A 26-year-old man is brought to the emergency department by po | Obstetrics & Gynecology

A 26-year-old man is brought to the emergency department by police after he was found disoriented and wandering on the street No medical history is available. The patient is agitated and violent but calms down after several doses of lorazepam and haloperidol. Physical examination reveals confusion and bilateral horizontal nystagmus but no other focal neurologic findings. There are abrasions on the lower extremities. Urine drug screen is positive for phencyclidine. The patient is hospitalized for observation. Several hours later, his agitation and confusion have improved, but he reports difficulty with his vision. Temperature is 37.1 C (98.8 F), blood pressure is 134/84 mm Hg, pulse is 88/min, and respirations are 16/min. On examination, both eyes are deviated superiorly, and extraocular movement is restricted. There is rigidity of the neck and upper extremities. Noncontrast CT scan of the head shows no intracranial hemorrhage.