## 4 Clinical and Paralinical Diagnosis
Nasopharyngealngo-laryngeal videofibroscopic examination is an indispensable evaluation for the visualization of the upper aerodigestive tract, highlighting inflammation of the pharyngo-laryngeal mucosa, narrowing of the airways due to swelling of the epiglottis, edema of the laryngeal crown with narrowing of the glottic space, and the appearance of dyspnea. Important salivary stasis can be found in the pyriform sinuses and the bulging of the back wall of the pharynx. The clinical underestimation of the presence of massive tissue edema in the oral cavity represents an increased risk for the patient at the time of transport and during evaluation with a neck and chest CT exam with a contrast substance. There is a risk of producing an acute respiratory arrest that may go unnoticed. Oral or nasotracheal intubation should not be performed because of the risk of injuring the acutely obstructed airway. Tracheotomy or cricothyroidotomy under local anesthesia is recommended. Deep neck infection (DNI) affects the fascial spaces of the neck, and can be fatal [10]. DNI may cause airway compromise, which is associated with serious morbidity, and even mortality. Protecting the airway is essential for managing DNI [40]. Tracheostomy is considered for DNI patients when intubation is hard to perform. However, the decision of whether to perform a tracheostomy usually depends on the physician's clinical consideration. Artificial intelligence (AI) allows computers to perform tasks that normally require human intellect and cognitive processes [41]. Machine learning is a form of AI that allows predictions to be made based on information extracted from input data [42; 43; 44]. Such machine learning methods are referred to as deep learning (DL). However, to date, no DL model is available to help physicians to determine when to perform tracheostomy in cases of DNI, especially when there is no obvious sign of airway obstruction. Thus, our goal was to establish a DL model for predicting the need for tracheostomy in patients with DNI, based on their clinical and CT data. This would help clinicians to decide whether tracheostomy should be performed in cases of DNI, and may lead to improvements in critical care [41]. Infections of the retropharyngeal space present with systemic toxicity, fever, odynophagia, dysphagia, dyspnea, and neck stiffness. Oropharyngoscopic and videofibroscopic examination may show a bulging of the retropharyngeal region. The protrusion of the pharyngeal wall causes respiratory distress, compressing the supraglottic area. The extension of the infection into the danger space or the prevertebral space causes chest pain that may be due to pleural irritation, suggesting the involvement of the pleura or mediastinal spaces, and pain and stiffness localized to the neck. Involvement of the danger space gives rise to the most dreaded complication of retropharyngeal infection, acute bacterial mediastinitis, which may involve the posterior mediastum through the danger space or the anterior mediastum by spreading over the pretracheal fascia to penetrate the parietal pericardium. This infection has a fulminant evolution and a high mortality rate [4]. The infection may spread to the lateral pharyngeal space from the submandibular space via the styloglossus muscle, or may occur following a dental, retropharyngeal, peritonsillar, salivary gland, or local lymph node infection. It is necessary to determine the anatomy of the cervical region for the clinical assessment of the infection of this space. Infection of the anterior (prestilian) compartment of the lateral pharyngeal space presents with pain, fever, stiffness, and trismus in a toxic-appearing patient. Local examination shows the presence of pain in patients when the neck is turned to the side opposite to the infection, due to spasming of the sternocleidomastoid muscle. In contrast, infection of the posterior (retrostylian) compartment does not cause trismus or obvious tissue swelling.