Pseudotumour cerebri (PTC), or idiopathic intracranial hypertension (IIH), is a condition of increased intracranial pressure (ICP) without clinical, laboratory or radiological evidence of intracranial pathology. IIH is deemed a diagnosis of exclusion. The original diagnostic criteria were formulated in 1937 by Walter Dandy, 1 who described benign intracranial hypertension as the presence of increased ICP, normal cerebrospinal fluid (CSF) findings and no sign of a brain tumour on ventriculography. Corbett and Thompson 2 later removed the adjective benign and substituted idiopathic in light of the potential for devastating loss of vision.The name idiopathic intracranial hypertension indicates a condition with unknown aetiology. Over the years, a multitude of IIH cases and coinciding conditions and medications have been reported, many of which may have arisen by chance. [3][4][5][6][7] Hormone use has been implicated in many of these reports. Several studies have sought to evaluate the existence of these proposed associations; however, apart from obesity, no convincing evidence exists. CASE SUMMARYA 23-year-old trans-gendered male presented with a persistent headache for the past two months. The headache was worse in the morning, non-localised and exacerbated by coughing, yawning and supine positioning. In addition, for the past two weeks he had noted black spots in his vision as well as bilateral transient visual loss. The visual symptoms intensified with positional change, lasted no more than one minute, were more prominent in the peripheral visual field and were not accompanied by any photopsia. The patient denied having any numbness, extremity weakness, diplopia, nausea or vomiting. Furthermore, he reported no recent antibiotic use or changes in weight. Our patient presented with a body mass index (BMI) of 27.05, which is above the ideal BMI range of 18.5 to 25. He was currently taking testosterone cypionate intramuscularly on a weekly basis, prescribed by his endocrinologist as part of gender reassignment management. Past medical history was significant for a bilateral mastectomy.Visual acuity was 6/6 in the right eye and 6/6 in the left eye. Pupils were equal and reactive to light with no afferent pupillary defect. Colour vision, ocular motility, and Humphrey visual field testing were normal. Neurological screening revealed cranial nerves II through XII to be grossly intact. Intraocular pressures taken by Goldmann tonometry were 15 mmHg and 17 mmHg in the right and left eyes, respectively. The dilated fundus examination revealed florid bilateral disc oedema with flame-shaped haemorrhages and hard exudates (Figure 1). Optical coherence tomography (OCT) further supported the diagnosis of bilateral optic disc oedema (Figure 2).The patient was immediately referred for magnetic resonance imaging (MRI) and scheduled for neurological consultation. The MRI revealed a small Chiari I malformation as demonstrated by the cerebellar tonsils projecting below the level of the foramen magnum. Because no mass or lesion was fo...