Conclusion
From this extensive review, several conclusions can be drawn:
SIH almost always results from spontaneous CSF leaks. The past theories of increased CSF absorption or decreased CSF production have never been substantiated. The disorder is far more common than was believed only one or two decades ago.
The overwhelming majority of spontaneous CSF leaks occur at the level of the spine, particularly the thoracic spine. Spontaneous leaks at the skull base do occur but only rarely.
Spontaneous CSF leaks can no longer be equated with postpuncture headaches. There is considerable variability in clinical presentations, imaging findings, and CSF findings including CSF pressures that can be within normal limits. CSF volume depletion (CSF hypovolemia) rather than decreased CSF pressure appears to be the pathogenetic core as the independent variable. CSF pressures, clinical manifestation, and MRI abnormalities are variables dependent on the CSF volume. The term "SIH" no longer appears broad enough to embrace all of these variables. Terms such as CSF volume depletion or CSF hypovolemia have appeared in the literature and have been used interchangeably with spontaneous CSF leak.
The anatomy of spontaneous CSF leaks is often complex and different from a simple hole or a rent. It is typically not the same as what is encountered in CSF leaks resulting from LP, epidural catheterization, or craniospinal surgeries.
Clinical stigmata of disorders of connective tissue matrix can be seen in a significant minority of the patients with spontaneous CSF leaks. This very likely plays a role in the weakness of the dural sac, formation of meningeal diverticula, and pathogenesis of the disorder.
Not all headaches in spontaneous CSF leaks are orthostatic and not all orthostatic headaches result from CSF leaks.
Sometimes after treatment of CSF leak, whether by EBP or surgery, a rebound increased intracranial pressure may occur, which is often self-limiting but sometimes may require treatment.
The rate of CSF leakage in spontaneous CSF leaks may vary considerably. Fast-flow and slow-flow leaks each present special diagnostic challenges. Novel diagnostic techniques have been quite helpful in locating the site of the leak in fast-flow leaks. Locating the site of slow-flow leaks remains challenging.
EBP has emerged as treatment of choice when initial conservative measures including time have failed. These may be targeted or blind (presumed distant from an undetermined leak site) or single level or bilevel. Epidural injection of fibrin glue also has utility in selected cases. Combined EBP and fibrin glue injections have also been tried but it needs special considerations.
Surgery aimed at stopping the leakage is often undertaken when less invasive measures (such as EBP) have failed. It is essential to determine the site of the leak by appropriate imaging before surgery is undertaken.