Exploratory tympanotomy refers to the surgical approach to the middle ear and its structures for diagnosis. The steps of exploratory tympanotomy are the same as those that would precede transcanal middle ear surgery, such as stapedectomy or removal of a small glomus tympanicum tumor. The operation is performed under otomicroscopy across the external auditory canal (transcanal). Canal skin incisions are created that permit tympanic membrane elevation to gain the necessary exposure to the middle ear and the structures contained within.
Exploratory tympanotomy takes its origins from early fenestration surgeries performed by Sourdille  and Lempert  for otosclerosis. Rosen performed the same exploratory tympanotomy steps prior to stapes mobilization.  It was simply a means to access the middle ear and its structures.
The ear is composed of external, middle (tympanic) (malleus, incus, and stapes), and inner (labyrinth) (semicircular canals, vestibule, cochlea) portions.
The primary functionality of the middle ear (tympanic cavity) is that of bony conduction of sound via transference of sound waves in the air collected by the auricle to the fluid of the inner ear. The middle ear inhabits the petrous portion of the temporal bone and is filled with air secondary to communication with the nasopharynx via the auditory (eustachian) tube (see the image below).
The tympanic membrane is an oval, thin, semi-transparent membrane that separates the external and middle ear (tympanic cavity). The tympanic membrane is divided into 2 parts: the pars flaccida and the pars tensa. The manubrium of the malleus is firmly attached to the medial tympanic membrane; where the manubrium draws the tympanic membrane medially, a concavity is formed. The apex of this concavity is called the umbo. The area of the tympanic membrane superior to the umbo is termed the pars flaccida; the remainder of the tympanic membrane is the pars tensa (see the image below).
For more information about the relevant anatomy, see Ear Anatomy.
The decision to perform an exploratory tympanotomy is made when middle ear pathology is suspected that requires direct visual inspection and or middle ear manipulation. Diagnosis is not obvious based on either the patient’s clinical presentation or radiographic imaging. The otoscopic examination suggests an abnormal appearance of the tympanic membrane or, possibly, a middle ear mass present. A conductive hearing loss is present on audiometric evaluation and inspection of the ossicular chain’s integrity and mobility is planned. The conductive hearing loss may be post-traumatic, congenital, or acquired.
Indications for exploratory tympanotomy for sensorineural hearing loss are less common, usually for suspected perilymphatic fistula. Perilymphatic fistula is a disorder of an abnormal leakage of perilymph from either the round window or oval window, 2 areas readily accessible by exploratory tympanotomy if surgical repair is required. The symptoms of perilymphatic fistula include hearing loss and vertigo induced on physical exertion. A traumatic event leading to sudden intralabyrinthine fluid pressures usually precedes the onset of symptoms.
Even though the purpose of an exploratory tympanotomy may be to establish diagnosis, the otosurgeon must plan for treatment that will ensue after the exploration. This is the situation for patients with conductive hearing loss. Stapedectomy or ossicular chain reconstruction (re-establishing the continuity of the ossicular chain) may follow an exploratory tympanotomy once the cause is determined. If a middle ear mass exists, measures to biopsy or remove the mass will be undertaken. Middle ear masses include congenital cholesteatoma, glomus tympanicum, or middle ear adenoma, for example.
Exploratory tympanotomy should not be undertaken if the external auditory canal does not permit passage and manipulation of the otologic micro-instrumentation to the tympanic membrane and middle ear. It should also not be performed if the portion of the tympanic membrane annulus that will need to be elevated is poorly visualized. Office examination under otomicroscopy should be performed prior to surgery to determine if an alternative approach to the middle ear should be taken. The ear canal should permit passage of at least a size-5 aural speculum.
The anatomy of the bony external auditory canal may prevent or make exploratory tympanotomy difficult. A prominent anterior bony canal wall bulge may be present. This may limit the space available to raise an adequate tympanomeatal flap and limit exposure of the middle ear. A hypertrophic tympanic ring will create an elevated bony canal floor that will impair visualization of the posterior fibrous tympanic annulus. If the fibrous tympanic annulus is not clearly identified during tympanomeatal flap elevation, a tear in the flap may result and lead to a perforation of the tympanic membrane. Clearly identifying the tympanic annulus and elevating from under it is important.
Various congenital and acquired conditions of the external auditory canal may prevent exploratory tympanotomy. Patients may have varying degrees of congenital ear canal stenosis. This must be kept in mind when operating on patients with craniofacial anomalies or syndromic hearing loss.
Acquired conditions, such as exostoses or osteomas, may physically obstruct and prevent access to the tympanic membrane. In this case, these obtrusive bony canal growths need to be removed prior to exploratory tympanotomy.
Exploratory tympanotomy is performed under otomicroscopy, typically through an aural speculum. A speculum holder may be used depending on the otosurgeon’s preference.
If the external auditory meatus is constricted, an endaural incision through the auricular incisura terminalis may be required to help expand the aperture of the cartilaginous external auditory canal and accommodate the largest size speculum possible.
Prior to elevation of the tympanomeatal flap, the canal skin is infiltrated with a local anesthetic/vasoconstrictor, not only to provide local anesthesia but also for its vasoconstrictive effects to reduce blood loss. Poor hemostasis will result in poor visualization throughout the surgical procedure.
Surgical site preparation should include periauricular areas (tragus, postauricular) that serve as potential tissue graft donor sites. These include cartilage, perichondrium, and fascia.
The otosurgeon should decide, in advance, whether the procedure should be performed under IV sedation/monitored anesthesia care or general anesthesia. The former has advantages by providing the surgeon with immediate patient feedback regarding hearing status, dizziness, or facial nerve stimulation.
Chronic otitis externa and other dermatologic conditions affecting the skin of the external canal may need to be treated with ototopical medications (antibiotics and/or corticosteroids) weeks prior to exploratory tympanotomy. In this way, the condition and health of the canal skin are optimized for surgery. Exploratory tympanotomy may be complicated by external auditory canal skin that is friable, edematous, hypertrophic, or hyperemic.
The outcome for tympanotomy for exploratory purposes is generally good. Care must be taken not to disturb the anatomical relationships between the tympanic membrane and the ear canal, as well as the relationship between the tympanic membrane and the malleus. The tympanic membrane that has been elevated is returned to its original anatomical position and stabilized using ear canal packing. The attachment between the tympanic membrane and manubrium of the malleus should not be disrupted. Inadvertent TM perforations must be repaired at the same setting using standard tympanoplasty technique.
When exploratory tympanotomy is undertaken in the setting of conductive hearing loss without history of otitis media, studies looking at the results of surgical middle ear exploration reveal that the common causes are otosclerosis, ossicular fixation, and ossicular discontinuity. [4, 5]
When exploratory tympanotomy is undertaken in the setting of sudden sensorineural hearing loss, abnormalities in the round window (perilymphatic fistula, scarring, and poor round window reflex) were found in nearly two thirds of the cases. 
Exploratory tympanotomy performed for conductive hearing loss after head trauma reveals that the most common injury is incudostapedial joint disruption. 
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