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Trigeminal nerve (Cranial nerve V)

The trigeminal nerve, also known as Cranial Nerve V (CN V), is the largest cranial nerve and a major sensory nerve of the head and face. It has both sensory and motor functions, innervating the muscles of mastication and transmitting sensory information from the face, scalp, oral cavity, and meninges. The trigeminal nerve has three main branches (ophthalmic, maxillary, and mandibular) and is a key structure frequently evaluated in neuroimaging, particularly when investigating facial pain, neuropathies, or lesions.

Synonyms

  • Trigeminal nerve

  • Cranial nerve V

  • CN V

  • Fifth cranial nerve

  • Nervus trigeminus

Function

  • Sensory Functions:

    • Provides sensation (touch, pain, temperature) to the face, anterior scalp, nasal cavity, oral cavity, teeth, anterior two-thirds of the tongue (general sensation only), and dura mater.

  • Motor Functions:

    • Supplies motor innervation to the muscles of mastication (masseter, temporalis, medial and lateral pterygoid muscles).

    • Also innervates tensor tympani, tensor veli palatini, mylohyoid, and anterior belly of digastric muscles.

MRI Appearance

  • 3D T2-weighted Imaging:

    • The trigeminal nerve appears as a well-defined, hypointense (dark) linear or oval structure within the cerebrospinal fluid (CSF) cisterns, particularly visible in the prepontine cistern as it emerges from the lateral pons.

    • The cisternal segment is best seen on 3D T2 (e.g., FIESTA, CISS, SPACE) due to high CSF-nerve contrast.

    • The nerve is seen traveling toward Meckel’s cave, where it forms the trigeminal (Gasserian) ganglion.

    • The three branches may be individually visualized distally.

  • T1-weighted Imaging:

    • The nerve appears as a small, slightly hypointense or isointense structure relative to brain parenchyma.

    • Less distinct than on T2, but can be seen within the prepontine cistern and Meckel’s cave.

    • The ganglion in Meckel’s cave may show a small hypointense or isointense nodule.

CT Appearance

  • The trigeminal nerve itself is usually not directly visualized on routine CT due to its small size and similar density to surrounding soft tissue.

  • The bony pathways and foramina associated with CN V (superior orbital fissure, foramen rotundum, foramen ovale) are well visualized.

  • Pathological processes (tumors, skull base fractures, bony erosions, or foraminal widening) involving the nerve or its branches may be detected indirectly on CT.

MRI images

Trigeminal nerve (Cranial nerve V) 3T MRI axial image

MRI images

Trigeminal nerve (Cranial nerve V) 3T MRI coronal image

MRI images

Trigeminal nerve (Cranial nerve V) 3T MRI sagittal image 1

MRI images

Trigeminal nerve (Cranial nerve V) 3T MRI sagittal image

MRI image

Trigeminal Nerve (Cranial Nerve V) MRI coronal anatomy image -img-00001-00001