Human cochlear nucleus on 7 tesla diffusion tensor imaging: insights into micro-anatomy and function for auditory brainstem implant surgery

OBJECTIVE: The cochlear nucleus (CN) is the target of the auditory brainstem implant (ABI). Most ABI candidates have Neurofibromatosis Type 2 (NF2) and distorted brainstem anatomy from bilateral vestibular schwannomas. The CN is difficult to characterize as routine structural MRI does not resolve detailed anatomy. We hypothesize that diffusion tensor imaging (DTI) enables both in vivo localization and quantitative measurements of CN morphology. STUDY DESIGN: We analyzed 7 Tesla (T) DTI images of 100 subjects (200 CN) and relevant anatomic structures using an MRI brainstem atlas with submillimetric (50 μm) resolution. SETTING: Tertiary referral center. PATIENTS: Young healthy normal hearing adults. INTERVENTION: Diagnostic. MAIN OUTCOME MEASURES: Diffusion scalar measures such as fractional anisotropy (FA), mean diffusivity (MD), mode of anisotropy (Mode), principal eigenvectors of the CN, and the adjacent inferior cerebellar peduncle (ICP). RESULTS: The CN had a lamellar structure and ventral-dorsal fiber orientation and could be localized lateral to the inferior cerebellar peduncle (ICP). This fiber orientation was orthogonal to tracts of the adjacent ICP where the fibers run mainly caudal-rostrally. The CN had lower FA compared to the medial aspect of the ICP (0.44 ± 0.09 vs. 0.64 ± 0.08, p < 0.001). CONCLUSIONS: 7T DTI enables characterization of human CN morphology and neuronal substructure. An ABI array insertion vector directed more caudally would better correspond to the main fiber axis of CN. State-of-the-art DTI has implications for ABI preoperative planning and future image guidance-assisted placement of the electrode array

Morbidity and Volumetric Progression in Juvenile Nasopharyngeal Angiofibroma in a Long-Term Follow-Up

Objective  We compare the open and transnasal approaches for the excision of juvenile nasopharyngeal angiofibromas regarding the rate of morbidity, and residual tumor and its symptomatic recurrence over time. In addition, we present volumetric measurements of juvenile nasopharyngeal angiofibromas over time. Methods  All surgically treated patients of our institution were reviewed back to 1969 for type of surgery, residual tumor by magnetic resonance imaging (MRI)-based volumetry, recurrence, and morbidity. We performed a prospective clinical and radiological follow-up on reachable patients. Results  In total, 40 patients were retrievable from our records. We were able to follow up on 13 patients after a mean of 15.7 years since surgery (range: 1-47 years). Patients operated by the open approach had a higher rate of postoperative complications and thus a higher morbidity than endoscopic patients (4/4 vs 3/9; p  = 0.007), although tumor sizes were equal among groups ( p  = 0.12). Persisting tumor was noted in 3/4 and 4/9 ( p  = 0.56) patients, respectively. The corresponding mean volumes of residual tumors were 16.2 ± 14.4 cm 3 and 10.8 ± 6.6 cm 3 ( p  = 0.27). No progression could be noted in endoscopically treated patients ( p  = 0.24, mean time between scans 2 years). Conclusions  Our analysis shows that the endoscopic approach results in less morbidity. The open approach does not guarantee freedom from persisting tumor tissue. Age seems to be a most important risk factor for the conversion of an asymptomatic persistence into a symptomatic recurrence

Closure of nasal septal perforations with a polydioxanone plate and temporoparietal fascia in a closed approach

BACKGROUND: Septal perforation closure is still often invasive and complex, with relatively low closure rates. OBJECTIVES: We aimed to provide the first results of a case series of 20 patients with nasal septal perforations who underwent septal perforation repair by both an open and a minimally invasive technique by using a graft that consisted of temporoparietal fascia and a polydioxanone (PDS) plate without mucosal flaps. Between 2014 and 2016, we tested, for the first time, the feasibility of the insertion of this graft via a hemitransfixion incision at our institution. The rationale for the closed approach was to avoid any visible nasal scars. We reported our results of both approaches. METHODS: The septal perforations were closed by insertion of a graft, which consisted of a 0.25-mm PDS flexible plate enveloped by temporoparietal fascia, into the perforation. The insertion of the graft was performed either via a columellar incision (open approach) or via a cosmetically advantageous hemitransfixion incision (closed approach) in an underlay technique. No attempts were made to close the perforation by mucosal flap rotation and/or advancement. Protective silastic sheeting to both sides of the perforation provided fixation to the graft while natural mucosal healing occurred over the perforation in the course of 3 to 8 weeks. RESULTS: Eighteen of 20 perforations were closed by mucosa at the last follow-up. The mean follow-up was 8.7 months. Thirteen patients had surgery via the closed approach. CONCLUSION: We showed, for the first time, that the insertion of a graft that consisted of a PDS flexible plate enveloped in temporoparietal fascia via a hemitransfixion incision was feasible and resulted in complete mucosal closure of nasal septal perforations in most patients. By performing the hemitransfixion incision, we avoided any visible nasal scars

