 Introduction/Background The clinical syndrome of intracranial hypotension refers to the symptoms caused by cerebrospinal fluid (CSF) hypovolemia and is primarily characterized by postural headaches [1,2]. According to the International Classification of Headache Disorders, third edition, the low CSF pressure headache is typically orthostatic in nature, is caused by low CSF pressure (<6 cm H2O) or CSF leakage, and remits after normalization of CSF pressure or a successful sealing of the CSF leak [3]. The onset of symptoms may be spontaneous or secondary depending on a temporal relation to a presumed cause, such as a recent procedural dural puncture. Headache symptoms may be accompanied by additional symptomatology to include nausea, vomiting, neck pain, tinnitus, changes in hearing, and photophobia [4]. It is estimated that spontaneous intracranial hypotension (SIH) occurs with an incidence of approximately 5 per 100,000 individuals annually [5]. The true incidence of this condition may be higher, because SIH is thought to be both highly underdiagnosed and a misdiagnosed disorder [4,6-8]. Clinical risk factors for the development of SIH include spinal osteophytes that can perforate the dura, weakened ectatic dura/meningeal cysts as can be seen with collagen vascular disease, and a history of bariatric surgery in which it is postulated that rapid loss of epidural fat may weaken the dura and predispose to CSF leakage [4,9-12]. Secondary intracranial hypotension symptoms related to dural puncture are thought to occur with a frequency of approximately 2% to 8% of cases, with risk factors in part related to needle type and gauge used [13-15].
Imaging of Suspected Intracranial Hypotension PCAs.  Introduction/Background The clinical syndrome of intracranial hypotension refers to the symptoms caused by cerebrospinal fluid (CSF) hypovolemia and is primarily characterized by postural headaches [1,2]. According to the International Classification of Headache Disorders, third edition, the low CSF pressure headache is typically orthostatic in nature, is caused by low CSF pressure (<6 cm H2O) or CSF leakage, and remits after normalization of CSF pressure or a successful sealing of the CSF leak [3]. The onset of symptoms may be spontaneous or secondary depending on a temporal relation to a presumed cause, such as a recent procedural dural puncture. Headache symptoms may be accompanied by additional symptomatology to include nausea, vomiting, neck pain, tinnitus, changes in hearing, and photophobia [4]. It is estimated that spontaneous intracranial hypotension (SIH) occurs with an incidence of approximately 5 per 100,000 individuals annually [5]. The true incidence of this condition may be higher, because SIH is thought to be both highly underdiagnosed and a misdiagnosed disorder [4,6-8]. Clinical risk factors for the development of SIH include spinal osteophytes that can perforate the dura, weakened ectatic dura/meningeal cysts as can be seen with collagen vascular disease, and a history of bariatric surgery in which it is postulated that rapid loss of epidural fat may weaken the dura and predispose to CSF leakage [4,9-12]. Secondary intracranial hypotension symptoms related to dural puncture are thought to occur with a frequency of approximately 2% to 8% of cases, with risk factors in part related to needle type and gauge used [13-15].