Test: Vestibular Physiology and Assessment of Vestibular Function - 1 - NEET PG MCQ

• Nystagmus and vertigo per se are not the manifestations of cochlear diseases. Cochlear diseases lead
• to hearing loss. Vestibular pathologies additionally there may be tinnitus and deafness when there
• occurs involvement of cochlea.
  • In Cerebellar disease the nystagmus is pendular.
  • In Vestibular disease the nystagmus is jerky.
  • In the Arnold-Chiari malformation a part of the brainstem and the cerebellum are herniated into the
• cervical vertebral canal. The Arnold-Chiari malformation is typically associated with vertical downbeat nystagmus.

• Vertebrobasilar insufficiency is a central vestibular condition.
• The two vertebral arteries on each side are branches of the subclavian arteries. They enter the skull through the foramen magnum and join at the pontomedullary junction to form the basilar artery which divides into two posterior cerebral arteries at the upper pons.
• The vertebrobasilar arterial system perfuses the medulla, cerebellum, pons, midbrain, thalamus, and occipital cortex.
• Therefore vertebrobasilar insufficiency leads to involvement of the central vestibular system

Acoustic reflex and Impedance audiometry are tests of hearing.

• In bi-thermal caloric test the normal response is C O W S, i.e. with Cold water nystagmus is towards the Opposite side and with Warm water it is towards the Same side.
• If both meatus are irrigated simultaneously with cold water the normal response is an up-beating nystagmus with torsion.

• If the same is done with warm water the nystagmus will be towards the same side, i.e. left side.
• Direction changing nystagmus is seen in central lesions.
• Positional nystagmus is seen in BPPV.

• If both meatuses are irrigated simultaneously with cold water, under normal circumstances the effect within both horizontal semicircular canals is equal and self cancelling; this eventually causes an up beating vertical nystagmus.
• Vertical upbeat means the fast component is upwards, hence the slow component will be downwards.