1. The most common vestibular symptoms are dizziness, vertigo, and unsteadiness. Dizziness is a sensation of altered spatial orientation without a false sense of motion. Vertigo is a sensation of self-motion when none is occurring; this false sense of motion may be of any type (eg, rotational, swaying, bobbing). Unsteadiness is the sensation of being unstable while seated, standing, or walking. Unsteadiness can be isolated, but more often it accompanies either dizziness or vertigo. Although they have specific meanings, we will be using these terms interchangeably throughout this chapter, except as specifically noted.

2. Neurologists encounter patients with dizziness and vertigo in all practice settings – typically these are acute presentations in the emergency department or recurrent, episodic, or chronic presentations in the outpatient clinic.

3. The causes of dizziness and vertigo are broad, ranging from benign and self-limited (BPPV) to cannot-miss diagnoses (ischemic stroke).

4. The patient should not be triaged and/or diagnosed based on symptom quality/type alone (eg, dizziness vs vertigo vs unsteadiness) as patients are not consistent with their use of these descriptive terms.

5. The history and examination should be approached based on a framework of first diagnosing the patient appropriately by understanding the timing and triggers of their symptoms, followed by a targeted bedside examination.

1. Presentation: Vestibular neuritis presents with acute-onset continuous vertigo often associated with nausea, vomiting, and unsteadiness that often occurs after a viral illness. Labyrinthitis presents with the above symptoms, but also with new-onset hearing loss. The patient’s most severe symptoms typically last continuously for 2 to 3 days, after which they start to improve gradually over the following weeks, at which time vestibular symptoms may seem more intermittent and mainly triggered by head movements. Vestibular neuritis is a monophasic illness, and recurrences are relatively uncommon.

2. Pathophysiology: Vestibular neuritis is thought to be idiopathic/postinfectious inflammatory changes of cranial nerve VIII. Pathologic studies show atrophy of one or more of the vestibular nerve trunks, most consistent with an infectious or postinfectious process. The involvement of vestibular nerve inflammation is further supported by the occasional visualization on magnetic resonance imaging (MRI) of enhancement of the vestibular nerve on the affected side in the acute phase of vestibular neuritis, especially when double or triple the normal dose of contrast agent is administered. MRI is neither necessary nor sufficient for the diagnosis of vestibular neuritis, which is a bedside clinical diagnosis.

3. Prognosis: Vertigo may be intense within the first few days, but then usually settles down and resolves into a syndrome of head motion intolerance and postural instability that improves over days to weeks, occasionally months. A small percentage of patients are left with chronic vestibular symptoms that never completely resolve.

4. Diagnosis: Diagnosis is made at the bedside based upon a peripheral-localizing HINTS examination, which means all the following examination features of the peripheral HINTS must be true to make a diagnosis. The following is for a patient with left vestibular neuritis (all rights vs lefts would be reversed for a right vestibular neuritis). The patient will have spontaneous unidirectional rightward-beating horizontal nystagmus with a mild torsional component that increases in intensity when looking to the right (ie, gaze toward the fast phase and away from the lesioned side). This pattern of nystagmus follows Alexander law. The head impulse test (HIT) toward the left will reveal a catch-up saccade. (Note that during the acute illness phase, when spontaneous nystagmus persists, this refixation saccade will be in the same direction as the nystagmus fast phase, so it must be recognized by the fact that it is of greater amplitude or out of phase/rhythm with the rest of the nystagmus beats.) Last, there should be no appreciable skew
deviation with the cross-cover test. As with this example, the fast phase of the nystagmus beats in the direction opposite of the affected ear and increases when looking in the direction of the fast phase. The catch-up saccade occurs with HIT in the direction of the impaired vestibular nerve. When learning to perform the HIT, clinicians should move the head from outward (lateral) toward the midline (center)—this prevents them from moving the head too far laterally, which is more comfortable for the patient and allows the examiner to focus on obtaining the correct head velocity. In addition, this reduces confusion with the patient’s nystagmus (because both rightward and leftward head impulses end with the patient’s head and gaze in the midline, reducing any confounding effect of the eyes being eccentrically placed at the end of the test—where the confounding nystagmus might be of high intensity only in one direction, purely based on orbital eye position). For example, in left vestibular neuritis when the patient’s head is turned center-to-lateral toward the left (and their eyes move to the right), the nystagmus intensifies, which could easily be confused as a large catch-up saccade. Also important to note is that a patient with vestibular neuritis should not have new-onset hearing loss, and, if they do, ischemia of the labyrinth (eg, from evolving AICA-territory infarction) should be suspected unless otoscopy shows a clear explanation for hearing loss, such as evidence of middle ear infection leading to inner ear invasion, causing bacterial labyrinthitis. Viral labyrinthitis should be a diagnosis of exclusion absent other features (eg, vesicles of the external ear or palate from herpes zoster oticus). The remainder of the patient’s neurologic examination should be normal, with the exception that they may have a vestibulospinal drift toward the affected side (analogous to the slow phase of the nystagmus). This may manifest as past-pointing with arms extended when eyes are closed or truncal sway toward the affected side while standing or walking, often requiring minor assistance to maintain steadiness. Patients should, nevertheless, be able to sit upright with arms crossed without significant truncal ataxia or sway as long as the eyes are open (in contrast to some patients with acute stroke).

5. Treatment

1. Presentation: Ischemic strokes have a broad range of presentations as described elsewhere in this textbook. When ischemic strokes affect the posterior circulation and cause dizziness or vertigo, there can be cranial nerves affected in addition to the eighth cranial nerve or other central signs (eg, motor, sensory, cerebellar, or autonomic findings). However, more often these “vestibular stroke” cases present as an isolated AVS without obvious neurologic symptoms or signs.

