A 54-year-old woman comes to the emergency department due to double vision and a droopy eyelid. The patient began seeing 2 side-by-side images while watching television last night. She attributed the symptoms to tiredness and went to bed. The vision disturbance was persistent on waking up today, and the patient also found her right eyelid was drooping. The diplopia is worse when looking toward the left and is not associated with headache, nausea, dizziness, or focal weakness or numbness. Physical examination shows ptosis of the right eye. Adduction and upward gaze are impaired on the right side. Pupils are 2 mm on the left and 5 mm on the right, and both are reactive to light. Examination of other cranial nerves is unremarkable. Upper and lower extremity strength, deep tendon reflexes, and sensation are normal. Noncontrast CT scan of the head is normal. Which of the following is the best next step in evaluation of this patient?

Question

A 54-year-old woman comes to the emergency department due to double vision and a droopy eyelid.  The patient began seeing 2 side-by-side images while watching television last night.  She attributed the symptoms to tiredness and went to bed.  The vision disturbance was persistent on waking up today, and the patient also found her right eyelid was drooping.  The diplopia is worse when looking toward the left and is not associated with headache, nausea, dizziness, or focal weakness or numbness.  Physical examination shows ptosis of the right eye.  Adduction and upward gaze are impaired on the right side.  Pupils are 2 mm on the left and 5 mm on the right, and both are reactive to light.  Examination of other cranial nerves is unremarkable.  Upper and lower extremity strength, deep tendon reflexes, and sensation are normal.  Noncontrast CT scan of the head is normal.  Which of the following is the best next step in evaluation of this patient?

Quizplus · Accepted Answer

Explanation: This patient with diplopia, right eye ptosis, ophthalmoplegia, and pupillary dilation has an acute non-pupil-sparing oculomotor nerve (cranial nerve [CN] III) palsy. CN III has parasympathetic and motor fibers. The parasympathetic fibers are responsible for pupil constriction by controlling the sphincter papillae muscle; disruption can lead to pupilary dilation. Motor fiber involvement can lead to ptosis ("droopy eyelid") due to paralysis of the levator palpebrae superioris. In addition, paralysis of the inferior oblique and superior, inferior, and medial recti (all of which are innervated by CN III) can result in a down-and-outward position of the eye due to the unopposed pull of the superior oblique muscle (innervated by CN IV) and lateral rectus muscle (innervated by CN VI). As a result, patients can develop sudden-onset diplopia. CN III palsies most commonly occur from compression (eg, aneurysm, tumor) or microvascular ischemia. The somatic (motor) components of CN III run within the nerve and are typically damaged by both etiologies. By contrast, the parasympathetic fibers responsible for pupil constriction run on the outside of the CN III fascicle; these are less susceptible to ischemia but are almost invariably affected by an extrinsic compression. Therefore, pupillary involvement can help distinguish the etiology of an isolated CN III palsy. Non-pupil-sparing CN III palsies are frequently caused by mass effect and should be considered due to an intracranial aneurysm until proved otherwise. Patients should undergo immediate MR or CT angiography of the head for evaluation. Pupil-sparing CN III palsies are typically caused by microvascular ischemia and are associated with diabetes, hypertension, hyperlipidemia, and advanced age. Observation and supportive care may be appropriate in patients with vasculopathic risk factors (eg, diabetes, hypertension). (Choice A) Anti-acetylcholine receptor antibody assay is used to diagnose myasthenia gravis, which causes fluctuating weakness that worsens throughout the day. Ocular myasthenia gravis causes ptosis, but pupillary response is spared. (Choice C) Hemoglobin A1c is indicated to evaluate a pupil-sparing CN III palsy, which is often due to microvascular ischemia. (Choice D) MRI of the orbits is useful to evaluate orbital disease (eg, tumor) or inflammation. These can cause compression of CN III but would be also be expected to cause proptosis, optic neuropathy, and chemosis. In addition, orbital tumors would likely be visible on head CT. (Choice E) Graves disease can cause ophthalmopathy with diplopia but exophthalmos, periorbital edema, and lid lag are expected on examination. The pupils are not affected. Educational objective: Non-pupil-sparing oculomotor nerve (CN III) palsies are concerning for aneurysmal compression. MR or CT angiography should be performed immediately. Pupil-sparing CN III palsies are most commonly caused by microvascular ischemia associated with diabetes mellitus, hypertension, and hyperlipidemia. References: Isolated ocular motor nerve palsies. (http://www.ncbi.nlm.nih.gov/pubmed/26444399)

A 54-Year-Old Woman Comes to the Emergency Department Due to Double