Version May 2024
INTRODUCTION — Intracranial hypotension occurs when imbalance in the production, absorption, or flow of cerebrospinal fluid (CSF) leads to low intracranial pressure and sagging of the brain within the skull. The resultant traction on connected nerves and other structures can cause a clinical syndrome often described by postural headaches, but nonpostural headaches and other neurologic symptoms may also occur.
Intracranial hypotension most commonly occurs from a persistent CSF leak after lumbar puncture but may also be spontaneous.
This topic will review the pathophysiology, clinical features, and diagnosis of spontaneous intracranial hypotension. The treatment and prognosis of spontaneous intracranial hypotension are discussed separately. (See "Spontaneous intracranial hypotension: Treatment and prognosis".)
Post-dural puncture headache is reviewed elsewhere. (See "Post dural puncture headache".)
PATHOPHYSIOLOGY — In 1898, Dr. August Bier, an early contributor to the field of spinal anesthesia, developed and was the first to report post–lumbar puncture (LP) headache [1]. He proposed that ongoing leakage of cerebrospinal fluid (CSF) through the dural puncture site was the cause of the headache. This belief is still held today. It is thought that leakage of CSF through the dural rent made by the LP needle exceeds the rate of CSF production, resulting in low CSF volume and pressure [2]. (See "Post dural puncture headache", section on 'Pathophysiology'.)
Spontaneous intracranial hypotension was first proposed as a clinical syndrome in 1938 [3]. It was initially called aliquorrhea and featured a postural headache virtually identical to that following LP [3,4].
Historically, several other terms have been used to describe spontaneous intracranial hypotension:
●Spontaneous (or idiopathic) low CSF pressure headache
●Low CSF volume headache
●Hypoliquorrhoeic headache
●CSF leak headache
●CSF hypovolemia
●CSF volume depletion
The prevailing theory for the etiology of spontaneous intracranial hypotension is that CSF leakage located in the spine occurs in the context of disruption of the meninges [5,6]. An underlying connective tissue disorder may result in dural weakness and play a role in the development of spontaneous low CSF pressure, as suggested by studies reporting connective tissue abnormalities in patients with spontaneous CSF leaks [7,8] and others identifying deficient fibrillin, elastin, or both in dermal fibroblast cultures from such patients [9].
Cause of headache symptoms — As the CSF pressure decreases, there is a reduction in the buoyancy of the brain's supportive cushion. As a result, the brain "sags" in the cranial cavity, causing traction on the anchoring and supporting structures of the brain [10-13]. Traction on pain-sensitive intracranial and meningeal structures, particularly the sensory nerves and bridging veins, is thought to cause headache and some of the associated symptoms of spontaneous intracranial hypotension [12]. The postural component of the headache is attributed to accentuated traction in the upright position due to gravity. Secondary vasodilation of the cerebral veins to compensate for the low CSF pressure may contribute to the vascular component of the headache by increasing brain volume [11]. Because jugular venous compression increases headache severity, venodilation is likely a contributing factor to the headache.
CSF hypovolemia, rather than CSF hypotension per se, has been proposed as the underlying cause of the headache syndrome [14], as some patients with normal CSF pressure have been described who have clinical and radiographic features typical of orthostatic headache [14-18]. In this paradigm, the CSF pressures, clinical manifestations, and imaging abnormalities of the syndrome are thought to be variables dependent on CSF volume [19,20]. Some authors [21] have therefore advocated the name "CSF hypovolemia syndrome" for the constellation of symptoms associated with CSF leakage.
An alternative hypothesis to explain the headache is that loss of CSF results in distal pooling due to an increased compliance at the caudal end of the spinal CSF space [22]. This explanation is compatible with the observation that spinal sites of CSF leakage commonly produce orthostatic headache, whereas cranial sites of CSF leakage (eg, seen with spontaneous CSF rhinorrhea or CSF otorrhea) rarely, if ever, do so.
Causes of CSF leak — The three main sources for CSF leak are tear of the spinal dural membrane, rupture of a meningeal diverticulum, and development of a CSF-venous fistula (figure 1) [23].
●Dural tears may occur spontaneously or after trivial trauma, often in the setting of degenerative disc disease, osseous spurs, or thoracic dorsal osteophytes [24-28].
●Meningeal diverticula may form spontaneously or after healing of a dural tear and may occur along the spinal column or at the dural root sleeve [29]. Meningeal diverticula have been associated with connective tissue abnormalities, including Marfan syndrome [8,30].
