Cranial Nerve VI Palsy

Cranial Nerve VI Palsy
SYMPTOMS Horizontal diplopia especially at distance
SIGNS Esotropia in primary gaze, Inability to abduct, Esodeviation is worse when looking in direction of affected eye, Head turn toward the affected eye
WORK-UP Pupils | EOMs | Cover test | Complete eye exam with dilation | Cranial nerve testing | OCT of the optic nerve (Rule out papilledema) | Forced duction testing
TREATMENT If cranial nerve VI palsy is acute onset and due to trauma, the patient should be referred to a neuro-ophthalmologist/neurologist/PCP/ER ASAP
Children or Adults under the age of 50 years old with an acute onset CN VI palsy should be referred to a pediatric ophthalmologist/pediatrician/neuro-ophthalmologist/neurologist/PCP/ER ASAP
Adults over the age of 50 years old with an acute onset CN VI palsy can be observed and referred to their PCP for a vascular work-up but strong consideration should be given to referring patient to a neuro-ophthalmologist/neurologist/PCP/ER if there is no improvement within 1 month, if there is progression, if there is aberrant regeneration, if there are other neurological symptoms, if there is a history of cancer, if there is optic nerve edema, or if CN VI palsy is bilateral
Fresnel prisms can temporarily help with diplopia with acute onset CN VI palsies
Treatment depends on the underlying etiology of the CN IV palsy
FOLLOW-UP Monitor monthly until complete resolution
ADDITIONAL LAB | TESTS Neuro-imaging is typically ordered through neuro-ophthalmologist/neurologist/PCP/pediatric ophthalmologist/pediatrician/ER and may include the following: MRI of the brain with and without contrast | CT of the brain with and without contrast | MRA | CTA | Lumbar puncture
If etiology is suspected to be due to vascular ischemia or inflammatory, the following should be ordered through the patient’s PCP: Blood pressure evaluation | Fasting blood sugar | HbA1c | CBC with differential | ESR | C-reactive protein | ANA | Lyme titer | ACE
ETIOLOGY Cranial nerve VI damage (from any point from the pons to the lateral rectus muscle) can be secondary to the following: Vascular ischemia from systemic diseases such as diabetes | Trauma | MS | Meningitis | Increased intracranial pressure Compression from a tumor or aneurysm | Infiltrative | Congenital due to incomplete development of the nucleus or nerve (Uncommon)
There are many potential etiologies as CN VI has the longest intracranial course of any cranial nerve
DIFFERENTIAL DX Myasthenia gravis, Duane syndrome, Thyroid eye disease, Pseudotumor cerebri, Internuclear ophthalmoplegia, Chronic progressive external ophthalmoplegia
NOTES The most common EOM palsy in adults

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