Bengt Salén

Anatomy of the Rat Middle Ear

The rat is of value in otological research for many reasons. For instance, the middle ear structures are easily approachable. Recently a couple of studies in the rat have been published concerning the

Repair of Experimental Tympanic Membrane Perforations

In this investigation the healing pattern of experimental central and marginal pars tensa perforations in cats and rats was studied by using light and scanning electronmicroscopic techniques. The perforations were closed by hyperplastic squamous epithelium exhibiting a marked keratin production. This keratin formed a membranous structure which primarily appeared to close the perforation. No ingrowth of squamous epithelium into the middle ear cavity could be detected. Generally speaking, the perforations had closed within 9-11 days in rats and within 12-14 days in cats.

Absorbable Gelatin Sponge (Gelfoam) In Otosurgery: One Cause of Undesirable Postoperative Results?: An Experimental Study in the Rat

Absorbable gelatin sponge (Gelfoam)--commonly used in otosurgery--was gently inserted or firmly packed into the middle ear cavities of rats. The postoperative changes were evaluated 2 to 3 months later when, apart from some air-filled canals leading from the tympanal orifice of the Eustachian tube towards the attic, the middle ear cavity had become filled with newly formed bone and an amorphous mass of adhesions and bridles. The mass consisted of loose connective tissue, with fibroblasts, vessels and inflammatory cells. The tympanic membrane was retracted and fixed to the promontory. There were no signs that any Gelfoam had been removed through the Eustachian tube. The authors proposed that similar tissue reactions may occur in tympano-plasties.

The Release of Histamine from the Pars Flaccida Mast Cells One Cause of Otitis Media with Effusion

In this experimental study in the rat, compound 48/80--a potent degranulating drug of mast cells--was instilled in the external auditory meatus towards the tympanic membrane. Moreover, effusion material was produced in the attic space by blocking the tympanic isthmus with a piece of Gelfoam applied through the tympanic bulla. Both these procedures caused a degranulation of the pars flaccida mast cells and subsequently histamine was detected in the rinsing fluid collected from the middle ear cavity. A possible direct cause of the effusion material in the middle ear cavity may be a degranulation of the pars flaccida mast cells, thus resembling an allergic reaction Type I.

The Role of the Pars Flaccida in the Mechanics of the Middle Ear

The role played by the pars flaccida in the functioning of the middle ear is not altogether clear. The aim of our research was to study the movements of pars flaccida in altering the air volume in the middle ear. By using a sond placed either in the tympanic bulla or in the Eustachian tube in the rat, the middle ear can be insufflated or aspirated with exact volumes of air. Pars flaccida reacted promptly to the changes, while pars tensa remained immobile. A large air volume caused perforation of the pars flaccida. It seems that pars flaccidas function may consist in maintaining a constant middle ear pressure within certain limits, by changing its position.

MYRINGOPLASTY USING SEPTUM CARTILAGE.

Myringoplasty on 25 cases with subtotal eardrum perforation has been made with material from the foremost part of the nasal septum. The transplantate consists of nasal cartilage without the nasal epithelium removed. This tissue gives a stiff membrane resistent against necrosis with sufficient acoustical qualities. 23 cases have healed without complications.

Appearance of effusion material in the attic space correlated to an impaired Eustachian tube function

In adult Sprague-Dawley rats a dysfunction or a total blockade of the Eustachian tube was established by various experimental procedures. The appearance of effusion material in the attic was subsequently considered to be evidence of incomplete ventilation of the middle ear cavity. Though the salpingopharyngeus muscle (SPM) seemed to be the muscle which could open the Eustachian tube maximally, splitting of the soft palate and consequent interference with the tensor veli palatini muscle (TVPM) and the levator veli palatini muscle (LVPM)--but obviously not with the salpingopharyngeus muscle (SPM)--caused the effusion material to be produced in the middle ear cavity. Neither blockade by about 80% of the tympanal orifice nor severing of the tendon of the tensor tympani muscle (TTM) close to the malleus produced any signs of effusion material whatsoever. Our findings strongly suggest that the most important part of the Eustachian tube, as regards ventilation, is the nasopharyngeal portion, as a normally functioning TVPM and LVPM seems to be an absolute prerequisite to prevent effusion material from developing in the attic.

Electromyogram Of The Tensor Tympani Muscle In Man During Swallowing

Experiments were carried out on 2 patients who underwent an operation for chronic otitis media, whereupon the tensor tympani muscle was visualized. A unipolar platinum electrode was inserted into the muscle belly. EMG recordings were made during swallowing and other motor activity. Distinct, pronounced EMG activity was recorded from both patients every time they swallowed. It was concluded that the tensor tympani muscle participates in the act of swallowing and thereby probably contributes to the ventilation of the middle ear.

The Healing Pattern of Experimental Pars Flaccida Perforations

The aim of this investigation was to ascertain how a traumatic perforation of the pars flaccida heals and whether this could explain the way in which the retraction pocket develops. In rats, traumatic pars flaccida perforations were performed on both ears and the healing pattern was registered after various intervals. The perforations healed in 7-10 days, forming in the first instance an indrawing of the pars flaccida and after 12-14 days an adhesive retraction, i.e., ther pars flaccida adhered to the neck of malleus. The retraction pocket was filled with wax, keratin and detritus. At the base of the retraction, epithelial inclusions could be found, which could explain why these retractions were not self-cleaning.

The Stapedial Artery in the Rat

Arteria stapedialis in the rat was studied in healthy rats and in experimental otitis media with effusion (OME). The mean diameters of the vessel was calculated to approximately 460 μm (healthy) and 4