Width of the extended facial recess: a numerical study of ultrahigh-resolution computed tomography and its implications in minimally invasive otologic surgery.

BACKGROUND: Methods of minimally invasive computer-assisted otologic surgery lag behind other fields. The reason seems to be the extremely small dimensions of the corridors between important structures in the temporal bone and the fact that these structures are encased in bony frameworks, are obscured before drilling, and are not movable. The extended facial recess is a surgical pass to the tympanic cavity. It is bounded medially by the facial nerve and laterally by the tympanic annulus, and varies among individuals. For computer-assisted, minimally invasive temporal bone surgery, high-resolution definition is critically important. AIMS: To determine the width of the extended facial recess and evaluate the computerized findings as a pre- and intraoperative aid to otologic surgery planning. METHODS: Bilateral temporal bone high-resolution computed tomographic images of 100 male and 100 female patients were measured twice at five levels (caudal to cephalic), first using a window-independent algorithm (extended facial recess, full-width at half-maximum), implemented in a computed tomographic image-processing workstation, and then manually with calipers on the same axial computed tomographic images. RESULTS: As expected, the extended facial recess, full-width at half-maximum method yielded the widest values superiorly (4.15 +/- 0.41 mm in the female patients and 4.32 +/- 0.54 mm in the male patients). From this level down, the extended facial recess, full-width at half-maximum method yielded values that tapered gradually to 2.50 +/- 0.56 mm in the female patients and 2.42 +/- 0.46 mm in the male patients at the most interior level. The manual method (extended facial recess, computed tomographic images) yielded a significantly higher value than that obtained with the objective, window-independent method at all levels, and at some levels was higher by as much as one-third. At Level 2, which corresponded roughly to the round window, the extended facial recess was 4.00 +/- 0.65 in the female study group and 4.11 +/- 0.67 mm in the male study group. CONCLUSION: Image processing methods such as extended facial recess, full-width at half-maximum method might lead to fine tuning and thus improvement of computer-assisted otologic surgery. Before clinical application and complete dependence on these automated methods during otologic surgery, their reliability should be further validated.

Ciliary body ablation: where are we and how did we get here?

Management of intraocular pressure remains the cornerstone of glaucoma treatment. Related medical and surgical practices involve increasing aqueous outflow or decreasing aqueous production. Filtration procedures that increase aqueous outflow are the first-line surgical defense in glaucoma. However, some cases of glaucoma are resistant to such treatment. In these cases, ciliary body ablation by various methods has had substantial success. Surgical manipulation of aqueous production has been used in glaucoma management since the turn of the century. Techniques have progressed markedly as technology has produced more discrete therapies designed to decrease aqueous production by destroying ciliary body epithelium. Over the past 90 years success has been achieved with a wide range of techniques, from surgical disinsertion of the ciliary body to recent laser and ultrasound techniques. With the development of more precise contact lasers and endoscopic visualization, side effects have been reduced and clinical success rates increased.

Retinal vascular accidents in glaucoma and ocular hypertension.

The incidence of primary open angle glaucoma in patients with central retinal vein occlusion is reported to be between 5.7 and 66%, while that of primary angle closure glaucoma is from 0 to 9%. (Corrected for the relative incidence of these two types of glaucoma in the general population, these rates are comparable). There appears to be a causal relationship between elevated intraocular pressure and central retinal vein occlusion, which does not correlate with the height to which the pressure is elevated. Other etiologic factors may be important, particularly arteriosclerosis. The association between elevated pressure and branch vein occlusion is less clear. Central vein occlusions occur in 3.5 to 5% of patients with primary open angle glaucoma. Similarly, central vein occlusions occur in approximately 3% of patients with ocular hypertension. It is recommended that ocular hypertensive patients over the age of 65 be treated to lower their pressure below 25 mm Hg.

Malignant glaucoma.

