Automobile airbag impulse noise: otologic symptoms in six patients

An in-depth technical and medical investigation of facial injuries caused by car accidents

BACKGROUND

Many studies have investigated the issue of facial injuries caused by car accidents, but only a few have addressed the technical and clinical aspects of such accidents and injuries in depth. The aim of this study was to identify risk factors and protective elements for facial injuries in car accidents.

METHODS

We analysed the technical and clinical data of patients with facial injuries caused by car accidents over a 16-year period (2000-2016) and investigated the following factors: sitting position, sex, age, accident time, use of a seatbelt, deployment of the front airbag, direction of impact, speed at the time of collision, and occurrence and location of facial injuries.

RESULTS

Of the 1291 patients involved in car accidents who were included in our study, 291 (22.5%) had suffered facial injuries. We found a significant association between occurrence of facial injuries and sex, speed at the time of collision, impact from the back, seatbelt usage, and deployment of the front airbag. In accidents occurring at speeds over 40 km/h, automobile security measures had no significant influence on the occurrence of facial injuries in drivers and front-seat passengers. In accidents occurring at speeds between 0 and 20 km/h, seatbelt usage (without airbag deployment) solely showed a significant protective influence against the occurrence of facial injuries (odd ratio [OR], 0.130; confidence interval [CI], 0.038-0.451). In contrast, patients who were in accidents at speeds between 21 and 40 km/h suffered significantly fewer facial injuries when wearing a seatbelt with the front airbag being deployed (OR, 0.245; CI, 0.091-0.665) or undeployed (OR, 0.216; CI, 0.084-0.561).

CONCLUSION

Male sex and a high speed at the time of collision are significant risk factors for the occurrence of facial injuries. The security measurements evaluated in this study only exerted a protective influence at low speeds (below 40 km/h). This indicates a possible weakness of these security systems with regard to preventing facial injuries. Engineers could benefit from these findings and improve the efficiency of existing security measures and eventually help decrease the incidence of facial injuries.

[Hidden hearing loss-damage to hearing processing even with low-threshold noise exposure?]

BACKGROUND

New research in animal models indicates that even at lower intensities, noise exposure can induce defects in the synapses of the auditory pathway. However, only very high levels of noise exposure lead to mechanical hair cell damage with lesions of the inner ear and measurable hearing loss (audiogram; distortion product otoacoustic emissions, DPOAE). This paper revises the literature, starting with a case study.

CASE HISTORY

A 41-year-old patient suffered from hearing loss and tinnitus in the right ear following a car accident with airbag deployment. Hearing loss recovered partially, tinnitus and difficulties in speech discrimination persisted. Audiometry showed typical high-frequency hearing loss (40 dB) and tonal tinnitus (8 kHz). Although DPOAE and ABR potentials (auditory brainstem response, wave III and V) were completely normal 6 months after the accident, there was no detectable cochlear action potential (CAP) in electrocochleography (ECochG).

DISCUSSION

These findings indicate recovery of initial hair cell damage, whereas synaptic transformation remains reduced and slight hearing loss and poor speech perception in complex listening situations persist. This phenomenon has been described as "hidden hearing loss" in newer literature. Although similar retrocochlear lesions in the auditory pathway could be detected in animal models, valid data in humans are currently lacking because no adequate diagnostic methods are available.

CONCLUSION

Noise trauma initially results in hair cell damage. After recovery, hearing loss may persist, which can be due to synaptic lesions in the first neuron. An adequate testbattery has to be developped.

Ginkgo biloba for tinnitus

BACKGROUND

This is an update of a Cochrane review first published in The Cochrane Library in Issue 2, 2004 and previously updated in 2007 and 2009.Tinnitus can be described as the perception of sound in the absence of external acoustic stimulation. At present no specific therapy for tinnitus is acknowledged to be satisfactory in all patients. There are a number of reports in the literature suggesting that Ginkgo biloba may be effective in the management of tinnitus. However, there also appears to be a strong placebo effect in tinnitus management.

