Olfactory nerve

The olfactory nerve (CN I) is the first and most rostral of the cranial nerves. Along with the optic nerve, it is actually a peripheral outpost of the central nervous system.

The bipolar cell is the first-order sensory neuron located in the roof of the nasal cavity, immediately inferior to the cribriform plate of the ethmoid bone. This cell is analogous to the sensory cells of spinal nerves, whose cell bodies reside in the dorsal root ganglion. Their central processes form filaments (approximately 20) which pass through the cribriform plate, pierce the dura mater and relay in the olfactory bulb, the expanded anterior portion of the nerve that sits in the olfactory fossa. The central process of these second-order neurons forms the olfactory nerve which passes posteriorly within the olfactory groove of the anterior cranial fossa and then in-between the gyrus rectus medially and orbital gyrus laterally.

Anterior to the anterior perforated substance, they form medial and lateral olfactory striae. The lateral olfactory striae project to the uncus. The medial olfactory striae ultimately project to the hypothalamus and brainstem nuclei

Coronal images are the best to depict the olfactory nerve as it is situated deep in the olfactory groove.

Anatomy: Brain

Anatomy: Brain

Article information

rID: 1770
Section: Anatomy
Synonyms or Alternate Spellings:
  • Olfactory nerve (CN I)
  • Olfactory nerve (I)

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Cases and figures

  • Figure 1: illustration - olfactory nerve (CNI)
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  • Case 1: olfactory nerves (MRI)
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  • Case 2: normal appearance on T2WI (annotated)
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  • Case 3: normal cranial nerves
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  • Case 4: absent right olfactory bulb
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