Otoscopy

Chapter 20 Otoscopy



Video Otoscopy



Ear diseases are one of the most commonly encountered conditions for which clients seek veterinary care from the veterinary practitioner and veterinary dermatologist. These diseases frequently pose diagnostic and therapeutic challenges to the veterinarian and can be very frustrating conditions for the clients to treat. Video otoscopy has revolutionized the practice of veterinary otology. It allows for better visualization of the ear, which aids in the diagnosis and management of the ear disease, makes possible digital documentation of the ear disease, and is instrumental in educating clients about ear disease.



Indications


In the past decade, video otoscopy has become more widely utilized for the evaluation and treatment of diseases of the external ear canal and middle ear. Indications for the use of the handheld otoscope still exist; however, the video otoscope has the advantages of superior magnification and lighting, complete visualization of the ear canal and tympanic membrane when instruments (e.g., biopsy forceps, grasping forceps, curettes, and catheters) are used through the instrument channel, and digital capture capability to document the ear disease.


Most video otoscopes are much more durable than the traditional rigid endoscopes; therefore, they can be used in the awake animal in the examination room, as well as in the sedated or anesthetized animal, so they are very versatile. Examination of the external ear canal and tympanic membrane should be part of the general examination, regardless of whether clients complain of any ear disease in their pets. It is important for veterinarians to become familiar with the normal structures in the ear so that they are then able to determine whether an abnormality exists.


The video otoscope is one of the few pieces of equipment that can be used in the examination room and that can allow the client to visualize the ear canal and tympanic membrane along with the veterinarian. Direct visualization of the ear and any abnormalities present will improve the client’s compliance with prescribed therapies and on reexamination offers positive reinforcement for the treatments that were performed. It is an invaluable piece of equipment to use when the ear canal and tympanic membrane are evaluated in a patient with otitis. The most common complaints that clients may have when their pets have ear disease are head shaking, ear scratching, otic discharge, foul odor from the ear, and pain when the ear is manipulated. In some instances, neurologic signs, such as facial nerve paralysis, Horner’s syndrome, vestibular disturbances, or deafness, may be present and may indicate the need to evaluate the patient for middle or inner ear disease.


The initial diagnostic plan for a patient with acute otitis externa should include cytologic analysis of otic exudates in addition to the otic examination so that it can be determined whether an infective agent is present in the ear canal and, if so, what initial treatments should be recommended. In patients with chronic, recurrent otitis externa, in addition to cytologic analysis of otic exudates and an otic examination, diagnostics are needed to determine the cause of the recurrent otitis and to evaluate the patient for concurrent otitis media. These may include, but are not limited to, bacterial culture and sensitivity testing (C/S), a food trial, allergy testing, blood work, biopsies, radiographic imaging of the bulla, deep ear flushing, and myringotomy.


Additionally, in patients with chronic otitis externa, the predisposing factors, primary causes, and perpetuating factors must be identified to control the ear disease. Primary causes of otitis externa are those that result in ear disease in the absence of other factors. Primary causes include parasitic diseases, hypersensitivity disorders, foreign bodies, disorders of keratinization, autoimmune disease, and neoplasia.


Predisposing factors are conditions affecting the patient that increase the risk of developing ear disease but that do not trigger the ear disease. Predisposing factors include conformational abnormalities (e.g., pendulous pinnae, stenotic ear canals, and excessive hair) and ear canal epithelial compromise (e.g., swimming, inappropriate treatments such as hair plucking, trauma from cotton swabs, and irritating topical otic products).


If these primary causes and predisposing factors are not diagnosed and controlled, perpetuating factors such as bacterial and yeast infections, otitis media, and progressive pathologic changes (e.g., stenosis, hyperplasia, fibrosis, and calcification) develop. These perpetuating factors prevent the resolution of the otitis externa even if the primary cause is identified and controlled. The most commonly isolated infectious organisms from the horizontal ear canal in dogs with otitis externa are Malassezia pachydermatis, Staphylococcus intermedius, and Pseudomonas aeruginosa.



