Neuroscience 10 – Dizziness and Vertigo
Anil Chopra
Vertigo (illusory movement) is a special case of a more general set of symptoms
‘Spatial Disorientation’. It may be caused by anything which disrupts the normal
transactions between the organism and environment, either functional or structural
and at a peripheral or central level of organisation.
Disabling dizziness is experienced by 70% of the population at some point in their life
and is normally handicapping.
Taking a History
- Patients often find it difficult to describe what “dizziness” is.
o Use faintness, disorientation, derealisation, anxiety.
- Anything which affects normal interaction with the world can result in
disorientation and illusory movement.
- Marked vertigo with nausea is a sign on peripheral vascular disorder.
- Symptoms include
o Intense spinning (rotational vertigo)
o Nausea
o Patient feels as if they are on a boat
o Patient feels as if the ground is unsteady
o Patient feels as if the world is spinning due to vestibular nystagmus.
Vestibular Disorder
Can be functional or structural:
Structural: caused by
- irritative disease
- destructive disease
Functional: caused by
- misinterpretation of sensory input by the brain
- mal adaptation
- loss of rules of correspondence between senses
- over awareness/magnification of sensory input
Can be both i.e. a structural disease which leads to chronic dysfunction.
 The general rule is that if the head is moved in a particular direction, the semicircular canal in that plane on that side will increase its rate of firing i.e. if the
head is turned to the right, then the right canals are stimulated.
 When the head is still the semicircular canals have an equal tonic firing rate.
 If there is a problem (e.g. lesion) in the left side, then the right side will signal
unopposed action potentials to the brainstem. This will give the patient the feeling
as if they are turning right which cause vertigo.
 It also has an effect on the vestibulo ocular reflex. The slow drift will be to the left
and the fast saccade to the right causing vestibular nystagmus.
 Similarly if there is irritatory excitation on a particular side, then the patient will
have the illusory feeling of rotating toward that side.
Treatment of common vestibular disorders:
 Reassurance that the patient is understood
 Pharmaco treatment – anti-virals, anti-emetics
 Treat associated anxiety, depression
 Cognitive behaviour therapy with desensitisation and physiotherapy
 Behavioural axiolytic tactics
 Minimise risk factors
Causes of Vertigo
Duration
Cause
Seconds
Benign Paroxysmal Positional Vertigo (BPPV) – this is caused by a
build up of debris in the semi-circular canals.
Minutes
Vertebrobasilar insufficiency (insufficient blood going to the brain via
vertebral and basilar arteries), migraine.
Hours
Meniere’s syndrome (disorder of the inner ear),
Days
Vestibular neuritis, infarction of labyrinth, herpes.
Continuous
Vestibular lesion
Mechanisms of common types of dizziness
Type
Mechanism
Vertigo
Imbalance in tonic vestibular signals
Near-faint dizziness
Diffuse cerebral ischemia
Psychophysiologic
Impaired central integration of sensory signals
Hypoglycemic dizziness
Inadequate brain glucose; increased circulatory catecholamines
Disequilibrium
Loss of vestibulospinal, proprioceptive, cerebellar, or
motor function
Ocular dizziness
Visual-vestibular mismatch due to impaired vision
Multisensory dizziness
Partial loss of multi sensory system function
Physiologic
Sensory conflict due to unusual combination of sensory signals
Drug-induced dizziness
CNS agents; change in cupula’s specific gravity (alcohol).
Vestibular Neuritis
“Acute Unilateral Vestibular Disorder”
Symptoms:
- vertigo
- oscillopsia (objects appear to be vibrating)
- imbalance
- nausea
- vomiting
- quick onset
- nystagmus
- pallor (pale)
- obvious ataxia (in-coordination of muscle movements)
These symptoms are intense for 1 or 2 days and then recover in a week or so.
Treatment:
- steroids
- anti-viral (cyclovirs)
- anti emetic
Disorders of Hearing
Conductive losses:
 Wax in the external meatus and middle ear otitis
 Otosclerosis
 ossicular discontinuity
 tympanic rupture
 congenital
 Cholesteotoma
Sensory (cochlear losses)
 Presbyacusis and noise exposure
 Inherited and secondary degenerations
 Ototoxicity
 Fistula (morphological disorders affecting cochlea)
 Hydrops (Menieres disease and secondary)
 Congenital
Neural (VIIIth nerve)
 Acoustic neuroma
 Demyelination
 Herpes
 Neural hearing loss (uncertain origin)
Spatial Orientation
People have awareness of spatial orientation using:
 Vision: disorders here can result in the railway carriage illusion; visual vertigo;
oscillopsia.
 Hapatic senses: i.e. touch, vibration, e.t.c. disorders here can result in plastic
rubbery legs and undulating floor
 Vestibular signals: Provide a spatial reference for other senses. Disorder here can
result in vertigo; motion sickness; derealisation.
Examinations of Hearing and Balance
Testing the integrity of the vestibular system can be useful to assess the condition of
the brainstem, especially in comatosed patients.
Eye Movements
Caloric Test
 Have the patient lying at a 30º angle.
 Inject either hot or cold air into their ear.
 With hot air, the convection currents cause endolymph to move and thus stimulating
excitation from the ampulla. The eyes will move contra-laterally (in the opposite
direction) to the injected ear.
 With cold air, the convection currents cause endolymph move in the opposite direction,
stimulating inhibition from the ampulla. The eyes will move ipsilaterally (in the same
direction) to the injected ear.
 Small amplitude short duration response to both hot and cold on one side  canal
paresis (loss of movement in the semicircular canals).
 Bilateral small short responses  bilateral hypofunction.
 Asymmetry of hot/cold responses is of little significance.
Head Rotation Test
 Ask the patient to stay focused on the doctor’s eye, and rotate their head.
 Normal response will be that the eyes stay focused.
 In vestibular dysfunction, the eyes will go with the head and not keep fixation and
patients often make saccades back to the fixation point. The lesion is on the side of
rotation.
Balance
 Patients will sway when standing still if they have vestibular dysfunction.
 They may also lean to one side or have a head tilt (lesion).
 Patients may also veer to one side when attempting to walk. (unilateral loss)
 Patients find it difficult to walk in the dark. (bilateral loss).
 Ask patient to walk briskly turning rapidly to right and left. Observe impairments,
particularly asymmetry.
Hearing
 A tuning fork at 512Hz is needed.
Rinne tests
Place the fork over the meatus of a normal ear will sound slightly louder than placed on the
mastoid. With a conductive loss the fork is louder on the mastoid.
Weber test
Test for sensor-neural hearing independent of conductive attenuation.
When the fork is placed on the mid-forehead the tone is normally heard ‘in the middle of
the head’. If there is a sensory loss on one side the tone is localised to the good side.