Aura · Grey Matter

An aura is a symptom the person notices at the start of an attack, before or instead of anything an observer can see, and it is the name used for two different events: the opening of a migraine attack and the first, still-aware part of a focal seizure.

Aura. An aura is a symptom the person notices at the start of an attack, before or instead of anything an observer can see, and it is the name used for two different events: the opening of a migraine attack and the first, still-aware part of a focal seizure.

The two share a word and little else. A migraine aura is produced by a slow wave of spreading depression, so it unfolds over minutes: by the international criteria each symptom spreads gradually over at least five minutes and lasts five to sixty, and the symptoms come one after another. More than 90 % of migraine auras are visual, a flickering zigzag or bright arc with a scotoma behind it; tingling that marches up a hand to the face and difficulty finding words are the sensory and language forms. An epileptic aura is a focal seizure that has not yet spread, so it is as fast as a seizure and its content is set by where it starts.

Epileptic auras name their place. Coloured circles lasting seconds point to the occipital lobe; a rising feeling in the stomach, déjà vu, fear, or a smell or taste point to the mesial temporal lobe; a tingle in one hand points to the sensory strip.

Duration and colour separate the visual ones. Migraine aura is gradual and often black and white with a blind patch; occipital seizures are brief, coloured and round, and can repeat many times a day.

An aura is information. In epilepsy it marks the focus and gives seconds to sit down; in migraine it is the visible side of an event in the cortex that the migraine card follows into the headache.

A migraine aura can occur without any headache, which is a recognised form of migraine in the classification.

The speed of an aura tells which wave made it.

Minutes of slow drift mean spreading depression; seconds of bright, local activity mean a seizure.

Questions: Is an epileptic aura a warning before the seizure, or the seizure itself? It is the seizure itself, at its start: a focal seizure with awareness kept, small enough to be felt and remembered and not yet large enough to show to an observer. Its content reveals where it begins, such as coloured lights in the occipital lobe, a rising feeling from the stomach or déjà vu in the mesial temporal lobe, and a tingle in one hand in the sensory strip. Sometimes it stays that size and ends; sometimes it spreads, awareness is lost, and it may become a convulsive seizure, so the aura is both the first sign and a guide to where the seizures start. How can coloured lights from an occipital seizure be told apart from a migraine aura? Speed and shape separate them best. Occipital seizures are produced by a fast discharge, so their lights appear within seconds, last seconds to a couple of minutes, are usually coloured and round, and can recur many times a day. A migraine aura is produced by spreading depression, which crosses the cortex at a few millimetres per minute, so by the international criteria it spreads over at least five minutes and lasts five to sixty, typically as a flickering black-and-white zigzag edge with a blind patch inside. The distinction is clinical, and overlapping cases are sorted out with an EEG and a neurologist. What counts as a migraine aura, and how long does it last? A migraine aura is a fully reversible neurological symptom (visual, sensory, speech or, rarely, motor) that develops gradually and is followed by or comes with the headache. By the international classification, at least one symptom spreads gradually over five minutes or more, each symptom lasts five to sixty minutes, at least one is on one side, and several may follow one another. More than 90 % of auras are visual, typically a flickering zigzag or bright arc that expands and leaves a blind patch, and an aura can also occur without any headache after it.