Summary: A 49-year-old white man with a medical history of coronary artery
disease, diabetes mellitus, and hypertension underwent 6-vessel coronary
artery bypass grafting (CABG) with subsequent loss of vision in both
eyes. Postoperative ophthalmologic examination revealed no reaction to
light, profound bilateral optic nerve pallor, and no evidence of emboli
or arterial occlusion. Magnetic resonance (MR) imaging of the orbits was
performed 2 weeks later at our institution.
Ischemic optic neuropathy (ION)
Dedicated imaging of the orbits with and without contrast administration
(using fat-suppression techniques) revealed faint areas of increased
signal on short tau inversion recovery (STIR) sequences and intense,
patchy enhancement of both the optic nerves following contrast
administration (Figures 1 and 2). The MR images of the head and the MR
angiogram of the head revealed no additional abnormalities (not shown).
Ischemic optic neuropathy is an uncommon complication of a variety of
procedures including CABG, cholecystectomy, radical neck dissection,1 spinal fusion,2 endoscopic sinus surgery,3 and liposuction.4 Over a period of 14 years, the incidence of ION following cardiopulmonary bypass surgery increased from 0.1% to 1.3% in 1996.1,5 Following glaucoma, ION is the second most common optic neuropathy in adults.6 Shapira et al5 found
that patients with ION after cardiopulmonary bypass had prolonged
bypass times and lower hematocrits and also required high doses of
inotropic drugs to maintain cardiac output.
neuropathy can be divided into anterior and posterior forms. In anterior
ION, the insult is thought to be caused by occlusion of the short
posterior ciliary arteries, with resultant ischemia of the optic nerve
head. Posterior ION is caused by occlusion of the circumferential pial
branches of the ophthalmic artery, which places the retrolaminar optic
nerve at an increased risk of ischemia during long procedures,
particularly those characterized by long periods of hypotension and
large amounts of blood loss.1
MR imaging of the brain
and orbits is a useful tool in the evaluation of the patient with acute
onset of visual loss following surgery. In our patient, MR imaging
served as a conﬁrmatory test following the clinical diagnosis of ION and
aided in the exclusion of other etiologies, such as multiple sclerosis
or embolic infarcts. Vaphiades7 reported a case of optic
nerve enhancement with ION following a hypotensive episode related to
CABG, and our case corroborates these ﬁndings. In the Vaphiades7 case, the optic nerves continued to exhibit enhancement on a follow-up MR performed 16 weeks after surgery.
Vaphiades’7 and our ﬁndings of optic nerve enhancement differ, however, from the bulk of reported literature regarding ION. Rizzo et al8 compared
the MR ﬁndings of ION with MR ﬁndings of optic neuritis in patients
with multiple sclerosis and found that only 5 of 32 patients with
clinical diagnoses of ION demonstrated MR abnormalities. It is unknown
which, if any, of the patients in the Rizzo8 series developed
ION postoperatively. In all 5 of the patients with MR abnormalities,
increased signal was seen in the affected optic nerves on STIR
sequences, while only 2 showed associated enhancement of the optic
nerves.8 The MR technique and the time from symptom onset to MR evaluation is comparable in our case to those in Rizzo’s study.8 Our
patient was imaged 2 weeks following the onset of symptoms, while the
patients in Rizzo’s study were imaged an average of 22 days following
symptom onset. The 2 patients in Rizzo’s study who exhibited optic nerve
enhancement on MR were imaged within 14 days of symptom onset.8 Postulated
theories for the etiology of optic nerve enhancement in ION include a
demyelinating process or ischemic compromise of the blood-brain barrier.
Ischemic optic neuropathy is a devastating but, fortunately, infrequent
complication of various surgical procedures, particularly those
characterized by hypotension and a loss of large volumes of blood. We
present a patient with postoperative blindness secondary to posterior
ION with MR ﬁndings of patchy enhancement of the optic nerves. While MR
changes with ION is thought to be unusual, optic nerve enhancement with
ION may be more common than previously suspected. It is important for
radiologists to recognize the MR ﬁndings of ION, particularly when
evaluating patients with postprocedure blindness.
- Remigio D, Wertenbaker C. Post-operative bilateral vision loss. Surv Ophthalmol. 2000;44:426-432.
- Dilger JA, Tetzlaff JE, Bell GR, et al. Ischemic optic neuropathy after spinal fusion. Can J Anaesth. 1998; 45(1):63-66.
JC, Chuo PI, Hsiung MW. Ischemic optic neuropathy after endoscopic
sinus surgery: A case report. Eur Arch Otorhinolaryngology. 2003;260:
- Minagar A, Schatz NJ, Glaser JS. Liposuction and
ischemic optic neuropathy: Case report and review of literature. J
Neurol Sci. 2000;181:132-136.
- Shapira OM, Kimmel WA, Lindsey PS,
Shahian DM. Anterior ischemic optic neuropathy after open heart
operations. Ann Thorac Surg. 1996;61:660-666.
- Moster ML. Visual loss after coronary artery bypass surgery. Surv Ophthalmol. 1998;42:453-457.
- Vaphiades MS. Optic nerve enhancement in hypotensive ischemic optic neuropathy. J Neuroophthalmol. 2004;24:235-236.
JF 3rd, Andreoli CM, Rabinov JD. Use of magnetic resonance imaging to
differentiate optic neuritis and nonarteritic anterior ischemic optic
neuropathy. Ophthalmology. 2002;109: 1679-1684.