The term "malignant glaucoma" referred originally to a rare and highly feared form of glaucoma occurring in certain postoperative patients. Over time the concept of the disease was expanded to include a group of angle closure glaucomas unresponsive to traditional miotic or filtering therapy. The haphazard lumping of many disease entities under such an umbrella term has caused confusion, which we attempt to resolve through a mechanistic approach to elucidating the pathogenesis of malignant glaucoma based on the anatomical location of obstruction to normal aqueous flow; surgical treatments are suggested based on the pathogenesis. Attention is drawn to the role of the vitreous and anterior hyaloid in combination with a block to normal aqueous circulation, redirection of its flow, high intraocular pressure and vitreous swelling in precipitating malignant glaucoma and creating a vicious circle to maintain it. Surgical management is directed to correcting the obstruction to normal aqueous flow and removing aqueous accumulated in the posterior chamber, vitreous or suprachoroidal space.

Trabeculotomy ab externo and trabeculectomy in congenital and adult-onset glaucoma.

In one prospective study, 75 eyes (47 children with congenital glaucoma) were treated by trabeculotomy. Intraocular pressures were controlled in 93.4% after one or more trabeculotomy operations. In five eyes the intraocular pressure was not controlled and these had a fibrovascular membrane in the angle, extending over the trabeculum and iris base with finger-like processes over the peripheral iris. The eyes that had successful operations did not have this appearance. In a second study trabeculotomy in adult-onset open-angle glaucoma had a high rate of failure (30%) including the use of postoperative medication. Nineteen eyes (17 patients) were operated on, 13 successfully. Another group of 19 eyes (17 patients) were treated by trabeculectomy, with the same follow-up period. The one failure (5%) occurred in an eye in which the angle appeared to be totally closed on gonioscopic examination. The operation was equally effective in black and white patients.

Exercise-induced increase of intraocular pressure in the pigmentary dispersion syndrome.

A 32-year-old man with pigmentary dispersion syndrome had blurred vision and halos after strenuous exercise, associated with a release of pigment into the anterior chamber and increased intraocular pressure (IOP). Additionally, he had typical symptoms after emotional stress or exposure to dim illumination, and had a high IOP without angle closure during a darkroom provocative test. The exercise-induced symptoms and the increase of IOP were prevented by the use of pilocarpine 0.5% drops immediately before exercise.

Subscleral Scheie operation for advanced glaucoma.

The subscleral Scheie procedure is most effective in advanced glaucoma patients with IOP of 35 mm Hg or more and in those patients in need of a secondary or tertiary procedure. The surgical technique is described.

Intraocular pressure rise after argon laser trabeculoplasty.

Eighty-four eyes received 107 argon laser trabeculoplasty treatments at Beth Israel Medical Center between 1982 and 1984 for advanced primary and secondary glaucoma. The prelaser mean pressure was 20.25 mmHg. Pressures taken 1 1/2 hours postoperatively varied widely: the pressure rose after 47 treatments and fell or remained the same after 60. Significant increases in pressure occurred in 10 eyes, after 12 treatments; 42% of these had received burns of 0.8 watts or greater. Pressure changes were correlated with laser burn energy level. Both patients who had significant increases in pressure initially were retreated again--in the same eye--at another time had similar increases in postoperative pressure again, even with lower energy levels. Comparison with the results of previous reports highlights the advantages of limited treatment to the anterior trabeculum with low energy levels.

Astigmatism in cataract surgery.

We report on our investigation into astigmatism in 40 eyes following a corneal cataract incision closed with a continuous 10/0 nylon monofilament suture (Ethilon). Immediately after surgery there was astigmatism caused by the nylon suture (suture-induced astigmatism), its severity depending on the tightness of the suture. It ranged from 1 to 10-5 dioptres, the mean value 4-09 dioptres with a standard deviation of +/-2-5. Removing the nylon suture eliminated this astigmatism and within a few weeks the corneal astigmatism correction in 48% of eyes returned to the preoperative level. In 80% of eyes the difference between the final postoperative corneal astigmatism (4 months after removing the continuous suture) and the preoperative astigmatism was 0-75 dioptres or less and the maximum change was 1-5 dioptres. In 40% of eyes the axis of the cylinder changed from a horizontal to an oblique axis but did not change from a with- to against-the-rule axis. The degree of astigmatism remained constant while the suture was in place and in 50% of eyes was equal to or less than 3 dioptres. The mean of the spherical equivalents was 11-31 dioptres with a standard deviation of +/-1-25. A spectacle correction 14 days after operation prescribed either as the mean spherical equivalent (11-50 dioptres) or according to the patient's refraction will give satisfactory vision until the suture is removed 4 months after operation. The degree of astigmatism following a corneal section and continuous nylon suture compares very favourably with astigmatism following other suturing techniques for cataract.

