The 12 cranial nerves participate in a total of seven neural functions. Each of these seven functions is designated by a three letter acronym.

• The first letter is either G (General) or S (Special).
  • General refers to primitive and/or external structures of the body.
  • Special refers to senses unique to the head (taste, olfaction, hearing, vision, and balance) and to muscles of branchial arch derivatives.
• The second letter is either S (Somatic) or V (Visceral).
  • Somatic refers to non-visceral structures including skin, muscles, tendons, joints, retina (vision), basilar membrane (hearing), and utricle/saccula (balance).
  • Visceral refers to organs of the body cavity, smooth muscle, vessels, and glands.
• The third letter is either A (Afferent) or E (Efferent).
  • Afferent refers to flow of neural information toward the brain (sensation)
  • Efferent refers to flow of neural information toward the periphery (motor).
• Knowledge of the functional components and the deficits that follow damage to each provides the basis of the thorough neurological exam.

The Seven Functional Components

• GSA – General Somatic Afferent
  • Touch, temperature, and pain to non-visceral structures
• GSE – General Somatic Efferent
  • Motor to skeletal muscle
• GVA – General Visceral Afferent
  • Touch (distention), temperature, and pain from the viscera
• GVE – General Visceral Efferent
  • Motor to viscera, smooth muscle, and glands
• SSA – Special Somatic Afferent
  • Vision, hearing, and balance
• SSE – Doesn’t exist
• SVA – Special Visceral Afferent
  • Taste and olfaction
• SVE – Special Visceral Efferent
  • Motor to muscles derived from the branchial arches