Introduction
Vertigo and/or dizziness is a common presentation to the emergency department (ED) accounting for approximately 3%–4% of all presentations.1 The spectrum of potential causes is broad and may include vestibular, neurological, cardiovascular or other systemic disorders. The acute vestibular syndrome (AVS) is more narrowly defined as acute dizziness or vertigo, associated with nystagmus, nausea/vomiting and gait ataxia lasting at least 24 hours.2 The most common cause of AVS is vestibular neuritis (VN), a benign diagnosis in comparison to the less common and more serious differential of posterior circulation stroke (PCS), which accounts for approximately 3%–5% of dizziness presentations to the ED.1
PCS is commonly misdiagnosed in the ED as the signs and symptoms may be subtle3 4 and MRI can miss 20%–50% of posterior fossa infarctions within 48 hours of symptom onset.5 Several techniques have been described to improve diagnosis of AVS, most notably the bedside head impulse test (b-HIT) and the Head Impulse, Nystagmus and Test of Skew (HINTS) examnation. The HIT is a simple clinical manoeuvre performed at the bedside to test the function of the horizontal semicircular canals.6 The HINTS examination has demonstrated greater sensitivity than early MRI for diagnosis of PCS.7
While the b-HIT and HINTS examinations allow for accurate diagnosis of PCS when performed by experts, their routine use in clinical practice may not be as reliable.8 9 The development of the video HIT (v-HIT)10 has allowed accurate and quantifiable assessment of the vestibulo-ocular reflex (VOR) in all six semicircular canals. V-HIT can be performed using portable and relatively inexpensive equipment at the bedside. There is increasing evidence to support the use of v-HIT alongside expert clinical assessment for diagnosis of vestibular disorders in the ED.11 There are also ongoing clinical trials12 investigating the use of v-HIT in the acute clinical setting.
V-HIT measurement of VOR gain, refixation saccade prevalence and amplitude are reliable discriminators of VN from PCS.13 An abnormal v-HIT test defined by the presence of reduced VOR gain and catchup saccades, provides objective evidence of unilateral peripheral vestibular dysfunction. This is most commonly caused by VN. Unilateral vestibular dysfunction is rare in PCS, however, isolated infarcts in the vestibular nucleus or the anterior inferior cerebellar (AICA) and/or labyrinthine artery, may demonstrate unilateral vestibular dysfunction on both b-HIT and v-HIT testing.14 The HINTS, and ‘HINTS plus’ (HINTS+) assessment, where acute hearing loss is also considered, is designed to reduce the likelihood of falsely excluding a PCS when the b-HIT is abnormal. Skew deviation is more common with a pontine or medullary infarct than VN and infarction of the cochlear nerve from an AICA stroke is associated with acute hearing loss.
In this prospective observational study, we examined consecutive AVS patients referred by ED physicians. A b-HIT and HINTs were performed by senior neurology trainees and v-HIT by audiologists. We examined the accuracy of b-HIT vs HINTS vs v-HIT in excluding a diagnosis of PCS in patients with AVS. MRI brain was performed >48 hours after symptom onset in all patients and used as the gold standard for stroke diagnosis. Our hypothesis was that v-HIT is more accurate than b-HIT and HINTS examination performed by non-expert clinicians for diagnosis of VN in a real-world application.