Pediatric Idiopathic Intracranial Hypertension Presenting With Sensorineural Hearing Loss

A New Perspective on the Pathophysiology of Idiopathic Intracranial Hypertension: Role of the Glia-Neuro-Vascular Interface

Idiopathic intracranial hypertension (IIH) is a neurological disease characterized by symptoms and signs of increased intracranial pressure (ICP) of unknown cause. Most attention has been given to the role of cerebrospinal fluid (CSF) disturbance and intracranial venous hypertension caused by sinus vein stenosis. We previously proposed that key pathophysiological processes take place within the brain at the glia-neuro-vascular interface. However, the relative importance of the proposed mechanisms in IIH disease remains unknown. Modern treatment regimens aim to reduce intracranial CSF and venous pressures, but a substantial proportion of patients experience lasting complaints. In 2010, the first author established a database for the prospective collection of information from individuals being assessed for IIH. The database incorporates clinical, imaging, physiological, and biological data, and information about treatment/outcome. This study retrieved information from the database, asking the following research questions: In IIH subjects responding to shunt surgery, what is the occurrence of signs of CSF disturbance, sinus vein stenosis, intracranial hypertension, and microscopic evidence of structural abnormalities at the glia-neuro-vascular interface? Secondarily, do semi-quantitative measures of abnormal ultrastructure at the glia-neurovascular differ between subjects with definite IIH and non-IIH (reference) subjects? The study included 13 patients with IIH who fulfilled the diagnostic criteria and who improved following shunt surgery, i.e., patients with definite IIH. Comparisons were done regarding magnetic resonance imaging (MRI) findings, pulsatile and static ICP scores, and immune-histochemistry microscopy. Among these 13 IIH subjects, 6/13 (46%) of patients presented with magnetic resonance imaging (MRI) signs of CSF disturbance (empty sella and/or distended perioptic subarachnoid spaces), 0/13 (0%) of patients with IIH had MRI signs of sinus vein stenosis, 13/13 (100%) of patients with IIH presented with abnormal preoperative pulsatile ICP [overnight mean ICP wave amplitude (MWA) above thresholds], 3/13 (23%) patients showed abnormal static ICP (overnight mean ICP above threshold), and 12/13 (92%) of patients with IIH showed abnormal structural changes at the glia-neuro-vascular interface. Comparisons of semi-quantitative structural variables between IIH and aged- and gender-matched reference (REF) subjects showed IIH abnormalities in glial cells, neurons, and capillaries. The present data suggest a key role of disease processes affecting the glia-neuro-vascular interface.

Sensorineural Hearing Loss and Tinnitus Characteristics in Patients With Idiopathic Intracranial Hypertension

OBJECTIVES

To characterize patterns of sensorineural hearing loss (SNHL) and tinnitus in patients with idiopathic intracranial hypertension (IIH).

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

PATIENTS

Adult patients diagnosed with IIH via lumbar puncture (LP) between 2010 and 2020 who had available audiograms. The study included a total of 40 patients; 33 women, and 7 men with a median age of 43.

INTERVENTIONS

Diagnostic LP and audiogram.

MAIN OUTCOME MEASURES

Otologic symptoms, ophthalmologic signs, hearing thresholds, cerebrospinal fluid opening pressures.

RESULTS

The most commonly reported symptoms were tinnitus in 28 (70%, 23 pulsatile and 5 tonal), aural fullness in 11 (28%), and vertigo in 10 (25%). Twenty-nine patients had ophthalmologic examinations and 18 had evidence of papilledema. Twenty-five (63%) patients had hearing loss in at least one ear at one frequency range. Patients presented with both unilateral and bilateral hearing loss across low, middle, and high frequency ranges. No significant association was observed between hearing loss threshold and LP opening pressure except for 250 Hz in the left ear. After stratification by tinnitus group (pulsatile, tonal, and no tinnitus), no significant difference was found between mean hearing loss threshold at different frequencies. In addition, no significant mean age difference was identified in patients within each tinnitus group.