Indications for the Use of Video Otoscopy in the Examination Room


For the beginner, the use of the video otoscope in the awake animal can be frustrating because it requires hand–eye coordination. However, the best way to become familiar with using the equipment is to perform video otoscopic examinations on every patient. In the awake patient, proper technical restraint is a must. A technician experienced in handling awake animals for otic examinations will help to expedite the procedure, which results in less discomfort for the patient. Examinations are best performed on an examination table with the animal in sternal recumbency or standing. In the dog, it is best to have the technician stand on the opposite side of the ear to be examined and gently grasp the muzzle with one hand while keeping the other hand on the dorsum of the neck. In the cat, less restraint is usually best: the technician should place a hand on the dorsum of the neck or, if necessary, scruff the cat while the other hand controls the back end.


For evaluation of the ear, the tip of the video otoscope should be placed at the intertragic incisure (incisura intertragica). Then, the external ear canal needs to be gently extended into a straight line by grasping the ear pinna and pulling it up and outward while inserting the otoendoscope. Advance the otoendoscope into the horizontal ear canal as the canal is straightened while looking at the monitor. The focal distance of the video otoscope is such that it is not necessary to penetrate deeply into the horizontal ear canal to visualize the entire canal and tympanic membrane. In the awake cat, it is difficult to visualize the entire rostral and dorsal portion of the tympanic membrane.


Both ears should be examined, and if there is a complaint of unilateral otitis, I will begin with the least affected or unaffected ear first. The least affected or unaffected ear should be used to show the client a normal ear as compared with the clinically affected ear. If both ears are abnormal, then it is helpful to have pictures of a normal ear to show the client. After examination of one ear, the otoendoscope should be disinfected before it is inserted into the second ear. At minimum, I will wipe the otoendoscope with isopropyl alcohol before examining the second ear. If there is a considerable amount of exudate on the otoendoscope, I will soak the otoendoscope in glutaraldehyde for 20 minutes and rinse it thoroughly with tap water, wipe it dry, before placing it in the second ear. Depending on the severity of the ear disease, a complete otoscopic examination may not be possible. However, even if only the vertical ear canal can be viewed with the otoendoscope, the client can be shown the pathology of the ear, which will help them to understand the necessity of additional treatments and diagnostics. A plan for future management of the ear can then be formulated.


The normal vertical and horizontal ear canal should be pink, and in most animals, the cartilage is flexible; thus the otoendoscope should advance easily down the canal. There can be small amounts of wax in the ear canal. In animals with otitis externa, the changes detected in the ear canal are related to the severity of the ear disease. The first changes noted in the ear canals in cases of acute otitis externa include erythema and glandular hyperplasia (Figure 20-1). The amount of exudate in the ear canal is variable and should be documented, as should its color and consistency. A swab sample from each ear should be obtained for cytologic evaluation. If numerous rod bacteria are noted cytologically or the infection has worsened since the last visit, then a bacterial C/S is indicated. In more severe cases of otitis externa, glandular hyperplasia progresses, resulting in stenosis of the canal, sometimes to the point where the otoendoscope can no longer be advanced into the vertical ear canal. The degree of stenosis and hyperplasia should also be documented. Ulcerations may also be noted, especially in ears secondarily infected with P. aeruginosa. Parasites such as Otodectes cynotis may be visualized rapidly moving about in the ear canal with the video otoscope and are usually found in conjunction with dark brown ceruminous (“coffee ground”) exudate. On occasion, masses or foreign bodies may be seen in the ear canal during the video otoscopic examination.



In cases of chronic otitis externa, the tympanic membrane may not be visualized due to excessive exudate, stenosis, hyperplasia, or a combination of these. If the tympanic membrane is visible, the color and gross appearance of the pars flaccida and pars tensa should be noted. Documentation of the findings on the video otoscopic examination of the vertical and horizontal ear canal as well the tympanic membrane is important for comparison during future reevaluations; this documentation should consist of digital images as well as other findings recorded in the patient record.


I find that most patients that allow an otoscopic examination with a handheld otoscope will allow one performed with a video otoscope. However, it is important to note that some dogs and cats will not allow a video otoscopic examination to be performed, despite proper restraint or the experience of the video otoscope user. In addition, some animals’ ears may be too painful to allow any otic examination.


