Cannabis smoke suppresses antiviral immune responses to influenza A in mice

Rationale

Despite its increasingly widespread use, little is known about the impact of cannabis smoking on the response to viral infections like influenza A virus (IAV). Many assume that cannabis smoking will disrupt antiviral responses in a manner similar to cigarette smoking; however, since cannabinoids exhibit anti-inflammatory effects, cannabis smoke exposure may impact viral infection in distinct ways.

Methods

Male and female BALB/c mice were exposed daily to cannabis smoke and concurrently intranasally instilled with IAV. Viral burden, inflammatory mediator levels (multiplex ELISA), lung immune cells populations (flow cytometry) and gene expression patterns (RNA sequencing) were assessed in the lungs. Plasma IAV-specific antibodies were measured via ELISA.

Results

We found that cannabis smoke exposure increased pulmonary viral burden while decreasing total leukocytes, including macrophages, monocytes and dendritic cell populations in the lungs. Furthermore, infection-induced upregulation of certain inflammatory mediators (interferon-γ and C-C motif chemokine ligand 5) was blunted by cannabis smoke exposure, which in females was linked to the transcriptional downregulation of pathways involved in innate and adaptive immune responses. Finally, plasma levels of IAV-specific IgM and IgG1 were significantly decreased in cannabis smoke-exposed, infected mice compared to infected controls, only in female mice.

Conclusions

Overall, cannabis smoke exposure disrupted host-defence processes, leading to increased viral burden and dampened inflammatory signalling. These results suggest that cannabis smoking is detrimental to the maintenance of pulmonary homeostasis during viral infection and highlight the need for data regarding the impact on immune competency in humans.

Myeloid-specific deletion of activating transcription factor 6 alpha increases CD11b+ macrophage subpopulations and aggravates lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrotic interstitial lung disease of unknown etiology. The accumulation of macrophages is associated with disease pathogenesis. The unfolded protein response (UPR) has been linked to macrophage activation in pulmonary fibrosis. To date, the impact of activating transcription factor 6 alpha (ATF6α), one of the UPR mediators, on the composition and function of pulmonary macrophage subpopulations during lung injury and fibrogenesis is not fully understood. We began by examining the expression of Atf6α in IPF patients' lung single-cell RNA sequencing dataset, archived surgical lung specimens, and CD14⁺ circulating monocytes. To assess the impact of ATF6α on pulmonary macrophage composition and pro-fibrotic function during tissue remodelling, we conducted an in vivo myeloid-specific deletion of Atf6α. Flow cytometric assessments of pulmonary macrophages were carried out in C57BL/6 and myeloid specific ATF6α-deficient mice in the context of bleomycin-induced lung injury. Our results demonstrated that Atf6α mRNA was expressed in pro-fibrotic macrophages found in IPF patient lung and in CD14⁺ circulating monocytes obtained from IPF patient blood. After bleomycin administration, the myeloid-specific deletion of Atf6α altered pulmonary macrophage composition, expanding CD11b⁺ subpopulations with dual polarized CD38⁺ CD206⁺ expressing macrophages. Compositional changes were associated with an aggravation of fibrogenesis including increased myofibroblast and collagen deposition. Further mechanistic ex vivo investigation revealed that ATF6α was required for CHOP induction and the death of bone marrow-derived macrophages. Overall, our findings suggest a detrimental role for the ATF6α-deficient CD11b⁺ macrophages which had altered function during lung injury and fibrosis.

Cigarette smoke augments CSF3 expression in neutrophils to compromise alveolar-capillary barrier function during influenza infection

BACKGROUND

Cigarette smokers are at increased risk of acquiring influenza, developing severe disease and requiring hospitalisation/intensive care unit admission following infection. However, immune mechanisms underlying this predisposition are incompletely understood, and therapeutic strategies for influenza are limited.

METHODS

We used a mouse model of concurrent cigarette smoke exposure and H1N1 influenza infection, colony-stimulating factor (CSF)3 supplementation/receptor (CSF3R) blockade and single-cell RNA sequencing (scRNAseq) to investigate this relationship.

RESULTS

Cigarette smoke exposure exacerbated features of viral pneumonia such as oedema, hypoxaemia and pulmonary neutrophilia. Smoke-exposed infected mice demonstrated an increase in viral (v)RNA, but not replication-competent viral particles, relative to infection-only controls. Interstitial rather than airspace neutrophilia positively predicted morbidity in smoke-exposed infected mice. Screening of pulmonary cytokines using a novel dysregulation score identified an exacerbated expression of CSF3 and interleukin-6 in the context of smoke exposure and influenza. Recombinant (r)CSF3 supplementation during influenza aggravated morbidity, hypothermia and oedema, while anti-CSF3R treatment of smoke-exposed infected mice improved alveolar-capillary barrier function. scRNAseq delineated a shift in the distribution of Csf3 + cells towards neutrophils in the context of cigarette smoke and influenza. However, although smoke-exposed lungs were enriched for infected, highly activated neutrophils, gene signatures of these cells largely reflected an exacerbated form of typical influenza with select unique regulatory features.

CONCLUSION

This work provides novel insight into the mechanisms by which cigarette smoke exacerbates influenza infection, unveiling potential therapeutic targets (e.g. excess vRNA accumulation, oedematous CSF3R signalling) for use in this context, and potential limitations for clinical rCSF3 therapy during viral infectious disease.

Early Th2 inflammation in the upper respiratory mucosa as a predictor of severe COVID-19 and modulation by early treatment with inhaled corticosteroids: a mechanistic analysis

BACKGROUND

Community-based clinical trials of the inhaled corticosteroid budesonide in early COVID-19 have shown improved patient outcomes. We aimed to understand the inflammatory mechanism of budesonide in the treatment of early COVID-19.

METHODS

The STOIC trial was a randomised, open label, parallel group, phase 2 clinical intervention trial where patients were randomly assigned (1:1) to receive usual care (as needed antipyretics were only available treatment) or inhaled budesonide at a dose of 800 μg twice a day plus usual care. For this experimental analysis, we investigated the nasal mucosal inflammatory response in patients recruited to the STOIC trial and in a cohort of SARS-CoV-2-negative healthy controls, recruited from a long-term observational data collection study at the University of Oxford. In patients with SARS-CoV-2 who entered the STOIC study, nasal epithelial lining fluid was sampled at day of randomisation (day 0) and at day 14 following randomisation, blood samples were also collected at day 28 after randomisation. Nasal epithelial lining fluid and blood samples were collected from the SARS-CoV-2 negative control cohort. Inflammatory mediators in the nasal epithelial lining fluid and blood were assessed for a range of viral response proteins, and innate and adaptive response markers using Meso Scale Discovery enzyme linked immunoassay panels. These samples were used to investigate the evolution of inflammation in the early COVID-19 disease course and assess the effect of budesonide on inflammation.

