Incidence of cerebellar tonsillar ectopia in idiopathic intracranial hypertension: a mimic of the Chiari I malformation

Are Chiari Malformation and Basilar Invagination Associated with Jugular Foramen Stenosis?

OBJECTIVE

We compared the diameter of the jugular foramen (JF) between normal individuals and those with a diagnosis of craniovertebral junction abnormalities, such as Chiari malformation type I (CMI) and/or basilar invagination (BI).

METHODS

This cross-sectional analytical study measured the diameter of the right and left JF on magnetic resonance imaging scans of patients divided into 4 groups: 68 with combined CMI and BI (CMI+BI), 42 with isolated BI, 45 with isolated CMI, and 102 control cases. The t test determined sex differences, and univariate analysis of variance with Tukey's post hoc test assessed JF differences between groups.

RESULTS

Considering all combinations of laterality and sex, the CMI+BI group had a JF narrower than their respective control groups. The JF was bilaterally narrower in the BI group than in the control group only in the women. Regardless of laterality, the CMI group had a wider JF than did the CMI+BI group in men and did not differ from that of the control group. In the female patients with CMI, the right JF did not differ from that of the controls and was wider than that in the CMI+BI group. Also, the left JF was narrower than that in the control group and did not differ from that in the CMI+BI group.

CONCLUSIONS

JF narrowing is associated with CMI and BI when combined in the same patient. When CMI or BI are detected separately, they do not imply evident changes in JF morphometry. It is expected that these findings could bring empiric substrate to support theories that claim a possible role of intracranial pressure disturbances as a triggering factor for CMI.

Magnetic Resonance Imaging Signs of Idiopathic Intracranial Hypertension

Importance

The magnetic resonance imaging (MRI) criteria currently used to diagnose idiopathic intracranial hypertension (IIH) are based on expert opinion and have limited accuracy. Additional neuroimaging signs have been proposed and used with contradictory results; thus, prospective evidence is needed to improve diagnostic accuracy.

Objective

To provide evidence-based, accurate MRI signs for IIH diagnosis.

Design, Setting, and Participants

This prospective cohort study was conducted from January 2018 to May 2021 with 3 validation cohorts at 2 Danish headache centers and with 3 independent international cohorts. Consecutive patients with suspected IIH were enrolled. Eligibility required the clinical suspicion of IIH, age 18 years or older, and written informed consent. The validation cohorts comprised patients with confirmed IIH from Austria and the US, and patients without IIH from the US. Data analysis was performed from December 2021 to August 2023.

Exposure

Standardized diagnostic workup was performed to classify cases according to current criteria, and blinded evaluation of cerebral radiological diagnostics and papilledema was performed.

Main Outcomes and Measures

The primary outcomes were MRI signs associated with IIH as assessed by univariate analyses. An MRI score estimating papilledema was calculated using machine learning. Internal validation of associations with lumbar puncture opening pressure and outcome and external validation of accuracy were performed in 3 cohorts.

Results

Of 192 eligible patients (185 women [96.4%]; median [IQR] age, 28.0 [23.0-35.0] years), 110 were classified as having IIH, 4 as having probable IIH, and 1 as having suspected IIH without papilledema; 77 did not have IIH and served as controls, with corresponding age, sex, and weight. Papilledema at diagnosis was associated with perioptic subarachnoid space distension (56 patients [68.3%] vs 21 patients [41.2%]), posterior globe flattening (53 patients [66.3%] vs 10 patients [21.3%]), optic nerve disc protrusion (35 patients [30.4%] vs 2 patients [2.3%]), and transverse sinus venous stenosis (75 patients [79.8%] vs 29 patients [46.8%]). The papilledema-estimating MRI score showed optimal balance between sensitivity (49%) and specificity (87%) when 2 of the 3 latter signs were present and was associated with the lumbar puncture opening pressure and ophthalmological outcome. The score showed strong diagnostic accuracy in the external validation cohorts (587 patients; area under the receiver operating characteristic curve, 0.86) and outperformed the current (2013) diagnostic MRI criteria.

Conclusions and Relevance

The findings of this cohort study of patients with IIH and controls suggest that an evidence-based MRI score including posterior globe flattening, optic nerve disc protrusion, and transverse sinus stenosis can estimate the presence of papilledema more accurately than the current diagnostic criteria.

Is foramen magnum decompression for acquired Chiari I malformation like putting a finger in the dyke? - A simplistic overview of artificial intelligence in assessing critical upstream and downstream etiologies

Background

Missed diagnosis of evolving or coexisting idiopathic (IIH) and spontaneous intracranial hypotension (SIH) is often the reason for persistent or worsening symptoms after foramen magnum decompression for Chiari malformation (CM) I. We explore the role of artificial intelligence (AI)/convolutional neural networks (CNN) in Chiari I malformation in a combinatorial role for the first time in literature, exploring both upstream and downstream magnetic resonance findings as initial screening profilers in CM-1. We have also put together a review of all existing subtypes of CM and discuss the role of upright (gravity-aided) magnetic resonance imaging (MRI) in evaluating equivocal tonsillar descent on a lying-down MRI. We have formulated a workflow algorithm MaChiP 1.0 (Manjila Chiari Protocol 1.0) using upstream and downstream profilers, that cause de novo or worsening Chiari I malformation, which we plan to implement using AI.

Materials and Methods

The PRISMA guidelines were used for "CM and machine learning and CNN" on PubMed database articles, and four articles specific to the topic were encountered. The radiologic criteria for IIH and SIH were applied from neurosurgical literature, and they were applied between primary and secondary (acquired) Chiari I malformations. An upstream etiology such as IIH or SIH and an isolated downstream etiology in the spine were characterized using the existing body of literature. We propose the utility of using four selected criteria for IIH and SIH each, over MRI T2 images of the brain and spine, predominantly sagittal sequences in upstream etiology in the brain and multiplanar MRI in spinal lesions.

Results

Using MaChiP 1.0 (patent/ copyright pending) concepts, we have proposed the upstream and downstream profilers implicated in progressive Chiari I malformation. The upstream profilers included findings of brain sagging, slope of the third ventricular floor, pontomesencephalic angle, mamillopontine distance, lateral ventricular angle, internal cerebral vein-vein of Galen angle, and displacement of iter, clivus length, tonsillar descent, etc., suggestive of SIH. The IIH features noted in upstream pathologies were posterior flattening of globe of the eye, partial empty sella, optic nerve sheath distortion, and optic nerve tortuosity in MRI. The downstream etiologies involved spinal cerebrospinal fluid (CSF) leak from dural tear, meningeal diverticula, CSF-venous fistulae, etc.

Conclusion

AI would help offer predictive analysis along the spectrum of upstream and downstream etiologies, ensuring safety and efficacy in treating secondary (acquired) Chiari I malformation, especially with coexisting IIH and SIH. The MaChiP 1.0 algorithm can help document worsening of a previously diagnosed CM-1 and find the exact etiology of a secondary CM-I. However, the role of posterior fossa morphometry and cine-flow MRI data for intracranial CSF flow dynamics, along with advanced spinal CSF studies using dynamic myelo-CT scanning in the formation of secondary CM-I is still being evaluated.

