Paracentral acute middle maculopathy immediately following internal carotid endovascular repair

Summary

Paracentral acute middle maculopathy (PAMM) can result from decreased perfusion to retinal and choroidal circulations meeting in the inner nuclear layer (INL) and outer plexiform layer (OPL). Although ischemia in these layers is rare, certain procedures place patients at risk for possible events, such as cardiopulmonary bypass, coronary angiography, and endovascular coil embolization. We report the case of a 70-year-old woman with a sudden-onset left paracentral scotoma following internal carotid endovascular repair. Currently no treatment or preventive technique is available. Additional ischemic events can occur if a preventable cause is not identified.

Introduction

Paracentral acute middle maculopathy (PAMM) is characterized by hyperreflectivity in the inner nuclear layer (INL) with subsequent atrophy.1 This was first observed and described on spectral domain ocular coherence tomography (SD-OCT) in 2013.1,2 Initially thought to be a superficially focused variant of acute macular neuroretinopathy (AMN) and described as type 1 AMN, it is now understood to be a separate entity, owing to differences in incidence, demographic distribution, and risk factors.1,3 It is thought to be a result of middle retinal ischemia and has been associated with retinal artery and venous occlusions.2 Presenting signs are typically sudden-onset paracentral scotoma, with preserved or mildly reduced visual acuity.2 Numerous etiologies have been correlated with PAMM, including oral contraceptives, hypertensive retinopathy, sickle cell retinopathy, diabetic retinopathy, and central retinal vein or artery occlusions. Case reports have also documented PAMM lesions associated with endovascular repair.4–6 Herein, we report the case of a woman with a PAMM lesion after undergoing an aneurysmal endovascular repair.

Case Report

A 70-year-old woman with a past medical history of systemic arterial hypertension, occipital neuralgia after ablation, fibromyalgia, and 20-pack year smoking history presented with severe headaches to her primary care physician. On workup, she was incidentally found to have a left internal carotid artery (LICA) aneurysm. The headaches resolved without intervention, but the patient elected to proceed with embolization of the aneurysm. This LICA aneurysm was treated with flow diverter embolization, with no intraoperative complications. At the time of surgery, there was concern for subarachnoid hemorrhage, given artifact on intraoperative computed tomography (CT) scan, but this was not present on post-procedure CT. Upon anesthesia reversal, the patient noted a new, persistent, paracentral scotoma in her left eye, described as a “blurry spot.”

One month later, the patient presented to the ophthalmology clinic. Her best-corrected visual acuity was 20/20⁻² in the right eye and 20/30 in the left eye. Prior corrected visual acuity was 20/30⁻² in the right eye and 20/30⁺² in the left eye. Intraocular pressure was 18 mm Hg in each eye. Pupils were equal, round, and reactive to light, with no relative afferent pupillary defect. Confrontation visual fields and extraocular movements were full. Slit-lamp examination demonstrated posterior chamber intraocular lenses in both eyes. A dilated fundus examination revealed faint retinal whitening nasal to the fovea in the left eye without hemorrhage (Figure 1). Posterior segment examination of the right eye was unremarkable. There was no disc edema in either eye. Optical coherence tomography (OCT) demonstrated a small area of retinal hyperreflectivity at the INL just nasal to the fovea corresponding to the funduscopic finding (Figure 2). OCT angiography (OCTA) did not demonstrate any associated choroidal neovascular membrane (Figure 3). The patient declined further visual field testing, follow-up clinic visits, and ophthalmic imaging.

Figure 1.

Fundus photograph showing faint area of retinal whitening indicating ischemia nasal to the fovea (red arrow).

Figure 2.

Optical coherence tomography demonstrating a small area of retinal hyperreflectivity at the inner nuclear layer just nasal to the fovea and corresponding to the funduscopic finding.

Figure 3.

Optical coherence tomography angiography of the superficial capillary plexus (A), deep capillary plexus (B), and choriocapillaris (C) did not demonstrate any acute choroidal neovascular membrane or vessel dropout.

Discussion

The proposed pathophysiology of PAMM is a result of retinal and choroidal circulations meeting in the INL and outer plexiform layer (OPL). This watershed area is more sensitive to decreased perfusion. PAMM has been associated with vasoconstricting substances (such as the performance-enhancing drug synephrine and caffeine) and medications, retinal vascular diseases, and systemic conditions.1,2,7

PAMM has been described following vascular surgeries, such as an aortic aneurysm repair, cardiopulmonary bypass, and coronary angiography, with symptom onset from 5 hours to 3 days after the associated procedure.4,6,8 Slit-lamp examination revealed one area of retinal whitening in the cases of coronary angiography and aortic aneurysm repair.4,6 Two cases of PAMM following endovascular coil embolization of an internal carotid artery aneurysm and anterior communicating artery aneurysm have been described in the literature.5 In both cases, the onset of symptoms occurred within 1 day of surgery, and slit-lamp examination revealed multiple white-yellow retinal lesions. Fluorescein angiography in 1 patient revealed delayed filling at the parafoveal lesions. Our patient experienced a similarly rapid onset of vision changes following endovascular surgery; her scotoma was present upon awakening from anesthesia. However, only one area of retinal whitening was seen.

We present a case of immediate development of PAMM following endovascular repair of an internal carotid artery aneurysm. The etiology of this patient’s PAMM was likely secondary to intraoperative hypotension, resulting in retinal hypoperfusion. The parafoveal region receives blood supply via a network of three capillary plexuses: the superficial capillary plexus (SCP), the intermediate capillary plexus (ICP), and the deep capillary plexus (DCP). Together, the ICP and DCP are referred to as the deep vascular complex (DVC).9 Decreased flow in the DCP or DVC can lead to infarction of the INL, resulting in PAMM.10 Patients with PAMM have been shown to have decreased capillary flow with capillary dilation in the area of the lesion at the DCP on follow-up years after symptom onset.11 While longitudinal follow-up has shown that gradual resolution of retinal lesions on funduscopy can occur over a few weeks, persistent OCT changes indicate the ischemia these lesions reflect has long-term impacts on the retina.11 In the literature, aneurysm treatment using endovascular flow-diverter devices has a mean rate of ischemic complications of 4.1%.12

There is currently no treatment for PAMM. Identification of any underlying cause or contributory disease and management of risk factors is recommended. In some cases, the funduscopic findings may appear normal, but OCT can demonstrate PAMM and alert providers of milder forms of retinal vascular obstruction.13–15 Serial examinations are recommended to document new lesions or signs of occult vascular occlusion, which may be masked by diffuse PAMM lesions.3 The development of retinal ischemia, including PAMM, should be included in a preoperative discussion with patients who are undergoing endovascular repair. Suspicion for retinal ischemia should be referred to ophthalmology for continued monitoring for complications and possible treatment to preserve vision.