FINDINGS

146 participants were recruited in the STOIC trial (n=73 in the usual care group; n=73 in the budesonide group). 140 nasal mucosal samples were available at day 0 (randomisation) and 122 samples at day 14. At day 28, whole blood was collected from 123 participants (62 in the budesonide group and 61 in the usual care group). 20 blood or nasal samples were collected from healthy controls. In early COVID-19 disease, there was an enhanced inflammatory airway response with the induction of an anti-viral and T-helper 1 and 2 (Th1/2) inflammatory response compared with healthy individuals. Individuals with COVID-19 who clinically deteriorated (ie, who met the primary outcome) showed an early blunted respiratory interferon response and pronounced and persistent Th2 inflammation, mediated by CC chemokine ligand (CCL)-24, compared with those with COVID-19 who did not clinically deteriorate. Over time, the natural course of COVID-19 showed persistently high respiratory interferon concentrations and elevated concentrations of the eosinophil chemokine, CCL-11, despite clinical symptom improvement. There was persistent systemic inflammation after 28 days following COVID-19, including elevated concentrations of interleukin (IL)-6, tumour necrosis factor-α, and CCL-11. Budesonide treatment modulated inflammation in the nose and blood and was shown to decrease IL-33 and increase CCL17. The STOIC trial was registered with ClinicalTrials.gov, NCT04416399.

INTERPRETATION

An initial blunted interferon response and heightened T-helper 2 inflammatory response in the respiratory tract following SARS-CoV-2 infection could be a biomarker for predicting the development of severe COVID-19 disease. The clinical benefit of inhaled budesonide in early COVID-19 is likely to be as a consequence of its inflammatory modulatory effect, suggesting efficacy by reducing epithelial damage and an improved T-cell response.

FUNDING

Oxford National Institute of Health Research Biomedical Research Centre and AstraZeneca.

Increased Monocyte-Derived CD11b+ Macrophage Subpopulations Following Cigarette Smoke Exposure Are Associated With Impaired Bleomycin-Induced Tissue Remodelling

Rationale

The accumulation of macrophages in the airways and the pulmonary interstitium is a hallmark of cigarette smoke-associated inflammation. Notably, pulmonary macrophages are not a homogenous population but consist of several subpopulations. To date, the manner in which cigarette smoke exposure affects the relative composition and functional capacity of macrophage subpopulations has not been elucidated.

Methods

Using a whole-body cigarette smoke exposure system, we investigated the impact of cigarette smoke on macrophage subpopulations in C57BL/6 mice using flow cytometry-based approaches. Moreover, we used bromodeoxyuridine labelling plus Il1a^-/- and Il1r1^-/- mice to assess the relative contribution of local proliferation and monocyte recruitment to macrophage accumulation. To assess the functional consequences of altered macrophage subpopulations, we used a model of concurrent bleomycin-induced lung injury and cigarette smoke exposure to examine tissue remodelling processes.

Main Results

Cigarette smoke exposure altered the composition of pulmonary macrophages increasing CD11b⁺ subpopulations including monocyte-derived alveolar macrophages (Mo-AM) as well as interstitial macrophages (IM)1, -2 and -3. The increase in CD11b⁺ subpopulations was observed at multiple cigarette smoke exposure timepoints. Bromodeoxyuridine labelling and studies in Il1a^-/- mice demonstrated that increased Mo-AM and IM3 turnover in the lungs of cigarette smoke-exposed mice was IL-1α dependent. Compositional changes in macrophage subpopulations were associated with impaired induction of fibrogenesis including decreased α-smooth muscle actin positive cells following intratracheal bleomycin treatment. Mechanistically, in vivo and ex vivo assays demonstrated predominant macrophage M1 polarisation and reduced matrix metallopeptidase 9 activity in cigarette smoke-exposed mice.

Conclusion

Cigarette smoke exposure modified the composition of pulmonary macrophage by expanding CD11b⁺ subpopulations. These compositional changes were associated with attenuated fibrogenesis, as well as predominant M1 polarisation and decreased fibrotic activity. Overall, these data suggest that cigarette smoke exposure altered the composition of pulmonary macrophage subpopulations contributing to impaired tissue remodelling.

Cigarette smoke exposure attenuates the induction of antigen-specific IgA in the murine upper respiratory tract

The upper respiratory tract is highly exposed to airborne pathogens and serves as an important inductive site for protective antibody responses, including mucosal IgA and systemic IgG. However, it is currently unknown to what extent inhaled environmental toxins, such as a cigarette smoke, affect the ability to induce antibody-mediated immunity at this site. Using a murine model of intranasal lipopolysaccharide and ovalbumin (LPS/OVA) immunization, we show that cigarette smoke exposure compromises the induction of antigen-specific IgA in the upper airways and systemic circulation. Deficits in OVA-IgA were observed in conjunction with a reduced accumulation of OVA-specific IgA antibody-secreting cells (ASCs) in the nasal mucosa, inductive tissues (NALT, cervical lymph nodes, spleen) and the blood. Nasal OVA-IgA from smoke-exposed mice also demonstrated reduced avidity during the acute post-immunization period in association with an enhanced mutational burden in the cognate nasal Igha repertoire. Mechanistically, smoke exposure attenuated the ability of the nasal mucosa to upregulate VCAM-1 and pIgR, suggesting that cigarette smoke may inhibit both nasal ASC homing and IgA transepithelial transport. Overall, these findings demonstrate the immunosuppressive nature of tobacco smoke and illustrate the diversity of mechanisms through which this noxious stimulus can interfere with IgA-mediated immunity in the upper airways.

Development and validation of a mouse model of contemporary cannabis smoke exposure

Cannabis is widely used for both recreational and medicinal purposes. Inhalation of combusted cannabis smoke is the most common mode of drug consumption, exposing the lungs to the pharmacologically active ingredients, including tetrahydrocannabinol (THC) and cannabidiol (CBD). While the relationship between cannabis smoke exposure and compromised respiratory health has yet to be sufficiently defined, previous investigations suggest that cannabis smoke may dysregulate pulmonary immunity. Presently, there exist few preclinical animal models that have been extensively validated for contemporary cannabis smoke exposure.

 To address this need, we developed a mouse model with readouts of total particulate matter, serum cannabinoid and carboxyhaemoglobin levels, lung cellular responses, and immune-mediator production.

 Using a commercially available smoke exposure system and a cannabis source material of documented THC/CBD composition, we exposed mice to a mean±sd total particulate matter of 698.89±66.09 µg·L⁻¹ and demonstrate increases in serum cannabinoids and carboxyhaemoglobin. We demonstrate that cannabis smoke modulates immune cell populations and mediators in both male and female BALB/c mice. This modulation is highlighted by increases in airway and lung tissue macrophage populations, including tissue-resident alveolar macrophages, monocyte-derived alveolar macrophages, and interstitial macrophage subpopulations. No changes in airway or lung tissue infiltration of neutrophils were observed. Immune-mediator analysis indicated significant upregulation of macrophage-derived chemokine, thymus and activation-regulated chemokine, and vascular endothelial growth factor within the lung tissue of cannabis smoke-exposed mice.

