Investigating the impact of non-gated thoracic CT prior to CTCA to reduce layered testing

AIM

To determine the proportion of computed tomography (CT) coronary angiography (CTCA) referrals with coronary artery calcification (CAC) evident on previous non-cardiac CT imaging and how this impacted the diagnostic yield for CTCA, the requirement for additional diagnostic testing, and the associated costs to confirm or refute obstructive coronary artery disease (CAD).

MATERIALS AND METHODS

A retrospective review of CTCA examinations was undertaken between 01/05/2018 and 31/05/2020 in which the examinations were cross referenced for previous non-gated thoracic CT at Royal United Hospitals Bath. Major epicardial vessel CAC on baseline CT was re-evaluated by published semi-quantitative methods, giving a per-patient CAC score (mild = 1-3, moderate = 4-6, severe >6). Subsequent incomplete CTCA diagnostic yield, further testing, and cost implications were examined.

RESULTS

Of the 2140 CTCA examinations identified, 13% (280/2140) had a preceding non-gated thoracic CT (53% female, age 63 ± 11 years). The incomplete diagnostic rate increased with CAC grade, mild 32%, (RR 12; 95% CI 4-40), moderate 64% (RR 25; 95% CI 8-80), severe 75%, (RR 29; 95% CI 9-94). Additional diagnostic testing occurred in 4% for the mild CAC category, and 14% and 42% for moderate and severe, respectively. When severe CAC was identified on a non-gated thoracic CT a cost saving of £171/patient (dobutamine stress echo [DSE]) and £61/patient (myocardial perfusion scintigraphy [MPS]) was established with a direct to functional testing pathway.

CONCLUSIONS

In patients referred for CTCA where severe CAC was identified on a preceding non-gated thoracic CT a direct to functional testing altered management in 42% of cases and was cost-effective.

FFRCT and Invasive Coronary Angiography – assessing concordance in an unselected UK real world population

Background/Introduction

CT coronary angiography (CTCA) Fractional Flow Reserve (FFRCT) is a key investigation in chronic coronary syndrome (CCS) guidelines. FFR calculated from CTCA may help improve CTCA specificity for flow limiting disease, preventing unnecessary invasive coronary angiography (ICA).

Purpose

To (1) assess the treatment planning potential of FFRCT by determining the concordance of FFRCT with an ICA +/− invasive physiological assessment for the detection of flow limiting CAD in a real world NHS setting and (2) concordance sub-analysis of concordance of invasive iFR and FFRCT.

Methods

A single-centre retrospective analysis of a prospectively maintained clinical CTCA database. We identified patients with CCS who had CTCA FFRCT and subsequent ICA from August 2018 to January 2021. Concordance was assessed on a per patient and per vessel basis (major epicardial vessels: left main stem [LMS], left anterior descending artery [LAD], circumflex [LCx], right coronary artery [RCA]). Two non-invasive ischaemia thresholds were examined an FFRCT ≤0.8 and <0.75 (2 cm distal to stenosis). This was compared to a clinical ICA assessment where a flow limiting lesion was defined as a stenosis >70% (or >50% in the LMS) and/or an end vessel iFR ≤0.89 / FFR ≤0.8. All vessels that underwent an iFR, at the interventionists discretion, were then assessed relative to their end-vessel FFRCT.

Results

565 patients had a CTCA with FFRCT and 164 patients had a subsequent ICA and were suitable for analysis. On a per patient basis 69% of those referred to ICA with an FFRCT ≤0.8 of at least one major epicardial vessel had any flow limiting CAD at ICA. With an FFRCT <0.75 this was 73%. Table 1 illustrates the per vessel concordance.

A total of 120 vessels were included in the iFR subsection analysis. The mean FFRCT was 0.71 (±0.13) and mean iFR was 0.89 (±0.1). Accuracy was 54% (95% CI 45–63%) with a sensitivity of 89% (95% CI 76–96%), specificity 32% (95% CI 22–44%), positive predictive value 45% (95% CI 40–50%) and negative predictive value of 83% (95% CI 66–92%). A Pearson's correlation coefficient of 0.23 was found.

