Some injuries to the cervical sympathetic plexus cause cervical sympathetic hyperactivity rather than the hypoactivity seen in Horner's syndrome (see above). This was first described by Pourfour du Petit in the 18th Century who studied soldiers with cervical sword wounds acquired during the Napoleonic Wars.


Neural pathways: as for Horner's syndrome (see previous algorithm)


Clinical features on side ipsilateral to the injury:

(1) unilateral mydriasis

(2) widening of the palpebral fissure

(3) exophthalmos

(4) facial skin that is cool and pale and which shows increased sweating


The syndrome occurs when sympathetic fibers of the papillary pathway are stimulated anywhere between the hypothalamus and pupil.


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