Spontaneous intracranial hypotension typically results from spontaneous cerebrospinal fluid (CSF) leak, often at spine level and only rarely from skull base. Once considered rare, it is now diagnosed far more commonly than before and is recognized as an important cause of headaches. CSF leak leads to loss of CSF volume. Considering that the skull is a rigid noncollapsible container, loss of CSF volume is typically compensated by subdural fluid collections and by increase in intracranial venous blood which, in turn, causes pachymeningeal thickening, enlarged pituitary, and engorgement of cerebral venous sinuses on magnetic resonance imaging (MRI). Another consequence of CSF hypovolemia is sinking of the brain, with descent of the cerebellar tonsils and brainstem as well as crowding of the posterior fossa noted on head MRI. The clinical consequences of these changes include headaches that are often but not always orthostatic, nausea, occasional emesis, neck and interscapular pain, cochleovestibular manifestations, cranial nerve palsies, and several other manifestations attributed to pressure upon or stretching of the cranial nerves or brain or brainstem structures. CSF lymphocytic pleocytosis or increase in CSF protein concentration is not uncommon. CSF opening pressure is often low but can be within normal limits. Stigmata of disorders of connective tissue matrix are seen in some of the patients. An epidural blood patch, once or more, targeted or distant, at one site or bilevel, has emerged as the treatment of choice for those who have failed the conservative measures. Epidural injection of fibrin glue of both blood and fibrin glue can be considered in selected cases. Surgery to stop the leak is considered when the exact site of the leak has been determined by neurodiagnostic studies and when less invasive measures have failed. Subdural hematomas sometimes complicate the CSF leaks; a rebound intracranial hypertension after successful treatment of a leak is not rare. Cerebral venous sinus thrombosis as a complication is fortunately less common, and superficial siderosis and bibrachial amyotrophy are rare. Short-term recurrences are not uncommon, and long-term recurrences are not rare.