Conclusion

This study demonstrated that the negative predictive value of FFRCT was excellent, including importantly for LMS analysis. The specificity on a per vessel basis was good with the exception of the LAD assessment. This may have implications for interventional planning with this imaging modality. FFRCT correlated poorly with invasive iFR in this subsection analysis although selection bias may be contributing. There remains a significant proportion of patients referred for an ICA where no flow limiting CAD is found.

Funding Acknowledgement

Type of funding sources: None. Table 1. Per vessel concordance analysis of potential flow limiting FFRCT relative to clinical ICA findings. Analysed with an ischaemia threshold of FFRCT ≤0.80 and <0.75. PPV = Positive Predictive Value. NPV = Negative Predictive Value.

23 Frailty, Older Age-Associated Conditions, and Multimorbidity Amongst People Experiencing Homelessness in A Hostel in London

Introduction

People experiencing homelessness (PEH) face poor health outcomes and extreme health inequity, and evidence suggests earlier onset of older age-associated conditions and signs of premature ageing. This is the first UK study to assess frailty in this population. The objective was to assess frailty, age-associated conditions, and multimorbidity in PEH residing in hostel accommodation, drawing comparisons with population data.

Methods

Participants were drawn from a hostel in London for PEH aged over 30. Age-associated conditions were identified using validated tools and a questionnaire modelled on comprehensive geriatric assessments. Participants’ keyworkers completed questionnaires to provide collateral information. Frailty was defined according to five criteria in Fried’s phenotype model: participants with three or more criteria are classified as frail, one or two criteria as vulnerable, and no criteria as not frail. Multimorbidity was defined as the presence of two or more long-term conditions in one person. Comparisons were made with population data from The English Longitudinal Study of Ageing and Health Survey for England.

Results

Thirty-three people participated (83% of eligible residents), with a mean age of 55.7 years (range 38–74). Frailty was identified in 18/33 participants (55%), with 13/33 (39%) classified as vulnerable, and 2/33 (6%) as not frail. Participants met an average of 2.6/5 frailty phenotype criteria, comparable to 90-year-olds in the general population. The most common age-associated conditions identified were: falls (in 61%), visual impairment (61%), low grip strength (61%), mobility impairment (52%), and cognitive impairment (45%). Multimorbidity was present in all thirty-three participants.

Conclusions

A wide range of unmet health needs was identified. The high prevalence of frailty and age-associated conditions support evidence of premature ageing, indicating a need to include holistic older-age assessments in PEH at a younger age. Involvement of health professionals with experience of working with older people could contribute to improving health outcomes for homeless patients.

A Site-Specific, Sustained-Release Drug Delivery System for Aneurysmal Subarachnoid Hemorrhage

Nimodipine is the only drug approved for use by the Food and Drug Administration for improving outcome after aneurysmal subarachnoid hemorrhage (SAH). It has less than optimal efficacy, causes dose-limiting hypotension in a substantial proportion of patients, and is administered enterally 6 times daily. We describe development of site-specific, sustained-release nimodipine microparticles that can be delivered once directly into the subarachnoid space or cerebral ventricles for potential improvement in outcome of patients with aneurysmal SAH. Eight injectable microparticle formulations of nimodipine in poly(DL-lactide-co-glycolide) (PLGA) polymers of varying composition were tested in vitro, and 1 was advanced into preclinical studies and clinical application. Intracisternal or intraventricular injection of nimodipine-PLGA microparticles in rats and beagles demonstrated dose-dependent, sustained concentrations of nimodipine in plasma and cerebrospinal fluid for up to 29 days with minimal toxicity in the brain or systemic tissues at doses <2 mg in rats and 51 mg in beagles, which would be equivalent of up to 612-1200 mg in humans, based on scaling relative to cerebrospinal fluid volumes. Efficacy was tested in the double-hemorrhage dog model of SAH. Nimodipine-PLGA microparticles significantly attenuated angiographic vasospasm. This therapeutic approach shows promise for improving outcome after SAH and may have broader applicability for similar diseases that are confined to body cavities or spaces, are self-limited, and lack effective treatments.

