Spontaneous Intracranial Hypotension Syndrome Research Articles

Evaluation and management of orthostatic headache in hypermobility disorders.

Headache is a frequent symptom among patients with hypermobility spectrum disorders. This mini review focuses specifically on a challenging aspect of headache evaluation in all patients, but especially those with hypermobility - the orthostatic headache. While the differential for an orthostatic headache is overall limited, patients with hypermobility disorders have risk factors for all of the most commonly encountered orthostatic headache disorders. The most common conditions to produce orthostatic headaches are discussed - spontaneous intracranial hypotension, cervicogenic headache, and postural orthostatic tachycardia syndrome. Less common etiologies of orthostatic headache pertinent to any patient are presented in table format.

Surgical management of spontaneous intracranial hypotension syndrome: a literature review.

Spontaneous intracranial hypotension (SIH) is a highly disabling but often misdiagnosed disorder. The optimal management options for patients with SIH remain uncertain. The aim of this study was to review studies reporting the management of SIH with a special emphasis on the surgical treatment of SIH including clinical trials, case series and case reports related to the issue of various neurosurgical procedures performed for SIH treatment. The clinical outcomes of patients diagnosed with SIH treated with either only surgery or with surgery as the primary method of treatment were analysed. The PubMed, Scopus and Google Scholar databases were searched according to the established criteria. The literature search revealed seven clinical trials, five case series and eight case reports regarding surgical treatment of patients diagnosed with SIH. Manuscripts reporting at least five individuals treated surgically for SIH were considered as case series. In most published articles, surgery provided clinical benefit, resulting in a success rate of 82.6-100% for complete relief of SIH symptoms. Our literature review has revealed that SIH can be diagnosed reliably by MRI and cisternography. The identification of the location of SIH is mandatory for its successful surgical treatment. The clinical outcome is related to the location of SIH in the spinal canal. Most often, cerebrospinal fluid leakage occurs in the thoracic region. Surgical treatment is very effective and the obtained treatment results are complete and permanent. of the location of SIH is mandatory for its successful surgical treatment. The clinical outcome is related to the location of SIH in the spinal canal. Most often, cerebrospinal fluid leakage occurs in the thoracic region. Surgical treatment is very effective and the obtained treatment results are complete and permanent.

Spontaneous intracranial hypotension syndrome presented with sixth cranial nerve palsy: a case report

Introduction Spontaneous intracranial hypotension (SIH) is a secondary cause of headache often misdiagnosed and underdiagnosed disorder. The main presentation is orthostatic headache. An uncommon symptom is cranial nerve palsy. We described a case of SIH that presented to our service with sixth cranial nerve palsy. Case Report Female, 39 years old, no relevant medical past or history of trauma, awoke due intense holocranial headache, associated with vomiting and photophobia, worsening in orthostasis. In the general emergency department, she was release with prescription of analgesics and topiramate, without resolution. After a week, the patient reported diplopia and was referred to our service, a tertiary center. In admission, she kept an intense orthostatic headache and in neurologic examination she presented right sixth nerve palsy, no other deficits. Laboratorial tests were normal, including metabolic and infectious marks. Cerebrospinal fluid (CSF) opening pressure was low (50 mmH2O) and analysis showed elevated protein levels (158mg/dl). MRI showed diffuse pachymeningeal enhancement and venous sinus distension, mainly in superior sagittal venous sinus. CT myelogram detected a spinal CSF leak in transition C1-C2. Initially, performed hydration and bed rest, while patient with partial improvement of headache. An epidural blood patch was then performed using 15ml of autologous blood with compatible contrast and lidocaine. There was complete resolution of pain after the procedure and four weeks later complete resolution of right sixth nerve palsy. Discussion According to International Classification of Headaches Disorders, third edition (ICHD-3), the headache attributed to SIH is descripted as a headache has developed in temporal relation to low CSF pressure (<60mm H2O) and/or evidence of CSF leakage on imaging. (To see the complete abstract, please, check out the PDF).

