A well-appearing infant with a sudden anisocoria

Case presentationA 10-month-old boy was admitted to the emergency department due to a sudden onset of left unilateral mydriasis (figure 1). His medical history was unremarkable. A minor head trauma 2 days before was reported, without alarming signs or symptoms. His mother was putting him to sleep, after coming back from work, when she noticed a different pupil size and promptly went to the ED with her husband. The parents denied any use of medications, including nebulised therapy or direct contact with plants. The child was well appearing and his vital signs were within the standard age limits. His extraocular motility was normal as well as the rest of his neurological and physical examination. Parents' behaviour was somehow remarkable. Even though the child was not suffering, the mother seemed very worried while the father was nervous and aggressive, repeatedly asking for a discharge.edpract;archdischild-2020-319993v1/F1F1F1Figure 1Left unilateral mydriasis. -: QuestionsWhat is the most likely diagnosis based on this clinical presentation?Local contact with a mydriatic substanceIntracerebral haemorrhageBrain tumourThird nerve palsyWhat would be the next step in the investigation to confirm this diagnosis?Brain CTBrain MRIFundus oculi examinationToxicological screening of urineHow is this condition managed, and what is the prognosis? Answers can be found on page XX .