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Deep Petrosal Nerve

nervus petrosus profundus

The deep petrosal nerve consists of postganglionic sympathetic fibres from the superior cervical ganglion that travel along the internal carotid artery plexus. It passes through the foramen lacerum and joins the greater petrosal nerve to form the nerve of the pterygoid canal (Vidian nerve). Through this union, sympathetic vasoconstrictive fibres reach the nasal mucosa and the lacrimal gland, counterbalancing the parasympathetic vasodilatory and secretory effects of the greater petrosal nerve.

Region: Head & Skull

Clinical Relevance

Clinical Notes

The deep petrosal nerve and its sympathetic fibres are relevant in head and neck pathology affecting the internal carotid sympathetic plexus. Horner syndrome from internal carotid artery dissection involves loss of sympathetic supply at the level of the deep petrosal nerve, producing partial anhidrosis of the face (confined to the medial forehead since the external carotid supplies the lateral face sympathetically) along with miosis and ptosis. Vidian neurectomy, dividing the nerve of the pterygoid canal, reduces excessive nasal secretion in vasomotor rhinitis by interrupting the parasympathetic pathway while the sympathetic is already partially preserved.

Pathology

Common Injuries & Conditions

Carotid Dissection Partial Horner Syndrome

Dissection of the internal carotid artery disrupts the sympathetic plexus at the deep petrosal nerve level, producing a partial Horner syndrome with miosis and ptosis but typically preserved facial sweating (as the external carotid carries facial sympathetics), with ipsilateral head or neck pain and stroke risk from embolism.