Endonasal

Endonasal describes anything that occurs within or through the nasal passages. In medical use, the term covers two related concepts: routes of drug administration through the nose and surgical or endoscopic approaches that access deeper structures via the nasal corridor. The word emphasizes that the nose serves as the entry point or pathway rather than a distant or external route.

In drug delivery, endonasal (often used interchangeably with intranasal) administration uses the nasal mucosa to absorb medications, sometimes to achieve local effects in the nasal passages and sinuses or to provide systemic absorption. Advantages include rapid onset and avoidance of first-pass metabolism. It is used for vaccines, migraine therapies, antihistamines, and other agents. Limitations include variability in absorption due to nasal congestion, mucosal condition, and mucociliary clearance, as well as potential local irritation or epistaxis. Not all drugs are suitable for nasal delivery, and dosing precision can be a concern.

In surgical practice, endonasal endoscopic approaches access the skull base, pituitary region, or paranasal sinuses through the nasal cavities. These procedures use specialized endoscopes and instrumentation to provide direct visualization and reach midline structures with minimal external incisions. Indications include pituitary tumors, certain skull base tumors, cerebrospinal fluid leaks, and complex chronic rhinosinusitis. Benefits include reduced morbidity and faster recovery compared with open approaches, while challenges involve a steep learning curve, need for multidisciplinary teams, and risks such as cerebrospinal fluid leaks, meningitis, vascular injury, nasal trauma, and potential olfactory impairment. Endonasal techniques continue to evolve with advances in imaging, navigation, and instrumentation.