 This accessible and reproducible smoke-exposure model provides a foundation to explore the impact of chronic cannabis exposures and/or co-exposures with pathogens of clinical relevance, such as influenza.

Validation of the use of contemporary cannabis available on the legal market of known THC/CBD composition in a mouse model of smoke exposure with readouts of lung inflammationhttps://bit.ly/3okHWS4

Differential expression of sputum and serum autoantibodies in patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a complex and progressive respiratory disease. Autoimmune processes have been hypothesized to contribute to disease progression; however, the presence of autoantibodies in the serum has been variable. Given that COPD is a lung disease, we sought to investigate whether autoantibodies in sputum supernatant would better define pulmonary autoimmune processes. Matched sputum and serum samples were obtained from the Airways Disease Endotyping for Personalized Therapeutics (ADEPT) study and at the Guangzhou Institute of Respiratory Health (GIRH). Samples were collected from patients with varying severity of COPD, asymptomatic smokers, and healthy control subjects. IgG and IgM autoantibodies were detected in sputum and serum of all subjects in both cohorts using a broad-spectrum autoantigen array. No differences were observed in sputum autoantibodies between COPD and asymptomatic smokers in either cohort. In contrast, 16% of detectable sputum IgG autoantibodies were decreased in subjects with COPD compared to healthy controls in the ADEPT cohort. Compared to asymptomatic smokers, approximately 13% of detectable serum IgG and 40% of detectable serum IgM autoantibodies were differentially expressed in GIRH COPD subjects. Of the differentially expressed specificities, anti-nuclear autoantibodies were predominately decreased. A weak correlation between increased serum IgM anti-tissue autoantibodies and a measure of airspace enlargement was observed. The differential expression of specificities varied between the cohorts. In closing, using a comprehensive autoantibody array, we demonstrate that autoantibodies are present in subjects with COPD, asymptomatic smokers, and healthy controls. Cohorts displayed high levels of heterogeneity, precluding the utilization of autoantibodies for diagnostic purposes.

Meta-analysis of outcome in anterior skull base resection for squamous cell and undifferentiated carcinoma

Multiple reports now demonstrate the technical feasibility of combined intra- and extracranial procedures for the excision of malignancy involving the anterior skull base-Anatomic proximity to vital structures in this region often precludes en bloc resection, however, and margins are often measured in millimeters. Nevertheless, multiple cases of prolonged survival following craniofacial excision of high-grade malignancies have been reported. These are usually included in larger series that encompass tumors of various histologic characteristics and grade. A meta-analysis of the reported outcome of craniofacial resection for squamous cell and undifferentiated carcinoma was performed. Ninety-six articles on craniofacial resection were reviewed and a total of 425 patients who had undergone craniofacial resection were identified in 30 of these. Of 89 patients with squamous cell carcinoma in whom follow-up data were available from seven larger series, the disease-free survival at 2 or greater years was 64%. Forty-one patients with undifferentiated carcinoma were identified who had undergone surgical excision, and 45% were disease-free at 2 or greater years (range, 2 to 24 years). This meta-analysis suggests that high-grade carcinoma involving the anterior cranial base is amenable to surgical excision with acceptable disease-free survival in selected patients at 2 years.

Effects of postural changes and removal of vestibular inputs on blood flow to and from the hindlimb of conscious felines

Considerable data show that the vestibular system contributes to blood pressure regulation. Prior studies reported that lesions that eliminate inputs from the inner ears attenuate the vasoconstriction that ordinarily occurs in the hindlimbs of conscious cats during head-up rotations. These data led to the hypothesis that labyrinthine-deficient animals would experience considerable lower body blood pooling during head-up postural alterations. The present study tested this hypothesis by comparing blood flow though the femoral artery and vein of conscious cats during 20-60 degrees head-up tilts from the prone position before and after removal of vestibular inputs. In vestibular-intact animals, venous return from the hindlimb dropped considerably at the onset of head-up tilts and, at 5 s after the initiation of 60 degrees rotations, was 66% lower than when the animals were prone. However, after the animals were maintained in the head-up position for another 15 s, venous return was just 33% lower than before the tilt commenced. At the same time point, arterial inflow to the limb had decreased 32% from baseline, such that the decrease in blood flow out of the limb due to the force of gravity was precisely matched by a reduction in blood reaching the limb. After vestibular lesions, the decline in femoral artery blood flow that ordinarily occurs during head-up tilts was attenuated, such that more blood flowed into the leg. Contrary to expectations, in most animals, venous return was facilitated, such that no more blood accumulated in the hindlimb than when labyrinthine signals were present. These data show that peripheral blood pooling is unlikely to account for the fluctuations in blood pressure that can occur during postural changes of animals lacking inputs from the inner ear. Instead, alterations in total peripheral resistance following vestibular dysfunction could affect the regulation of blood pressure.

Consequences of postural changes and removal of vestibular inputs on the movement of air in and out of the lungs of conscious felines

A variety of experimental approaches in human subjects and animal models established that the vestibular system contributes to regulation of respiration. In cats, the surgical elimination of labyrinthine signals produced changes in the spontaneous activity and posturally related responses of a number of respiratory muscles. However, these effects were complex and sometimes varied between muscle compartments, such that the physiological role of vestibulo-respiratory responses is unclear. The present study determined the functional significance of vestibulo-respiratory influences by examining the consequences of a bilateral labyrinthectomy on breathing rate and the pressure, volume, and flow rate of air exchanged during inspiration and expiration as body orientation with respect to gravity was altered. Data were collected from conscious adult cats acclimated to breathing through a facemask connected to a pneuomotach during 60 degrees head-up pitch and ear-down roll body rotations. Removal of vestibular inputs resulted in a 15% reduction in breathing rate, a 13% decrease in minute ventilation, a 16% decrease in maximal inspiratory airflow rate, and a 14% decrease in the maximal expiratory airflow rate measured when the animals were in the prone position. However, the lesions did not appreciably affect phasic changes in airflow parameters related to alterations in posture. These results suggest that the role of the vestibular system in the control of breathing is to modify baseline respiratory parameters in proportion to the general intensity of ongoing movements, and not to rapidly alter ventilation in accordance with body position.

