The causes of acquired 3rd nerve palsy
Among ocular misalignments from cranial nerve palsies, the third nerve palsies are the most worrisome, because a subset of these cases is caused by life-threatening aneurysms.
The annual incidence of acquired third nerve palsy is approximately 4 cases per 100,000.
The annual incidence in patients older than 60 was greater than patients younger than 60, predominantly due to a large increase in microvascular third nerve palsies in older adults.
The most common causes of acquired third nerve palsy are:
Presumed microvascular.
Trauma.
Compression from neoplasm.
Post-neurosurgery
Compression from aneurysm.
17 percent of patients with microvascular third nerve palsies have pupil involvement, while pupil involvement is seen in 64 percent with compressive third nerve palsies.
Overall, 43 percent with acquired third nerve palsies have pupil involvement at the time of presentation.
Pupil involvement was seen in:
>70 percent of traumatic third nerve palsies.
> 70 percent of post-neurosurgical third nerve palsies.
64 percent of compressive third nerve palsies
16 percent of microvascular third nerve palsies
Among compressive third nerve palsies, 33 percent of aneurysms have pupil involvement at presentation, and 81 percent of nonaneurysmal compressive third nerve palsies had pupil involvement.
Upsurge in the sixth decade of life of microvascular third nerve palsies.
Pupil involvement is more common in compressive lesions, it is seen in some cases of microvascular third nerve palsies, and pupil sparing is seen in some cases of compressive lesions, including aneurysm.