Ocular hypertension: a comparative follow-up of black and white patients.

Forty-four eyes in 25 black patients are compared with 92 eyes of 47 white patients in a population with ocular hypertension followed up for 1 to 12 years in a glaucoma clinic. The black patients present at a younger age than the whites and their mean initial intraocular pressure is significantly higher. The fact that more black ocular hypertensives developed glaucoma--8 eyes (18.1%) in the black population as compared with 5 eyes (5.4%) in the white population--is attributed to these two differences.

Comparative study of Watson's and Cairns's trabeculectomies in a Black population with open angle glaucoma.

A comparative study of the effectiveness of Watson's and Cairns's trabeculectomy in a Black South African population with open-angle glaucoma is presented. The eventual success rate of 91-6% is comparable with that found in Whites, and the results were similar with both methods.

Influence of pH on the efficacy of pilocarpine.

Pilocarpine 4% solutions at pH 4.1 and 5.8 were compared in a double-blind clinical trial on 24 eyes of patients with primary open-angle glaucoma. Each drug was used over a period of 1 week. No significant difference in the lowering of intraocular pressure was found, and the near-neutral solution of pilocarpine was found to be equally stable when compared to the acid solution over a 6-month period.

Plasma cortisol suppression response in the South African black population with glaucoma.

Plasma cortisol suppression was measured in 25 Black glaucomatous patients and in 19 Black patients of similar age and sex, but without glaucoma, who acted as controls. Initial serum cortisol levels were found to be slightly higher in the glaucomatous group. The response to systemically-administered cortisone was statistically more marked in the glaucomatous patients compared with the control group.

Cytomegalovirus retinitis: a manifestation of the acquired immune deficiency syndrome (AIDS).

Two homosexual males with the "gay bowel syndrome' experienced an acute unilateral loss of vision. Both patients had white intraretinal lesions, which became confluent. One of the cases had a depressed cell-mediated immunity; both patients ultimately died after a prolonged illness. In one patient cytomegalovirus was cultured from a vitreous biopsy. Autopsy revealed disseminated cytomegalovirus in both patients. Widespread retinal necrosis was evident, with typical nuclear and cytoplasmic inclusions of cytomegalovirus. Electron microscopy showed herpes virus, while immunoperoxidase techniques showed cytomegalovirus. The altered cell-mediated response present in homosexual patients may be responsible for the clinical syndromes of Kaposi's sarcoma and opportunistic infection by Pneumocystis carinii, herpes simplex, or cytomegalovirus.

Trabeculectomy: a modified surgical technique.

A modified surgical technique is described for trabeculectomy using contemporary limbal incisional techniques for a simplified dissection of the lamellar scleral flap, a technically easier operation, with smoothly dissected surfaces. The results and complications are comparable to those using the standard method.

Relationship between the gas composition of the middle ear and the venous blood at steady state.

Concomitant continuous measurements of the steady-state gas composition of the middle ear and of the venous blood were recorded by mass spectrometry in four guinea pigs. The following mean values were obtained for the partial pressures of middle ear gases; nitrogen + argon, 606.4 mm Hg; oxygen, 46.2 mm Hg; and carbon dioxide, 60.2 mm Hg. The corresponding values for the venous blood were as follows: Nitrogen + argon, 563.4 mm Hg; oxygen, 38.0 mm Hg; and carbon dioxide, 61.4 mm Hg. The similarity of the steady-state gas composition of the middle ear to that of the venous blood suggests that the partial pressures of the gases in the middle ear are controlled by interchange with gases present in the blood.

Cochlear implantation in healthy and otitis-prone children: a prospective study.