Surgical treatment of spinal CSF-venous fistulas: a systematic review

CSF-venous fistula is a relatively new and unexplored cause of spontaneous intracranial hypotension syndrome (SIH). The syndrome was first described in 1974 in a patient with chronic lumbar puncture-associated headache after digital subtraction myelography. After 40 years, CSF-venous fistula was considered as the cause of the SIH syndrome in patients with orthostatic headache. CSF-venous fistula is a pathological connection of the subarachnoid space and the adjacent epidural vein or veins. It is one of the top three causes of SIH along with dural defects and meningeal diverticulum. Despite the insufficient assessment of the prevalence of CSF-venous fistulas, some authors consider the syndrome to be the cause of 25 % of the cases. Positional headaches, as well as headaches associated with cough and Valsalva maneuver, are the most common symptoms in patients with CSF-venous fistulas. These patients are characterized by typical MRI signs of intracranial hypotension, such as a clear visualization of pachymeninx, venous congestion, an increase in the size of the pituitary gland, brain sagging syndrome, tonsillar herniation, etc. However, due to the rarity of this disease, algorithms for its diagnosis and treatment have not been established. Management of patients is usually limited to conservative treatment as the first-line method. This includes EBP alone or in combination with fibrin glue. Open surgery for ligation or coagulation of the fistula is used in cases of failed conservative treatment. Endovascular occlusion of the draining vein is a relatively new and less common treatment. The article presents a systematic review of the literature and analysis of the clinical results of various types of treatment for CSF-venous fistulas (EBP, surgical excision and endovascular embolization).

Clinical Presentation, Investigation Findings, and Treatment Outcomes of Spontaneous Intracranial Hypotension Syndrome

Spontaneous intracranial hypotension (SIH) is a highly disabling but often misdiagnosed disorder. The best management options for patients with SIH are still uncertain. To provide an objective summary of the available evidence on the clinical presentation, investigations findings, and treatment outcomes for SIH. Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline-compliant systematic review and meta-analysis of the literature on SIH. Three databases were searched from inception to April 30, 2020: PubMed/MEDLINE, Embase, and Cochrane. The following search terms were used in each database: spontaneous intracranial hypotension, low CSF syndrome, low CSF pressure syndrome, low CSF volume syndrome, intracranial hypotension, low CSF pressure, low CSF volume, CSF hypovolemia, CSF hypovolaemia, spontaneous spinal CSF leak, spinal CSF leak, and CSF leak syndrome. Original studies in English language reporting 10 or more patients with SIH were selected by consensus. Data on clinical presentation, investigations findings, and treatment outcomes were collected and summarized by multiple observers. Random-effect meta-analyses were used to calculate pooled estimates of means and proportions. The predetermined main outcomes were the pooled estimate proportions of symptoms of SIH, imaging findings (brain and spinal imaging), and treatment outcomes (conservative, epidural blood patches, and surgical). Of 6878 articles, 144 met the selection criteria and reported on average 53 patients with SIH each (range, 10-568 patients). The most common symptoms were orthostatic headache (92% [95% CI, 87%-96%]), nausea (54% [95% CI, 46%-62%]), and neck pain/stiffness (43% [95% CI, 32%-53%]). Brain magnetic resonance imaging was the most sensitive investigation, with diffuse pachymeningeal enhancement identified in 73% (95% CI, 67%-80%) of patients. Brain magnetic resonance imaging findings were normal in 19% (95% CI, 13%-24%) of patients. Spinal neuroimaging identified extradural cerebrospinal fluid in 48% to 76% of patients. Digital subtraction myelography and magnetic resonance myelography with intrathecal gadolinium had high sensitivity in identifying the exact leak site. Lumbar puncture opening pressures were low, normal (60-200 mm H2O), and high in 67% (95% CI, 54%-80%), 32% (95% CI, 20%-44%), and 3% (95% CI, 1%-6%), respectively. Conservative treatment was effective in 28% (95% CI, 18%-37%) of patients and a single epidural blood patch was successful in 64% (95% CI, 56%-72%). Large epidural blood patches (>20 mL) had better success rates than small epidural blood patches (77% [95% CI, 63%-91%] and 66% [95% CI, 55%-77%], respectively). Spontaneous intracranial hypotension should not be excluded on the basis of a nonorthostatic headache, normal neuroimaging findings, or normal lumbar puncture opening pressure. Despite the heterogeneous nature of the studies available in the literature and the lack of controlled interventional studies, this systematic review offers a comprehensive and objective summary of the evidence on SIH that could be useful in guiding clinical practice and future research.

