Disorders of olfactory (1st) nerve

This code represents any pathological condition affecting the first cranial nerve, the olfactory nerve, which is responsible for the sense of smell. These disorders can manifest as a complete loss of smell (anosmia), a reduced sense of smell (hyposmia), or a distorted sense of smell (dysosmia/parosmia).

Use this code when documentation indicates a diagnosed disorder of the olfactory nerve, such as anosmia, hyposmia, or dysosmia, due to various etiologies like trauma, infection, or neurological conditions. Supporting documentation should clearly state the impairment of the sense of smell and attribute it to the olfactory nerve.

• Differentiate from symptoms like "loss of smell" without a confirmed olfactory nerve disorder; consider symptom codes if the underlying cause isn't specified.
• Always code the underlying cause of the olfactory nerve disorder first, if known and documented (e.g., head injury, tumor).
• Avoid using this code for transient or self-limiting olfactory disturbances not attributed to a specific nerve pathology.