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\begin{document}

\title{Transient cortical blindness after coronary artery bypass surgery}



\author[1]{Seyed Mirhosseini}%
\author[2]{Hossein Yarmohammadi}%
\author[2]{Amir Rostami}%
\author[3]{Masood Soltanipur}%
\author[3]{mahdi rezaei}%
\affil[1]{Shahid Beheshti University of Medical Sciences}%
\affil[2]{Shahed University}%
\affil[3]{Shahed University Faculty of Medical Sciences}%


\vspace{-1em}



  
  \date{June 14, 2024}


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\textbf{Introduction}

Transient cortical blindness (TCB) is an infrequent and intriguing
postoperative complication following cardiac surgery. It is
characterized by the sudden and temporary loss of vision in both eyes,
usually resolving within hours (1). By reporting this rare occurrence of
TCB after coronary artery bypass grafting (CABG) surgery, we aim to
raise awareness among clinicians and researchers about this potential
complication.

\textbf{Case}

A 54-year-old non-diabetic woman complaining of chest pain with a
history of myocardial infarction (MI) and percutaneous coronary
intervention about 13 years ago was evaluated. Her drug history included
nitroglycerin, atorvastatin, and, aspirin. Before the operation, her
ejection fraction was 40\% and the carotid Doppler showed no
abnormality. Also, angiography revealed 80\%, 90\%, and 60\% stenosis in
the left anterior descending (LAD), diagonal artery, and right coronary
artery respectively. Bypass grafts were implanted as the left internal
mammary artery to the LAD artery, the saphenous vein to the obtuse
marginal and ramus artery, however, right coronary artery bypass
grafting was incapable. During surgery, the blood runoff was good.
Additionally, iodinated contrast agent was used and the time of the
operation and aortic clamp duration were 128 minutes and 70 minutes
respectively.

The patient was asymptomatic after the operation but started to have
bilateral blurring of vision three days after the surgery, which
worsened drastically over 2 weeks. After this period, she only was able
to perceive light bilaterally and her vision improved gradually for 2
months. After the surgery, vital signs were good, had no change of
electrocardiogram or enzymes, and cardiac status was stable. The
ophthalmology examination detected no causative ocular damage except
bilateral papilledema and reduced visual acuity at the level of light
perception. So, as the initial management, intravenous hydrocortisone
was administrated (100 mg bd for three days). A non-contrast computed
tomography (CT)-Scan revealed bilateral subarachnoid hyperdensities in
the occipital and parietal lobes. Hence to confirm cerebral hemorrhage,
magnetic resonance imaging (MRI) was done which showed no evidence of
hemorrhage. The evaluation of related arteries (carotid, vertebral and
ophthalmic) was completely normal. Nevertheless, the patient remained
under close observation with no additional intervention. Finally, her
vision completely recovered after two months and remained with no other
complications during the further follow-up.

\textbf{Discussion}

TCB is an uncommon but potentially severe and stress-full complication
that has been mainly associated with cerebral and vertebral angiography
(2, 3). Reports on TCB following CABG have also existed in the
literature since the 1990s (4, 5). The pathophysiology of TCB remains
incompletely understood, but several proposed mechanisms may shed light
on its occurrence. Hyperosmolar iodinated contrast agents have been
associated with TCB occurrences (1). Contrast agents may induce a
disruption of the blood-brain barrier, leading to the infiltration of
the contrast in to the brain parenchyma. This localized infiltration,
particularly affecting the occipital lobes, may result in an
inflammatory response, potentially contributing to the sudden onset of
cortical blindness (6).

It is worth noting that not all cases of TCB involve hyperosmolar
iodinated contrast agents. Reports have shown that non-ionic contrast
agents, which are considered less osmotically active, have also been
associated with TCB incidents (7). Although the use of non-ionic and
hypoosmolar contrast agents was expected to mitigate the risk of TCB, it
is evident that this measure does not provide complete prevention (7).
This discrepancy suggests that factors beyond the osmolarity of contrast
agents may be involved in the development of TCB.

In the presented case, bilateral subarachnoid hyperdensities in the
occipital and parietal lobes were observed in the non-contrast CT scan.
However, subsequent MRI findings did not show any pathological
abnormalities. This inconsistency raises questions about the nature of
the observed hyperdensities and their relation to transient cortical
blindness. A similar case reported by Zhen-Vin Lee also displayed acute
subarachnoid bleeding in both occipital lobes on a CT scan but a normal
MRI, further emphasizing the transient nature of these changes and the
lack of lasting damage associated with TCB (8). This highlights the
importance of MRI in the work-up of these patients, however, the
diagnosis of TCB remains to be based on clinical presentation mostly.
The prognosis for TCB is generally favorable, with most cases resolving
within hours, as observed in this patient (9). In conclusion, clinicians
should be vigilant about the possibility of TCB following coronary
angiography and CABG procedures. Additionally, patients undergoing these
procedures should be informed about the potential risk of TCB, and close
monitoring for signs and symptoms of this condition is advised.

\textbf{Ethical Approval}

The patient signed an informed consent form.

\textbf{References}

1. Gellen B, Remp T, Mayer T, Milz P, Franz W-M. Cortical blindness: a
rare but dramatic complication following coronary angiography.
Cardiology. 2003;99(1):57-9.

2. Tong X, Hu P, Hong T, Li M, Zhang P, Li G, et al. Transient cortical
blindness associated with endovascular procedures for intracranial
aneurysms. World Neurosurgery. 2018;119:123-31.

3. Li M, Liang H, Liu C, Liu H, Zheng Y, Shi W, et al. Risk factors of
transient cortical blindness after cerebral angiography: a multicenter
study. Frontiers in Neurology. 2019;10:1005.

4. Kamata J, Fukami K, Yoshida H, Mizunuma Y, Moriai N, Takino T, et al.
Transient cortical blindness following bypass graft angiography: a case
report. Angiology. 1995;46(10):937-46.

5. Sticherling C, Berkefeld J, Auch-Schwelk W, Lanfermann H. Transient
bilateral cortical blindness after coronary angiography. The Lancet.
1998;351(9102):570.

6. Alp B, Bozbu\selectlanguage{polish}ğ\selectlanguage{english}a N, Tuncer M, Yakut C. Transient cortical blindness
after coronary angiography. Journal of International Medical Research.
2009;37(4):1246-51.

7. Yazici M, Ozhan H, Kinay O, Kilicaslan B, Karaca M, Cece H, et al.
Transient cortical blindness after cardiac catheterization with
iobitridol. Texas Heart Institute Journal. 2007;34(3):373.

8. Lee Z-V, Singh RSA. Transient cortical blindness after coronary
angiography, bypass graft angiography, and coronary angioplasty. Cureus.
2021;13(1).

9. Akhtar N, Khatri IA, Naseer A, Ikram J, Ahmed W. Transient cortical
blindness after coronary angiography: a case report and literature
review. JPMA The Journal of the Pakistan Medical Association.
2011;61(3):295-7.

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