severe skin and soft tissue infections of the head and neck are rare conditions that may emerge secondarily to oropharyngeal infections . anaerobic bacteria are often involved and may contribute to extensive inflammation , necrosis , and abscess formation . secondary focal complications as bacterial invasion of vasculature , venous or arterial septic embolisation to the brain , spine or thorax may appear . lemierre 's syndrome ( ls ) is a manifestation with anaerobic aetiology and septic thrombophlebitis of the internal jugular vein . cervicocranial necrotizing fasciitis ( cnf ) is a more superficial infection , and descending necrotizing mediastinitis ( dnm ) is a deep manifestation of this group of diseases . broad - spectrum antibiotics are the basis of treatment , and early surgery is often necessary , especially in nf and dnm . the role of adjuvant treatment with hyperbaric oxygen ( hbot ) in these conditions is controversial . especially for infections with anaerobic microbes , other than in knowledge of the possible benefit of adjuvant treatment is important for this group of patients . here we present three cases with definite or probable involvement of anaerobic bacteria , where hbo was used with a favourable outcome . a 67-year - old man in previously good condition , experienced a sore throat and dysphagia for 5 days . on admission to hospital temperature was 38,1c , heart rate ( hr ) 125/min , blood pressure ( bp ) 110/59 mm hg , respiratory rate ( rr ) 30/min , and sa02 87% with 12 l 02/min supplement via a nonrebreather mask . on clinical examination the neck was asymmetric with an enlarged mass on the left side , and crepitus was felt by palpation . a ct - scan demonstrated soft tissue swelling , subcutaneous gas ( figure 2 ) , and a muscle abscess in the neck . antibiotic treatment was initiated , and he had to undergo immediate surgery with drainage of the abscess . mixed anaerobic microbes were identified ( table 1 ) . due to the foci of infection , gas - production in the tissue and positive cultures for anaerobic bacteria , it was decided to start with hyperbaric oxygen treatment ( hbot ) for 90 min sequences at 3 atmosphere absolute ( ata ) . hbot at 3 ata was chosen based on the recommendation for treatment of clostridial myonecrosis from undersea and hyperbaric medical society ( uhms ) . a total of 5 hbot were performed in the next 2.5 days , the first starting a few hours after the initial surgery . already after 3 hbots the surgeon reported a halt of the ongoing necrotizing infection in the area . after 5 hbots the patients condition was reported to be under control and stabilized , and hbot was discontinued . during hbo - treatment the sequential organ failure assessment ( sofa ) score decreased from 12 to 5 , and vasopressor was ceased ( figure 1 ) . although the condition improved , another ct - scan of the neck and chest demonstrated thrombosis of the left jugular vein and an additional abscess in the upper mediastinum . after 27 days in the icu , the patient was transferred to the medical ward , were he stayed another 36 days before he was discharged from hospital to home . changes in c - reactive protein (  , mg / l ) , procalcitonin (  , g / l * 100 ) and sequential organ failure assessment -score * 10 (  ) during the first twelve days in hospital . the hyperbaric oxygen treatment period is marked . crp , c - reactive protein ; pct , procalcitonin ; sofa , sequential organ failure assessment ; hbo , hyperbaric oxygen . changes in c - reactive protein (  , mg / l ) , procalcitonin (  , g / l * 100 ) and sequential organ failure assessment -score * 10 (  ) during the first twelve days in hospital . the hyperbaric oxygen treatment period is marked . crp , c - reactive protein ; pct , procalcitonin ; sofa , sequential organ failure assessment ; hbo , hyperbaric oxygen . figure 2computed tomography scan of thorax , showing loculaments of air in the tissue of the mediastinum ( white arrows ) in patient # 1 . computed tomography scan of thorax , showing loculaments of air in the tissue of the mediastinum ( white arrows ) in patient # 1 . 
