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.

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.

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.

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.

Vestibular Implant Imaging

Analogous to hearing restoration via cochlear implants, vestibular function could be restored via vestibular implants that electrically stimulate vestibular nerve branches to encode head motion. This study presents the technical feasibility and first imaging results of CT for vestibular implants in 8 participants of the first-in-human Multichannel Vestibular Implant Early Feasibility Study. Imaging characteristics of 8 participants (3 men, 5 women; median age, 59.5 years; range, 51-66 years) implanted with a Multichannel Vestibular Implant System who underwent a postimplantation multislice CT (n = 2) or flat panel CT (n = 6) are reported. The device comprises 9 platinum electrodes inserted into the ampullae of the 3 semicircular canals and 1 reference electrode inserted in the common crus. Electrode insertion site, positions, length and angle of insertion, and number of artifacts were assessed. Individual electrode contacts were barely discernible in the 2 participants imaged using multislice CT. Electrode and osseous structures were detectable but blurred so that only 12 of the 18 stimulating electrode contacts could be individually identified. Flat panel CT could identify all 10 electrode contacts in all 6 participants. The median reference electrode insertion depth angle was 9° (range, -57.5° to 45°), and the median reference electrode insertion length was 42 mm (range, -21-66 mm). Flat panel CT of vestibular implants produces higher-resolution images with fewer artifacts than multidetector row CT, allowing visualization of individual electrode contacts and quantification of their locations relative to vestibular semicircular canals and ampullae. As multichannel vestibular implant imaging improves, so will our understanding of the relationship between electrode placement and vestibular performance.

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.

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.

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.

The Occipital Emissary Vein: A Possible Marker for Pseudotumor Cerebri

BACKGROUND AND PURPOSE

Transverse sinus stenosis can lead to pseudotumor cerebri syndrome by elevating the cerebral venous pressure. The occipital emissary vein is an inconstant emissary vein that connects the torcular herophili with the suboccipital veins of the external vertebral plexus. This retrospective study compares the prevalence and size of the occipital emissary vein in patients with pseudotumor cerebri syndrome with those in healthy control subjects to determine whether the occipital emissary vein could represent a marker of pseudotumor cerebri syndrome.

MATERIALS AND METHODS

The cranial venous system of 46 adult patients with pseudotumor cerebri syndrome (group 1) was studied on CT venography images and compared with a group of 92 consecutive adult patients without pseudotumor cerebri syndrome who underwent venous assessment with gadolinium-enhanced 3D-T1 MPRAGE sequences (group 2). The presence of an occipital emissary vein was assessed, and its proximal (intraosseous) and distal (extracranial) maximum diameters were measured and compared between the 2 groups. Seventeen patients who underwent transverse sinus stent placement had their occipital emissary vein diameters measured before and after stent placement.

RESULTS

Thirty of 46 (65%) patients in group 1 versus 29/92 (31.5%) patients in group 2 had an occipital emissary vein (P < .001). The average proximal and distal occipital emissary vein maximum diameters were significantly larger in group 1 (2.3 versus 1.6 mm, P <.005 and 3.3 versus 2.3 mm, P < .001). The average maximum diameters of the occipital emissary vein for patients who underwent transverse sinus stent placement were larger before stent placement than after stent placement: 2.6 versus 1.8 mm proximally (P < .06) and 3.7 versus 2.6 mm distally (P < .005).

CONCLUSIONS

Occipital emissary veins are more frequent and larger in patients with pseudotumor cerebri syndrome than in healthy subjects, a finding consistent with their role as collateral venous pathway in transverse sinus stenosis. A prominent occipital emissary vein is an imaging sign that should raise the suspicion of pseudotumor cerebri syndrome.

Outcomes of endoscopic ultrasound-guided biliary drainage: A systematic review and meta-analysis

Background

Success and event rates of endoscopic ultrasound (EUS)-guided biliary drainage vary with techniques, and results from different studies remain inconsistent.

Objective

We conducted a proportion meta-analysis to evaluate the efficacy and safety of EUS-guided biliary drainage and compare the outcomes of current procedures.

Methods

We searched MEDLINE, Embase, Cochrane and Web of knowledge to identify studies reporting technical success, clinical success and complication rates of EUS-guided biliary drainage techniques to estimate their clinical and technical efficacy and safety.

Results

We identified 17 studies including a total of 686 patients. The overall clinical success and technical success rates were respectively 84% confidence interval (CI) 95% (80-88) and 96% CI 95% (93-98) for hepaticogastrostomy, and respectively 87% CI 95% (82-91) and 95% CI 95 (91-97) for choledochoduodenostomy. Reported adverse event rates were significantly higher (p = 0.01) for hepaticogastrostomy (29% CI 95% (24-34)) compared to choledochoduodenostomy (20% CI 95% (16-25)). Compared with hepaticogastrostomy, the pooled odds ratio for the complication rate of choledochoduodenostomy was 2.01 (1.25; 3.24) (p = 0.0042), suggesting that choledochoduodenostomy might be safer than hepaticogastrostomy.

Conclusion

The available literature suggests choledochoduodenostomy may be a safer approach compared to hepaticogastrostomy. Randomized controlled trials with sufficiently large cohorts are needed to compare techniques and confirm these findings.

Very late heart transplant rejection is associated with microvascular injury, complement deposition and progression to cardiac allograft vasculopathy

In heart transplants, the significance of very late rejection (after 7 years post-transplant, VLR) detected by routine endomyocardial biopsies (EMB) remains uncertain. Here, we assessed the prevalence, histopathological and immunological phenotype, and outcome of VLR in clinically stable patients. Between 1985 and 2009, 10 662 protocol EMB were performed at our institution in 398 consecutive heart transplants recipients. Among the 196 patients with >7-year follow-up, 20 (10.2%) presented subclinical ≥3A/2R-ISHLT rejection. The VLR group was compared to a matched control group of patients without rejection. All biopsies were stained for C4d/C3d/CD68 with sera screened for the presence of donor-specific antibodies (DSAs). In addition to cellular infiltrates with myocyte damage, 60% of VLR patients had evidence of intravascular macrophages. C4d and/or C3d-capillary deposition was found in 55% VLR EMB. All cases of VLR associated with microcirculation injury had DSAs (mean DSA(max) -MFI = 1751 ± 583). This entity was absent from the control group (p < 0.0001). Finally, after a similar follow-up postreference EMB of 6.4 ± 1 years, the mean of CAV grade was 0.76 ± 0.18 in the control group compared to 2.06 ± 0.26 in the VLR group respectively, p = 0.001). There was no difference in patient survival between study and control groups. In conclusion, VLR is frequently associated with complement-cascade activation, microvascular injury and DSA, suggesting an antibody-mediated process. VLR is associated with a dramatic progression to severe CAV in long-term follow-up.

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.