Presentation of symptoms and clinical history significantly differentiates true acute subarachnoid haemorrhage (SAH)from pseudo-SAH. We report a 25-year-old man who presented with recurrent headaches and has been attending a pulmonologist for recurrent chest infections. Non-Enhanced CT(NECT) of the brain was done, which showed extra-axial sulcal hyper density along cerebral arteries and hyperdense venous sinuses. MR imaging confirmed the linear hypointensity along vessels on susceptibility-weighted images(SWI), suggesting an increased concentration of paramagnetic deoxyhemoglobin within cerebral vessels; findings suggested polycythaemia mimicking SAH. Pseudo SAH is a potential mimic of SAH. Awareness of various manifestations of pseudo-SAH is essential for proper treatment, avoiding unnecessary investigative modalities like angiographic studies, invasive procedures like Lumbar puncture, etc. Polycythaemia presenting as pseudo subarachnoid haemorrhage is a rare differential. Clinical history and MR imaging help to differentiate SAH from pseudo-SAH.
Key words: Pseudo subarachnoid hemorrhage, MRI-SWI sequence, Hypoxia, Haematocrit
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