A Virtual Inner Ear Model Selects Ramped Pulse Shapes for Vestibular Afferent Stimulation.

Bilateral vestibular deficiency (BVD) results in chronic dizziness, blurry vision when moving the head, and postural instability. Vestibular prostheses (VPs) show promise as a treatment, but the VP-restored vestibulo-ocular reflex (VOR) gain in human trials falls short of expectations. We hypothesize that the slope of the rising ramp in stimulation pulses plays an important role in the recruitment of vestibular afferent units. To test this hypothesis, we utilized customized programming to generate ramped pulses with different slopes, testing their efficacy in inducing electrically evoked compound action potentials (eCAPs) and current spread via bench tests and simulations in a virtual inner model created in this study. The results confirmed that the slope of the ramping pulses influenced the recruitment of vestibular afferent units. Subsequently, an optimized stimulation pulse train was identified using model simulations, exhibiting improved modulation of vestibular afferent activity. This optimized slope not only reduced the excitation spread within the semicircular canals (SCCs) but also expanded the neural dynamic range. While the model simulations exhibited promising results, in vitro and in vivo experiments are warranted to validate the findings of this study in future investigations.

The interdural hematoma: A subtype of convexity subdural/dural hematoma with specific radioanatomical characteristics.

Background: Rare cases of biconvex hematomas splitting the convexity dura mater were reported and denominated interdural hematoma (IDH). Due to their rarity, little is known about their radiological characteristics, and in most cases, their invasive management with craniotomy and dural membrane excision is unnecessary. Case Description: We report here a case of single burr-hole endoscopic evacuation of an IDH and its complete resolution after the 6-month follow-up imaging. The literature review reveals 11 reported cases of IDH. Most of them are male and the mean age is 65 years (range 51-90). Most of the reported IDHs were misdiagnosed as epidural hematoma or meningioma, and therefore, they have been managed invasively through craniotomy with dural excision. Diagnosis of the interdural nature was confirmed macroscopically during surgery in all cases and histology was reported for 6 cases. Image analysis found a double dural beak sign and biconvex shape on coronal planes, subarachnoid space enlargement at the collection extremities, and irregular thick inner wall as common radiological aspects of the IDH. Conclusion: IDH is a rarely reported and often misdiagnosed dural hematoma subtype. Its invasive treatment through craniotomy is likely related to its unknown radiological characteristics. We review and raise awareness about potentially unique radiological anatomy that could avoid unnecessary invasive treatment. Moreover, we report the first case of endoscopically evacuated IDH with long-term follow-up imaging showing complete resolution.

Isolated invasive fungal sphenoid sinusitis-induced extensive bone erosion and severe meningoencephalitis: diagnosis and multidisciplinary management.

Invasive fungal sinusitis (IFS) is more common in immunosuppressed patients but can also occur in immunocompetent hosts. While the non-invasive type of fungal sinusitis has usually a good prognosis, IFS is a potentially lethal condition.We report the case of a woman in her 60s presenting an isolated fungal infection by Aspergillus fumigatus of the right sphenoid sinus, causing extensive bone erosion of its walls and complicated by severe meningoencephalitis. She was healthy without any immunosuppressive conditions. Methods of diagnosis, multidisciplinary management, follow-up and outcomes are documented.Early-stage diagnosis of sphenoid sinus pathologies is often delayed because patients are usually asymptomatic. IFS of the sphenoid is more aggressive than other paranasal sinus and carries significant mortality. Early diagnosis and aggressive and multidisciplinary treatment are crucial to reduce sequels and improve patient's survival.

Intraductal Carcinoma of the Parotid Gland as a Rare Neoplasm: A Case Report and Literature Review.