Status and characterization of the lithium beam diagnostic on DIII-D

The 30 keV lithium beam diagnostic on DIII-D is suitable to measure both the radial electron density and poloidal magnetic field profiles in the pedestal. The refurbished system features a new setup to measure the Doppler shift allowing accurate alignment of the spectral filters. The injector has been optimized to generate a stable lithium neutral beam with a current of I = 15-20 mA and a diameter of 1.9 ± 0.1 cm measured by beam imaging. The typical temporal resolution is Δt = 1-10 ms and the radial resolution of ΔR = 5 mm is given by the optical setup. A new analysis technique based on fast Fourier transform avoids systematic error contributions from the digital lock-in analysis and accounts intrinsically for background light correction. Latest upgrades and a detailed characterization of the system are presented. Proof-of-principle measurements of the poloidal magnetic field with a statistical error of typically 2% show a fair agreement with the predictions modeled with the Grad-Shafranov equilibrium solver EFIT within 4%.

Comparison of collisional radiative models for edge electron density reconstruction from Li I (2s-2p) emission profiles

Four collisional radiative models (CRMs) for reconstruction of the edge electron density profile from the measured Li I (2s-2p) emission profile of an accelerated lithium beam are compared using experimental data from DIII-D. It is shown for both L- and H-mode plasmas that edge density profiles reconstructed with the CRMs DDD2, ABSOLUT, [Sasaki et al. Rev. Sci. Instrum. 64, 1699 (1993)] and a new model developed at DIII-D agree in a density scan from n(e) (ped) = (2.0-6.5) × 10(19) m(-3) within 20%, 20%, <5%, and 40%, respectively, of the pedestal density measured with Thomson scattering. Profile shape and absolute density vary in a scan of the effective ion charge Z(eff) = 1-6 up to a factor of two but agree with Thomson data for Z(eff) = 1-2 within the error bars.

Investigation of TBR1 Hemizygosity: Four Individuals with 2q24 Microdeletions

TBR1 encodes a transcription factor with critical roles in corticogenesis, including cortical neuron migration and axon pathfinding, establishment of regional and laminar identity of cortical neurons, and control of glutamatergic neuronal cell fate. Based upon TBR1's role in cortical development, we sought to investigate TBR1 hemizygosity in individuals referred for genetic evaluation of intellectual disability and developmental delay. We describe 4 patients with microdeletions identified by molecular cytogenetic techniques, encompassing TBR1 and spanning 2q24.1q31.1, ranging in size from 2.17 to 12.34 Mb. Only the patient with the largest deletion had a possible cortical malformation. Mild ventriculomegaly is the only common brain anomaly, present in all patients; a Chiari I malformation is seen in 2 patients, and mega cisterna magna is seen in a third. Our findings are consistent with Tbr1 mouse models showing that hemizygosity of the gene requires additional genetic factors for the manifestation of severe structural brain malformations. Other syndromic features are present in these patients, including autism spectrum disorders, ocular colobomas, and craniosynostosis, features that are likely affected by the deletion of genes other than TBR1.

Photochemical dimerization of parinaric acid in lipid bilayers

Parinaric acid (9,11,13,15-octadecatetraenoic acid), a conjugated tetraene fatty acid, undergoes a second-order photochemical reaction in phospholipid bilayers. The reaction results in the loss of the characteristic absorption of this chromophore and the development of new absorption demonstrating the presence of a triene chromophore. The progress of this reaction is easily monitored by measurement of the decrease in the fluorescence intensity from a uniformly illuminated sample. The reaction rate measured in this way is sensitive to the thermal phase transition of the bilayer and to the presence of cholesterol. The relationship of the second-order rate constant to the lipid diffusion coefficient is discussed. This relationship differs from that previously used for the analysis of similar photochemical processes.

