Overview
Vertigo describes the sensation of movement of themselves or their surroundings when they are not, often described as ‘the room spinning’ or the patient ‘swaying’.
Dysfunction of the vestibular pathway leads to vertigo. Vertigo can be classified as peripheral or central depending on which part of the vestibular pathway is affected. It is essential to ascertain what type of vertigo is present, as it may be presenting feature of a serious underlying cause including stroke.
This is where the head impulse, nystagmus, and test of skew (HINTS) examination is useful.
Types
Peripheral vertigo occurs due to problems with the inner ear or vestibular system (semicircular canals, utricle, saccule, and vestibular nerve). Causes include:
- Benign paroxysmal positional vertigo (BPPV) – most common
- Ménière’s disease
- Vestibular neuronitis
- Labyrinthitis
Central vertigo occurs due to problems with the central nervous system (particularly the cerebellum, brainstem, and vestibular nuclei). Causes are generally more severe and include:
- Ischaemia or stroke affecting the cerebellum, brainstem, or vestibular nuclei
- Multiple sclerosis
- Tumours
- Some drugs (e.g. phenytoin)
Head Impulse
Overview
This tests the vestibulo-ocular reflex (VOR) which is the reflex that keeps our gaze focused on an object when we turn our heads. If you turn your head to the right while reading this text, your eyes move to the left so that you can keep reading this text clearly. Turning your head to one side increases the activity of the ipsilateral semicircular canal.
Method
- The patient’s eyes are fixed on the examiner’s nose and the patient’s head is turned gently from left to right
- The patient’s head is rapidly turned around 20 degrees to the left and right and back to the midpoint
Interpretation
If the VOR is intact, the patient’s eyes will remain on the examiner’s nose during the quick passive movements.
If the VOR is weakened, the eyes move with the head and then rapidly move back (‘saccade’) to the point of fixation (the examiner’s nose). This corrective saccade means a peripheral cause of vertigo is more likely (generally, VOR is unaffected in stroke).
Turning the head to the right activates the right VOR and vice versa. If the patient’s head is rapidly turned to the right and the patient requires a corrective saccade (a quick eye movement to bring the patient’s focus back on the target, the examiner’s nose), then the right VOR is affected and the pathology is in the right inner ear or vestibular system.
Nystagmus
Overview
Nystagmus describes involuntary, rhythmic, rapid, oscillatory, and jerky movements of the eyes.
The fast phase of nystagmus describes the corrective saccade (the corrective eye movements that bring the gaze back to the target). This is what is used to describe nystagmus:
- For example, in down-beating nystagmus, the fast phase is downwards
The slow phase is the pathological part of nystagmus. This is the slow drifting eye movement in a certain direction that opposes the fast phase.
- For example in down-beating nystagmus, the slow phase is upwards
Method
- The patient is asked to look straight ahead
- The patient is then asked to look left, right, up, and down
Peripheral nystagmus
Causes of peripheral (causes involving the inner ear/vestibular system) nystagmus:
- Are monodirectional (i.e. nystagmus only beats in one direction)
- Are unaffected by which way the patient is looking (e.g. right-beating nystagmus remains right-beating regardless of if the patient is looking up, down, left, or right).
- Obey Alexander’s law which states:
- Nystagmus is directed towards the healthy ear
- Nystagmus is greater when looking in the direction the eyes are beating:
- For example, in right-beating nystagmus, the nystagmus is easier to see when the patient looks right and less easy to see when they look to the left
Central nystagmus
Gaze-evoked nystagmus describes nystagmus when the patient moves their eyes from the central position and its fast phase (the direction it beats) depends on which way the patient is looking:
- Looking to the left causes left-beating nystagmus
- Looking to the right causes right-beating nystagmus
Gaze–evoked nystagmus is seen in central nystagmus (problems with the cerebellum, brainstem, or vestibular nuclei) and is not seen in peripheral nystagmus. This is also known as bidirectional nystagmus and is specific for stroke.
Test of Skew
Overview
Skew describes the vertical misalignment of the eyes due to vestibular dysfunction as a result of brainstem or cerebellar damage that is not due to oculomotor nerve or muscle problems. If a patient’s eye appears to be at a higher level than the other, there is skew deviation which can suggest a central cause of vertigo.
If one eye appears higher than the other, this is known as a hypertropic eye. If it appears lower than the other, it is known as a hypotropic eye.
Method
- The patient looks at the examiner’s nose and the examiner covers one eye with their hand
- The examiner quickly moves their hand to cover the other eye and during this, the examiner looks to see any vertical and/or diagonal corrective eye movements
Interpretation
If an eye moves vertically/diagonally to correct eye movements, then a central cause of vertigo is likely.
Summary
- Peripheral causes (e.g. BPPV) are likely if:
- Head impulse is positive
- Nystagmus is unidirectional and obeys Alexander’s law
- There is no skew deviation
- Central causes (e.g. stroke) are likely if:
- Head impulse is normal
- Bidirectional/gaze-evoked nystagmus is present
- There is skew deviation
