Thread by @ClementsCharl96

1) A thread looking at the rather weird and wonderful, Meralgia Paraesthetica (MN)

2) Mononeuropathy of the lateral femoral cutaneous nerve which arises from the dorsal horn of L1-3. It is predominantly sensory but also has vasomotor (temp changes), sudomotor (sweating) & pilomotor (hair movement) functions.

3) It passes lateral to the psoas, beneath the iliac fascia & inguinal ligament where it enters a fibro-osseous tunnel & splits into anterior & posterior divisions to provide sensation to the anterolateral thigh. Compression is often at the inguinal ligament insertion @ the ASIS.

4) Epidemiology: Equal prevalence amongst genders and is more apparent in the 3rd - 5th decades. Thought to affect 4.3 per 100k in general population versus 247 per 100k in diabetics (Cheatham et al., 2013).

5) Risk Factors; hypothyroidism (+ swelling & exert pressure on nerve), diabetes (+ inflammation & ischaemia) obesity, pregnancy, tight clothing, space occupying lesions (lipomas, schwannoma & tumours) & surgical procedures (THR’s / spinal).

6) Features: Dysesthesia & paraesthesia along the sensory distribution of LFCN (anterolateral thigh). Sx are purely sensory due to no motor innervation. Sx are often aggravated in standing due to hip extension compressing the nerve against the inguinal ligament.

7) Differentials: MP is an elusive condition, important to rule out other pathologies; a) LSS, b) Lx radiculopathy or radicular pain & c) somatic hip pain. Sx which will not occur with MP are; i) abnormal reflexes, ii) muscle weakness or iii) sensory deficit in lower limb

8) One objective test is The Compression Test: Pt is side lying w symptomatic side up. Apply compressive load across the innominate for 45s. Has a SP of 93% & SN 95% (*has only been assessed once on 20 pt’s though!!!)

9) Another test would possibly involve a Neurodynamic: Side lying, flex the knee and adduct the hip to stretch the nerve (similar to a prone knee bend which stresses the femoral nerve).

10) Natural History: It is thought approx. 85% of cases improve. Iatrogenic cases can improve within 3/12 and most pregnancy-related MP’s will resolve post-delivery (Coffey & Gupta, 2021).

11) Treatment; Appears to be little high-quality evidence. Reducing Aggs (time standing & tight clothing), BMI advice if appropriate. ? NSAID’s may offer some relief. If nil improvement then query an injection with anaesthetic and corticosteroid

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