OBJECTIVES

To assess the effect of Ginkgo biloba in patients who are troubled by tinnitus.

SEARCH METHODS

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; AMED; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; ICTRP and additional sources for published and unpublished trials. The date of the most recent search was 12 March 2012.

SELECTION CRITERIA

Adults (18 years and over) complaining of tinnitus or adults with a primary complaint of cerebral insufficiency, where tinnitus forms part of the syndrome.

DATA COLLECTION AND ANALYSIS

Both original authors independently extracted data and assessed trials for quality. For the 2012 update two authors determined trial eligibility, extracted data, analysed data and updated the contents of the review.

MAIN RESULTS

Four trials with a total of 1543 participants were included in the review; we assessed all the included studies as having a low risk of bias. Three trials (1143 participants) included patients with a primary complaint of tinnitus and one (400 participants) included patients with mild to moderate dementia, some of whom had tinnitus.There was no evidence that Gingko biloba was effective in patients with a primary complaint of tinnitus. In the study of patients with dementia, mean baseline levels of tinnitus were low (1.7 to 2.5 on a 10-point subjective symptom rating scale). A small but statistically significant reduction of 1.5 and 0.7 points was seen in patients taking Gingko biloba with vascular dementia and Alzheimer's disease respectively. The practical clinical significance of this is unclear. The incidence of side effects was low.

AUTHORS' CONCLUSIONS

The limited evidence does not demonstrate that Ginkgo biloba is effective for tinnitus when this is the primary complaint.

Sound therapy (masking) in the management of tinnitus in adults

BACKGROUND

This is an update of a Cochrane Review first published in The Cochrane Library in Issue 12, 2010.Tinnitus is described as the perception of sound or noise in the absence of real acoustic stimulation. Numerous management strategies have been tried for this potentially debilitating, heterogeneous symptom. External noise has been used as a management tool for tinnitus, in different capacities and with different philosophical intent, for over a century.

OBJECTIVES

To assess the effectiveness of sound-creating devices (including hearing aids) in the management of tinnitus in adults. Primary outcome measures were changes in the loudness or severity of tinnitus and/or impact on quality of life. Secondary outcome measures were change in pure-tone auditory thresholds and adverse effects of treatment. 

SEARCH METHODS

We searched the Cochrane ENT Group Trials Register; CENTRAL; PubMed; EMBASE; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; ICTRP and additional sources for published and unpublished trials. The date of the most recent search was 8 February 2012.

SELECTION CRITERIA

Prospective randomised controlled trials recruiting adults with persistent, distressing, subjective tinnitus of any aetiology in which the management strategy included maskers, noise-generating device and/or hearing aids, used either as the sole management tool or in combination with other strategies, including counselling.

DATA COLLECTION AND ANALYSIS

Two authors independently examined the 387 search results to identify studies for inclusion in the review, of which 33 were potentially relevant. The update searches in 2012 retrieved no further potentially relevant studies. Both authors extracted data independently.

MAIN RESULTS

Six trials (553 participants) are included in this review. Studies were varied in design, with significant heterogeneity in the evaluation of subjective tinnitus perception, with different scores, scales, tests and questionnaires as well as variance in the outcome measures used to assess the improvement in tinnitus sensation/quality of life. This precluded meta-analysis of the data. There was no long-term follow-up. We assessed the risk of bias as medium in three and high in three studies. Following analysis of the data, no significant change was seen in the loudness of tinnitus or the overall severity of tinnitus following the use of sound therapy compared to other interventions such as patient education, 'relaxation techniques', 'tinnitus coping strategies', counselling, 'tinnitus retraining' and exposure to environmental sounds. No side effects or significant morbidity were reported from the use of sound-creating devices.

AUTHORS' CONCLUSIONS

The limited data from the included studies failed to show strong evidence of the efficacy of sound therapy in tinnitus management. The absence of conclusive evidence should not be interpreted as evidence of lack of effectiveness. The lack of quality research in this area, in addition to the common use of combined approaches (hearing therapy plus counselling) in the management of tinnitus are, in part, responsible for the lack of conclusive evidence. Other combined forms of management, such as tinnitus retraining therapy, have been subject to a Cochrane Review. Optimal management may involve multiple strategies.

