PAMM on OCT: seen in a quarter with giant cell arteritis, none with NAION

Design

Retrospective observational study, two tertiary neuro-ophthalmology practices

Population

80 biopsy-proven giant cell arteritis and 179 NAION patients

Primary outcome

Prevalence of PAMM on OCT

Effect

28% in giant cell arteritis vs 0% in NAION (P < .001)

This retrospective study from two tertiary neuro-ophthalmology practices reviewed OCT in 80 patients with biopsy-proven giant cell arteritis — with or without visual symptoms — and 179 with non-arteritic anterior ischaemic optic neuropathy, looking for paracentral acute middle maculopathy (PAMM), a band of hyperreflectivity in the middle retina that marks deep capillary ischaemia.

PAMM was present in 28% of the arteritis group and in no one with NAION (P < .001). It was found in 29% of arteritis patients who had no visual symptoms at all, and was no less common in those already on steroids (29% vs 22%). It was not associated with presenting acuity or field loss.

The value is diagnostic. In an older patient with optic disc swelling and ischaemic optic neuropathy, PAMM on a routine macular OCT points towards arteritis and away from the non-arteritic form. Its absence does not exclude arteritis, since three-quarters of arteritis patients did not have it. Starting steroids before the scan does not seem to make it disappear.

• Look for PAMM on macular OCT in any older patient with anterior ischaemic optic neuropathy.
• Treat PAMM in that setting as a pointer to giant cell arteritis, prompting urgent inflammatory markers and biopsy or imaging.
• Do not use the absence of PAMM to exclude arteritis; most arteritis patients did not have it.
• Perform OCT even after steroids have started; PAMM persisted on treatment.
• Consider OCT in giant cell arteritis without visual symptoms, as subclinical retinal ischaemia was found.

Why it matters

A routine macular scan can add weight to the most time-critical diagnosis in neuro-ophthalmology.

Don't overread it

This was retrospective at two tertiary centres; the absence of PAMM in NAION needs confirming in other cohorts.

The statistics, in plain English

PAMM in 28% versus 0% means its presence was highly specific for arteritis in this cohort, but with low sensitivity — about 72 in 100 arteritis patients did not have it. The steroid comparison (OR 1.43, interval 0.41 to 4.94) is too imprecise to say steroids have no effect, only that PAMM was still commonly seen.

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