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.