Inner ear fluid volumes and the resolving power of magnetic resonance imaging: can it differentiate endolymphatic structures?

Magnetic resonance imaging (MRI) can accurately recognize minute volumes as small as 1 mm3. The volumes of the utricle and saccule of the inner ear are within the resolving power of MRI, but these structures cannot be recognized because the endolymph and perilymph signals are identical. To clarify the interpretation and description of inner ear structures on MRI, we measured and calculated the volumes of the perilymphatic and endolymphatic spaces of the human ear. We found the total volume of the bony labyrinth to be approximately 192.5 mm3 (endolymph, 34.0 mm3; perilymph, 158.5 mm3).

Anatomical and theoretical observations on otolith repositioning for benign paroxysmal positional vertigo.

OBJECTIVE: To determine if there is an anatomic basis for the assumption that loose, "rogue" otoliths presumed to arise from the utricular macula and theorized to cause benign paroxysmal positional vertigo (BPPV) by impinging on semicircular canal ampullae could be returned to their original site by a series of changes in the position of the head called particle repositioning maneuvers (PRMs). Further, if such otolith movement were possible, once they were replaced into the utricle, would they adhere to the utricular macula? STUDY DESIGN: Kodachrome photographs of 2-mm-thick macrosections of human temporal bones were available for evaluation. The bones were sectioned in horizontal, coronal, and sagittal planes. Rice grains were placed on the photographs of the cross-sections to demonstrate the possible paths taken by loose otoliths under the influence of gravity in different positions of the head. RESULTS: A study of cross-sections of the temporal bone shows that loose macular otoliths after PRMs would tend to fall into the lumen of the utricle. Once the patient assumes the erect position, however, repositioned otoliths would tend to fall into the near or utriculopetal side of the cupula of the posterior semicircular canal, which opens directly into the inferior portion of the utricle, and could cause labyrinth stimulation and BPPV by the same mechanism of misplaced otoliths on the opposite or far side of the cupula. Loose otoliths in the utricle could also stimulate the horizontal ampullae. CONCLUSIONS: PRMs do not remove or fix otoliths in any specific site in the labyrinth. Repositioning of loose otoliths onto the original site in the macula of the utricle, which lies superiorly in the vestibule, could not be accomplished by any of the repositioning maneuvers. If otoliths were to be repositioned on the utricular macula, there is no evidence that the otoliths would adhere to the macula when the patient assumes the erect position. The good results obtained by physiotherapeutic procedures suggest that some other mechanism than repositioning of otoliths is responsible for the relief of BPPV.

An anatomical study of a new portal for ankle arthroscopy.

We describe a medial midline portal between the tendons of extensor hallucis longus and tibialis anterior for arthroscopy of the ankle. We dissected 20 cadaver specimens to compare the risk of neurovascular injury using this approach with that of using standard arthroscopic portals. Compared with the anterocentral portal, the medial midline was a mean of 11.2 mm further from the nearest branch of the superficial peroneal nerve and 10.3 mm further from the dorsalis pedis artery. This portal allows good access to the joint surface and intra-articular structures and has a lower risk of injury to the dorsalis pedis artery, deep peroneal nerve or the medial branch of the superficial peroneal nerve.

Rediscovering general psychiatry: creation of an academic division.

OBJECTIVE: To describe the rationale, origins, and goals of a newly created academic division of general psychiatry within a university setting. METHOD: Literature review, observation, and description. RESULTS: Within 2 years of its inception, the General Psychiatry Division of the University of Toronto has begun to realize some of its goals and further elucidate specific objectives. CONCLUSIONS: In an era of increasing academic subspecialization, the preservation of core skills in psychiatry and the recognition of the continuing public need for psychiatric generalists must be enshrined within academic training programs.

Retraction cholesteatoma of the sinus tympani.

Posteromedial retraction of the tympanic membrane, between the oval window superiorly and the round window niche inferiorly, results in the formation of an epithelium-lined pocket within the sinus tympanic recess. Failure to recognize posterior invagination of the tympanic membrane intraoperatively leads to inadvertent tearing of the tympanomeatal flap at the level of the annulus with epithelial seeding of the middle ear and probably cholesteatoma recurrence. This article focuses on the clinical manifestations and radiographic findings suggestive of sinus tympanic epithelial retraction of the pars tensa and provides direct correlation between human cross-sectional temporal bone anatomy and otomicroscopy. The surgical management of these challenging lesions includes initial endaural access, external meatal bone removal posteromedial to the tympanic annulus and anterior to the vertical portion of the facial nerve, and middle ear ventilation after marsupialization of the epithelial retraction. Although early tympanic membrane retraction can be treated with a ventilation tube, deep epithelial pockets may require additional surgical treatment. A method for the management of sinus tympanic cholesteatomas is demonstrated.