Repetitive transcranial magnetic stimulation for tinnitus

BACKGROUND

Tinnitus is the perception of sound, in the ear or in the head, in the absence of any external acoustic stimulation. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive means of inducing electrical currents in the brain, and has received increasing attention in recent years for the treatment of many neuropsychiatric disorders, including tinnitus.

OBJECTIVES

To assess the effectiveness and safety of rTMS versus placebo in patients with tinnitus.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; ICTRP and additional sources for published and unpublished trials. The date of the most recent search was 24 May 2011.

SELECTION CRITERIA

Randomised controlled trials of rTMS versus sham rTMS.

DATA COLLECTION AND ANALYSIS

Two review authors reviewed the titles, abstracts and keywords of all records retrieved. Three review authors independently collected and extracted data, and assessed the risk of bias of the trials.

MAIN RESULTS

Five trials comprising of 233 participants met our inclusion criteria. Each study described the use of a different rTMS device that delivered different waveforms at different frequencies. All five trials were relatively small studies but generally they demonstrated a low risk of bias.When considering the impact of tinnitus on patients' quality of life, the results of only one study demonstrated a statistically significant improvement in Tinnitus Handicap Inventory (THI) scores at four months follow-up (defined as a 'partial improvement' by the study authors (THI reduction of 21% to 80%)) when low-frequency rTMS was compared with a sham control treatment. However, no statistically significant improvement was demonstrated by another two studies that considered rTMS at the same frequency. Furthermore, this single positive finding should be taken in the context of the many different variables which were recorded at many different points in time by the study authors.In accordance with our pre-specified subgroup analysis we extracted the data from one study to consider the differential effectiveness between 'lower' low-frequency rTMS (1 Hz) and 'higher' low-frequency rTMS (10 Hz, 25 Hz). In doing this we were able to demonstrate a statistically significant difference between rTMS employing a frequency of 1 Hz and the sham group when considering tinnitus severity and disability after four months follow-up ('partial' improvement). However, no statistically significant difference was demonstrated between 10 Hz and 25 Hz rTMS, and the sham control group, when considering the severity and disability of tinnitus at four months follow-up.When considering tinnitus loudness in patients undergoing rTMS we were able to demonstrate a statistically significant reduction in tinnitus loudness when the results of two studies were pooled (risk ratio 4.17, 95% confidence interval 1.30 to 13.40). However, this finding was based on two small trials and consequently the confidence interval was particularly wide.No serious adverse effects were reported in any of the trials.

AUTHORS' CONCLUSIONS

There is very limited support for the use of low-frequency rTMS for the treatment of patients with tinnitus. When considering the impact of tinnitus on patients' quality of life, support is from a single study with a low risk of bias based on a single outcome measure at a single point in time. When considering the impact on tinnitus loudness, this is based on the analysis of pooled data with a large confidence interval.Studies suggest that rTMS is a safe treatment for tinnitus in the short-term, however there were insufficient data to provide any support for the safety of this treatment in the long-term.More prospective, randomised, placebo-controlled, double-blind studies with large sample sizes are needed to confirm the effectiveness of rTMS for tinnitus patients. Uniform, validated, tinnitus-specific questionnaires and measurement scales should be used in future studies.

Sound therapy (masking) in the management of tinnitus in adults

BACKGROUND

Tinnitus is described as the perception of sound or noise in the absence of real acoustic stimulation. Numerous management strategies have been tried for this potentially debilitating, heterogeneous symptom. External noise has been used as a management tool for tinnitus, in different capacities and with different philosophical intent, for over a century.

OBJECTIVES

To assess the effectiveness of sound-creating devices (including hearing aids) in the management of tinnitus in adults. Primary outcome measures were changes in the loudness or severity of tinnitus and/or impact on quality of life. Secondary outcome measures were change in pure-tone auditory thresholds and adverse effects of treatment. 