 table 1clinical data of patient # 1 and # 2.localizationdetection methodmicrobepatient # 1blood cultureculture / v3-v4 sequencingcampylobacter species ( rectus / showae)anaerobic blood culturemicroscopygram positive coccusneckculturepeptostreptococcus anaerobius , propionibacterium acnesmediastinumv1-v3 , group specific primers*parvimonas spp . , treponema denticola , prevotella dentalis , prevotella biviamediastinumv3 v4 sequencing*porphyromonas gingivalis , bacteriodes species ( parabecteriodes goldsteinii)patient # 2tonsilsmicroscopyfusiform gram negative rodsculturehaemophilus parainfluenzae , streptococcus viridans 
 aggregatibacter aphrophilus , group b streptococcus , mediastinum , tonsilsculturestreptococcus milleri , prevotella speciesmediastinumculturepeptostreptococcus species*used ripseq software a healthy 53 year old man with psoriatic disease experienced 6 days of sore throat . due to sudden onset of chest pain a coronary event was suspected . on admittance to hospital he was in reduced general state with a temperature of 37 , 3c , hr 90/min , a ct - scan of neck and chest showed inflammation of the upper and lower mediastinum , involving the pericardium , and gas was seen in deep tissue layers . figure 3computed tomography scan of thorax , showing loculaments of air in the tissue of the mediastinum ( black arrow ) in patient # 2 . computed tomography scan of thorax , showing loculaments of air in the tissue of the mediastinum ( black arrow ) in patient # 2 . it was decided to treat the surgical wound with vacuum assisted closure ( vac ) , and initially not by hbot . however , over the next 5 days his condition did not improve , a ct - scan demonstrated bilateral empyema , significant inflammation in soft tissue of the neck and mediastinum , and gas surrounding the heart . due to the foci of infection , gas - production in the tissue and identification of anaerobic pathogens , he underwent a total of 5 hbo - treatments the next 3 days , as described in case 1 . upon hbot , the patient improved , vasopressors were ceased , and crp decreased from 285 to 116 mg / l ( figure 4 ) . four days after the last hbo - treatment his sternum was closed . after a total of 21 days in icu he was discharged to the ear - nose - and throat ward ( ent ) . changes in c - reactive protein (  , mg / l ) , procalcitonin (  , g / l * 100 ) and and sequential organ failure assessment -score * 10 (  ) during the first 16 days in hospital . the hyperbaric oxygen treatment period is marked . hbo , hyperbaric oxygen ; crp , c - reactive protein ; pct , procalcitonin ; sofa , sequential organ failure assessment . changes in c - reactive protein (  , mg / l ) , procalcitonin (  , g / l * 100 ) and and sequential organ failure assessment -score * 10 (  ) during the first 16 days in hospital . the hyperbaric oxygen treatment period is marked . hbo , hyperbaric oxygen ; crp , c - reactive protein ; pct , procalcitonin ; sofa , sequential organ failure assessment . a previously healthy woman , age 22 , had a history of 6 days with progressive dysphagia . she was admitted to the local hospital due to increasing systemic signs of infection , accompanied by tenderness of the neck and chest pain . she received treatment with antibiotics for one day , before she was transferred to the regional hospital . distinct tenderness on the left side of the neck was found , as well as discrete oedema . on inspection of the oropharynx , slight elevation of the left side of the lateral pharyngeal wall was seen . laboratory results are given in figure 5 . a new ct - scan and an mri confirmed the findings of inflammatory changes in the neck as well as an mediastinal abscess , together with thromboses of the left jugular and subclavian veins . the abscess was not suited for surgical drainage due to difficult access ; small volume and density measured by ct . she was treated with antibiotics and lmhw in the infectious diseases ward . in an attempt to reduce further progression of inflammation and pus formation , hbot was started ( 3 ata , 90 min ) whereby the patient 's condition improved shortly after this treatment was introduced ( figure 5 ) . three days after discontinuation of hbot she was transferred to her local hospital for further conservative measures . after two weeks she was discharged from the local hospital , where treatment was continued with antibiotics for another 2 weeks and anticoagulation for 3 months . changes in c - reactive protein (  , mg / l ) and , sequential organ failure assessment -score * 10 (  ) during the first 13 days in hospital . the hyperbaric oxygen treatment period is marked . hbo , hyperbaric oxygen ; crp , c - reactive protein ; sofa , sequential organ failure assessment . changes in c - reactive protein (  , mg / l ) and , sequential organ failure assessment -score * 10 (  ) during the first 13 days in hospital . the hyperbaric oxygen treatment period is marked . hbo , hyperbaric oxygen ; crp , c - reactive protein ; sofa , sequential organ failure assessment . in each of these three cases we diagnosed the patient with an extensive soft - tissue infection of the neck and mediastinum . patient # 1 and # 3 met the criteria for lemierre 's syndrome , and patient # 2 had findings consistent with dnm . in patient # 1 and # 2 several bacteria were identified with an oropharyngeal origin . both anaerobic and aerobic bacteria were probably involved in the