Infectious arthritis of the knee caused by Mycobacterium terrae: a case report

Mycobacterium terrae is ubiquitous in our environment. M terrae infections most commonly involve tendon sheaths, bones, bursae, and joints. We report a case of infectious arthritis of the knee caused by M terrae in a 21-year-old man who had non-specific chronic synovitis. No organism was seen on microscopy or isolated from cultures until months later. Initially the M terrae culture was considered a contaminant and specific anti-mycobacterial treatment was not advised. The patient was commenced on suppressive therapy for persistent effusion and discomfort. Eventually, the M terrae infection was confirmed and he was commenced on clarithromycin, ciprofloxacin, and ethambutol. The triple antibiotic regimen was continued for 2 years. The knee improved but never completely settled. The patient chose to cease all antibiotic medication. The knee remained swollen and irritable, with little chance of eradicating the organism.

Agonist-dependent cannabinoid receptor signalling in human trabecular meshwork cells

BACKGROUND AND PURPOSE

Trabecular meshwork (TM) is an ocular tissue involved in the regulation of aqueous humour outflow and intraocular pressure (IOP). CB1 receptors (CB1) are present in TM and cannabinoid administration decreases IOP. CB1 signalling was investigated in a cell line derived from human TM (hTM).

EXPERIMENTAL APPROACH

CB1 signalling was investigated using ratiometric Ca2+ imaging, western blotting and infrared In-Cell Western analysis.

KEY RESULTS

WIN55212-2, a synthetic aminoalkylindole cannabinoid receptor agonist (10-100 microM) increased intracellular Ca2+ in hTM cells. WIN55,212-2-mediated Ca2+ increases were blocked by AM251, a CB1 antagonist, but were unaffected by the CB2 antagonist, AM630. The WIN55,212-2-mediated increase in [Ca2+]i was pertussis toxin (PTX)-insensitive, therefore, independent of Gi/o coupling, but was attenuated by a dominant negative Galpha(q/11) subunit, implicating a Gq/11 signalling pathway. The increase in [Ca2+]i was dependent upon PLC activation and mobilization of intracellular Ca2+ stores. A PTX-sensitive increase in extracellular signal-regulated kinase (ERK1/2) phosphorylation was also observed in response to WIN55,212-2, indicative of a Gi/o signalling pathway. CB1-Gq/11 coupling to activate PLC-dependent increases in Ca2+ appeared to be specific to WIN55,212-2 and were not observed with other CB1 agonists, including CP55,940 and methanandamide. CP55940 produced PTX-sensitive increases in [Ca2+]i at concentrations>or=15 microM, and PTX-sensitive increases in ERK1/2 phosphorylation.

CONCLUSIONS AND IMPLICATIONS

This study demonstrates that endogenous CB1 couples to both Gq/11 and Gi/o in hTM cells in an agonist-dependent manner. Cannabinoid activation of multiple CB1 signalling pathways in TM tissue could lead to differential changes in aqueous humour outflow and IOP.

Solid-State Coordination Chemistry of the Cu/Triazolate/X System (X = F-, Cl-, Br-, I-, OH-, and SO42-)

