Video 1. An introduction to Neuro-Otology. Prof A Moodley Neurology Registrar Weekend, 2019

 

(vv)Neurotology.mp4(tt)


 


Symptoms of Vestibular Disease                              Examination for Vestibular Disease

Normally, the difference between the vestibular sensory organs is relayed centrally to the vestibular nuclei, generating the eye movement commands that compensate for head movements when we attempt to stabilize the retinal images of objects in the environment, either as the rotational vestibulo-ocular reflex (VOR), sensed by the semicircular canals, or the translational VOR, sensed by the otolith organs1

The sensation of vertigo is derived from head rotation being identified by the paired semicircular canals as a reciprocal change in activity between each set of horizontal canals in each vestibular apparatus. There is a baseline high tonic rate of firing resulting in a constant stream of action potentials feeding into the brain stem. A unilateral disorder that abruptly disrupts this tonic firing rate causes a static imbalance between the right and left vestibular afferents that leads to vertigo, and deviation of the eyes towards the lesioned side, the tonic output of which is now reduced.   This results in vestibular nystagmus with slow phases that move the eyes toward the lesion and corrective quick phases that move the eyes away from the lesion: the direction of nystagmus is away from the lesioned side.

Most vestibular syndromes involve both the semicircular canal and otolith functions. This reflects the underlying anatomy of the systems: the different receptors for perception of angular and linear acceleration are housed in a common labyrinth, and their peripheral (8th nerve) and central (medial longitudinal fasciculus) pathways take the same course. Additionally, there is a convergence of otolith and semicircular canal input at all levels of the CNS, from the vestibular nuclei to the vestibular cortex2.
Common examples of combined vestibular syndromes, where both seimicircular canal and otolith function are involved include2:
 Peripheral: vestibular neuritis: this is mostly caused by failure of the superior division of the vestibular nerve that subserves the horizontal and anterior semicircular canals and the maculae of the utricle and the anterosuperior part of the saccule.
 Central: lateral medullary syndrome: this involves the medial and superior vestibular nuclei, where otolith and semicircular canal input converge. This causes ocular and body lateropulsion, and spontaneous torsional nystagmus.

Both peripheral and brainstem vestibular dysfunction may cause a pathological sense of self-motion and visuo-vestibular conflict. Although vertigo is a major vestibular symptom of a peripheral vestibular disturbance, that is largely the case when acute asymmetries of vestibular function occur, and may not hold true for long-standing dysfunction of the vestibular system. A slowly decreasing or relatively stable but permanent loss of function is a frequent occurrence (as occurs in aging, the equivalent of presbyopia and presbyacusis).  This loss, despite central compensation, leads to a range of other complaints due to the impaired ability of the normally extremely sensitive labyrinthine sensors to detect head motion and head orientation relative to gravity. These persisting complaints include loss of visual (dynamic) acuity, imbalance, fear of falling and actual falls, visual vertigo, chronically enhanced cognitive load and fatigue, all reflecting the various functions of the labyrinth3.

Although it is widely accepted that most patients with vestibular disease present with variable combinations of vestibular disease (vertigo, dizziness, postural symptoms, visuo-vestibular symptoms)4, it is also becoming increasingly clear that the coupling of a particular symptom to a specific organ is problematic, for example, presyncope's linkage to the cardiovascular system, or vertigo's linkage to the vestibular system. About 10% of patient with hemispheric stroke report a sensation of "rocking-rolling, like being on a boat"5, and patients with primary cardiac diseases such as arrhythmias, myocardial infarction, and aortic dissection may present with transient vertigo, as opposed to presyncope or other types of dizziness. In one series of patients with vertebro-basilar disease, many of whom had subclavian steal, recurrent dizziness was present in half, and a third had syncope, presyncope or drop attacks6.  Similarly, vertigo has been reported in conditions such as orthostatic hypotension, migraine, epilepsy and panic attack4.

Definitions5


Dizziness and vertigo are potentially problematic terms, with a number of definitions, related partly to the absence of a defined vestibular sense: our awareness of the vestibular system is largely brought to consciousness only when the system is failing, and words to describe that are either lacking or imprecise1.
 -Vertigo: “a false sense of motion of spinning or nonspinning quality” . This typically refers to a false sensation of movement of the self, when no motion is present, or altered sensation of motion when motion occurs. The motion sensation may be rotary, translational, or tilt.  A similar sensation of motion of the environment is a vestibulovisual symptom (called external vertigo).  Vestibular vertigo is an illusion of movement (spinning, rocking, or tilting) of oneself or one’s surroundings and implies a left-right asymmetry in the neural activity of the vestibular nuclei7.
 -Dizziness: “disturbed or altered spatial orientation without a false sense of motion.”  Note that this rather non-specific symptom may be the major complaint of BPPV, especially of the elderly and of patients with chronic unilateral vestibular disease4.
 -Oscillopsia describes the impression of a bidirectional, oscillating visual motion that incorporates complaints such as “jumping” or “bouncing” vision as can occur in opsoclonus (if the head is still) or during movement of the head in bilateral vestibular failure.
 -Vestibulovisual symptoms: Visual symptoms that result from vestibular pathology or visualvestibular interactions. 