disease of these two patients . anaerobic involvement was probable also the case in patient # 3 , as crepitations in the skin were found under clinical examination . the contribution of hbot to the recovery of each patient will be discussed in the following . descending necrotizing infections of the head and neck are rare and the case fatality rate is high . severe infections of the head and neck often start with symptoms from the source of infection . in lemierre 's syndrome sore throat and neck pain the origin is often a pharyngotonsillitis or a peritonsillar abscess . in cnf , dysphagia and a sore throat a dental infection is often the primary source of infection in dnm , pharyngeal infection is most often the primary source . in our three cases , all presented with a history of sore throat and dysphagia . the two patients with lemierre 's syndrome both had oropharyngeal infections with downward spread of infection to the mediastinum . in lemierre 's syndrome the spread is usually metastatic from the thrombophlebitis of the affected vein . in dnm the spread is probably facilitated by gravity , breathing and negative intrathoracic pressure . the systemic effects predominate when the mediastinum becomes more involved ; capillary leak , possible respiratory distress syndrome ( ards ) and empyema . the necrotizing infections described herein are typically polymicrobial , and anaerobic microbes normally harboured in the oral cavity are usually involved . all the tested bacteria were sensitive to penicillin g and are considered sensitive to the initial empiric therapy . however , the sub - optimal effect of antibiotics observed was most likely caused by local factors as impaired perfusion , oxygen depletion , impaired immunofunction or bacterial community mediated antibiotic tolerance mechanisms . strictly anaerobic microbes are easily killed during specimen transport and handling if anaerobic conditions are not maintained . , often considered the main bacteria causing lemierre 's syndrome , are extremely sensitive to o2 and can be missed by traditional culture methods . the usefulness of alternative techniques is illustrated in case 1 , where 16srdna detection identified in total 6 species that were not identified by conventional culture . 16srdna sequencing in mixed infections gives mixed chromatograms where overlying sequences make it difficult to identify which nucleic acid belong to which microbe . this was overcome by using the newly developed software ripseq that identified 2 microbes ( porphyromonas gingivalis and bacteroides spp . ) . the 16srdna sequencing , in this study targeted either or both of the variable gene regions v1-v3 and v3-v4 . using group specific primers and ripseq we were able to identify an additional 4 microbes . such detection methods based on genus / species specific nucleic acids are particularly useful in infections caused by fastidious and oxygen sensitive bacteria . earlier only infections caused by a single bacterial species could be detected by 16 rdna sequencing , but by using group specific primers and rip seq software this can be accomplished also for polymicrobial infections , even after antimicrobial therapy is started , as illustrated in this case report . patient # 1 and # 2 were treated in a multiplace - chamber due their need of intensive care and respirator ( haux - quadro 2500 - 2200 ) . in patient # 1 , an improvement in the clinical condition was objectively observed after three hbots . he received two additional treatments , and his clinical condition further improved , objectively observed by marked reduction of the sofa - score ( figure 1 ) . however , his condition worsened a few days later , and an abscess in the mediastinum was found and removed by drainage . one might argue a need for additional hbot in this patient , but this was not done . however , his clinical condition worsened and it was not until the start of hbot at day 5 one was able to get control over his infection and his condition stabilized . this patient was treated in a monoplace - chamber ( baramed hyperbaric chambers , etc ) . the use of hbot in conjunction with surgical debridement , antibiotic therapy and maximal critical - care therapy for severe soft tissue infections is widely accepted , but the efficacy of hbo remains unproven . in soft tissue infections , an area of hypoxia develops . the hypoxia impairs phagocytosis , and the drop in ph creates a milieu for growth of anaerobic organisms . gas is frequently seen in crepitant necrotizing infections , as described in our three cases . hbot provides oxygenation to otherwise ischemic areas , and reduces the impact of hypoxia on leukocyte function . hbot of infections also occurs via hbo acting as a bactericide or as a bacteristatic agent to some microorganisms , and through an additive and/or synergistic effect on some antimicrobial drugs . in patient # 1 the surgeon reported vital tissue only in the affected area , shortly after start of hbot which may illustrate its therapeutic potential . in all the cases , a clinical improvement was seen after the start of hbot , but the specific role of hbot in this improvement is difficult to estimate . the necrotizing infections described herein are typically polymicrobial , and anaerobic microbes normally harboured in the oral cavity are usually involved . all the tested bacteria were sensitive to penicillin g and are considered sensitive to the initial empiric therapy . however , the sub - optimal effect of antibiotics observed was most likely caused by local factors as impaired perfusion , oxygen depletion , impaired immunofunction or bacterial community mediated antibiotic tolerance mechanisms . strictly anaerobic microbes are easily killed during specimen transport and handling if anaerobic conditions are not maintained . , often considered the main bacteria causing lemierre 's syndrome , are extremely sensitive to o2 and can be missed by traditional culture methods . the usefulness of alternative techniques is illustrated in case 1 , where 16srdna detection identified in total 6 species that were not identified by conventional culture . 