A 74-year-old man comes to the emergency department due to 2 weeks of progressive leg weakness and difficulty standing and walking. He has also had increasing urinary hesitancy and dribbling of urine. The patient has had low back pain for several months, but the pain has recently worsened and begun radiating to his legs. He was diagnosed with metastatic squamous cell lung cancer a year ago and received chemotherapy initially, but the patient stopped treatment due to side effects. He also has a history of hypertension and chronic obstructive pulmonary disease. Lower extremity examination shows normal bulk and tone but decreased strength of major muscle groups bilaterally. Knee reflexes are decreased on both sides. There are patchy areas of sensory loss in the bilateral lower extremities. Digital rectal examination shows loss of sensation in the perianal skin, decreased anal sphincter tone, and mildly enlarged prostate. A lesion at which of the following sites is most likely responsible for this patient's symptoms?

Question

A 74-year-old man comes to the emergency department due to 2 weeks of progressive leg weakness and difficulty standing and walking.  He has also had increasing urinary hesitancy and dribbling of urine.  The patient has had low back pain for several months, but the pain has recently worsened and begun radiating to his legs.  He was diagnosed with metastatic squamous cell lung cancer a year ago and received chemotherapy initially, but the patient stopped treatment due to side effects.  He also has a history of hypertension and chronic obstructive pulmonary disease.  Lower extremity examination shows normal bulk and tone but decreased strength of major muscle groups bilaterally.  Knee reflexes are decreased on both sides.  There are patchy areas of sensory loss in the bilateral lower extremities.  Digital rectal examination shows loss of sensation in the perianal skin, decreased anal sphincter tone, and mildly enlarged prostate.  A lesion at which of the following sites is most likely responsible for this patient's symptoms?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d599_dcd5_bc81_cfbefae01cb1_MD0003_00 This patient with metastatic squamous cell lung cancer has progressive back pain, radiculopathy, lower extremity motor/sensory/reflex deficits, bladder dysfunction, decreased rectal sphincter tone, and reduced perianal sensation, raising strong suspicion for cauda equina syndrome (CES), a medical emergency marked by compression of ≥2 spinal nerve roots in the lumbar cistern. Although most cases of CES are due to large, central lumbar disc herniation (at L4-S1), patients can develop CES from epidural tumors (eg, metastatic squamous cell lung cancer), epidural abscess, or inflammatory diseases in the region (eg, sarcoidosis). The cauda equina carries nerve roots from L2-L5, S1-S5, and the coccygeal nerve; therefore, patients with CES generally develop progressive lower back radicular pain (into one or both legs) plus ≥1 of the following: Motor deficits in the affected dermatomes; reflex responses in the knee or ankle are often absent Patchy sensory loss in the affected dermatomes; saddle anesthesia (impaired sensation in the buttocks, perineum, and/or perianal area) is particularly suggestive of CES Rectal sphincter, bladder (eg, hesitancy, dribbling), and/or sexual dysfunction due to damage to S3-S5 Patients with any of these symptoms require urgent MRI of the lumbosacral spine to evaluate for CES. Surgical decompression within 24-48 hours is generally required to prevent irreversible neurologic sequelae. (Choices B, C, D, E, and G) Lesions in the brain, spinal cord, and conus medullaris (tapered end of the spinal cord) generally cause upper motor neuron findings such as hypertonia, spasticity, hyperreflexia, and positive Babinski sign. In contrast, lesions at the level of the spinal roots usually cause lower motor neuron findings such as decreased/absent reflexes and decreased muscle tone. This patient's lower motor neuron signs (eg, loss of reflexes) in combination with rectal sphincter/bladder dysfunction and patchy sensory loss raise strong suspicion for CES. Although conus medullaris compression can be associated with perianal anesthesia and bowel/bladder dysfunction, it would cause upper (not lower) motor neuron signs in the lower extremities. (Choice F) Peripheral nerve damage is often caused by uncontrolled diabetes mellitus or alcohol abuse and generally presents with lower motor neuron signs and/or decreased sensation. Decreased rectal tone and bladder dysfunction would be atypical; these symptoms raise strong suspicion for CES. Educational objective: Cauda equina syndrome is a disorder marked by compression of ≥2 spinal nerve roots in the lumbar cistern. Most cases are caused by large, central lumbar disc herniation, but some are due to epidural tumor or abscess or inflammation in the region. Suspicion should be raised when a patient has severe, radicular lower back pain plus impaired motor/sensory/reflex activity in the lower extremities, bowel/bladder/sexual dysfunction, and/or saddle anesthesia. References: Conus medullaris and cauda equina syndrome as a result of traumatic injuries: management principles. (http://www.ncbi.nlm.nih.gov/pubmed/15202874) Cauda equina syndrome in patients undergoing manipulation of the lumbar spine. (http://www.ncbi.nlm.nih.gov/pubmed/1471004)

A 74-Year-Old Man Comes to the Emergency Department Due to 2