Epidural blood patch in the management of the syndrome of spontaneous intracranial hypotension: An effective therapeutic approach

Background: Spontaneous intracranial hypotension (SIH) is a rare syndrome characterized by heterogeneity of presentation and prognosis, which can occasionally result in serious complications, such as the formation of subdural hematoma (SDH). This case series aims to emphasize that SIH remains a diagnostic and therapeutic challenge; it can present with a far broad clinical spectrum of symptoms, can lead to SDH and if conservative treatment fails, an epidural blood patch (EBP) is a viable treatment option. Although the exact aetiology of SIH is not known, it is believed to be due to cerebrospinal fluid (CBF) leak or a low CBF pressure. Case report: Three patients (two males and one female) with age ranging between 38-53 years old who presented with complaints not only of an orthostatic headache, but with a variety of symptoms of SIH, including the formation of two SDHs in one of them, were included in this series. These patients did not respond to conservative management and subsequently, given the clinical and radiological evidence of SIH, were referred to the Anaesthesia Department for an EBP. The exact site of the CSF leak was identified with imaging modalities, including magnetic resonance imaging (MRI) of the brain and spinal cord, prior to the EBP. All three patients were subjected to an EBP with an 18-gauge epidural needle placed into the middle epidural compartment at the T12–L3 level. A total of between 30–43 mL of autologous blood was collected from the patients’ left basilic vein and was injected into the epidural space under strict aseptic conditions. Two lumbar (L1–L2, L2–L3) and one thoracic (T11–T12) EBPs were performed on the three patients. All patients reported complete resolution of symptoms following the EBPs, while MRI imaging improved substantially. Discussion: This report describes three cases of SIH with CSF leak originating from the cervical, the thoracic and the lumbar level. The EBP restored CSF volume and relieved the patients' persistent symptoms. MRI helps in showing indirect signs of low volume of CSF, though it may not be possible to find the actual site of leak. In conclusion, EBP is a well-accepted and beneficial treatment modality for SIH when conventional measures fail.

自发性低颅压继发硬膜下积液1例报告

自发性低颅压继发硬膜下积液1例报告

075 A case of spontaneous CSF rhinorrhea in a patient with marfan syndrome

IntroductionSpontaneous cerebrospinal fluid leak is uncommon condition and frequently associated with hereditary disorders of connective tissues. Nasal CSF leakage is extremely rare.1Methods and resultsWe present the case of a 40-year-old woman presented to hospital for few days history of postural headache associated with clear intermittent discharge from right nostril without any signs of meningism. There was no history of trauma. She has a background history of Marfan syndrome with associated complications of ASD repair at age 2, mechanical Aortic and Mitral valve replacement, aortic root repair, previous ST elevation MI with LV dysfunction, automated implantable cardioverter-defibrillator in situ, atrial fibrillation, and Hashimoto’s thyroiditis. Her regular medications are warfarin, bisoprolol and thyroxine. The clear nasal discharge was positive for β-2 transferrin confirming cerebrospinal fluid. Her CT Brain did not reveal any clear site of CSF leak. She had a flexible nasendoscopy which showed normal nasal passageway, no defect in nasal mucosa and no active CSF leakage. She was managed conservatively with strict bed rest and advised to minimise strenuous activity and heavy lifting.ConclusionSpontaneous cerebrospinal fluid leak is uncommon condition and frequently associated with hereditary disorders of connective tissues. Nasal CSF leakage is extremely rare.1 Testing β-2 transferrin has high sensitivity and specificity.2Initial treatment may include bed rest, oral or intravenous hydration, oral caffeine or corticosteroids.3 4 If conservative therapy fails, surgical repair with nasal endoscopic approach is recommended.2 5ReferencesOmmaya A, Di Chiro G, Baldwin M, Pennybacker J. Non-traumatic cerebrospinal fluid rhinorrhoea. Journal of Neurology, Neurosurgery & Psychiatry 1968;31(3):214-–225.Wang E, Vandergrift W, Schlosser R. Spontaneous CSF Leaks. Otolaryngologic Clinics of North America 2011;44(4):845–856.Milledge J, Ades L, Cooper M, Jaumees A, Onikul E. Severe spontaneous intracranial hypotension and Marfan syndrome in an adolescent. Journal of Paediatrics and Child Health 2005;41(1–2):68–71.Placantonakis D, Bassani L, Graffeo C, Behrooz N, Tyagi V, Wilson T, et al. Noninvasive diagnosis and management of spontaneous intracranial hypotension in patients with marfan syndrome: Case Report and Review of the Literature. Surgical Neurology International 2014;5(1):8.Spontaneous cerebrospinal fluid rhinorrhea. Medicine 2018;97(7):e9954.