The clinical findings to notice mild elevation of intracranial pressure in an otology clinic

Mildly elevated intracranial pressure appears to be a distinct pathology separate from idiopathic increased intracranial pressure and migraine. Many patients present with head fullness-pressure and dizziness, which is often suggestive of a clinical diagnosis of vestibular migraine. These patients may additionally have episodic vertigo as seen in endolymphatic hydrops and positional vertigo in addition to feeling dizzy. In most cases, hearing is normal. A long duration of the condition or a presence of associated ear pathologies, i.e., dehiscence, fistula, hypermobile footplate, or history of chronic ear infections can add hearing loss to clinical presentations. Low-pitch pulsatile tinnitus, when present, is an important symptom. The neuroimaging findings such as partially empty sella, blockage of the dural venous sinus or sigmoid sinus wall defects are frequently observed. The condition is diagnosed by measuring the lumbar puncture opening pressure. Typically, patients have normal cerebrospinal fluid chemistry and microscopy. Lowering the pressure during the lumbar puncture will resolve the patient's symptoms temporarily. Medical therapy is typically successful using carbonic anhydrase inhibitors and corrections of medical disorders that may be contributing to the increased pressure. A few require shunting or stenting procedures. In this review article, we define the condition in detail with illustrative cases that we collected from our practices.

Effect of Body Mass Index on Chiari Malformation 1 Tonsil Ectopia Length in Adults

OBJECTIVE

Diagnosis of Chiari I malformation (CM-1) is based on measurements of the inferior extension of the cerebellar tonsils into the foramen magnum on cranial or cervical spine magnetic resonance imaging. Imaging may be obtained before the patient is referred to the neurosurgical specialist. The length of time raises questions about the possibility that body mass index (BMI) fluctuations could affect the measurement of ectopia length. However, previous literature on BMI and CM-1 has reported conflicting findings on BMI.

METHODS

We conducted a retrospective chart review of 161 patients who were referred to a single neurosurgeon for CM-1 consultation. Patients with multiple recorded BMI values (n = 71) were compared to see if BMI changes correlated with changes in ectopia length. In addition, we compared and tested 154 recorded ectopia lengths from the patients (1 per patient) and patient BMI values with Pearson correlation and Welch t tests to determine if BMI changes either influenced or were associated with ectopia changes.

RESULTS

For the 71 patients with multiple BMI values, change in ectopia length ranged from -4.6-9.8 mm but was not statistically significant (r = 0.019; P = 0.88). For the 154 measured ectopia lengths, changes in BMI did not correlate with ectopia length (P > 0.05). Likewise, differences in ectopia length between patients in normal, overweight, and obese categories were not statistically significant (|tstat| < |tcrit|, P > 0.05).

CONCLUSIONS

In individual patients, we found that BMI and changes in BMI were not accompanied by changes in tonsil ectopia length.

Cranial Versus Cervical Spine Magnetic Resonance Imaging in Adult Chiari Malformation Type I Diagnostics: Is There a Difference in Tonsil Ectopia Length?

BACKGROUND

Chiari malformation type 1 (CM-1) diagnosis is based on measurement of the cerebellar tonsils on cranial or cervical spine magnetic resonance imaging (MRI). However, imaging parameters of cranial and cervical spine MRI could differ because spine MRI has greater resolution.

METHODS

We conducted a retrospective chart review of 161 patients of a single neurosurgeon for adult CM-I consultation between February 2006 and March 2019. Patients were selected based on receiving both cranial and cervical spine MRI within a month of each other to determine tonsillar ectopia length for CM-1. Ectopias were measured to determine if differences in values were statistically significant.

RESULTS

From the 161 total patients, 81 had cranial and cervical spine MRI for a total of 162 tonsil ectopia measurements (81 cranial and 81 spinal). Average ectopia length on a cranial MRI was 9.1 mm (±5.2 mm); average ectopia length on a spinal MRI was 8.9 mm (±5.3 mm). Average cranial and spinal MRI values were found to be <1 standard deviation apart. Two-tailed, nonequal variances t test determined that differences between the cranial and spinal ectopia measurements were insignificant (P = 0.2403).

CONCLUSIONS

This study confirmed that the added resolution offered by spine MRI did not make better or more refined measurements over cranial MRI that could lead to measurement differences, which can instead be attributed to chance. Cranial and cervical spine MRI can be used to determine the degree of the tonsil ectopia.

Low versus High Intracranial Compliance in Adult Patients with Chiari Malformation Type 1-Comparison of Long-Term Outcome After Tailored Treatment

BACKGROUND

In patients with Chiari malformation type 1 (CMI) presenting with low intracranial compliance (ICC), foramen magnum decompression (FMD) often fails and the complication rate may be higher. We therefore routinely perform a preoperative assessment of ICC from intracranial pressure measurement. Patients with low ICC are treated with ventriculoperitoneal shunt (VPS) before FMD. In this study, we assess the outcome of patients with low ICC, compared with patients with high ICC treated with FMD alone.

METHODS

We reviewed the clinical and radiologic data of all consecutive patients with CMI treated between April 2008 and June 2021. ICC was assessed by overnight measurement of the pulsatile intracranial pressure: mean wave amplitude (MWA) above a previously defined threshold for abnormality was considered a surrogate marker for low ICC. The outcome was scored by Chicago Chiari Outcome Scale.

RESULTS

Of 73 patients, 23 with low ICC (average MWA 6.8 ± 1.2 mm Hg) received VPS before FMD, whereas 50 with high ICC (average MWA 4.4 ± 1.0 mm Hg) received only FMD. After a mean follow-up of 78.7 ± 41.4 months, 96% of all patients subjectively improved. The mean Chicago Chiari Outcome Scale score was 13.1 ± 2.2. Enlargement of cerebrospinal fluid space in the foramen magnum was achieved in 95% and regression of syringomyelia in 74% of cases. We found no significant difference in outcome between the patients with low and high ICC.

CONCLUSIONS

By identifying patients with CMI associated with low ICC and tailoring their treatment by VPS before FMD, we achieved favorable clinical and radiologic outcomes comparable to those with high ICC.

Cerebellar Tonsillar Descent Mimicking Chiari Malformation

Chiari I malformation has been defined as cerebellar tonsillar descent greater than 5 mm below the foramen magnum. Suboccipital decompression remains the mainstay of treatment for symptomatic patients. Other conditions sometimes have imaging features that mimic Chiari I malformation. These patients are at risk of misdiagnosis and mismanagement, including surgery that may be unnecessary or may even worsen the underlying condition. The aim of this study was to analyse a series of Chiari I malformation mimics and identify differentiating imaging features. The mimics are categorised as post-traumatic cranio-cervical junction arachnoiditis, dural band, spontaneous intracranial hypotension, idiopathic intracranial hypertension, and cysts. Better understanding of these conditions will assist with diagnosis and optimal management, including avoiding unnecessary surgery.