Terson syndrome in aneurysmal subarachnoid hemorrhage-its relation to intracranial pressure, admission factors, and clinical outcome

A large number of reports have not been able to clarify the pathophysiology of Terson syndrome (TS) in aneurysmal subarachnoid hemorrhage (aSAH)

Sexual Dysfunction After Good-Grade Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE: To assess the consequences of aneurysmal subarachnoid hemorrhage (aSAH) on sexual pleasure in patients with an otherwise favorable neurologic outcome. METHODS: Anonymous, standardized questionnaires concerning sexual function, including the International Index of Erectile Function (IIEF), Female Sexual Function Index (FSFI), and a statement on subjective change in sexual pleasure after aSAH, were completed by 33 patients treated at the Cantonal Hospital St Gallen between 2005 and 2013. All had favorable neurologic outcomes (Glasgow Outcome Scale score 4 or 5). RESULTS: Ten patients (31.3%) reported a subjective worsening of sexual pleasure after aSAH. Sexual dysfunction according to FSFI criteria affected 9 of the 19 female patients (47.4%). All 19 women had a hypoactive sexual desire disorder. Erectile dysfunction was present in 7 of the 14 male patients (50%). Patients with World Federation of Neurosurgical Societies (WFNS) grade 2 aSAH were significantly more likely to report a subjective worsening of sexual experience after hemorrhage than those with WFNS grade 1. CONCLUSIONS: This is the first known evaluation of sexual health following aSAH with otherwise favorable neurological outcomes, and confirms that sexual dysfunction is common in this population. Sexual health should be explored during follow-up with these patient

Neurodegenerative cerebrospinal fluid biomarkers tau and amyloid beta predict functional, quality of life, and neuropsychological outcomes after aneurysmal subarachnoid hemorrhage

Cerebrospinal fluid (CSF) biomarkers might be useful in predicting outcome after aneurysmal subarachnoid hemorrhage (aSAH). It was the aim to determine whether tau and amyloid beta CSF concentrations predict functional, health-related quality of life (hrQoL), and neuropsychological outcomes after aSAH. Ventricular CSF was obtained from n = 24 aSAH patients at admission (D0), day 2 (D2), and day 6 (D6). CSF total (t)Tau, phosphorylated (p)Tau(181P), and amyloid beta(1-40 and 1-42) (Aβ40/Aβ42) levels were compared between patients with favorable and unfavorable functional (modified Rankin Scale (mRS)), hrQoL (Euro-Qol (EQ-5D)), and neuropsychological outcomes at 3 (3 m) and 12 months (12 m). Patients with unfavorable functional (mRS 4-6) and hrQoL outcome (EQ-5D z-score ≤ - 1.0) at 3 and 12 m had higher CSF tTau/pTau and lower Aβ40/Aβ42 at D0, D2, and D6 with varying degrees of statistical significance. In terms of predicting neuropsychological outcome, CSF pTau showed a statistically significant correlation with the z-scores of executive function (r = - 0.7486, p = 0.008), verbal memory (r = - 0.8101, p = 0.002), attention (r = - 0.6498, p = 0.030), and visuospatial functioning (r = - 0.6944, p = 0.017) at 3 m. At 12 m, CSF pTau had statistically significant correlations with the z-scores of verbal memory (r = - 0.7473, p = 0.008) and visuospatial functioning (r = - 0.6678, p = 0.024). In conclusion, higher tTau/pTau and lower Aβ40/Aβ42 CSF levels predict unfavorable long-term functional and hrQoL outcomes. Neuropsychological deficits correlate with increased CSF tTau and pTau concentrations

Creation of a novel trigeminal tractography atlas for automated trigeminal nerve identification

Diffusion MRI (dMRI) tractography has been successfully used to study the trigeminal nerves (TGNs) in many clinical and research applications. Currently, identification of the TGN in tractography data requires expert nerve selection using manually drawn regions of interest (ROIs), which is prone to inter-observer variability, time-consuming and carries high clinical and labor costs. To overcome these issues, we propose to create a novel anatomically curated TGN tractography atlas that enables automated identification of the TGN from dMRI tractography. In this paper, we first illustrate the creation of a trigeminal tractography atlas. Leveraging a well-established computational pipeline and expert neuroanatomical knowledge, we generate a data-driven TGN fiber clustering atlas using tractography data from 50 subjects from the Human Connectome Project. Then, we demonstrate the application of the proposed atlas for automated TGN identification in new subjects, without relying on expert ROI placement. Quantitative and visual experiments are performed with comparison to expert TGN identification using dMRI data from two different acquisition sites. We show highly comparable results between the automatically and manually identified TGNs in terms of spatial overlap and visualization, while our proposed method has several advantages. First, our method performs automated TGN identification, and thus it provides an efficient tool to reduce expert labor costs and inter-operator bias relative to expert manual selection. Second, our method is robust to potential imaging artifacts and/or noise that can prevent successful manual ROI placement for TGN selection and hence yields a higher successful TGN identification rate