Vestibular inputs elicit patterned changes in limb blood flow in conscious cats

Previous experiments have demonstrated that the vestibular system contributes to regulating sympathetic nervous system activity, particularly the discharges of vasoconstrictor fibres. In the present study, we examined the physiological significance of vestibulosympathetic responses by comparing blood flow and vascular resistance in the forelimb and hindlimb during head-up tilt from the prone position before and after the removal of vestibular inputs through a bilateral vestibular neurectomy. Experiments were performed on conscious cats that were trained to remain sedentary on a tilt table during rotations up to 60 deg in amplitude. Blood flow through the femoral and brachial arteries was recorded during whole-body tilt using perivascular probes; blood pressure was recorded using a telemetry system and vascular resistance was calculated from blood pressure and blood flow measurements. In vestibular-intact animals, 60 deg head-up tilt produced approximately 20% decrease in femoral blood flow and approximately 37% increase in femoral vascular resistance relative to baseline levels before tilt; similar effects were also observed for the brachial artery ( approximately 25% decrease in blood flow and approximately 38% increase in resistance). Following the removal of vestibular inputs, brachial blood flow and vascular resistance during head-up tilt were almost unchanged. In contrast, femoral vascular resistance increased only approximately 6% from baseline during 60 deg head-up rotation delivered in the first week after elimination of vestibular signals and approximately 16% in the subsequent 3-week period (as opposed to the approximately 37% increase in resistance that occurred before lesion). These data demonstrate that vestibular inputs associated with postural alterations elicit regionally specific increases in vascular resistance that direct blood flow away from the region of the body where blood pooling may occur. Thus, the data support the hypothesis that vestibular influences on the cardiovascular system serve to protect against the occurrence of orthostatic hypotension.

Effects of postural changes and removal of vestibular inputs on blood flow to the head of conscious felines

Prior studies have shown that removal of vestibular inputs produces lability in blood pressure during orthostatic challenges (Holmes MJ, Cotter LA, Arendt HE, Cass SP, and Yates BJ. Brain Res 938: 62-72, 2002; Jian BJ, Cotter LA, Emanuel BA, Cass SP, and Yates BJ. J Appl Physiol 86: 1552-1560, 1999). Furthermore, these studies led to the prediction that the blood pressure instability results in susceptibility for orthostatic intolerance. The present experiments tested this hypothesis by recording common carotid blood flow (CCBF) in conscious cats during head-up tilts of 20, 40, and 60 degrees amplitudes, before and after the surgical elimination of labyrinthine inputs through a bilateral vestibular neurectomy. Before vestibular lesions in most animals, CCBF remained stable during head-up rotations. Unexpectedly, in five of six animals, the vestibular neurectomy resulted in a significant increase in baseline CCBF, particularly when the laboratory was illuminated; on average, basal blood flow measured when the animals were in the prone position was 41 +/- 17 (SE) % higher after the first week after the lesions. As a result, even when posturally related lability in CCBF occurred after removal of vestibular inputs, blood supply to the head was not lower than when labyrinthine inputs were present. These data suggest that vestibular influences on cardiovascular regulation are more complex than previously appreciated, because labyrinthine signals appear to participate in setting basal rates of blood flow to the head in addition to triggering dynamic changes in the circulation to compensate for orthostatic challenges.

Ossiculoplasty Using Incus Interposition: Hearing Results and Analysis of the Middle Ear Risk Index

OBJECTIVE

To determine the immediate hearing result and the long-term stability of sculpted incus interposition in ossiculoplasty and evaluate the utility of the middle ear risk index in predicting hearing outcome in these cases.

PATIENTS

One hundred thirty-seven surgical patients.

STUDY DESIGN

Review of 137 patients who underwent ossiculoplasty using autologous or homologous sculpted incus interposition.

INTERVENTIONS

Ossiculoplasty using autologous or homologous sculpted incus interposition.

METHODS

Retrospective chart review, using the guidelines delineated by the Committee on Hearing and Equilibrium of the Academy of Otolaryngology-Head and Neck Surgery for the evaluation of results for the treatment of conductive hearing loss.

RESULTS

The mean preoperative air bone gap was 26.8 dB, and the mean postoperative gap was 18.6 dB. Twenty-seven percent of patients were closed to within 10 dB, and 66.4% were brought to within 20 dB of the postoperative bone conduction line. Average time to the last postoperative audiometric testing was 15.8 months, with a range of 2 to 62 months. A mean air bone gap change of -0.2 dB was noted. Four patients had more than a 10 dB deterioration in conductive hearing loss. There were no cases of graft extrusion. Each ear operated upon in our series was fully scored using the middle ear risk index, and an index total was calculated. No statistical associations could be demonstrated in any group between the postoperative air bone gap and the middle ear risk index subcategories or total.

CONCLUSIONS

Sculpted autologous or homologous incus interposition provides hearing success comparable with current allograft prosthesis studies, has a very low extrusion rate, and remains stable over time. We were not able to demonstrate an association between the middle ear risk index and hearing results in this subset of patients.

Effects of postural changes and vestibular lesions on genioglossal muscle activity in conscious cats

Previous studies in humans showed that genioglossal muscle activity is higher when individuals are supine than when they are upright, and prior experiments in anesthetized or decerebrate animals suggested that vestibular inputs might participate in triggering these alterations in muscle firing. The present study determined the effects of whole body tilts in the pitch (nose-up) plane on genioglossal activity in a conscious feline model and compared these responses with those generated by roll (ear-down) tilts. We also ascertained the effects of a bilateral vestibular neurectomy on the alterations in genioglossal activity elicited by changes in body position. Both pitch and roll body tilts produced modifications in muscle firing that were dependent on the amplitude of the rotation; however, the relative effects of ear-down and nose-up tilts on genioglossal activity were variable from animal to animal. The response variability observed might reflect the fact that genioglossus has a complex organization and participates in a variety of tongue movements; in each animal, electromyographic recordings presumably sampled the firing of different proportions of fibers in the various compartments and subcompartments of the muscle. Furthermore, removal of labyrinthine inputs resulted in alterations in genioglossal responses to postural changes that persisted until recordings were discontinued approximately 1 mo later, demonstrating that the vestibular system participates in regulating the muscle's activity. Peripheral vestibular lesions were subsequently demonstrated to be complete through the postmortem inspection of temporal bone sections or by observing that vestibular nucleus neurons did not respond to rotations in vertical planes.

Use of electrical vestibular stimulation to alter genioglossal muscle activity in awake cats

Prior work has shown that the vestibular system contributes to regulating activity of upper airway muscles including the tongue protruder muscle genioglossus. The goal of the present experiments was to determine whether electrical vestibular stimulation could potentially be used to alter genioglossal activity in awake animals. Six adult cats were instrumented for recording of EMG activity from genioglossus, abdominal musculature, and triceps. In addition, a silver ball electrode was implanted on the round window for stimulation of vestibular afferents. Subsequently, stimulation and recordings were conducted while animals were awake. In all cases, stimulation using single shocks or trains of pulses > 100 microA in intensity produced responses in all muscles, including genioglossus. The latency of the genioglossal response was approximately 12 msec, and delivering continuous current trains to the labyrinth chronically elevated the muscle's activity. Although a number of muscles were affected by the stimulus, animals experienced no obvious distress or balance disturbances. Vestibular stimulation remained effective in producing genioglossal responses until experiments were discontinued 1-2 months following onset. These data suggest that electrical vestibular stimulation could potentially be used therapeutically to alter upper airway muscle activity.

