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Transient neurologic syndromes: A diagnostic approach

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Release date: February 1, 2018
Expiration date: January 31, 2019
Estimated time of completion: 1 hour

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ABSTRACT

Clinicians are often confronted with patients who have transient neurologic symptoms lasting seconds to hours. In many of these patients, their symptoms have gone away or returned to baseline by the time of evaluation, making the diagnosis even more challenging. Elements such as correlation of symptoms with vascular territory, prodromes, triggers, motor symptoms, confusion, and sleep behavior can guide the diagnostic workup.

KEY POINTS

  • Transient ischemic attack, migraine aura, and partial seizures are common and often can be differentiated by their distinctive symptoms.
  • Episodes of confusion in a patient with diabetes raise the possibility of hypoglycemic encephalopathy; other possibilities include hyperventilation syndrome and transient global amnesia.
  • Daytime sleepiness in a young patient may be due to narcolepsy or parasomnias.


 

References

Many patients present to their primary care physicians, urgent care centers, and emergency rooms because of neurologic symptoms lasting seconds to hours. Their problems can be a cause for concern and a challenge to diagnose, as in many cases their symptoms have returned to baseline by the time of evaluation. Referral to a neurologist may not be practical for all of them, particularly given that a consultation may take a long time to obtain.

Understanding the causes of transient neurologic syndromes and their phenomenology may help the clinician diagnose, triage, and treat such conditions effectively.

Here, we outline several transient neurologic syndromes—transient ischemic attack (TIA), migraine with aura, partial seizures, hypoglycemic encephalopathy, hyperventilation syndrome, transient global amnesia, narcolepsy, parasomnias, and some rarer conditions— focusing on their diagnostic elements. Others, such as drug-induced transient neurologic syndromes, vertigo, and dizziness, have been well discussed elsewhere.1–3

THE BIG 3: TIA, MIGRAINE, SEIZURES

A 45-year-old woman with a history of tobacco use and headaches presents to the emergency department with a 4-month history of episodic numbness and tingling of her right arm and face. She reports a prodromal state of anxiety and irritability 24 to 48 hours before symptom onset.

The sensory symptoms begin on her face and gradually progress down the arm and eventually to her fingers. They fully resolve within 2 hours without sequelae. Family members have noted some “slurred speech” during the episodes, and the episodes are occasionally preceded by a unilateral, throbbing headache that improves with rest.

What are the possible causes of her symptoms?

Transient ischemic attack

If a patient reports transient neurologic symptoms and has vascular risk factors, TIA is often the default diagnostic consideration. The risk of stroke is 9.9% in the 2 days after a TIA, 13.4% at 30 days, and 17.3% at 90 days.4 Rapid recognition offers a crucial period to minimize the possibility of permanent impairment. Interventions include modifying risk factors (hypertension, diabetes, and smoking) and starting an antiplatelet drug, an anticoagulant drug, or both, and possibly a statin.

It can be difficult to determine if this workup needs to be completed in the inpatient or outpatient setting. There is no clear consensus, but the ultimate goal is timely evaluation (within 24 to 48 hours). The ABCD2 (Age, Blood pressure, Clinical features, Duration of symptoms, and Diabetes) risk factor calculator was developed to help triage patients, though it has limitations.5,6

One should assess a patient’s history of a possible TIA in a stepwise fashion. First, analyze the patient’s age and demographics for known vascular risk factors or central embolic sources (eg, atrial fibrillation). Then consider the symptoms. TIA symptoms have rapid onset, usually within seconds7; symptoms with a more gradual crescendo suggest a nonvascular cause.8 TIA manifestations should resolve within 1 hour, and most studies suggest symptom resolution within 10 minutes is specific for a TIA.9–11 TIA symptoms are negative neurologic phenomena that denote a loss of function, such as loss of vision, motor weakness, or sensory numbness.

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

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