SEARCH STRATEGY

We searched the Cochrane ENT Group Trials Register; CENTRAL (2009, Issue 3); PubMed; EMBASE; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; mRCT and additional sources for published and unpublished trials. The date of the most recent search was 11 September 2009.

SELECTION CRITERIA

Prospective randomised controlled trials recruiting adults with persistent, distressing, subjective tinnitus of any aetiology in which the management strategy included maskers, noise-generating device and/or hearing aids, used either as the sole management tool or in combination with other strategies, including counselling.

DATA COLLECTION AND ANALYSIS

Two authors independently examined the 362 search results to identify studies for inclusion in the review, of which 33 were potentially relevant. Both authors extracted data independently.

MAIN RESULTS

Six trials (553 participants) are included in this review. Studies were varied in design, with significant heterogeneity in the evaluation of subjective tinnitus perception, with different scores, scales, tests and questionnaires as well as variance in the outcome measures used to assess the improvement in tinnitus sensation/quality of life. This precluded meta-analysis of the data. There was no long-term follow up. We assessed the risk of bias as medium in three and high in three studies. No side effects or significant morbidity were reported from the use of sound-creating devices.

AUTHORS' CONCLUSIONS

The limited data from the included studies failed to show strong evidence of the efficacy of sound therapy in tinnitus management. The absence of conclusive evidence should not be interpreted as evidence of lack of effectiveness. The lack of quality research in this area, in addition to the common use of combined approaches (hearing therapy plus counselling) in the management of tinnitus are, in part, responsible for the lack of conclusive evidence. Other combined forms of management, such as Tinnitus Retraining Therapy, have been subject to a Cochrane Review. Optimal management may involve multiple strategies.

Cognitive behavioural therapy for tinnitus

BACKGROUND

This is an update of a Cochrane Review originally published in Issue 1, 2007 of The Cochrane Library.Tinnitus is an auditory perception that can be described as the experience of sound, in the ear or in the head, in the absence of external acoustic stimulation. Cognitive behavioural therapy (CBT) uses relaxation, cognitive restructuring of the thoughts and exposure to exacerbating situations in order to promote habituation and may benefit tinnitus patients, as may the treatment of associated psychological conditions.

OBJECTIVES

To assess whether CBT is effective in the management of patients suffering from tinnitus.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; PsycINFO; ISRCTN and additional sources for published and unpublished trials. The date of the most recent search was 6 May 2010.

SELECTION CRITERIA

Randomised controlled trials in which patients with unilateral or bilateral tinnitus as their main symptom received cognitive behavioural treatment.

DATA COLLECTION AND ANALYSIS

One review author (PMD) assessed every report identified by the search strategy. Three authors (PMD, AW and MT) assessed the methodological quality and applied inclusion/exclusion criteria. Two authors (PMD and RP) extracted data and conducted the meta-analysis. The four authors contributed to the final text of the review.

MAIN RESULTS

Eight trials comprising 468 participants were included.For the primary outcome of subjective tinnitus loudness we found no evidence of a difference between CBT and no treatment or another intervention (yoga, education and 'minimal contact - education').In the secondary outcomes we found evidence that quality of life scores were improved in participants who had tinnitus when comparing CBT to no treatment or another intervention (education and 'minimal contact education'). We also found evidence that depression scores improved when comparing CBT to no treatment. We found no evidence of benefit in depression scores when comparing CBT to other treatments (yoga, education and 'minimal contact - education').There were no adverse/side effects reported in any trial.

AUTHORS' CONCLUSIONS

In six studies we found no evidence of a significant difference in the subjective loudness of tinnitus.However, we found a significant improvement in depression score (in six studies) and quality of life (decrease of global tinnitus severity) in another five studies, suggesting that CBT has a positive effect on the management of tinnitus.

