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Pseudotumor cerebri syndrome secondary to lymecycline therapy

Tetracyclines are a rare but well-recognised cause of raised intracranial pressure. Herein, the first case of pseudotumor cerebri syndrome (PTCS) secondary to lymecycline intake is described. A 28-year-old visually asymptomatic man was referred to the Emergency Department with bilateral disc swelling. He was morbidly obese (BMI 42) and had a past medical history of depression and gout. Although his acne vulgaris had long been in remission, he continued to take daily lymecycline. On examination his visual acuity was 20/16 OD and 20/20 OS. Dilated fundus examination showed bilateral moderate disc swelling in keeping with retinal nerve fibre thickening on OCT (Figure 1). There were no neurological deficits. Cerebral CT/CTV excluded any intracranial mass lesion and venous thrombosis but showed tapered narrowing of the lateral aspects of the transverse sinuses. Lumbar puncture (LP) showed an opening pressure of 36 cmCSFwith normal cerebral spinal fluid (CSF) constituents. A diagnosis of pseudotumor cerebri secondary to tetracycline use (PTCS-T) was made and immediate cessation of lymecycline intake was advised. Five months later the patient’s BMI remained unchanged but his papilloedema had resolved (Figure 2). Optic disc swelling can have many causes. In the context of raised intracranial pressure (ICP) it constitutes papilloedema. Although patients with mild papilloedema usually have normal visual function, patients with more severe papilloedema are at risk of losing sight irreversibly, often in a relatively short period of time. This is because severe and prolonged papilloedema will subject the optic nerve to something analogous to compartment syndrome, which will eventually lead to optic atrophy. Arguably, the most concerning underlying cause of papilloedema is a brain tumour, although other serious causes exist, including intracranial haemorrhage, venous sinus thrombosis and meningitis. However, when neuroimaging is unremarkable and CSF contents are also normal, the term ‘pseudotumor cerebri’, meaning “false brain tumour”, is used to describe this clinical entity. Like some large brain tumours, pseudotumour cerebri (PTC) presents with symptoms of raised ICP, including often, but not always, headache, changes in vision and pulsatile tinnitus. Primary PTC is better known as idiopathic intracranial hypertension (IIH), although given the well-recognised association with obesity, the term ‘idiopathic’ is somewhat misleading. IIH almost exclusively affects young women, and is becoming increasingly common as rates of global obesity rise. Although there are a number of disease-modifying strategies available, including pharmacotherapy (predominantly acetazolamide) as well as surgery (predominantly shunting procedures), the only cure for IIH remains weight loss. Secondary PTC can be due to, amongst other things, venous sinus thrombosis, obstructive sleep apnoea, anaemia, hypoparathyroidism and the use of medications such as vitamin A and the tetracycline class of antibiotics. Although observation of a bulging fontanel in infants on tetracycline therapy was first described in 1961, the exact mechanism by which tetracyclines raise ICP remains unclear. PTCS-T can occur at any age and symptoms of raised ICP usually take weeks to months to develop. When PTC is medication-induced, withdrawal of the