Case Report Series: Clinical Analysis of Severe Deep Neck Space Infection

Background Severe deep neck space infection is rare and critical.The objective is to deepen the understanding of severe deep neck space infection and improve the level of clinical diagnosis and treatment. Case presentation A retrospective analysis of the diagnosis and treatment of 5 cases of serious deep neck infections admitted to our department. The 5 patients were all diagnosed by cervical CT and surgical exploration. 3 patients with diabetes, 2 patients with diabetic ketoacidosis, 3 patients with mediastinal infection; 3 patients underwent tracheotomy and 2 patients with tracheal intubation; All patients were treated by neck incision, drainage, dressing change and targeted antibiotics. Conclusions Severe deep neck infections are prone to occur in patients with diabetes and other systemic basic diseases. Early diagnosis, timely neck incision exploration, drainage to maintain airway patency and targeted antibiotic treatment are the keys to diagnosis and treatment.

fourth day of admission to the hospital, there was hyperemia and swelling in the suprathyroid cartilage in the middle of the neck, accompanied by laborious breathing. Neck CT showed soft tissue swelling with pneumatosis from left epiglottis to thyroid cartilage ( Fig. 1.c). Perform tracheotomy and neck incision exploration, see the formation of abscesses in the anterior epiglottic space between thyroid cartilage and hyoid bone, which were thick yellow pus with smelly.Further diagnosis: Abscess of deep neck space.

Case 4
Male, 62 years old.On June 24, 2019, He was admitted to the hospital because of " pharyngalgia, fever with dysphagia for 5 days, neck swelling and pain for 2 days", without history of diabetes and other basic diseases. Physical examination:T: 38.2 C, left laryngopharyngeal side wall swelling is obvious, epiglottis without hyperemia, swelling; bilateral upper neck swelling is obvious with tenderness. On the second day of admission, the neck swelling became worse, spreading to the upper sternum fossa, and there was a feeling of crepitus. Neck CT: The swelling of the left parapharyngeal space and the soft tissue of the lower neck is accompanied by a large liquid low-density shadow, considering abscess formation ( Fig. 1.d).General anesthesia, oral trachea cannula, neck incision and drainage of pus, see a large number of thick yellow pus with odor; pus cavity involving submandibular space, supraclavicular fossa space and pre-tracheal space. Diagnosis: infection of the left parapharyngeal space; infection of multiple spaces in the deep neck.

Case 5
Male, 48 years old. He was admitted to the hospital on March 17, 2020 due to "left-sided sore throat, limitation of mouth opening with neck swelling and fever" for 3 days. He has a history of diabetes, poor normal control, and a history of drug abuse. He has been detoxi ed for 10 years.Physical examination on admission:T: 38. 5

Treatment
Antibiotic treatment: The ve patients were treated with cephalosporin antibiotics and metronidazole intravenous drip in the early stage of the disease, while vancomycin, linezolid, meropenem, ornidazole and other antibiotics were empirically upgraded in the progression of infection, and then antibiotics were adjusted according to bacterial culture and drug sensitivity.

Surgical treatment
All 5 patients underwent neck incision, debridement and drainage in time. Daily rinsing and dressing changes after surgery:Trilocular tube irrigation in 2 cases (cases 2 and 4) ; 2 cases of negative pressure drainage (case 1, 3); 1 case (case 5) negative pressure drainage combined with partial wound opening and dressing change. And 3 cases (cases 2, 4, 5) tracheotomy, Three cases (cases 2, 4, and 5) had tracheotomy, and two cases (cases 1, 3) were intubated through the mouth to keep the airway open.

Comorbidities and complications treatment:
Three cases (cases 1, 3, and 5) with diabetes were treated with hypoglycemic therapy by insulin, of which cases 1 and 5 were also expanded with blood volume to correct ketoacidosis. Except for case 2, the remaining 4 cases were complicated by pneumonia and pleural effusion, and were actively treated for anti-in ammatory, atomizing inhalation, and sputum excretion. Systemic supportive treatment: Nasal feeding, intravenous uid supplement and timely correction of hypoproteinemia.

Results
The ve patients were all in the SICU intensive care unit after surgical drainage, and were transferred back to the general ward after stable disease.After the above systemic treatment, all patients were cured and discharged, hospitalized for 14-53 days, with an average hospitalization of 35.8 days.3 cases (Case 1, Case 2, case 5) were nally diagnosed as "neck Necrotizing Fasciitis", which underwent more than 2 times of debridement and drainage, and had a long time of washing and dressing change.Two cases had ketoacidosis, three had mediastinum infection, and four had pneumonia. We summarize the relevant information of the diagnosis and treatment of these 5 patients as follows, see Table 1.

