Palsies of which cranial nerve result in esotropia due to weakness of the lateral rectus muscle?

The correct response identifies that palsies of the sixth cranial nerve, also known as the abducens nerve, result in esotropia due to weakness of the lateral rectus muscle. The lateral rectus muscle is responsible for the abduction movement of the eye, which pulls the eye outward. When the sixth cranial nerve is affected, the lateral rectus muscle becomes weak or paralyzed, leading to an inability to move the affected eye laterally. This results in the eye crossing inward towards the nose, a condition known as esotropia.

Esotropia can also be observed in other cranial nerve palsies, but specifically for the abducens nerve, the defining characteristic is the loss of lateral movement. Since the lateral rectus muscle is solely innervated by cranial nerve VI, its paralysis directly leads to the clinical sign of esotropia. Understanding the specific muscles innervated by each cranial nerve is crucial for diagnosing and understanding the implications of nerve injuries in clinical practice.