Stimulation of a branch of the trigeminal nerve (cranial nerve V) can result in bradycardia. This is termed the trigeminocardiac reflex (TCR).
Mechanism: Nerve impulses to the trigeminal nucleus trigger the vagal nucleus. Vagal efferent pathway cause a cardiac depressor response.
Branches of the trigeminal nerve:
(1) ophthalmic (V1)
(2) maxillary (V2)
(3) mandibular (V3).
The most common type of TCR is the oculocardiac reflex (see 19.43.01) associated with stimulation of the ophthalmic branch (CV1).
Stimulation of other branches of the trigeminal nerve can occur in:
(1) temporomandibular joint arthrotomy
(2) facial surgery
(3) cerebellopontine angle surgery
(4) skull base surgery
(5) pituitary fossa surgery
(6) microvascular trigeminal decompression
(7) trigeminal neuralgia
Effects of the TCR:
(1) bradycardia
(2) variable hypotension
(3) variable sinus arrest
(4) syncope
(5) variable nausea and vomiting