Tinnitus Retraining Therapy (TRT) for tinnitus

BACKGROUND

Tinnitus is described as the perception of sound or noise in the absence of real acoustic stimulation. Although an outright cure for tinnitus remains elusive, various management strategies have been developed to help to lessen the impact of the symptom. Following the publication of a neurophysiological model of tinnitus, Tinnitus Retraining Therapy (TRT) was developed. Using a combination of directive counselling and sound therapy in a strict framework, this is one of the most commonly used treatment modalities for tinnitus. Many studies refer to the use of TRT where in fact a modified version of this therapy is actually being implemented. It is therefore important to confirm the use of authentic TRT when reviewing any study that reports its use.

OBJECTIVES

To assess the efficacy of TRT in the treatment of tinnitus.

SEARCH STRATEGY

The search included the Cochrane ENT Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, EMBASE and reference lists of identified publications. The date of the most recent search was 26 August 2009.

SELECTION CRITERIA

Randomised controlled trials of TRT versus no treatment, or other forms of treatment, in adult patients with tinnitus.

DATA COLLECTION AND ANALYSIS

Both authors critically appraised the retrieved studies for risk of bias and extracted data independently. Where necessary, we contacted the original study authors for further information.

MAIN RESULTS

Only one trial (123 participants) was included in the review. Several excluded trials did not follow the strict protocol for TRT, evaluating instead a modified form of TRT. The included trial showed TRT to be more effective than a tinnitus masking (TM) approach. In this study outcome data for tinnitus severity were presented using three instruments (Tinnitus Handicap Inventory (THI), Tinnitus Handicap Questionnaire (THQ), Tinnitus Severity Index (TSI)) for patients in three groups (participants' tinnitus being a 'moderate problem', big problem' or 'very big problem').At 18 months, improvements for the three groups in the three scores (TRT versus TM) were respectively: 'moderate problem' - THI: 18.2 versus 4.6, THQ: 489 versus 178, TSI 7.5 versus 1.6; 'big problem' - THI: 29.2 versus 16.7, THQ: 799 versus 256, TSI: 12.1 versus 6.7; and 'very big problem' - THI: 50.4 versus 10.3, THQ; 1118 versus 300, TSI: 19.7 versus 4.8.

AUTHORS' CONCLUSIONS

A single, low-quality randomised controlled trial suggests that TRT is much more effective as a treatment for patients with tinnitus than tinnitus masking.

Up-regulation of prestin mRNA expression in the organs of Corti of guinea pigs and rats following unilateral impulse noise exposure

Prestin is the motor protein of the outer hair cells (OHCs) and is required for both their electromotility and for cochlear amplification. We investigated the prestin mRNA expression in guinea pigs and rats in relation to the degree of noise-induced hearing loss (NIHL) induced by unilateral impulse noise exposure (167dB peak SPL) for 2.5-5 min. Distortion product otoacoustic emissions (DPOAE) and auditory brainstem responses were recorded before and one week post exposure. Prestin mRNA was examined by quantitative reverse transcription-polymerase chain reaction. Either the whole organs of Corti or the apical, middle and basal parts were examined separately. The specimens were pooled and grouped according to the degree of NIHL measured in the exposed ears. In rats, the number of hair cells was counted. A clear base-to-apex gradient in the prestin mRNA expression was found to exist in guinea pig and rat controls. In both species, there was an increase in the number of prestin RNA transcripts at a mean NIHL of about 15-25 dB indicating an up-regulation in the remaining intact cells. In rats, this degree of NIHL corresponded to an OHC loss of about 40%. Interestingly, the contralateral ears also revealed an up-regulation of prestin mRNA accompanied by significant DPOAE improvements.

Occipital condyle fracture: An unusual airbag injury

The installation of airbags in motor vehicles, in association with the use of seat belts, has reduced the incidence of head injuries, as well as significantly decreasing morbidity and mortality in motor vehicle accidents. Nevertheless, the literature on the subject increasingly refers to lesions related to airbag deployment. These are usually minor, but in certain circumstances, severe and fatal injuries can result. This is a case report of serious injury due to airbag deployment, involving a restrained driver who suffered occipital condylar injury when his airbag deployed in a frontal collision. The range of airbag associated injuries is reported and predisposing factors, such as the probable proximity to the airbag housing, is discussed.

