Background and Aims The medial femoral cutaneous nerve (MFCN) is known to innervate the anteromedial knee area.^1,2 A selective block of the anterior branch from the MFCN (MFCN-A) but not the posterior branch (MFCN-P) has been described.^3,4 We present an ultrasound-guided technique for blockade of the MFCN-P. Post-hoc analysis of data from a randomized, controlled trial showed that the MFCN-A or MFCN-P may innervate the distal part of the medial lower leg and even the medial malleolus (MM) which has never previously been described.⁴ We present a case of cutaneous neuropathy in the “classical saphenous nerve territory” on the medial side of the lower leg and MM, where a selective MFCN-P block was used for diagnosis and treatment of the neuropathic pain.⁵

Methods A woman presented with severe chronic neuropathic pain on the medial side of the lower leg and MM. The worst pain was localized to the MM. Diagnostic nerve blocks were performed in the following order: 1) SN; 2) MFCN-A; 3) MFCN-P (figure 1 and 2).

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Abstract B1 Figure 1

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Abstract B1 Figure 2

Results The SN, MFCN-A and MFCN-P all innervated part of the skin in the neuropathic area. SN block alone marginally reduced NRS, whereas additional MFCN-A block did not further reduce NRS. MFCN-P block anesthetized the area around the MM and significantly reduced the pain. Perineural botox was injected around the SN and MFCN-P. At 2-weeks follow-up NRS was significantly reduced (table 1) and patient satisfaction high.

Conclusions We present a novel selective MFCN-P block, which may be important in the diagnosis and treatment of chronic neuropathic pain.