What is Vestibular Neuronitis?
Neuronitis is an infection, viral or bacterial, that inflames the vestibulocochlear nerve. In most cases, neuronitis results in unilateral vestibular weakness. This means that the vestibulocochlear nerve on the side of infection is not working as effectively to transfer vestibular input to the brain as the unaffected side.
Vestibular Neuronitis Symptoms:
Sudden onset of severe vertigo, nausea and vomiting. Onset often occurs following illness, such as upper respiratory infection. Symptomology can last for weeks with very gradual improvement over time. Gradual improvements occur as the brain compensates for the unilateral weakness.
Vestibular Neuronitis Testing:
Unilateral vestibular weakness, resultant from neuronitis, may be revealed during caloric testing, an integral part of a VNG assessment. During caloric testing, the vestibular system is stimulated by “irrigating” both ears with warm and cool air. When warm air is used to irrigate the ear, endolymph within the horizontal canal becomes lighter and flows upward. When cool air is used to irrigate the ear, endolymph in the horizontal semicircular canal becomes heavier and flows downward. This flow of endolymph results in the patient feeling as if his/her head moving. When a patient experiences this spinning sensation, or vertigo, the eyes reflexively move in a specific pattern called nystagmus. It is normal to experience vertigo and nystagmus during caloric testing. The intensity of the nystagmus is measured to determine the strength of the vestibular response at each ear. A unilateral vestibular weakness is revealed when one ear’s response is weaker than expected.
vHIT assesses the integrity of the vestibulo-ocular reflex (VOR) relative to each semicircular canal. For more information regarding the VOR and its relationship with the semicircular canals please refer to the vestibular anatomy section. During vHIT, the patient wears goggles that are used to measure eye movements. The provider instructs patient to keep eyes focused on a visual target and then moves the patient’s head in short, quick motions. The measurement of eye movement is then compared to head movement. In a patient with normal VOR function, eye movement should be equal but opposite of head movement, allowing the patient’s eyes to stay focused on the visual target despite head movement. In a patient with impaired VOR function, patient’s eyes will lose focus on visual target when head is moved. Neuronitis can result in impaired VOR function related to the side of unilateral weakness.
Vestibular Neuronitis Management:
Neuronitis will resolve itself as the brain completes the compensation process. The more the patient moves, the more vestibular input to the brain, resulting in faster compensation. Neuronitis can be furthered addressed via vestibular rehabilitation therapy as prescribed by a physical therapist. Refer to this link for more information regarding vestibular rehabilitation therapy: http://www.fyzicalbalance.com/our-approach/howdoesitwork