Indentation and Transverse Diameter of the Meckel Cave: Imaging Markers to Diagnose Idiopathic Intracranial Hypertension

Calcitonin gene-related peptide in newly diagnosed idiopathic intracranial hypertension: a prospective, cross-sectional, case-control study of cerebrospinal fluid and plasma

BACKGROUND

Calcitonin Gene-Related Peptide (CGRP) is involved in migraine pain signaling, and blockage hereof is effective in migraine treatment. Headache in idiopathic intracranial hypertension (IIH) is often migraine-like but the underlying mechanisms are not understood. We report levels of CGRP in plasma and cerebrospinal fluid (CSF) of patients with newly diagnosed IIH to elucidate CGRP involvement in the pathogenesis of headache in IIH.

METHOD

We consecutively enrolled patients suspected of having IIH in a prospective cohort at two Danish tertiary headache centers. Patients are confirmed to have IIH or disproven of it (non-IIH). We included non-IIH with primary headache disorders as headache controls to IIH cases. We also recruited sex-, age- and BMI-matched healthy controls (HC). All participants had CSF and blood drawn and CGRP was analyzed using a validated radioimmunoassay. CSF plasma-ratios were calculated. Between-group levels were compared with ANOVA or Kruskal-Walli's test. In sub-analyses we restricted comparison of HC to non-IIH/IIH with chronic migraine; we also compared IIH with versus without headache. We correlated CGRP to lumbar opening pressure (OP), and BMI, and assessed the correlation between CGRP in plasma and CSF. Generalized or linear regression was applied to adjust for confounding by BMI, age, and active smoking.

RESULTS

Comparing 97 patients with IIH, 52 non-IIH, and 37 HC, we found no between-group differences in CGRP levels in plasma (p = 0.78), CSF (p = 0.79), or in CSF:plasma-ratio (p = 0.13). Adjusting for BMI, age, and smoking yielded similar results. CGRP levels were neither associated with having a migraine phenotype or chronic headache, nor with having any headache versus no headache in IIH. CGRP in plasma correlated with CGRP in CSF (p < 0.0001). CGRP did not correlate with OP or BMI.

CONCLUSION

CGRP levels in plasma and CSF and their ratios were comparable in IIH, non-IIH patients with headache, and sex-, age-, and BMI-matched HC. CGRP in plasma correlated with CGRP in CSF. Due to methodology, we probably measured basal resting CGRP. The role of CGRP in IIH-headache needs further clarification. A headache preventive effect in IIH of anti-CGRP targeted therapy remains a relevant unexplored area.

Idiopathic intracranial hypertension: Imaging and clinical fundamentals

Neuroimaging is a paramount element for the diagnosis of idiopathic intracranial hypertension, a condition characterized by signs and symptoms of raised intracranial pressure without the identification of a mass or hydrocephalus being recognized. The primary purpose of this review is to deliver an overview of the spectrum and the specific role of the various imaging findings associated with the condition while providing imaging examples and educational concepts. Clinical perspectives and insights into the disease, including treatment options, will also be discussed.

Imaging of Vertigo and Dizziness: A Site-based Approach Part 3 (Brainstem, Cerebellum, and Miscellaneous)

Dizziness and vertigo, frequently associated with cerebrovascular origins, pose a substantial challenge in emergency medical settings due to their potential to be associated with severe underlying conditions. Sudden-onset dizziness, in particular, may be an early indicator of critical events such as stroke or transient ischemic attack. This comprehensive review encompasses the differential diagnosis of central causes of dizziness and vertigo, emphasizing the crucial role of imaging modalities in the accurate detection and assessment, including cerebrovascular diseases, inflammatory disorders, infections, and other conditions such as vestibular migraine and cervical spondylosis. It highlights the significance of advanced imaging techniques, particularly magnetic resonance imaging and computed tomography in identifying and distinguishing these conditions.

Role of neuroimaging markers on predicting of idiopathic intracranial hypertension

BACKGROUND

The goals of neuroimaging in idiopathic intracranial hypertension (IIH) are the exclusion of mimickers and effective management of disease. In recent studies, several imaging markers have been identified as potential predictors of IIH.

