anatomy(sensory division)

Last reviewed 01/2018

The trigeminal nerve's sensory root division has three key target nuclei once it has entered via the pons. The main sensory nucleus receives signals about facial two-point discrimination, position sense and proprioception. The proprioceptive nucleus lies in the midbrain. The nucleus for pain, temperature and facial touch descends through the brainstem to reach the upper cervical cord.

The nerve leaves the pons from the cerebellopontine angle and runs a course over the temporal lobe in the middle cranial fossa. The trigeminal ganglion - Gasserian - is formed at the petrous temporal bone and it is from here that the three divisions arise.

The first division - ophthalamic - travels in the cavernous sinus with the third nerve and emerges from the superior orbital fissure. This division supplies the skin of the forehead, the cornea and the conjunctiva. The second division - maxillary - emerges from the infraorbital foramen. This division supplies skin in the middle of the face and the mucous membranes of the upper part of the mouth, palate and nasopharynx. The third division - mandibular - travels with the motor part of the nerve and emerges through the foramen ovale to supply the skin of the lower jaw and mucous membranes of the lower part of the mouth.

Pain and temperature fibres from the face ultimately terminate in the spinal trigeminal nucleus - passing from the pons through the medulla - in the upper cervical cord. Touch and proprioceptive fibres travel from the pontine nucleus to form the trigeminothalamic tract which then ascends to the thalamus and thence to the post-central gyrus of the cortex. Note that this arrangement explains why upper spinal cord lesions can cause dissociated sensory loss of the face - retention of touch and proprioception, but loss of pain and temperature.