Professional and Linguistic Assessments Board (PLAB) Practice Exam

Which sensation is generally preserved in patients with syringomyelia despite loss of temperature sensation?

1. Light touch

2. Pain

3. Proprioception

4. Vibration

The correct answer is: Light touch

In patients with syringomyelia, the sensation of light touch is typically preserved even when there is a loss of temperature sensation. This condition is characterized by the formation of a cyst (syrinx) within the spinal cord, which can disrupt the normal pathways that carry temperature and pain sensations. The loss of these sensations occurs because the crossing fibers responsible for transmitting pain and temperature are affected by the expanding cyst. However, light touch sensation is carried by the dorsal columns of the spinal cord, which are usually spared in the early stages of the disease. These columns transmit proprioceptive and vibratory sensations as well, but light touch specifically remains intact longer than pain and temperature because the pathways for these modalities are distinct within the spinal cord. This preservation is important for diagnosis and understanding the progression of the disease. While proprioception and vibration sensation can also be preserved, the most commonly noted preservation in clinical evaluations directly relates to light touch, making it the more appropriate answer in this context.