Cognitive behavioural therapy for tinnitus

BACKGROUND

Tinnitus is an auditory perception that can be described as the experience of sound, in the ear or in the head, in the absence of external acoustic stimulation (not usually audible to anyone else). At present no specific therapy for tinnitus is acknowledged to be satisfactory in all patients. Cognitive behavioural therapy (CBT) uses relaxation, cognitive restructuring of the thoughts and exposure to exacerbating situations in order to promote habituation and may benefit tinnitus patients, as may the treatment of associated psychological conditions.

OBJECTIVES

To assess whether cognitive behavioural therapy is effective in the management of patients suffering from tinnitus.

SEARCH STRATEGY

Our search included the Cochrane ENT Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 2, 2006), MEDLINE and EMBASE. The last search date was June 2006.

SELECTION CRITERIA

Randomised controlled trials in which patients with unilateral or bilateral tinnitus as main symptom received cognitive behavioural treatment.

DATA COLLECTION AND ANALYSIS

One review author (PMD) assessed every report identified by the search strategy. The four review authors assessed the methodological quality, applied inclusion/exclusion criteria and extracted data.

MAIN RESULTS

Six trials comprising 285 participants were included. 1.

PRIMARY OUTCOME

subjective tinnitus loudness. CBT compared to a waiting list control group: we found no significant difference (Standardised Mean Difference (SMD) 0.06 (95% CI -0.25 to 0.37)). CBT compared to another intervention (Yoga, Education, Minimal Contact - Education and Education): we found no significant difference (SMD 0.1 (95% CI -0.22 to 0.42)).2.

SECONDARY OUTCOMES

a) Depression. CBT compared to a waiting list control group: we found no significant difference in either group (SMD 0.29 (95%CI -0.04 to 0.63)). CBT compared to another intervention (Yoga, Education and Minimal Contact - Education): we found no significant difference (SMD 0.01 (95% CI -0.43 to 0.45)). b) Quality of life: CBT compared to a waiting list control group: we found a significant difference in favour of CBT versus the waiting list group (SMD 0.7 (95% CI 0.33 to 1.08)). CBT compared to another intervention (Education, Minimal Contact - Education and Education): we also found a significant difference between CBT and the other intervention control group (SMD 0.64 (95% CI 0.29 to 1.00)). There were no adverse/side effects reported in any trial.

AUTHORS' CONCLUSIONS

We did not find a significant difference in the subjective loudness of tinnitus, or in the associated depression. However we found a significant improvement in the quality of life (decrease of global tinnitus severity) of the participants, thus suggesting that cognitive behavioural therapy has an effect on the qualitative aspects of tinnitus and contributes positively to the management of tinnitus.

Acute hearing loss after airbag deployment

Hearing loss from airbag deployment after motor vehicle crashes has been documented multiple times in the adult population, but rarely in the pediatric population. We report a case of significant sensorineural hearing loss following airbag deployment in a pediatric patient who presented to the ED on the day of the crash. This report highlights the need for pediatric physicians to be aware of the potential of minor to significant hearing loss in patients who present for medical evaluation after airbag deployment in motor vehicle crashes and to be aware of the importance of follow-up in these children.

Ginkgo biloba for tinnitus

BACKGROUND

Tinnitus can be described as the perception of sound in the absence of external acoustic stimulation. At present no specific therapy for tinnitus is acknowledged to be satisfactory in all patients. There are a number of reports in the literature suggesting that Ginkgo biloba may be effective in the management of tinnitus. However, there also appears to be a strong placebo effect in tinnitus management.

OBJECTIVES

To assess the effect of Ginkgo biloba in patients who are troubled by tinnitus.

SEARCH STRATEGY

The Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library Issue 4 2003), MEDLINE (1966 - 2003), EMBASE (1974 - 2003), and reference lists of identified publications. Date of the most recent search was December 2003.

SELECTION CRITERIA

Adults (18 years and over) complaining of tinnitus. Adults with a primary complaint of cerebral insufficiency where tinnitus forms part of the syndrome.