Effects of lesions of the caudal cerebellar vermis on cardiovascular regulation in awake cats

The vestibular system is known to participate in cardiovascular regulation during movement and postural alterations. The present study considered whether lesions of two regions of the posterior cerebellar vermis (the nodulus and uvula) that provide inputs to vestibular nucleus regions that affect control of blood pressure would alter cardiovascular responses during changes in posture. Blood pressure and heart rate were monitored in awake cats during nose-up tilts up to 60 degrees in amplitude before and following aspiration lesions of the nodulus or uvula; in most animals, cardiovascular responses were also recorded following the subsequent removal of vestibular inputs. Lesions of the nodulus or uvula did not affect baseline blood pressure or heart rate, although cardiovascular responses during nose-up tilts were altered. Increases in heart rate that typically occurred during 60 degrees nose-up tilt were attenuated in all three animals with lesions affecting both dorsal and ventral portions of the uvula; in contrast, the heart rate responses were augmented in the two animals with lesions mainly confined to the nodulus. Furthermore, following subsequent removal of vestibular inputs, uvulectomized animals, but not those with nodulus lesions, experienced more severe orthostatic hypotension than has previously been reported in cerebellum-intact animals with bilateral labyrinthectomies. These data suggest that the cerebellar nodulus and uvula modulate vestibulo-cardiovascular responses, although the two regions play different roles in cardiovascular regulation.

Effects of postural changes and vestibular lesions on diaphragm and rectus abdominis activity in awake cats

Changes in posture can affect the resting length of the diaphragm, requiring alterations in the activity of both the abdominal muscles and the diaphragm to maintain stable ventilation. To determine the role of the vestibular system in regulating respiratory muscle discharges during postural changes, spontaneous diaphragm and rectus abdominis activity and modulation of the firing of these muscles during nose-up and ear-down tilt were compared before and after removal of labyrinthine inputs in awake cats. In vestibular-intact animals, nose-up and ear-down tilts from the prone position altered rectus abdominis firing, whereas the effects of body rotation on diaphragm activity were not statistically significant. After peripheral vestibular lesions, spontaneous diaphragm and rectus abdominis discharges increased significantly (by approximately 170%), and augmentation of rectus abdominis activity during nose-up body rotation was diminished. However, spontaneous muscle activity and responses to tilt began to recover after a few days after the lesions, presumably because of plasticity in the central vestibular system. These data suggest that the vestibular system provides tonic inhibitory influences on rectus abdominis and the diaphragm and in addition contributes to eliciting increases in abdominal muscle activity during some changes in body orientation.

An anatomic variant of the anterior inferior cerebellar artery in a patient with Ménière's disease

OBJECTIVE

To describe an anatomic variant of the anterior inferior cerebellar artery in a patient with Ménière's disease.

STUDY DESIGN

Retrospective case review and review of the literature.

SETTING

Tertiary referral clinic.

INTERVENTION

Vestibular nerve section and microvascular decompression.

MAIN OUTCOME MEASURES

Audiometric testing and control of vertigo.

RESULTS

The eighth nerve was identified via a retromastoid approach. The anterior inferior cerebellar artery was observed bisecting the eighth nerve. The vestibular nerve was sectioned, and microvascular decompression was performed on the cochlear division. At last follow-up, the patient had not experienced any vertiginous attacks but was observed to have progressive hearing loss.

CONCLUSIONS

The course of the anterior inferior cerebellar artery is highly variable and difficult to predict. Knowing the potential paths is a necessity in performing posterior fossa surgery. Although the patient's vertigo was controlled by the vestibular nerve section, microvascular decompression of the cochlear nerve did not result in hearing improvement or stabilization. This case report does not support a benefit of microvascular decompression in Méniére's disease. Vestibular nerve section remains the authors' treatment of choice for controlling disabling vertigo caused by Ménière's disease.

Creating a stable tympanic membrane perforation using mitomycin C

OBJECTIVE

To determine the ability of topically applied mitomycin C to create a stable tympanic membrane perforation.

STUDY DESIGN AND SETTING

Twenty-four rats underwent subtotal removal of the tympanic membranes bilaterally. Forty ears received 0.2 mg/ml of mitomycin C. The remaining 8 received phosphate-buffered saline solution (control). Photographs taken every 3 to 5 days for 44 days were digitally scanned and computer analyzed to calculate the percentage of residual perforation. Application of solutions, photography, and data analysis were performed in a blinded fashion.

RESULTS

The mitomycin C treated ears had delayed closure time and healing rate (from day 0 to 25) compared to the control group. All controls healed by day 14. By day 44, 92.5% of the mitomycin C treated ears healed.

CONCLUSION

Mitomycin C prolongs the closure and healing rate of myringotomies in rat tympanic membranes.

SIGNIFICANCE

Myringotomy with concurrent mitomycin C application may be useful for creating an animal model for chronic tympanic membrane perforation and should be tested in human beings as a method to maintain myringotomy patency for long-term ventilation.

Short- and long-term outcomes of canalith repositioning for benign paroxysmal positional vertigo

This is a prospective, nonrandomized study of the canalith repositioning procedure (CRP) for treatment of benign paroxysmal positional vertigo (BPPV). CRP was used to treat 168 patients with BPPV. Patient data were gathered by yearly telephone interviews to determine whether symptoms of position-induced vertigo had returned. After 1 or 2 treatment sessions 91.3% of patients reported complete symptom resolution. Average follow-up for the study population after the initial treatment was 26 months. A recurrence rate of 26.8% was found among those patients who initially reported resolution of symptoms after CRP. Application of recurrence data to a Kaplan-Meier estimation suggests a 15% recurrence rate per year of BPPV, with a 50% recurrence rate of BPPV at 40 months after treatment. There was no significant association between cure or recurrence rate and sex, age, duration of symptoms, presumed cause, or treating physician.

