What is the diagnosis and explanation of neuritis to a patient and what is the HINTS (Head Impulse Test, Nystagmus, Test of Skew) exam?

Diagnosis of Neuritis and HINTS Examination

Vestibular neuritis is diagnosed through characteristic clinical features including acute-onset rotatory vertigo lasting more than 24 hours, horizontal spontaneous nystagmus toward the unaffected ear, and absence of cochlear or other neurological symptoms, with HINTS examination being crucial to differentiate it from central causes. 1, 2

Diagnosis of Vestibular Neuritis

Key Diagnostic Features

• Abrupt onset of true-whirling vertigo lasting more than 24 hours
• Horizontal spontaneous nystagmus (with rotational component) toward unaffected ear
• Pathologic head-impulse test toward affected ear
• Deviation of subjective visual vertical toward affected ear
• Postural imbalance with falls toward affected ear
• Nausea and vomiting worsened by head movement
• Absence of cochlear symptoms (in most cases) and other neurological symptoms 2, 3

Diagnostic Tests

1. Head Impulse Test: Shows ipsilateral deficit of vestibuloocular reflex
2. Caloric Testing: Reveals reduced or absent response on affected side
3. Vestibular-Evoked Myogenic Potential (VEMP): May be abnormal in affected ear
4. Neuroimaging: Not routinely needed if HINTS examination suggests peripheral cause 1, 4

Explaining Neuritis to Patients

When explaining vestibular neuritis to patients, include:

• Simple Definition: "Vestibular neuritis is inflammation of the inner ear balance nerve, likely caused by a viral infection."
• Cause: "It's most likely caused by a viral infection affecting your balance nerve, similar to how a cold virus might affect other nerves."
• Expected Course: "The severe spinning sensation typically improves within days, but complete recovery may take weeks to months."
• Recovery Process: "Your brain will gradually compensate for the damaged balance system through a process called central compensation."
• Treatment: "Treatment includes medications for symptoms, possibly steroids to reduce inflammation, and vestibular rehabilitation exercises to help your brain adapt faster."
• Prognosis: "Most people recover well, though some may have lingering symptoms with quick head movements."

HINTS Examination

HINTS stands for Head Impulse test, Nystagmus, Test of Skew. It's a powerful bedside examination to differentiate between peripheral causes (like vestibular neuritis) and central causes (like stroke) of vertigo.

Components of HINTS Examination:

1. Head Impulse Test (HIT):

   • Technique: Patient fixes gaze on examiner's nose while examiner quickly turns patient's head 10-20° horizontally
   • Peripheral pattern: Corrective saccade (eyes move off target then back) when head is turned toward affected ear
   • Central pattern: Normal VOR (eyes stay fixed on target) despite acute vertigo 1, 5

2. Nystagmus Evaluation:

   • Technique: Observe for spontaneous and gaze-evoked nystagmus
   • Peripheral pattern: Unidirectional, horizontal-torsional nystagmus that decreases with fixation
   • Central pattern: Direction-changing nystagmus, purely vertical/torsional nystagmus, or nystagmus unaffected by fixation 5

3. Test of Skew:

   • Technique: Alternate cover test looking for vertical ocular misalignment
   • Peripheral pattern: No vertical skew
   • Central pattern: Vertical skew deviation present 4

Clinical Significance of HINTS

• When properly performed, HINTS has higher sensitivity for stroke detection than early MRI (100% versus 46%) 1
• A peripheral pattern on HINTS ("INFARCT = Impulse Normal, Fast-phase Alternating, Refixation on Cover Test") strongly suggests vestibular neuritis
• A central pattern on HINTS ("HINTS = Head Impulse Normal, Test of Skew present") strongly suggests stroke 1, 5

Important Clinical Considerations

• Vestibular neuritis is the third most common cause of peripheral vestibular vertigo with an annual incidence of 3.5 per 100,000 population 2
• Up to 75-80% of patients with acute vestibular syndrome related to stroke have no associated focal neurologic deficits, making HINTS examination crucial 1
• Skew deviation may be associated with vestibular neuronitis but is more commonly seen with central lesions 4
• Recovery occurs through a combination of peripheral restoration (improved by early corticosteroid treatment), sensory substitution, and central compensation 2

Treatment Approach

1. Symptomatic therapy: Vestibular suppressants and antiemetics for acute symptoms
2. Specific drug therapy: Corticosteroids (improve recovery rate to 62% within 12 months), consider antivirals
3. Vestibular rehabilitation: Crucial for promoting central compensation 2, 3

Remember that HINTS examination should only be applied in cases of acute vestibular syndrome (continuous vertigo >24 hours) and requires proper training for accurate interpretation.