02 Nov Case Studies Issue: Migraine Aura Without Headache (Ophthalmic Migraine)
By Sheena K. Aurora, M.D.
Swedish Medical Center
A 60-year-old woman presented to the headache clinic with three episodes of visual symptoms. The first episode occurred after she had been on the computer for several hours. She described her symptoms as a bright semi-circle in her visual field on the right side of both eyes. She was still able to see, but there was a black spot around the bright zig-zag lines. The episode lasted for 30 minutes. She had two more episodes, which lasted 15 minutes each, and she became concerned because they came on within the same week. Her neurological examination was normal. She had a family history of migraine with aura and previously got headaches with her menstrual period, which fit the criteria for migraines.
This patient is probably having migraine aura without headache, a very uncommon condition that is sometimes referred to as ophthalmic migraine. Since she had never had aura before, an MRI of the brain was ordered and the results were normal. We proceeded to treat her for migraine aura without headache. We counseled the patient that the disorder was benign. If the migraine aura came on frequently and was disabling to her there were several daily medications that could prevent the migraine aura, such as magnesium and neuromodulators like valproate, gabapentin and topiramate. She chose to follow-up if the problem worsened.
SOLVING THE MYSTERY OF AURA
The migraine aura is a fascinating puzzle for migraine sufferers, physicians and scientists alike. The most common aura involves visual disturbances, such as seeing jagged lines with a bright edge or other bright spots or flashes, often followed by a partial loss of vision. Less commonly, auras can involve a slowly spreading sensation of tingling or numbness that, for example, passes up one arm to the face. Speech disturbances, and weakness or loss of coordination can also occur with aura, though these are rare. Some people, especially children, have “Alice-in-Wonderland” hallucinations in which objects shrink or expand in size, or otherwise change their shape and proportions. None of these auras is dangerous, provided a careful medical exam has ruled out underlying causes. Until very recently, we could only speculate about the origin of aura. Early theories proposed that the visual aura and the neurological symptoms that are sometimes present (such as tingling or numbness) might be due to a lack of blood supply to the brain.
In 1940, Professor Lashley, a prominent researcher who also suffered from migraines, timed his own aura and the progression of the symptoms. He described the aura as a slow march forward across the surface of the brain. The timing of this march was similar to a phenomenon known to occur in the brains of animals in experiments that are thought to mimic the effects of migraine triggers. This phenomenon was very difficult to prove, however, because tools to detect changes in human brain activity were not readily available.
Perhaps the most convincing demonstration that this slow march of altered brain activity occurred in humans came from Drs. Barkley and Tepley at Henry Ford Hospital in Detroit, who were able to capture a migraine aura in a fellow neurologist in 1988. They used a device called a magnetoencephalogram, which measures the collective electrical activity of brain cells. Spreading wave-like events were detected during the aura. Capturing an aura such as this was exceptional. Therefore, Drs. Bowyer, Welch and I developed a technique to trigger migraine experimentally, using a visual stimulus, so we could study the very early events of migraine aura in a series of cases. We also used a newer device, called a whole-head magnetoencephalogram, which could capture electrical activity throughout the head. We were now able to precisely measure the nature of the waves and were again able to demonstrate the presence of spreading waves of activity in migraine. These waves started from the visual cortex, the part of the brain that processes visual signals. Using a different technique involving functional MRI, Drs. Cao, Welch and I also saw these spreading events and we measured blood flow during the aura. These functional MRI studies clearly demonstrated that blood flow never dropped to levels that would produce oxygen starvation (ischemia) in the brain. There was, then, no basis for the theory that migraine aura is like a stroke. Migraine aura is a benign entity and is the result of electrical phenomena that occur in the brains of individuals who are susceptible to migraine.