●CSF-venous fistula is an abnormal communication to the vascular system that allows CSF to drain from the subarachnoid space directly into adjacent spinal epidural and paraspinal veins in the absence of a dural defect [31,32]. This subtype has been increasingly recognized with the advancement of diagnostic imaging techniques.
The onset of a CSF leak may be triggered by an inciting event, including a fall, a sudden twist or stretch, sexual intercourse or orgasm, a sudden sneeze, sports activity, or "trivial trauma" [33]. These relatively minor events may cause rupture of spinal epidural cysts (formed during fetal development) or perineural (Tarlov) cysts or may cause a tear in a dural nerve sheath [5] with resultant cryptic CSF leakage.
●Classification – A comprehensive classification system was developed to categorize CSF leaks based on their underlying cause and the presence or absence of extradural CSF on spinal imaging. These subtypes and their frequencies were identified in a review of 568 patients with spontaneous intracranial hypotension [34]:
•Type 1 CSF leaks result from a dural tear (image 1) and accounted for 27 percent of cases. Nearly all were associated with an extradural CSF collection. Type 1a CSF leaks along the ventral thecal surface predominated (96 percent) over type 1b leaks along the dorsal surface (4 percent).
•Type 2 CSF leaks result from meningeal diverticula (image 2) and accounted for 42 percent of leaks. An extradural CSF collection was found in 22 percent of these patients. Type 2a represented simple diverticula (91 percent) and type 2b complex meningeal diverticula/dural ectasia (9 percent).
•Type 3 CSF leaks result from direct CSF-venous fistulas and accounted for 2.5 percent of cases. Type 3 leaks were not associated with extradural CSF collections.
•Type 4 CSF leaks are of indeterminate source and accounted for 29 percent of cases. Extradural CSF collections were found in 52 percent of patients with type 4 leaks.
Spinal location — The location of CSF leaks associated with spontaneous intracranial hypotension is almost exclusively spinal; most occur at the thoracic or cervicothoracic junction. Few, if any, cases result from CSF leaks at the skull base [18]. As an example, one series evaluated 273 patients with spontaneous intracranial hypotension, and none had evidence of a cranial CSF leak [35].
Cranial CSF leaks that occur at the skull base, typically in the petrous or ethmoidal regions or through the cribriform plate, may cause CSF otorrhea or rhinorrhea and clinical features distinct from spontaneous intracranial hypotension. Cranial CSF leaks may result from sustained intracranial hypertension as occurs in idiopathic intracranial hypertension [36-38]. (See "Idiopathic intracranial hypertension (pseudotumor cerebri): Epidemiology and pathogenesis" and "Idiopathic intracranial hypertension (pseudotumor cerebri): Clinical features and diagnosis".)
EPIDEMIOLOGY — There are few data regarding the incidence of spontaneous intracranial hypotension. The estimated annual incidence is 4 to 5 per 100,000 [39,40]. In a 2021 systematic review of published cohort studies, the following observations were made [41]:
●The mean age of patients was 43 years with a range from 2 to 88 years of age.
●The proportion of female individuals was 63 percent.
Although data are limited, possible risk factors for spontaneous intracranial hypotension include connective tissue abnormalities, spinal pathologies, and bariatric surgery [41-43]. (See 'Causes of CSF leak' above.)
CLINICAL FEATURES — Postural headache is usually, but not always, the major manifestation of spontaneous intracranial hypotension [6,23]. Infrequently, patients report no headache, typically when other symptoms of low cerebrospinal fluid (CSF) pressure are evident [39,41]. (See 'Associated symptoms' below.)
The neurologic examination is often normal in patients with spontaneous intracranial hypotension [44]. However, various neurologic symptoms and signs may be present. (See 'Associated symptoms' below.)
Headache — Headache attributed to spontaneous intracranial hypotension may be of sudden or gradual onset. The headache ordinarily develops within two hours, and in most cases within 15 minutes, of sitting or standing [45]. Rarely, it starts as a thunderclap headache [29]. (See "Overview of thunderclap headache".)
The typical headache with this syndrome is often described as throbbing or a dull pain that may be generalized or focal. The headache severity is widely variable and ranges from mild to incapacitating [39]. Frontal head pain is reported by patients as often as occipital and diffuse pain [33,41].