Hydrothermal reactions of 1,2,4-triazole with the appropriate copper salt have provided eight structurally unique members of the Cu/triazolate/X system, with X = F-, Cl-, Br-, I-, OH-, and SO4(2-). The anionic components X of [Cu3(trz)4(H2O)3]F2 (1) and [Cu6(trz)4Br]Cu4Br4(OH) (4) do not participate in the framework connectivity, acting as isolated charge-compensating counterions. In contrast, the anionic subunits X of [Cu(II)Cu(I)(trz)Cl2] (2), [Cu6(trz)4Br2] (3), [Cu(II)Cu(I)(trz)Br2] (5), [Cu3(trz)I2] (6), [Cu6(II)Cu2(I)(trz)6(SO4)3(OH)2(H2O)] (8), and [Cu4(trz)3]OH.7.5H2O (9.7.5H2O) are intimately involved in the three-dimensional connectivities. The structure of [Cu(II)Cu(I)(trz)2][Cu3(I)I4] (7) is constructed from two independent substructures: a three-dimensional cationic {Cu2(trz)2}n(n+) component and {Cu3I4}n(n-) chains. Curiously, four of the structures are mixed-valence Cu(I)/Cu(II) materials: 2, 5, 7, and 8. The only Cu(II) species is 1, while 3, 4, 6, and 9.7.5H2O exhibit exclusively Cu(I) sites. The magnetic properties of the Cu(II) species 1 and of the mixed-valence materials 5, 7, 8, and the previously reported [Cu3(trz)3OH][Cu2Br4] have been studied. The temperature-dependent magnetic susceptibility of 1 conforms to a simple isotropic model above 13 K, while below this temperature, there is weak ferromagnetic ordering due to spin canting of the antiferromagnetically coupled trimer units. Compounds 5 and 7 exhibit magnetic properties consistent with a one-dimensional chain model. The magnetic data for 8 were fit over the temperature range 2-300 K using the molecular field approximation with J = 204 cm(-1), g = 2.25, and zJ' = -38 cm(-1). The magnetic properties of [Cu3(trz)3OH][Cu2Br4] are similar to those of 8, as anticipated from the presence of similar triangular {Cu3(trz)3(mu3-OH)}(2+) building blocks. The Cu(I) species 3, 4, 6, and 9 as well as the previously reported [Cu(5)(trz)3Cl2] exhibit luminescence thermochromism. The spectra are characterized by broad emissions, long lifetimes, and significant Stokes' shifts, characteristic of phosphorescence.

Emergency eye care in rural Australia: role of internet

PURPOSE

Significant differences exist in the utilization of emergency eye care services in rural and urban Australia. Meanwhile, influence of internet-based technology in emergency eye care service utilization has not been established. This study aims to demonstrate, from a health provider perspective, an internet-based service's impact on emergency eye care in rural Australia.

METHODS

The teleophthalmology service was initiated in the Carnarvon Regional Hospital (CRH) of the Gascoyne region in Western Australia. A digital, slit lamp and fundus camera were used for the service. Economic data was gathered from the Department of Health of Western Australia (DOHWA), the CRH and the Lions Eye Institute.

RESULTS

During the study period (January-December, 2003) 118 persons took part in teleophthalmology consultations. Emergency cases constituted 3% of these consultations. Previous year, there were seven eye-related emergency evacuations (inter-hospital air transfers) from the Gascoyne region to City of Perth.

CONCLUSIONS

Analysis demonstrates implementation of internet-based health services has a marked impact on rural emergency eye care delivery. Internet is well suited to ophthalmology for the diagnosis and management of acute conditions in remote areas. Integration of such services to mainstream health care is recommended.

Observation of weak impact of a stochastic magnetic field on fast-ion confinement

Fast ions are observed to be very well confined in the Madison Symmetric Torus reversed field pinch despite the presence of stochastic magnetic field. The fast-ion energy loss is consistent with the classical slowing down rate, and their confinement time is longer than expected by stochastic estimates. Fast-ion confinement is measured from the decay of d-d neutrons following a short pulse of a 20 keV atomic deuterium beam. Ion confinement agrees with computation of particle trajectories in the stochastic magnetic field, and is understood through consideration of ion guiding center islands.