Incidental findings on brain magnetic resonance imaging (MRI) in adults: a review of imaging spectrum, clinical significance, and management

Utilization of brain MRI has dramatically increased in recent decades due to rapid advancement in imaging technology and improving accessibility. As a result, radiologists increasingly encounter findings incidentally discovered on brain MRIs which are performed for unrelated indications. Some of these findings are clinically significant, necessitating further investigation or treatment and resulting in increased costs to healthcare systems as well as increased patient anxiety. Moreover, management of these incidental findings poses a significant challenge for referring physicians. Therefore, it is important for interpreting radiologists to know the prevalence, clinical consequences, and appropriate management of these findings. There is a wide spectrum of incidental findings on brain MRI such as asymptomatic brain infarct, age-related white matter changes, microhemorrhages, intracranial tumors, intracranial cystic lesions, and anatomic variants. This article provides a narrative review of important incidental findings encountered on brain MRI in adults with a focus on prevalence, clinical implications, and recommendations on management of these findings based on current available data.

Exploring the prognostic differences in patients of Chiari malformation type I with syringomyelia undergoing different surgical methods

Background

The best surgical treatment of Chiari malformation patients with syringomyelia remains controversial, and whether cerebellar tonsillectomy should be performed has not been decided.

Objective

To evaluate the efficacy of posterior fossa decompression with duraplasty (PFDD) and Posterior fossa decompression with resection of tonsils (PFDRT) in patients of Chiari malformation type I (CM-I) with syringomyelia and explore relevant factors affecting prognosis.

Patients and methods

We retrospectively analyzed 182 adult patients of CM-I with syringomyelia who underwent PFDD or PFDRT over a 6-year period, and analyzed their clinical manifestations, imaging features, and follow-up data. Clinical outcomes were assessed using the Chicago Chiari Outcome Scale (CCOS), and imaging outcomes were assessed using the syrinx remission rate. Difference comparisons were performed to compare the differences between different surgical groups. Influencing factors associated with outcome were investigated using bivariate analysis and multiple linear regression analysis.

Results

There were statistically significant differences in CCOS score (p = 0.034) and syrinx remission rates (p = 0.046) between the PFDRT group and the PFDD group after surgery. Regression analysis showed that preoperative motor dysfunction, cerebellar-related symptoms and different surgical methods may have influenced the CCOS score and that brainstem-related symptoms and age may have influenced the syrinx remission rates in the total patient group (p < 0.05). Regression analysis showed that the duration of symptoms, cerebellar-related symptoms and preoperative syrinx diameter may have influenced the CCOS score and that the preoperative cerebellar tonsillar hernia distance may have influenced the postoperative syrinx remission rate in the PFDRT group (p < 0.05). Age and length of hospital stay may have influenced the CCOS score, and brainstem-related symptoms and age may have influenced the syrinx remission rates in the PFDD group (p < 0.05).

Conclusion

This study showed that the CCOS score in the PFDRT group was better than that in the PFDD group. Preoperative motor dysfunction, cerebellar-related symptoms, and different surgical methods in patients of CM-I with syringomyelia affected postoperative CCOS score. Both the duration of symptoms and the age of the patients should be actively considered as factors influencing prognosis. Symptomatic CM-I patients with syringomyelia should undergo surgical treatment as early as possible.

Chiari Malformation Type 1 in Adults

The term Chiari malformation refers to a heterogeneous group of anatomical abnormalities at the craniovertebral junction. Chiari malformation type 1 (CM1) refers to the abnormal protrusion of cerebellar tonsils through the foramen magnum and is by far the commonest type. Its prevalence is estimated approximately 1%; it is more common in women and is associated with syringomyelia in 25-70% of cases. The prevalent pathophysiological theory proposes a morphological mismatch between a small posterior cranial fossa and a normally developed hindbrain that results in ectopia of the tonsils.In most people, CM1 is asymptomatic and diagnosed incidentally. In symptomatic cases, headache is the cardinal symptom. The typical headache is induced by Valsalva-like maneuvers. Many of the other symptoms are nonspecific, and in the absence of syringomyelia, the natural history is benign. Syringomyelia manifests with spinal cord dysfunction of varying severity. The approach to patients with CM1 should be multidisciplinary, and the first step in the management is phenotyping the symptoms, because they may be due to other pathologies, like a primary headache syndrome. Magnetic resonance imaging, which shows cerebellar tonsillar decent 5 mm or more below the foramen magnum, is the gold standard investigative modality. The diagnostic workup may include dynamic imaging of the craniocervical junction and intracranial pressure monitoring.The management of CM1 is variable and sometimes controversial. Surgery is usually reserved for patients with disabling headaches or neurological deficits from the syrinx. Surgical decompression of the craniocervical junction is the most widely used procedure. Several surgical techniques have been proposed, but there is no consensus on the best treatment strategy, mainly due to lack of high-quality evidence. The management of the condition during pregnancy, restriction to lifestyle related to athletic activities, and the coexistence of hypermobility require special considerations.

Features of Idiopathic Intracranial Hypertension on MRI With MR Elastography: Prospective Comparison With Control Individuals and Assessment of Postintervention Changes

BACKGROUND. Understanding of dynamic changes of MRI findings in response to intracranial pressure (ICP) changes in idiopathic intracranial hypertension (IIH) is limited. Brain stiffness, as assessed by MR elastography (MRE), may reflect changes in ICP. OBJECTIVE. The purpose of this study was to compare pituitary height, ventricular size, and brain stiffness between patients with IIH and control individuals and to evaluate for changes in these findings in patients with IIH after interventions to reduce ICP. METHODS. This prospective study included 30 patients (28 women, two men; median age, 29.9 years) with IIH and papilledema and 21 control individuals (21 women, 0 men; median age, 29.1 years), recruited from January 2017 to July 2019. All participants underwent 3-T brain MRI with MRE; patients with IIH underwent additional MRI examinations with MRE after acute intervention (lumbar puncture with normal closing pressure; n = 11) and/or chronic intervention (medical management or venous sinus stenting with resolution or substantial reduction in papilledema; n = 12). Pituitary height was measured on sagittal MP-RAGE images. Ventricular volumes were estimated using unified segmentation, and postintervention changes were assessed by tensor-based morphometry. Stiffness pattern score and regional stiffness values were estimated from MRE. RESULTS. In patients with IIH, median pituitary height was smaller than in control individuals (3.1 vs 4.9 mm, p < .001) and was increased after chronic (4.0 mm, p = .05), but not acute (2.3 mm, p = .50), intervention. Ventricular volume was not different between patients with IIH and control individuals (p = .33) and did not change after acute (p = .83) or chronic (p = .97) intervention. In patients with IIH, median stiffness pattern score was greater than in control individuals (0.25 vs 0.15, p < .001) and decreased after chronic (0.23, p = .11) but not acute (0.25, p = .49) intervention. Median occipital lobe stiffness was 3.08 kPa in patients with IIH versus 2.94 kPa in control individuals (p = .07) and did not change after acute (3.24 kPa, p = .73) or chronic (3.10 kPa, p = .83) intervention. CONCLUSION. IIH is associated with a small pituitary and increased brain stiffness pattern score; both findings may respond to chronic interventions to lower ICP. CLINICAL IMPACT. The "partially empty sella" sign and brain stiffness pattern score may serve as dynamic markers of ICP in IIH.