2. Pathophysiology: Strokes presenting with dizziness are typically caused by interruption of blood flow in the posterior circulation (the vertebrobasilar system). These strokes occur due to the same mechanisms of ischemic stroke described in Chapter 6. One mechanism that should not be overlooked, especially in young patients with neck pain presenting with dizziness, is vertebral artery dissection. The anatomic location of strokes causing isolated AVS presentations can be either cerebellar (eg, posterior inferior cerebellar artery [PICA] territory involving the nodulus) or brainstem (eg, small stroke involving the inferior cerebellar peduncle or vestibular nucleus).

3. Prognosis: Patients with dizziness from ischemic strokes can improve over weeks to months as with other stroke syndromes. Cerebellar ischemic strokes typically
recover very well, even if they are quite large (assuming the patient receives prompt care, survives the acute illness phase, and does not suffer a second, more devastating stroke).

4. Diagnosis: In patients presenting with acute onset dizziness meeting criteria for the acute vestibular syndrome, diagnosis is made at the bedside based on a central-localizing HINTS examination. To be considered central-localizing, any one of the following examination features can be present to make a diagnosis. The patient’s head impulse test is usually (˜90%) bilaterally normal, meaning there is no catch-up saccade with head impulse test in either direction, which suggests normal vestibulo-ocular reflexes. These patients can have spontaneous nystagmus that is direction changing (ie, right beating in rightward gaze, left beating in leftward gaze), dominantly vertical, or dominantly torsional (˜40%). With alternate cover test there can be a skew deviation, a vertical misalignment of the eyes (˜25%). Only one of the features listed above needs to be present in patients with acute vestibular syndrome to classify them as having a central-localizing examination. Following the HINTS Plus decision rule, the presence of new onset hearing loss is considered a central finding until proven otherwise, when otoscopy is normal. This is because AVS plus hearing loss is about equally likely to be due to labyrinthine infarction linked to AICA- or basilar-territory ischemia as to be due to viral labyrinthitis (and, in cases of isolated labyrinthine infarction, the HINTS portion of the exam appears peripheral). The remainder of the complete neurologic examination may reveal other examination deficits, which can raise the examiner’s suspicion for ischemic stroke. In particular, severe truncal or gait ataxia requiring balance assistance is usually due to stroke, rather than vestibular neuritis. A stroke diagnosis can be confirmed with an MRI brain, though the HINTS examination has been shown to have higher sensitivity than MRI within the first 48 to 72 hours of onset of symptoms.

5. Treatment: Treatment of acute ischemic stroke is discussed elsewhere in this book, but if within the presenting time window and a candidate for the intervention, patients should be treated with thrombolytics and/or thrombectomy.

1. Presentation: The classic triad of Wernicke encephalopathy is ophthalmoparesis, ataxia, and confusion. Most patients do not present with all features of the classic triad. In fact, patients can present with isolated acute-onset vertigo, dizziness, or unsteadiness with associated spontaneous and gaze-evoked nystagmus (ie, AVS). On ocular motor examination, patients can have spontaneous upbeat nystagmus that converts to downbeat nystagmus with convergence. Over time, the patient’s upbeat nystagmus can permanently convert to a spontaneous downbeat nystagmus. Gaze-evoked nystagmus and bilaterally abnormal HIT can be seen as well, often with a history of weight loss, malnutrition, or even uncontrolled vomiting, such as in hyperemesis gravidarum.

2. Pathophysiology: Thiamine plays an important role in multiple biochemical pathways; its deficiency can lead to damage of vulnerable regions within the diencephalon and brainstem, which causes the patient’s symptomatic presentation. In our example of spontaneous upbeat nystagmus, it is hypothesized that thiamine deficiency and associated thiamine pyrophosphate deficiency lead to an accumulation of glutamate. This excess glutamate can result in damage to areas near more fragile portions of the blood-brain barrier, such as the structures adjacent to the ventricular spaces, including, in particular, the area postrema in
the dorsal medulla. Damage localized to the dorsal medulla can cause disruption in key nuclei (intercalatus and Roller), which is thought to lead to upbeat nystagmus.

3. Prognosis: With treatment, patients with Wernicke encephalopathy can often experience improvement. However, with delayed treatment, both the physical and neuropsychological effects of Wernicke encephalopathy can persist, which can be debilitating. If left untreated, Wernicke encephalopathy can lead to coma and death.

4. Diagnosis: Diagnosis is suspected based on the patient’s clinical presentation and history, but there are no formally established diagnostic criteria. A low blood thiamine level is supportive of a diagnosis of Wernicke encephalopathy. Although imaging is not needed for a diagnosis of Wernicke encephalopathy, MRI can show increased signal in DWI and T2 FLAIR sequences in the dorsal medulla, surrounding the aqueduct and third ventricle, mammillary bodies, and in the thalamus.

5. Treatment: For patients with suspected Wernicke encephalopathy, treatment with parenteral thiamine is recommended. This should be given urgently as soon as suspected to avoid permanent deficits. The typical regimen consists of 500 mg thiamine three times per day for 2 days, followed by 250 mg daily for 5 days. Often, other B vitamins are replaced simultaneously.

1. Presentation: Just as an ischemic stroke affecting the vertebrobasilar system can present with isolated dizziness, a transient ischemic attack (TIA) can as well. These patients can present with transient, unprovoked, acute-onset dizziness, vertigo, or unsteadiness that occurs in isolation or associated with other neurologic symptoms referential to the posterior circulation. Although the duration of a TIA, by definition, is less than 24 hours, the symptoms are more commonly shorter in duration (usually lasting minutes up to several hours). The most common posterior circulation TIA symptom is isolated dizziness or vertigo, and studies have found that these TIAs tend to persist longer than anterior circulation TIAs (which usually last less than an hour).