Hearing is a very important ability of humans, and it is the process of detecting and interpreting sound waves to deduce meaningful information. The process of hearing starts with the outer ear, basically the pinna which is the external part of the human ear. The ear is divided into three sections which are the Outer ear, the Middle ear, and the Inner ear. The outer ear goes to the eardrum, the middle ear goes from the eardrum to the oval window and the inner ear includes the Cochlea and the Vestibules, and the ear cells. I am actually not going into the ear in full, today's post is on Eustachian tube dysfunction, but let me quickly explain the process of hearing as fast as possible.
The Outer Ear starts with the auricle (pinna), and the external acoustic meatus (which is the hollow cartilage that connects the outer ear to the middle ear).
The Middle Ear is made up of the ear ossicles which are the malleus, incus, and Stapes which are the smallest bone in the body. The wall of the middle ear is made up of tegmentum bone, and the base wall of the inner ear is known as the jugular base/floor, the lateral wall of the inner ear is known as the membranous wall, the medial wall is known as the Labyrinth wall, the anterior wall is the carotid wall, and the posterior wall is the mastoid bone. The Stapes is the closest to the inner ear, and it interacts with the inner ear through the oval window. The middle ear also has muscles known as the stapedius muscles which anchor the Stapes, as well as the tensor-tympani muscle which interacts with the tympanic membrane and the malleus.
The Inner Ear starts at the other end of the oval window, and it receives mechanical vibration signals from the stapes through the oval window. The inner ear is comprised of the cochlear which has the hair cells (which have a shell-like look), the vestibules, and the semicircular canal. With earing in the internal ear, the cochlear fluid is being vibrated by the vibration from the ossicles in the middle ear, which moves the Cochlear hair cells, after which the signals are sent through the round window and are sent to the brain through the sensory nerves which form the cranial nerve 8 (vestibulocochlear nerve). the cochlear is important for hearing while the vestibular system is important for maintaining balance and spatial orientation.
The Eustachian Tube also known as the auditory tube is found in the inner ear and connects to the middle ear. The major part of the middle and inner ear is basically bony, and the auditory tube is a canal that connects the middle ear to the nasal pharynx. The nasal pharynx is made up of the upper throat and the back of the Nasal cavity. The auditory tube is made up of two parts, which are the bony part and the cartilaginous part. It proceeds forward, downward, and medially, forming a 45% angle with the sagittal plane and 30% with the horizontal plane.
The body part of the tube makes up the posterior and lateral one-third of the tube. The lateral end is wide and opens at the anterior wall of the middle ear cavity. Between the bony part and cartilaginous part is the middle part which is narrow and it attaches both parts of the tube. The bony part of the Eustachian Tube is connected to the tensor tympani, medially connected to the carotid canal, and laterally connected to the chorda tympani, the spine of sphenoid, auriculotemporal nerve, and the temporomandibular joint.
The cartilaginous part is what forms the anterior and medial two-thirds of the Eustachian Tube. It forms a triangular plate of fibrocartilage, which forms the superior and medial walls of the tube. The apex of the plate is attached to the medial end of the bony part of the tube, while the base of the tube forms the tubal elevation of the nasopharynx.
Just as the name implies, Eustachian Tube Dysfunction is a condition where the Eustachian tube, pharyngotympanic, or Auditory tube isn't functioning properly. Epidemiologically, it is estimated to affect about 1% of the population, which is a large number, although it looks small in percentage. It has a higher prevalence in children, and males are more likely to be affected at younger ages while females are at the adult stage.
The eustachian tube is usually closed and would open only for the purpose of regulating gaseous pressure changes, and draining the middle ear fluid into the nasal pharynx. This dysfunction happens when there is an inflammation or disruption to the tube, which could cause it to inadequately open or close in other to regulate pressure changes and drain middle ear fluids. The inability of the tube to open properly will lead to obstructive Eustachian Tube Dysfunction (Obstructive ETD), while a condition where the tube remains opened will lead to a condition known as Patulous Eustachian Tube Dysfunction (patulous ETD). Another type of ETD is the Baro-Challenged induced ETD where the tube is not properly openedas a result of altitude changes.
This dysfunction can be caused by certain factors such as Gastroesophageal reflux disease (GERD), Upper Respiratory Tract infection, Rhinosinusitis, smoking (impairing the function of the cilia in the tube), Allergies, Recent vaccination, recent adenoidectomy, sarcoidosis, granulomatosis, Aspirin-exacerbated respiratory disease, polyangiitis, and Cleft palate which leads to altered patency of the eustachian tube.
Clinical features of Eustachian Tube Dysfunction will include;
With Obstructive ETD where the Eustachian tube is unable to open, the signs and symptoms would include pressure inside the ear causing pain, hearing, and reduction, aural fullness. In Patlous ETD where the Eustachian tube remains open, the signs and symptoms would include Aural fullness, and Autophony. With Baro-challenged induced ETD, where the Eustachian tube is unable to open properly as a result of a change in altitude, the signs, and symptoms associated with ETD only occur during the period of the person experiencing altitude changes.
The diagnosis for ETD would include;
The treatment of Eustachian Tube Dysfunction is dependent on the underlying cause of the dysfunction. In cases of upper respiratory tract infection, the underlying causes are usually temporary, and using antibiotics, and nasal decongestant can help. Avoiding allergies, nasal corticosteroid, and using anti-histamines can be used to treat allergies related to Eustachian Tube Dysfunction. Treating GERD which is an underlying disease that can cause Eustachian Tube Dysfunction is another treat it. Diatery changes, weight loss, and proton pump inhibitors are a way to prevent GERD. Surgical dilatation of Eustachian tube, Tympanostomy tube, and Autoinsufflation (temporary cases).
