The majority, if not all, of the cases of spontaneous intracranial hypotension result from spontaneous cerebrospinal fluid (CSF) leaks. The disorder has a broad clinical and imaging spectrum with substantial variability in clinical and imaging features, in CSF findings, and in response to treatment. Headache is the most common symptom and is typically orthostatic, but with chronicity the orthostatic features may blur into a chronic, lingering headache. Other clinical features include neck pain, nausea, emesis, interscapular pain, diplopia, dizziness, change in hearing, visual blurring, radicular upper extremity symptoms, and a variety of other, but much less common, manifestations. The most common imaging feature is diffuse pachymeningeal gadolinium enhancement. Other manifestations include imaging evidence of sinking of the brain, subdural fluid collections, enlargement of the pituitary, engorgement of venous sinuses, and engorgement of epidural venous plexus. CSF opening pressure is typically low and CSF analysis may be normal or show increased protein concentration and a primarily lymphocytic pleocytosis. No longer can the entity be simply equated with post-spinal puncture headaches. The pathogenetic core and the independent variable is decrease in CSF volume, whereas clinical imaging and CSF findings, including CSF opening pressures, are all variables dependent on the loss of CSF volume. Many patients respond well to treatment, but some present stubborn therapeutic challenges. A subgroup of patients with orthostatic headaches is gradually recognized who have disorders other than CSF leaks.