J Accid Emerg Med: first published as 10.1136/emj.12.3.194 on 1 September 1995. Downloaded from Journal of Accident and Bomb blast to the : The London Bridge Emergency incident series Medicine 1995 12,194-198 R.M. WALSH,1 J.P. PRACY,1 A.M. HUGGON2 & M.J. GLEESON'

'Department of Otolaryngology - Head and Neck Surgery and 2Department of Accident and Emergency Medicine, Guy's Hospital, London, UK

which results in a massive increase in volume and SUMMARY consequently of pressure. The pressure wave Twelve patients who were treated for ear injuries spreads out from the site of the explosion and has at Guy's Hospital following the London Bridge three components: (1) a shock front which is bomb blast in February 1992 were reviewed. irregular in nature; (2) a positive pressure wave Among three there were four perforated , which lasts for 5-1 Oms and reaches an amplitude two of which closed spontaneously (50%). All of hundreds to thousands of kilograms cm-2; and three patients had a persistent mixed . (3) a long negative phase which lasts for The remaining nine patients had acute approximately 30ms and is never greater than sensorineural hearing loss and/or only. atmospheric pressure. The form of a charac- Four of these had resolved completely by 4h, teristic blast wave is known as the Friedlander another one by 48h, and two by 4 weeks. Two curve (Fig. 1). patients had a residual high frequency hearing The effects of blast on the ear have been loss. In total, five patients (42%) have a persistent described in detail by Kerr & Byrne.2-4 They hearing loss. None of the patients suffered from reported that the inner ear is more frequently balance problems. affected than the . A temporary In summary, the ear is very susceptible to bomb threshold shift of hearing acuity is common, often blast , but there is a high rate of spontaneous initially quite severe, but usually only transient. closure of perforations and improvement of Tinnitus is the most frequently reported ear sensorineural hearing loss and tinnitus. symptom, and its recovery tends to parallel that of Keywords: blast injury, sensorineural hearing hearing loss. Balance problems are rare. Tympanic loss membrane perforations are common in those near http://emj.bmj.com/ to the explosion. These tend to close spontaneously; closure rates of > 80% have been INTRODUCTION reported.2 The ear is the most sensitive organ in the body to We report this series of patients who sustained the effects of blast. The first case of deafness due bomb blast injuries to their because such are more common in to blast injury was reported by Green in 1872.1 A incidents becoming present- on September 29, 2021 by guest. Protected copyright. blast wave is the consequence of an explosive day society, and a review of their management rapidly changing from a solid to a gaseous state, would seem to be overdue.

...... Correspondence: .... R.M. Walsh,

..... ENT Registrar, t ......

g- r n ;:i? M Department of ...... Otolaryngology -

PqObbu ...... Head and Neck ......

Surgery, Guy's ...... Hospital, St Thomas L 10 20 25 30 35 St, London SE1 9RT, 0 6 15 Fig. 1. Pressure profile of a blast UK Time (mgs) wave (Friedlander curve). © 1995 Blackwell Science Ltd J Accid Emerg Med: first published as 10.1136/emj.12.3.194 on 1 September 1995. Downloaded from Bomb blast months and 1 year, respectively, after the SUBJECTS AND RESULTS injuries to the ear explosion. These findings were confirmed by pure A total of 30 patients were seen in the Accident tone audiometry. The air conduction (AC) threshold and Emergency Department at Guy's Hospital, at 8 KHz is used to illustrate those patients with a London on the morning of 28 February 1992 high frequency sensorineural element to their following a bomb explosion on a crowded plafform hearing loss (Table 3). at London Bridge railway station. Twelve of these Three patients had perforated eardrums. In one patients suffered otological injuries, the details of patient both eardrums were perforated, while in the which are summarized in Table 1. other two the perforations were unilateral. Each of All patients underwent a thorough otological these patients underwent suction clearance of any history and examination, including tuning fork debris within the external auditory canal with the tests. None of them had a previous history of aid of a microscope, and avoidance of water was hearing problems. All 12 patients presented with advised. Topical antibiotics were not required, as hearing loss or tinnitus, and none of the patients there were no cases of . The perforations had vestibular symptoms. Nine patients had were managed conservatively over the ensuing 6 symptoms suggestive of cochlear damage, i.e. months. The bilateral perforations closed hearing loss and/or tinnitus. Examination of the spontaneously within 6 months, but this patient has tympanic membrane in these patients was normal. a persistent mild bilateral mixed (conductive and Four of these patients were discharged after 4 h of sensorineural) hearing loss and tinnitus. One patient observation as their auditory symptoms had with a subtotal unilateral perforation was treated resolved completely (Table 2). The remaining five successfully by a after 9 months as patients were followed up as out-patients in the it had failed to heal spontaneously. The final patient Otolaryngology Department because of persistent with a unilateral perforation refused surgery and still hearing loss/tinnitus and abnormal tuning fork has a persistent bilateral hearing loss. The difference tests. All five patients were managed between the air conduction and bone conduction conservatively. The symptoms resolved completely thresholds (AB) indicates those patients with a within 48h in one patient, and within 4 weeks in conductive element to their hearing loss (Table 3). two others, but in two patients a residual bilateral In total, five of the 12 patients (42%) had a high frequency hearing loss was present at 8 persistent hearing loss 6 months to 1 year after