Robots in operating theatres.

Robots designed for surgery have three main advantages over humans. They have greater three dimensional spatial accuracy, are more reliable, and can achieve much greater precision. Although few surgical robots are yet in clinical trials one or two have advanced to the stage of seeking approval from the UK's Medical Devices Agency and the US Federal Drug Administration. Safety is a key concern. A robotic device can be designed in an intrinsically safe way by restricting its range of movement to an area where it can do no damage. Furthermore, safety can be increased by making it passive, guided at all times by a surgeon. Nevertheless, some of the most promising developments may come from robots that are active (monitored rather than controlled by the surgeon) and not limited to intrinsically safe motion.

Fascia and perichondrium atrophy in tympanoplasty and recurrent middle ear atelectasis.

Fascia and perichondrium grafts to replace and reinforce thin, atrophic tympanic membranes (TMs) are recommended by several authors to correct middle ear atelectasis by forming a fibrous, collapse-resistant TM. This study reviewed the status of connective tissue grafts performed over the 10-year period from 1979 to 1988 to determine if these grafts would maintain sufficient strength and fibrous character to resist recurrent atelectasis. The author used fascia or perichondrium to repair 89 TM defects, and 63 ears were available for follow-up: 54 had cholesteatomas and 9 had perforations. Graft atrophy was judged by microscopic otoscopy and Kodachrome otophotography. Fascia TM grafts atrophied in 35 of 43 ears (80%), and perichondrium atrophied in 8 of 20 ears (40%). Grafts maintained their relatively thick and fibrous character in only 20 of 63 ears (32%). If fascia and perichondrium used to correct atelectasis were to atrophy at the same rate as the grafts in this series, atelectasis would recur after attempts to reinforce atrophic TMs. Atelectasis-prone middle ears require intubation despite surgery.

Middle ear gas generation in myringoplasties.

No Gelfoam was used to support the vein in 10 simple underlay vein graft myringoplasties. Computed tomographic studies 24 hours postoperatively showed gas filling 75% to 100% of the middle ears in three ears. The epitympanum and mastoid were also evaluated. Apparently, in some ears the middle ear generates gas in the immediate postoperative period to support fresh vein grafts.

CT and MR imaging of intralabyrinthine schwannoma: report of two cases and review of the literature.

Two cases of intralabyrinthine schwannoma were studied with computed tomography (CT) and magnetic resonance (MR) imaging. On CT scans, a soft-tissue mass was identified in the round window niche in both cases. Widening of the basilar turn of the cochlea and characteristic erosion of the promontory were noticed in one case. Preoperative MR imaging (performed in only one case) revealed a soft-tissue mass in the labyrnth, extending into the round window niche. Findings at CT and MR imaging are discussed, and a differential diagnosis is given. The literature is reviewed. The authors' findings suggest that CT and MR imaging may prove very valuable in the previously difficult preoperative diagnosis of these tumors. In the setting of progressive sensorineural hearing loss, atypical Meniere disease, or recurrent vertigo, the presence of a mass in the labyrinth or labyrinthine windows- delineated on CT or MR images, despite a normal internal auditory canal, cerebellopontine angle, or brain stem - is highly suggestive of intralabyrinthine schwannoma.

Patent eustachian tube in the underaerated middle ear: a paradox.

Secretory otitis media, middle ear atelectasis, and retraction type cholesteatomas are the most frequently occurring chronic middle ear diseases; and eustachian tube obstruction and the generation of negative or less than atmospheric middle ear pressure is said to be an essential factor in the pathogenesis of these diseases. It has been found that habitual sniffing causes high degrees of negative middle ear pressure in diseased ears; this finding demonstrates eustachian tube patency rather than obstruction. Ears intubated for chronic secretory otitis media, middle ear atelectasis, and cholesteatoma were examined to identify patent eustachian tubes. More than one third of the patients aspirated a solution into the middle ear with one or more sniffs by aspirating air from their middle ears, demonstrating eustachian tube patency rather than obstruction.

Evaluating the effectiveness of a process medical audit in a teaching general hospital.