●Classic orthostatic features – At symptom onset, headache typically occurs upon sitting or standing upright and relief is obtained with recumbency, usually within minutes. In rare cases associated with an asymmetric cervical CSF leak, headache relief occurs only with lying on one side of the body [46]. The headache is seldom relieved with analgesics. Exacerbating factors include erect posture, head movement, coughing, straining, sneezing, jugular venous compression, and high altitude [47]. Orthostatic character of the headache may wane as symptoms become chronic.
●Alternative headache patterns – While headache attributed to spontaneous intracranial hypotension is characteristically orthostatic, other patterns can occur [18,48]:
•Chronic daily headache may replace an orthostatic pattern as symptoms become chronic [20,29]. On occasion, the postural component may not be present at all.
•Paradoxical headache, worse with recumbency and better with the upright position, has been reported in rare patients with spontaneous low CSF pressure [49,50].
•A diurnal headache characterized by onset late in the day may be reported by patients with a low-volume ("slow-flow") CSF leak or leaks that have slowed due to chronicity or treatment. A clear orthostatic character may be inapparent as headaches are usually absent despite upright posture through the early morning. Symptoms begin in late morning or early afternoon but do typically increase in severity as more time is spent upright [51].
•Intermittent headaches with headache-free intervals of varying duration may occur in patients with intermittent CSF leaks.
•In other cases, the headache can mimic a primary headache syndrome, such as primary cough headache [52] or primary exertional headache [53]. These primary headache syndromes are discussed separately. (See "Primary cough headache" and "Exercise (exertional) headache".)
Headache attributed to spontaneous intracranial hypotension may resolve spontaneously within two weeks or with successful treatment [44]. In some cases, it lasts months or years.
Associated symptoms — In 1825, Magendie described vertigo and unsteadiness in a patient following the removal of CSF [54]. Today, the list of reported associated symptoms is varied and extensive [6,39,41]. In a systematic review including 32 articles and 1531 patients, the most common associated symptoms of spontaneous intracranial hypotension were [41]:
●Nausea or vomiting – 51 percent
●Neck pain or stiffness – 33 percent
●Tinnitus – 19 percent
●Dizziness – 14 percent
Other associated symptoms include the following [2,14,33,39,41,55-57]:
●Change in hearing (eg, hyperacusis, echoing, or tinnitus)
●Photophobia
●Other visual disturbances (eg, blurred vision, diplopia, visual obscurations)
●Vertigo
●Diaphoresis
●Anorexia
●Limb weakness
●Unsteadiness or staggering gait
●Back pain
●Hiccups
●Dysgeusia
Cognitive deficits have also been associated with spontaneous intracranial hypotension including cases of reversible frontotemporal dementia attributed to low CSF pressure [39,58,59]. Another report described eight patients with "frontotemporal brain sagging syndrome" (FBSS) who presented with progressive behavioral symptoms and cognitive dysfunction suggestive of behavioral variant frontotemporal dementia [60]. Treatments directed at intracranial hypotension led to improvement in a few patients. Frontotemporal dementia is discussed separately. (See "Frontotemporal dementia: Clinical features and diagnosis".)
Uncommon severe manifestations — Some patients with spontaneous intracranial hypotension may present infrequently with more severe symptoms or findings on imaging associated with caudal descent and compression of brainstem structures.
●Signs and symptoms
•Ataxia (posterior fossa) [61]
•Quadriparesis (brainstem and upper cervical spinal cord) [50]
•Movement disorders including parkinsonism, tremor, chorea, and dystonia (deep midline structures) [61-63]
•Hypoactive-hypoalert behavior, including apathy and akinetic mutism (pons and midbrain) [64]
•Decreased level of consciousness, stupor, and coma (diencephalon) [65-67]
•Galactorrhea and hyperprolactinemia (pituitary stalk) [68]
•Abducens nerve palsy (pontomedullary junction) [69]
●Imaging findings
•Acute subdural hematoma (image 3) [70-73]
•Cerebellar hemorrhage (cerebellar bridging veins) [50]
•Posterior circulation infarction (deformation of cerebral arteries) [74-76]
•Cerebral venous sinus thrombosis [77]
•Reversible posterior leukoencephalopathy syndrome (also known as posterior reversible encephalopathy syndrome or PRES) [78,79]
•Reversible cerebral vasoconstriction syndrome [80]
•Superficial siderosis [78,81-84]
Except for hemorrhage and infarction, these manifestations are typically reversible with successful treatment of the CSF leak. The role of anticoagulation in cerebral venous sinus thrombosis treatment in the setting of spontaneous intracranial hypotension remains uncertain, and potential benefits must be weighed against risks of hemorrhage, particularly for patients with subdural fluid collections. (See "Cerebral venous thrombosis: Treatment and prognosis", section on 'Acute antithrombotic management'.)
