Accuracy of Neuroimaging for Dizziness – It’s Not Pretty

September 21, 2022

Written by Gabby Leonard

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We cannot rely on neuroimaging (CT, CTA, MRI or MRA) alone to effectively rule out stroke in patients presenting to the ED with acute dizziness or vertigo.

Why does this matter?
Dizziness comprises roughly 4 million annual ED visits, with 40% of these patients receiving some type of neuroimaging. We’ve covered how to not miss posterior stroke before. Also, evidence shows neuroimaging alone is not reliable to rule out central causes for vertiginous symptoms in the acute setting.

You spin my head right round, right round
This systematic review looked at patients in the ED who presented with acute (<2 weeks) symptoms of dizziness to determine the sensitivity and specificity of neuroimaging in distinguishing stroke from peripheral causes. MRI was used as reference standard for diagnosis in addition to clinical diagnosis and final diagnosis at hospital discharge.

The numbers speak for themselves:

Type of Neuroimaging	Number of Studies/Patients	Sensitivity	Specificity
MRI	5 studies 943 patients	79.8% (95% CI 71.4%-86.2%)	98.8% (95% CI, 96.2%-100%)
MRA	1 study 24 patients	60.0% (95% CI 26.2%-87.8%)	92.9% (95% CI 66.1%-99.8%)
Ultrasound	3 patients 258 patients	30%-53.6%	94.9% to 100%
Non-Contrast CT	6 studies 771 patients	28.5% (95% CI, 14.4%-48.5%)	98.9% (95% CI, 93.4%-99.8%)
CTA	1 study 153 patients	14.3% (95% CI 1.8% – 42.8)	97.7% (95% CI 93.8% – 99.6%)

Important Takeaways:

1. Non-contrast head CT is obtained in 92% of patients who get neuroimaging for dizziness and has low sensitivity but still beats CTA. CT alone may miss a considerable number of acute ischemic strokes early after symptoms begin.
2. MRI obtained <48 hours after symptom onset is only 80% sensitive for posterior circulation strokes and is costly and difficult to obtain.

It seems we can’t rely solely on neuroimaging to rule out a central cause of vertigo. We must elicit a thorough history including timing and triggers of symptoms in addition to focused physical exam. Consider HINTS exam (head impulse, nystagmus, test of skew) when patients are symptomatic, but beware the limits of HINTS as well.

Editor’s note: So, what should we do? 1) If imaging is positive, easy – admit. 2) If you can do HINTS, and it’s positive but imaging is negative, still admit. 3) If you can’t do HINTS, imaging is negative for stroke, but you have other concerns on history or exam (advanced age, can’t walk, can’t take PO, fall risk, whatever), admit. In short, any worrisome dizzy person – admit. ~Clay Smith

Source
Diagnostic accuracy of neuroimaging in emergency department patients with acute vertigo or dizziness: A systematic review and meta-analysis for the guidelines for reasonable and appropriate care in the emergency department. Acad Emerg Med. 2022 Jul 25. doi: 10.1111/acem.14561. Online ahead of print.