Medical auditing has moved beyond the traditional chart review to the process audit, which identifies deficiencies in care and suggests remedies. In 1981 the audit committee of the Department of Psychiatry at Toronto General Hospital audited the use of hypnotic drugs in the inpatient unit. The audit produced two recommendations: that nursing staff record sleep graphs for inpatients more often, and that an educational program be instituted to change the physicians' patterns of prescribing hypnotics. In 1983 the audit was repeated to test the effectiveness of the 1981 auditing process. The 1981 recommendation produced the desired improvement in recording of sleep graphs. However, the medical staff failed to change their patterns of prescribing hypnotics: oxazepam remained the preferred hypnotic. For the process audit to be effective in improving patient care those using it must ensure that the methods reflect the nature and structure of the professional group they are trying to influence.

Experimental evidence against middle ear oxygen absorption.

The present theory of eustachian tube (ET) function and middle ear (ME) ventilation posits that oxygen absorbed by the ME mucosa causes negative ME pressure which is relieved by periodic opening of the ET during swallowing and yawning. After developing a method to cannulate the ET of mongrel dogs we connected the cannulas hermetically to manometers. This system excluded ET function and tested the oxygen absorption capacity of the ME. When we controlled respiration and maintained blood gas PO2 and PCO2 at normal levels, we were unable to find any manometric evidence of negative pressure of gas absorption in the dog ME. Lowering the PCO2 and raising the PO2 of the blood by hyperventilation caused negative ME pressure which could be measured manometrically. We confirmed these findings with the tympanometer. Raising the PCO2 and lowering the PO2 by hypoventilation caused positive pressure in the ME. There is no evidence in these experiments that O2 absorption occurs or causes negative ME pressure in the dog. To the contrary there is evidence that elevated blood levels of the more diffusible CO2 cause an increase in the ME pressure and lowered CO2 level causes a negative ME pressure.

Cholesteatoma and chronic otitis media following middle ear intubation.

As in any surgical procedure, complications can occur following middle ear intubation for secretory otitis media or atelectasis. Serial Kodachrome studies of the middle ear demonstrate the types of lesions that occur and the methods used to correct them. Chronic otitis media in the form of chronic granulomas or perforations are relatively simple problems that are easily corrected. Cholesteatomas can arise from intubation either by formation of atelectatic pockets following extrusion of the tube or from ingrowth of the surface epithelium of the tympanic membrane onto the medial surface of the tympanic membrane. These lesions often require surgical correction. Middle ear intubation should not be done indiscriminately, and prolonged follow-up of patients is mandatory for the early detection of complications.

Correlation between micro-otoscopy, micropneumatoscopy and otoadmittance tympanometry.

The micro-otoscopic, audiometric and tympanometric findings were correlated in 204 ears seen in a Veterans Administration Hospital ear clinic. Otoscopy, audiometry and tympanometry were done during the same clinical visits. In most cases pneumo-otoscopy with the microscope also was performed. Because we were unable to standardize pressures, we found pneumo-otoscopy of limited value. The data in this series were analyzed from two different points of view to determine the accuracy of the tympanometer in detecting and identifying ear disease. First the otoscopic results were compared with the tympanometric findings. Second, the procedure was reversed and various tympanometric findings were compared to the otologic diagnosis. Otophotographs were obtained in many of the ears to record findings. An otologic evaluation consists in physical and functional examinations and is not complete without both elements. It is important to remember that the tympanogram does not measure hearing loss. Tympanic membrane abnormalities can invalidate measurements of acoustic impedance and lead to a false interpretation of tympanometric findings.

Observations of middle ear pressures. Commentary with movie.

Previous direct measurements of middle ear pressure in ears with serous otitis resulted in the range of from 0 to -10 mm H2O pressure. To confirm these findings we attempted to quantify middle ear pressures by doing myringotomies in serous otitis patients through sterile saline solution. We compared the rate of aspiration of the saline in ears with serous otitis to the rate of aspiration of saline after an experimental myringotomy in an ear model in which known pressures were imposed. To record our findings we used motion picture photography. Layering a film of sterile oil suspension of oxytetracycline and hydrocortisone over dry tympanic membrane perforations resulted in the demonstration of a pulsatile positive pressure of about 6 mm water in many of the ears which we tested. The oil film often formed an external bubble which ruptured after several minutes. In some ears there was no change in pressure and in only a small percentage there was evidence of a decreased pressure by absorption of air in the middle ear during the period of observation. This positive pressure is unrelated to swallowing and suggests that the current theories of middle ear aeration via opening of the eustachian tube may not be valid. These findings were demonstrated with motion picture film.