EVALUATION AND DIAGNOSIS — The diagnosis of spontaneous intracranial hypotension should be considered in patients who present with positional orthostatic headache not caused by dural puncture, with or without other neurologic symptoms [39,85]. Headache caused by low cerebrospinal fluid (CSF) pressure following a dural puncture rarely creates a diagnostic dilemma.
In addition, the diagnosis of spontaneous intracranial hypotension should also be considered in patients undergoing magnetic resonance imaging (MRI) of the brain to evaluate for headache or other neurologic symptoms when imaging findings are suggestive of spontaneous orthostatic hypotension. (See 'Brain MRI' below.)
Diagnosis — The diagnosis of spontaneous intracranial hypotension is made in patients with headache, typically orthostatic in quality, with or without associated symptoms, and with evidence on imaging of CSF leak or low CSF pressure (algorithm 1). (See 'Clinical features' above and 'Initial diagnostic neuroimaging' below and 'Additional neuroimaging when initial studies are nondiagnostic' below.)
Diagnostic criteria — The diagnostic criteria for headache attributed to spontaneous intracranial hypotension, as delineated by the International Classification of Headache Disorders, 3rd edition (ICHD-3) are as follows [86]:
●(A) Any headache fulfilling criterion C
●(B) Either or both of the following:
•Low CSF pressure (<60 mmH20)
•Evidence of CSF leakage on imaging
●(C) Headache has developed in temporal relation to the low CSF pressure or CSF leakage or has led to its discovery
●(D) Not better accounted for by another ICHD-3 diagnosis
Our approach — For patients with symptoms suggestive of spontaneous orthostatic hypotension, we perform MRI of the brain and spine to assess for imaging evidence suggestive of low CSF pressure, in agreement with consensus clinical guidelines [85]. Additional neuroimaging and measurement of opening pressure by lumbar puncture may be required to identify or help exclude the diagnosis of spontaneous intracranial hypotension.
●Brain MRI may show findings consistent with "brain sagging" and can help exclude alternative causes to neurologic symptoms. (See 'Brain MRI' below.)
●Spinal MRI may show extradural CSF suggestive of an adjacent leak. (See 'Spine MRI' below.)
●Additional neuroimaging may be required for some patients who have nondiagnostic or normal initial brain and spine neuroimaging. (See 'Additional neuroimaging when initial studies are nondiagnostic' below.)
Direct evidence of low CSF pressure may be identified by measuring CSF opening pressure during a diagnostic lumbar puncture (LP) or assessed during dural puncture required for intrathecal contrast. However, LP may cause a post-dural puncture headache and aggravate preexisting symptoms or introduce confounding clinical features. In addition, CSF pressure may be normal even in the presence of an active leak. Diagnostic LP is typically reserved for suspected cases of spontaneous intracranial hypotension where neuroimaging is nondiagnostic. (See 'The role of lumbar puncture' below.)
Once the diagnosis is confirmed, the need for further evaluation to confirm the exact site of the CSF leak is driven by the response to therapy. This is discussed in greater detail separately. (See "Spontaneous intracranial hypotension: Treatment and prognosis", section on 'Imaging evaluation to identify site of leak'.)
For other patients whose diagnostic evaluation shows no evidence of low CSF pressure or CSF leak, we evaluate for alternative diagnostic entities. (See 'Differential diagnosis' below.)
Initial diagnostic neuroimaging — We perform MRI with gadolinium contrast of the brain and spine as the initial studies for confirming the diagnosis of spontaneous intracranial hypotension. MRI may be performed without contrast for patients unable to receive gadolinium due to a contraindication or kidney failure.
The utility of head computed tomography (CT) for confirming the diagnosis is limited, as head CT is often normal in patients with spontaneous intracranial hypotension. However, findings on head CT may suggest the diagnosis by demonstrating subdural fluid collections, slit-shaped ventricles, tight basal cisterns, scant CSF over the cortex, or increased tentorial contrast enhancement [39].
Neuroimaging studies are generally not performed in patients with post-lumbar puncture headache, where the diagnosis is more obvious. (See "Post dural puncture headache".)
