Cranial Nerve IV Palsy

Cranial Nerve IV Palsy: Pathogenesis and clinical findings
(e.g. Möbius Syndrome)
Dysgenesis (defective development) of CN IV
Microvascular Disease (e.g. Stroke)
Damage or occlusion (complete or partial blockage) to the blood vessels supplying CN IV
Temporary or permanent damage to the nerve fibers
Metastasis (e.g. Leptomeningeal)
Compression of the nerve fibers along the nerve tract
Primary (e.g. Schwannoma)
Tumor develops new blood vessels that redirect blood flow to the malignancy, away from the nerve
Ischemia of CN IV
Infection (a rare cause) (e.g. Ehrlichia chaffeensis, Tuberculosis meningitis)
Infectious process in the subarachnoid space
Damage to axons of CN IV
Cranial Nerve (CN) IV Palsy
Superior oblique musculature weakness due to CN IV dysfunction
Lesion to the fascicle of CN IV (extending from midbrain to cavernous sinus)
Impaired ability to conduct motor commands from nucleus to superior oblique muscle in the eye
Weak superior oblique innervation
Difficult abduction and intorsion of the eye
Contralateral superior
oblique weakness
Lesion to the nucleus of CN IV (located in the midbrain)
Disturbed signal production occurring prior to demarcation of fibers to contralateral side
The pathophysiology above can cause damage to structures surrounding CN IV in the midbrain
Impacting ipsilateral sympathetic chain descending from the
hypothalamus prior to reaching the superior cervical ganglion
Shahab Marzoughi Reviewers:
Sunawer Aujla
Yvette Ysabel Yao
Yan Yu*
Gary Michael Klein*
* MD at time of publication
Vertical/oblique Diplopia (double vision)
Hypertropia (one eye is deviated upward compared to the other)
Perinaud’s Syndrome (upgaze palsy, convergence retraction nystagmus, and pupillary hyporeflexia)
See relevant Calgary Guide slide on Parinaud’s Syndrome
Loss of eye muscle movement coordination and function of other structures relating to gait
Ipsilateral Primary Horner’s Syndrome (miosis, anhidrosis, ptosis)
See relevant Calgary Guide slide on Horner Syndrome
Sign/Symptom/Lab Finding
Published January 16, 2024 on