Inferior Alveolar Nerve — Course and Applied Anatomy
Origin
- Largest branch of the posterior division of the mandibular nerve (V3)
- Arises in the infratemporal fossa
Course
| Segment | Details |
|---|---|
| Infratemporal fossa | Descends medial to lateral pterygoid, then between sphenomandibular ligament and ramus of mandible |
| Before mandibular foramen | Gives off nerve to mylohyoid in the pterygomandibular space |
| Mandibular foramen | Enters the mandibular canal accompanied by the inferior alveolar artery and vein |
| Mandibular canal | Runs through the body of mandible below the tooth roots, giving branches to all lower teeth via the inferior dental plexus |
| Mental foramen | Divides into mental nerve and incisive nerve at the level of the 2nd premolar |
Branches
| Branch | Origin | Distribution |
|---|---|---|
| Nerve to mylohyoid | Just before mandibular foramen | Motor to mylohyoid and anterior belly of digastric |
| Inferior dental branches | Within mandibular canal (via inferior dental plexus) | Pulp and periodontal membrane of all lower teeth |
| Mental nerve | At mental foramen | Skin of chin; skin and mucous membrane of lower lip |
| Incisive nerve | Continuation beyond mental foramen | Pulp of lower incisors and canine |
Relations
- Lateral: Ramus of mandible
- Medial: Sphenomandibular ligament (in infratemporal fossa); medial pterygoid
- Anterior: Lingual nerve (lies anterior and medial to inferior alveolar nerve in the infratemporal fossa)
- Accompanied by: Inferior alveolar artery (branch of maxillary artery, 1st part)
Applied Anatomy
Inferior Alveolar Nerve Block (Mandibular Block):
- Most common dental anaesthesia technique
- Needle inserted into pterygomandibular space, medial to ramus
- Local anaesthetic deposited near mandibular foramen
- Anaesthetises: all lower teeth on that side, lower lip, chin, anterior 2/3 tongue (via lingual nerve which is nearby)
- Lingual nerve often anaesthetised simultaneously
Mandibular Fracture:
- Fracture at angle of mandible or through mandibular canal → inferior alveolar nerve damage
- Results in: paraesthesia or anaesthesia of lower lip and chin (mental nerve distribution)
Mental Nerve Neuropathy:
- “Numb chin syndrome” — anaesthesia of chin and lower lip
- Causes: mandibular fracture, metastatic disease to mandible (breast, prostate, lung → mandibular metastasis), dental procedures, multiple myeloma
- Important: mental nerve neuropathy without trauma = malignancy until proven otherwise
Third Molar (Wisdom Tooth) Extraction:
- Inferior alveolar nerve lies close to roots of lower 3rd molar
- Risk of nerve damage during difficult extractions → post-operative paraesthesia of lower lip
Mandibular Nerve | Branches of Mandibular Nerve — Posterior Division