Background: Intraductal carcinoma is a rare low grade neoplasm of salivary glands with an excellent prognosis. It most frequently occurs in the parotid gland. Ectopic localizations are quite rare. Methods: This case report describes a man in his 60's who was referred to ear, nose and throat outpatient department with 1-month history of painless swelling of the right parotid region. Results: Ultrasound-guided fine-needle aspiration unveiled a cytologic specimen judged as "suspicious for malignancy" and patient underwent a partial superficial parotidectomy. Immunohistochemistry confirmed diagnosis of intraductal carcinoma of right parotid gland. Conclusions: There are few reported cases concerning this clinical entity following thorough review of the literature and recent developments with reference to the contribution of cytology and histopathology will probably modify its classification and management.

The Use of Intracranial Vessel Wall Imaging in Clinical Practice.

Three-dimensional vessel wall MR imaging has gained popularity in the diagnosis and management of patients with cerebrovascular disease in clinical practice. Vessel wall MR imaging is an imaging technique that delivers a fundamentally different viewpoint by emphasizing on the pathology of the vessel wall as opposed to traditional descriptions that focus on the vessel lumen. It shows a crucial power in detecting vessel wall changes in patients with diseases including, but not limited to, central nervous system vasculitis, moyamoya disease, aneurysms, dissections, and intracranial atherosclerotic disease.

Late metachronous cerebral metastasis of pancreatic adenocarcinoma of the tail of the pancreas: a case report.

BACKGROUND: Pancreatic cancer is one of the leading causes of cancer mortality and one of the most lethal malignant neoplasms worldwide. It is known for its local tumor extension to the liver; other common sites include the lung, distant lymph nodes, and bone. Brain metastases are extremely rare and represent less than 0.6% of all brain metastases. CASE REPORT: We report the case of a 66-year-old Caucasian female known to have adenocarcinoma of the tail of the pancreas treated with chemotherapy. During follow-up, thoracoabdominal computed tomography scans did not reveal any residual tumor or any metastasis. Moreover, tumor markers were within normal limits. She presented to the emergency department of our institution following an episode of a generalized tonic-clonic seizure 5 years following the initial diagnosis. Brain magnetic resonance imaging revealed an expansive left frontal intraaxial lesion compatible with high-grade glioma. The patient underwent surgical treatment. Histological examination revealed pancreatic metastasis. CONCLUSIONS: Thought to be rare, metachronous cerebral pancreatic metastasis should be kept in mind in patients with pancreatic cancer. Early diagnosis and complete surgical resection play a key role in the survival of these patients.

Spinal fistulas documented by contrast enhanced computed tomography during myelopathy workup: a lost opportunity.

PURPOSE: Low-flow spinal arteriovenous fistulas (SAVFs) with intradural venous drainage typically manifest with a progressive venous hypertensive myelopathy (VHM) in older patients. VHM is difficult to identify. MRI is often nonspecific, and many cases are initially misdiagnosed, most often as transverse myelitis. The workup of myelopathic patients frequently includes thoracic and/or abdominal contrast-enhanced CT (CECT) that are generally not reviewed by neuroradiologists. The purpose of this work was to investigate how often abnormal enhancing intracanalar structures corresponding to the draining veins of a low-flow SAVF were documented by CECT. MATERIALS AND METHODS: We evaluated 92 consecutive patients with low-flow SAVFs and VHM treated at our institution between 2009 and 2018. The study group included 22 of these patients with at least one thoracoabdominal CECT available for review. The control group consisted of 20 consecutive myelopathy patients with negative angiography and at least one thoracoabdominal CECT. Intracanalar enhancing structures were classified either as (i) conspicuous or (ii) equivocal or absent. RESULTS: One CECT in the study group was technically inadequate. Conspicuous intracanalar enhancing structures were observed in 20 of the remaining 21 patients with SAVFs (95.2%) and in 2 of 20 control patients (10%). None of the enhancing intracanalar structures was mentioned in official study reports. CONCLUSIONS: The presence of enhancing vascular structures within the spinal canal on thoracoabdominal CECT obtained during the workup of myelopathies appears to represent a powerful but currently underappreciated tool for the detection of low-flow SAVFs.

Cervical spinal dural fistulas leading to remote thoracolumbar myelopathy: A diagnostic pitfall.

