HINTS Exam (Head-Impulse / Nystagmus / Test-of-Skew)

Introduction

The HINTS exam consists of three physical examination techniques designed to assist the clinician in determining if dizziness or vertigo is of central or peripheral etiology. 

The HINTS exam is only used on a subset of the patients who present with all of the following (An asymptomatic patient can result in false negatives): 

• Acute Vestibular Syndrome (AVS): vertigo, nystagmus, nausea/vomiting, head-motion intolerance, unsteady gait.

• nystagmus at rest or with lateral gaze (active on presentation)

• A normal full neurological exam. 
  

Problem

• Determining whether Acute Vestibular Syndrome (AVS) or complaints such as "dizziness" is of peripheral (benign conditions) or central nervous system lesions (like strokes) is critical, time sensitive and often challenging. Focal neurological deficits that are often associated with central causes can be inconspicuous.

  • While most vertebrobasilar strokes are also accompanied by other signs (such as diplopia, dysarthria, dysphagia, motor and sensory deficits) a proportion of cerebellar strokes present only with vertigo and subtle incoordination on examination.

Components 

• Taking a detailed history (onset, tempo, prior episodes, associated symptoms and relevant risk factors) is the first step in determining the cause.

• The HINTS examination (Head Impulse - Nystagmus - Test of Skew) is a useful tool in detecting acute, time-sensitive, central causes of vertigo, including posterior circulation strokes like lateral medullary syndrome (Kattah et al, 2009).  

  • HINTS is comprised of three diagnostic tests: 

    • Head impulse test

    • Evaluation of nystagmus

    • A test of skew. 

• A positive HINTS exam has been reported to have a high sensitivity (96-100%) and specificity (96-98%)for the presence of a central cause of vertigo.

• HINTS exam was more sensitive than an MRI in the first 24 hours.

A single central finding on any of the 3 components "rules-in" a posterior circulation stroke and further testing and treatment is indicated.

*Nystagmus:

•  Interpretation: The direction of the saccadic eye movement is important. 

  • Unidirectional nystagmus is reassuring and more likely to be of peripheral origin. 

  • When nystagmus changes direction or is vertical, it is much more likely to be associated with central pathologies. 

  • Bidirectional nystagmus, in particular, is highly specific for stroke. In this case, the saccadic movement beats in the direction that the patient is looking, then changes direction with their gaze (gaze-evoked nystagmus).

Kattah JC, Talkad AV, Wang DZ, Hsieh YH, Newman-Toker DE. HINTS to diagnose stroke in the acute vestibular syndrome: three-step bedside oculomotor examination more sensitive than early MRI diffusion-weighted imaging. Stroke. 2009 Nov;40(11):3504-10.