Ans: C (Bilateral photophobia) Ref: Hcirrisotis principles of Internal Medicine. 18th edition. 2012. Chapter 14. Pg.112Explanation:CLUSTER HEADACHEThe pain is deep, usually retroorbital, excruciating in intensity, nonfluctuating, and explosive in quality.A core feature of cluster headache is Periodicity. At least one of the daily attacks of pain recurs at about the same hour each day for the duration of a cluster bout.The typical cluster headache patient has daily- bouts of one to two attacks of relatively short- duration unilateral pain for 8 to 10 weeks a year; this is usually followed by a pain-free interval that averages a little less than 1 year.Patients are generally perfectly well between episodes.Onset is nocturnal in about 50% of patients, and men are affected three times more often than women.Patients with cluster headache tend to move about during attacks, pacing, rocking, or rubbing their head for relief. This is in sharp contrast to patients with migraine, who prefer to remain motionless during attacks.Cluster headache is associated with ipsilateral symptoms of cranial parasympathetic autonomic activation: conjunctival injection or lacrimation, rhinorrhea or nasal congestion, or cranial sympathetic dysfunction such as ptosis.The sympathetic deficit is peripheral and likely to be due to parasympathetic activation with injury to ascending sympathetic fibers surrounding a dilated carotid artery as it passes into the cranial cavity.When present, photophobia and phonophobia are far more likely to he unilateral and on the same side of the pain, rather than bilateral, as is seen in migraine.Cluster headache is likely to be a disorder involving central pacemaker neurons in the region of the posterior hypothalamusTreatment:Acute Attack TreatmentOxygen inhalation.Sumatriptan 6 mg SC is rapid in onset and will usually shorten an attack to 10-15 minSumatriptan (20 mg) and zolmitriptan (5 mg) nasal spraysOral sumatriptan is not effective for prevention or for acute treatment of cluster headache.Preventive Treatments (See the following table)Neurostimulation TherapyIndicated when medical therapies failDeep-brain stimulation of the region of the posterior hypothalamic gray matter has proven successful in a substantial proportion of patients.