Acute confusional migraine and transient global amnesia: variants of cognitive migraine?

Abstract

Reading Pacheva and Ivanov's account of acute confusional migraine (ACM) 1, a condition with which, as an adult neurologist, I was not familiar, a possible relationship with transient global amnesia (TGA) occurred to me. Although preserved conscious level is a sine qua non in suggested TGA diagnostic criteria 2, nevertheless there are distinct similarities between ACM and TGA: duration of attack, postparoxysmal amnesia, low recurrence rate, possible relationship with migraine (some authors envisage TGA as a migraine aura 3, and possible familial nature in some cases 4, not to mention the possible misdiagnosis or missed diagnosis of cases 5. In addition, TGA patients may appear perplexed, anxious and repeatedly ask the same questions during an attack in a manner, which may be described as ‘agitated’. The clinical similarities between ACM and TGA have suggested to others the possibility of a shared pathophysiology 6, 7. As modern neuroimaging modalities have thrown new light on the pathogenesis of TGA 8, it would be of interest to examine ACM patients with these techniques. For example, diffusion-weighted magnetic resonance imaging (DWI) has shown hyperacute and acute ischaemic changes in medial temporal lobe structures in some TGA patients 9, 10. Magnetic resonance spectroscopy (MRS) has been used to demonstrate a focal hippocampal lactate peak in some TGA patients, indicative of anaerobic glycolysis and hence local metabolic stress related to ischaemia 11. Cortical spreading depression, the mechanism thought to be the neurophysiological correlate of migraine with aura, may also play a role in TGA, in addition to ischaemia 9. Functional imaging with positron emission tomography (PET) has provided some evidence in support of this possibility 12. Is it possible that ACM and TGA, respectively, represent global and focal disturbances of brain perfusion, perhaps with cortical spreading depression, vulnerability being in some way related to brain maturity? If shared pathogenetic mechanisms were established, for example through studies using DWI, MRS and PET, then ACM and TGA might be classified together as variants of ‘cognitive migraine’. None.