DATA COLLECTION AND ANALYSIS

Both reviewers independently extracted data and assessed trials for quality.

MAIN RESULTS

Twelve trials were identified from the search as being relevant to the review. Ten trials were excluded on methodological grounds. No trials of tinnitus in cerebral insufficiency reached a satisfactory standard for inclusion in the review. There was no evidence that Ginkgo biloba was effective for the primary complaint of tinnitus. The incidence of side effects was small.

REVIEWERS' CONCLUSIONS

The limited evidence did not demonstrate that Ginkgo biloba was effective for tinnitus which is a primary complaint. There was no reliable evidence to address the question of Ginkgo biloba for tinnitus associated with cerebral insufficiency.

Effects of underwater sound exposure on neurological function and brain histology

To evaluate the safety of sonar exposure from a neurological perspective, the vulnerability of the central nervous system to underwater exposure with high-intensity, low-frequency sound (HI-LFS) was experimentally examined. Physiological, behavioral and histological parameters were measured in anesthetized, ventilated rats exposed to brief (5 min), underwater HI-LFS. Exposure to 180 dB sound pressure level (SPL) re 1 microPa at 150 Hz (n = 9) did not alter acute cardiovascular physiology (arterial blood pH, pO(2), pCO(2), heart rate, or mean arterial blood pressure) from that found in controls (n = 11). Rats exposed to either 180 dB SPL re 1 microPa at 150 Hz (n = 12) or 194 dB SPL re 1 microPa at 250 Hz (n = 12) exhibited normal cognitive function at 8 and 9 days after sound exposure. Evaluation of neurological motor function revealed a minor deficit 7 days after 180 dB SPL/150 Hz exposure that resolved by 14 days, and no deficits after 194 dB SPL/250 Hz exposure. No overt histological damage was detected in any group. These data suggest that underwater HI-LFS exposure may cause transient, mild motor dysfunction.

Expression of c-Fos and c-Myc and deposition of beta-APP in neurons in the adult rat brain as a result of exposure to short-lasting impulse noise

There is increasing evidence that impulse noise causes brain damage, but little is known about the mechanisms and extent of the response. Here, rat brains were investigated immunohistochemically for the expression of c-Fos, c-Myc, and beta-APP during the first 3 weeks postexposure to impulse noise of 198 or 202 dB. The expression of c-Fos and c-Myc increased at 2 h after exposure in neurons of the cerebral cortex, thalamus, and hippocampus, and this c-Fos immunoreactivity remained elevated for the entire observation period. The c-Myc immunoreactivity peaked at 18 h in both neurons and astrocytes but returned to control levels at 7 days. Abnormal deposition of beta-APP was evident within 6 h in the same brain regions. The beta-APP immunoreactivity was most prominent at 18 h and remained increased over the 21-day period assessed. The observed effects were similar to those described in humans following traumatic brain injury and in Alzheimer's disease. We conclude that impulse noise influences the brain in a fashion similar to that in cases with progressive CNS degeneration.

Exposure to short-lasting impulse noise causes microglial and astroglial cell activation in the adult rat brain

Exposure to impulse noise, i.e. pressure waves, is above a certain intensity, harmful to auditory function. Intense, short-lasting impulse noise of 198 or 202 dB affects the heavy subunit of neurofilament proteins in neuronal perikarya of the cerebral cortex and hippocampus. There was as well an increased expression of immediate early gene products and induction of neuronal apoptosis. Here, we show that this range of exposure also affects glial cells. We identified microglial cells with an antibody against the complement receptor type 3 (OX-42) and astrocytes with an antibody against the glial fibrillary acidic protein (GFAP). The pattern of damage included microglial activation as early as 2 h after exposure to 202 dB. The activation increased further at 18 h. There was a significant increase of the area occupied by microglial cells in the anterior and posterior hypothalamus and in the lateral septal nucleus. Astrogliosis was observed in the cerebral cortex, the dentate gyrus and in the pyramidal cell layers as well as in white matter of the hippocampus. Both the microglial and astrocytic reactivities remained at 21 days. Exposure to 198 dB, caused similar, but less prominent activation in both cell types.

