Acute macular neuroretinopathy (AMN) was reported initially by Bos and Deutman in 1975 when they described a series of four women with acute visual disturbance and paracentral scotomas consistent with cuneiform macular damage [1].

The pathogenesis of AMN has yet to be fully elucidated, but some evidence points to the existence of deep ischemia of the retinal capillary plexus [2].

Optical coherence tomography angiography (OCTA) enables full visualization of retinal vascular flow, providing a key tool for assessing the extent of a vascular defect [3]. The most frequently documented association with AMN is viral infection. Other associations include oral contraception, high coffee consumption, vasoconstrictive drug intake, hypotension and, recently, vaccination [4].

We report a rare case of postpartum acute macular neuroretinopathy following ergotamine intake. We aim to highlight the importance of identifying this clinical entity in the postpartum context and to provide a credible hypothesis on the mechanism inherent in this disease on the basis of the OCTA findings.

We report the clinical presentation of a 27-year-old woman who presented with paracentral scotomas in the left eye immediately after a normal full-term delivery. She suffered from chronic hypotension with a blood pressure of approximately 85/60 mmHg. To prevent postpartum hemorrhage, the patient received a total dose of 200 micrograms of ergometrine administered intramuscularly (IM).

Corrected visual acuity was 20/20 in both eyes. Anterior segment examination showed no abnormalities. Fundus examination revealed reddish, well-delineated parafoveal defects in the left eye (Fig. 1A) and no abnormalities in the right eye.

Fig. (1). (A) left fundus photo showing flat, well-defined, reddish parafoveal lesions (black arrow), (B) red-free imaging showing dark petalloid perifoveal lesions(blue arrow), (C) Near-infrared (NIR) imaging reveals petal-shaped hyporeflective lesions (red arrow), (D) optical coherence tomography showing a well-defined reflectivity defect in the outer retinal layers (red arrow).

Fig. (2). Optical coherence tomography angiography (OCTA) showing flow void (red asterix) in the deep capillary plexus (B), outer retina (C) and choriocapillaris (D) that colocalize with the hyporeflectivity (red asterix) seen on near-infrared reflectance imaging (E).

In the red-free imaging, there were dark petalloid perifoveal lesions with the tips pointed toward the fovea (Fig. 1B). Near-infrared (NIR) imaging revealed two petal-shaped hyporeflective upper parafoveal lesions (Fig. 1C). SD-OCT revealed a thinned outer nuclear layer with hyperreflective of the outer retina and rupture of the ellipsoid zone, the outer limiting membrane, and the interdigitation zone (Fig. 1D). OCTA demonstrated superficial capillary plexus normal vascular flow (Fig. 2A), and a vascular flow void (red asterisk) in deep capillary plexus (B), outer retina (C) and choriocapillaris (D) matching the hyporeflectivity noted on near-infrared reflectance imaging (E). Optical coherence tomography angiography (OCTA) revealed normal vascular flow in the superficial capillary plexus (Fig. 2A) and a vascular flow void (red asterix) in the deep capillary plexus (B), outer retina (C) and choriocapillaris (D) that colocalize with the hyporeflectivity seen on NIR imaging (E). Acute macular neuroretinopathy was diagnosed in a post-partum patient.

The patient described a marked reduction in scotomas after three months of follow-up. On ocular examination, visual acuity was stable at 20/20 in both eyes, and fundus lesions had diminished (Fig. 3A). SD-OCT revealed recovery of the reflectivity damage in the outer retinal layers (Fig. 3B, red asterisk), and OCTA revealed attenuation of vascular flow vacuity (Fig. 3C, red asterisk).

Fig. (3). Three months' follow-up: (A) fundus lesions were attenuated, (B) OCT showing reflectivity defect restoration, (C) OCTA revealing attenuation of vascular flow vacuity.

Acute macular neuroretinopathy typically occurs in in young women with risk factors including migraine, oral contraceptives, ergotamine or ephedrine use, hypotension and viral infection [5]. Patients usually present with acute symptoms, such as paracentral scotomas, blurred or preserved vision and metamorphopsia [5]. The course of the disease varies from a few weeks to several months, with results ranging from total recovery of vision to persistent scotomas [6].

