Endolymphatic hydrops in idiopathic intracranial hypertension: prevalence and clinical outcome after lumbar puncture. Preliminary data

What should otolaryngologists know about dural venous sinus stenting?

Dural venous sinus stenting is an emerging and exciting area in otolaryngology in collaboration with neurosurgeons and neuroradiologists. The first cases were reported 20 years ago. It is now considered part of the routine treatment of increased intracranial pressure due to transverse sinus stenosis. ENT doctors are the first to see these patients in their clinics, as sinus headaches, pulsating tinnitus, and dizziness are the most common symptoms. Previously, with limited success, high-dose diuretics and intracranial shunts had been the only options for treating these patients. Other methods, such as covering the sigmoid sinuses with graft material, appear to cause a sudden increase in intracranial pressure that can lead to blindness and even death. This overview summarizes the clinical and imaging characteristics of patients who will benefit from endovascular sinus stenting for elevated intracranial pressure.

Transverse sinus pathologies, vestibular migraine and intracranial hypertension without papilledema

BACKGROUND

In the absence of papilledema, the presentation of migraine and idiopathic intracranial hypertension (IIH) is very similar. In this respect, an IIH could be presented as a vestibular migraine. Our main objective in this case report is to demonstrate the similarities between IIH and vestibular migraine.

CASES

This is a report of 14 patients who have IIH without papilledema presented as vestibular migraine to the clinic and followed from 2020 to 2022.

RESULTS

The common presentation of patients was ear-facial pain, dizziness, and frequent pulsatile tinnitus. One-fourth of the patients reported episodes of true episodic vertigo. The average age was 37.8, the average BMI was 37.4, and the average lumbar puncture-opening pressure was 25.6 cm H2O. Transverse sinus venous flow alterations caused neuroimaging findings of sigmoid sinus dehiscence, empty sella, or tonsillar ectopia. Most patients improved with carbonic anhydrase inhibitors, and one patient was treated with a dural sinus stent.

CONCLUSION

A transverse sinus stenosis, even in the non-dominant site, may elevate the CSF pressure in obese individuals. This stenosis causes dural sinus-related pulsatile tinnitus with characteristics different from those of an arterial origin. Dizziness is a common complaint in patients with IIH, just like VM. In our opinion, episodic vertigo in these patients is the direct effect of CSF flow alterations into the inner ear's vestibule. Patients with mild elevations will be presented to the clinic, similar to migraines with or without the presence of pulsatile tinnitus. Treatment requires lowering intracranial pressure and managing migraine symptoms.

The Link Between Empty Sella Syndrome, Fibromyalgia, and Chronic Fatigue Syndrome: The Role of Increased Cerebrospinal Fluid Pressure

The etiopathogenesis of fibromyalgia (FM) and chronic fatigue syndrome (CFS) is not yet elucidated. Hypothalamo-pituitary-adrenal (HPA) axis dysfunction is reflected in the hormonal disturbances found in FM and CFS. Some study groups have introduced a novel hypothesis that moderate or intermittent intracranial hypertension may be involved in the etiopathogenesis of FM and CFS. In these conditions, hormonal disturbances may be caused by the mechanical effect of increased cerebrospinal fluid pressure, which hampers blood flow in the pituitary gland. Severe intracranial pressure may compress the pituitary gland, resulting in primary empty sella (ES), potentially leading to pituitary hormone deficiencies. The aim of this narrative review was to explore whether similar hormonal changes and symptoms exist between primary ES and FM or CFS and to link them to cerebrospinal fluid pressure dysregulation. A thorough search of the PubMed and Web of Science databases and the reference lists of the included studies revealed that several clinical characteristics were more prevalent in primary ES, FM or CFS patients than in controls, including increased cerebrospinal fluid pressure, obesity, female sex, headaches and migraine, fatigue, visual disturbances (visual acuity and eye motility abnormalities), vestibulocochlear disturbances (vertigo and neurosensorial hearing loss), and bodily pain (radicular pain and small-fiber neuropathy). Furthermore, challenge tests of the pituitary gland showed similar abnormalities in all three conditions: blunted adrenocorticotropic hormone, cortisol, growth hormone, luteinizing hormone, and thyroid stimulating hormone responses and an increased prolactin response. The findings of this narrative review provide further support for the hypothesis that moderately or intermittently increased cerebrospinal fluid pressure is involved in the pathogenesis of FM and CFS and should stimulate further research into the etiopathogenesis of these conditions.