PURPOSE

To investigate the predictive roles of novel radiological markers as the Meckel's cave area, alongside classical radiologic markers in identifying IIH such as the empty sella.

MATERIAL AND METHODS

The patients were classified according to cerebrospinal fluid (CSF) opening pressure as the IIH group and control group. The observational, case-control study included 22 patients with IIH and 22 controls. Groups were compared for presence of empty sella, Meckel's cave area, fat area of posterior neck, fat thickness of scalp, presence of transverse sinus stenosis, and ophthalmic markers, such as increase of optic nerve (ON) sheath diameter.

RESULTS

In the IHH group, higher occurrences of increased ON sheath diameter, ON tortuosity, flattening of the scleral surface, and transverse sinus stenosis were observed (P < 0.001, P < 0.001, P = 0.046, and P = 0.021, respectively). Meckel's cave area and fat area of posterior neck were similar in both groups (P = 0.444 and P = 0.794).

CONCLUSION

Ophthalmic markers and transverse sinus stenosis could be utilized as radiologic features supporting early and precise diagnosis of IIH. However, enlargement of Meckel's cave area and measurements of fatty area of posterior neck are not helpful for diagnosis of IIH.

A novel case of Horner syndrome as the presenting sign of craniosynostosis

Craniosynostosis, the premature fusion of cranial sutures, can lead to distortion of skull shape and neurological dysfunction. We present a novel case of Horner syndrome as the presenting sign of craniosynostosis associated with elevated intracranial pressure. A 10-year-old boy presenting for strabismus follow-up was noted to have new-onset anisocoria, greater in the dark, and mild right upper eyelid ptosis. Apraclonidine testing was concerning for Horner syndrome. Neuroimaging demonstrated previously undiagnosed sagittal craniosynostosis with tortuous optic nerves and large cerebrospinal fluid spaces around both optic nerves. The patient was referred to neurosurgery and underwent a lumbar puncture with an opening pressure of 44 cm H2O. He underwent surgical cranial expansion. By six months postoperatively, his anisocoria had resolved.

Interthalamic Adhesion: Can it be used to Diagnose Idiopathic Intracranial Hypertension?

OBJECTIVE

This retrospective study aimed at determining the dimension of the interthalamic adhesion (ITA) in patients with the idiopathic intracranial hypertension (IIH) for assisting in preoperative radiologic diagnosis.

METHODS

The study universe consisted of magnetic resonance images of 20 patients with IIH (age: 22.70 ± 4.04 years, sex: 14 females and 6 males) and 20 normal subjects (age 22.30± 2.94 years, sex: 14 females and 6 males). To determine the morphology of ITA, its height (vertical diameter) and width (horizontal diameter) were measured on the coronal and axial planes, respectively.

RESULTS

The height and width of ITA in IIH were measured as 2.58 ± 0.71 mm (range: 1.40-4.20 mm) and 2.73 ± 0.77 mm (range: 1.70-4.40 mm), respectively. Its height and width in controls were measured as 4.99 ± 1.04 mm (range: 2.70-6.30 mm) and 4.92 ± 1.11 mm (range: 2.60-6.50 mm), respectively. ITA height and width in IIH was significantly smaller compared with controls (P < 0.001). For an arbitrary cutoff of 3.85 mm, the sensitivity of the height of ITA was 85% with 95% specificity. For an arbitrary cutoff of 4.45 mm, the sensitivity of the width of ITA was 75% with 100% specificity.

CONCLUSIONS

The height and width of ITA are approximately 50% smaller in IIH than controls; therefore alterations in the dimension of ITA may be a valuable radiologic sign for the diagnosis of IIH.

Debilitating trigeminal neuralgia secondary to idiopathic intracranial hypertension

Idiopathic intracranial hypertension (IIH) is characterized by raised intracranial pressure with unknown etiology. The most common neurological manifestations are headache and visual loss. Often, other cranial nerve impairments are also found, most commonly in the VI nerve. Trigeminal neuralgia (TN) is a debilitating condition that is most frequently caused by neurovascular pathology, but TN secondary to IIH is a rare and poorly described topic. Possible explanations of TN in these patients include the distortion of the local anatomy at CN entry zones and fluid displacement causing distortion of the Meckel's cave. In the case below we describe the clinical course of an obese female patient with TN-like pain who underwent a ventriculoperitoneal shunt to treat IIH and experienced complete resolution of both conditions.