Fogging of the lens during the video otoscopic examination in the awake patient can be a source of frustration. Fogging occurs when the cool lens comes into contact with the warm ear canal. There are a few procedures that can be used to control lens fogging. I use a combination of isopropyl alcohol wipes and a commercially available lens defogger (UltraStop). Before inserting the otoendoscope into the ear, I wipe the tip with an alcohol-soaked gauze sponge and then spray the defogger on the tip. This procedure will need to be repeated if the tip comes into contact with the ear canal epithelium (and subsequently accumulates some wax on the tip) or comes into contact with exudate in the ear canal. Another technique that has been used to defog the lens is to warm the tip of the otoendoscope in a bowl of warm water.




Instrumentation


The standard otoendoscope is a straightforward 0-degree telescope with a length of 7 to 8.5 cm, a tip diameter of 4.75 to 5 mm, and a 2-mm working channel, which is fully immersible and able to be sterilized in ethylene oxide (gas) and autoclaved. The camera is a digital single-chip or three-chip camera of high resolution, with automatic white balance. The standard light source is halogen; however, I prefer the xenon light source, which gives off a “whiter” and brighter light. In addition, if the camera is to be used for other types of endoscopy, the xenon light is the preferred light source. The working channel allows the passage of 5F or smaller catheters, endoscopic forceps, and video otoscopic–compatible curettes. Some may choose to use a rigid cystoscope or arthoscope to examine the ear canal and tympanic membrane. Because of the delicate nature of these scopes, they should only be used in the anesthetized animal.


A dual-port adapter is available with some video otoscopes and can be attached to an external suction device and a fluid bag to provide simultaneous passive suctioning and flushing. External suction and flushing devices are also available and can be used by attachment of a catheter to the unit for directed suction and flushing. A medical-grade monitor is preferred for viewing because the image projected is superior to nonmedical grade monitors. The digital capture system functions like a computer and is invaluable for image documentation. Most have the capability of capturing still images and video clips. Biopsy and grasping forceps and curettes are available for obtaining samples, removing foreign bodies, and dislodging cerumen, respectively. Brushes are available for removing loose hairs and debris.





Otic Anatomy


It is important to understand the anatomy of the external and middle ear when evaluating a patient with ear disease. First, in order to diagnose otic disease, one must be familiar with the appearance of the normal structures of the ear. Secondly, when one is performing a deep ear flush, it is imperative that one is aware of the delicate structures of the ear to avoid damaging them and causing neurologic complications.


The opening of the external ear canal is bounded by the helix (the free, slightly folded margin of cartilage at the base of the pinna) rostrally, the tragus laterally, and the antitragus caudally. The antitragus is a thin, elongated piece of cartilage caudal to the tragus and separated from it by the intertragic incisure (incisura intertragica). This anatomic region is the area in which I will insert the otoscopic cone or otoendoscope for the otoscopic examination. The vertical ear canal runs for about 1 inch, extending ventrally and slightly rostrally before taking a medial turn and forming the horizontal ear canal. There is a prominent cartilaginous ridge that separates the vertical and horizontal ear canals and, when the ear is in its normal position, makes otic examination of the horizontal ear canal difficult without the clinician elevating this ridge by grasping the ear pinna and lifting the ear.


The horizontal ear canal is composed of auricular and annular cartilage. The auricular cartilage rolls as it forms a tube. A separate cartilaginous band, the annular cartilage, fits within the base of this tube. The annular cartilage overlaps with the osseous external acoustic meatus and articulates via ligamentous tissue, giving the external ear canal flexibility.


In most breeds, hairs are present in the external ear canal, decreasing in number from distal to proximal. A very few fine hairs are found at the entrance of the cartilaginous external acoustic meatus. I find that these hairs are a useful landmark for locating the tympanic membrane when flushing an ear.