Endolymphatic space is age-dependent

Knowledge of the physiological endolymphatic space (ELS) is necessary to estimate endolymphatic hydrops (ELH) in patients with vestibulocochlear syndromes. Therefore, the current study investigated age-dependent changes in the ELS of participants with normal vestibulocochlear testing. Sixty-four ears of 32 participants with normal vestibulocochlear testing aged between 21 and 75 years (45.8 ± 17.2 years, 20 females, 30 right-handed, two left-handed) were examined by intravenous delayed gadolinium-enhanced magnetic resonance imaging of the inner ear (iMRI). Clinical diagnostics included neuro-otological assessment, video-oculography during caloric stimulation, and head-impulse test. iMRI data analysis provided semi-quantitative visual grading and automatic algorithmic quantitative segmentation of ELS volume (3D, mm³) using a deep learning-based segmentation of the inner ear's total fluid space (TFS) and volumetric local thresholding, as described earlier. As a result, following a 4-point ordinal scale, a mild ELH (grade 1) was found in 21/64 (32.8%) ears uni- or bilaterally in either cochlear, vestibulum, or both. Age and ELS were found to be positively correlated for the inner ear (r(64) = 0.33, p < 0.01), and vestibulum (r(64) = 0.25, p < 0.05). For the cochlea, the values correlated positively without reaching significance (r(64) = 0.21). In conclusion, age-dependent increases of the ELS should be considered when evaluating potential ELH in single subjects and statistical group comparisons.

The potential significance of reversed stapes reflex in clinical practice in idiopathic intracranial hypertension

Background:

Stapes reflex test is a method of evaluating the involuntary muscle contraction of the stapedius muscle in response to a high-intensity sound stimulus. The formation of this reflex involves the intact function of the 7^th nerve, brain stem, 8^th nerve, and middle ear. Due to ease of administration and information yielded, the stapedial reflex is considered one of the most powerful differential diagnostic audiological procedures. Numerous studies have remarked on the fluid communication between the intracochlear and intracranial spaces through the cochlear aqueduct. Currently, the potential significance of a noninvasive audiological technique in the discrimination of raised intracranial pressure constitutes a crucial topic of interest.

Methods:

We have performed the pre-LP and post-LP detailed otorhinolaryngological investigations, including the detailed inspection, audiometric testing, tympanometry, and stapedial reflex in a total of four consecutive patients with IIH.

Results:

We found that the stapedial reflex was bilateral absent initially in two of the patients. However, the second stapedial reflex investigations after LP showed reversal of the reflex responses in both of the patients.

Conclusions:

We suggest some hypotheses and propose some clinical applications. Future studies focusing on the potential utility of this reflex in the monitorization of IIH may provide crucial perspectives.

Enhancement of subarachnoid space during magnetic resonance imaging of endolymphatic hydrops: a case report

Enhancement of the subarachnoid space after intravenous administration of gadolinium contrast agent is not common. Enhancement usually occurs in pathological conditions that increase the permeability of the blood–cerebrospinal fluid barrier, most notably in meningitis. We herein describe possible subarachnoid enhancement in patients with no apparent effect on the meninges. These patients had clinical signs of Meniere’s disease and underwent specific magnetic resonance imaging of the inner ear to possibly visualize endolymphatic hydrops. The endolymphatic space can be noninvasively imaged by intravenous administration of contrast agent, usually at a double dose, 4 hours before the scanning process. During this time, the contrast agent penetrates not only the perilymph but also the subarachnoid space, where the highest concentration occurs after 4 hours according to some studies.