Discussion
The de nition of deep neck space infection and the characteristics of serious deep neck infection, and the relationship between neck necrotizing fasciitis.
The fasciaof the neck divides the neck into many potential cell ulitis spaces,with the hyoid bone as the boundary,which can be divided into the submandibular space,the submental space,and the parapharyngeal spaceabove the hyoidbone. The pretracheal space, and the suprasternal space and the super cial cervical space, the retropharyngeal space, the Visceral vascular space, and the prevertebral space below the hyoid bone that communicates with each other. Due to the interconnection between the deep gaps of the neck [10], after the gap infection, the infection where the pus accumulates can spread along the anatomical pathway or between adjacent gaps.These spaces communicate downward with the pericardium, parietal pleura and mediastinum, thus becoming the entrance and passage for neck and throat infections to enter the thoracic cavity. DNIs are mostly caused by infection sources around them, such as pharynx, tonsils, teeth and other infections, not limited to a single space, but can spread to adjacent spaces and tissues to cause airway obstruction, pneumonia, neck necrotizing fasciitis, descending mediastinum In ammation, septicemia, sepsis and other high-risk complications [11,12], so it can be considered that the development of the above complications is a serious DNIs. All cases have airway obstruction; 4 cases complicated with pneumonia; 3 cases caused upper mediastinitis and pericarditis;3 cases developed cervical necrotizing fasciitis(CNS).We believe that CNF is a serious DNIs, and its diagnosis is not established at one time, but is gradually con rmed according to the development and changes of the disease. Some authors believe that gas formation indicates a more serious infection process [13]. In this group of all cases, there is gas formation on CT images. It can be considered that one of the characteristics of severe DNIs is the formation of "gas".
The inducement of serious deep neck infection, pathogenic bacteria, and the experience of diagnosis and treatment of this disease.
In this study, 3 of 5 patients had a history of diabetes, and all the 3 patients who with descending mediastinitis had a history of diabetes. Umeda et al. [14] reported 48 cases of CNF patients with descending mediastinitis. Among them, the mortality rate of patients with diabetes was 39.5%, which was signi cantly higher than the mortality rate of patients without underlying diseases (16.7%). Diabetes has been identi ed as the most common systemic disease of deep neck infections [1,2.4,16,17]. In particular, patients with diabetes over 10 years of age are more prone to multi-space infections in the deep neck [18]. DNIs with diabetes are more severe and di cult to control, prone to ketoacidosis, and in severe cases may have complications such as septicemia and sepsis, and have a higher mortality rate [11].
The possible mechanisms for analysis are as follows: Disorders of substance metabolism, dysfunction of carbohydrates, increased lipolysis, and negative balance of protein metabolism in diabetic patients make the body's immune function decline, and it is in a susceptible state; In diabetic patients, fat metabolism products increase and accumulate in the body, which increases the growth and reproduction of Gram-negative in the body; Hyperglycemia is also conducive to the growth of pathogenic microorganisms such as bacteria, and concurrent infections can form a vicious circle, that is, infections cause uncontrollable hyperglycemia to further aggravate the infection; Monocyte IL-1β expression is abnormally low in diabetes, which can increase the body's susceptibility to certain toxic bacteria [19]; The risk of periodontal infection, caries, and apical abscess in diabetic patients is signi cantly higher than that in non-diabetic patients, and it is more prone to odontogenic DNIs. Therefore, diabetes is an important cause of severe DNIs.
Analysis of DNIs in 173 cases by Srivanitchapoom et al. [20] showed that DNIs infection route was odontogenic > pharyngeal > with unknown cause > glandular origin (48.6%, 19.7%, 16.8%, 6.9%). Although different sources of infection have been reported, pharyngeal and odontogenic DNIs is still the main infection route for most DNIs, but there are still some unknown causes. In this study, 2 of the 5 patients were acute epigytitis and 3 were DNIs secondary to peritonsil abscess, all of which were pharyngeal.
Another study believes that advanced age is one of the high-risk factors for DNIs [21]. Cases in this group are 43-81 years old, with an average age of 61.8. It can be considered that elderly DNIs tend to develop into severe cases. The severe DNIs in this group are all males. Whether males are more likely to develop into severe DNIs remains to be further investigated in the future, but previous literature have reported that DNIs show a trend of more men than women [3,22].
Streptococcus and anaerobic bacteria are the main pathogenic bacteria in the deep neck space infection, and mixed infection is the main [23,24]. In this group of cases, except for one case, the culture of the bacteria was negative, and the culture of the other cases was negative bacilli, streptococcus, and anaerobic bacteria, which is consistent with the characteristics of mixed infection. There are 2 cases of drug-resistant Acinetobacter baumannii, 1 case of anaerobic bacteria (digestive streptococcus), and 1 case of facultative anaerobe (Klebsiella oxytoca), all of which are di cult to control. It is easy to cause serious disease of DNIs. 2 cases cultured fungal, considering the diabetes itself and the secondary infection caused by antibiotics.
CT has the advantages of fast and intuitive, and has obvious advantages in the diagnosis of DNIs, so imaging examination is particularly important.The characteristic manifestations of CT diagnosis of DNIs are as follows: 1. When cellulitis occurs, the infected muscle is swollen, the edge is blurred, the fat in the fascial space disappears, and the occulent density increases; After the formation of the abscess, the pus cavity showed a low density, the pus wall strengthened annularly, and some pus cavity had gas [3]. CT can promptly diagnose potential serious complications such as upper airway obstruction, jugular vein thrombosis, and descending mediastinitis [25].The CT of this group of patients showed a large amount of gas accumulation in multiple spaces of the fascia, and some of the soft tissues were torn in the center and the edges were uneven, which was consistent with the imaging characteristics of severe DNIs.

