In cavernous sinus thrombosis, which cranial nerve is affected first?

In cavernous sinus thrombosis, the cranial nerve that is typically affected first is the abducens nerve, or cranial nerve VI. This is largely due to the anatomic location of the abducens nerve, which is closely associated with the wall of the cavernous sinus. When thrombosis occurs in this area, it can disrupt the nerve function more readily than others.

The abducens nerve is responsible for lateral eye movement, which is often noted early in the course of cavernous sinus thrombosis as patients may present with signs of lateral rectus muscle palsy, leading to diplopia or strabismus. Early impairment of this nerve due to its vulnerable position in the sinus can serve as a key clinical indicator in diagnosing the condition.

Other cranial nerves, such as cranial nerves III, IV, and V, may also be affected as the condition progresses, but the abducens nerve's positional vulnerability means it is usually implicated first in this pathological process. Understanding the order of nerve involvement is crucial because it aids in early recognition and treatment of the syndrome, which can be life-threatening if not addressed promptly.