Table 1. Presenting features http://emj.bmj.com/ No. Age Sex Presenting symptoms Presenting signs (years)

1 38 M Bilateral hearing loss, Bilateral subtotal perforations bilateral tinnitus 2 47 M Right hearing loss, Right subtotal perforation right tinnitus on September 29, 2021 by guest. Protected copyright. 3 58 M Left hearing loss, Left central perforation left tinnitus 4 34 F Left hearing loss, None left tinnitus 5 62 M Right hearing loss, None right tinnitus 6 36 F Bilateral hearing loss, None bilateral tinnitus 7 22 M Right hearing loss, None right tinnitus 8 59 F Bilateral hearing loss, None bilateral tinnitus 9 26 M Bilateral tinnitus None 10 31 M Bilateral tinnitus None 11 27 M Right tinnitus None 12 38 F Bilateral hearing loss, None 195 bilateral tinnitus

1995 Blackwell Science Ltd, Journal of Accident and Emergency Medicine 12, 194-198 J Accid Emerg Med: first published as 10.1136/emj.12.3.194 on 1 September 1995. Downloaded from Table 2. Treatment and clinical R.M. Walsh et al. No. Treatment Resulting symptoms Resulting signs outcome 1 Conservative Bilateral hearing loss, Spontaneous closure bilateral tinnitus of both perforations 2 Right tympanoplasty Right hearing loss, Perforation closed right tinnitus 3 Conservative Left hearing loss, Permanent central (patient refused surgery) left tinnitus perforation 4 Conservative Resolved by 4 weeks None 5 Conservative Resolved by 4 weeks None 6 Conservative Bilateral hearing loss, None bilateral tinnitus 7 Conservative Resolved by 48 h None 8 Conservative Bilateral hearing loss, None bilateral tinnitus 9 Conservative Resolved by 4 h None 10 Conservative Resolved by 4 h None 11 Conservative Resolved by 4 h None 12 Conservative Resolved by 4 h None

the blast, of which two cases were entirely duration.67 All of these variables are directly sensorineural while the other three were mixed related to the nature and amount of the explosive.4 (conductive and sensorineural) in nature. Clearly, the distance of the ear from the explosion, the presence of obstructing objects and the DISCUSSION proximity of surrounding structures are also significant. Furthermore, the state of the Ruedi and Furrer5 classified airborne stimulation is relevant. Healed perforations are sites of deafness as three types: noise-induced deafness, potential weakness whereas report trauma and blast trauma. Noise-induced and thickening are comparatively strong. The deafness is acquired by prolonged exposure to tympanic membranes of young people seem to elevated sound intensities resulting in cochlear be more resistant to blast injury than those of the and it is most marked around 4 kHz. damage only, elderly.4 http://emj.bmj.com/ Report trauma is sustained by those exposed to The commonest effect of blast on the middle ear gunfire when the duration of the positive wave of is a . The perforation is usually the stimulus is less than 1.5 ms. In these cases, located in the antero-inferior part of the part tensa, middle ear damage is unusual and cochlear may be punched out, ragged, linear or multiple, damage is most marked at 4 kHz. In contrast, blast and is produced by the positive pressure wave. It