Otologic injuries from airbag deployment

Airbags became available as an optional passive restraint system in motor vehicles in 1973. The National Highway Traffic Safety Administration mandated placement of driver and right passenger airbags in all passenger vehicles and light trucks beginning in model year 1997. An estimated 2.1 million airbags have been deployed from the late 1980s until the present. There have been several case reports of hearing loss after exposure to airbag deployments in drivers and passengers since 1995. Members of the American Academy of Otolaryngology-Head and Neck Surgery submitted case reports on 71 patients with otologic symptoms after airbag deployment.

Patterns of maxillofacial injuries as a function of automobile restraint use

OBJECTIVE

To determine the pattern and severity of maxillofacial injuries sustained in a motor vehicle accident (MVA) resulting from automobile restraint use.

DESIGN

Retrospective database review of patients injured in a MVA who were admitted to the level I trauma center at the University of Louisville Hospital in Louisville, Kentucky.

METHODS

Demographic data, drug and alcohol impairment screening, and comorbidity data were obtained from database searches of trauma records. Forty-four patients had an airbag deployed, 34 patients wore seat belts, and 94 patients were unrestrained. All maxillofacial Abbreviated Injury Scale (AIS) ratings were compared among the three groups.

RESULTS

Twenty-two of the 44 patients (50%) in the airbag group sustained only facial injuries. Fifteen of them had lacerations; four others had only facial abrasions. Three of the airbag patients had moderate facial injuries (AIS = 2); none required operative management. The airbag group had a mean AIS rating of 1.13, the seat belt group a mean AIS of 1.29, and the unrestrained group a mean AIS of 1.46. Patients using either seat belts (mean age, 40.5 y) or airbags (mean age, 44.9 y) were older than the unrestrained group (mean age, 39.6 y). Drug and/or alcohol impairment was significantly greater in the unrestrained group (mean, 38%) compared with the seat belt group (mean, 26%) and the airbag group (mean 11%.).

CONCLUSIONS

Use of airbags is associated with less severe maxillofacial injuries compared with either a seat belt alone or no restraint. There is an inherent risk of minor maxillofacial injuries with airbag usage, but the severity of injury is distinctly reduced.

Hearing loss and automobile airbag deployments

In an on-going research program, on the causation of injuries in motor vehicle accidents, at the University of Michigan Transportation Research Institute, crashes with airbags have been, and are continuing to be, investigated. In order to determine the occurrence, if any, of 'hearing problems' associated with airbag deployments, drivers and passengers who had been involved in 'airbag' automobile crashes were interviewed by telephone. From the crashes investigated, 225 attempts were made to contact drivers who were exposed to airbag deployments. From these telephone interviews, contacts were made with 177 car occupants. Only three reported that they had experienced any type of hearing-related problems subsequent to their crash. One other case is reported of a driver who had pre-crash hearing loss. It appears that permanent hearing deficit due to airbag deployment, both in cars with the steering wheel airbag alone, and in those with a passenger side airbag, is an infrequent event (1.7%) from the data of this study.

Otologic injuries caused by airbag deployment

Airbags are clearly successful at mitigating injury severity during motor vehicle accidents. Deployment unfortunately has introduced new injury-causing mechanisms. A retrospective review of 20 patients who sustained otologic injuries resulting from airbag inflation was conducted. The most common symptoms were hearing loss in 17 (85%) and tinnitus in 17 (85%). Objective hearing loss was documented in 21 of 24 (88%) subjectively affected ears; this included unilateral and bilateral sensorineural, unilateral conductive, and mixed hearing losses. Ten patients (50%) had dysequilibrium. Four subjects (20%) had a tympanic membrane perforation; each required surgical closure. Ear orientation toward the airbag was found to be associated with hearing loss (P = 0.027), aural fullness (P = 0.039), and tympanic membrane perforation (P = 0.0004). A wide variety of airbag-induced otologic injuries occur and may have long-term sequelae. It is important for health care personnel to be aware of these potential problems.