Responses of vestibular nucleus neurons to tilt following chronic bilateral removal of vestibular inputs

Recordings were made from the vestibular nuclei of decerebrate cats that had undergone a combined bilateral labyrinthectomy and vestibular neurectomy 49-103 days previously and allowed to recover. Responses of neurons were recorded to tilts in multiple vertical planes at frequencies ranging from 0.05 to 1 Hz and amplitudes up to 15 degrees. Many spontaneously active neurons were present in the vestibular nuclei; the mean firing rate of these cells was 43 +/- 5 (SEM) spikes/s. The spontaneous firing of the neurons was irregular: the coefficient of variation was 0.86 +/- 0.14. The firing of 27% of the neurons was modulated by tilt. The plane of tilt that elicited the maximal response was typically within 25 degrees of pitch. The response gain was approximately 1 spikes/s/degree across stimulus frequencies. The response phase was near stimulus position at low frequencies, and lagged position slightly at higher frequencies (average of 35 +/- 9 degrees at 0.5 Hz). The source of the inputs eliciting modulation of vestibular nucleus activity during tilt in animals lacking vestibular inputs is unknown, but could include receptors in the trunk or limbs. These findings show that activation of vestibular nucleus neurons during vertical rotations is not exclusively the result of labyrinthine inputs, and suggest that limb and trunk inputs may play an important role in graviception and modulating vestibular-elicited reflexes.

Benign paroxysmal positional vertigo

Benign paroxysmal positional vertigo is a common disorder of the inner ear that should be suspected in all patients with a history of positionally provoked vertigo. The condition appears to be caused by free-floating debris in the posterior semicircular canal. The diagnosis is confirmed by eliciting characteristic symptoms and signs during the Dix-Hallpike test. Although benign paroxysmal positional vertigo is usually a self-limited disorder, treatment with a specific bedside maneuver is effective and can provide the patient immediate and long-lasting relief. Although many patients with positionally provoked vertigo have typical benign paroxysmal positional vertigo, physicians should be aware of nonbenign variants.

Approach to the vestibular patient and driving: A patient perspective

OBJECTIVES

To learn about the impact of dizziness on driving from a patient perspective and to present an approach to the vestibular patient and driving.

DESIGN

An anonymous questionnaire completed by 265 dizzy patients at 3 different centers.

RESULTS

The participants were experienced drivers who needed to drive to function normally (83%). Those with constant or severe dizziness comprised a higher risk group of drivers. Although few had ever been warned not to drive, 52% said that if they were warned to stop driving, they would not. Most thought that it was the doctor's role to report unsafe drivers to the authorities (P < 0.001, chi2 = 87.2670).

CONCLUSIONS

The diagnosis of a vestibular disorder should not alone be grounds to suspend a patient's driver's license. Legislation should be amended to better reflect the views of doctors and patients alike.

Effects of bilateral vestibular lesions on orthostatic tolerance in awake cats

Previous experiments in anesthetized or decerebrate cats showed that the vestibular system participates in adjusting blood pressure during postural changes. The present experiments tested the hypothesis that removal of vestibular inputs in awake cats would affect orthostatic tolerance. Before the lesion, blood pressure typically remained within 10 mmHg of baseline values during nose-up-pitch body rotations of up to 60 degrees in amplitude. In contrast, bilateral peripheral vestibular lesions altered the pattern of orthostatic responses in all animals, and blood pressure fluctuated >10 mmHg from baseline values during most 60 degrees nose-up tilts in five of six animals. The deficit in correcting blood pressure was particularly large when the animal also was deprived of visual cues indicating position in space. During this testing condition, either a decrease or increase in blood pressure >10 mmHg in magnitude occurred in >80% of tilts. The deficit in adjusting blood pressure after vestibular lesions persisted for only 1 wk, after which time blood pressure remained stable during tilt. These data show that removal of vestibular inputs alters orthostatic responses and are consistent with the hypothesis that vestibular signals are one of several inputs that are integrated to elicit compensatory changes in blood pressure during movement.

Management of facial nerve injury due to temporal bone trauma

OBJECTIVE

This article provides an overview of relevant data regarding the management of facial nerve injury due to temporal bone trauma.

DATA SOURCES

Sources used were relevant English language clinical and basic science publications.

STUDY SELECTION

A Medline search dating back to 1966 for articles concerning temporal bone trauma and facial nerve injury including both human and animal data was performed. Articles were included if they contained relevant data or were significant reviews on the subject. A retrograde bibliography search was then conducted to acquire any articles that may have been missed by the computerized search, including those papers published prior to 1966.

DATA EXTRACTION

The data from each paper were reviewed individually.

DATA SYNTHESIS

The data were not amenable to formal meta-analysis or valid data summarization.

CONCLUSIONS

Patients who should not require surgical intervention include those who have: documented normal facial nerve function after injury regardless of progression, presentation with incomplete facial nerve paralysis with no progression to complete paralysis, and degeneration <95% on ENoG. The remaining patients presumably have a poorer prognosis for return of facial nerve function although it remains unclear exactly how poor the return of function will be. Decompression surgery likely has a beneficial effect if performed within 14 days of injury, so those patients with expected poor natural outcomes may be offered this intervention. Late decompression surgery is not recommended. Late exploratory surgery is recommended only in those patients who do not experience adequate recovery of facial nerve function and likely require nerve repair. Despite the availability of a relatively large volume of published data, there remain many unanswered questions.

Treatment of benign positional vertigo using heels-over-head rotation

Particle repositioning, using either bedside techniques or whole-body manipulation devices, has been used effectively to treat benign positional vertigo (BPV). We assessed the efficacy of particle repositioning using a device designed and built specifically to treat BPV that rotated patients 360 degrees heels-over-head in their sagittal body plane while their heads were turned to align the posterior semicircular canal with the plane of rotation. Eye movements were monitored during the maneuver by an infrared video recording system that allowed subsequent review of the induced nystagmus. Our results indicate that 1) heels-over-head rotation is an extremely efficacious procedure for treating patients with BPV and 2) the pattern of nystagmus during repositioning is consistent with the theory that free-floating debris is highly likely to account for BPV.

A review of balance instruments for older adults

OBJECTIVE

The purpose of this article is to review balance instruments developed within the past 10 years that can be used in the clinic or home environment. The use of such instruments may assist in identifying older adults who are at risk for falling, a major problem that can result in impaired function and loss of independence.

METHOD

Six instruments were reviewed: the Berg Balance Scale (Berg), the Clinical Test of Sensory Interaction and Balance (CTSIB), the Functional Reach Test, the Tinetti Balance Test of the Performance-Oriented Assessment of Mobility Problems (Tinetti), the Timed "Up and Go" Test (TU&GT), and the Physical Performance Test (PPT). Considered were what aspects of balance are assessed, time needed to administer the instrument, tools or equipment needed, evidence of reliability and validity, advantages and disadvantages, and the target population.

RESULTS

The Berg, Tinetti, and PPT measure a variety of aspects of balance, whereas the Functional Reach, TU&GT, and CTSIB measure more narrow aspects of balance. All six instruments have been used with older adults and do not require much equipment. The instruments differ in their reliability and validity.

CONCLUSION

Familiarity with balance instruments can be helpful in selecting the one most appropriate for clinical setting and clients in order to institute appropriate prevention programs, such as environmental modifications and lifestyle adaptations.

