P. J. B., KLEIN C. J.. Meralgia paresthetica: Relation to obesity, advanced age, and diabetes mellitus. Neurology [online] December, 77(16):1538-1542 [viewed 19 November 2014] Available from: doi:10.1212/WNL.0b013e318233b356
  2. IVINS GK. Meralgia Paresthetica, The Elusive Diagnosis: Clinical Experience With 14 Adult Patients Ann Surg [online] 2000 Aug, 232(2):281-286 [viewed 18 November 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1421141

Management - Specific Treatments

Fact Explanation
Local infiltration of the LFCN with bupivacaine 0.25%. This local anesthetic provides perineural analgesia and thereby relief of symptoms [1].
Carbamazepine. (200-800mg daily in divided doses) Pain occurs due to ectopic discharges from damaged nerves as a result of membrane remodelling. This leads to an excess of voltage sensitive sodium channels in the area of nerve damage. carbamazepine blocks use-dependent sodium channels in preference to inactive channels, thereby causing pain relief [2].
Gabapentin. (300mg 3 times daily) It binds to voltage dependent calcium channels and inhibits the release of excitatory neurotransmitters while reducing glutamate availability at NMDA and non-NMDA receptors, thereby causing pain relief [2].
Surgical decompression of the LFCN. (By dividing the posterior slip of the inguinal ligament ) The LFCN may pass through the split lateral attachment of the inguinal ligament and curve medially and inferiorly around the anterior superior iliac spine, resulting in compression and repetitive trauma in this fibroosseous tunnel [3]. Surgery is reserved for those who do not respond to conservative therapy.
References
  1. RICHMAN JEFFREY M., LIU SPENCER S., COURPAS GENEVIEVE, WONG ROBERT, ROWLINGSON ANDREW J., MCGREADY JOHN, COHEN SETH R., WU CHRISTOPHER L.. Does Continuous Peripheral Nerve Block Provide Superior Pain Control to Opioids? A Meta-Analysis. Anesthesia & Analgesia [online] 2006 January, 102(1):248-257 [viewed 19 November 2014] Available from: doi:10.1213/01.ANE.0000181289.09675.7D
  2. BENNETT MICHAEL I, SIMPSON KAREN H. Gabapentin in the treatment of neuropathic pain. palliat med [online] 2004 January, 18(1):5-11 [viewed 19 November 2014] Available from: doi:10.1191/0269216304pm845ra
  3. IVINS GK. Meralgia Paresthetica, The Elusive Diagnosis: Clinical Experience With 14 Adult Patients Ann Surg [online] 2000 Aug, 232(2):281-286 [viewed 18 November 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1421141