Sir,

We read with great interest the letter by Jamison and Gilmour,1 and wish to emphasise that patients with headache and cotton wool spots require appropriate investigation before using the diagnosis of exclusion ‘retinal vasospasm’, as the differential diagnosis is wide and has potential threat to sight or life. This includes ischaemic retinopathy (diabetes, hypertension, hypercoagulable states, embolic disease), inflammatory conditions (systemic lupus erythematosus, polyarteritis nodosa, giant cell arteritis), and more rarely infection (HIV, Bartonella, leptospirosis) and neoplasia (lymphoma, leukaemia, metastases).

The authors’ speculation regarding a link between migraine and retinal vasospasm is reminiscent of the occasionally encountered diagnosis ‘retinal migraine’. This condition, defined by the International Headache Society (IHS) as recurrent, transient monocular visual disturbance occurring in close temporal association with typical migraine headache,2 is controversial. A literature review by Hill et al3 showed that only a minority of reported cases meet the IHS diagnostic criteria. Even where they are met, this presentation still merits investigation. We have seen a 63-year-old gentleman with a 10-day history of generalised headaches, intermittent scintillating scotomata, and an isolated cotton wool spot on examination (Figure 1). Within 24 hours of presentation he developed a central retinal artery occlusion and, despite the absence of any systemic symptoms, a diagnosis of giant cell arteritis was later confirmed by biopsy. Ominously, retinal migraine was initially considered a likely diagnosis.

Figure 1
figure 1

Left fundus colour photograph from a 63-year-old patient presenting with headaches and scintillating scotomata, showing an isolated cotton wool spot (arrow). Giant cell arteritis was later confirmed by temporal artery biopsy.

Full size image

It is worth noting that the understanding of migraine pathophysiology has changed. Alterations in cortical blood flow, though associated with migraine, do not reliably explain the complex nature or time course of the symptoms experienced by migraineurs. Evidence to support the modelling of migraine as a pathological state of neuronal instability is growing.4 Cortical migraine and retinal vasospasm may therefore be pathologically distinct entities.5 One must also bear in mind that ‘migraine’ is a term widely used by the public and is the commonest neurological diagnosis. Therefore, when a history of migraine is elicited from a patient with cotton wool spots, it is important not to be falsely reassured by this finding as it may be purely incidental.