In the approach to vestibular disorders, an emphasis on TIMING and TRIGGERS is useful8:

TIMING(Table 1)
Patients may be divided into those whose dizziness was:
 -Transient or episodic (lasting SECONDS to HOURS) or
 -Those with persistent or continuous dizziness (lasting DAYS to WEEKS).

Note that the three syndromes may overlap and merge into one another:
-Acute
: rapid onset of continuous vertigo, dizziness and/or unsteadiness of at least one day, and typically lasting days to weeks, with features suggestive of new, ongoing vestibular system dysfunction (e.g. vomiting, nystagmus, severe postural instability). (bottom half, Table 1)
-Episodic: recurrent attacks of transient vertigo, dizziness and/or unsteadiness lasting seconds/minutes or hours with remissions between attacks, features suggestive of temporary, short-lived vestibular system dysfunction (eg, nausea, nystagmus, sudden falls). (top half, Table 1)
-Chronic: clinical syndrome of chronic vertigo, dizziness or unsteadiness lasting months to years and generally including features suggestive of persistent vestibular system dysfunction (eg, oscillopsia, nystagmus, gait unsteadiness).

Disorders causing the acute vestibular syndrome (see lower half of Table 1) are not generally important considerations in episodic patients (top half of Table 1) (although vestibular neuritis may be preceded by a single, transient episode of dizziness in about 25% of cases, and completed stroke in either the anterior or posterior circulation may be associated with transient dizziness or vertigo that resolves within minutes to hours).

Rarely, a prolonged attack of Meniere's disease or vestibular migraine may be prolonged and not transient/intermittent.

TRIGGERS8
This approach emphasises a search for specific triggers. These are naturally of greatest importance in patients with brief, episodic dizziness (top half of Table 1), and are unlikely to be valuable in patients presenting with an acute vestibular syndrome.  
The triggers for most patients with transient dizziness are positional or postural.  It may be difficult to establish if the vestibular syndrome is episodic or chronic, and it is important to enquire if the patient has asymptomatic phases in the presence of the triggers or not1.
There are potentially also specific triggers for reflex syncope or panic attacks.  

Examination may need to concentrate on findings which provoke symptoms. However, in cases of episodic dizziness, the examination is quite likely to be normal, emphasising that the history is critical to distinguish between, on the one hand, episodic causes which are common and benign, and their dangerous mimics on the other.  The presence of a trigger often indicates benign causes (for example, a change in head position in BPPV), although exertion and head turning would be exceptions to this rule, in that they may be associated with cardiac arrhythmia and vascular compresssion syndromes6.  Provocative tests are likely to be useful in the setting of episodic vestibular symptoms, and are not of value in the acute vestibular syndrome9.

Table 1.  CAUSES: Episodic and Non-Episodic (Non-Episodic equating to causes of the Acute Vestibular Syndrome)

Note that the type of dizziness in acute vestibular syndrome is not likely to be a good predictor of underlying aetiology9.
Most patients with acute vestibular syndrome have an acute peripheral vestibulopathy; however this can be mimicked by brainstem and/or cerebellar stroke. Examination should focus on specific symptoms which can distinguish brainstem stroke from peripheral causes.

 

  Seconds to hours  EPISODIC: transient or intermittent

   

BRIEF EPISODIC ATTACKS: COMMON-RARE CAUSES

   
    Unlikely to be symptomatic at time of consultation, unless intermittent
    symptoms triggered by certain actions.

    History critical; examination tends to be normal since it takes place between  
    episodes, and some symptoms  may need to be provoked

 

   
    Benign paroxysmal positional vertigo (BPPV) (seconds)
    Benign orthostatic hypotension (eg, medications) (seconds-minutes)
    Reflex syncope (seconds-minutes)
    Panic attack (minutes-hours)
    Menière’s disease (seconds-days) (> 1 day in 10%)
    Vestibular migraine (seconds-days) (> 1 day in 25%)
    Motion sickness disorder
    Vestibular paroxysmia
    Superior canal dehiscence syndrome

    DANGEROUS MIMICS

    TIA (seconds-hours)
    Cardiac arrhythmia (seconds-hours)
    Other cardiovascular emergencies (eg, myocardial ischemia, dissection)
    Neuro-humoral neoplasm (eg, insulinoma)    

 

      
ACUTE VESTIBULAR SYNDROME
Days to weeks  NON-EPISODIC: persistent or continuous

 

ACUTE VESTIBULAR SYNDROME
COMMON-RARE CAUSES

 

    Likely symptomatic at time of consultation

    Examination of importance, and physical findings should distinguish
    between benign and dangerous causes.

