Ocularmotor Nerve Palsy (CN III)

Exam Cram

• Ocularmotor nerve (CN III) 

• Presentation: down and out eye, dilated pupil and ptosis

• Diagnosis: clinical

•  Management

  • CT Angio if pupil involved +- surgery

  • Pupil spared ix and treat medical causes (BP, diabetes, vasculitis)

Outline

Background

• Oculomotor nerve is the 3rd cranial nerve

• Oculomotor nerve supplies four ocular eye muscles: medial, superior and inferior rectus & inferior oblique

•  Oculomotor nerve has sympathetic fibres to dilate the pupil, on the outside of its fibre

Assessment

History

• Diploplia (double vision)

• Trauma

• Raised icp: headaches

Examination

• Affected eye: down and out at rest, minimal movements

• Ptosis (dropping eye lid)

• Dilated pupil (mihydrosis)

Investigations

• CT Angio: ?posterior communicating artery aneurysm ? SoL/ malignancy

• Blood pressure- Hypertension

• Blood sugar- Diabetes Mellitus 

• CRP, WCC, ESR- Vasculitis 

Diagnosis

Diagnostic criteria: clinical

Classification (underlying cause):

• Surgical (extrinsic) causes- pupil dilated

• Medical (intrinsic) causes- pupil spared

Management

Surgery is the preferable modality

• T1, N1, M0- surgical resection

• T3-4, N1-3, M0- neoadjuvant chemo/radiotherapy with oesophagectomy

• T4, N3, M1- consider End of Life Care 

Resources and References

Links

• Physiology: GI system

• Pathology: Cancer

• Specialty: General Surgery, Gastroenterology

Written in 2025