trauma results from a single stimulus whose has been estimated that the minimum pressure on September 29, 2021 by guest. Protected copyright. positive wave has a duration of more than 1.5 ms. needed to cause a perforation is 25 cmHg, whereas All of the frequencies may be affected, but damage considerably less is required to cause cochlear is most marked in the higher tones. Middle ear damage (7 cmHg.).8 Ossicular discontinuity has damage is more frequently sustained after blast only been reported in the presence of a perforated trauma than after report trauma, but cochlear eardrum. Debris from the blast may be driven into damage prevails in both. Disturbances of balance the external or middle ear and consequently are uncommon, regardless of the type of airborne introduce infection. Similarly, squamous epithelium stimulation deafness. can be implanted in the middle ear cleft and later The effects of blast on the ear result from a large form .1'9 positive pressure wave spreading out from the Kerr & Byrne2 studied the effects of a 5-pound centre of the explosion (Fig. 1). Several factors bomb blast in a crowded restaurant in 1972 on the determine the degree of damage sustained by the ears of 101 people. A total of 66 patients had ear, including the rise time, i.e. the speed with perforated eardrums, 55 (83%) of which healed which the positive pressure wave builds up, the spontaneously, in contrast with a 50% closure rate 196 amplitude of the positive pressure wave and its in our series. In their series, six out of seven

1995 Blackwell Science Ltd, Journal of Accident and Emergency Medicine 12, 194-198 Bomb blast J Accid Emerg Med: first published as 10.1136/emj.12.3.194 on 1 September 1995. Downloaded from Table 3. Audiological threshold data injuries to the ear Case Initial PTA (dB) Final PTA (dB) no. Delay R L Dekay R L 1 AB 1 month 20.0 17.5 6 months 10.0 10.0 AC 45.0 40.0 42.5 40.0 2 AB 4 months 17.5 0.0 14 months 10.0 0.0 AC 30.0 15.0 25.0 7.5 3 AB 2 months 0.0 20.0 18 months 0.0 17.5 AC 25.0 30.0 25.0 27.5 4 AB 1 months 0.0 0.0 NA NA NA AC 10.0 10.0 NA NA 5 AB 2 months 5.0 2.5 12 months 2.5 2.5 AC 35.0 10.0 10.0 10.0 6 AB 2 mouths 0.0 0.0 8 months 0.0 0.0 AC 50.0 47.5 50.0 45.0 7 AB 48 h 0.0 0.0 NA NA NA AC 20.0 10.0 NA NA 8 AB 1 month 5.0 2.5 12 months 5.0 2.5 AC 55.0 47.5 55.0 47.5 9 FTA NA NA FTA NA NA 10 FTA NA NA FTA NA NA 11 AB FTA NA NA 18months 0.0 0.0 AC NA NA 15.0 12.5 12 AB FTA NA NA 18 months 0.0 0.0 AB NA NA 10.0 7.5

AB: Difference between average air conduction and bone conduction thresholds at 50OHz,1 kHz, 2kHz and 4kHz. AC: Air conduction threshold at 8kHz. FTA: Failed to attend for examination NA: Not applicable

myringoplasties were successful, and no ossicular within 4 weeks. damage was reported. Kerr and Byrne2 described the histological There is no association between middle ear and effects of blast on the ear after microdissection of http://emj.bmj.com/ inner ear damage, and no evidence to suggest that the temporal bones of those killed by bomb blasts. dissipation of energy by a perforation of the These included rupture of the saccule, utricle and eardrum protects the inner ear. A temporary basilar membrane, the presence of squamous threshold shift is common, especially in those near epithelium in the middle ear and ruptured tympanic the blast. Recovery is often rapid (occurring within membranes. Ruedi and Furrer5 reported the hours to days), with a higher rate for the middle miscroscopic effects of blast on the inner ears of on September 29, 2021 by guest. Protected copyright. than the high frequencies, and it is complete in a guinea pigs. They found tears in Reissner's large proportion of patients.2 A significant number membrane and the basilar membrane in the basal of patients, while asymptomatic, are left with a mild coil, with hair cell damage over long stretches of persistent high-frequency sensorineural hearing the organ of Corti. loss as shown by pure tone audiometry. Kerr and Tinnitus is the commonest ear symptom after a Byrne2 reported that 100% of people in their series bomb blast, and is universal in both series. Its pitch had some degree of temporary hearing loss and/ depends on the frequency of the hearing loss, and or tinnitus, 30% had persistent high-frequency recovery parallels the restoration of hearing. deafness greater than 30 dB, 17% had persistent Balance disorders are exceptionally uncommon. deafness over all of the frequencies and 5% had If present, they are probably secondary to an bilateral deafness greater than 40 dB affecting the associated . However, a few cases of entire frequency range. Similarly, in our series, all benign positional paroxysmal have been patients had some degree of initial hearing loss described in the absence of a history of head 197 and/or tinnitus, and 58% had reverted to normal injury.4