Brain MRI — Brain MRI with gadolinium is the most sensitive test for identifying spontaneous intracranial hypotension [87]. In a meta-analysis of 28 studies including 2078 patients with spontaneous intracranial hypotension, abnormal findings on brain MRI were found in 81 percent [41]. Several imaging features have been described including [15,41,54,88-93]:
●Diffuse pachymeningeal enhancement (image 4 and image 5)
●Subdural hygromas or hematomas (image 3)
●Engorgement of the dural venous sinuses (image 6)
●Brainstem descent with cerebellar tonsillar herniation (image 7)
●Pituitary enlargement (image 3 and image 5)
●Paucity of fluid in perioptic nerve sheaths and dilated superior ophthalmic veins (image 5)
●Reduced diameter of suprasellar and prepontine cisterns (image 7 and image 8)
●Increased anteroposterior diameter of the midbrain (image 5)
The acronym SEEPS (for Subdural fluid collections, Enhancement of the pachymeninges, Engorgement of the venous structures, Pituitary enlargement, and Sagging of the brain) recalls major features of spontaneous intracranial hypotension on brain MRI [39].
The most common abnormality on brain MRI is diffuse pachymeningeal enhancement, found in nearly 75 percent of patients with intracranial hypotension (image 4) [15,41]. Pachymeningeal enhancement is believed to occur when lowered CSF pressure leads to accumulation of gadolinium in dilated dural venous sinuses. It involves the pachymeninges diffusely, spares the leptomeninges, and does not involve the cortical sulci or around the brainstem [15,94-96]. It is typically contiguous (without skip areas), smooth, and involves both supratentorial and infratentorial compartments. The enhancement is often thick and obvious but sometimes can be quite thin. Diffuse pachymeningeal enhancement may improve or resolve over time or with resolution of the headache [97].
Other features on brain MRI are variously found in approximately one-third up to one half of patients [41].
Rarely, brain MRI may show swelling of the upper brainstem and diencephalon without pachymeningeal enhancement or other more common features [98]. The upper brainstem swelling is hypothesized to be a manifestation of venous stagnation caused by downward stretching of the vein of Galen, which results in a functional stenosis where the vein of Galen joins the straight sinus. This results in a narrowing of the midbrain-pons angle, which has been associated with a poorer response to spontaneous intracranial hypotension treatment [99] and can be used as an indicator of spinal CSF leakage severity (image 8) [100].
Spine MRI — MRI of the spine without gadolinium is typically performed along with brain MRI to identify features suggestive of CSF leak. A meta-analysis of 14 studies that included 406 patients found spinal MRI was abnormal in 48 percent (effect size 95% CI 0.3-0.6) [41].
Imaging features on MRI of the spine in patients with spontaneous intracranial hypotension include [101,102]:
●Epidural fluid collections (image 1 and image 8)
●Collapse of the dural sac (image 8)
●Engorgement of the epidural venous plexus (image 8)
●Meningeal diverticula (image 2)
In a series of 10 female patients who had characteristic orthostatic headache without a previous history of dural tear, spinal MRI revealed dilated cervical epidural veins [21]. The authors concluded that this finding is an indicator of CSF hypovolemia and can be used to differentiate spontaneous low CSF pressure from the other causes of diffuse pachymeningeal enhancement.
Additional neuroimaging when initial studies are nondiagnostic — We perform additional diagnostic imaging such as noninvasive MR myelography and radioisotope cisternography when clinical suspicion is high despite nondiagnostic initial neuroimaging. In addition, further imaging may be performed to exclude the diagnosis for patients with atypical symptoms or abnormal imaging findings of uncertain cause. As examples, additional testing may be warranted when brain MRI shows isolated pachymeningeal enhancement in a patient with nonorthostatic headaches or to establish that evidence of cerebellar tonsillar herniation is due to intracranial hypotension rather than a Chiari malformation.
In addition, we perform additional diagnostic imaging when initial brain and spine MRI are normal but clinical suspicion for the diagnosis is high, such as for patients with severe characteristic postural headache. While brain or spine MRI is abnormal in most patients, a systematic review of patients with spontaneous intracranial hypotension estimated that brain MRI remains normal in up to 20 percent and spinal MRI can be normal in more than 50 percent [39,41].