Intracranial venous sinus stenting for the treatment of lateral sinus stenoses: An analysis of 200 patients

PURPOSE

The purpose of this study was to analyze the long-term efficacy and safety of intracranial venous sinus stenting in a large cohort of patients with any type of presentation of primary lateral venous sinus stenosis (VSS).

MATERIALS AND METHODS

A retrospective cohort study was performed including patients treated by venous sinus stenting for symptomatic VSS from 2012 to 2019. Successful primary resolution of symptoms without adjunctive treatment or recurrence, and complications after stenting were analyzed at the last follow-up time point.

RESULTS

Two-hundred patients were included. There were 14 men and 186 women with a mean age of 39±14 (SD) years (age range: 13-75 years). Presenting symptoms included venous pulsatile tinnitus in 168 patients (168/200; 84%), idiopathic intracranial hypertension in 100 patients (100/200; 50%) and/or spontaneous cerebrospinal fluid leak in 35 patients (35/200; 17%). The overall rate of successful primary resolution of any typical presenting symptoms was 79% (95% CI: 73-85%). This rate ranged from 74% to 93% depending on the symptom with no significant difference between patients with and those without idiopathic intracranial hypertension (P=0.08). Recurrence rate was 10% (95% CI: 6-14%). No death or permanent morbidity were observed during a median follow-up of 2.2 years (Q1, Q3: 1.4, 3.3; range: 1-7.7 years).

CONCLUSION

Our study shows that venous sinus stenting has a low morbidity and high success rate at long-term follow-up for the treatment of idiopathic intracranial hypertension, venous pulsatile tinnitus or spontaneous cerebrospinal fluid leak associated with VSS. The excellent safety suggests considering this treatment as first-line treatment when medical management is ineffective or poorly tolerated.

The neurologist and the hydrops

The presence of endolymphatic hydrops has been studied in many neurological disorders. The pathophysiological mechanisms may involve CSF pressure variations, transmitted to the innear ear. This hydrops could play a role in vestibular or cochlear symptoms. For the ENT specialist, the etiological diagnosis of endolymphatic hydrops is a challenge, and neurological etiologies must be known. The treatment of these neurological causes could be effective on cochleo-vestibular symptoms. The knowledge of endolymphatic hydrops could also be a target for noninvasive tests, able to estimate CSF pressure variations. For the neurologist, this could represent a useful tool for the diagnosis and follow-up, in some of these neurological disorders, related to a CSF pressure imbalance. The purpose of this paper is to summarize literature data on endolymphatic hydrops in neurological disorders. We define some neurological conditions, for which there is a particular interest in noninvasive investigations of endolymphatic hydrops.

Atypical presentations of idiopathic intracranial hypertension

Idiopathic intracranial hypertension (IIH) is a disorder of unknown etiology that results in isolated raised intracranial pressure. Classic symptoms and signs of IIH include headache, papilledema, diplopia from sixth nerve palsy and divergence insufficiency, and pulsatile tinnitus. Atypical presentations include: (1) highly asymmetric or even unilateral papilledema, and IIH without papilledema; (2) ocular motor disturbances from third nerve palsy, fourth nerve palsy, internuclear ophthalmoplegia, diffuse ophthalmoplegia, and skew deviation; (3) olfactory dysfunction; (4) trigeminal nerve dysfunction; (5) facial nerve dysfunction; (6) hearing loss and vestibular dysfunction; (7) lower cranial nerve dysfunction including deviated uvula, torticollis, and tongue weakness; (8) spontaneous skull base cerebrospinal fluid leak; and (9) seizures. Although atypical findings should raise a red flag and prompt further investigation for an alternative etiology, clinicians should be familiar with these unusual presentations.

