PAMM on OCT appeared in 28% of giant cell arteritis and none of NAION

Design

Retrospective observational study at two tertiary practices

Population

80 patients with biopsy-proven giant cell arteritis and 179 with NAION

Primary outcome

Prevalence of paracentral acute middle maculopathy on OCT

Effect

28% in arteritis vs 0% in NAION (p<0.001)

This retrospective study from two neuro-ophthalmology practices reviewed OCT in 80 patients with biopsy-proven giant cell arteritis and 179 with non-arteritic anterior ischaemic optic neuropathy, looking for paracentral acute middle maculopathy, a band of ischaemia in the middle retinal layers.

PAMM was present in 28% of the arteritis group and in no NAION patients. In arteritis, it was found in 33% with persistent visual symptoms, 8% with transient symptoms and 29% with no visual symptoms at all. Steroid treatment before the scan did not make it disappear (29% vs 22%). PAMM was not associated with acuity or field loss.

In a patient with optic disc swelling and suspected ischaemic optic neuropathy, finding PAMM on OCT points towards arteritis. Its absence does not exclude it, since most arteritis patients did not have PAMM.

• Look for paracentral acute middle maculopathy on macular OCT in suspected arteritic ischaemic optic neuropathy.
• Treat PAMM in an older patient with disc swelling as supporting giant cell arteritis.
• Do not use absent PAMM to exclude arteritis; most patients with it did not have PAMM.
• Continue to start steroids promptly on clinical suspicion; PAMM persisted after treatment began, so scanning need not delay it.

Why it matters

Distinguishing arteritic from non-arteritic ischaemic optic neuropathy quickly decides whether the other eye is at risk.

Don't overread it

This is a retrospective series from specialist practices; specificity in broader settings may be lower.

The statistics, in plain English

28% versus 0% means PAMM was fairly specific for arteritis in this sample but not sensitive: about seven in ten arteritis patients lacked it. The steroid comparison (OR 1.43, CI 0.41 to 4.94) is too imprecise to conclude much beyond 'it did not disappear'.

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