ANSWER: (A) Cavernous sinus thrombosisREF: khurana 4th ed p. 357Clinical features of cavernous sinus thrombosis:The most common signs of CST are related to anatomical structures affected within the cavernous sinus, notably cranial nerves III-VI, as well as symptoms resulting from impaired venous drainage from the orbit and eye.Classic presentations are abrupt onset of unilateral periorbital edema, headache, photophobia, and bulging of the eye (proptosis).Ptosis, chemosis, cranial nerve palsies (III, IV, V, VI).Sixth nerve palsy is the most common.Sensory deficits of the ophthalmic and maxillary branch of the fifth nerve are common.Papilledema, retinal haemorrhages, and decreased visual acuity and blindness may occur from venous congestion within the retina.Fever, tachycardia and sepsis may be present.Headache with nuchal rigidity may occur. Pupil may be dilated and sluggishly reactive.Infection can spread to contralateral cavernous sinus within 24-48 hours of initial presentation.