Comparison of immunomodulator mRNA and protein expression in the lungs of Stachybotrys chartarum spore-exposed mice

Stachybotrys chartarum is an important toxigenic fungus that has been associated with respiratory disease onset in animals and humans. It can be separated into macrocyclic trichothecene-producing and nonproducing chemotypes based on secondary metabolite production. However, effects of spores of the two chemotypes on lung inflammatory responses are poorly understood. In this study, real-time reverse-transcription polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assay (ELISA) were used to investigate time-course (1, 3, 6, 24, and 48 h post-instillation [PI]) relationships in mice intratracheally exposed to 300 spores/g body weight of a macrocyclic trichothecene-producing (JS 58-17) and a nonproducing (JS 58-06) S. chartarum isolate and of Cladosporium cladosporioides. There were marked differences in the magnitude and temporal patterns of mouse lung immune responses to intratracheal exposure to spores of these species at this spore dose. Both macrophage inflammatory protein 2 (MIP-2) and surfactant protein-D (SP-D) mRNA expression were significantly upregulated in lungs of JS 58-17-treated animals compared to that of all other treatment animals at 6 and 24 h PI. Heightened mRNA expression of these immunomodulators combined with comparatively depressed MIP-2 and tumor necrosis factor (TNF)-a protein expression suggests that the action of macrocyclic trichothecenes sequestered in 58-17 spores is involved. Interestingly, TNF-a protein expression in all spore treatment animal groups was also significantly increased over that in saline controls. Similarities in expression among all spore treatment animals suggest that chemicals other than toxic secondary metabolites, and possibly spore-sequestered 1,3-beta-D-glucan, may contribute to lung pathogenesis.

Comparison of inflammatory and cytotoxic lung responses in mice after intratracheal exposure to spores of two different Stachybotrys chartarum strains

Stachybotrys chartarum is an important toxigenic fungus that has been associated with respiratory disease onset in animals and humans. While it can be separated into macrocyclic trichothecene- and atranone-producing chemotypes based on secondary metabolite production, effects of spores of the two chemotypes on lungs are poorly understood. In this study we used bronchoalveolar lavage fluid (BALF) to investigate dose-response (30, 300, 3000 spores/g body weight [BW]) and time-course (3, 6, 24, 48, 96 h post instillation [PI]) relationships in mice to exposure of macrocyclic trichothecene- (JS 58-17) and atranone-producing (JS 58-06) S. chartarum strains, as well as Cladosporium cladosporioides spores. BALF total protein, albumin, pro-inflammatory cytokine (IL-1beta, IL-6, and tumor necrosis factor-alpha [TNF-alpha]), and lactate dehydrogenase (LDH) concentrations showed significant (p < 0.05) fungal species (S. chartarum vs. C. cladosporioides) and strain (58-17 vs. 58-06), spore dose and time dependent changes. The no adverse effect level (NOAEL) due to exposure to spores of JS 58-17 and JS 58-06 was < 30 spores/g BW; for C. cladosporioides it was < 300 spores/g BW. At moderate and high S. chartarum doses, BALF composition reflects differences in strain toxicity while at the lowest dose, BALF composition of either S. chartarum strain were similar. This suggests that at low spore doses, it is spore sequestered factors common to both strains not strain dependent toxins that are contributing to lung disease onset.

Electron heat transport measured in a stochastic magnetic field

New profile measurements have allowed the electron thermal diffusivity profile to be estimated from power balance in the Madison Symmetric Torus where magnetic islands overlap and field lines are stochastic. The measurements show that (1) the electron energy transport is conductive not convective, (2) the measured thermal diffusivities are in good agreement with numerical simulations of stochastic transport, and (3) transport is greatly reduced near the reversal surface where magnetic diffusion is small.

