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Paracentral acute middle maculopathy (PAMM) is an optical coherence tomography (OCT) finding defined by the presence of a hyperreflective band at the level of the inner nuclear layer (INL), indicating INL infarct secondary to hypoperfusion of the deep vascular complex.
We report a novel observation of a ruptured retinal artery macroaneurysm (RAM) with secondary incomplete branch retinal artery occlusion (BRAO) that resulted in PAMM.
A 72-year-old female presented with a 3-month history of sudden-onset left paracentral scotoma (Fig. 1A). Her medical history included hypertension and hyperlipidemia. Visual acuity was 20/25 and 20/150 OD and OS, respectively. Anterior-segment examination and intraocular pressures were unremarkable.
A ruptured RAM was seen along a second-order artery at the inferotemporal arcade. A small area of deep retinal whitening along the distal branches of this artery also was observed (Fig. 1B).
Corresponding OCT showed a round superficial retinal hyperreflective lesion consistent with RAM (Fig. 2A) and a hyperreflective band involving the outer plexiform layer (OPL), INL, and inner plexiform layer (IPL) consistent with PAMM (Fig. 2B).
Confocal scanning laser ophthalmoscopy dynamic fluorescein angiogram demonstrated a ruptured and hemorrhagic RAM with significantly delayed distal filling of the artery, which represented an incomplete BRAO. This was accompanied by resultant PAMM in an area supplied by the tributary arterioles of the affected artery (Fig. 2C).
Oxygen consumption is highest at the metabolically active middle retinal layer. The inner and middle retinal layers are supplied collectively by the superficial capillary plexus in the ganglion cell layer, intermediate capillary plexus (ICP) in the INL-IPL boundary, and deep capillary plexus (DCP) in the INL-OPL boundary. Schraf et al.
Second, it receives arteriolar inflow solely from the ICP (the superficial and deep retinal layers), lacking major arterial supply. As such, it maintains a lower perfusion pressure and is susceptible to states of global insufficiency.
Infarction of the middle retinal layer, resulting in PAMM, may occur selectively because of the combined effects of decreased perfusion pressure, decreased oxygen saturation, and increased metabolic oxygen demands.
Our patient had hypertension, which predisposed her to developing RAM.
resulted in mechanical narrowing of the vessel lumen and severe flow limitation distally, leading to an incomplete BRAO. This was consistent with the fluorescein angiogram findings of delayed filling in the distal portion of the affected artery. Flow limitation resulted in decreased blood supply to the retinal capillary plexuses and further decreased perfusion pressure, thereby disrupting the delicately balanced ICP and DCP blood supply of the middle retinal layer for reasons discussed earlier.
Middle retinal layer infarction occurs most readily and presented as PAMM in our patient.
Although the association of BRAO with PAMM has been described previously, this case merits discussion because the association of RAM with PAMM is novel and has not yet been reported. Additionally, the clinical and imaging findings were consistent with and clearly elucidated the anatomy and physiology of the retinal capillary plexuses as well as the pathophysiology of PAMM.
Footnotes and Disclosure
Wei Kiong Ngo has received speaker fees from Allergan (Singapore), Bayer (Singapore), and Novartis (Singapore) and also received travel support from Allergan (Singapore). Eunice Jin Hui Goh has no financial interest to declare.
Paracentral acute middle maculopathy and the organization of the retinal capillary plexuses.