Midbrain Infarction Causing Diplopia and Atypical Neurological Symptoms: An Abducens Palsy Review
A 68 year old white male reports distance horizontal diplopia immediately following a cerebrovascular accident.
Neuroimaging shows acute right midbrain infarction. While rarely associated with stroke, neurologic sixth nerve palsies occur and entail further workup.
i. CASE HISTORY
a. PT DEMOGRAPHICS: 68 year old white male
b. CHIEF COMPLAINT: On 8/12/16 patient reports recent onset of horizontal diplopia in the distance
for two weeks and reduction of right gaze. Noted diplopia, dizziness, and trace left sided
extremity/facial weakness after recent stroke on 07/28/16, but reported no pain, visual field loss,
or ataxia.
c. OCULAR HISTORY:
i. Mild Non-Proliferative Diabetic Retinopathy OS (10-2015)
d. MEDICAL HISTORY
i. 1999: Diabetes Mellitus
ii. 1999: Hypertension
iii. 1999: Hyperlipidemia
iv. 2009: Cerebrovascular accident
v. 2009: Right vertebral artery stent
vi. 2014: Transient ischemic attack
vii. 2014: Severe posterior circulation disease
e. MEDICATIONS
i. Metformin
ii. Amlodipine
iii. Hydrochlorothiazide
iv. Lisinopril
v. Tamsulosin
vi. Clopidogrel bisulfate
f. OTHER SALIENT INFORMATION
i. MRI 06-26-09; Subacute infarction in left ventral pons ii. MRI 04-20-16; Subacute infarction of left caudate
iii. CT Brain without contrast 06-25-09; Subacute infarction in left ventral pons
iv. CT Brain without contrast 01-02-16; unremarkable
ii. PERTINENT FINDINGS
a. CLINICAL
i. Vision
1. OD: 20/20-1 cc
2. OS: 20/20 cc
ii. Pupils: equal, round and reactive to light with no afferent defect
iii. Cover Test (thru habitual Rx)
1. Distance: 10^ Right Esotropia
2. Near: ~4^ Right Esotropia
iv. Maddox Rod: 15^ Base Out OD at distance
v. Subjective Prism: 12^ base out OD eliminated diplopia
vi. Extraocular Motility: Limited right abduction by approximately 30% (IMAGE OF PATIENT)
1. (+) right gaze diplopia, (-) pain
vii. Confrontations: Full to finger count
viii. Anterior Segment: Unremarkable with (-) ptosis, iris neovascularization
ix. Posterior Segment: Unremarkable with (-) optic nerve pallor, neovascularization, hemes,
cotton wool spots, exudates
b. PHYSICAL
i. Results from neurology examination 07-29-16 (Summarized)
c. SELECTED LABORATORY STUDIES
i. Vitals- 08/04/16
1. Blood Pressure: 148/72
2. Pulse: 58
ii. Labs
1. Glucose -08/03/16
a. 113
2. HbA1C- 07/30/16
a. 6.1% d. RADIOLOGY STUDIES
i. CT Brain with contrast 07-29-16
1. No pertinent findings
ii. MRI Brain without contrast 07-29-16 (IMAGE OF PATIENT’S MRI)
1. Radiology Impression
“Acute infarct right paramedian pontomedullary junction with multiple remote
infarcts and chronic microangiopathy” iii. DIFFERENTIAL DIAGNOSIS
a. PRIMARY/LEADING
i. Gaze paresis secondary to vascular disease
1. Most common cause of CN 6 palsy
b. OTHERS
i. Aneurysm
ii. Tumor
iii. Muscle entrapment
iv. Giant cell arteritis
vi. Raymonds Syndrome
vii. Millard Gubler Syndrome
viii. Foville’s Syndrome
ix. Internuclear ophthalmoplegia iv. DIAGNOSIS AND DISCUSSION
a. FINAL DIAGNOSIS: Cranial nerve 6 palsy with neurological findings secondary to midbrain
infarction
i. MRI confirms acute right infarct, at the right paramedian pontomedullary junction
b. ELABORATE ON CONDITION—Cranial Nerve 6 Palsy
1. Horizontal diplopia greater in distance
2. Abduction defect
3. Esotropia at distance
a. Ipsilateral to abduction defect
ii. Epidemiology 1. 11.3 in 100,0004
a. Most common of all Cranial Nerve Palsies
2. 15% of all CN 6 palsies caused by Stroke5
3. Literature reveals 5.8% of stroke cohort had a CN 6 palsy8
4. 47% of all stroke causing CN palsies occur in brainstem cerebellum8
c. EXPOUND ON UNIQUE FEATURES—Cranial Nerve 6 Palsy due to midbrain infarction
i. Nuclear 6th Cranial Nerve Palsy
1. Ipsilateral gaze palsy that cannot be overcome by vestibular testing
a. Contralateral abduction weakness
b. Ipsilateral peripheral facial nerve palsy
i. One and a half syndrome
ii. Foville’s syndrome
iii. Gaze palsy
ii. Fascicular 6th Cranial Nerve Palsy
1. Results from location of surrounding structures in the Pons
a. Contralateral hemiplegia
i. Raymond’s syndrome
b. Ipsilateral facial weakness with contralateral hemiplegia
i. Millard Gubler Syndrome
2. **UNIQUE FEATURES OF THIS PATIENT**
a. trace contralateral limb weakness
b. trace contralateral facial weakness
iii. Recommended Neuro-Ophthalmic Evaluation
1. Cranial nerve testing
2. Vestibular system and cerebellum testing
3. Evaluation of deep tendon reflexes and peripheral motor system
4. Optic nerve head evaluation v. TREATMENT AND RESPONSE TO TREATMENT
a. TREATMENT OPTIONS
i. Patching paretic eye or frosting spectacle lens
ii. Temporary Fresnel Prism
iii. Injection of Botulinum Toxin in ipsilateral medial rectus muscle iv. Surgical intervention
1. Indicated after 6 months of stable deviation
b. PROGNOSIS
i. Approximately 50% of all CN6 palsies resolve spontaneously after onset (within 3
months) 4
1. Vasculopathic etiologies resolve more rapidly (4-6 weeks) 4
ii. 31-35% recurrence rate for vasculopathic patients 4
c. MANAGEMENT OF CASE
i. 12^ BO Fresnel Prism placed on right lens
ii. Patient to Return to Clinic on 9/12/16 for follow up
vi. CONCLUSION
a. Sixth cranial nerve palsies are the most common oculomotor cranial nerve palsies
i. Most often caused by vasculopathic disorders in at risk patients over 50 years old.
1. Current treatment protocol does not indicate neuroimaging for these patients.
b. When neurological findings are present with cranial nerve palsy, more severe diagnoses should
be considered such as cerebrovascular accident, neoplasm or aneurysm.
c. Midbrain infarctions causing a sixth cranial nerve palsy are rare and are often associated with
additional gaze deficits, facial paresis, or hemiplegia.
d. Any patient diagnosed with CN6 palsy and presenting with additional neurological symptoms
should be sent for neuroimaging and a further neurological workup regardless of age or presence
of vascular risk factors.
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