The Consistency Between the Preoperative 3D-Reconstructed Meckel's Cave and the Intraoperative Balloon Results in Percutaneous Balloon Compression

OBJECTIVE

To predict the volume and shape of the balloon before PBC by reconstructing the Meckel's cave (MC) and establishing a volumetric measurement model, supporting preoperative preparation and intraoperative decisions.

METHODS

The clinical data of 31 patients with good therapeutic effects who underwent PBC are retrospectively collected, including preoperative MRI, the volume of contrast agent injected into the balloon, and intraoperative lateral X-ray images. The MC on the affected side of the 31 patients is reconstructed based on MRI using 3D Slicer, while the volume of the MC is calculated to compare with the volume of contrast agent. The width (W) and length (L) of the model of the MC in lateral view are measured and used to classify the shape of the MC based on W/L. The consistency between the W/L of the model of the MC and the W/L of the intraoperative balloon is evaluated.

RESULTS

For volume, the mean value of the models of the MC (V1) in 31 patients is 399.77±155.13 mm³, while the mean value of the contrast agent injected during PBC (V2) is 539.03±111.93 mm³. The formula obtained by linear regression is V2= 392.1 + 0.3676×V1. Based on the value of W/L, the shape of the MC is classified into thin "pear" in 5 patients (16.13%), standard "pear" in 22 patients (70.97%), and square "pear" in 4 patients (12.90%). There is no significant difference in W/L between the models of the MC and the intraoperative balloons in 31 patients (P=0.221).

CONCLUSION

In 31 patients with good efficacy, it is verified that the prediction of the MC before PBC by 3D Slicer is consistent with the actual situation of the intraoperative balloon. This method can provide certain basis for preoperative preparation and intraoperative judgment.

How to understand an enlarged Meckel's cave? An anatomical study

PURPOSE

Dilatation of the trigeminal cavum, or Meckel's cave (MC), is usually considered a radiological sign of idiopathic intracranial hypertension. However, the normal size of the trigeminal cavum is poorly characterized. In this study, we describe the anatomy of this meningeal structure.

METHODS

We dissected 18 MCs and measured the length and width of the arachnoid web and its extension along the trigeminal nerve.

RESULTS

Arachnoid cysts were clearly attached to the ophthalmic (V1) and maxillary (V2) branches until they entered the cavernous sinus and foramen rotundum, respectively, without extension to the skull base. Arachnoid cysts were close to the mandibular branch toward the foramen ovale, with a median anteromedial extension of 2.5 [2.0-3.0] mm, lateral extension of 4.5 [3.0-6.0] mm, and posterior extension of 4.0 [3.2-6.0] mm. The trigeminal cavum arachnoid had a total width of 20.0 [17.5-25.0] mm and length of 24.5 [22.5-29.0] mm.

CONCLUSION

Our anatomical study revealed variable arachnoid extension, which may explain the variability in size of the trigeminal cavum in images and calls into question the value of this structure as a sign of idiopathic intracranial hypertension. The arachnoid web extends beyond the limits described previously, reaching almost double the radiological size of the cavum, particularly at the level of V3 afference of the trigeminal nerve. It is possible that strong adhesion of the arachnoid to the nerve elements prevents the formation of a true subarachnoid space that can be visualized by magnetic resonance imaging.

Introducing the "Temporal Thumb Sign" in Pediatric Patients With New-Onset Idiopathic Seizures With and Without Elevated Cerebrospinal Fluid Opening Pressure

BACKGROUND

Temporal lobe changes, such as anterior temporal lobe meningoceles or encephaloceles, have been documented as possible epileptogenic foci in a subset of pediatric patients with seizures. In our study, we aim to analyze a different structural change in the temporal lobe, remodeling of the posterior temporal skull base by the inferior temporal gyrus called the "temporal thumb sign" (TTS), in pediatric patients presenting with new-onset seizures with or without elevated opening pressure (OP), patients presenting with confirmed diagnosis of idiopathic intracranial hypertension (IIH) without seizure presentation, and healthy controls.

