Vestibular Disorders. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

Автор: Группа авторов
Издательство: Ingram
Серия: Advances in Oto-Rhino-Laryngology
Жанр произведения: Медицина
Год издания: 0
isbn: 9783318063714
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eyes to initially move together (Fig. 6c), followed by a rapid corrective eye movement or catch-up saccade, which rapidly refixates the eye (Fig. 6d). A positive catch-up saccade in the horizontal canal plane is usually evident in the subject, presenting with an acute vestibular syndrome secondary to vestibular neuritis [13]. To confidently separate vestibular neuritis from an acute vestibular syndrome of central origin, it is essential to prove the presence or absence of all the attributes of neuritis. A positive “HINTS plus” test battery (positive head impulse test, typical peripheral nystagmus, absence of skew deviation, and normal hearing) has been shown to separate central from peripheral causes of acute vestibular syndrome with greater accuracy than an MRI scan [13].

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      Testing Saccades and Pursuit

      Visual Cancellation of the Vestibulo-Ocular Reflex

      Ask the patient to sit on a swivel chair with arms extended, hands clasped and thumbs pointing up. Rotate the patient en bloc in the yaw plane as the patient fixates on his/her own thumbs. Inspect the eyes for fast phases. In a normal subject with normal VOR cancellation, the eyes remain fixed on the target and no fast phases are observed. In cerebellar disorders and in disorders of smooth pursuit, VOR cancellation is impaired and fast phases toward the direction of rotation are seen.

      Stance and Gait

      Postural Blood Pressure, Pulse, and Auscultation

      Lying and standing blood pressure and pulse measurements (20-mm systolic blood pressure drop or 30 beats per minute heart rate rise) help identify orthostatic intolerance as a cause of dizziness. Auscultation of the heart, neck, and supraclavicular fossae for bruits may identify cardiac murmurs (aortic stenosis) or vertebral artery stenosis.

      Differential Diagnosis

      Often, a carefully elicited history supported by a competent examination yields a correct diagnosis with a clear management path, without requiring further investigation. Episodic positional vertigo lasting seconds, with paroxysmal positional nystagmus confirming BPV, leading to a liberatory manoeuvre, is a cause for celebration. Acute vestibular syndrome, where isolated spontaneous vertigo is accompanied by typical peripheral nystagmus and an unequivocally positive bedside head impulse confirming vestibular neuritis is another. Conversely, there will be instances where the diagnosis has to be avidly pursued. When the patient with episodic positional vertigo has a negative Hallpike test, it will be necessary to perform a second, third or fourth assessment on a symptomatic day before BPV is proven. When the patient with an acute vestibular syndrome does not fulfil all “HINTs plus” criteria (positive head impulse, peripheral nystagmus, absent skew, normal hearing), alternate causes of acute vestibular syndrome such as brainstem stroke should be considered. A diffusion-weighted MRI scan should be undertaken, and it may be necessary to commence an antiplatelet therapy even when there is no clear infarction, especially in the presence of vascular risk factors. Patients with recurrent spontaneous vertigo lasting hours may have no historic features or examination findings pointing to whether the vertigo is due to endolymphatic hydrops or VM. Here, the clinician may need to use audio-vestibular tests to assist with differential diagnosis and plan to urgently assess the patient on a symptomatic day to help them determine whether they are dealing with VM or MD. There is a need for methods of capturing the ictal nystagmus that accompanies acute spontaneous vertigo in patients’ own environments as additional means of identifying the underlying vestibular disorder.

      References