# Internal Medicine/Dysphagia
## Definition and Classification

Dysphagia is a complex condition, and understanding its nuances requires categorization. It can be broadly classified into two main types: oropharyngeal dysphagia and esophageal dysphagia.
* Oropharyngeal dysphagia primarily involves difficulties in the initial phases of swallowing, typically from the mouth to the hypopharynx. It can manifest as issues with chewing, forming a cohesive food bolus, and moving it effectively to the back of the throat.
* Esophageal dysphagia, on the other hand, is associated with challenges in the passage of food through the esophagus, often causing sensations of food "getting stuck" in the chest.

## Physiology of Swallowing

Swallowing is a highly coordinated process that comprises several distinct phases. Here, we delve into the physiological intricacies of this vital function:
* Swallowing initiates with a voluntary phase in the mouth. During this stage, food is thoroughly masticated (chewed) and mixed with saliva.
* Following the oral phase, the transfer phase begins as the tongue propels the formed food bolus into the pharynx.
* Entry into the hypopharynx triggers the pharyngeal swallow response, a centrally mediated sequence of actions aimed at propelling food through the pharynx into the esophagus while guarding against entry into the airway.
* This process involves the elevation and forward movement of the larynx, facilitating the opening of the upper esophageal sphincter (UES). The bolus is then propelled through the UES by tongue movement and followed by a peristaltic contraction that clears residue from the pharynx and moves it through the esophagus.
* The lower esophageal sphincter (LES) relaxes to allow the bolus into the stomach.

## Musculature and Innervation

Understanding the musculature and innervation of the swallowing process is crucial:
* The muscles involved in swallowing are striated and directly innervated by lower motor neurons carried in cranial nerves.
* Specific cranial nerves control different parts of the process, such as the fifth (trigeminal) and seventh (facial) cranial nerves for oral cavity muscles, and the twelfth (hypoglossal) cranial nerve for the tongue.
* The upper esophageal sphincter (UES) consists of the cricopharyngeus muscle, the adjacent inferior pharyngeal constrictor, and the proximal portion of the cervical esophagus. Its innervation is derived from the vagus nerve.
* The UES remains closed at rest due to its elastic properties and neurogenically mediated contraction of the cricopharyngeus muscle. It opens during swallowing through a complex coordination of muscle relaxation and movement.

## Pathophysiology of Dysphagia

Dysphagia isn't a singular condition; it can be subdivided based on location and underlying causes:
* Structural dysphagia often results from an oversized bolus or a narrow lumen in the esophagus, causing difficulty in food passage.
* Propulsive or motor dysphagia arises from abnormalities of peristalsis or impaired sphincter relaxation after swallowing.
* It's possible for more than one mechanism to contribute to dysphagia in a patient.

## Oropharyngeal Dysphagia Causes

Oropharyngeal dysphagia can be attributed to various factors, including:
* Neurologic causes, such as cerebrovascular accidents, Parkinson's disease, and amyotrophic lateral sclerosis, which affect the neural control of swallowing.
* Structural issues like Zenker's diverticulum, cricopharyngeal bar, and neoplasia, which hinder the smooth passage of food.
* Iatrogenic causes, often related to surgeries and radiation treatments in the context of head and neck cancer.
* Infectious sources, where mucosal ulceration results in painful swallowing (odynophagia).
* Psychogenic factors like phagophobia (fear of swallowing) or refusal to swallow.

## Esophageal Dysphagia Causes

Esophageal dysphagia, primarily centered around the esophagus, has its own set of causes:
* Structural issues, including Schatzki's rings, eosinophilic esophagitis, and peptic strictures, can narrow the esophageal lumen, making swallowing challenging.
* Gastroesophageal reflux disease (GERD) can lead to esophageal dysphagia by altering esophageal sensation or motility.
* Propulsive disorders, such as achalasia, diffuse esophageal spasm, and scleroderma, impact the normal functioning of the esophageal muscles.
* Various factors, including prior surgery, radiation therapy, and congenital abnormalities, can also contribute to esophageal dysphagia.

## Approach to Diagnosis

When dealing with dysphagia, an accurate diagnosis is pivotal. Here's an overview of the diagnostic approach:
* The patient's history plays a crucial role, helping identify the localization of dysphagia, associated symptoms, and its progression. It can also reveal potential causes, such as prior surgeries or medical conditions.
* Physical examination can provide insights, especially for oropharyngeal dysphagia, by detecting signs like neuromuscular deficits or inflammatory lesions in the mouth and pharynx.
* Diagnostic procedures like fluoroscopic swallow studies, otolaryngoscopic evaluations, and endoscopy are employed based on the suspected type and location of dysphagia.

## Diagnostic Procedures

In-depth diagnostic procedures are essential in uncovering the underlying causes of dysphagia:
* Fluoroscopic swallow studies are instrumental in assessing oropharyngeal dysphagia, revealing issues like bolus retention, regurgitation, and aspiration.
* Upper endoscopy, the primary test for esophageal dysphagia, allows for visualizing mucosal lesions and obtaining biopsies when necessary.
* Esophageal manometry can confirm esophageal motor disorders, while barium radiography complements the evaluation, especially in complex cases.

## Treatment

Effective treatment of dysphagia depends on its specific causes and location:
* Oropharyngeal dysphagia often benefits from therapy to improve swallowing postures and maneuvers. Altering food consistency can reduce aspiration risk.
* Esophageal dysphagia may require esophageal dilation for structural issues or surgical interventions for conditions like achalasia or cancer.
* Infectious etiologies can be treated with antimicrobial medications or management of underlying immunosuppressive conditions.
* Eosinophilic esophagitis can be addressed through dietary changes, proton pump inhibitors, topical glucocorticoids, and esophageal dilation.