Which primary shoulder and elbow replacement? A review of the results of prostheses available in the UK

To assist surgeons select a suitable prosthesis, we have undertaken a detailed review of all shoulder and elbow replacements currently marketed in the UK. Twenty shoulder and 8 elbow implants, manufactured by 16 companies, have been identified. Twelve of the shoulder and one of the elbow implants have been introduced or modified in the last 8 years and have no clinical results published in peer-reviewed journals. Only the Biomodular, Bipolar, Copeland, Isoelastic, Neer hemi, Neer II, Roper-Day and Select shoulders accounting for less than 40% of the UK shoulder market, possess published results. The Capitello-condylar, Coonrad-Morrey, GSB III, Kudo, Liverpool, Roper-Tuke and Souter-Strathclyde elbows all have published results. These account for over 95% of all UK elbow replacements. The implications of these findings in an era of evidence-based medicine is discussed. Reviewing the clinical results should be of primary importance in the selection of a suitable prosthesis. Implants with a proven long-term record must represent the 'gold standard'. New or modified implants should only be used if they are part of a properly conducted clinical trial.

PCG boards. Social climbers

A national survey of PCG chief executives and social services representatives on PCG boards showed that most consider the social services role 'very useful'. Most social services representatives spent two to four days a month on PCG business. Two-thirds felt they needed more time. Almost half felt they had little or no support. Better feedback mechanisms are needed for social services representatives.

Strategic pooling of compounds for high-throughput screening

Bringing new medicines to the market depends on the rapid discovery of new and effective drugs, often initiated through the biological testing of many thousands of compounds in high-throughput screening (HTS). Mixing compounds together into pools for screening is one way to accelerate this process and reduce costs. This paper contains both theoretical and experimental data which suggest that careful selection of compounds to be pooled together is necessary in order to reduce the risk of reactivity between compounds within the pools.

Joint working. Prospects of partnership

Joint working between organisations and professions is a key part of many of this government's initiatives, including health action zones. To work effectively together, professionals must overcome the problems of different cultures and different patterns of accountability. Teamworking across the boundaries of health and social care is generally inadequate.

Joint working. Take your partners

The white paper proposals for partnerships in the NHS of the future are much less developed than those for performance. It is unclear whether collaborative activities are discretionary or mandatory. Effective inter-agency co-operation will require central government to give joint working a higher priority.

Joint working. Local differences

The interface between social care and primary healthcare remains underdeveloped. Where joint working is effective, it is the result of co-operation, trust and mutual respect. Successful local networks take account of professional autonomy.

Children's services. The youth of today

Few authorities have joint commissioning of mental health services for children and adolescents. But the introduction of children's services plans in April offers an important opportunity, argues Bob Hudson.

Electric response audiometry in young children before cochlear implantation: a short latency component

OBJECTIVE

Evaluation of a short latency component (SLC) observed in profoundly deaf young children during recordings of the auditory brain stem response (ABR) before cochlear implantation.

DESIGN

Seventy young children (ages 2 to 11 yr) were investigated as part of their routine audiologic and diagnostic assessment, before cochlear implantation. The ABR was evoked using click stimuli and tone pips (500 Hz and 1 kHz) at intensity levels up to 105 dB nHL. The incidence of the SLC arising at a latency of 3 msec with high level click stimuli, in addition to residual ABR waves, was assessed.

RESULTS

An SLC was observed in a total of 18 of the 70 children investigated. It was present in 15 out of 31 congenitally deaf children (48%) compared with only 2 out of 33 children deafened after meningitis (6%). A chi-squared test employing a 2 x 2 contingency table shows that this dependency on etiology of deafness is highly statistically significant (p < 0.001). The presence of the SLC in the congenitally deaf children is related to age at the time of the Electric Response Audiometry test and is more likely to be observed in the younger child (p < 0.01).

CONCLUSIONS

Interpretation of the ABR in profoundly deaf children should take into consideration the possible presence of the SLC. An evoked potential arising from stimulation of the vestibular system, particularly the vestibular nuclei, is proposed as a likely origin for this component. Damage to sensory cells in the vestibular portion of the labyrinth might explain why an SLC is seen rarely in cases of deafness after meningitis.