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Topic

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Middle superior alveolar nerve

The middle superior alveolar nerve (MSAN) is a branch of the infraorbital nerve, itself a division of the maxillary nerve (cranial nerve V2). It arises within the canal or infraorbital groove and courses along the lateral wall of the maxillary sinus, innervating the maxillary premolars, mesiobuccal root of the first molar, and adjacent buccal gingiva. The MSAN may be absent in some individuals, in which case its territory is supplied by the anterior superior alveolar nerve (ASAN) or posterior superior alveolar nerve (PSAN). This nerve is clinically significant in dental anesthesia, endodontics, and maxillofacial surgery due to its role in sensory innervation of the mid-maxilla.

Synonyms

  • Middle superior alveolar branch

  • Middle maxillary alveolar nerve

  • MSAN

Function

  • Provides sensory innervation to the maxillary premolars and the mesiobuccal root of the first molar

  • Innervates the buccal gingiva overlying its dental territory

  • Transmits tactile, pain, and temperature sensations from teeth and surrounding soft tissues

  • Assists in dental anesthesia targeting the mid-maxilla

MRI Appearance
T1-weighted images:

  • Appears as a thin, linear hypointense structure along the lateral wall of the maxillary sinus

  • Surrounded by hyperintense fat in the infraorbital canal, providing clear contrast

  • Pathological changes, such as nerve compression or neuroma, appear as focal hyperintense enlargement or disruption

T2-weighted images:

  • Nerve remains low-to-intermediate signal, while adjacent sinus mucosa or soft tissue may appear hyperintense

  • Useful for detecting edema, inflammation, or cystic lesions affecting the nerve

STIR (Short Tau Inversion Recovery):

  • Fat suppression highlights edema, inflammation, or nerve pathology

  • Normal nerve is low signal; pathological conditions appear bright hyperintense

CT Appearance

  • The MSAN is generally not directly visualized on conventional CT

  • Its course can be inferred by the location of the infraorbital canal and maxillary sinus walls

  • Bony landmarks such as the canine fossa, maxillary sinus, and infraorbital foramen are clearly seen

MRI images

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