Spontaneous Intracranial Hypotension Spontaneous CSF Leaks

MR imaging has truly revolutionized the diagnosis of spontaneous intracranial hypotension (SIH). A substantially larger number of patients are now diagnosed and a broader clinical and imaging spectrum of the disorder is recognized. It is now realized that SIH nearly always results from spontaneous CSF leaks. The majority of these leaks occur at the level of the spine and only rarely at the skull base. Considerable variability exists in clinical manifestations, including the headaches. Although the typical headache is an orthostatic headache, not all headaches in CSF leaks are orthostatic and not all orthostatic headaches are caused by intracranial hypotension or CSF leaks. Furthermore, imaging and CSF findings also reveal considerable variability, including patients who may display CSF opening pressures that are consistently within normal limits or head MRIs that may not show abnormal pachymeningeal enhancement. The core pathogenetic factor is decreased CSF volume (CSF hypovolemia) as the independent variable, while CSF pressures, clinical manifestations, and MRI abnormalities are variable and dependent on loss of CSF volume. Epidural blood patch (EBP) has emerged as the treatment of choice for patients who fail initial conservative measures. However, response to EBP in spontaneous leaks is far less impressive than in post-lumbar puncture headaches. In spontaneous leaks, the anatomy of the leak is frequently complex and quite different from a simple hole or rent as might be seen in post-lumbar puncture headaches. These two entities should not be equated. At least a significant minority of the patients with spontaneous CSF leaks have pre-existing dural weakness, likely based on a disorder of connective tissue matrix. There is also a considerable variability in the rate of leakage of CSF in these patients. This can create diagnostic challenges and novel diagnostic techniques are evolving to address the fast- and slow-flow leaks. A large majority of the patients make excellent recovery spontaneously, with conservative measures, with epidural injections, or surgery. A small minority, however, continue to remain symptomatic. Subdural hematomas may complicate CSF leaks, may become symptomatic, and create therapeutic challenges but, fortunately, uncommonly. Rarely, cerebral venous thrombosis may develop. Sometimes, after treatment of spontaneous CSF leaks, rebound intracranial hypertension may occur which is likely self-limiting.