OBJECTIVE: To evaluate and compare the timing of surgery, intraoperative findings, and otitis media-related outcome of cochlear implantation in children who are otitis-prone with their counterparts who are not otitis-prone. STUDY DESIGN: Prospective. METHODS: Children referred for cochlear implantation were assigned to a non-otitis-prone group (group A: normal otoscopy on their first visit after referral) or an otitis-prone group (group B: current or a recent history of otitis media at referral). Group B patients were managed using a structured protocol aimed at preimplantation otitis media control. The study reviewed pre-, intra-, and postoperative data. RESULTS: Of the 18 children studied, 8 were assigned to group A (mean age at referral, 40.6 mo) and 10 to group B (mean age at referral, 31.6 mo). For otitis media control, all otitis-prone children underwent ventilating tube insertion (various numbers of procedures before implantation). Only one otitis-prone child required cortical mastoidectomy also. Time from referral to implantation was similar in the two groups (mean, 6.6 mo). High-resolution computed tomography data showed mastoid pneumatization to be significantly smaller in the otitis-prone group, but the facial recess was not smaller in this group. During implantation, 10 children had inflamed middle ear mucosa. Seven of these belonged to group B. All of these seven children had a round window niche obliterated by the inflamed mucosa, which had to be removed for round window membrane identification. After implantation, only one child had drainage through the ventilating tube for more than 1 week. Two children in group B developed otitis media (1 year postimplantation) that was overcome within 1 week. There were no otitis media-related complications. CONCLUSIONS: If a structured protocol is used for the control of otitis media before cochlear implantation, otitis media should not require a delay in implantation. In otitis media-prone children, the round window niche is often obscured by inflamed mucosa. Its removal is mandatory for identification of the round window membrane. After cochlear implantation, otitis media is not a frequent occurrence.

Otitis media in children with cochlear implants.

Fifty children who received a cochlear implant between 1991 and 1995 were evaluated for incidence of acute otitis media (AOM). Thirty-seven (74%) children had AOM before implantation and 8 (16%) after implantation. All children who had AOM after implantation had a history of AOM. A subgroup of 14 children required ventilating tubes for recurrent AOM before implantation. Five (35.7%) in this group had AOM after implantation. The incidence and severity of AOM decreased after implantation. All episodes of postimplant AOM were successfully treated with routine oral antibiotics, and no infectious complications occurred. A history of recurrent AOM should not inordinately delay cochlear implantation.

Necrotizing external otitis in patients with AIDS.

In a retrospective review of seven patients with AIDS who were diagnosed with necrotizing external otitis between 1990 and 1995, it was found that the presentation of necrotizing external otitis in patients with AIDS differed from the classic description of malignant external otitis in several respects. The patient population was significantly younger and nondiabetic. Granulation tissue was usually absent from the external auditory canal and Pseudomonas aeruginosa was not the predominant pathologic organism. Also, outcome was found to be significantly worse. Thus a high index of suspicion must be entertained and vigorous local and systemic treatment initiated early in the course of disease to achieve a satisfactory outcome.

Surgical technique for implantation of the totally ossified cochlea.

OBJECTIVES: Among the technical challenges of cochlear implant surgery is electrode insertion into the fully ossified cochlea. Earlier drill-out techniques have two significant drawbacks: 1. up to one half fail when the electrode pulls away from the cochlea; and 2. extended radical mastoidectomy, abdominal fat graft for obliteration, and closure of the external auditory meatus are required. A simplified technique is described that allows positive fixation of the cochlear implant electrode and in selected cases avoids a radical cavity with obliteration. STUDY DESIGN: Technical description with case reports and hearing outcomes. METHODS: Ten cadaver temporal bones were dissected to determine middle ear landmarks that overlie the basal turn of the cochlea from the transcanal approach and to establish the feasibility of the intact canal wall procedure. Surgery was performed on four patients who had preoperative imaging evidence of full ossification, two with the canal wall down, and two with canal wall up. Standard measures of speech recognition were used to evaluate hearing. RESULTS: Critical surgical landmarks are the round window, carotid artery, cochleariform process, and oval window. The procedure was successfully performed on four patients and open-set speech recognition is present in each. CONCLUSIONS: This canal wall up procedure allows long electrode insertion without radical cavity/obliteration in patients with fully ossified cochleas and prevents distraction of the electrode from the cochlea. While open-set word recognition was achieved by all subjects, results are poorer than expected for patients with limited or no ossification.