The effect of acidic fibroblast growth factor and live yeast cell derivative on tympanic membrane regeneration in a rat model

The current treatment of choice for chronic tympanic membrane perforations is surgery. Recent studies using various polypeptide growth factors to accelerate closure of tympanic membrane perforations in model systems have produced mixed results. This study evaluates the effect of acidic fibroblast growth factor (AFGF) and live yeast cell derivative (LYCD) on the rate of healing of acute tympanic membrane perforations in a rat model. Thirty-seven rats had both ears separately randomized in a blinded fashion to receive AFGF in one of three concentrations, LYCD, or a control solution. The rats initially underwent subtotal removal of the tympanic membranes bilaterally. Solutions were applied to the randomized ears daily for 3 days, starting at the time of the surgical perforation. The ears were photographed every 3 to 8 days for 35 days. The photographs were digitally scanned and a computer analysis was used to calculate the percentage of residual perforation. No significant difference in the rate of healing was observed for ears treated with AFGF or LYCD versus the controls. Given the potential advantages of medical treatment of tympanic membrane perforations and the established efficacy of growth factors in other model systems, however, further research is warranted.

The effect of acidic fibroblast growth factor and live yeast cell derivative on tympanic membrane regeneration in a rat model

The current treatment of choice for chronic tympanic membrane perforations is surgery. Recent studies using various polypeptide growth factors to accelerate closure of tympanic membrane perforations in model systems have produced mixed results. This study evaluates the effect of acidic fibroblast growth factor (AFGF) and live yeast cell derivative (LYCD) on the rate of healing of acute tympanic membrane perforations in a rat model. Thirty-seven rats had both ears separately randomized in a blinded fashion to receive AFGF in one of three concentrations, LYCD, or a control solution. The rats initially underwent subtotal removal of the tympanic membranes bilaterally. Solutions were applied to the randomized ears daily for 3 days, starting at the time of the surgical perforation. The ears were photographed every 3 to 8 days for 35 days. The photographs were digitally scanned and a computer analysis was used to calculate the percentage of residual perforation. No significant difference in the rate of healing was observed for ears treated with AFGF or LYCD versus the controls. Given the potential advantages of medical treatment of tympanic membrane perforations and the established efficacy of growth factors in other model systems, however, further research is warranted.

Migraine-related vestibulopathy

Migraine has been associated with specific vestibular disorders, including benign paroxysmal vertigo of childhood and benign recurrent vertigo in adults. Migraine may also play a role in chronic nonspecific vestibulopathy. Because scant data exist that describe the clinical findings and vestibular function abnormalities in suspected migraine-related vestibulopathy, we reviewed the history, physical examination, vestibular tests (electronystagmography, rotational chair, posturography), and response to treatment of 100 patients with diagnoses of migraine-related vestibulopathy. Dominant clinical features included chronic movement-associated dysequilibrium, unsteadiness, space and motion discomfort, and occasionally, episodic vertigo as an aura prior to headache, or true vertigo without headache. Common vestibular test abnormalities included a directional preponderance on rotational testing, unilateral reduced caloric responsiveness, and vestibular system dysfunction patterns on posturography. Treatment was usually directed at the underlying migraine condition by identifying and avoiding dietary triggers and prescribing prophylactic anti-migraine medications. Symptomatic relief was also provided using anti-motion sickness medications, vestibular rehabilitation, and pharmacotherapy directed at any associated anxiety or panic disorder.

Functional outcome of vestibular rehabilitation in patients with abnormal sensory-organization testing

A goal of vestibular rehabilitation is to improve the functional status of patients with balance disorders. Despite the focus of vestibular rehabilitation on function, few objective data describe the outcome of vestibular rehabilitation in terms of balance function. In this prospective observational study, we tested a well-defined patient cohort (n = 67) with abnormal pretreatment sensory-organization testing who were undergoing vestibular rehabilitation. Patient outcomes were determined by using objective and subjective measures of function before and after rehabilitation. Overall, 60% of patients showed objective improvement of balance function; 25% of patients improved to normal. Analysis of success and failure of vestibular rehabilitation is important as an aid to appropriate patient counseling and efficient use of rehabilitation resources.

Update on skull base surgery

The field of skull base surgery has changed significantly during the past decade. Various surgical approaches have been developed, which when used alone or in combination provide optimal exposure for the resection of a given lesion with minimal morbidity. This recent evolution in the field of skull base surgery has allowed the surgical management of larger lesions in previously inaccessible locations. Furthermore, techniques in the preoperative, intraoperative, and postoperative management of the intrapetrous internal carotid artery have circumvented many prior limitations of cranial base resections. The goals of this article are to provide an overview of the postlateral skull base approaches in use today, discuss the regions of the skull base that are accessible, and describe the state of the art in management of the intrapetrous internal carotid artery.

Galvanic-induced postural movements as a test of vestibular function in humans

Galvanic stimulation produces a postural sway and eye movements in humans. Since galvanic currents are thought to exert their effect at the trigger zone of the vestibular nerve, an intact vestibular nerve should be necessary to produce a response. We have used galvanic stimulation in humans to test the hypothesis that intact vestibular nerve fibers are required to obtain a postural away response. Experimental subjects included normal subjects, patients who had undergone resection of an acoustic neuroma, and patients who had undergone vestibular neurectomy and surgical labyrinthectomy. Our results support the hypothesis that an intact vestibular nerve is necessary to produce a response. Moreover, two patients with recurrent vertigo following vestibular neurectomy and labyrinthectomy, who had absent ice-water caloric test responses in the operated ears, were found to have a positive galvanic response. This result suggested that their recurrent vertigo was based on intact residual vestibular nerve fibers. Although previous research has not yielded a routine clinical use for galvanic stimulation, our results suggest that galvanic stimulation of the vestibular system can provide unique and valuable diagnostic information.

A practical work-up for vertigo

Specific elements in the history and physical examination direct the work-up of the "dizzy" patient toward or away from a vestibular disorder. When a disorder of this type is suspected, the differential diagnosis includes benign positional vertigo, vestibular neuritis, vertebrobasilar insufficiency, migraine, and endolymphatic hydrops, which is the pathologic condition thought to underlie Meniere's disease. Anxiety is well recognized as a potential component of vestibular abnormalities or as the primary problem.

Excision of petroclival tumors by a total petrosectomy approach

The surgical removal of intradural petroclival tumors of any size is demanding because of the restricted surgical exposure and relation of the tumor with the brain stem, cranial nerves, and vertebrobasilar artery and branches. When petroclival tumors are large or giant sized and involve multiple areas of the clivus, adequate surgical exposure is difficult to achieve, yet is critical for safe tumor removal. In 17 patients with extensive petroclival tumors, total removal of the petrous bone was performed to gain a wide and shallow surgical exposure. This report details the intraoperative and postoperative complications, cranial nerve status, pre- and postoperative disability scores, and extent of tumor resection in these 17 patients. Deterioration of facial nerve function was the most common new cranial nerve injury following surgery. Three patients suffered major neurologic complications; six other patients suffered significant but temporary neurologic complications. Gross total tumor resection was accomplished in 9 of 17 patients, and most patients (15/17) maintained or improved their disability status. Tumor residual was related to cavernous sinus involvement, vascular encasement, or brainstem pial invasion. Total petrosectomy is an intensive and complex approach with inherent morbidity and thus should be reserved for extensive petroclival tumors that cannot be removed using less complicated approaches.

