Subarachnoid haemorrhages are where there is an extravasation of blood into the space between the arachnoid and pia. Subarachnoid haemorrhages often develop as a result of rupture of a cerebral aneurysm (most often arising from the circle of Willis or the middle cerebral artery bifurcation) or consequent ...

A lumbar puncture (LP, also known as a spinal tap) is a diagnostic and at times, therapeutic medical procedure. Diagnostic indications The main diagnostic indications of performing a LP is for collection and evaluation of cerebrospinal fluid (CSF) for diagnosis and exclusion of infectious, inflammatory ...