    Vestibular neuritis
    Multiple Sclerosis
    Viral labyrinthitis
    Drug toxicity (anticonvulsants, aminoglycosides)
    Herpes zoster oticus  

      DANGEROUS MIMICS

    Brainstem, cerebellar, labyrinthine stroke
    Bacterial labyrinthitis/mastoiditis
    Wernicke’s encephalopathy
    Brainstem encephalitis (eg, listeria, herpes simplex). 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Symptoms of the vestibular system

  - Static (head still) vestibular imbalance leads to spontaneous nystagmus.  Damage to the vestibular sensors on one side upsets the balance between the vestibular signals generated from both sides. This is reflected as a greater relative output from the intact apparatus, and this is interpreted by the brain as turning towards and stimulation of the horizontal semicircular canal on the intact side: this leads to an illusory sensation of self-rotation(vertigo)6.  
Static imbalance results in vegetative symptoms including nausea, vomiting, sweating and occasionally hypotension and syncope. 
  - Dynamic (head moving) disturbances affect vestibular function provoked by head motion or change in head position, in unilateral lesions due to the loss of the normal push-pull relationship of the horizontal canals, for example. This reflects abnormalities in gain (amplitude), direction, and/or timing (phase) of the VOR and vestibulospinal reflexes, or occasionally mechanical disruptions in the labyrinth (eg, benign paroxysmal positional vertigo and peri-lymphatic fistula).  Bilateral lesions lead to dynamic disturbances because of an overall loss of function, but rarely give rise to vertigo, nystagmus or vegetative symptoms. 

In everyday life, vestibular stimuli are integrated with visual, somatosensory, auditory, and motor efference inputs to derive estimates of self-motion. Perhaps the reason for the omission of vestibular perception from the traditional human senses is that, compared with the perceptual times for other senses, conscious awareness of changes in the vestibular system is relatively slow (70–160 ms). Accordingly, during daily life we are often unaware of workings of the vestibular system until it fails. Patients with vestibular disorders suffer not only from difficulties with balance but also report blurred vision, head-movement induced oscillopsia and difficulties during complex behaviors such as self-motion perception and navigation, and spatial perception11,12.

Symptoms of vestibular dysfunction include:

  1. Oscillopsia: the illusion that the environment is moving
  2. Changes in the tonic signals arising in the vestibular apparatus are interpreted as head motion. Anything that deranges that signal causes vertigo, a perception of head motion when the head is still.
  3. Vertigo may be associated with visuovestibular conflict, nausea, and vomiting.
  4. Spatial disorientation: patients often describe difficulty with driving, walking and large, open spaces, or being in crowded environments such as shopping malls and supermarkets.  These sensory-rich environments provoke and intensify sensory conflicts which aggravate feelings of disorientation as well as symptoms such as nausea and vomiting.  Note that symptoms of vertigo and postural imbalance occur frequently in healthy people, eg, symptoms may arise with overhead work while standing on an unstable wobbling ladder or in situations in which visual cues conflict with proprioceptive input (looking up at moving clouds). The likely physiological explanation for this is an unusual combination of multisensory inputs from the stabilizing systems12.  
  5. Due to vestibular imbalance, patients report a sense of self rotation away from the side of the lesion.
    Patients may also report that the room spins away (Room Rotates Away) from the lesion.  This illusory rotation is generated by the slow phases of nystagmus and the direction of rotation is in the direction of nystagmus (the opposite direction to the slow phases). Spinning of the room to the left indicates left beating spontaneous nystagmus and a right vestibular lesion.
  6. Postural imbalance.

Examination of the vestibular system and for nystagmus  
Entities marked with * are particularly important for distinguishing peripheral from central causes of vertigo


Static vestibular imbalance: Spontaneous nystagmus, ocular torsion, and ipsilesional SVV tilt
Dynamic vestibular imbalance: HIT, head-shaking nystagmus, vibration-induced nystagmus, and caloric paresis

