Cranial Nerves Examination 1 to 6

Cranial Nerves 1-6

  1. Olfactory nerve
  2. Optic nerve
  3. Occulomotor nerve
  4. Trochlear nerve
  5. Trigeminal nerve
  6. Abducent nerve

Olfactory Nerve ( I CN)


Sensory nerve

Function – carries the sensation of smell

Requirements – common substances like

  • Coffee powder
  • Camphor
  • 1 small bottle of clove oil
  • 1 small bottle of peppermint oil

Procedure :

  • Ask the subject to sit comfortably on a stool
  • Both the nostrils should be patent
  • Ask the subject to close his eyes and one of his  nostril
  • Take the bottle containing Coffee powder close to the open nostril and ask him to identify it
  • Test each nostril separately
  • Note the result as Normal, Reduced, Absent or Perverted
  • Repeat the procedure with Camphor

Precautions:

  • Subject should close his eyes
  • Subject should be familiar with the odour
  • Both nostrils to be tested separately
  • One nostril should be closed when the other nostril is being examined

Disorders of Smell:

  • Anosmia
  • Hyposmia
  • Hyperosmia
  • Parosmia 

 Optic Nerve (II CN)

Sensory nerve

Function – carries the sensation of Vision

The examination of this nerve  consists of

  1. Visual Acuity
  2. Field of Vision
  3. Colour Vision
  4. Pupillary Reflexes 

Requirements:

  1. Snellen’s chart (for Far / Distant vision)
  2. Jaegers chart (for Near vision)
  3. Ishihara chart, Cotton wool test (for Colour vision)
  4. Lister’s Perimeter  (for Field of  vision)
  5. Torch (for Pupillary reflexes)

Visual receptors in retina

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Optic nerve

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Optic chiasma

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Optic tract

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Lateral geniculate body

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Optic radiation

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Visual cortex




Visual Acuity

Definition:

  • Visual acuity refers to the ability of the eye to resolve two point as separate

Types of Visual acuity:

  • Distant or Far vision
  • Near vision


Test for Distant/Far vision

Requirement:

Snellen’s Chart

  • This chart  consists of 8 rows of letters of varying sizes/fonts
  • The topmost line can be read by a normal subject at a distance of 60 meters
  • Subsequent lines at 36, 24,18, 12, 9, 6 & 5 meters respectively
  • Note the number above the  each row indicates the distance at which the letters should be read (D)