Paracentral Acute Middle Maculopathy (PAMM) and Its Multiple Etiologies

Educational Objectives

The goal of this program is to improve diagnosis and treatment of ophthalmologic disorders. After hearing and assimilating this program, the clinician will be better able to:

1. Recognize expected pathophysiologic changes in the retina in a patient with paracentral acute middle maculopathy.

Summary

Description: paracentral acute middle maculopathy (PAMM) features perivascular white lesions (not cotton wool spots) in macula; lesions usually surround veins; optical coherence tomography (OCT) shows middle maculopathy; defect in inner nuclear layer (INL) source of whitening; over time, INL thins and opacity resolves; PAMM initially considered new variant of acute macular neuroretinopathy (AMN) but now recognized as separate entity; PAMM more common than AMN; PAMM may be associated with branch or central vein occlusion

Pathogenesis: retina experiences arterial inflow and venous outflow; watershed zone rich in oxygen; this zone between blood supply of inner retina and choroid, in photoreceptor zone; decrease in blood supply to inner retinal layer means choroidal flow must supply ischemic inner retina, thereby shifting watershed zone into middle retina; condition described mainly in patients with vein occlusion but may be seen in those with incomplete arterial inflow; mild arterial ischemia alone may be associated with PAMM

Case: 77-yr-old man presented with 3 days of central vision loss; condition associated with embolus and appeared to be branch retinal artery occlusion (BRAO); however, OCT showed sparing of ganglion cell layer and retinal nerve fiber layer, suggesting incomplete BRAO; embolus migrated peripherally after 6 wk; on OCT angiography, flow visible, so BRAO incomplete; condition improved as embolus migrated; case illustrates probable mechanism by which arterial ischemia leads to PAMM

Assessment with OCT: applying algorithm to images from OCT angiography removes projection artifact and hyperreflectivity, allowing observer to see distinct layers in 3 capillary networks; using this algorithm, speaker studied PAMM, AMN, and disorganization of retinal inner layers (DRIL); study hypothesized that affecting superficial capillary plexus (SCP) associated with DRIL, affecting middle capillary plexus (MCP) associated with PAMM, and affecting deep capillary plexus (DCP) associated with AMN; AMN characterized by obvious wedge-shaped defect and disruption of outer retina; patients may recover partially, but outer nuclear layer remains thin

Study findings: defects subtle, focal, and only visible on cross-sections; defect believed to be in DCP; involvement of choriocapillaris in PAMM has been theorized, but study did not corroborate this; in patients with central vein occlusion, classic lesions of PAMM follow veins, while arteries spared; MCP involved first, which prevents flow into DCP; reperfusion appeared to emanate from increased flow in arterioles; in some cases of PAMM, SCP also affected; in eyes with reperfusion, INL not thinned, suggesting that early reperfusion may prevent loss of vision

Comparison of disorders: DRIL — characterized by multilayered ischemia; AMN — single capillary disease of DCP; PAMM — more likely to involve MCP, but DCP may be affected; occasionally, with severe ischemia, all 3 layers affected; these disorders may be associated with undetected underlying vascular pathology

Readings

Chu S et al: Projection-resolved OCT angiography of microvascular changes in paracentral acute middle maculopathy and acute macular neuroretinopathy. Invest Ophthalmol Vis Sci 2018 Jun 1;59(7):2913-2922; Ghasemi Falavarjani K et al: En face optical coherence tomography analysis to assess the spectrum of perivenular ischemia and paracentral acute middle maculopathy in retinal vein occlusion. Am J Ophthalmol 2017 May;177:131-138; Khan MA et al: En face optical coherence tomography imaging of deep capillary plexus abnormalities in paracentral acute middle maculopathy. Ophthalmic Surg Lasers Imaging Retina 2015 Oct;46(9):972-5; McLeod D: Misery perfusion, diffusive oxygen shunting and interarterial watershed infarction underlie oxygenation-based hypoperfusion maculopathy. Am J Ophthalmol 2019 Mar 21 [Epub ahead of print]; Sarraf D et al: Paracentral acute middle maculopathy: a new variant of acute macular neuroretinopathy associated with retinal capillary ischemia. JAMA Ophthalmol 2013 Oct;131(10):1275-87.

Disclosures

For this program, the following has been disclosed: Dr. Fawzi reported nothing relevant to disclose. 

Acknowledgements

Dr. Fawzi spoke at the 12th Annual Retina Symposium, presented by the University of Illinois, Chicago, Eye and Ear Infirmary, and held April 5, 2019, in Chicago, IL. For information about CME conferences presented by the University of Illinois, Chicago, Eye and Ear Infirmary, please visit chicago.medicine.uic.edu. The Audio Digest Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0 CE contact hours.

Lecture ID:

OP572003

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.