Japanese and foreign literature concerning cholesteatoma of the external auditory canal is reviewed. Between two major theories on the etiology of cholesteatoma of the external auditory canal, one that supports the origin in the external auditory canal per se has been more widely accepted than the other that seeks the origin in the middle ear. Pathology of this disease includes ; 1) intact tympanic membrane or the one with occasional thinning, 2) hyperkeratinization in the bony protion of the exteranal auditory canal and 3) occasional bony destruction in the external auditory canal. Among many theories on the developmental mechanism the disturbance of normal migration of the epithelium of the tympanic membrane and the external auditory canal due to various reasons, such as local inflammation or morphological abnormalities, with eventual accumulation of debris and bony destruction appears most plausible for the explanation of the pathology.
Through a series of experimental study of auditory brain stem response (ABR) in rats under anesthesia, the authors have found the followings; 1) the most successful recordings of ABR in rats for a wide frequencies of sound could be obtained by placing the cathode at the forehead and the anode at the top of the head, 2) use of an ear mold and a sound collector helped to prevent the attenuation of the stimulating sound pressure, 3) being low in resistance, a silver ball electrode has been found to yield better results by reducing the artifact during the recording, 4) a conventional dose of the anesthetics, urethane chloralose, has been found not to produce umtoward effect on the recording but an excessive dose usually produced an elevation of the threshold of ABR.
In an attempt to evaluate objectively the hypersensitivity of the nasal mucosa the author measured airway resistance of the nasal passages after local application of allergen discs or of acethylcholine solution in cases with nasal allergy. As to the results, nasal resistance increased on the test side in hypersensitive cases while no such increases were.noted in cases without hypersensitivity of the nasal mucosa. The author concluded nasal airway resistance reflects faithfully the reaction of nasal mucosa in nasal allergy.
There are two kinds of microvascular anastomosis; end-to-end and end-to-side, but no essential differences in these two. If the diameters of the two vessels are too different in size to make end-to-end anastomosis, end-to-side anastomosis can be chosen. As an example, a case of the superficial temporal artery (STA) cortical branch of the middle cerebral artery (MCA) anastomosis is described to explain the technical points of the procedure of end to side anastomosis. (The diameter of the vessels: 1-1.5 mm) The STA as a donor vessel should be dissected free from the subcutaneous tissue leaving some perivascular soft tissue around it, not to injure the vasovasorum of the STA. However the tip of the STA ca. 3 mm in length, where anastomosis is performed, should be completely free from the perivascular soft tissue. If this soft tissue is left around the tip of the STA and caught into the anastomosis cavity, the process of thrombosis occures there. This dissection of the STA should be done under an operating microscope. Temporary clips must have low pressure. To make the anastomosis cavity larger, the STA should be cut obliquely and longitudinally in addition. (A<b) The edges of the cut-end are better left. (Fig. 1) The lumen of the vessel is washed with heparinized saline. As a recipient vessel, the cortical branch of the MCA is prepared after cutting the arachnoid membrane. A rubber dam is laid under the recipient vessel in order not to njure the cortical surface of brain during the procedure of suturing. A 10-0 monofilament nylon is used for sutures. A microforceps (Inox No.5) in the left hand is inserted into the vessel and opened gently and through a space between the two tips of the forceps, a needle is sticked into the vessel wall (Fig. 2) A microforceps (Inox No.1) is used as a needle-holder in the right hand. The intima of the vessels may not be picked with forceps. If so, thrombosis will occur at the site. During the operation the vessels should always be kept wet. Intraoperatively, and for 1 week postoperatively low molecular dextran, 500 ml per day, is used as an antiplatelet drug. Systemic use of Heparin is not necessary. Blood transfusion is not recommended till Hb is under 9g/dl, to keep the potentiality of patency higher.