The nervus terminalis, also referred to as cranial nerve zero, cranial nerve XIII, zero nerve, nerve N or NT, is a previously unnumbered cranial nerve, most rostral of all cranial nerves.
It is a bilateral bundle of nerve fibres, which runs in the subarachnoid space from the medial olfactory stria on the inferior surface of the frontal lobe, to and through the cribriform plate, to the nasal septum. It runs medially to the olfactory nerve, over the surface of the gyrus rectus.
The terminal nerve originates from the neural crest, distinct and separate from the olfactory nerve (which originates in the nasal placode).
Whilst not mentioned in recent editions of anatomy textbooks by Last or Gray, the nervus terminalis carries a number of key functions: in embryogenesis it acts as a migration route for LHRH cells and as such is probably implicated in pathogenesis of Kallman syndrome.
In adults, based on animal studies, the nerve may be involved in reproductive behaviour consisting of modulatory neurons.
High-resolution modern MRI scanners that achieve voxel size of 0.6-0.7 mm should be able to adequately display the nerve and assess for its lesions. Cohort serial studies demonstrating this are pending.
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