Treatment and experience:
Active antimicrobial therapy, open drainage and supportive care are the basic treatment of DNIs. Some scholars [11] believe that if CT examination reveals that abscesses are widespread, early surgical incision and drainage is the key method of treatment.It has been reported in the literature [26,27] that patients with dyspnea and a maximum abscess diameter > 2.0 cm should be surgically interventioned as soon as possible. Incision and drainage can reduce local pressure, prevent infection from spreading further to the deep neck and mediastinum, inhibit anaerobic bacteria, and reduce upper airway obstruction.
Therefore, incision and drainage is the key to the treatment of severe DNIs. We believe that individualized drainage schemes should be selected according to the infection gap, location and scope:1) Direct incision and drainage: the debridement can be repeated multiple times, the disadvantages are the need for multiple dressing changes, excessive trauma, and large scars left on the skin after recovery; 2) Negative pressure drainage: sucking out the pus after debridement, which can continuously discharge the pus out of the body, and it is also convenient for continuous washing and uninterrupted negative pressure suction can close the gap caused by the formation of abscess, Cases 1 and 3 adopted this method.3) trilocular tube drainage: It has negative pressure suction and is also conducive to washing when dressing change. Cases 2 and 4 use this method. Case 5 due to multiple gap infections and abscess formation on both sides of the deep neck, a combination of direct incision and negative pressure drainage was used.Therefore, according to the condition of the patient and choosing the appropriate incision and drainage method for the patient, it is conducive to treatment. Some studies have found that using a drainage tube does not prolong the patient's hospital stay [28] .
In DNI, tracheotomy has been stated as the gold standard in the management of compromised airway [29]. Maintaining airway unobstructed is also a top priority for treatment. Severe DNIs are often associated with airway obstruction. When surgical incision and drainage are performed, intraoperative traction and damage to the tissue of the posterior pharyngeal space and upper mediastinal tracheoesophageal sulcus can cause tissue edema. Postoperative airway obstruction may be aggravated. Therefore, the airway should be closely observed, and emergency tracheal intubation or tracheotomy should be prepared at any time to maintain the airway patency. For example, patients with moderate to severe laryngeal obstruction and di culty in opening mouth should consider tracheotomy. However, tracheotomy is an operation after all, and it will aggravate neck trauma, so it still needs to be cautious. In this group of cases, there are 2 cases of tracheal intubation, extubation within one week, close observation to avoid tracheotomy, and from these 5 patients, tracheotomy patients treated in ICU longer than tracheal intubation. But some studies think [30], in DNI,tracheotomy may decrease the need for ICU care and decrease complications related to longer intubation periods. Some studies believe that the exact location of the infection may also afect the choice of airway management [31]. Therefore, for severe DNI, the choice of tracheal intubation or tracheotomy needs to be individually evaluated according to the disease and systemic condition.
Although there is no uniform standard for the use of antibiotics, antibiotics are used empirically in the early stages of treatment, and then sensitive antibiotics are selected based on bacterial culture.Monitoring of vital signs, attention should be paid to the treatment of patients with underlying diseases. Patients with severe DNIs often have diabetes, should control blood sugar, and correct ketoacidosis. To strengthen systemic nutrition support, those who have di culty opening their mouth or cannot eat due to intubation, need to nasally feed a high-protein, high-vitamin and low-fat diet, regularly review electrolytes, liver and kidney function, etc., pay attention to liver and kidney function damage and other complications caused by drugs and diseases themselves, pay attention to water and electrolyte balance and correct it in time.
In a word, severe DNIs often occur in patients with low immunity such as diabetes. They are often infected by a combination of streptococcus and anaerobic bacteria. Pharyngeal and odontogenic are the most common. The "pneumatosis" of CT is the imaging feature of severe DNIs.Timely personalized incision and drainage, correct evaluation of the disease, choose tracheal intubation or tracheotomy to maintain airway opening, combine with the results of bacteriological culture to select sensitive antibiotics, and pay attention to the treatment of complications.

Declarations
Ethics approval and consent to participate According to Medical Research Council Tool, the presented case series does not require ethical clearance.

Consent for publication
Written informed consent for publication was obtained from all Five patients.

Availability of data and materials
Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.

Competing interests
The authors declare that they have no competing interests.

Funding
None.

Authors' contributions
Ling Jin and KaiFan have written the following article. Ling Jin and Kai Fan contribute equally to this work.; Shuangxi Liu,Shiwang Tan, Yang Wang,and Yumin Zhao completed the collection of case information and data;Shaoqing Yu has reviewed the article and operated on all of the cases discussed. The author(s) read and approved the nal manuscript.