Vestibular Anatomy

Aka: Vestibular Anatomy, Vestibular Labyrinth

1. See Also
   1. Head and Neck Anatomy
2. Anatomy: Vestibular Structures
   1. Semicircular canals
      1. Monitors head rotation and spatial positioning
      2. Three semicircular canals, one for each direction (X,Y and Z access)
   2. Otolithic organs
      1. Utricle
         1. Contains otoliths (small stones) that settle with position changes
         2. Detects horizontal linear movement and Head Tilting
      2. Sacule
         1. Smaller, more globular organ without utricle communication
         2. Detects vertical linear movement (e.g. gravity)
3. Anatomy: Neurologic Structures
   1. Cranial Nerve VIII (2 tracts)
      1. Vestibular tract carries signals from the utricle and sacule
      2. Cochlear tract carries signals from the hearing apparatus in the Cochlea
   2. Vestibular nucleii
      1. Located in the pons and Medulla and receive input from the respective tracts of Cranial Nerve VIII
      2. Transmit signals to the rest of the Cerebrum, Cerebellum and spinal cord to combine with other inputs (e.g. occiptal lobe, dorsal columns)
   3. Medial Longitudinal Fasciculus and Oculomotor Nucleus
      1. Brainstem fiber tracts that connect with the Oculomotor Nucleus and carry information directing eye movement
      2. Connects with CN 3, CN 4, and CN 6 for eye motor activity, as well as CN 8 for head position input related to eye saccades
4. Anatomy: Vascular Structures
   1. See Vertebro-Basilar CVA
   2. Posterior Circulation via the vertebrobasilar system
   3. Vertebral arteries
      1. Two arteries ascend in parallel from the subclavian artery via each transverse foramen and join to form the Basilar Artery
      2. Branches
         1. Posterior Inferior Cerebellar Artery (see PICA CVA)
         2. Anterior Spinal Artery
   4. Basilar Artery
      1. Arises from the joining of the two Vertebral arteries and coursing anteriorly to join with the Anterior Circulation via the Circle of Willis
      2. Branches
         1. Anterior Inferior Cerebellar Artery
         2. Superior Cerebellar Artery
5. Anatomy: Images
   1. Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
   2. Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
   3. Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
   4. Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
   5. Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
   6. Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
6. References
   1. Ondrejka (2014) Crit Dec Emerg Med 28(10): 11-7