CONCLUSIONS

There was no classic pattern or presentation for hearing loss in our IIH patients. They developed sudden, unilateral, or bilateral SNHL in low, middle, or high frequency range. The degree of hearing loss did not correlate with CSF opening pressure.

Increased occurrence of pathological mitochondria in astrocytic perivascular endfoot processes and neurons of idiopathic intracranial hypertension

Idiopathic intracranial hypertension (IIH) primarily affects fertile, overweight women, and presents with the symptoms of raised intracranial pressure. The etiology is unknown but has been thought to relate to cerebrospinal fluid disturbance or cerebral venous stenosis. We have previously found evidence that IIH is also a disease of the brain parenchyma, evidenced by alterations at the neurogliovascular interface, including astrogliosis, pathological changes in the basement membrane and pericytes, and alterations of perivascular aquaporin-4. The aim of this present electron microscopic study was to examine whether mitochondria phenotype was changed in IIH, particularly focusing on perivascular astrocytic endfeet and neurons (soma and pre- and postsynaptic terminals). Cortical brain biopsies of nine reference individuals and eight IIH patients were analyzed for subcellular distribution and phenotypical features of mitochondria using transmission electron microscopy. We found significantly increased prevalence of pathological mitochondria and reduced number of normal mitochondria in astrocytic endfeet of IIH patients. The degree of astrogliosis correlated negatively with the number of normal mitochondria in astrocytic endfoot processes. Moreover, we found significantly increased number of pathological mitochondria in pre- and postsynaptic neuronal terminals, as well as significantly shortened distance between mitochondria and endoplasmic reticulum contacts. Finally, the length of postsynaptic density, a marker of synaptic strength, was on average reduced in IIH. The present data provide evidence of pathological mitochondria in perivascular astrocytes endfeet and neurons of IIH patients, highlighting that impaired metabolism at the neurogliovascular interface may be a facet of IIH.

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.

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.

Idiopathic Intracranial Hypertension Presenting as Auditory Neuropathy Hearing Disorder in a Child

Otologic manifestations are known to occur in patients with idiopathic intracranial hypertension (IIH), but the occurrence of sensorineural hearing loss, especially in pediatric populations, has been addressed in only a few reports. Here, we describe a pediatric patient who presented with IIH and severe bilateral hearing loss. The patient's hearing loss was diagnosed as a form of auditory neuropathy (AN) and resolved after prompt treatment of the increased intracranial pressure. This case points to a possible association between IIH and AN and suggests that IIH may potentially be a reversible cause of AN spectrum disorder. Laryngoscope, 129:E407-E411, 2019.

Idiopathic intracranial hypertension: Proposal of a stratification strategy for monitoring risk of disease progression

OBJECTIVES

A general consensus based on a multidisciplinary perspective involving an international panel was recently developed for management of patients with idiopathic intracranial hypertension (IIH). In this paper, the authors sought to develop further on the aspect of this consensus that concerns monitoring progression of the disease.

PATIENTS AND METHODS

A systematic literature review of previous publications on monitoring disease progression in IIH and a meta-analysis to examine efficacy of method of monitoring employed in each study. The authors present a brief descriptive analysis of challenges with monitoring progression of the disease and propose a risk stratification to aid monitoring.

RESULTS

Of a total of 382 publications identified from the literature search, only 8 studies (144 patients) satisfied inclusion criteria and were included for analysis. Among these, 3 were based on ICP monitoring while the remaining 5 focused on ophthamological evaluation. Interestingly, there were neither any studies on monitoring with progression of clinical features nor any study on monitoring with symptomatology associated with IIH among the selected studies.

CONCLUSION

There is a paucity of studies in the literature on methods of monitoring disease progression in IIH. Though close attention to adequate evaluation and proper care of patients with IIH remains the key in managing this problem, this proposed risk stratification will be an objective tool and useful guide to better monitor these patients according to their extent of risk from the disease and possibly for planning treatment and intervention.