Anatomical assessment of trigeminal nerve tractography using diffusion MRI: A comparison of acquisition b-values and single- and multi-fiber tracking strategies

Background: The trigeminal nerve (TGN) is the largest cranial nerve and can be involved in multiple inflammatory, compressive, ischemic or other pathologies. Currently, imaging-based approaches to identify the TGN mostly rely on T2-weighted magnetic resonance imaging (MRI), which provides localization of the cisternal portion of the TGN where the contrast between nerve and cerebrospinal fluid (CSF) is high enough to allow differentiation. The course of the TGN within the brainstem as well as anterior to the cisternal portion, however, is more difficult to display on traditional imaging sequences. An advanced imaging technique, diffusion MRI (dMRI), enables tracking of the trajectory of TGN fibers and has the potential to visualize anatomical regions of the TGN not seen on T2-weighted imaging. This may allow a more comprehensive assessment of the nerve in the context of pathology. To date, most work in TGN tracking has used clinical dMRI acquisitions with a b-value of 1000 s/mm2 and conventional diffusion tensor MRI (DTI) tractography methods. Though higher b-value acquisitions and multi-tensor tractography methods are known to be beneficial for tracking brain white matter fiber tracts, there have been no studies conducted to evaluate the performance of these advanced approaches on nerve tracking of the TGN, in particular on tracking different anatomical regions of the TGN. Objective: We compare TGN tracking performance using dMRI data with different b-values, in combination with both single- and multi-tensor tractography methods. Our goal is to assess the advantages and limitations of these different strategies for identifying the anatomical regions of the TGN. Methods: We proposed seven anatomical rating criteria including true and false positive structures, and we performed an expert rating study of over 1000 TGN visualizations, as follows. We tracked the TGN using high-quality dMRI data from 100 healthy adult subjects from the Human Connectome Project (HCP). TGN tracking performance was compared across dMRI acquisitions with b = 1000 s/mm2, b = 2000 s/mm2 and b = 3000 s/mm2, using single-tensor (1T) and two-tensor (2T) unscented Kalman filter (UKF) tractography. This resulted in a total of six tracking strategies. The TGN was identified using an anatomical region-of-interest (ROI) selection approach. First, in a subset of the dataset we identified ROIs that provided good TGN tracking performance across all tracking strategies. Using these ROIs, the TGN was then tracked in all subjects using the six tracking strategies. An expert rater (GX) visually assessed and scored each TGN based on seven anatomical judgment criteria. These criteria included the presence of multiple expected anatomical segments of the TGN (true positive structures), specifically branch-like structures, cisternal portion, mesencephalic trigeminal tract, and spinal cord tract of the TGN. False positive criteria included the presence of any fibers entering the temporal lobe, the inferior cerebellar peduncle, or the middle cerebellar peduncle. Expert rating scores were analyzed to compare TGN tracking performance across the six tracking strategies. Intra- and inter-rater validation was performed to assess the reliability of the expert TGN rating result

Utility of Postoperative Magnetic Resonance Imaging in Patients Who Fail Superior Canal Dehiscence Surgery

OBJECTIVE: The etiology of symptoms following primary repair of superior canal dehiscence (SCD) may be due to a persistent third window. However, the extent of surgery cannot be seen on postoperative computed tomography (CT) since most repair materials are not radiopaque. We hypothesize that the extent of superior semicircular canal (SSC) occlusion following primary repair can be quantified based on postoperative magnetic resonance imaging (MRI) data. STUDY DESIGN: Retrospective series. SETTING: Tertiary care center. PATIENTS: Adult patients with a history of SCD syndrome who 1) report persistent symptoms following primary SCD repair and 2) underwent heavily T2-weighted MRI postoperatively. INTERVENTIONS: Analysis of SSC using 3D-reconstruction of CT co-registered with MRI data. MAIN OUTCOME MEASURES: Arc length of fluid void on MRI and quantification of persistent SCD based on CT/MRI co-registration. RESULTS: We identified 9 revision cases from a cohort of 145 SCD repairs at our institution (2002-2017) with CT/MRI data. A fluid void on postoperative MRI (indicating occlusion of the SSC) was observed in all cases (anterior limb: 50.1 degrees [±21.8 SD] and posterior limb 48.1 degrees [±28.5 SD]). Co-registration of CT/MRI revealed a residual defect that was most commonly found along the posterior limb in most patients with persistent symptoms. CONCLUSIONS: The extent of SCD repair can be determined using reformatted or direct T2-weighted MRI sequences in the plane of Pöschl. Co-registration of CT/MRI may be useful to determine the location of a residual superior canal defect and when present was found most commonly along the posterior limb