A 65 year old male presents to your office with complaints of horizontal diplopia. He says he woke up with double vision about a week ago and it is unchanged since. The images appear to be side by side and is worst on lateral gaze. He has no other ocular symptoms such as decreased vision, pain, or photophobia and has never had diplopia before. There is no history of eye trauma. On review of systems he has no other symptoms such as headache, neck stiffness, nausea, vomiting, muscle weakness, or numbness.
The patient’s past medical history is significant for type 2 diabetes for 20 years, hypertension, dyslipidemia and gastroesophageal reflux disease. Medications include metformin, norvasc, hydrochlorothiazide, lipitor, and aspirin. His past ocular history is significant for nonproliferative diabetic retinopathy with past laser treatments for clinically significant macular edema.
On exam, visual acuity is 20/30 bilaterally. Pupils are equal and reactive to light and accommodation, with no afferent pupillary defect. On testing of extraocular movements, there is a limitation of adduction as shown below:
What is the most likely diagnosis?
• Idiopathic sixth nerve palsy
Idiopathic sixth nerve palsy is relatively common cause in children, however in an adult especially with vascular risk factors this is less likely.
• Fourth nerve palsy
The pattern of gaze restriction in the case is not consistent with fourth nerve palsy as the cause of diplopia.
• Vasculopathic sixth nerve palsy
• Cerebral neoplasm
INCORRECT A neoplasm would be in the differential diagnosis of sixth nerve pals, however at this point other potential causes would be more likely.