METHODS

Magnetic resonance imaging scans of 163 pediatric patients were studied retrospectively for the presence of TTS. We analyzed the scans of 43 patients with elevated OP and confirmed IIH, 40 patients with elevated OP and new-onset idiopathic seizures, 40 patients with normal OP and new-onset idiopathic seizures, and 40 age- and sex-matched healthy controls.

RESULTS

The TTS was detected most frequently in patients with elevated OP and seizures at 72.5% compared with patients with IIH with no seizures and patients with normal OP and seizures (32.6% and 27.5%, respectively). The TTS had a frequency of 12.5% in the control group. The TTS had the highest combination of specificity and sensitivity (72.5% and 72.5%) in patients with seizures and elevated OP compared with patients with seizures and normal OP (P value < 0.001).

CONCLUSIONS

Our results suggest the Kamali "temporal thumb sign" is a novel imaging feature that may be used as a sensitive and specific imaging finding associated with seizures and elevated OP in the pediatric population.

Expanding the clinical spectrum of idiopathic intracranial hypertension

PURPOSE OF REVIEW

Idiopathic intracranial hypertension (IIH) is a disorder of raised intracranial pressure (ICP). Although the majority of patients with IIH present classically with headache and papilledema, some patients may have unusual presentations or manifestations. Recent advancements in neuroimaging have facilitated the identification of other presentations associated with IIH. This review provides an overview of the expanding clinical spectrum of IIH.

RECENT FINDINGS

Presentations of IIH that are considered unusual include highly asymmetric or unilateral papilledema, IIH without papilledema, and IIH associated with cranial nerve involvement. These presentations likely reflect differences in the way cerebrospinal fluid (CSF) pressure is transmitted intracranially. Radiological signs of intracranial hypertension are increasingly recognized in patients with IIH and provide further insights into the effects of raised ICP on intracranial structures. Osseous changes in the skull base leading to formation of meningoceles and encephaloceles have been identified in patients with IIH, spontaneous skull base CSF leak, and drug-resistant temporal lobe epilepsy, suggesting a possible association.

SUMMARY

Clinicians should be familiar with the expanding clinical spectrum of IIH and the implications for the management of these presentations.

Efficacy of Dural Sinus Quantitative Measurements in Idiopathic Intracranial Hypertension : A Practical Diagnostic Feature

BACKGROUND AND PURPOSE

This study aimed to investigate the potential contribution of quantitative measurements of dural venous sinuses to the diagnosis of idiopathic intracranial hypertension (IIH) and the relationship between IIH and dural venous sinus dimensions on 3D post-gadolinium T1-weighted magnetic resonance (MR) images.

MATERIAL AND METHODS

A total of 129 individuals (57 IIH patients and 72 controls) who complained of headache and underwent both magnetic resonance venography (MRV) and precontrast/postcontrast 3D T1-weighted MR imaging between 2018 and 2021 were included in this retrospective study. Dural venous sinus and jugular vein diameters were measured in all cases using post-gadolinium 3D T1 TFE images. The presence of transverse sinus (TS) hypoplasia and occipital sinus variation, the number and size of arachnoid granulations in the TS, and the presence of brain parenchymal herniation were also evaluated. Cut-off values that maximized accurate diagnosis of IIH were established on the receiver operating characteristic curve. The sensitivity and specificity of the diagnosis of IIH based on quantitative measurements of the dural sinus were calculated.

RESULTS

The ratios of the maximum to minimum TS diameters and the minimum TS diameters to minimum sigmoid sinus (SS) diameters were significantly higher in IIH patients than in the control group (p < 0.001). The diagnostic sensitivity and specificity values of TS_max/TS_min and TS_{min sum}/SS_{min sum} parameters for the detection of IIH were 84.2%, 84.7% and 83.3%, 84.2%, respectively.

CONCLUSION

Practical measurements from multiplanar T1 sequences can be useful for both quantitative assessment and overcoming misinterpretation due to anatomical variation.

Accuracy and reliability of magnetic resonance imaging in the diagnosis of idiopathic intracranial hypertension

PURPOSE

To determine the diagnostic utility of brain magnetic resonance imaging (MRI) findings in patients with idiopathic intracranial hypertension (IIH) and to investigate the significance of evaluating radiological findings together with neurological and ophthalmological data in the diagnosis of IIH.

