nervus intermedius

The nervus intermedius, also known as intermediate nerve of Wrisberg, is a part of the facial nerve (CN VII) which contains somatic sensory, special sensory, and visceral motor (secretomotor) fibers .

Gross anatomy

Nuclei

• superior salivatory nucleus 
  • forms the parasympathetic root (general visceral efferent) of the nerve and supplies the motor component of the greater petrosal and chorda tympani nerves
    • lacrimal and nasal glands via the greater petrosal nerve via the pterygopalatine ganglion
    • submandibular and sublingual glands via the chorda tympani nerve via the submandibular ganglion
• solitary nucleus (nucleus tractus solitarii) 
  • central processes of pseudo-unipolar cell bodies in the geniculate ganglion enter the gustatory part of the solitary nucleus forming the special visceral afferent root of the nerve
  • peripheral processes of these cells receive taste sensation from the anterior two-thirds of the tongue (via chorda tympani) and the palate (via greater petrosal nerve)
• main sensory nucleus of the trigeminal nerve
  • cell bodies of general somatic afferents also dwell in the geniculate ganglion
  • they furnish sensory information pertaining to the posterior aspect of the external auditory auditory canal, mastoid, and lateral pinna

Course

The nervus intermedius exits the brainstem at the boundary between the pons and the inferior cerebellar peduncle lateral to the motor root of the facial nerve and medial to the vestibulocochlear nerve (in close proximity to the pontomedullary junction). It travels with the motor root of the facial nerve through the cerebellopontine angle towards the internal acoustic meatus where it enters the anterior superior quadrant to travel through the petrous temporal bone. At the geniculate ganglion (at the first genu) it joins the motor root of the facial nerve .

Branches

Branches of the facial nerve including :

• greater (superficial) petrosal nerve to the pterygopalatine ganglion
• chorda tympani to the submandibular ganglion
• tympanic branches

Radiographic features

MRI

• not visible on CT or 1.5 T MRI
• best appreciated on axial 3 T MRI through the cerebellopontine angle traveling towards the internal acoustic canal 

Related pathology

• facial nerve schwannoma
• nervus intermedius neuralgia

History and etymology

First documented by German anatomist Heinrich August Wrisberg (1736-1808) in 1777, although likely first described by Eustachius in 1563 .

Siehe auch:

• Nervus facialis