Patients with migraine experience many symptoms other than headache. Some of these occur during headache, some occur before and some after the headache has stopped. A peculiar symptom is what is called aura. About a quarter of patients with migraine will experience the aura symptoms. Most commonly, aura occurs just before headache, but can also occur during the early part of headache or sometimes without the headache. These symptoms can involve changes in vision (visual aura), sensations (sensory aura) or strength (motor aura).
This is the most common and well-studied type of aura. Typically, patients will see a zig-zag line starting on one side which moves across in front of their eyes before fading away. The symptoms are quite alarming and patients often and understandably feel anxious and worried when they get them for the first time. Along with zig-zag lines, patients may also see sparkling or flashing lights or diamond-shaped small lights (positive symptoms).
The hallmark of migraine aura is that the symptoms change in shape, size and location. If the symptoms are stationery i.e. flashing small lights or spots, which do not change i.e. move or become big or small, they are unlikely to represent migraine aura.
The visual disturbance lasts for more than 5 minutes and not more than 60 minutes in a typical patient although some patients may have these symptoms lasting longer. Sometimes after the positive symptoms go away, there may be dark holes in the vision where patients are not able to see (scotoma).
This consists of either a feeling of tingling (i.e. pins and needles) or numbness (i.e. lack of sensation or ‘dead’ feeling). Again the feeling starts in one area of the body and travels slowly, patients are able to note the march of symptoms. For example, if the feeling starts in the hand, it will move up the arm and not involve the entire arm all at the same time.
Speech and language can also be affected causing ‘difficulty getting the right word out’ and slurring of words.
This genuine weakness on one side of the body is much rarer. Many patients with this type of aura have other members in the family who experience similar symptoms (called familial hemiplegic migraine) although it can also occur without a family history (sporadic hemiplegic migraine). Although feelings of numbness or apparent weakness (‘my arm felt dead and I had difficulty moving it’) are common, genuine weakness on one side suggestive of hemiplegic migraine is much less common.
What causes aura?
A gentleman called Lashley in the 1940’s was the first to carefully document his visual aura as it happened. After calculating the rate of progression of the visual aura, it was estimated that the corresponding ‘electrical disturbance’ in the back part of the brain (occipital cortex, where vision is represented) had to spread at the rate of around 3 mm/minute. When the occipital cortex of animals is stimulated either by a chemical preparation or mechanically, there is a wave of electrical change that spreads at the rate of around 3 mm/minute. There is also some indirect human evidence that such a change may be occurring in patients during aura, although the evidence is not robust. Drugs that are useful for preventing migraine with aura are able to stop this electrical change in experimental animals. Therefore, it is likely that the electrical change that is called cortical spreading depression (CSD) is the cause of migraine aura. The exact mechanisms for CSD are however not understood.
How do you treat migraine aura?
There is no treatment proven to be effective during the aura but fortunately, most aura symptoms last for a short period of time. You will know your limitations and should not carry out any activities that you feel may be dangerous whilst your senses are somewhat impaired.
If the aura symptoms are frequent and disturb your life significantly, there are several preventive medications that can be used to reduce the frequency and the duration of the aura attacks.
Migraine aura and stroke
It has been shown that young female patients with migraine aura have a slightly increased risk of having a stroke. This is a small risk but can increase further if there other risk factors are present such as smoking, high blood pressure, high cholesterol, and being over-weight. So, it is important that patients stop smoking, get their blood pressure and cholesterol checked and maintain a healthy lifestyle and body weight. Another thing that can increase the chances of stroke in these patients is the use of oestrogen. So, oestrogen (present in the combined contraceptive pill) should be avoided by young female patients with migraine aura. There are plenty of other hormonal options available for contraception.
By Farooq Maniyar, Consultant Neurologist.
This information is provided as a general guide only and is not a comprehensive overview of prescribing information. If you have any queries or concerns about your headaches or medications please discuss them with your GP or book an appointment to see a Headache Specialist at the National Migraine Centre.