Meralgia Paresthetica
The most likely diagnosis is meralgia paresthetica, an entrapment neuropathy of the lateral femoral cutaneous nerve (LFCN) at the inguinal ligament, confirmed by the pathognomonic positive Tinel sign (reproduction of symptoms with tapping over the lateral inguinal ligament) in a patient with classic risk factors (obesity with BMI 37, diabetes, sedentary lifestyle). 1, 2
Clinical Reasoning
The clinical presentation is diagnostic for meralgia paresthetica based on several key features:
Anterolateral thigh distribution: The burning pain and numbness localized to the anterolateral left thigh matches the sensory distribution of the LFCN, which is pathognomonic for this condition 3, 4, 2
Positive Tinel sign: Reproduction of symptoms with tapping over the lateral inguinal ligament is the classic diagnostic finding that confirms LFCN entrapment at this anatomic location 3, 5
Risk factor profile: Obesity (BMI 37) and diabetes are the two most significant risk factors that increase the incidence of meralgia paresthetica, as the LFCN is compressed as it tunnels through the inguinal ligament 2, 6
Why Not Diabetic Peripheral Neuropathy?
This presentation is distinctly different from typical diabetic peripheral neuropathy (DPN):
Distribution pattern: DPN presents as distal symmetric polyneuropathy affecting both feet in a stocking distribution with reduced ankle reflexes, not unilateral proximal thigh symptoms 1, 7
Reflexes: DPN causes reduced or absent ankle reflexes, whereas meralgia paresthetica presents with normal reflexes since it is a pure sensory mononeuropathy 7, 5
Temporal pattern: DPN develops gradually over months to years with length-dependent progression starting distally, not acutely in a proximal unilateral distribution 7
Diagnostic Confirmation
Clinical diagnosis: The diagnosis is relatively simple due to unique clinical features and can be confirmed by relief of symptoms after injection of local anesthetic at the entrapment site 3, 5
Electrodiagnostic studies: Can confirm LFCN involvement if diagnosis is uncertain, though typically not necessary with classic presentation 4, 2
Imaging considerations: In atypical cases or treatment-resistant symptoms, consider abdominopelvic imaging to exclude mass lesions (ovarian cysts, tumors) that can compress the nerve proximally 4
Management Algorithm
Conservative management (first-line for all patients):
Remove compressive factors: loose clothing, weight loss (critical given BMI 37), avoid prolonged standing 3, 6, 5
Neuropathic pain medications if burning pain persists: pregabalin, gabapentin, or duloxetine 1
Interventional management (if conservative fails after 6-8 weeks):
- Local anesthetic and corticosteroid injection at the entrapment site provides both diagnostic confirmation and therapeutic benefit 3, 6, 5
Surgical management (last resort for intractable symptoms):
- Neurolysis with decompression and transposition versus neurectomy (nerve transection) - both options remain controversial regarding superiority 6, 5
Critical Pitfall to Avoid
Do not dismiss this as simply diabetic neuropathy and optimize glucose control alone - while the American Diabetes Association recommends optimizing diabetes management to prevent neuropathic complications, this won't resolve the mechanical compression causing meralgia paresthetica 1. The patient requires specific treatment directed at relieving LFCN entrapment, with weight loss being the most important long-term intervention given the BMI of 37 3, 2, 5.