Combined approaches for resection of extensive glomus jugulare tumors. A review of 12 cases

Complete resection with conservation of cranial nerves is the primary goal of contemporary surgery for glomus jugulare tumors. This publication reports the value of combined surgical approaches in achieving this goal in 12 patients with extensive tumors. Eleven of these tumors were classified as Fisch Class C and/or D, while eight were categorized as Jackson-Glasscock Grade III or IV. Intracranial (intradural) extension was present in 10 patients; four patients had tumor extension into the clivus and two into the cavernous sinus. The petrous internal carotid artery (ICA) was involved in eight and the vertebral artery (VA) in one. Subtemporal-infratemporal, retrosigmoid, and/or extreme lateral transcondylar approaches were added to the usual transtemporal-infratemporal approach. This improved the exposure, provided early control of the petrous ICA, and facilitated tumor removal from the clivus, cavernous sinus, posterior fossa, and foramen magnum, allowing a single-stage resection in eight patients. Ten patients had a complete microscopic resection with no mortality. The facial nerve was preserved in nine cases, with tumor involvement requiring nerve resection followed by grafting in the remaining three. Mobilization of the facial nerve was avoided in five cases; of these, three had intact function and two had House-Brackmann Grade III function on follow-up review. Only one patient had a mild persistent swallowing difficulty. The ICA was preserved in 10 patients and resected in two, while the VA required reconstruction in one case. There were no instances of stroke, and blood transfusions were required in five patients who had tumors with nonembolizable ICA or VA feeders. While complete resection provides the best possibility for cure, the important role of adjuvant radiation therapy in cases with residual tumor is discussed. The importance of degrees of brain-stem compression and vascular encasement is emphasized in classifying the more extensive tumors.

Evolution and advances of the lateral surgical approaches to cranial base neoplasms

The evolution and advances of the lateral surgical approaches used for neoplasms of the cranial base involving the middle and posterior cranial fossa are reviewed. The lateral approaches available for access to the cranial base are diverse and are often used in combination. Approaches for tumors that are completely extradural, usually involving the temporal bone or infratemporal fossa, include the infratemporal fossa approach described by Fisch and the preauricular subtemporal-infratemporal fossa approach. Lateral approaches used to provide exposure of intradural tumors involving the clivus and traversing the middle and posterior cranial fossa are based on the following approaches: the frontotemporal orbitozygomatic, subtemporal/middle fossa, transpetrosal, lateral suboccipital, and transcondylar approaches. The great strides that have been made in the safe and effective surgical treatment of cranial base neoplasms are due, in part, to the availability of multiple surgical approaches and the ability to tailor the planned operative procedure to the precise location and extent of the cranial base tumor.

Clinical assessment of postural stability

It is important to evaluate both vestibulo-oculomotor and vestibulospinal pathways in patients with balance disorders. While moving-platform posturography can assess vestibulospinal function, the cost and time required to perform this test may limit its clinical use. A clinical office vestibulospinal evaluation that could be done quickly and inexpensively would be of benefit. In this study we used foam posturography to prospectively evaluate 50 patients with vestibular complaints to determine its predictive value in comparison with moving-platform posturography results. Our results demonstrate a significant correlation (p < 0.005) with a sensitivity and specificity of 95 percent and 90 percent, respectively, between the clinical office assessment using foam posturography and the results of moving-platform posturography. The ability of patients to utilize vestibular cues to maintain posture may be accurately assessed in a clinical office examination and should be useful to otolaryngologists to evaluate the vestibulospinal system.

Sources of error in use of beta-2 transferrin analysis for diagnosing perilymphatic and cerebral spinal fluid leaks

Beta-2 transferrin is a protein found in cerebral spinal fluid and inner ear perilymph, but not in blood, nasal, or ear secretions. The clinical use of this test has been previously demonstrated, but sources of test error have not been addressed. The purpose of this study was to evaluate sources of error related to this test in order to improve its clinical use. We reviewed the specimens submitted for beta-2 analysis over the first 12 months of test availability at our institution to identify potential factors leading to test error. Sources of error were categorized into the following groups: sample collection, delivery, and extraction factors; assay factors; physician-related factors; and patient-related factors. The test for beta-2 transferrin is a valuable diagnostic tool for the management of difficult clinical problems, provided the physician is aware of potential factors that can lead to test error and clinical mismanagement.

Neurotologic manifestations of Chiari 1 malformation

It is important for otolaryngologists to recognize Chiari malformations as part of the differential diagnosis of balance disorders because patients may initially be seen with symptoms referable to the vestibular system, including ataxia, nystagmus, or vertigo. The objective of this paper is to review the signs, symptoms, and vestibular test findings of a series of patients with Chiari 1 malformation. Six patients were identified by retrospective chart review with a diagnosis of Chiari malformation. Each patient had a complete otoneurologic examination and vestibular function testing. The results indicated that patients fell into two different vestibular test result profiles. First, patients with advanced symptoms demonstrated oculomotor dysfunction, central vestibular nystagmus, abnormal vestibular visual interaction, and abnormal tilt suppression of postrotatory nystagmus. On the other hand, a number of patients were identified with incidentally noted Chiari malformation on magnetic resonance imaging scan who had a vestibular test profile consistent with peripheral vestibulopathy without signs and symptoms of central nervous system dysfunction. Guidelines are provided to help determine the extent of the group of symptoms attributable to an incidentally discovered Chiari malformation.

Translabyrinthine approach to skull base tumors with hearing preservation

The improvement in surgical techniques and the experience gained in treatment of skull base tumors have stimulated more aggressive management of larger lesions. Patients presenting with limited preoperative deficits have challenged the surgeon to design the surgical approach so as to minimize postoperative morbidity and preserve function. Tumors of the middle fossa and clivus with extension into the posterior fossa are usually approached by a combined subtemporal, transtentorial, transpetrous approach. In patients with preoperative hearing, the surgical exposure is often limited by the labyrinthine portion of the otic capsule. The technique of partial labyrinthectomy, removing the posterior and/or superior semicircular canals, maximizes exposure with preservation of hearing. This report details our experience with the partial labyrinthectomy approach for 14 patients with large skull base lesions. All patients had hearing preserved despite sacrifice of one or two of the semicircular canals. Bone pure-tone averages and speech discrimination scores were maintained near their preoperative levels. The indications, benefits, techniques, and hearing results of this approach are reviewed.