Purpose

 The purpose of this exhibit is to: 
-Review the detailed anatomy of the oculomotor nerve (CNII).
-Understand the specific functions of the oculomotor nerve.
-Highlight select clinical entities within the spectrum of partial and complete palsy.

Materials and Methods
Retrospective review of 3T MR and CT examinations performed for oculomotor nerve palsy or paresis over the last 5 years. A variety of oculomotor nerve palsy cases are presented which clearly demonstrate the pertinent imaging findings on high-resolution cross-sectional imaging. Relevant anatomy is reviewed. Additionally, a literature review on oculomotor nerve palsy was completed.

Results
Review oculomotor nerve anatomy by dividing the nerve into 7 distinct segments: supranuclear, nuclear, fascicular, cisternal, cavernous sinus, superior orbital fissure, and orbital lesions using a case-based approach. This presentation highlights neuroanatomy pertinent to the specific level of oculomotor pathology, emphasizing how the clinical presentation can drive the differential diagnosis.


Conclusions
Etiology and clinical presentation of CN III palsy varies depending on the level of the lesion or injury. An accurate diagnosis is predicated on a detailed understanding of the anatomy and CN III pathologic spectrum. Classic CN III injury can be classified partial (paresis) or complete palsy with or without pupillary involvement. Pupillary involved CN III palsy is more often caused by compression, which can be related to aneurysm and requires vascular imaging. Cavernous sinus or superior orbital fissure lesions typically result in multiple cranial nerve palsies.  Radiologists must be familiar with the spectrum of oculomotor dysfunction to avoid lesion mislocalization and/or premature exclusion of CN III pathology.

Not Just Down and Out: Oculomotor Nerve Pathologic Spectrum

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