a vasculopathic palsy is a marker for atherosclerotic disease, daily aspirin is appropriate as prophylaxis for other ischemic events such as stroke and heart attack. Some patients experience a subsequent similar episode involving the same cranial nerve, another ocular motor nerve or a facial palsy. Even in the case of such recurrence, the prognosis for ultimate recovery is excellent.

Diagnosis: Vasculopathic cranial mononeuropathy

Tip: The diagnosis of a vasculopathic cranial nerve palsy is a clinical one. Ancillary testing should be reserved for patients with an atypical clinical course.

Episodic scintillating scotoma

Case: A 55-year-old teacher had experienced several episodes of transient binocular visual loss over

the past two years. She described “shimmering” vision that began close to fixation and spread out to the periphery over 20 minutes. Most of these episodes occurred in the right hemifield, but occasional attacks were on the left. There were no other focal deficits, altered consciousness or headache associated with the visual loss. She was generally in good health and taking no medications. She reported a remote history of “sick headaches” without visual disturbance that were usually associated with menses and remitted in her late twenties after her first pregnancy. Her neurologic examination was normal including visual fields full to confrontational testing.

Does this patient need neuro-imaging? An EEG? Other investigation?

The slow spread of the scintillations across the visual field described by this patient is considered

pathognomonic of migraine. The fact that her visual disturbance sometimes switches sides further rules out a structural lesion. In this case, no additional testing is needed.

Discussion: Migraine with or without visual aura is extremely common, with a lifetime prevalence of 12 to 33% in women and 4 to 22% in men. Many patients with migraine present to primary care physicians, others to ophthalmologists, neurologists or other healthcare providers. Not all patients with migraine require neuro-imaging or other ancillary testing and it is helpful for the clinician to have a set of guidelines for deciding when such work-up is needed.

The presence or absence of headache is not a useful criterion since migraine visual aura without headache is a common occurrence, termed acephalgic migraine or migraine equivalent in the older literature. Moreover, 20% of vertebrobasilar transient ischemic attacks and even occasional seizures are accompanied by headache. The temporal and spatial characteristics of the visual episode are much more helpful. As noted previously (see Chapter 1, Twinkling scotoma), migrainous visual phenomena are usually positive (i.e. seeing something that is not there rather than not seeing something that is there) and usually include a quality of motion (shimmering, sparkling or vibrating). These migrainous scintillations often start adjacent to fixation and spread to the periphery on one side over 20 minutes (Figure 11.4). This slow spread or “march” corresponds to the speed of the spreading cortical depression that underlies an attack and is generally considered to be pathognomonic for migraine. There are rare cases in which this characteristic pattern of scintillations has been associated with a structural lesion (specifically, an occipital arteriovenous malformation or tumor), and it is believed that in these individuals a mechanical stimulus has provoked an episode of migraine. A helpful tip-off in such rare cases is the fact that attacks occur exclusively in the same hemifield. About 20% of patients with migraine report their attacks as always being on the same side (termed

Figure 11.4 ]Migraine visual aura. Typical scintillating scotoma is shown at varying time intervals after onset. The “X” in each instance indicates the visual fixation point and the numbers represent minutes. (From K. S. Lashley, Arch Neurol Psychiatr, 46 (1941), 331–9, with permission.)

“side-locked” migraine), so this feature alone does not guarantee the presence of a structural lesion but the converse is very helpful: attacks that switch sides are not due to an underlying mass lesion.

Migraine attacks are frequently precipitated by an internal or external trigger, and eliciting this history can be helpful in diagnosis as well as treatment. Stress and hormonal change are the most common triggers. The actual migraine episode typically occurs not during the period of stress but in the letdown phase that follows. Hormonal triggers most often involve a decline in estrogen levels such as just prior to menses and during peri-menopause when estrogen secretion tends to be erratic. Other triggers include skipping meals, sleeping late, strong smells, bright lights, caffeine withdrawal and certain foods. In some cases, more than one trigger is required to precipitate an episode; for example, missing breakfast and coffee because one is running late for a morning appointment. In its fullfledged form the headache is severe and associated with nausea, vomiting and a heightened sensitivity to light and sound; however not all migraine attacks have these characteristics. Migraine headaches are usually relieved by sleep and often by triptan medications. In the vast majority of cases, the focal