VOLT: a novel open-source pipeline for automatic segmentation of endolymphatic space in inner ear MRI

Background

Objective and volumetric quantification is a necessary step in the assessment and comparison of endolymphatic hydrops (ELH) results. Here, we introduce a novel tool for automatic volumetric segmentation of the endolymphatic space (ELS) for ELH detection in delayed intravenous gadolinium-enhanced magnetic resonance imaging of inner ear (iMRI) data.

Methods

The core component is a novel algorithm based on Volumetric Local Thresholding (VOLT). The study included three different data sets: a real-world data set (D1) to develop the novel ELH detection algorithm and two validating data sets, one artificial (D2) and one entirely unseen prospective real-world data set (D3). D1 included 210 inner ears of 105 patients (50 male; mean age 50.4 ± 17.1 years), and D3 included 20 inner ears of 10 patients (5 male; mean age 46.8 ± 14.4 years) with episodic vertigo attacks of different etiology. D1 and D3 did not differ significantly concerning age, gender, the grade of ELH, or data quality. As an artificial data set, D2 provided a known ground truth and consisted of an 8-bit cuboid volume using the same voxel-size and grid as real-world data with different sized cylindrical and cuboid-shaped cutouts (signal) whose grayscale values matched the real-world data set D1 (mean 68.7 ± 7.8; range 48.9–92.8). The evaluation included segmentation accuracy using the Sørensen-Dice overlap coefficient and segmentation precision by comparing the volume of the ELS.

Results

VOLT resulted in a high level of performance and accuracy in comparison with the respective gold standard. In the case of the artificial data set, VOLT outperformed the gold standard in higher noise levels. Data processing steps are fully automated and run without further user input in less than 60 s. ELS volume measured by automatic segmentation correlated significantly with the clinical grading of the ELS (p < 0.01).

Conclusion

VOLT enables an open-source reproducible, reliable, and automatic volumetric quantification of the inner ears’ fluid space using MR volumetric assessment of endolymphatic hydrops. This tool constitutes an important step towards comparable and systematic big data analyses of the ELS in patients with the frequent syndrome of episodic vertigo attacks. A generic version of our three-dimensional thresholding algorithm has been made available to the scientific community via GitHub as an ImageJ-plugin.

Blood-Brain Barrier Dysfunction in Idiopathic Intracranial Hypertension

Idiopathic intracranial hypertension (IIH) is traditionally considered benign and characterized by symptoms related to increased intracranial pressure, including headache and impaired vision. We have previously demonstrated that brains of IIH patients exhibit patchy astrogliosis, increased perivascular expression of the water channel aquaporin-4 (AQP4) as well as degenerating pericyte processes and capillary basement membranes. Given the established association between pericyte degeneration and blood-brain barrier (BBB) dysfunction, we investigated blood protein leakage by light microscopic immunohistochemistry. We also assessed perivascular AQP4 expression by immunogold transmission electron microscopy. The study included 14 IIH patients and 14 reference (REF) subjects undergoing neurosurgery for epilepsy, aneurysm, or tumor. Evidence of BBB dysfunction, measured as area extravasated fibrinogen/fibrin, was significantly more pronounced in IIH than REF individuals. The extent of extravasated fibrinogen was positively correlated with increasing degree of astrogliosis and vascular AQP4 immunoreactivity, determined by light microscopy. Immunogold transmission electron microscopy revealed no overall changes in AQP4 expression at astrocytic vascular endfeet in IIH (n = 8) compared to REF (n = 11) individuals. Our results provide evidence of BBB leakage in IIH, signifying that IIH is a more serious neurodegenerative disease than previously considered.

Dural sinus collapsibility, idiopathic intracranial hypertension, and the pathogenesis of chronic migraine

Available evidences suggest that a number of known assumption on idiopathic intracranial hypertension (IIH) with or without papilledema might be discussed. These include (1) the primary pathogenetic role of an excessive dural sinus collapsibility in IIH, allowing a new relatively stable intracranial fluids pressure balance at higher values; (2) the non-mandatory role of papilledema for a definite diagnosis; (3) the possibly much higher prevalence of IIH without papilledema than currently considered; (4) the crucial role of the cerebral compliance exhaustion that precede the raise in intracranial pressure and that may already be pathologic in cases showing a moderately elevated opening pressure; (5) the role as "intracranial pressure sensor" played by the trigeminovascular innervation of dural sinuses and cortical bridge veins, which could represent a major source of CGRP and may explain the high comorbidity and the emerging causative link between IIHWOP and chronic migraine (CM). Accordingly, the control of intracranial pressure is to be considered a promising new therapeutic target in CM.