MATERIALS AND METHODS

All consecutive patients diagnosed with IIH in our tertiary neuro-ophthalmology center between January 1, 2018 and March 15, 2020, were included in the study. The clinical, radiological, and ophthalmological findings of IIH patients were compared with the control group with similar demographic characteristics.

RESULTS

A total of 98 patients, 49 cases and 49 controls, were included in the study. Lateral ventricular index had the highest area under the curve (AUC) value (0.945) for prediction of disease group followed by sella height category (AUC = 0.915) and optic nerve tortuosity (AUC = 0.855) According to the multivariate model we developed, caudate index (OR = 0.572, 95% CI 0.329-0.996), lateral ventricle index (OR = 3.969, 95% CI 1.851-8.509) and bilateral optic nerve tortuosity (OR = 22,784, 95% CI 2.432-213.450) were significant predictors for disease group.

CONCLUSION

Tortuosity in the optic nerve, lateral ventricular index and caudate index can be used as MRI parameters supporting the diagnosis of IIH in clinically suspicious cases. A holistic approach to the clinical and radiological findings of the cases in the diagnosis of IIH can prevent overdiagnosis and enable early correct diagnosis.

Neuroimaging Features of Intracranial Hypertension in Pediatric Patients With New-Onset Idiopathic Seizures, a Comparison With Patients with Confirmed Diagnosis of Idiopathic Intracranial Hypertension: A Preliminary Study

A cutoff value of 6.0 mm for optic nerve sheath dilation may be used as a screening imaging marker to suspect elevated opening pressure with specificity of 88% in pediatric patients with new-onset idiopathic seizures.

Flatness of the Meckel cave may cause primary trigeminal neuralgia: a radiomics-based study

Background

Neurovascular contact (NVC) is the main cause of primary trigeminal neuralgia (PTN); however, cases of PTN without NVC are still observed. In this study, the Meckel cave (MC) morphology in PTN were analyzed by radiomics and compared to healthy controls (HCs) to explore the cause of PTN.

Methods

We studied the 3.0T MRI data of 115 patients with PTN and 46 HCs. Bilateral MC was modeled using the 3D Slicer software, and the morphological characteristics of MC were analyzed using the radiomics method.

Results

The right side incidence rate in the PTN group was higher than the left side incidence. By analyzing the flatness feature of MC, we observed that the affected side of the PTN was lower than that of the unaffected side, the right MC of the PTN and HC was lower than that of the left MC, the MC of the affected side of the left and right PTN without bilateral NVC was lower than that of the unaffected side.

Conclusions

By providing a method to analyze the morphology of the MC, we found that there is an asymmetry in the morphology of bilateral MC in the PTN and HC groups. It can be inferred that the flatness of the MC may be a cause of PTN.

Meckel Cave: An Anatomical Study Using Magnetic Resonance Imaging

OBJECTIVE

To our knowledge, few studies have investigated anatomy of the Meckel cave with neuroimaging modalities. The present study aimed to characterize it using magnetic resonance imaging (MRI).

PATIENTS AND METHODS

Following conventional MRI examination, a total of 101 patients underwent T2-weighted imaging in thin-sliced coronal and sagittal sections, and 11 patients underwent constructive interference steady-state sequences in thin-sliced sagittal sections. Moreover, 3 injected cadaver heads were dissected.

RESULTS

In the cadaver specimens, the size and extent of the cerebrospinal fluid-filled space between the Gasserian ganglion and surrounding arachnoids were difficult to define. On the T2-weighted imaging, the Meckel cave was delineated with variable morphologies and left-right asymmetry. On the sagittal images, the shape of the Meckel cave could be classified into 3 different types, bulbous, oval, and flat, with the oval being the most frequent that comprised 60%. Furthermore, on the sagittal constructive interference steady-state images, parts of the trigeminal nerve distributed in the Meckel cave were delineated in all patients. The ophthalmic, maxillary, and mandibular divisions were clearly distinguished on both sides.

CONCLUSIONS

The Meckel cave is a structure characterized by diverse morphologies and left-right asymmetry. Thin-sliced T2-weighted imaging is useful for exploring the anatomy of the Meckel cave.