Noninvasive MR myelography — We perform noninvasive MR myelography when initial brain and spine MRI are nondiagnostic. Many imaging modalities to assess the spinal canal by myelography require contrast infusion via dural puncture. Noncontrast MR myelography using heavily T2-weighted three-dimensional sequences is performed without a dural puncture or intravenous gadolinium contrast and may be an effective technique to diagnose spontaneous intracranial hypotension [23,103,104]. It may show extradural fluid collections or structural causes such as meningeal diverticula. Noninvasive MR myelography does not expose patients to radiation and is typically a quicker study to perform than myelography with intrathecal injection. In addition, it does not carry the adverse risks of causing a CSF leak from dural puncture or potential adverse reactions to intrathecal gadolinium associated with myelography performed with intrathecal injection.
The sensitivity of noninvasive MR myelography was compared with CT myelography with intrathecal contrast in a registry of 667 patients with spontaneous intracranial hypotension who underwent both studies [105]. Extradural fluid collections were found in 276 patients (48 percent). Overall diagnostic agreement was 99 percent; of the 276 patients found to have an extradural fluid collection, 1 was diagnosed by CT myelography alone and 7 were diagnosed by MR myelography alone. In a meta-analysis of 15 studies that included 643 patients with spontaneous intracranial hypotension, noninvasive MR myelography was also found to have a similar diagnostic sensitivity as MR myelography with intrathecal gadolinium (86 versus 83 percent) [106]. In a 2021 meta-analysis of studies assessing findings in spinal imaging performed for spontaneous intracranial hypotension, the proportional pooled estimates of finding an extradural CSF collection with noninvasive MR myelography was 63 percent (effect size 95% CI 0.24 to 1.03), similar to MR myelography with intrathecal gadolinium (60 percent) and radioisotope cisternography (67 percent) [41].
In some cases, noninvasive MR myelography may also identify the site of a CSF leak to guide site-specific treatment for patients who require targeted treatment options. (See "Spontaneous intracranial hypotension: Treatment and prognosis", section on 'Treatment at the site of leak'.)
Radioisotope cisternography — We perform radioisotope cisternography when noninvasive MR myelography is nondiagnostic. It is a nuclear study used to assess the flow and map the extent of CSF as it circulates through the neuraxis. It is used at centers with experience in its performance and interpretation to confirm a CSF leak [107]. The procedure involves intrathecal injection, via lumbar puncture, of a radioisotope (indium-111 DTPA) [108].
Since an LP is required as part of the procedure (see 'The role of lumbar puncture' below), opening CSF pressure is measured, and CSF is sent for analysis at the same time.
The dynamic flow of the isotope is followed by scanning at predetermined intervals for 24 or 48 hours. Normal CSF flow involves cephalad migration from the site of injection to the cerebral convexities and the sylvian fissures [11]. The most common cisternographic abnormality in CSF leaks is the absence or paucity of activity over the cerebral convexities (image 9), which provides reliable, though indirect, evidence of the presence of a leak [109-111]. Other findings suggestive of a CSF leak, though not as reliable, include early accumulation of radioisotope within the bladder and kidneys, leakage of isotope outside of the normal confines of the subarachnoid space, and early soft tissue uptake of radioisotope. By contrast, the presence of radioactivity over the cerebral convexities at 24 hours argues against an active CSF leak [108].
In a small retrospective study of patients with spontaneous CSF leaks, the diagnosis of intracranial hypotension was supported in all 10 patients who had radionucleotide cisternography, which showed early bladder accumulation of the nucleotide and reduced activity over the cerebral hemispheres, consistent with rapid uptake of the tracer in the bloodstream [112]. In addition, the location of the leaks was identified in 7 of the 10 patients with this method. In other studies, direct evidence of the exact site of the CSF leak from paradural extravasation of radioisotope was infrequent [107,113].
Iatrogenic CSF leak from the lumbar puncture is a potential complication of radioisotope cisternography [114].
Imaging studies to identify the site of a leak — When clinical suspicion for spontaneous intracranial hypotension remains high despite normal initial neuroimaging studies, further testing with studies typically performed to identify the specific site of a CSF leak may be performed after other entities in the differential diagnosis have been excluded. (See 'Differential diagnosis' below.)
In rare instances, localizing studies such as CT or MR myelography with intrathecal contrast or digital subtraction myelography (DSM) may be utilized to confirm the diagnosis by identifying small or slow leaks and CSF leaks along the ventral surface of the spinal cord [115]. The utility of these studies to identify or exclude the diagnosis of spontaneous intracranial hypotension is uncertain. (See "Spontaneous intracranial hypotension: Treatment and prognosis", section on 'Imaging evaluation to identify site of leak'.)
