Which of the following cranial nerve assesses Nystagmus.  aCN III (Oculomotor) bCN IV (Trochlear) cCN V (Trigeminal) dNone of the above

Breakdown of the Problem

1. Identify the cranial nerves listed in the options.
2. Understand the function of each cranial nerve in relation to eye movement and nystagmus.

Relevant Concepts

• Nystagmus: An involuntary eye movement that can affect balance and vision.
• Cranial nerves involved in eye movement:
  • CN III (Oculomotor): Controls most of the eye's movements including constriction of the pupil and maintaining an open eyelid.
  • CN IV (Trochlear): Innervates the superior oblique muscle, which is responsible for downward and lateral eye movement.
  • CN V (Trigeminal): Primarily responsible for sensation in the face and motor functions such as biting and chewing; it does not directly assess nystagmus.

Analysis and Detail

• Nystagmus is typically assessed through examination of eye movements that involve the oculomotor system.
• The function of CN III is crucial for monitoring and controlling the majority of eye movements.

Verify and Summarize

While CN IV also plays a role in eye movement, it does not primarily assess or contribute to nystagmus. CN V does not relate to eye movements or nystagmus at all. Thus, the best answer related to nystagmus assessment is CN III.

Final Answer

a) CN III (Oculomotor) is the cranial nerve that assesses nystagmus.