PURPOSE OF REVIEW: Spinal dural arteriovenous fistulas (SDAVFs) are abnormal connections between 1 or more radiculomeningeal arteries and a single radiculomedullary vein draining into the perimedullary venous system. SDAVFs present in older patients with a progressive myelopathy caused by diffuse spinal venous hypertension. The discrepancy between the focal nature of the arteriovenous shunt and the extent of the induced myelopathy is a classic feature of SDAVFs related to the coexistence of diffuse spinal venous drainage impairment. RECENT FINDINGS: We describe 3 cases of cervical SDAVFs (at C1, C4, and C7) presenting with a myelopathy that spared the cervical spinal cord and, in 2 instances, the upper thoracic cord. This is to our knowledge the first observations of cervical SDAVFs with MRI showing absent or subtle flow voids and presenting remote thoracolumbar myelopathy without cervical cord involvement. SUMMARY: A considerable distance may separate low-flow spinal arteriovenous fistulas from the spinal cord damage they produce. These observations emphasize the importance of performing a complete spinal angiogram when investigating a vascular myelopathy of any location and extent.

Clinical characteristics, misdiagnosis and outcomes of patients with low-flow spinal arteriovenous fistulas.

OBJECTIVE: To describe the clinical characteristics, delay to diagnosis and post-intervention outcomes of patients with low-flow spinal arteriovenous fistulas (SAVFs). METHODS: In this retrospective observational study, we reviewed all patients with low-flow SAVFs angiographically diagnosed at our institution between 2008 and 2018. Pre- and post-intervention disability levels were recorded using the modified Aminoff and Logue scale (mALS). RESULTS: One-hundred and five patients were included. Median age was 62 years and 79% were male. Most patients (56%) presented to neurologists and 41% were misdiagnosed with myelitis. Patients underwent unnecessary treatment with corticosteroids (44%), other immunosuppressive therapies (8%) and spinal surgery (10%). Inappropriate corticosteroid treatment led to a precipitous clinical decline in 30% of patients exposed. Only 21% percent of patients were correctly diagnosed after initial evaluation; the median delay to diagnosis in the rest of the cohort was of 12 months (IQR 7 to 24 months). Longer delays to diagnosis were associated with higher levels of disability (p = .002). Treatment of SAVF was endovascular in 64% and surgical in 26%; 13% of patients required further intervention due to incomplete initial treatment or fistula recurrence. Greater than 6 months after intervention, disability scores were improved in 52% and stable in 43% of patients. In individual patients, pre- and post-intervention disability scores were strongly correlated (p < .001). CONCLUSIONS: Low-flow SAVFs are associated with substantial disability and are frequently misdiagnosed. Timely diagnosis of SAVF needs to improve, as endovascular or surgical treatment results in stabilization or improvement of disability in the vast majority of patients.

Case of Cowden Syndrome with 15 Spinal Arteriovenous Fistulas.

BACKGROUND: Spinal vascular malformations are rarely multiple: fewer than 50 observations have been documented so far, with a maximum of 4 coexisting lesions per patient, always restricted to a single vertebral region (e.g., cervical or thoracic). CASE DESCRIPTION: We describe the case of a 61-year-old woman with Cowden syndrome with 15 spinal arteriovenous fistulas (AVFs) at the cervical, thoracic, and lumbar levels and an adrenal AVF. She was initially referred for reevaluation of an upper cervical spinal epidural spinal arteriovenous fistula diagnosed 6 years earlier. Her history included breast carcinoma, a malignant salivary gland tumor, and removal of multiple ovarian, thyroid, and gastric hamartomas. Computed tomography and magnetic resonance imaging confirmed the presence of a prominent cervical vascular lesion. Spinal digital subtraction angiography revealed the presence of 15 additional vascular anomalies. CONCLUSIONS: This multiplicity of AVFs appears to result from a combination of various factors including local regional hemodynamic changes, growth factor-mediated alterations involving notably vascular endothelial growth factor pathways, and the prothrombotic state associated with abnormalities in blood vessel structure.

Virtual Rhesus Labyrinth Model Predicts Responses to Electrical Stimulation Delivered by a Vestibular Prosthesis.