1995 Blackwell Science Ltd, Journal ofAccident and Emergency Medicine 12, 194-198 R.M. Walsh et al. The management of these patients is relatively REFERENCES J Accid Emerg Med: first published as 10.1136/emj.12.3.194 on 1 September 1995. Downloaded from A and straightforward. thorough otological history 1. Geen J.O. (1872) Cases of injury to the ear from examination, including tuning fork testing, should external violence. Transactions of The American be undertaken. All patients should be referred to Otological Society 5, 88-98. the ENT department within 24 h so that audiometry 2. Kerr A.G. & Byrne J.E.T. (1975) Concussive effects and, where appropriate, microscopic suction of bomb blast on the ear. Journal of Laryngology clearance can be performed. Sensorineural and 89, 131-143. hearing loss and tinnitus undergo rapid early 3. Kerr A.G. (1980) Trauma and the temporal bone: the spontaneous resolution, and therefore effects of blast on the ear. Journal of Laryngology reassurance is appropriate. and Otology 94, 107-110. It is unlikely that any treatment influences the 4. Kerr A.G. (1987) Blast injury to the ear: a review. course of sensorineural deafness, but Kerr4 Reviews on Environmental Health 7, 65-79. L. & Furrer W. (1947) Das Akustische Trauma. prescribes corticosteroids to those with severe 5. Ruedi S. Karger, Basle. airborne stimulation deafness on an empirical 6. White C.S. (1961). Biological effects of blast basis. Any debris in the external ear canal should Technical Progress Report. Defense Atomic Support be removed by suction clearance under the Agency, No 1271, 1-50. Lovelace Foundation for microscope in the ENT Department. In view of the Medical Education and Research, Alberquerque, high spontaneous closure rate of perforated New Mexico. eardrums, immediate surgery is not recommended, 7. White C.S., Bowen l.G., & Richmond D.R. (1965) and patients should be reassured of this fact. A Biological Tolerance to Air Blast and Related tympanoplasty is indicated for any perforation that Biomedical Criteria. United States Atomic Energy has failed to close within 6 months. Comission Civil Effects Test Operations Report No. Prophylaxis should always be considered when 65.4, 1-239. Lovelace Foundation for Medical bomb blast exposure is expected. Ear muffs and Education and Research, Alberquerque, New Mexico. plugs afford protection but restrict communication. 8. Hirsch F.G. (1968) Effects of over-pressure on the ear - a review. Annals of the New York Academy of Gundefender® ear plugs'° offer considerable Sciences 152, 147-162. protection and at the same time maintain almost 9. Seaman R.W. & Newell R.C. (1971) Another aetiology normal hearing. This is effected by a small of middle ear cholesteatoma. Archives of perforation in a metal disc embedded in rubber Otolaryngology 94, 440. which allows the passage of speech sounds but 10. Coles R.R.A. (1970) Recent developments in ear impedes the blast wave. protection. Proceedings of the Royal Society of In conclusion, although the ear is exquisitely Medicine 63, 1016. http://emj.bmj.com/ sensitive to the effects of blast, spontaneous recovery from acquired sensorineural hearing loss, tinnitus and tympanic membrane perforations can be expected in the majority of cases.

ACKNOWLEDGEMENTS on September 29, 2021 by guest. Protected copyright. The material in this paper was presented at the Accident and Emergency Symposium, Guy's Hospital, London, on 11 December 1992.

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