Insights on the Hydrodynamics of Chiari Malformation

Background: We propose that the appearance of a ptosis of the cerebellar tonsils and syringomyelia is linked to its own hemohydrodynamic mechanisms. We aimed to quantify cerebrospinal fluid (CSF) and cerebral blood flow to highlight how neurofluid is affected by Chiari malformations type 1(CMI) and its surgery. Methods: We retrospectively included 21 adult patients with CMI who underwent pre- and postoperative phase contrast MRI (PCMRI) during the period from 2001 to 2017. We analyzed intraventricular CSF, subarachnoid spaces CSF, blood, and tonsils pulsatilities. Results: In preoperative period, jugular venous drainage seems to be less preponderant in patients with syringomyelia than other patients (venous correction factor: 1.49 ± 0.4 vs. 1.19 ± 0.1, p = 0.05). After surgery, tonsils pulsatility decreased significantly (323 ± 175 μL/cardiac cycle (CC) vs. 194 ± 130 μL/CC, p = 0.008) and subarachnoid CSF pulsatility at the foramen magnum increased significantly (201 ± 124 μL/CC vs. 363 ± 231 μL/CC, p = 0.02). After surgery, we found a decrease in venous flow amplitude (5578 ± 2469 mm3/s vs. 4576 ± 2084 mm3/s, p = 0.008) and venous correction factor (1.98 ± 0.3 vs. 1.20 ± 0.3 mm3/s, p = 0.004). Conclusions: Phase-contrast MRI could be a useful additional tool for postoperative evaluation and follow-up, and is complementary to morphological imaging.

MRI findings differentiating tonsillar herniation caused by idiopathic intracranial hypertension from Chiari I malformation

PURPOSE

Some patients with idiopathic intracranial hypertension (IIH) have cerebellar tonsillar herniation ≥ 5 mm mimicking Chiari malformation I (CMI), which can result in misdiagnosis and unjustified treatment. Our purpose was to identify IIH patients with tonsillar herniation ≥ 5 mm (IIH_TH) and compare with CMI patients to assess imaging findings that could distinguish the two conditions.

METHODS

Ninety-eight patients with IIH, 81 patients with CMI, and 99 controls were retrospectively assessed. Two neuroradiologists blindly reviewed MR images. IIH_TH patients were compared with CMI patients and controls regarding the extent of tonsillar herniation (ETH), bilateral transverse sinus stenosis (BTSS), hypophysis-sella ratio (HSR), and bilateral tortuosity of optic nerve (BTON).

RESULTS

13/98 (13.2%) IIH patients had tonsillar herniation ≥ 5 mm (IIH_TH) and were significantly younger and had higher BMI compared with CMI patients and controls. ETH was significantly less in the IIH_TH than CMI (6.5 ± 2.4 mm vs. 10.9 ± 4.4 mm; p < 0.001). BTSS and HSR < 0.5 were more common in IIH_TH than CMI (p < 0.001 and p = 0.003, respectively). No differences were seen between CMI and controls. BTON was significantly more common in IIH_TH compared to control (p = 0.01) but not to the CMI (p = 0.36). Sensitivity and specificity to differentiate IIH_TH from CMI were 69.2% and 96.1% for BTSS and 69.2% and 75.3% for HSR < 0.5.

CONCLUSION

The presence of BTSS and/or HSR < 0.5 in patients with ETH ≥ 5 mm should suggest further evaluation to exclude IIH before considering CMI surgery.

Utility of Neuroimaging in the Management of Chronic and Acute Headache

Imaging plays an important role in identifying the cause of the much less common secondary headaches. Such headaches may be caused by a variety of pathologic conditions which can be categorized as intracranial and extracranial. Idiopathic intracranial hypertension imaging findings include "empty sella," orbital changes, and dural venous sinus narrowing. Intracranial hypotension (ICH) is frequently caused by CSF leaks. Imaging findings include loss of the CSF spaces, downward displacement of the brain, as well as dural thickening and enhancement. Severe cases of ICH may result in subdural hematomas. A variety of intracranial and skull base tumors may cause headaches due to dural involvement. Extracranial tumors and lesions that frequently present with headaches include a variety of sinonasal tumors as well as mucoceles. Neurovascular compression disorders causing headaches include trigeminal and glossopharyngeal neuralgia. Imaging findings include displacement and atrophy of the cranial nerve caused by an adjacent arterial or venous structure.

Population-Based Evaluation of Indirect Signs of Increased Intracranial Pressure

BACKGROUND

The Mayo Clinic Study of Aging (MCSA) is a unique prospective study that systematically evaluates the normal aging population and includes many participants undergoing both MRI and lumbar puncture (LP). Using MCSA date, we aimed to determine the prevalence of indirect signs of raised intracranial pressure (ICP) on MRI and whether these correlate with LP opening pressure (OP). This is a large-scale study that evaluates how often indirect signs of increased ICP occur in a normal population.

METHODS

MCSA participants who had an MRI within 3 months of an LP with recorded OP were included in the study. MRIs were reviewed for indirect signs of raised ICP, including pituitary to sella (P/S) ratio, cerebellar tonsillar ectopia, and optic nerve sheath diameter (ONSD). These signs were evaluated for correlations with OP and influences from body mass index (BMI) and obstructive sleep apnea (OSA).

RESULTS

Five hundred ninety-seven MCSA patients were identified who underwent both LP and MRI. Two hundred sixty (43.6%) were women. The median age was 70.7 years (range 32.6-92.7). Median OP was 152 mm H2O (range 60-314 mm H2O), with 91 (15.2%) participants having an OP ≥ 200 mm H2O. Empty or partially empty sella was seen in 81 (12.8%) of the cohort. The P/S ratio decreased with increasing OP (r = -0.3, P < 0.001). There was a weak correlation between OP and average ONSD (r = 0.184, P = 0.01), which was no longer significant when accounting for age, gender, and BMI (partial r2 = 0.014, P = 0.097). There was no correlation between OP and cerebellar tonsillar ectopia. OSA was associated with increased ONSD (P = 0.004), but this did not remain statistically significant after accounting for age, gender, and BMI (P = 0.085).

CONCLUSION

Smaller pituitary gland size correlated with increasing OP. This suggests that ICP is a continuum with some normal individuals demonstrating asymptomatic radiologic signs of raised ICP.

Diagnostic performance of neuroimaging in suspected idiopathic intracranial hypertension

The diagnostic utility of neuroradiologic signs associated with idiopathic intracranial hypertension (IIH) for the evaluation of patients presenting with papilloedema remains yet to be elucidated. This multicentre retrospective cohort study assessed consecutive patients presenting with suspected papilloedema to Auckland District Health Board (NZ) and Stanford University Medical Centre (US), between 2005 and 2019, undergoing magnetic resonance imaging and venography (MRI/MRV) or computed tomography and venography (CT/CTV) prior to lumbar puncture assessment for diagnostic suspicion of IIH. Data were collected regarding demographic, clinical, radiologic, and lumbar puncture parameters, and the diagnosis of IIH was determined according to the Friedman criteria for primary pseudotumor cerebri syndrome. A total of 204 participants (174 females; mean ± SD age 29.9 ± 12.2 years) were included, and 156 (76.5%) participants fulfilled the diagnostic criteria for IIH. The presence of any IIH-associated radiologic sign on MRI/MRV demonstrated a sensitivity (95% CI) of 74.8% (65.8%-82.0%) and specificity (95% CI) of 94.7% (82.7%-98.5%), while radiologic signs on CT/CTV exhibited a sensitivity (95% CI) of 61.0% (49.9%-71.2%) and specificity (95% CI) of 100.0% (83.2%-100.0%). In summary, the modest sensitivities of radiologic signs of IIH would support the routine use of lumbar puncture assessment following neuroimaging to secure the diagnosis. However, the high specificities might lend limited support for the judicious deferment of lumbar puncture assessment among typical IIH demographic patients who consent to the inherent small risk of missed pathology, which has been proposed by some clinicians.