To better understand the spread of prosthetic current in the inner ear and to facilitate design of electrode arrays and stimulation protocols for a vestibular implant system intended to restore sensation after loss of vestibular hair cell function, we created a model of the primate labyrinth. Because the geometry of the implanted ear is complex, accurately modeling effects of prosthetic stimuli on vestibular afferent activity required a detailed representation of labyrinthine anatomy. Model geometry was therefore generated from three-dimensional (3D) reconstructions of a normal rhesus temporal bone imaged using micro-MRI and micro-CT. For systematically varied combinations of active and return electrode location, the extracellular potential field during a biphasic current pulse was computed using finite element methods. Potential field values served as inputs to stochastic, nonlinear dynamic models for each of 2415 vestibular afferent axons, each with unique origin on the neuroepithelium and spiking dynamics based on a modified Smith and Goldberg model. We tested the model by comparing predicted and actual 3D vestibulo-ocular reflex (VOR) responses for eye rotation elicited by prosthetic stimuli. The model was individualized for each implanted animal by placing model electrodes in the standard labyrinth geometry based on CT localization of actual implanted electrodes. Eye rotation 3D axes were predicted from relative proportions of model axons excited within each of the three ampullary nerves, and predictions were compared to archival eye movement response data measured in three alert rhesus monkeys using 3D scleral coil oculography. Multiple empirically observed features emerged as properties of the model, including effects of changing active and return electrode position. The model predicts improved prosthesis performance when the reference electrode is in the labyrinth's common crus (CC) rather than outside the temporal bone, especially if the reference electrode is inserted nearly to the junction of the CC with the vestibule. Extension of the model to human anatomy should facilitate optimal design of electrode arrays for clinical application.

Morphological features in juvenile Huntington disease associated with cerebellar atrophy - magnetic resonance imaging morphometric analysis.

BACKGROUND: The imaging features of Huntington disease are well known in adults, unlike in juvenile-onset Huntington disease. OBJECTIVE: To conduct a morphometric magnetic resonance imaging (MRI) analysis in three juvenile Huntington disease patients (ages 2, 4 and 6 years old) to determine whether quantitative cerebral and cerebellar morphological metrics may provide diagnostically interesting patterns of cerebellar and cerebellar atrophy. MATERIALS AND METHODS: We report the cases of three siblings with extremely early presentations of juvenile Huntington disease associated with dramatic expansions of the morbid paternal allele from 43 to more than 100 CAG trinucleotide repeats. Automatic segmentation of MRI images of the cerebrum and cerebellum was performed and volumes of cerebral substructures and cerebellar lobules of juvenile Huntington disease patients were compared to those of 30 normal gender- and age-matched controls. Juvenile Huntington disease segmented volumes were compared to those of age-matched controls by using a z-score. RESULTS: Three cerebral substructures (caudate nucleus, putamen and globus pallidus) demonstrated a reduction in size of more than three standard deviations from the normal mean although it was not salient in one of them at clinical reading and was not diagnosed. The size of cerebellum lobules, cerebellum grey matter and cerebellum cortex was reduced by more than two standard deviations in the three patients. The cerebellar atrophy was predominant in the posterior lobe. CONCLUSION: Our study sheds light on atrophic cerebral and cerebellar structures in juvenile Huntington disease. Automatic segmentations of the cerebellum provide patterns that may be of diagnostic interest in this disease.

Restoring the 3D vestibulo-ocular reflex via electrical stimulation: the Johns Hopkins multichannel vestibular prosthesis project.

Bilateral loss of vestibular sensation causes difficulty maintaining stable vision, posture and gait. An implantable prosthesis that partly restores normal activity on branches of the vestibular nerve should improve quality of life for individuals disabled by this disorder. We have developed a head-mounted multichannel vestibular prosthesis that restores sufficient semicircular canal function to partially recreate a normal 3-dimensional angular vestibulo-ocular reflex in animals. Here we describe several parallel lines of investigation directed toward refinement of this approach toward eventual clinical application.