A clinical analysis on 40 cases of spontaneous intracranial hypotension syndrome

Objective: To investigate clinical and imaging features of 40 patients with spontaneous intracranial hypotension (SIH).Methods: 40 cases of spontaneous intracranial hypotension (SIH) diagnosed in our hospital from June 2013 to September 2017 were collected and retrospectively analyzed.Results: In our study, the male to female ratio was 2:3. The average age of onset was 43.0 ± 15.0 years. There were 12 (30.0%) patients with clear incentives, mostly catching cold. The average length of hospital stay was 11.2 ± 6.3 days. All the patients showed orthostatic headaches, 62.5% patients with nausea or vomiting, 40.0% patients with neck stiffness, 17.5% patients with dizziness and vertigo, 10.0% patients with numbness and weakness of limbs, 5% patients with neck discomfort, and 2.5% patients with visual symptoms (visual impairment, photophobia, diplopia). 24 patients underwent CT scans which showed no abnormalities in 20 cases (83.3%), subdural fluid accumulation in 3 cases (12.5%), and subdural haematoma in 1 case (2.5%). Cranial contrast-enhanced MR scans showed diffuse pachymeningeal enhancement (95.83%, 23/24), signs of pituitary hyperaemia in 5 cases (20.8%), subdural fluid accumulation and subdural hematoma in 4 cases (16.7%), sagging of the brain in 3 cases (12.5%), and engorgement of venous structures in 1 case (4.1%). Six patients underwent plain and contrast-enhanced spinal MR scans which showed varying degrees of dural thickening and enhanced performance in all the patients. 92.5% (37/40) of patients had cerebrospinal fluid pressure <60 mmH2O on lumbar puncture. 97.5% of patients underwent conservative treatment with drugs and had a good outcome.Conclusion: Orthostatic headache and cranial MRI diffuse pachymeningeal enhancement are characteristic features of SIH. Cranial contrast-enhanced MR scan is recognized as the first and non-invasive investigation in the diagnosis of SIH. Most patients had cerebrospinal fluid pressure <60 mmH2O. The vast majority of patients improved with fluid replacement.

Acquired Chiari I Malformation Secondary to Spontaneous Intracranial Hypotension Syndrome and Persistent Hypoglycemia: A Case Report

Spontaneous intracranial hypotension (SIH) is a rare and potentially serious condition in childhood. Cerebrospinal fluid (CSF) volume depletion is thought to be the main causative feature for intracranial hypotension and results from a spontaneous CSF leak, often at the spine level. SIH is increasingly diagnosed in clinical practice, although it manifests a varied symptomatology. The downward displacement of the brain, sometimes mimicking a Chiari I malformation, has rarely been reported. We present a case of a SIH with Chiari I malformation accompanied by an unusual clinical presentation of persistent hypoglycemia.

Distribution Patterns of Spinal Epidural Fluid in Patients with Spontaneous Intracranial Hypotension Syndrome.

The aim of this study is to clarify the details of distribution patterns of spinal epidural fluid and to establish it as measure of spontaneous intracranial hypotension (SIH) syndrome diagnosis. Magnetic resonance imaging findings of the spine were analyzed in 37 patients, 24 women and 13 men (mean age 46.3 years), with SIH. Detection rate, thickness and patterns of the fluid collection were evaluated at every vertebral level. Follow-up spinal MRI findings were also analyzed for changes in epidural fluid collection and association with clinical symptoms. The MR images of the cervical spine were obtained in 30 patients, the thoracic spine in 36, and the lumbar spine in 17 patients. Epidural fluid collection was detected totally in 36 patients (97%) and was predominantly found at the mid-thoracic vertebrae. The fluid tended to locate dorsal to the dural sac at the thoracic spine and ventral at the cervical and lumbar spine. Patients with shorter duration of illness tended to have thicker fluid in the thoracic spine. In follow-up MRI, the findings of epidural fluid collection has disappeared in 32/36 cases within 3 months after treatment. Although residual fluid collection was found at the thoracic level in 4 cases, clinical symptoms were improved in all patients. This study suggested that the mid-thoracic spine should be chosen as the target of MRI in screening of SIH, and enlarged dorsal epidural space is strongly indicative of SIH.