Papilledema: A Review of the Pathophysiology, Imaging Findings, and Mimics

Increased intracranial pressure is the most common cause of papilledema. Multiple etiologies such as cerebral edema, hydrocephalus, space occupying lesions, infection, and idiopathic intracranial hypertension among others should be considered. Imaging plays a critical role in the detection of pathologies that can cause papilledema. MRI with contrast and CE-MRV, in particular, are key for the diagnosis of idiopathic intracranial hypertension. This review will focus in common and infrequent causes of papilledema, the role of imaging in patients with papilledema as well as its potential mimickers.

Idiopathic intracranial hypertension: an illustrated guide for the trainee radiologist

Idiopathic intracranial hypertension is characterized by increased intracranial pressure, headache, and visual perturbations. Although the pathophysiology of idiopathic intracranial hypertension is obscure, several mechanisms have been proposed, such as increased cerebral blood volume, excessive cerebrospinal fluid volume (due to high production or impaired resorption), and inflammatory mechanisms as a likely cause of or contributor to impaired cerebrospinal fluid circulation. It predominantly affects women of reproductive age who are overweight or obese. The most common symptoms are daily headache, synchronous pulsatile tinnitus, transient visual perturbations, and papilledema with visual loss. The main neuroimaging findings are a partially empty sella turcica; flattening of the posterior sclera; transverse sinus stenosis (bilateral or in the dominant sinus); a prominent perioptic subarachnoid space, with or without optic nerve tortuosity; and intraocular protrusion of the optic nerve head. The main complication of idiopathic intracranial hypertension is visual loss. Within this context, neuroimaging is a crucial diagnostic tool, because the pathology can be reversed if properly recognized and treated early.

Posterior fossa volume in idiopathic intracranial hypertension: a magnetic resonance imaging-based study

BACKGROUND

The etiology of idiopathic intracranial hypertension (IIH) is uncertain. Studies suggest the fundamental cause of the Chiari 1 malformation, a congenitally hypoplastic posterior fossa, may explain the genesis of IIH in some patients.

PURPOSE

To assess the hypothesis that linear and volumetric measurements of the posterior fossa (PF) can be used as predictors of IIH.

MATERIAL AND METHODS

A retrospective analysis of magnetic resonance imaging (MRI) studies on 27 patients with IIH and 14 matched controls was performed. A volumetric sagittal magnetization prepared rapid acquisition gradient echo sequence was used to derive 10 linear cephalometric measurements. Total intracranial and bony posterior fossa volumes (PFVs) were derived by manual segmentation. The ratio of PFV to total intracranial volume was calculated.

RESULTS

In total, 41 participants were included, all women. Participants with IIH had higher median body mass index (BMI). No significant differences in linear cephalometric measurements, total intracranial volumes, and PFVs between the groups were identified. Linear measurements were not predictive of volumetric measurements. However, on multivariate logistic regression analysis, the likelihood of IIH decreased significantly per unit increase in relative PFV (odds ratio [OR]=3.66 × 10^-50; 95% confidence interval [CI]=1.39 × 10^-108 to 1.22 × 10^-5; P = 0.04). Conversely, the likelihood of IIH increased per unit BMI increase (OR=1.19; 95% CI=1.04-1.47; P = 0.02).

CONCLUSION

MRI-based volumetric measurements imply that PF alterations may be partly responsible for the development of IIH and Chiari 1 malformations. Symptoms of IIH may arise due to an interplay between these and metabolic, hormonal, or other factors.

Evolution of MRI Findings in Patients with Idiopathic Intracranial Hypertension after Venous Sinus Stenting

BACKGROUND AND PURPOSE

The correlation between imaging findings and clinical status in patients with idiopathic intracranial hypertension is unclear. We aimed to examine the evolution of idiopathic intracranial hypertension-related MR imaging findings in patients treated with venous sinus stent placement.

MATERIALS AND METHODS

Thirteen patients with idiopathic intracranial hypertension (median age, 26.9 years) were assessed for changes in the CSF opening pressure, transstenotic pressure gradient, and symptoms after venous sinus stent placement. Optic nerve sheath diameter, posterior globe flattening and/or optic nerve protrusion, empty sella, the Meckel cave, tonsillar ectopia, the ventricles, the occipital emissary vein, and subcutaneous fat were evaluated on MR imaging before and 6 months after venous sinus stent placement. Data are expressed as percentages, medians, or correlation coefficients (r) with P values.

RESULTS

Although all patients showed significant reductions of the CSF opening pressure (31 versus 21 cm H₂O; P = .005) and transstenotic pressure gradient (22.5 versus 1.5 mm Hg; P = .002) and substantial improvement of clinical symptoms 6 months after venous sinus stent placement, a concomitant reduction was observed only for posterior globe involvement (61.5% versus 15.4%; P = .001), optic nerve sheath diameter (6.8  versus 6.1 mm; P < .001), and subcutaneous neck fat (8.9  versus 7.4 mm; P = .001). Strong correlations were observed between decreasing optic nerve sheath diameters and improving nausea/emesis (right optic nerve sheath diameter, r =  0.592, P = .033; left optic nerve sheath diameter, r = 0.718, P = .006), improvement of posterior globe involvement and decreasing papilledema (r = 0.775, P = .003), and decreasing occipital emissary vein diameter and decreasing headache frequency (r = 0.74, P = .035). Decreasing transstenotic pressure gradient at 6 months strongly correlated with decreasing empty sella (r = 0.625, P = .022) and regressing cerebellar ectopia (r = 0.662, P = .019).

CONCLUSIONS

Most imaging findings persist long after normalization of intracranial pressure and clinical improvement. However, MR imaging findings related to the optic nerve may reflect treatment success.

Differentiation of Chiari malformation type 1 and spontaneous intracranial hypotension using objective measurements of midbrain sagging

OBJECTIVE

Chiari malformation type 1 (CM-1) and spontaneous intracranial hypotension (SIH) are causes of headache in which cerebellar tonsillar ectopia (TE) may be present. An accurate method for differentiating these conditions on imaging is needed to avoid diagnostic confusion. Here, the authors sought to determine whether objective measurements of midbrain morphology could distinguish CM-1 from SIH on brain MRI.