Multimodal imaging allowed the diagnosis of AMN in our patient presenting with paracentral scotomas in a postpartum context. There are only four published reports on cases of AMN occurring after the post-partum period, three of which were delivered by caesarean section and one by vaginal delivery [7-10] (Table 1). Two patients developed hypotension during caesarean section and received oral methylergometrin and etilephrine in one case [5] and ephedrine and epinephrine in the second case [10].

The patient suffered from chronic hypotension, with no evidence of an acute fall in blood pressure before the onset of symptoms. However, she received ergometrine, known to trigger acute ischemic damage and peripheral vessel constriction [8, 11]. Lupton et al. [12] demonstrated changes in retinal microvascularization during pregnancy, consisting of initial vessel dilation in the second trimester, followed by gradual vessel constriction for the rest of the pregnancy. We speculate that these coincident hemodynamic conditions during pregnancy may have exacerbated the ergotamine vasoconstrictive action on the choriocapillaris and retinal microvasculature, leading to ischemia at this level.

Diagnosis of AMN relies on multimodal imaging combining NIR imaging, SD-OCT with B-scan analysis and, more recently, optical coherence tomography angiography (OCTA) [13].

A typical corner-shaped defect on NIR imaging, associated with outer retinal layer defects on SD-OCT and non-perfusion in the deep capillary plexuses and choriocapillaris on OCTA, has been frequently documented in AMN [14].

AMN's pathogenesis is not fully clarified, but it has been suggested that deep retinal capillary plexus and choriocapillaris ischemia cause hypoxic retinal damage [15, 16]. OCTA can represent an invaluable tool in multimodal imaging in AMN, permitting visualization of retinal microvasculature perfusion at different levels. No previous reports on the use of A-OCT in AMN in post-partum settings were identified in our literature review.

Hypotension and ergotamine's vasoconstrictive properties may indeed have contributed to ischemic damage involving the deep capillary plexuses and choriocapillaris, as demonstrated by OCT-A and contributing to the development of AMN [17].

In a similar case reported by Vance et al., the authors suggested that methylergometrine-trine-induced vasoconstriction in the chorioretina leads to AMN in the postpartum period [6].

Acute macular neuroretinopathy is generally a self-limiting disease that does not necessitate treatment. As in our patient's case, resolution of fundus defects and outer retinal layer restoration on SD-OCT are common; however, paracentral scotoma may persist months or even years later [17].

Follow-up is based on the results of multimodal imaging and patient symptomatology. Multimodal imaging, including new diagnostic tools, such as OCTA, was described in post-partum AMN for the first time in this case report. OCTA assists not just in the diagnosis and monitoring of this rare disease but also in describing the retinal microvasculature damage observed in this condition, supporting the hypothesis of the ischemic effect of ergotamine in this report.

Retinal vascular occlusions may occur in the postpartum period, such as central retinal artery occlusion [18], AMN [7-10], central retinal vein occlusion [19], cilioretinal artery occlusion [19], and Purtscher’s-like retinopathy [20]. Pregnancy by itself can be a risk factor for retinal vascular thrombosis. Indeed, normal pregnancy is associated with a state of systemic hypercoagulability, which may continue into the post-partum period to prevent delivery hemorrhage [21].

In conclusion, in the case of post-partum AMN, a systemic workup is necessary to investigate a state of thrombophilia, which may be exacerbated by undiagnosed pre-existing underlying thrombotic disease, hypotension induced by post-partum hemorrhage or the use of vasoconstrictive drugs.

Ergometrine is commonly administered in obstetrics for the prevention of postpartum hemorrhage.

We describe here a further case of AMN, which occurred in a young woman in the postpartum setting following ergotamine intake. This event deserves serious consideration by healthcare professionals and must be seriously considered in patients requiring ergotamine, particularly those at additional risk of AMN.