Transient neurologic syndromes: A diagnostic approach

Symptoms should also correlate with a defined vascular territory:

• The middle cerebral artery is commonly involved; its blockage is associated with aphasia, weakness of the face and arm, and homonymous visual field impairment (loss of one-half of the visual fields in both eyes)
• Blockage in the posterior circulation generally causes symptoms localized to the brainstem, cerebellum, and occipital cortex. The symptoms are usually grouped together as the “5Ds”: dizziness, diplopia, dysarthria, dysphagia, and dystaxia/ataxia. Brainstem involvement classically produces “crossed” findings, with ipsilateral cranial findings and contralateral motor or sensory findings.
• Lacunar strokes involve the subcortical white matter and produce typical patterns including pure motor or sensory syndromes.

Loss of consciousness is rarely a symptom of TIA and should suggest another etiology.

The definition of TIA has evolved from an operational one, ie, symptoms lasting less than 24 hours, to a tissue-based one, ie, focal cerebral ischemia not associated with permanent cerebral infarction. ¹² Though imperfect, this pathophysiology should help reinforce the most common features of TIA, including a sudden onset of negative symptoms that are localized to a defined vascular territory. ^13,14

Migraine with aura

Migraine with aura is common in patients ages 25 to 55 who have a long-standing history of headache. The pathophysiologic mechanism of an aura is believed to be a disseminating wave of cortical depression, which is a self-propagating wave of neural depression and then activation. Ultimately, this leads to a cascade of inflammatory and pain signals, resulting in a headache.

This background helps explain the positive (superimposed) symptoms associated with the aura. Positive symptoms are produced by excessive neuronal discharges stimulating the visual (flashing lights, zigzag lines), sensory (paresthesias), or motor (limb movements) pathways.

Common symptoms associated with aura include visual disturbances such as scintillating scotoma (a blind spot), sensory changes such as tingling, or auditory disruption with tinnitus. Symptoms may evolve over the course of 5 to 20 minutes, first affecting vision and then other senses. In contrast, in a TIA, symptoms usually begin simultaneously and are confined to a vascular territory. ^7,15 Symptoms of an aura usually resolve within an hour, but there is evidence showing a substantial number of patients have an aura lasting much longer. ¹⁶ Focal weakness is uncommon during an aura but is reported in specific migraine conditions such as hemiplegic migraine and migraine with unilateral motor symptoms. The vast majority of patients experience other neurologic symptoms during this prodrome. ^17,18

The prodromal period (2 to 48 hours leading up to the onset of migraine) is a commonly overlooked feature of migraine. ¹⁹ Common symptoms during this time include fatigue, mood change, and gastrointestinal symptoms. ²⁰ One study demonstrated that patients generally had good intuition concerning these nonspecific prodromal symptoms and could predict the onset of migraine 72% of the time. ²¹

In addition, a myriad of possible triggers and exacerbating factors can be identified (and sometimes avoided) such as visual stimuli, weather changes, nitrates, sleep disturbances, menstruation, foods, and stressors. ²²

Although headache is often the cardinal manifestation of migraine, some patients experience aura without headache—acephalgic migraine. ²³ This can be a diagnostic challenge, especially in an older population with multiple vascular risk factors. New-onset acephalgic migraine may be a cause for concern but is not uncommon and is not associated with a significantly increased risk of stroke. ²⁴ Focusing on the character of the neurologic symptoms in regard to timing, progression, and resolution will help differentiate this disease from other transient neurologic syndromes. ²⁵