Which nerve may be absent in some patients, causing PSA and ASA to provide innervation instead?

Which nerve may be absent in some patients, causing PSA and ASA to provide innervation instead?

• A. MSA
• B. ASA
• C. PSA
• D. Infraorbital Nerve

Answer: (A)

The middle superior alveolar nerve can be absent in some people. When it isn’t present, the teeth and gingiva it would normally supply—the premolars (and often the mesiobuccal root of the first maxillary molar)—receive innervation from neighboring branches, mainly the anterior superior alveolar and posterior superior alveolar nerves. So PSA and ASA blocks can cover those areas by taking over the territory that a missing MSA would normally serve. This variation in nerve presence is why PSA and ASA may provide innervation instead of a distinct MSA.

The middle superior alveolar nerve can be absent in some people. When it isn’t present, the teeth and gingiva it would normally supply—the premolars (and often the mesiobuccal root of the first maxillary molar)—receive innervation from neighboring branches, mainly the anterior superior alveolar and posterior superior alveolar nerves. So PSA and ASA blocks can cover those areas by taking over the territory that a missing MSA would normally serve. This variation in nerve presence is why PSA and ASA may provide innervation instead of a distinct MSA.