METHODS

This is a retrospective case-control series comparing neuroimaging in consecutive adult subjects with CM-1 and SIH. Measurements obtained from brain MRI included previously reported measures of brain sagging: TE, slope of the third ventricular floor (3VF), pontomesencephalic angle (PMA), mamillopontine distance, lateral ventricular angle, internal cerebral vein-vein of Galen angle, and displacement of iter (DOI). Clivus length (CL), an indicator of posterior fossa size, was also measured. Measurements for the CM-1 group were compared to those for the entire SIH population (SIHall) as well as a subgroup of SIH patients with > 5 mm of TE (SIHTE subgroup).

RESULTS

Highly significant differences were observed between SIHall and CM-1 groups in the following measures: TE (mean ± standard deviation, 3.1 ± 5.7 vs 9.3 ± 3.5 mm), 3VF (-16.8° ± 11.2° vs -2.1° ± 4.6°), PMA (44.8° ± 13.1° vs 62.7° ± 9.8°), DOI (0.2 ± 4.1 vs 3.8 ± 1.6 mm), and CL (38.3 ± 4.5 vs 44.0 ± 3.3 mm; all p < 0.0001). Eight (16%) of 50 SIH subjects had TE > 5 mm; in this subgroup (SIHTE), a cutoff value of < -15° for 3VF and < 45° for PMA perfectly discriminated SIH from CM-1 (sensitivity and specificity = 1.0). DOI showed perfect specificity (1.0) in detecting SIH among both groups. No subjects with SIH had isolated TE without other concurrent findings of midbrain sagging.

CONCLUSIONS

Measures of midbrain sagging, including cutoff values for 3VF and PMA, discriminate CM-1 from SIH and may help to prevent misdiagnosis and unnecessary surgery.

Rapidly progressive medulloblastoma initially mimicking idiopathic intracranial hypertension and Chiari I malformation: A case report

Introduction

Medulloblastoma (MDB) often causes signs and symptoms of elevated intracranial pressure (ICP) with imaging findings of mass lesion. Here, we report a case of MDB who initially presented with clinical features imitating idiopathic intracranial hypertension (IIH) and Chiari I malformation (CIM).

Case presentation

A 19-year-old man had clinical symptoms of elevated ICP without mass lesion on imaging. He was initially diagnosed with IIH and CIM, which underwent shunt surgery and posterior fossa decompression. Later on, he had recurrent symptoms, and the new imaging revealed the development of MDB in the right cerebellar hemisphere. After tumor resection, the patient rapidly deteriorated with spinal metastases.

Discussion and conclusion

Management of the coexistence between IIH and CIM in patients with rising ICP is complicated. MDB is one of the aggressive malignant brain tumors showing a wide range of imaging features, including non-enhancing mass. Therefore, recognizing the possibility of brain tumors mimicking IIH or CIM is crucial.

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The coexistence of idiopathic intracranial hypertension (IIH) and Chiari I malformation (CIM) is complicated.

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Medulloblastoma (MDB) can present with a wide range of imaging features, including non-enhancing mass.

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Exclusion of the secondary cause of rising intracranial pressure is necessary before making the diagnosis of IIH or CIM

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Early diagnosis, including subtype of MDB, and urgent treatment are crucial for better outcome.

Space Flight-Associated Neuroocular Syndrome, Idiopathic Intracranial Hypertension, and Pseudotumor Cerebri: Phenotypic Descriptions, Pathogenesis, and Hydrodynamics

Recent data from astronauts who have returned to Earth from a long-duration space flight have unequivocally distinguished spaceflight-associated neuro-ocular syndrome (SANS) from idiopathic intracranial hypertension (IIH) and pseudotumor cerebri (PTC). We review the semiology and pathogenesis of these three entities, noting that optic disc edema is what unites them, and this where the similarities between SANS and IIH/PTC end. We distinguish between PTC and IIH and between SANS and IIH/PTC and review the medical and surgical therapy of IIH/PTC. The key to understanding the phenomenon of optic disc edema is the geometry of the optic nerve sheath, which is a simulacrum of an inverted Venturi tube. This allows us to theoretically study the hydrodynamics of the optic nerve sheath by applying simple physical laws, including the Venturi effect, Poiseuille's law, and Reynold's number, and we speculate on nature's design and the correlation of form and function in understanding how cerebrospinal fluid (CSF) circulates in the optic nerve sheath as it approaches the optic nerve head. Recent spectacular data on the histology of the blood nerve-barrier of the optic nerve disc and the glymphatic system of the optic nerve sheath will also help us understand the development of optic disc edema due to the microgravity-induced cephalad shift of CSF in SANS. We will explore the role of the sodium/potassium adenosine triphosphatase (ATPase) pump on choroid plexus epithelial cells and the aquaporin-4 water receptors located on astrocyte end-feet and their complex interactions with the tetracyclines, mineralocorticoids, and therapeutic agents with carbonic anhydrase activity. We also adumbrate the complex interactions between obesity, vitamin A, and 11-beta-hydroxysteroid dehydrogenase and how the aquaporin-4 receptor relates to these interactions.

Delayed Cranial Nerve Palsies and Chiari Type I Malformation After Epidural Anesthesia in the Setting of Childbirth

Epidural analgesia is an efficient method of controlling pain and has a wide spectrum of therapeutic and diagnostic applications. Potential complications may occur in a delayed fashion, can remain undiagnosed, and can be a source of significant morbidity. We present a 37-year-old woman presented with severe spontaneous occipital headaches, diplopia, and dizziness that occurred spontaneously six weeks after giving birth. Her primary method of pain control during labor was epidural analgesia. Her neurologic exam revealed a cranial nerve six palsy with ptosis, and her brain MRI demonstrated a Chiari I malformation which had not been previously diagnosed. CT myelography of the lumbar spine revealed extradural contrast extravasation within the interspinous soft tissue at L1-L2, which was the site of her prior epidural procedure. She underwent epidural blood patch administration, and her cranial nerve palsy resolved along with all of her other symptoms. The development of concurrent Chiari I malformation and cranial nerve palsy after epidural anesthesia is an exceptionally rare occurrence. Neurologic complications after epidural anesthesia are likely under-reported, since patients are often lost to follow-up or have subtle neurologic signs which can easily be missed. This frequently delayed presentation emphasizes the importance of patient education and the necessity of a detailed neurological exam when symptoms occur.

Graded Cerebellar Lobular Volume Deficits in Adolescents and Young Adults with Fetal Alcohol Spectrum Disorders (FASD)

The extensive prenatal developmental growth period of the cerebellum renders it vulnerable to unhealthy environmental agents, especially alcohol. Fetal alcohol spectrum disorders (FASD) is marked by neurodysmorphology including cerebral and cerebellar volume deficits, but the cerebellar lobular deficit profile has not been delineated. Legacy MRI data of 115 affected and 59 unaffected adolescents and young adults were analyzed for lobular gray matter volume and revealed graded deficits supporting a spectrum of severity. Graded deficits were salient in intracranial volume (ICV), where the fetal alcohol syndrome (FAS) group was smaller than the fetal alcohol effects (FAE) group, which was smaller than the controls. Adjusting for ICV, volume deficits were present in VIIB and VIIIA of the FAE group and were more widespread in FAS and included lobules I, II, IV, V, VI, Crus II, VIIB, and VIIIA. Graded deficits (FAS < FAE) were consistently present in lobules VI; neither group showed volume deficits in Crus I or IX. Neuroradiological readings blind to diagnosis identified 20 anomalies, 8 involving the cerebellum, 5 of which were in the FAS group. We speculate that the regional cerebellar FASD-related volume deficits may contribute to diagnostically characteristic functional impairment involving emotional control, visuomotor coordination, and postural stability.