  1. Examine for spontaneous nystagmus, initially assessed when the patient is looking straight ahead, ideally with Frenzel lenses which prevent the patient from using visual fixation to suppress spontaneous nystagmus.  Spontaneous nystagmus (with the head still) is the hallmark of an imbalance in the tonic levels of activity mediating the rotational VOR. When peripheral in origin, spontaneous nystagmus characteristically is damped by visual fixation and is increased or only becomes apparent when fixation is eliminated.  Hence, for the VOR, an equivalent of a Romberg test must be carried out, looking for spontaneous nystagmus with the patient wearing Frenzel goggles or during ophthalmoscopy (with the opposite eye occluded to prevent fixation). 
    The intensity of nystagmus is compared with that observed when the patient is fixating on visual target.  The intensity of nystagmus usually depends on the position of the eye in the orbit, and nystagmus arising from a peripheral lesion and most central lesions is more intense (slow-phase velocity higher) and may only be evident, when gaze is in the direction of the quick phase (Alexander's law).  With central lesions, however, the opposite occasionally occurs. Example of spontaneous vestibular nystagmus in Meniere's disease.
  2. * Gaze evoked nystagmus (GEN): the examination of gaze-holding function reflects the function of the brainstem-cerebellar neural integrator, and GEN is not a feature of peripheral vestibular disease.
  3.  Examine for positional nystagmus/positioning nystagmus: Peripheral vestibular diseases often cause a positioning or positional nystagmus. This type of nystagmus is paroxysmal, and can be found in disorders such as benign paroxysmal positioning vertigo (BPPV), Ménière’s disease, Superior Semicircular Canal Dehiscence, physiological “head extension vertigo” or “bending over vertigo.” It may rarely be identified due to a central lesion
  4. * Head impulse test
  5. * Skew deviation: alternating cover; first one eye and then the other (1-2 seconds per eye). 
  6. * Smooth pursuit: 30 degrees to the side in horizontal plane.
  7. Abnormalities in VOR gain4: Dynamic VA: normal < 3 line decrease at 2 Hz; abnormal > 3 line decrease
  8. Head shaking nystagmus : 2 Hz for 20 seconds, head down by 30o.
  9. Bucket test: subjective visual vertical
  10. Visual fixation suppression of the VOR
  11. Past pointing: patients point in the direction of the slow drift, that is, towards the lesion (Point Towards).  
    Mnemonic: RAPT (Rotate Away (both room and patient) Point Towards (and fall towards) the lesion).
  12. Balance and Romberg: as with pointing, the patient themselves rotate and fall towards the lesion, again, following the slow phase.

 

 

 

References

  1. Bisdorff A. Vestibular symptoms and history taking. Handb Clin Neurol. 2016;137:83-90. doi:10.1016/B978-0-444-63437-5.00006-6
  2. Bisdorff A, Von Brevern M, Lempert T, Newman-Toker DE. Classification of vestibular symptoms: towards an international classification of vestibular disorders. J Vestib Res. 2009;19(1-2):1-13. doi:10.3233/VES-2009-0343
  3. Kingma H, van de Berg R. Anatomy, physiology, and physics of the peripheral vestibular system. Handb Clin Neurol. 2016;137:1-16. doi:10.1016/B978-0-444-63437-5.00001-7
  4. Bisdorff A. How to take diagnose vertigo and ocular motor disorders. EAN 2020.
  5. Anagnostou E, Spengos K, Vassilopoulou S, Paraskevas GP, Zis V, Vassilopoulos D. Incidence of rotational vertigo in supratentorial stroke: a prospective analysis of 112 consecutive patients. J Neurol Sci. 2010;290(1-2):33-36. doi:10.1016/j.jns.2009.11.015
  6. Toursarkissian B, Rubin BG, Reilly JM, Thompson RW, Allen BT, Sicard GA. Surgical treatment of patients with symptomatic vertebrobasilar insufficiency. Ann Vasc Surg. 1998;12(1):28-33. doi:10.1007/s100169900111
  7. Welgampola MS, Bradshaw AP, Lechner C, Halmagyi GM. Bedside Assessment of Acute Dizziness and Vertigo. Neurol Clin. 2015;33(3):551-vii. doi:10.1016/j.ncl.2015.04.001
  8. Newman-Toker D.A new approach to the dizzy patient. [Neuro-Ophthalmology Virtual Education Library: NOVEL Web Site]. 2010. Available at hhttps://collections.lib.utah.edu/ark:/87278/s6tm7cr7
  9. Newman-Toker D.Acute Vestibular Syndrome Syllabus. [Neuro-Ophthalmology Virtual Education Library: NOVEL Web Site]. 2010. Available at https://collections.lib.utah.edu/ark:/87278/s66w9cr5
  10. von Campe G, Regli F, Bogousslavsky J. Heralding manifestations of basilar artery occlusion with lethal or severe stroke. J Neurol Neurosurg Psychiatry. 2003;74(12):1621-1626. doi:10.1136/jnnp.74.12.1621
  11. Zee DS, Jareonsettasin P, Leigh RJ. Ocular stability and set-point adaptation. Philos Trans R Soc Lond, B, Biol Sci. 2017;372(1718)
  12. Hotson JR, Baloh RW. Acute vestibular syndrome. N Engl J Med. 1998;339(10):680-685. doi:10.1056/NEJM199809033391007
  13. Wong, A. M. (2008). Eye movement disorders. Oxford: Oxford University Press.