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Question

Difficulty: MediumPhysical Examination Findings

A 68-year-old man comes to the clinic due to a 3-week history of progressively worsening lower back pain. He has a history of prostate cancer treated with a radical prostatectomy 4 years ago. The pain is now constant, wakes him from sleep, and is poorly relieved by over-the-counter analgesics. He also reports new-onset weakness in his legs over the past 2 days. The physician is concerned about epidural spinal cord compression. Which of the following physical examination findings would specifically indicate spinal cord compression rather than cauda equina syndrome in this patient?

  1. Hyperreflexia and a positive Babinski sign bilaterallyAnswer
  2. B
    Decreased anal sphincter tone and perineal sensory loss
  3. C
    Asymmetric, flaccid weakness of the lower extremities
  4. D
    Abolished bilateral Achilles and patellar deep tendon reflexes
  5. E
    Pain radiating down the posterior thigh with passive straight leg raising

Answer

Hyperreflexia and a positive Babinski sign bilaterally
The presence of hyperreflexia and an upgoing plantar reflex (Babinski sign) indicates an upper motor neuron (UMN) lesion. In a patient with a history of prostate cancer presenting with red-flag back pain and weakness, these findings strongly point to epidural spinal cord compression. The spinal cord typically terminates at the L1-L2 vertebral level; compression above this level affects the spinal cord proper, resulting in UMN signs. This presentation must be distinguished clinically from cauda equina syndrome, which affects the peripheral nerve roots below the conus medullaris and presents with lower motor neuron signs.

Step-by-Step Solution

1
Identify the patient's risk factors and presenting symptoms.
The patient is a 68-year-old man with a history of prostate cancer who presents with worsening back pain and new-onset leg weakness, highly concerning for metastasis.
Recognizing red flag symptoms helps prioritize the differential diagnosis between neurologic emergencies like spinal cord compression and cauda equina syndrome.
2
Differentiate the anatomical locations of the suspected neurologic emergencies.
Epidural spinal cord compression affects the spinal cord proper (an upper motor neuron structure), whereas cauda equina syndrome affects the lumbosacral nerve roots below L1-L2 (lower motor neuron structures).
The anatomical level of the lesion dictates the specific physical examination findings.
3
Correlate the physical examination findings with the type of motor neuron lesion.
Upper motor neuron lesions present with spasticity, hyperreflexia, and a positive Babinski sign. Lower motor neuron lesions present with flaccid weakness, areflexia, and decreased tone.
This establishes the clinical criteria needed to answer the question.
4
Select the finding that specifically indicates spinal cord compression.
Hyperreflexia and an upgoing plantar reflex (Babinski sign) specifically point to an upper motor neuron process.
This matches the clinical picture of spinal cord compression above the level of the conus medullaris.

Key Concept

Physical examination findings differentiating upper motor neuron lesions (spinal cord compression) from lower motor neuron lesions (cauda equina syndrome).
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Topics

Physical Examination Findings

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