Re: Trandermal Hyoscine Induced Unilateral Mydriasis
A 4 year old patient with a known diagnosis of a brainstem glioma, ventriculo-peritoneal shunt and ventricular access device was referred to our paediatric district general ward for review following a head injury. She had been knocked over at nursery by her brother on a bicycle and sustained an occipital head injury. Following this, the nursery staff noticed that her pupils were asymmetrical. Mum had collected her from nursery and brought her to the ward. There was no history of loss of consciousness or vomiting. On examination she was very well, bright and playful with a heart rate of 104 and blood pressure 99/56. There was a small, non boggy swelling to her occiput. Her right pupil was a size 6, fixed and dilated. Her left pupil was size 2 with an intact direct and consensual response to light. The accommodation reflex was intact and eye movements were also normal. Fundoscopy showed a slightly blurred optic disc on the right and was difficult to visualise on the left. Neurological examination was otherwise normal for this patient and mum described her as 'the best she has been in ages'. On further discussion of current medication it transpired that the hyoscine patch which had been applied that morning was missing from behind her right ear. The clinical impression was that the head injury was coincidental and that given how clinically well she was, the right sided pupillary findings were most in keeping with topical contamination of the eye with hyoscine presumably by fingertip innoculation. In our literature search for the half life of hyoscine we came across the above BMJ case report. In this report, Hannon et al very helpfully summarise an easy clinical test involving the instillation of Pilocarpine eye drops to establish if a pharmacological blockade is the cause for the underlying pupillary dilatation. We therefore administered pilocarpine and reviewed. Our patient continued to have one fixed and dilated pupil at 30 minutes, confirming pharmacological blockade as the cause of her dilated pupil. This avoided an hour long journey to a tertiary centre, possible general anaesthetic for a CT scan and potential aspiration of ventricular access device. This case reinforces the need for a detailed medication history and the management was significantly improved by the BMJ case report. Case reports remain a very helpful resource for patient management and we were exceptionally grateful to these authors for their thorough and helpful discussion.
Sarah Alexander, Locum Paediatric Consultant Clare Irving, Consultant Paediatrician, Borders General Hospital
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