The middle ear consists of an air-filled tympanic cavity, three auditory ossicles, and the tympanic membrane. The tympanic membrane is located at a 45-degree angle in relation to the central axis of the horizontal part of the external ear canal. The tympanic membrane is a semitransparent membrane that separates the external ear canal from the middle ear, is thin in the center and thicker at the periphery, and is divided into two sections, the small upper pars flaccida and the larger lower pars tensa (Figure 20-2). The pars flaccida is the pink, small, loosely attached region forming the upper quadrant of the tympanic membrane that contains small blood vessels. The pars flaccida is usually flat; however, even in the healthy ear one may identify a bulging pars flaccida (Figure 20-3). The exception is the Cavalier King Charles Spaniel, in which a bulging pars flaccida may be indicative of a disease known as primary secretory otitis media (PSOM) (Figure 20-4).





The pars tensa, the thin, tough, gray structure with radiating strands, occupies the remainder of the membrane. The pars tensa is attached to the osseous ring of the external acoustic meatus. The manubrium of the malleus attaches to the medial surface of the tympanic membrane. The outline of the manubrium of the malleus, the stria mallearis, may be visualized when the tympanic membrane is viewed externally. The pars tensa has a concave shape when viewed externally because of the tension applied to the internal surface of the membrane, where the manubrium of the malleus is attached. The point of greatest depression is called the umbo.


The tympanic cavity consists of a small epitympanic recess, a large ventral bulla, and the tympanic bulla proper. In the dog, there is an incomplete bony septum, the bulla septum, which allows communication between the tympanic bulla proper and the ventral tympanic bulla. On the medial wall of the tympanic cavity, there is a bony eminence, the promontory, which houses the cochlea, and lies opposite the tympanic membrane medial to the epitympanic recess. At the caudolateral portion of the promontory, a foramen called the cochlear (round) window is located. The cochlear window is covered by a thin membrane that oscillates to dissipate the vibratory energy of the perilymph in the scala tympani. The vestibular (oval) window lies on the dorsolateral surface of the promontory immediately adjacent to the pars flaccida (Figure 20-5). It is covered by a thin diaphragm. The footplate of the stapes is attached to the diaphragm over the vestibular window. When flushing the middle ear, one must be very careful to avoid damaging the promontory or the cochlear window and to avoid damaging the inner ear, causing vestibular disturbances or deafness.



The middle ear cavity of the cat is different from the dog’s and is divided by a septum into two distinct regions, the tympanic cavity and the bullar cavity. These two cavities are connected through a narrow foramen between the septum and the petrous bone. In the small dorsolateral compartment lie the auditory ossicles, the osteum of the auditory tube, and the tympanic membrane. The larger ventromedial compartment is an air-filled tympanic bulla. The bony septum should be perforated surgically when middle ear disease is present in both cavities for proper drainage of the middle ear cavity. Rough handling of the bony septum may result in damage to the postganglionic sympathetic nerves. The nerves, which are visible submucosally as fine strands over the cochlear promontory, should be avoided during surgical removal of the septum in the cat.


The three auditory ossicles, the malleus, incus, and stapes, are the bones that transmit and amplify air vibrations from the tympanic membrane to the inner ear. The malleus is attached to the tympanic membrane, the petrous temporal bone, and the incus. The incus is suspended between the malleus and the stapes. The footplate (base) of the stapes is attached to the vestibular window, which is in direct contact with the perilymph fluid. The vestibular window is approximately 18 to 20 times smaller in area than the tympanic membrane.



Procedure for Deep Ear Flush with the Video Otoscope


The video otoscope is an invaluable tool for evaluating and flushing the middle ear of an anesthetized patient with otitis media. I would encourage standardizing the orientation of the video otoscope relative to the animal when utilizing the video otoscope in the anesthetized patient. That way, the surgeon avoids becoming disoriented when the anatomy of the ear is abnormal. Next, make sure that the monitor is easily visible while examining the ear, which means that it is directly in front or to the left or right. It is very awkward for the surgeon to try to view the monitor over his or her shoulder.


