Intracranial hypotension syndrome: a review of the magnetic resonance findings

Introduction. Intracranial hypotension syndrome (IHS) is a syndrome with a variable aetiology and clinical presentation that is, in most cases, caused by leakage of cerebrospinal fluid (CSF) through the thecal sac. Orthostatic headache associated to the typical magnetic resonance imaging (MRI) findings, secondary to depletion of CSF, is the key to a correct diagnosis. Aims. To show the imaging findings that, within a suitable clinical context, allow this condition to be identified and diagnosed. Development. Decreased CSF volume plays an important role in INS, which leads to an increase in the compensatory volume of blood, essentially dependent on the venous system. MRI is a sensitive technique in the diagnosis of INS. Yet, separate findings are unspecific. The MRI findings include diffuse and homogeneous dural enhancement, the presence of small bilateral subdural collections, caudal displacement of the encephalic structures (pseudo-Chiari), dilatation of the cortical and medullar veins, and the recent sign of venous distension. This last sign is a highly sensitive finding of IHS, which tends to disappear following the patient's clinical improvement even before the disappearance of the pachymeningeal enhancement, and could be used as a marker for response to treatment. Conclusions. IHS is a condition that is difficult to diagnose clinically for which several typical MRI findings have been reported; both neurologists and radiologists must be familiar with these findings.