Chiari I malformation and altered cerebrospinal fluid dynamics-the highs and the lows

PURPOSE

This paper reviews the altered cerebrospinal fluid dynamics that can be associated with paediatric Chiari I malformation and we present our own institutional experience.

METHODS

We conducted a thorough review of the literature and retrospectively analyzed all cases of operatively managed paediatric Chiari 1 malformation at our institution between February 2006 and February 2019.

RESULTS

Acquired Chiari malformation (ACM) can radiologically mimic Chiari I and has been associated with both intracranial hypotension (either secondary to lumboperitoneal shunting or spontaneous CSF hypotension) and idiopathic intracranial hypertension (IIH). At our institution, 61 paediatric cases (range, 2-15 years) underwent foramen magnum decompression (FMD) for Chiari I malformation. Whilst 80% (50/61) of cases underwent FMD with no preceding or post-operative problems of CSF dynamics, 8% (5/61) of cases had hydrocephalus at initial presentation requiring CSF diversion followed by FMD for persistent Chiari, and 10% (6/61) developed hydrocephalus following FMD and required long-term CSF diversion.

CONCLUSIONS

In paediatric ACM, the management of intracranial hypotension involves thorough radiological assessment and inclusion/adjustment of a valve in the case of lumboperitoneal shunting or epidural blood patch or interventional techniques in the case of spontaneous CSF leak. Thereby, unwarranted posterior fossa decompression surgery is avoided. In the case of IIH and Chiari I malformation, children who have recurrent symptoms despite adequate posterior fossa decompression surgery (failed Chiari), there is a strong role for intracranial pressure monitoring as raised intracranial pressure may indicate long-term CSF diversion.

Chiari 1 malformation and raised intracranial pressure

BACKGROUND

The pathophysiology of Chiari 1 malformation (CM1) is inextricably related to intracranial pressure (ICP). The characteristic cerebellar tonsil herniation at the foramen magnum may either cause raised ICP by disturbing CSF flow (as observed in idiopathic CM1) or may itself be the effect of raised ICP (as observed in acquired CM1). Distinguishing between these two phenomena, therefore, is of paramount importance in successfully alleviating the symptoms of the condition and preventing serious complications.

OBJECTIVES

In this article, we discuss the pathophysiology of raised ICP in CM1 and review the current evidence for its investigation and treatment. We also share our own clinical experience which investigates the utility of ICP monitoring in a series of 26 children with CM1.

Dynamic cerebellar herniation in Chiari patients during the cardiac cycle evaluated by dynamic magnetic resonance imaging

PURPOSE

Cerebellar herniation in Chiari patients can be dynamic, following the cerebrospinal fluid pulsatility during the cardiac cycle. We present a voxel intensity distribution method (VIDM) to automatically extract the pulsatility-dependent herniation in time-resolved MRI (CINE MRI) and compare it to the simple linear measurements. The degree of herniation is furthermore compared on CINE and static sequences, and the cerebellar movement is correlated to the presence of hydrocephalus and syringomyelia.

METHODS

The cerebellar movement in 27 Chiari patients is analyzed with VIDM and the results were compared to linear measurements on an image viewer (visual inspection, VI) using a paired t test. Second, an ANOVA test is applied to compare the degree of herniation on static 3D MRI and CINE. Finally, the Pearson's correlation coefficient is calculated for the correlation between cerebellar movement and the presence of hydrocephalus and syringomyelia.

RESULTS

VIDM showed significant movement in 85% of our patients. Assuming that movement < 1 mm cannot be detected reliably on an image viewer, VI identified movement in 29.6% of the patients (p = 0.002). The herniation was greater on static sequences than on CINE in most cases, but this was not statistically significant. The cerebellar movement was not correlated with hydrocephalus or syringomyelia (Pearson's coefficient < 0.3).

CONCLUSIONS

VIDM is a sensitive method to detect tissue movement on CINE MRI and could be used for Chiari patients, but also for the evaluation of cyst membranes, ventriculostomies, etc. The cerebellar movement appears not to correlate with hydrocephalus and syringomyelia in Chiari patients.

Chiari Type I Malformation Associated With Verbal Fluency Impairment

PURPOSE

Chiari malformation (CM) Type I is a rare disorder that implies an anomaly in the craniocervical junction, where one or both cerebellar tonsils are displaced below the foramen magnum into the cervical spinal channel. Research carried out regarding cognitive symptoms such as verbal fluency is scarce. The aim of this study was to investigate whether verbal fluency is impaired in a CM clinical group compared to a group of healthy control individuals while controlling for depression and anxiety symptomatology.

METHOD

For this purpose, 101 individuals were enrolled to take part in the study (51 CM, 50 healthy controls). The Controlled Oral Word Association Test (Benton, de Hamsher, & Sivan, 1983) and the Hospital Anxiety and Depression Scale (Zigmond & Snaith, 1983) were administered.

RESULTS

Results showed significantly lower scores for the CM group in verbal fluency compared to the control group (p < .005). After performing an analysis of covariance to eliminate depression and anxiety symptomatology tendencies, it was observed that verbal fluency could not be predicted by this variable (p > .005).

CONCLUSIONS

From the results of this study, it can be concluded that people suffering from CM exhibit less verbal fluency than healthy control individuals and that this difference is not caused by depression or anxiety.

The Significance and Reliability of Imaging Findings in Pseudotumor Cerebri

The objective of our study was to provide a comparative assessment of previously reported magnetic resonance imaging (MRI) parameters in primary and secondary pseudotumor cerebri (PTC) patients, to examine their diagnostic contribution, and to evaluate their association with symptoms, neuro-ophthalmological findings, laboratory results, and cerebrospinal fluid characteristics. Twenty-eight consecutive patients with PTC were included in the study. Age- and sex-matched 20 individuals with normal neurologic examination served as the control group. Modified Dandy Criteria were used for the diagnosis of PTC. Orbital and cranial MRI and MR venography of all patients and controls were assessed by three radiologists. According to our study, posterior flattening of the globe (64% sensitive, 100% specific), optic nerve sheath distention (46% sensitive, 100% specific), vertical tortuosity of the optic nerve (30% sensitive, 95% specific), and partial empty sella (43% sensitive, 100% specific) emerged as particularly valuable markers for a diagnosis of PTC.

Cerebrospinal fluid rhinorrhea and otorrhea: A multimodality imaging approach

Cerebrospinal fluid (CSF) leaks are extracranial egress of CSF into the adjacent paranasal sinus or tympanomastoid cavity due to an osteodural defect involving skull base. It can be due to a multitude of causes including accidental or iatrogenic trauma, congenital malformations and spontaneous leaks. Accurate localization of the site of the leak, underlying causes and appropriate therapy is necessary to avoid associated complications. In this paper relevant anatomy, clinical diagnosis, imaging modalities and associated findings are discussed along with a brief mention about management.

