Hanna, Barbara

BACKGROUND Lipomatosis of the nerve (LN) is a rare peripheral nerve pathology characterized by abundant proliferation of fat within the epineurium giving it pathognomonic features on MRI. Any nerve may be affected, but major nerves such as the median and sciatic nerves are most reported. One of the clinical hallmarks of LN is associated bony and soft tissue overgrowth occurring distal to the nerve lesion. While macrodactyly and limb length overgrowth are well known in LN, this study aims to look at nerve territory bony overgrowth affecting the knee. OBSERVATIONS An initial search revealed 59 cases of LN in the Mayo Clinic system. Of 19 patients with LN of the lower limbs, 12 cases involved nerves in the pelvis, buttock, or thigh. Three cases fulfilled the criteria (LN of lower extremity with available MR images and knee radiographs) that affected the femoral, sciatic, and combined femoral/sciatic nerves. Knee radiographs revealed bony overgrowth in the respective nerve territories in each case: anterior, posterior, and both anterior and posterior portions of the knee. LESSONS These illustrative cases of LN with overgrowth of the knee demonstrate that bone overgrowth follows the territory of the associated nerve in LN, which supports the previously published evidence on LN-associated nerve territory overgrowth. https://thejns.org/doi/10.3171/CASE25132

Background: The median nerve anatomy and its clinical presentation are crucial for surgeons to consider avoiding iatrogenic injury and performing effective surgical interventions. Case Description: An atypical presentation of median nerve anatomy proximal to the carpal tunnel was found during cadaveric dissection. The median nerve was located deep to a uniquely double-headed flexor carpi radialis and curved medially around the tendons of the forearm to enter the carpal tunnel superficially. Conclusion: The atypical presentation of median nerve anatomy can assist surgeons in adverse event reduction during surgeries such as carpal tunnel and pronator teres syndrome releases.