The role of lumbar puncture — An LP can document low CSF pressure in suspected cases of spontaneous intracranial hypotension. However, CSF pressure may be normal even in the presence of an active leak. In addition, LP may cause a CSF leak and post-dural puncture headache, worsening symptoms and potentially obscuring the diagnosis of spontaneous intracranial hypotension. We generally reserve diagnostic LP for circumstances when neuroimaging is nondiagnostic or as a part of imaging studies that require dural puncture, such as radioisotope cisternography. (See 'Radioisotope cisternography' above.)
●Opening pressure – Normal opening pressure in patients in the lateral decubitus position is typically 60 to 200 millimeters of water (mmH2O) in adults and children; opening pressures up to 250 mmH2O may be normal in people with obesity. (See "Cerebrospinal fluid: Physiology and utility of an examination in disease states", section on 'CSF pressure'.)
Low opening pressure in patients with spontaneous intracranial hypotension usually ranges from 0 to 60 mmH2O [10]. However, normal or even high opening pressure may occur in some cases of proven spontaneous intracranial hypotension if the measurement is made after a period of recumbency, if the CSF leak is intermittent, or if the CSF leak is chronic [18,20,41,116]. Even within the same patient, the CSF pressure may vary from LP to LP. In a review of 738 patients including 21 studies, the opening pressure was low in 67 percent but normal in 32 percent of patients [41].
In rare instances, the CSF pressure is negative (below that of atmospheric pressure), and a sucking noise may be heard when the stylet is removed from the LP needle.
●CSF analysis – The CSF is typically clear and colorless. Common CSF abnormalities in patients with spontaneous intracranial hypotension include a moderate lymphocytic pleocytosis (up to 50 cells/mm3), the presence of red blood cells, and elevated protein (commonly up to 100 mg/dL) [15]. The CSF pleocytosis likely reflects a reactive phenomenon secondary to hydrostatic pressure changes [44]. The elevated protein may be related to lowered CSF pressure leading to disruption of normal hydrostatic and oncotic pressure across the venous sinus and arachnoid villi, resulting in the passage of serum protein into the CSF [44].
CSF cytology and microbiology is always normal and CSF glucose is never low [101].
In patients with spontaneous intracranial hypotension, LPs are often difficult. Repeated attempts may be needed to obtain CSF, and traumatic blood-tinged fluid may result. In addition, so-called "dry taps" may be encountered, requiring cisternal taps to collect the fluid.
DIFFERENTIAL DIAGNOSIS — The clinical features of spontaneous intracranial hypotension may mimic several headache syndromes and other neurologic conditions. Some patients may have symptoms due to multiple sources such as migraine as well as spontaneous intracranial hypotension. Atypical presentations, including those without postural headaches, may be reported in patients with spontaneous intracranial hypotension whose symptoms are chronic [117].
●Migraine – Migraine is a common condition that may coexist with other conditions including spontaneous intracranial hypotension. Patients with migraine may report worsening symptoms in the upright posture or toward the second half of the day as well as associated symptoms such as nausea, vomiting, or dizziness. However, migraine headaches may be distinguished by the presence of aura, longer duration of headache, and episodic nature of symptoms. In addition, rapid improvement of symptoms with recumbency is uncommon with migraine headaches. (See "Pathophysiology, clinical manifestations, and diagnosis of migraine in adults", section on 'Clinical features'.)
●Cervicogenic headache – Patients with cervicogenic headaches may report onset or worsening symptoms with upright positioning due to cervical muscle strain [18]. Other clinical features of spontaneous intracranial hypotension and imaging abnormalities are not typically found in patients with cervicogenic headache. (See "Cervicogenic headache".)
●Chiari I malformation – Some patients with low-lying cerebellar tonsils consistent with a Chiari I malformation may present with occipital headaches or dizziness. However, the headaches in patients with a symptomatic Chiari I malformation are typically associated with physical activity or Valsalva maneuvers rather than upright positioning, and brain magnetic resonance imaging does not show evidence of low cerebrospinal fluid (CSF) pressure, unlike those with spontaneous intracranial hypotension [18]. (See "Chiari malformations", section on 'Chiari I clinical features'.)
●Postural tachycardia syndrome – Orthostatic headache in the absence of CSF leak may also be a manifestation of the postural tachycardia syndrome (POTS) or orthostatic intolerance [118]. The presence of tachycardia with upright positioning identifies patients with POTS. (See "Postural tachycardia syndrome".)
