Mandibular Nerve Anatomy

• The mandibular nerve (CN V3) is the largest branch of the trigeminal nerve (CN V)
• It is a mixed nerve containing both sensory and motor fibers
• It is the only branch of the trigeminal nerve to contain motor fibers

Anatomy

• The mandibular nerve originates from the trigeminal ganglion in the middle cranial fossa
• It exits the skull through the foramen ovale
• Just outside the foramen ovale, the nerve gives off a small meningeal branch (nervus spinosus)
• The mandibular nerve then divides into a small anterior and a large posterior trunk
• These divisions occur in the infratemporal fossa

Branches

• The mandibular nerve has several branches that arise from its main trunk or its anterior and posterior divisions.
  • The main trunk gives off:
    • Meningeal branch (nervus spinosus): Sensory innervation to the dura mater of the anterior cranial fossa and middle cranial fossa
    • Nerve to medial pterygoid: Motor innervation to the medial pterygoid muscle; this nerve also gives off small branches to the tensor veli palatini and tensor tympani muscles
  • Anterior division branches include:
    • Masseteric nerve: Motor innervation to the masseter muscle
    • Deep temporal nerves (anterior and posterior): Motor innervation to the temporalis muscle
    • Nerve to lateral pterygoid: Motor innervation to the lateral pterygoid muscle
    • Buccal nerve (long buccal nerve): Sensory innervation to the skin and mucous membrane of the cheek and gingiva of the lower molars
  • Posterior division branches include:
    • Auriculotemporal nerve: Sensory innervation to the auricle, external auditory meatus, temporomandibular joint, and temporal region of the scalp
    • Lingual nerve: Sensory innervation to the anterior two-thirds of the tongue (taste and general sensation) and the floor of the mouth; it carries taste fibers from the chorda tympani (a branch of the facial nerve)
    • Inferior alveolar nerve: Sensory innervation to the lower teeth and gingiva; it gives off the mental nerve as a terminal branch, which provides sensory innervation to the skin of the chin and lower lip
    • Mylohyoid nerve: Motor innervation to the mylohyoid and anterior belly of the digastric muscle; it branches off the inferior alveolar nerve just before the inferior alveolar nerve enters the mandibular canal

Sensory Innervation

• The mandibular nerve provides sensory innervation to:
  • Lower teeth and gingiva
  • Skin of the lower lip and chin
  • Part of the auricle and external auditory meatus
  • Temporal region of the scalp
  • Cheek
  • Anterior two-thirds of the tongue (general sensation)
  • Floor of the mouth
  • Dura mater of the anterior and middle cranial fossae

Motor Innervation

• The mandibular nerve provides motor innervation to:
  • Muscles of mastication: masseter, temporalis, medial pterygoid, and lateral pterygoid
  • Mylohyoid
  • Anterior belly of the digastric
  • Tensor veli palatini
  • Tensor tympani

Functional Components

• Branchial motor (special visceral efferent): Innervates the muscles of mastication, mylohyoid, anterior belly of digastric, tensor veli palatini, and tensor tympani.
• General sensory (general somatic afferent): Conveys sensory information from the face, mouth, and dura mater.
• Special sensory (special visceral afferent): Carries taste sensation from the anterior two-thirds of the tongue via the lingual nerve and chorda tympani.

Clinical Significance

• Trigeminal Neuralgia:
  • Can affect the mandibular nerve, causing intense, stabbing pain in the lower face and jaw
  • Often triggered by light touch, chewing, or speaking
• Mandibular Nerve Block:
  • Used in dentistry to anesthetize the lower teeth and gingiva for procedures such as extractions and root canals
  • Can also be used to manage chronic pain conditions
• Nerve Damage:
  • Can occur due to trauma, surgery, or tumors
  • Results in sensory deficits (numbness, tingling, pain) and/or motor deficits (weakness or paralysis of the muscles of mastication)
• Temporomandibular Joint (TMJ) Disorders:
  • The auriculotemporal nerve innervates the TMJ, and irritation or inflammation of this nerve can contribute to TMJ pain and dysfunction
• Masseter Muscle Hypertrophy:
  • Enlargement of the masseter muscle due to excessive chewing or teeth grinding (bruxism)
  • Can be treated with botulinum toxin injections into the masseter muscle, which targets the masseteric nerve
• Lesions:
  • Complete lesions of the Mandibular nerve are rare, given its protected anatomical location.
  • Partial lesions involving specific branches can occur.
  • Motor lesions result in difficulty chewing, deviation of the mandible towards the affected side upon opening the mouth (due to unopposed action of the contralateral lateral pterygoid), and impaired function of the tensor veli palatini and tensor tympani.
  • Sensory lesions result in numbness or altered sensation in the areas innervated by the affected branches, such as the lower teeth, lip, tongue, or cheek.