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Topic

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Anterior superior alveolar nerve

The anterior superior alveolar (ASA) nerve is a sensory branch of the infraorbital nerve, which itself is a branch of the maxillary nerve (cranial nerve V2). It descends within the anterior wall of the maxillary sinus to innervate the maxillary incisors and canine teeth, the adjacent gingiva, and the labial mucosa. The nerve courses through the canine canal, communicating with the middle superior alveolar nerve in some individuals, and terminates near the apexes of the anterior teeth. Its relatively superficial course makes it important in dental anesthesia, endodontic procedures, and maxillofacial surgery.

Synonyms

  • ASA nerve

  • Anterior superior alveolar branch of V2

  • Maxillary anterior alveolar nerve

Function

  • Provides sensory innervation to the maxillary central and lateral incisors, canines, and their surrounding periodontium

  • Supplies the labial gingiva and mucosa overlying the anterior maxillary teeth

  • Transmits pain, touch, and temperature sensations from its area of supply

  • Acts as an anatomical guide in dental anesthesia for anterior maxillary procedures

MRI Appearance
T1-weighted images:

  • ASA nerve appears as a small, linear hypointense structure within the fat of the anterior maxilla or canine fossa

  • Surrounded by hyperintense fat, which provides contrast for visualization

  • Pathological changes such as nerve inflammation, compression, or neuroma appear as focal signal alterations

T2-weighted images:

  • Nerve remains hypointense to intermediate signal, while surrounding fat and soft tissues are hyperintense

  • Useful for detecting edema, inflammation, or compressive lesions

STIR (Short Tau Inversion Recovery):

  • Suppresses fat signal, highlighting nerve pathology

  • Normal ASA nerve is low signal, while inflammation or tumor appears hyperintense

CT Appearance

  • The ASA nerve itself is not directly visualized, but its course is inferred from the canine canal in the anterior maxilla

MRI images

Anterior superior alveolar nerve mri sagittal image -img-00000-00000