A 56-year-old man is evaluated in the clinic due to worsening lower extremity pain and weakness. The patient has had hematuria and intermittent burning on urination for the past year. He has no history of pelvic trauma or surgery. The patient has smoked a pack of cigarettes daily for the past 35 years. His urine culture is negative for bacterial growth. Urine cytology and cystoscopy confirm the diagnosis of transitional cell carcinoma. Abdominal CT shows an advanced bladder tumor compressing a nerve that passes through the obturator canal. Which of the following actions would most likely be impaired in this patient?

Question

A 56-year-old man is evaluated in the clinic due to worsening lower extremity pain and weakness.  The patient has had hematuria and intermittent burning on urination for the past year.  He has no history of pelvic trauma or surgery.  The patient has smoked a pack of cigarettes daily for the past 35 years.  His urine culture is negative for bacterial growth.  Urine cytology and cystoscopy confirm the diagnosis of transitional cell carcinoma.  Abdominal CT shows an advanced bladder tumor compressing a nerve that passes through the obturator canal.  Which of the following actions would most likely be impaired in this patient?

Quizplus · Accepted Answer

11ec160b_3598_2f07_9249_1d38116ee1d5_MD0001_00 The obturator nerve arises from the lumbar plexus and carries fibers from the L2-L4 spinal segments. It descends posteromedial to the iliopsoas muscle and courses along the lateral aspect of the lesser pelvis before descending through the obturator canal. The obturator nerve is the only major nerve that exits the pelvis through this canal. Once the nerve has entered the thigh, it supplies the obturator externus muscle and divides into anterior and posterior branches that supply the rest of the thigh adductor muscles (eg, adductor longus, brevis, magnus). The anterior division of the nerve gives off a terminal cutaneous branch that provides sensation over the distal medial thigh. Obturator nerve injury is most commonly caused by compression due to pelvic trauma, surgery, or tumors (eg, bladder cancer). Patients typically present with weakness on thigh adduction and sensory loss in the distal medial thigh. (Choice A) Abduction of the thigh is primarily accomplished by the gluteus medius, gluteus minimus, and tensor fascia lata, which are supplied by the superior gluteal nerve. This nerve exits the pelvis through the greater sciatic foramen above the piriformis. (Choice C) Extension of the leg is mainly accomplished by the quadriceps femoris muscle group. These muscles are innervated by the femoral nerve, which gains access to the thigh deep to the midpoint of the inguinal ligament. (Choice D) Extension of the thigh is mostly accomplished by the gluteus maximus muscle, which is supplied by the inferior gluteal nerve. This nerve exits the pelvis through the greater sciatic foramen below the piriformis. (Choice E) Flexion of the thigh is primarily accomplished by the psoas, iliacus, and sartorius muscles. The psoas is directly innervated by the lumbar plexus, and the iliacus is innervated by the femoral nerve. Educational objective: The obturator nerve is the only major nerve that exits the pelvis through the obturator foramen. Nerve injury typically results from compression (eg, due to pelvic trauma, surgery, or tumor) and presents with weakness on thigh adduction and sensory loss over the distal medial thigh. __________ References: Obturator neuropathy. (http://www.ncbi.nlm.nih.gov/pubmed/19468309) Obturator mononeuropathy caused by pelvic cancer: six cases. (http://www.ncbi.nlm.nih.gov/pubmed/8394520)

A 56-Year-Old Man Is Evaluated in the Clinic Due to Worsening