An elderly female comes into the emergency department complaining of swelling around her left eye. The swelling began a couple months ago and has gotten progressively worse. It is associated with redness in the eye as well as blurry vision. Interestingly, the patient complains that her eye “pops out” in the morning after she has been lying flat at night. She also has recently developed double vision when looking side to side.
When you examine her, you note the area around the left eye appears swollen and erythematous. She has binocular diplopia. When she looks side to side, you note a deficit in outward movement of the left eye. A head CT is performed:
What is your differential diagnosis? What would your diagnostic workup and/or management be?
Scroll down for the Case Conclusion.
Final diagnosis: Carotid-cavernous fistula
Case Conclusion: The patient had an MRV performed which demonstrated edema of the extra ocular muscles of the left eye as well as engorgement of the left superior ophthalmic vein. This was considered suspicious for a low-flow carotid-cavernous fistula and she was referred to neurointerventional radiology who performed a cerebral angiogram confirming this diagnosis. One week later, the patient underwent transvenous endovascular venous embolization via the left superior ophthalmic vein.
Learning Points: Like many presentations in emergency medicine, ophthalmologic complaints can have either a benign or deadly cause. The complaint of diplopia has a particularly important differential. The first step in approaching diplopia involves assessment of whether the diplopia is monocular or binocular. Monocular diplopia (present when one of the eyes is covered) is almost always localized to the eye itself (or to glasses or contact lenses). Binocular diplopia, however, points to an extra-ocular and often neurologic cause, such as stroke, demyelinating disorder, structural cause such as tumor or vascular anomaly, or muscular disorder including myasthenia gravis .
Once the diagnosis of binocular diplopia is made, patients should be examined carefully for misalignment of the eyes in different positions of gaze and for restriction of eye motility, as this will further narrow the differential diagnosis . Patients should also have a full neurologic exam to identify any co-existing neurologic findings which would suggest a more serious underlying etiology. In this patient, the combination of horizontal double vision and the inability to move the left eye laterally is consistent with an Abducens or 6th cranial nerve palsy. The differential diagnosis of an acute 6th nerve palsy is also broad, as it can be due to nerve interference anywhere along extensive course of the 6th cranial nerve from the pons to orbit [Figure 1] . In the absence of trauma or other signs on physical exam, neurologically-isolated 6th nerve palsies are most often due to hypertension, diabetes or a combination of thereof . However, other neurologic or physical findings (such as proptosis) suggest a more serious underlying cause.
The cause of this patient’s sixth nerve palsy and proptosis was a carotid-cavernous fistula. The cavernous sinus is a trabeculated venous cavity located just lateral to the sella turcica containing several important vascular and neural structures [Figure 2]. The cavernous sinus receives drainage from the superior ophthalmic vein, superficial sylvian vein, and the sphenoparietal sinus. Venous congestion due to cavernous sinus pathology can lead to ocular and orbital symptoms, including proptosis, chemosis, conjunctival injection, and increased intraocular pressure. Infection (especially from facial, dental or sinus sources), vascular anomalies, and mass-occupying lesions must be considered in any patient presenting with this constellation of symptoms especially in the presence of cranial nerve deficits.
Carotid-cavernous fistulas [CCFs] are the result of the intimate anatomic relationship of the internal carotid artery and cavernous sinus [Figure 2]. CCFs are classified by etiology (traumatic vs. non-traumatic), anatomy (direct vs. indirect), and hemodynamics (high flow vs. low flow) [Figure 3]. The most common etiology of all CCFs is trauma, and they have been reported in up to 4% of patients who sustain a basilar skull fracture . They can occur as a direct result of tearing of the carotid artery by bony fracture or by shear forces during the traumatic incident (and thus can also occur in the absence of fracture). Traumatic CCFs, as they are direct communications between the carotid and the cavernous sinus, typically present acutely and progress rapidly. Patients will have diplopia (88%), visual disturbance, proptosis (72-98%, sometimes pulsatile), chemosis (55-100%), and other cranial nerve deficits (facial numbness due to involvement of Cranial nerve V). Alternatively, spontaneous CCFs are more typically found in older females such as our patient. They can be direct, high flow fistulas with more dramatic presentations (such as would be due to rupture of a cavernous sinus aneurysm) or be indirect, low-flow in nature and have a more insidious onset. Amongst low-flow CFs, conjunctival injection is the most common feature and patients are often commonly treated for other conditions such as conjunctivitis before the correct diagnosis is made. 81% of patients will have proptosis, 61% will have diplopia, and 34% will have elevated intraocular pressure.
Cerebral angiography is the gold standard for diagnosis of CCFs, most patients undergo non-invasive imaging in the form of CT scan or MRI. Indirect signs of CCF include cavernous sinus enlargement, proptosis, extra-ocular muscle enlargement, and superior ophthalmic vein dilation . The absence of abnormalities on non-invasive imaging does not exclude the diagnosis of CCF, and in the context of high clinical suspicion, patients should be referred for diagnostic cerebral angiography. While patients use to undergo surgical intervention, endovascular therapy is now much more common.
Case Conclusion by Maia Dorsett (@maiadorsett)
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