Abstract Number: Esoc2026a358 Severe Hypophosphataemia Mimics Large Vessel Occlusion Syndrome

Background and aims The estimated rate of thrombolysed stroke mimic patients is 17%. We report of a 51y/o male patient (mRS0) presenting with a large vessel occlusion syndrome (LVO) mimic second to severe hypophosphataemia. Methods The patient presented to the A&E department of a UK District General Hospital within 4.5 hours of a witnessed collapse followed by possible GTC seizure/postictal phase and right-sided paralysis. The patient was being investigated for possible hypophosphataemia and taking naproxen for osteoarthritis/chronic back pain. Results Initial GCS was 13/15 (E3V4M6) with right frontal head/right neck pain. The NIHSS was 19 with partial left gaze preference, right visual/sensory inattention, right hemibody paralysis and mild expressive dysphasia/dysarthria. A CT head/angiogram demonstrated ASPECT10 and no evidence of haemorrhage/LVO. Symptoms resolved within 24 h following IV thrombolysis and phosphate (PO4-) replacement for critically low PO4- levels of 0.16 mmol/L. On day 4 of admission, the patient developed rapid right hemibody paralysis following sudden-onset of right-sided headache. PO4- levels were low at 0.58 mmol/L and orally replaced. CT/MRI head scans did not reveal evidence of ischaemic stroke and symptoms resolved within a few hours. We identified naproxen as a possible culprit of low PO4- levels as extended investigations did not yield a plausible cause. We safety-netted the patient with anti-platelet treatment with a view to stop following interval outpatient MRI head scan. Conclusions This case highlights the importance of considering hypophosphataemia as a stroke/LVO mimic in patients with absence of radiological brain changes.