An intradural mass lesion at the tip of a drug infusion catheter is least likely to present as

An intradural mass lesion at the tip of a drug infusion catheter is least likely to present as

• A. Piloerection, rhinorrhea, sweating, and more pain
• B. Development of numbness in T8 dermatomal pattern
• C. Hypopnea
• D. Perianal numbness

Answer: (C)

The main idea is that a mass intradurally at the tip of an intrathecal catheter produces signs that are segmental to the level of the cord involved, plus possible autonomic symptoms from irritation of nearby pathways. Such a lesion commonly causes sensory changes in the dermatomes at or below the level of compression (for example, a T8 distribution) and can produce perianal numbness if lower sacral roots are affected. Autonomic signs like piloerection, rhinorrhea, and sweating can occur with spinal irritation or compression due to disrupted sympathetic pathways. Hypopnea, on the other hand, implies reduced respiratory drive from involvement of higher spinal levels or brainstem respiratory centers (or systemic opioid toxicity). A localized intradural mass at the tip of an intrathecal catheter—particularly in the lower spine—would not typically impair the brainstem respiratory centers or phrenic nerve function. Therefore hypopnea is the presentation least likely to arise from a localized intradural mass at the catheter tip, whereas the other signs align with segmental spinal compression and autonomic disturbance at that level.

The main idea is that a mass intradurally at the tip of an intrathecal catheter produces signs that are segmental to the level of the cord involved, plus possible autonomic symptoms from irritation of nearby pathways. Such a lesion commonly causes sensory changes in the dermatomes at or below the level of compression (for example, a T8 distribution) and can produce perianal numbness if lower sacral roots are affected. Autonomic signs like piloerection, rhinorrhea, and sweating can occur with spinal irritation or compression due to disrupted sympathetic pathways.

Hypopnea, on the other hand, implies reduced respiratory drive from involvement of higher spinal levels or brainstem respiratory centers (or systemic opioid toxicity). A localized intradural mass at the tip of an intrathecal catheter—particularly in the lower spine—would not typically impair the brainstem respiratory centers or phrenic nerve function. Therefore hypopnea is the presentation least likely to arise from a localized intradural mass at the catheter tip, whereas the other signs align with segmental spinal compression and autonomic disturbance at that level.