●Post-dural puncture headache – Patients with symptoms of post-dural puncture headache following a lumbar puncture or inadvertent dural puncture for epidural anesthesia are typically identified by the onset of symptoms immediately following the procedure.
However, patients with spontaneous intracranial hypotension may develop worsening symptoms due to dural puncture performed as part of the diagnostic evaluation. (See 'The role of lumbar puncture' above.)
The clinical features and management of post-dural puncture is discussed in detail separately. (See "Post dural puncture headache".)
●CSF shunts – Patients who have CSF shunts placed for various neurosurgical indications may develop a syndrome identical to that of spontaneous intracranial hypotension. Evaluation of the shunt function is warranted to assess for overdrainage (over shunting) of CSF [15]. (See "Normal pressure hydrocephalus", section on 'Ventricular shunting' and "Hydrocephalus in children: Management and prognosis", section on 'CSF shunt'.)
SUMMARY AND RECOMMENDATIONS
●Pathophysiology – Spontaneous intracranial hypotension occurs when imbalance in the production, absorption, or flow of cerebrospinal fluid (CSF) leads to low intracranial pressure and sagging of the brain within the skull. The resultant traction on connected nerves and other structures can cause a clinical syndrome often described by postural headaches. (See 'Pathophysiology' above.)
Spontaneous intracranial hypotension arises from CSF leakage located in the spine due to three main sources: spontaneous dural tear, rupture of meningeal diverticula, and CSF-venous fistula (figure 1).
●Epidemiology – The estimated annual incidence of spontaneous intracranial hypotension is 4 to 5 per 100,000. The mean age of patients is 43 years with a range from 2 to 88 years of age, and the proportion of female individuals is 63 percent. (See 'Epidemiology' above.)
●Clinical features
•Orthostatic headache – Postural headache is usually the major manifestation of spontaneous intracranial hypotension. The headache ordinarily develops within two hours, and in most cases within 15 minutes, of sitting or standing. Relief is typically obtained with recumbency, usually within minutes. (See 'Headache' above.)
Some patients do not have a postural component to the headache at onset; in others, the orthostatic pattern may evolve into a chronic daily headache pattern.
•Associated symptoms – Other symptoms associated with spontaneous intracranial hypotension include nausea, vomiting, neck pain, tinnitus, dizziness, and changes in hearing. (See 'Associated symptoms' above.)
●Diagnosis – The diagnosis of spontaneous intracranial hypotension is made in patients with headache, typically orthostatic in quality, with or without associated symptoms, and with evidence on imaging of CSF leak or low CSF pressure (algorithm 1). (See 'Diagnosis' above and 'Our approach' above.)
•Brain and spine MRI – We perform magnetic resonance imaging with gadolinium contrast of the brain and spine as the initial studies for confirming the diagnosis of spontaneous intracranial hypotension. (See 'Initial diagnostic neuroimaging' above.)
-Brain MRI is the most sensitive test for identifying spontaneous intracranial hypotension and may show diffuse pachymeningeal enhancement (image 4) or other findings suggestive of low CSF pressure (image 3 and image 7 and image 5 and image 6).
-Spinal MRI may show extradural fluid collections, collapse of the dural space, or other evidence suggestive of a CSF leak (image 1 and image 8 and image 2).
•Additional imaging studies – We perform additional diagnostic imaging such as MR myelography and radioisotope cisternography when initial brain and spine MRI are abnormal but nondiagnostic and when clinical suspicion for the diagnosis is high despite normal initial imaging. (See 'Additional neuroimaging when initial studies are nondiagnostic' above.)
•The role of lumbar puncture – Lumbar puncture (LP) may cause a CSF leak and post-dural puncture headache, worsening symptoms and potentially obscuring the diagnosis of spontaneous intracranial hypotension. We generally reserve diagnostic LP for circumstances when neuroimaging is nondiagnostic or as a part of imaging studies that require dural puncture, such as radioisotope cisternography. (See 'The role of lumbar puncture' above.)
●Differential diagnosis – Spontaneous intracranial hypotension may mimic several headache syndromes and other neurologic conditions such as migraine, cervicogenic headache, symptomatic Chiari I malformation, and postural tachycardia and other orthostatic intolerance syndromes. (See 'Differential diagnosis' above.)
Patients with post-dural puncture headaches and CSF shunt overdrainage presenting with the same clinical syndrome as patients with spontaneous intracranial hypotension are typically distinguished by different clinical circumstances.
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