Clinical symptoms and results of autonomic function testing overlap in spontaneous intracranial hypotension and postural tachycardia syndrome

Background and purpose: Orthostatic headache is a hallmark of patients with spontaneous intracranial hypotension (SIH) but may also occur in patients with postural tachycardia syndrome (POTS). Our aim was to compare the clinical symptoms and findings of autonomic function testing in patients with SIH and POTS. Methods: This was a retrospective analysis of the clinical symptoms and findings of autonomic function testing, including sympathetic vasoconstrictor and parasympathetic cardiac function as well as head-up tilt in patients with SIH and POTS. Results: Nine patients with confirmed SIH and 48 with POTS (neuropathic N = 35, hyperadrenergic N = 5, deconditioned N = 8) were included. SIH patients experienced on average a shorter disease duration than patients with POTS. Orthostatic headache was present in all patients with SIH and 27% of patients with POTS. There was a broad overlap of other clinical symptoms of orthostatic intolerance. Screening autonomic function testing revealed normal sympathetic and parasympathetic function in all patients. All patients with SIH showed an excessive clinically symptomatic heart rate increase during standing, fulfilling the diagnostic criteria for POTS. Conclusion: Clinical symptoms and results of autonomic function testing overlap in SIH and POTS. Hence, patients with prominent orthostatic headache fulfilling the diagnostic criteria for POTS should also be evaluated for further testing of a spinal cerebrospinal fluid leak, in the absence of a history of lumbar puncture.

Ehlers Danlos, POTS, and Occult Cerebrospinal Fluid Leak: A Case Report

Ehlers Danlos syndromes (EDS) are associated with spontaneous intracranial hypotension (SIH) and postural orthostatic tachycardia syndrome (POTS). We hypothesized that some POTS patients might in fact have occult SIH due to unappreciated EDS. We describe a 26-year-old female with a history of POTS and headache who presented to us with negative imaging for cerebrospinal fluid leak (CSF). Upon examination with clinical evidence of EDS and supportive history, we performed an epidural blood patch despite repeat imaging evidence negative for CSF leak resulting in resolution of the patient’s POTS, headache, and cognitive symptoms. Patients with POTS and connective tissue disorders associated with dural weakness may be suffering from occult chronic CSF leaks. MRI imaging may be falsely reassuring and dissuade clinicians from performing epidural blood patching among patients who can be cured.

Dural Thickening of the Internal Auditory Canal in Patients With Spontaneous Intracranial Hypotension Syndrome.

This study aimed to assess the utility of dural thickening of the internal auditory canal (IAC) in patients with spontaneous intracranial hypotension (SIH) syndrome and determined the sensitivity and specificity of this image finding. Magnetic resonance images were evaluated for 22 cases of definite SIH and 16 cases of unlikely SIH. On contrast-enhanced magnetic resonance imaging, pachymeningeal enhancement and dural thickening of the IAC were assessed. Pachymeningeal enhancement was observed in 21 of 22 patients in the definite SIH group and 1 of 16 patients in the unlikely SIH group (sensitivity, 95.5%; specificity, 93.8%). Dural thickening of the IAC was observed in 15 of 22 patients in the definite SIH group and 0 of 16 patients in the unlikely SIH group (sensitivity, 68.2%; specificity, 100%). Dural thickening of the IAC showed 100% specificity for SIH syndrome and can increase the accuracy of diagnosis of SIH syndrome.

O030. Treatment of orthostatic headache from spontaneous intracranial hypotension syndrome: single institutional experience of 326 cases.

Materials and methods From 1992 to 2015 we observed 326 patients (169 females and 157 males; age range 15-84; mean, 47 years) with OH from SIH according to the ICHD 2004 criteria. One hundred and sixteen performed a conservative treatment, while 210 underwent lumbar EBP with 15-50 ml (mean 28 ml) autologous blood. In 203 cases blood was mixed with contrast medium (1 ml of gadolinium [12 pts] and 5 ml of iopamidol [191 pts]), because about 30’ after EBP they underwent a spinal MRI or CT to document the blood spread into the epidural space. All patients were kept in a 30° Trendelenburg position for an hour before the procedure, during and for 24 h (52 pts) or 16 h (158 pts) after the procedure. Fifty-two patients were premedicated with acetazolamide (500 mg). The follow-up ranged from 6 months to 8 years.