The animal should be anesthetized and have an endotracheal tube in place for the deep ear flush. The endotracheal tube will prevent aspiration of any fluid that passes from the middle ear into the auditory tube to the nasopharynx and then to the oropharynx and respiratory tract if a myringotomy and middle ear flush are performed. Before the deep ear flush, the first procedure I perform is radiographic imaging to evaluate the middle ear. I prefer to perform computed tomography (CT) on my patients, but in general practice, this is often not available, and bulla radiographs suffice. Radiographic imaging not only allows evaluation of the middle ear for changes consistent with otitis media (i.e., soft tissue density in the bulla) but it also allows identification of significant changes in the bulla, such as sclerosis or lysis, that may indicate osteomyelitis or a tumor, respectively, which will aid in determining the prognosis for medical treatment of the ear disease.


Just before cleaning the ear, one should obtain swab samples from the external ear canal for bacterial C/S and cytologic examination. Video otoscopic images are taken of the external ear canal for documentation. With the patient in lateral recumbency, preferably on a tub table and a heating pad (those specifically designed for veterinary surgical procedures), the external ear canal is soaked with an ear cleaner or ceruminolytic agent for 10 minutes. I prefer to use a ceruminolytic agent because these products are the best for removing exudate from the ear canal. However, the majority of these products are ototoxic if they enter into the middle ear cavity. Once the ear has been cleaned, if the tympanic membrane is ruptured or torn, I will repeatedly flush sterile saline into the external ear canal to remove the ceruminolytic agent. There is, however, one commercially available ceruminolytic agent, Cerumene, that has been shown to be nonototoxic.


After the external ear canal has been soaked with a ceruminolytic agent or ear cleaner, the external ear canal is flushed with warm sterile isotonic saline with the use of a bulb syringe to remove large debris and exudate. This is followed by flushing with warm sterile isotonic saline with the use of a handheld otoscope with an 8F polypropylene urinary catheter attached to a 12-mL syringe passed through an otoscopic cone. An 8F red rubber feeding tube may be cut to size and used to flush the external ear canal. External flushing devices, such as the Vet Pump 2, available from the manufacturer of the video otoscope, may be used in place of the manual flushing described above. Once the ear is clean, the tympanic membrane is evaluated with the video otoscope and images are taken for documentation. If the tympanic membrane is ruptured or torn, as previously stated, it is important to flush copious amounts of sterile saline into the ear canal to remove the ceruminolytic agent. In addition, once a ruptured or torn tympanic membrane has been identified, do not infuse the ceruminolytic agent into the bulla. Once the exudate has been removed from the external ear canal, I attach the dual-port adapter to the port on the otoendoscope. The dual-port adapter is used to perform passive suctioning and flushing of the external ear canal, which expands the ear canals, further magnifies the ear, prevents lens fogging, and continues to clean the ear. A warmed bag of sterile saline is attached to a Venoset on one port of the dual-port adapter, and a suction hose is attached to the other port. A tear or rupture can be identified by bubbles coming from the tympanic membrane. Once the patency of the tympanic membrane has been determined, I will remove the saline from the ear canal and evaluate the tympanic membrane with the otoendoscope because saline in the ear canal can sometimes cause the tympanic membrane to look opaque (which would be considered abnormal) when it is not. If the tympanic membrane is ruptured, then the patient has otitis media. A myringotomy does not need to be performed, and samples from the middle ear for cytologic and culture analysis can be obtained through the tear in the tympanic membrane. I find it helpful to have technical assistance in obtaining these samples. I will turn the otoendoscope to where the port is ventral, without moving the camera. This allows easy access to the port and keeps the instruments aimed ventrally so that the auditory ossicles and promontory are avoided. I will have a technician stand behind the patient’s head and hold the ear in one hand and the video otoscope in the other. This allows me to have my hands free to flush the middle ear (Figure 20-6). An open-end 3½F Tomcat catheter attached to a 12-mL syringe is placed through the port of the otoendoscope. Saline is flushed into the middle ear cavity and aspirated back for culture, and a second sample is flushed into the middle ear and aspirated back for cytologic analysis. After sample retrieval, the middle ear is flushed with warm sterile saline through the open-ended Tomcat catheter. I will flush and aspirate back 1 mL of sterile saline at a time and will finish when the saline flushed from the middle ear cavity is clear.


Sep 10, 2016 | Posted by in SMALL ANIMAL | Comments Off on Otoscopy
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