HINTS Examination for Diagnosing Central Causes of Acute Vestibular Syndrome

Dizziness and vertigo are common reasons for people to present for medical care and they often present in our chiropractic offices as well. When this symptomatology is acute and severe, do you know what to do?

A specific cause of dizziness and vertigo is called acute vestibular syndrome, which consists of symptoms such as severe vertigo, nausea, and vomiting, spontaneous nystagmus and postural instability/imbalance. Acute vestibular syndrome can occur from either peripheral causes such as vestibular neuronitis and Meniere’s syndrome, or from central causes such as cerebellar infarction and cerebellar hemorrhage. These clinical presentations bring significant challenges for clinicians as peripheral and central causes can present with similar symptoms. While most people have a benign etiology, it’s important to accurately identify central causes promptly due to its’ time sensitive nature which often requires hospital admission, further diagnostic tests, and immediate management. Therefore, there is a need to identify an accurate tool that can detect, as well as exclude central causes of acute vestibular syndrome.

The head impulse test measures the vestibulo-ocular reflex and is performed by having the person focus their eyes on a single central target while their head is rapidly rotated side to side in a horizontal direction. The interpretation of results can seem somewhat counterintuitive: A normal response consists of the person generating an equal and opposite eye movement such as their eyes staying stationary in space while their head moves (in a healthy person without acute vestibular syndrome). An abnormal response (in a healthy person) occurs when their eyes are unable to maintain fixation in one direction due to loss of vestibular afferent input, causing the person to develop a corrective gaze shift back to the center. In someone with acute vestibular syndrome, this sort of ‘catch-up’ saccade can be reassuring because it suggests a nerve (peripheral) problem, versus a brain (central) problem – these patients may demonstrate fixed eyes, or a blank stare during this test.

Nystagmus is often present in people with acute vestibular syndrome. When a peripheral etiology is present, nystagmus is predominately horizontal and beats only in a single direction. The nystagmus intensity will increase when the person looks in the direction of the nystagmus. An abnormal finding, which would suggest a central cause, includes vertical nystagmus, torsional nystagmus or nystagmus that changes in direction on eccentric gaze.

Skew deviation consists of a vertical misalignment of the eyes due to an imbalance of vestibular tone in the oculomotor system. This is assessed by performing the alternative cover test, whereby the clinician covers each eye in isolation assessing for a vertical correction of the eye position when they remove their hand. A vertical correction would be abnormal and suggestive of a central cause.

A HINTS examination is suggestive of a central cause of symptoms when there is a normal head impulse test (with fixed eyes or blank stare – remember, you want to see that corrective saccade!), direction changing nystagmus or a vertical correction on the test of skew. A clinician should consider a peripheral cause of symptoms when the HINTS examination shows an abnormal head impulse test, unilateral nystagmus and no evidence of vertical correction on the test of skew.

The HINTS Plus examination is an expansion of the HINTS examination which includes a fourth step that assesses for the presence of new hearing loss which is generally unilateral and on the same side as the abnormal head impulse test (i.e. the side opposite of the fast phase of the nystagmus). This is used for an inner ear or cochlear nucleus stroke and frequently assessed by the clinician rubbing their fingers together over the patient’s ear to identify a new asymmetry in the patient’s hearing (1, 2).

The gold standard imaging test for a cerebellar and bulbar infarction is MRI with diffuse weighted imaging. While a CT scan is often ordered, studies have demonstrated that the diagnostic accuracy of a CT scan is substantially lower than an MRI when assessing for an ischemic stroke (3). When considering the use of an MRI, it has reduced accuracy within the first 48 hours and studies have reported false negative rates of 5% to 12% among early MRIs compared to MRIs obtained later than 48 hours after symptom onset (4, 5).

The primary aim of this review is to assess the diagnostic accuracy of the HINTS and HINTS Plus examination for identifying a central etiology for acute vestibular syndrome. The secondary objectives of this review include assessing the diagnostic accuracy among the following subgroups which are provider type, time from symptom onset to presentation, reference standard, underlying etiology, study setting, provider level of training, provider specialty, and the individual diagnostic accuracy of each component of the examination.

RELATED E-SEMINAR:

I discuss the HINTS examination in detail the 8-hour E-Seminar “Chiropractic Checkup from the Neck Up” (which includes sections on dizziness and vertigo differential diagnosis and assessment, headaches, concussion, stroke & neck manipulation and more…) – get this E-Seminar here

RESEARCH REVIEW: HINTS Examination for Diagnosing Central Causes of Acute Vestibular Syndrome

This paper was published in the Cochrane Database of Systematic Reviews (2023)

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