Femoral Nerve Neuropathy by Synovial Hip Cyst as a Treatable Cause of Recurrent Falls: A Case Report

Synovial cysts originating from the hip joint are rarely symptomatic and are mostly found incidentally by imaging. When the cyst intrudes into the surrounding structures, local pain and swelling, arterial/venous compression, and rarely neurologic symptoms related to disturbance of femoral nerve function can be observed. We report a case of a 78-year-old man who was admitted because of recurrent falls at home over the last weeks. He had been noticing weakness in the right leg, and clinical and neurophysiologic examinations corroborated femoral nerve palsy. A pelvic computed tomography scan depicted a 5-cm-diameter cystic lesion within the right iliopsoas muscle in close contact with the femoral nerve. An ultrasound-guided needle aspiration with evacuation of 5 ml of clear fluid led to a nearly complete resolution of the palsy. We review the available literature on this subject and discuss further differential diagnoses of isolated femoral neuropathy and treatment options for hip joint cysts. Many conditions are associated with falls in older adults. Non-palpable cystic lesions of the hip joint must be considered when clinical examination reveals symptoms of femoral neuropathy. Treatments for symptomatic cysts range from rest, nonsteroidal anti-inflammatory drug administration, and needle aspiration to surgical excision.