Spinal cord compression due to epidural metastasis

A 64-year-old woman is evaluated in the emergency department for a 4-day history of progressive bilateral leg weakness and numbness and a 1-day history of urinary incontinence. She has also had increasingly severe midback pain for the past 2 months. She has a history of breast cancer diagnosed 2 years ago and treated with surgery and local radiation therapy. Her only current medication is tamoxifen.

Physical examination shows normal mental status and cranial nerves. Strength in the arms is normal. The legs are diffusely weak, 3/5 proximally and 4/5 distally. Sensory examination shows diminished pinprick sensation from the nipples downward; vibratory sense is severely diminished in the feet. Reflexes are 2+ in the biceps and triceps and 3+ in the knees and ankles. An extensor plantar response is present bilaterally. Anal sphincter tone is diminished.

Which of the following is the most appropriate diagnostic study at this time?
A CT scan of the lumbar spine
B Electromyography and nerve conduction studies
C MRI of the brain
D MRI of the entire spine
E Plain radiographs of the entire spine


ANSWER

This patient has bilateral weakness and upper motor neuron signs in the legs, sensory loss below the T4 level, and sphincter dysfunction; there are no signs or symptoms of brain or brainstem dysfunction. These findings are consistent with a spinal cord process. Given her history of breast cancer, metastatic spinal cord compression from an epidural metastasis is most likely and represents a neurologic emergency that must be excluded by urgent imaging. Although the distribution of pain and the sensory level suggest that the lesion is at the thoracic level, MRI of her entire spine is most appropriate because sensory levels can be unreliable for localizing the site of an epidural tumor. In addition, patients with a metastatic epidural tumor can have multiple sites of disease in the spine. MRI gives excellent images of both the spinal cord and the vertebrae, whereas CT does not adequately show the substance of the spinal cord and epidural region, making MRI the modality of choice in this patient.

CT scan of the lumbar spine is not an appropriate imaging choice in this patient. Because the spinal cord ends at around the L1 vertebral body, the spinal cord would not be visualized if imaging of the lumbar spine alone is performed. Plain radiographs of the spine can visualize some bony metastases and fractures but are not sensitive for the site of cord compression and do not image the spinal cord. Electromyography and nerve conduction studies are helpful in diagnosing peripheral nerve and muscle diseases but have no role in the evaluation of spinal cord disorders. MRI of the brain may be needed to assess for asymptomatic brain metastases but is not as urgent as spine imaging.


Key Point
Spinal cord compression due to epidural metastasis is a neurologic emergency for which urgent MRI of the entire spine is appropriate.

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