How to Spot Posterior TIA Presenting with Dizziness

August 6, 2024

Written by Shannon Markus

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Diagnosing patients with a posterior circulation TIA who are experiencing  isolated episodic dizziness can be challenging, especially when considering the difficulty in assessing individual symptoms and the small absolute number of these patients. The authors lay out a pragmatic approach for assessment and diagnosis, but the data to support a reliable clinical decision-making tool is weak.

Differential for dizzy got me in a tizzy… 😵‍💫
Dizziness is arguably EM’s most loathed complaint. Symptoms can be nebulous and challenging to describe with precision. Diagnosing ED patients with episodic dizziness requires a broad differential that includes posterior circulation TIAs (pcTIA). An estimated 70,000 ED patients/year ultimately have pcTIAs, with a higher risk of subsequent stroke, and starting prevention measures after identification will prevent some strokes. Admittedly, the number of missed pcTIA diagnoses is very low.

Diagnostic difficulties in patients with acute dizziness are common and result from underuse of the physical examination and overreliance on brain imaging. The authors based their recommendations on studies that evaluated rates of (1) pcTIA “misses”, (2) stroke after pcTIA, and (3) posterior stroke patients who retroactively recalled isolated episodic dizziness. The authors suggest familiarizing oneself with clinical variables that help to distinguish pcTIA from vestibular migraine (most common cause of episodic vestibular syndrome), BPPV, and orthostatic hypotension, and provide a table to simplify the differences. For example, vestibular migraine patients tend to be younger, female, fewer vascular risks, multiple previous attacks, and commonly have concurrent HA. pcTIA patients are generally older, male, more vascular risks, fewer previous attacks, and rarely have HA.

Their diagnostic algorithm suggests the following steps:

• Step 1: Determine whether the episodic vestibular syndrome is triggered through history-taking and bedside tests.
• Step 2: Think algorithmically. Consider using vascular risk calculators like ABCD2 to stratify patients at higher risk of CVA.
• Step 3: Become more familiar with vestibular migraine.

How will this change my practice?
A very small proportion of all-comer ED patients with isolated dizziness have true pcTIA, and as it is, there are not very many missed diagnoses. I’m not sure that their algorithmic approach will improve my ability to find the needle in the haystack, but may make me more confident in foregoing advanced imaging in patients whom I think have an alternative diagnosis, reducing exposure, time, and healthcare costs.

Source
Recognizing Posterior Circulation Transient Ischemic Attacks Presenting as Episodic Isolated Dizziness. Ann Emerg Med. 2024 May 23:S0196-0644(24)00214-2. doi: 10.1016/j.annemergmed.2024.04.006. Epub ahead of print. PMID: 38795083.