Article
Transient ischemic attack: Omen and opportunity
A transient ischemic attack (TIA) is often the precursor of stroke. As such, every TIA deserves to be taken seriously.
A 35-year-old woman with a history of depression, anxiety, and poorly controlled type 1 diabetes presents to the clinic after several weeks of episodes of confusion, usually accompanied by paresthesias in both hands, dizziness, and palpitations. In each episode, soon after the symptoms began, she had painful cramps in her hand. The symptoms fully resolved within 10 minutes without sequelae.
Questioned further, the patient describes the confusion as a “mental haze” but denies frank disorientation. She has not kept a log of her blood sugar levels but has not noticed a temporal relationship with regard to her meals or insulin injections.
What are the possible causes of these episodes?
Hypoglycemic encephalopathy
Hypoglycemia is common in most people with diabetes, who have been reported to suffer from 62 to 320 severe hypoglycemic episodes in their lifetime. 33,34 The neurologic consequences can be devastating in these severe cases.
During mild to moderate drops in the glucose level, generalized symptoms stem from sympathetic activation. These include generalized anxiety, tremor, palpitations, and sweating. Focal symptoms such as unilateral weakness have also been reported. 35,36
Unfortunately, people with long-standing diabetes have a blunted response to epinephrine that reduces their sensitivity to hypoglycemia, placing them at high risk of permanent neurologic damage. This can lead to seizures and coma, as the hypoglycemia has a greater effect on cortical and subcortical structures (highly metabolic areas) than on the brainstem. Thus, respiratory and cardiovascular function is maintained but cerebral function is abnormal. If this state is prolonged, brain death can occur. 37,38
Hyperventilation syndrome
Hyperventilation syndrome is not well characterized. Most think of it as synonymous with an underlying psychopathology, but there is evidence to suggest it can occur without underlying anxiety.
There is no clear mechanism, but it is hypothesized that diminished carbon dioxide levels lead to cerebral vasoconstriction. This may lead to reduced cerebral blood flow, causing dizziness, lightheadedness, or vertigo. 39 Appendicular symptoms including paresthesias, carpopedal spasm, or tetany have been core features since the syndrome was first described in the early 1900s. 40
Though the disorder has rather nonspecific features, it can be easily reproduced in the clinical setting by asking the patient to breathe deeply and rapidly. This can help confirm the underlying diagnosis and also reassure the patient that the underlying pathology is not life-threatening and that he or she has some control over the disease.
Transient global amnesia
Transient global amnesia usually strikes older patients (50 to 70 years old) in the setting of an acute physical or emotional stressor. There is also a correlation between transient global amnesia and migraine, with studies showing migraineurs are at higher risk than the general population. 41 Despite common clinical concerns, there is no relationship between transient global amnesia and stroke. 42
Transient global amnesia is defined by acute transient anterograde amnesia (coding of new memories). To try to reorient themselves, patients will repeatedly ask questions such as “What day is it?” or “Why are we here?” Retrograde memories, especially long-standing ones, are usually well preserved. The patient’s cognition is otherwise intact, and there are no other focal neurologic symptoms. The event usually lasts 2 to 24 hours and resolves without sequelae. 43,44 Afterward, patients remember the event only poorly, which supports the notion that they cannot code new memories.