Which cranial nerve is most susceptible to trauma?

Which cranial nerve is most susceptible to trauma?

• A. CN II
• B. CN III
• C. CN IV
• D. CN VI

Answer: (C)

Trochlear nerve vulnerability comes from its unusually long intracranial path and its exposed route around the brainstem. It travels a long distance from the dorsal side of the midbrain, threads around the brainstem through the ambient cistern, and then passes into the cavernous sinus and through the superior orbital fissure to reach the superior oblique muscle. That long, slender, and relatively tethered course makes it particularly prone to traction or shear injuries during head trauma, skull base fractures, or sudden shifts in intracranial pressures. When this nerve is injured, the patient develops vertical diplopia due to loss of the superior oblique, which normally depresses the eye when it is adducted and helps intort the eye. The diplopia worsens with looking down and in, and patients often tilt their head to the opposite side to compensate. In contrast, the other cranial nerves either have shorter intracranial courses or are less commonly affected by the kinds of trauma that typically injure the trochlear nerve.

Trochlear nerve vulnerability comes from its unusually long intracranial path and its exposed route around the brainstem. It travels a long distance from the dorsal side of the midbrain, threads around the brainstem through the ambient cistern, and then passes into the cavernous sinus and through the superior orbital fissure to reach the superior oblique muscle. That long, slender, and relatively tethered course makes it particularly prone to traction or shear injuries during head trauma, skull base fractures, or sudden shifts in intracranial pressures.

When this nerve is injured, the patient develops vertical diplopia due to loss of the superior oblique, which normally depresses the eye when it is adducted and helps intort the eye. The diplopia worsens with looking down and in, and patients often tilt their head to the opposite side to compensate. In contrast, the other cranial nerves either have shorter intracranial courses or are less commonly affected by the kinds of trauma that typically injure the trochlear nerve.