Paracentral Acute Middle Maculopathy
SALIENT FEATURES
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) that indicates INL infarction caused by impaired perfusion of the deep vascular complex (ie, intermediate and deep retinal capillary plexus or ICP and DCP) (Figure 12.1).
Patients present with an acute-onset paracentral negative scotoma and typically experience a permanent visual defect.
PAMM can complicate a large number of retinal disorders. It is most often secondary to local retinal vascular disease and/or systemic disorders but can be idiopathic.
Local retinal vascular diseases that can cause PAMM include central retinal vein occlusion, central or branch retinal artery occlusion, diabetic retinopathy, hypertensive retinopathy, sickle cell retinopathy, Purtscher retinopathy, and retinal vasculitis.
Systemic disorders include migraines, medications (amphetamines, caffeine, vasopressors oral contraceptives), hypovolemia, orbital compression injury, and viral prodromes.
As such, detection of PAMM should prompt a search for local vascular or systemic risk factors.
On fundoscopy, PAMM lesions appear gray, smooth in consistency, and deeper within the retina compared to cotton wool spots (Figure 12.1).
FIGURE 12.1 Color fundus photography and spectral-domain optical coherence tomography (OCT) (SD-OCT) of a patient with combined cotton wool spot and paracentral acute middle maculopathy (PAMM) secondary to a branch retinal artery occlusion. A, Color fundus photograph shows a white ischemic lesion with evidence of inner and middle retinal infarction. The latter appears deeper, greyer, and smoother in consistency. B, OCT through the superior region of the lesion shows bandlike inner nuclear layer (INL) hyperreflectivity consistent with a middle retinal infarct or PAMM. C, OCT through the inferior region of the lesion shows evidence of inner retinal infarction. (Courtesy K. Bailey Freund MD).
As lesions are secondary to an ischemic insult, they are often unilateral but may be bilateral.
Management is targeted toward the identification and treatment of related vasculopathic and systemic risk factors.
OCT IMAGING
OCT serves as the mainstay of diagnosis.
Acute PAMM lesions appear as bandlike, hyperreflective lesions at the level of the INL in the parafovea. The acute lesions leave a legacy of
INL thinning or atrophy typical of tissue infarction, ie, old or chronic PAMM (Figure 12.2).
FIGURE 12.2 Spectral-domain optical coherence tomography (OCT) of a patient with paracentral acute middle maculopathy or PAMM. A, OCT at baseline shows two bands of inner nuclear layer (INL) hyperreflectivity consistent with an INL infarct or PAMM. B, At follow-up, a legacy of middle retinal atrophy corresponding to the baseline PAMM lesions is noted.1 These lesions may be referred to as old or chronic PAMM. (Reprinted with permission from Yu S, Pang CE, Gong Y, et al. The spectrum of superficial and deep capillary ischemia in retinal artery occlusion. Am J Ophthalmol. 2015;159(1):53-63.e2. doi:10.1016/j.ajo.2014.09.027.)
PAMM lesions can have a diffuse or skip pattern with cross-sectional OCT. With en-face OCT, the skip PAMM lesions typically display a precise perivenular colocalization (Figure 12.3).
PAMM is a manifestation of the retinal ischemic cascade due to the predominantly physiological vertical flow of blood from the superficial to the deep retinal capillary plexus (Figures 12.3 and 12.4).
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