The link between idiopathic intracranial hypertension, fibromyalgia, and chronic fatigue syndrome: exploration of a shared pathophysiology

PURPOSE

Idiopathic intracranial hypertension (IICH) is a condition characterized by raised intracranial pressure (ICP), and its diagnosis is established when the opening pressure measured during a lumbar puncture is elevated >20 cm H2O in nonobese patients or >25 cm H2O in obese patients. Papilledema is caused by forced filling of the optic nerve sheath with cerebrospinal fluid (CSF). Other common but underappreciated symptoms of IICH are neck pain, back pain, and radicular pain in the arms and legs resulting from associated increased spinal pressure and forced filling of the spinal nerves with CSF. Widespread pain and also several other characteristics of IICH share notable similarities with characteristics of fibromyalgia (FM) and chronic fatigue syndrome (CFS), two overlapping chronic pain conditions. The aim of this review was to compare literature data regarding the characteristics of IICH, FM, and CFS and to link the shared data to an apparent underlying physiopathology, that is, increased ICP.

METHODS

Data in the literature regarding these three conditions were compared and linked to the hypothesis of the shared underlying physiopathology of increased cerebrospinal pressure.

RESULTS

The shared characteristics of IICH, FM, and CFS that can be caused by increased ICP include headaches, fatigue, cognitive impairment, loss of gray matter, involvement of cranial nerves, and overload of the lymphatic olfactory pathway. Increased pressure in the spinal canal and in peripheral nerve root sheaths causes widespread pain, weakness in the arms and legs, walking difficulties (ataxia), and bladder, bowel, and sphincter symptoms. Additionally, IICH, FM, and CFS are frequently associated with sympathetic overactivity symptoms and obesity. These conditions share a strong female predominance and are frequently associated with Ehlers-Danlos syndrome.

CONCLUSION

IICH, FM, and CFS share a large variety of symptoms that might all be explained by the same pathophysiology of increased cerebrospinal pressure.

Pulsatile versus non-pulsatile tinnitus in idiopathic intracranial hypertension

INTRODUCTION

Tinnitus is a symptom commonly associated with idiopathic intracranial hypertension (IIH) that can have a profound effect on quality of life. We aim to determine tinnitus symptom response after dural venous sinus stenting (DVSS) or CSF diversion with a shunt, in patients with both pulsatile (PT) and non-pulsatile tinnitus (NPT).

METHODS

Single-centre cohort of IIH patients (2006-2016) who underwent 24-h ICP monitoring (ICPM). An un-paired t test compared ICP and pulse amplitude (PA) values in IIH patients with PT vs. NPT.

RESULTS

We identified 59 patients with IIH (56 F:3 M), mean age 32.5 ± 9.49 years, 14 of whom suffered from tinnitus. Of these 14, seven reported PT and seven reported NPT. Patients with tinnitus had a mean 24-h ICP and PA of 9.09 ± 5.25 mmHg and 6.05 ± 1.07 mmHg respectively. All 7 patients with PT showed symptom improvement or resolution after DVSS (n = 4), secondary DVSS (n = 2) or shunting (n = 1). In contrast, of the 7 with NPT, only 1 improved post intervention (DVSS), despite 2 patients having shunts and 5 having DVSS.

CONCLUSIONS

NPT and PT were equally as common in our group of IIH patients. DVSS appears to be an effective management option for IIH patients with a clear history of pulsatile tinnitus. However, non-pulsatile tinnitus was more persistent and did not respond well to either DVSS or CSF diversion.