16srdna sequencing in mixed infections gives mixed chromatograms where overlying sequences make it difficult to identify which nucleic acid belong to which microbe . this was overcome by using the newly developed software ripseq that identified 2 microbes ( porphyromonas gingivalis and bacteroides spp . ) . the 16srdna sequencing , in this study targeted either or both of the variable gene regions v1-v3 and v3-v4 . using group specific primers and ripseq we were able to identify an additional 4 microbes . such detection methods based on genus / species specific nucleic acids are particularly useful in infections caused by fastidious and oxygen sensitive bacteria . earlier only infections caused by a single bacterial species could be detected by 16 rdna sequencing , but by using group specific primers and rip seq software this can be accomplished also for polymicrobial infections , even after antimicrobial therapy is started , as illustrated in this case report . patient # 1 and # 2 were treated in a multiplace - chamber due their need of intensive care and respirator ( haux - quadro 2500 - 2200 ) . in patient # 1 , an improvement in the clinical condition was objectively observed after three hbots . he received two additional treatments , and his clinical condition further improved , objectively observed by marked reduction of the sofa - score ( figure 1 ) . however , his condition worsened a few days later , and an abscess in the mediastinum was found and removed by drainage . one might argue a need for additional hbot in this patient , but this was not done . however , his clinical condition worsened and it was not until the start of hbot at day 5 one was able to get control over his infection and his condition stabilized . this patient was treated in a monoplace - chamber ( baramed hyperbaric chambers , etc ) . the use of hbot in conjunction with surgical debridement , antibiotic therapy and maximal critical - care therapy for severe soft tissue infections is widely accepted , but the efficacy of hbo remains unproven . in soft tissue infections , an area of hypoxia develops . the hypoxia impairs phagocytosis , and the drop in ph creates a milieu for growth of anaerobic organisms . gas is frequently seen in crepitant necrotizing infections , as described in our three cases . hbot provides oxygenation to otherwise ischemic areas , and reduces the impact of hypoxia on leukocyte function . hbot of infections also occurs via hbo acting as a bactericide or as a bacteristatic agent to some microorganisms , and through an additive and/or synergistic effect on some antimicrobial drugs . in patient # 1 the surgeon reported vital tissue only in the affected area , shortly after start of hbot which may illustrate its therapeutic potential . in all the cases , a clinical improvement was seen after the start of hbot , but the specific role of hbot in this improvement is difficult to estimate . data on hbot of such infections are scarce and not conclusive , but somewhat in support of this . recent availability of hbot with intensive care facilities at our hospital has led to three hbo treated cases all demonstrating a significant clinical improvement . we also show that hbot may be used on the basis of only strong clinical suspicion of anaerobic infection . the cases demonstrate that use of polymerase chain reaction is especially useful in the diagnostics of anaerobic infections . when hbot is available , it should be considered as adjunctive treatment in extensive infections with anaerobes , but more studies are needed to evaluate the effect .
necrotizing infections of the head and neck are rare conditions in our hospital . 
 clinical and microbiological characteristics of three consecutive cases treated in haukeland university hospital in western norway in the year 2010 are described . 
 two cases of lemierre 's syndrome and one case with a descending necrotizing mediastinitis ( dnm ) were diagnosed . 
 all three cases were treated with broad spectrum antibiotics and in two cases surgery was possible . 
 hyperbaric oxygen treatment ( hbot ) with intensive care facilities became recently available at our hospital , and this treatment was used in all these patients regardless of surgery . in one case 
 we describe the use of hbot on the basis of strong clinical suspicion of anaerobic infection only . 
 bacterial identification by partial sequencing of the 16srdna gene proved to be a useful supplement to conventional culture techniques . 
 all the cases all demonstrated a significant clinical improvement after introduction of hbot . 
 when hbot is available , it should be considered as adjunctive treatment in extensive infections with anaerobes .