Cranial morcellation decompression for refractory idiopathic intracranial hypertension in children

BACKGROUND

Primary idiopathic intracranial hypertension (PIIH) in children is rare and has a poorly understood pathophysiology. It is characterized by raised intracranial pressure (ICP) in the absence of an identified brain lesion. Diagnosis is usually confirmed by the measurement of a high cerebrospinal fluid (CSF) opening pressure and exclusion of secondary causes of intracranial hypertension. Refractory PIIH may lead to severe visual impairment. The purpose of this study was to evaluate a cranial morcellation decompression (CMD) technique as a new surgical alternative to stabilize intracranial pressure in PIIH.

MATERIALS AND METHODS

A literature review was carried out, disclosing only 7 pediatric cases of PIIH treated with surgical skull expansion. In addition, we describe here one case of our own experience treated by CMD.

CONCLUSIONS

CMD surgery is a safe and effective option to control refractory PIIH in selected patients.

Noninvasive Assessment of Intracranial Pressure Status in Idiopathic Intracranial Hypertension Using Displacement Encoding with Stimulated Echoes (DENSE) MRI: A Prospective Patient Study with Contemporaneous CSF Pressure Correlation

BACKGROUND AND PURPOSE

Intracranial pressure is estimated invasively by using lumbar puncture with CSF opening pressure measurement. This study evaluated displacement encoding with stimulated echoes (DENSE), an MR imaging technique highly sensitive to brain motion, as a noninvasive means of assessing intracranial pressure status.

MATERIALS AND METHODS

Nine patients with suspected elevated intracranial pressure and 9 healthy control subjects were included in this prospective study. Controls underwent DENSE MR imaging through the midsagittal brain. Patients underwent DENSE MR imaging followed immediately by lumbar puncture with opening pressure measurement, CSF removal, closing pressure measurement, and immediate repeat DENSE MR imaging. Phase-reconstructed images were processed producing displacement maps, and pontine displacement was calculated. Patient data were analyzed to determine the effects of measured pressure on pontine displacement. Patient and control data were analyzed to assess the effects of clinical status (pre-lumbar puncture, post-lumbar puncture, or control) on pontine displacement.

RESULTS

Patients demonstrated imaging findings suggesting chronically elevated intracranial pressure, whereas healthy control volunteers demonstrated no imaging abnormalities. All patients had elevated opening pressure (median, 36.0 cm water), decreased by the removal of CSF to a median closing pressure of 17.0 cm water. Patients pre-lumbar puncture had significantly smaller pontine displacement than they did post-lumbar puncture after CSF pressure reduction (P = .001) and compared with controls (P = .01). Post-lumbar puncture patients had statistically similar pontine displacements to controls. Measured CSF pressure in patients pre- and post-lumbar puncture correlated significantly with pontine displacement (r = 0.49; P = .04).

CONCLUSIONS

This study establishes a relationship between pontine displacement from DENSE MR imaging and measured pressure obtained contemporaneously by lumbar puncture, providing a method to noninvasively assess intracranial pressure status in idiopathic intracranial hypertension.

Imaging of Intracranial Pressure Disorders

Intracranial pressure (ICP) is the pressure inside the bony calvarium and can be affected by a variety of processes, such as intracranial masses and edema, obstruction or leakage of cerebrospinal fluid, and obstruction of venous outflow. This review focuses on the imaging of 2 important but less well understood ICP disorders: idiopathic intracranial hypertension and spontaneous intracranial hypotension. Both of these ICP disorders have salient imaging findings that are important to recognize to help prevent their misdiagnosis from other common neurological disorders.

Chiari Type 1 Malformation-induced Intracranial Hypertension with Diffuse Brain Edema Treated with Foramen Magnum Decompression: A Case Report

Chiari type 1 malformation (CM1) rarely causes papilloedema, which is indicative of high intracranial pressure with or without ventricular dilatation. Furthermore, concomitant brain parenchymal abnormalities have not been reported to date. In this paper, the authors report on a young woman of CM1-induced intracranial hypertension (ICH) with diffuse brain edema with a focus on venous sinus assessment, and discuss the surgical strategy. A 24-year-old woman presented to Nagoya University Hospital complaining of 4-year history of severe occipital headache and blurry vision with slowly progressive worsening. Head and whole spine MRI showed a CM1 with diffuse white matter hyperintensities (WMH) on T2-weighted imaging and narrowed brain sulci without hydrocephalus. Lumbar puncture revealed extremely high opening pressure. Detailed blood examination and other radiographical imaging studies denied the presence of tumor, collagen disease, encephalitis and other entities. Head magnetic resonance venography and angiography demonstrated severe transverse sinus stenosis on both sides. Foramen magnum decompression was performed to alleviate the ICH by restoration of cerebrospinal fluid (CSF) stagnation at the foramen magnum with successful outcome. The patient completely recovered from preoperative symptoms immediately after surgery. The diffuse WMH and narrowing brain sulci have been resolving. The most feasible explanation for this complicated pathophysiology was ICH induced by CM1 led to transverse sinus collapse, resulting in diffuse WMH as a result of venous hypertension. This case report is the first illustration of successful surgical treatment of CM1 with diffuse brain edema with a focus on venous sinus assessment.

Imaging of Cerebrospinal Fluid Rhinorrhea and Otorrhea

As the obesity epidemic grows in the United States, rhinorrhea and otorrhea from spontaneous cerebrospinal fluid (CSF) leaks secondary to untreated idiopathic intracranial hypertension are increasing in prevalence. CSF rhinorrhea and otorrhea should also be carefully evaluated in posttraumatic and postsurgical settings, because untreated CSF leaks often have serious consequences. The work-up, diagnosis, and characterization of a CSF leak can be complex, often requiring a multimodality approach to optimize surgical planning. This article reviews the causes of CSF leaks, describes the methodology used to work up a suspected leak, and discusses the challenges of making an accurate diagnosis.

Imaging Features of Idiopathic Intracranial Hypertension in Children

Magnetic resonance imaging (MRI) signs of elevated intracranial pressure and idiopathic intracranial hypertension have been well characterized in adults but not in children. The MRIs of 50 children with idiopathic intracranial hypertension and 46 adults with idiopathic intracranial hypertension were reviewed for optic nerve head protrusion, optic nerve head enhancement, posterior scleral flattening, increased perioptic cerebrospinal fluid, optic nerve tortuosity, empty or partially empty sella, tonsillar herniation, enlargement of Meckel's cave meningoceles, and transverse venous sinus stenosis(TSS). Compared to adolescents (11-17 years, n = 40) and adults (>17 years, n = 46), prepubescent children (<11 years, n = 10) had lower frequencies of scleral flattening (50% vs 89% and 85%, P = .02), increased perioptic cerebrospinal fluid (60% vs 84% and 89%, P = .08), optic nerve tortuosity (20% vs 46% and 59%, P = .07), empty or partially empty sella (56% vs 78% and 93%, P = .007), and TSS (67% vs 93% and 96%, P = .04). Children with idiopathic intracranial hypertension have similar MRI findings as adults, but they are less frequent in prepubescent children.