Diagnostic value of MRI for spontaneous intracranial hypotension syndrome

Objective To analyze the magnetic resonance imaging （ MRI ） appearances of spontaneous intracranial hypotension syndrome （ SIHS） ,in order to improve the understanding of this disease .Methods The clini-cal data of 7 patients with SIHS confirmed by lumbar puncture were retrospectively analyzed .MRI was performed in all cases,in which there were 6 cases with contrast-enhanced MRI.Results All of them showed diffusely thickening of dural.6 cases with brain contrast-enhanced MRI demonstrated linear ,non-nodular and diffusely dural enhancement . The dilation of sinus and great vein were observed in 5 cases,subdural hydroma in 2 cases,brain sagging in 3 cases, pituitary gland plumpness in 2 cases,subdural hematoma in 1 case and 1 case with linear spinal dural enhancement . Conclusion The MRI manifestations of SIHS are characteristic ,and it will be helpful for the diagnosis by combining clinical data. Key words: Intracranial hypotension; Syndrome; Magnetic resonance imaging; Diagnosis

Modified Valsalva test differentiates primary from secondary cough headache

I suppose that the patient number 14, reported in the article of RJ Lane et al. on “Modified Valsalva test differentiates primary from secondary cough headache ”in a recent issue of your esteemed journal, was probably suffering from spontaneous intracranial hypotension syndrome (SIH) caused by cervical manipulation.

Two cases of medically-refractory spontaneous orthostatic headaches with normal cerebrospinal fluid pressures responding to epidural blood patching: Intracranial hypotension versus hypovolemia and the need for clinical awareness

The diagnosis of spontaneous intracranial hypotension or cerebrospinal fluid (CSF) hypovolemia syndrome requires a high index of suspicion and meticulous history taking, demonstration of low CSF pressure and/or neuroimaging features. A 31-year-old male, presented with subacute onset moderate occipital and sub-occipital headaches precipitated by upright posture and relieved on recumbency and neck pain for 2 years. There was no trauma, cranial/spinal surgery. Clinical examination was normal and CSF opening pressure and laboratory study were normal. Magnetic resonance imaging (MRI) brain showed thin subdural hygroma. Another patient, 41-year-old male presented with 1 month of subacute onset severe bifrontal throbbing orthostatic headaches (OHs). CSF opening pressure was normal. Contrast MRI brain showed the presence of bilateral subdural hygromas, diffuse meningeal enhancement, venous distension, sagging of the brain, and tonsillar herniation. We report two cases of “spontaneous OHs” with normal CSF pressures who were successfully treated with epidural blood patching after poor response to conservative management.

Spontaneous intracranial hypotension syndrome treated with a double epidural blood patch

Spontaneous intracranial hypotension (SIH) is considered to be a very rare disease. It is characterised by an orthostatic headache in the absence of a past history of a trauma or a dural puncture. SIH is caused by a spontaneous spinal cerebrospinal fluid (CSF) leakage demonstrated by neuroradiological studies in most of the patients. Conservative treatment usually includes bed rest, hydration and administration of caffeine or steroids. However, when the patient is refractory to the conservative treatment, an epidural blood patch (EBP) is performed. We report a 34-year-old woman with SIH and no neuroradiologically demonstrable clear point of CSF leakage, who was treated with a double EBP at two different levels (lumbar and thoracic) in the same procedure. The patient was successfully managed, and she was still asymptomatic at the 18 months follow-up. After review of literature, we observed that execution of a double EBP at the same time is not a common procedure for treatment of SIH. We consider that simultaneous use of two EBP could be useful as a novel treatment in those cases of SIH without demonstration of CSF leakage.

Diagnostic value of the optic nerve sheath subarachnoid space in patients with intracranial hypotension syndrome

The size of the subarachnoid space in the optic nerve sheath (ONS) on MR images is thought to reflect intracranial pressure. The diagnostic value of this space was investigated in patients with spontaneous intracranial hypotension (SIH) syndrome. Coronal fat-saturated T2-weighted MRI of the orbit was performed in 15 patients with SIH fulfilling the diagnostic criteria for headache caused by low CSF pressure of the International Classification of Headache Disorders or the criteria for spontaneous spinal CSF leaks and intracranial hypotension. The size of the subarachnoid space in the ONS was measured in 2 slices behind the eyeballs. The images were compared before and after treatment. The CSF pressure was measured by lumbar puncture. Before treatment, the diameter of the ONS subarachnoid space ranged from 2.58 to 4.21 mm (mean 3.34 mm) and the thickness from 0 to 0.48 mm (mean 0.15 mm). Both measurements showed significant correlations with CSF opening pressure, and 8 patients had no CSF space before treatment. The size of CSF space increased in many patients after effective treatment. Disappearance of the CSF space in the ONS was frequently observed in patients with SIH. This characteristic finding may be useful in the diagnosis of SIH as well as in the evaluation of treatment effectiveness.