• Vestibular neuronitis often affects previously well, young or middle-aged adults, but can affect anyone.
• Enquire about symptoms indicative of vestibular neuronitis.
• Vertigo occurs spontaneously, may develop on waking, or may develop over the course of the day. Acute symptoms usually settle in a few days because vestibular compensation occurs.
• Nausea and vomiting occur, and balance may be affected. Gait apraxia is not a prominent feature.
• Hearing loss and tinnitus are not features of vestibular neuronitis (but may be present in labyrinthitis).
• There are no focal neurological symptoms.
• Look for signs of vestibular neuronitis.
• Nystagmus is present and is usually fine horizontal but may be mixed horizontal-torsional with the fast phase away from the affected ear. It always beats in the same direction, even if the head is rotated, and is reduced when the vision is fixed on a point.
• The head impulse test may be positive (but is less reliable than nystagmus as an examination finding, as it may also be positive for other peripheral causes of vertigo and so cannot be used to differentiate between them).

• Use caution if the person has neck pathology, as the head impulse test involves rapid repositioning of the head [Kuo et al, 2008b]. Always start by asking the person to rotate their neck themselves to assess for any limitation of neck movement. If in doubt about the safety of the manoeuvre, seek specialist advice or refer the person to a balance specialist.
• To carry out the head impulse test [Macleod and McAuley, 2008]:
• Advise the person to sit upright and to fix their gaze on the examiner.
• Then rapidly turn the head 20 degrees to one side and watch the eyes for corrective abnormal movements (saccades).
• Repeat several times to the same or opposite side, randomly and unpredictably, until satisfied as to the consistent presence or absence of the corrective saccade.
• A corrective saccade represents a positive test and implies moderate to severe loss of function of the horizontal semi-circular canal on the side to which the test is positive.
• Video illustrations of performing the head impulse test and demonstrating corrective saccades are available at the Imperial College London Faculty of Medicine website.

This information is based on expert opinion in review articles [Hanley et al, 2001; Baloh, 2003; Hain and Uddin, 2003; Macleod and McAuley, 2008].

• Other causes of vertigo include:
• Benign paroxysmal positional vertigo. For more information, see the CKS topic on Benign paroxysmal positional vertigo.
• Labyrinthitis (similar features to vestibular neuronitis, but also involves hearing loss).
• Meniere's disease. For more information, see the CKS topic on Meniere's disease.
• Central causes (for example migraine, stroke, transient ischaemic attack, cerebellar tumour, acoustic neuroma, and multiple sclerosis).
• For more information on differentiating between these conditions, see the CKS topic on Vertigo.

This information is based on expert opinion in a review article [Nadol, 1995]. Further sources of information are discussed in the CKS topic on Vertigo.