Rochester, NY—Differentiating between migraine and transient ischemic attack at first may appear daunting, but a careful history-taking with attention to the details of the particular attack should help sort things out.
"One would think that differentiating between migraine and transient ischemic attack [TIA] would be easy, because it is commonly thought that migraine must be associated with a headache. However, that is not always the case," said Deborah I. Friedman, MD.
"The aura of migraine, including the neurologic symptoms that can mimic the TIA, can either precede a headache, as in classic migraine, occur during a headache, or occur without a headache (acephalic migraine or isolated migraine aura), the last of which is the problem," she said. "Afferent and efferent manifestations of migraine can mimic TIA. Those are the events that are stressful for both the patient and the ophthalmologist."
Positive visual phenomena are the most frequent companions of migraine and may occur at any age. Symptoms vary in length from momentary to 1 hour, are bilateral or unilateral, and are present even when the patient's eyes are closed. The descriptions of the phenomena vary as well, including heat waves rising from the pavement, sparkles, visual distortion, a flashing light, a kaleidoscopic effect, visual shimmering, zigzags in the visual field, or silver-gray or multicolored fortification spectra, which resemble a medieval fortress.
"The fortification spectra, with a build-up of and spread of the scintillating scotoma across the visual field of both eyes, are pathognomonic of migraine," Dr. Friedman said. "Ophthalmologists can feel comfortable that the patient is probably not having a TIA."
The monocular negative visual experience of migraine, sometimes referred to as ocular or retinal migraine, can also be confused with TIA, she pointed out. Retinal migraine, which can also be a momentary event or last hours, is characterized by a unilateral curtain-like effect over the vision, a unilateral gray-out of vision, or unilateral tunnel vision; positive visual phenomena may also occur. Narrowing of the retinal vein occurs during an ocular migraine.
The terms "ocular migraine" and "ophthalmic migraine" are sometimes used incorrectly to describe a binocular experience that does not originate in the eye but rather from the cerebral cortex. Dr. Friedman emphasized the importance of obtaining a good patient history to determine the origin of the symptoms.
"Ask the patient to describe the vision with both eyes open because you want to make certain that he or she is describing a homonymous hemianopia rather than unilateral visual loss," she said.
Homonymous hemianopia can occur in both migraine and TIA. When occurring during a migraine, homonymous hemianopia develops as rapidly as in a stroke, can occur with or without positive visual symptoms, lasts 10 to 60 minutes, and may occur as an isolated symptom. During a stroke, the homonymous hemianopia often starts simultaneously with other neurologic symptoms such as weakness or numbness on the same side as the hemianopia, or with a speech disturbance, she pointed out.
Other migrainous experiences can cause the vision to appear tilted and distorted, and objects can appear closer or farther away than they should or too small or too big. Objects can appear to move faster or slower toward or away from the patient, and patients can also have vision that resembles cracked glass.
The visual fields can be constricted in both migraine and TIA, according to Dr. Friedman. In migraine, the constriction usually develops gradually or over minutes and may progress to a blackout or whiteout of vision.
"This implies bilateral occipital involvement," she explained.