Lee A. Harker

Middle cranial fossa acoustic neuroma excision: results and complications.

The middle cranial fossa surgical approach has been used for the removal of acoustic neuromas in 43 patients at the University of Iowa since 1974. Hearing was maintained in 50% of patients with tumors 1.5 cm or less outside the porus acusticus. Postoperative hearing, facial nerve function, and complications were similar to reports using the suboccipital or retrosigmoid approach to preserve hearing for this size tumor. The character of the tumor appears to dictate the postoperative outcome rather than the surgical approach.

Vascular Loop as a Cause of Vertigo

A vascular loop in the internal auditory canal pressing upon the vestibular nerve was found in a series of eight patients with episodic vertigo and severe motion intolerance. All patients had failed medical and surgical therapy for vestibular Menieres disease, which this syndrome closely mimics. A vestibular nerve resection or section medial to the vascular loop produced relief of symptoms in all patients, but one patient required a second operation. We have no test or study to reliably diagnose this syndrome preoperatively. The history appears to be the best indicator to date.

Interpretation of Electrocochleography in Meniere's Disease and Normal Subjects

Electrocochleographic recordings were obtained from 20 subjects with normal hearing and 10 subjects with Menieres disease by using an eardrum electrode. Stimuli included clicks and 6,000-Hz tone bursts. Results were not significantly different between the two groups for summating potential (SP) amplitude, action potential (AP) amplitude, or the SP/AP amplitude ratio. Interpreting the results in light of symptoms on the date of assessment or hearing threshold did not appear to improve separation between the two groups. Various SP/AP amplitude ratio criteria have been proposed in order to separate normal patients from those with Menieres disease. Applying these proposed criteria to our data did not successfully separate the two groups.

Incidence of cholesteatoma with cleft palate.

The overall incidence of cholesteatoma in Iowa has been estimated to be 6.01/100,000 population, or less than 0.01 %. However, in patients with cleft palate seen at the University of Iowa Cleft Palate Clinic between 1947 and 1968 and followed for at least 10 years, the risk of developing cholesteatoma was 9.2%. In order to determine whether this high risk of cholesteatoma is still valid, a comparable retrospective study was undertaken of 153 patients with cleft palate who were born between 1969 and 1977, were enrolled in the University of Iowa Cleft Palate Clinic within 1 year of birth, and were followed by the interdisciplinary team for a minimum of 10 consecutive years. Cholesteatoma occurred in four patients (2.6%), a substantial decrease in the risk of developing cholesteatoma in a well-defined and longitudinally followed population.

Benign Paroxysmal Positional Vertigo: Concomitant Involvement of Different Semicircular Canals

Objectives: We evaluated the simultaneous ipsilateral or contralateral involvement of the posterior and lateral, anterior and lateral, or posterior and anterior semicircular canals in patients with benign paroxysmal positional vertigo (BPPV). Methods: The files of 2,345 patients with BPPV were analyzed. Results: Single-canal BPPV occurred in 2,310 cases (98.5%) — Unilaterally in 2,058 (89.1%) and bilaterally in 252 (10.9%). Multiple-canal BPPV occurred in 35 cases (1.5%). Of these 35 cases, there was simultaneous involvement of the posterior and lateral canals on the same side (23) or on opposite sides (9) in 32 cases (91.4%). Simultaneous involvement of the anterior canal on one side and the posterior canal on the opposite side occurred in 2 cases (5.7%), and that of the anterior canal on one side and the lateral canal on the opposite side occurred in 1 case (2.9%). All cases represented canalithiasis. Conclusions: Multiple-canal BPPV was rare, and usually involved canals on the same side; simultaneous involvement of the posterior and lateral canals was much more common than involvement of the anterior and posterior canals or the anterior and lateral canals. Trauma increased the risk for multiple-canal BPPV, but not the risk for bilateral single-canal BPPV. Cupulolithiasis was not a factor in multiple-canal BPPV.

Major immunoglobulin ratios in carcinoma of the head and neck.

— Serum immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM) levels were determined on 245 patients with carcinoma of the head and neck and on 92 controls. Ratios of these levels were calculated for each subject. The patients with cancer demonstrated elevated serum IgA levels (P <.0001) and elevated IgA/IgM and IgA/IgG ratios (P <.05). No differences were noted when the IgM/IgG ratios were compared between the cancer and the control groups. These observations are offered as evidence that previously reported elevations of serum IgA levels in patients with carcinoma of the head and neck are not merely an index of nonspecific increased immunoglobulin production in these patients.

Electrocochleography in the Presence and Absence of Perilymphatic Fistula

The purpose of the present study was to evaluate the effect of an acute perilymphatic fistula on the amplitude ratio (SP/AP) of the summating potential (SP) and action potential (AP). The effect of the acute fistula on AP threshold was also addressed. Electrocochleo-graphic recordings were obtained before and immediately after surgical laceration of the round window membrane in 19 guinea pigs. Stimuli comprised clicks and 2,000-Hz and 8,000-Hz tone bursts, presented initially at 100 dB peak equivalent sound pressure level and in descending 10-dB steps. After fistula induction the SP/AP significantly increased for the click and 8,000-Hz tone burst stimuli but not for the 2,000-Hz tone burst stimuli. No significant change in AP threshold occurred. These findings suggest that the SP/AP may be sensitive to perilymphatic fistula, at least in guinea pigs. The changes in the SP/AP do not appear to be related to changes in threshold.

Meniere's Disease at the University of Iowa: 1973 to 1980

The goals of treatment in Menieres disease are hearing preservation and control of vertigo. Controversy abounds with regard to the most expeditious and efficacious means of attaining these goals. Low-salt diet, diuretic therapy, endolymphatic-mastoid shunt, and middle cranial fossa vestibular neurectomy are all modes of treatment employed for Menieres disease at the University of Iowa. This review of our experience from 1973 to 1980 summarizes the efficacy of each therapeutic option.

The Relationship Between Pure-Tone Thresholds and Psychoacoustical Tuning Curves in the Hearing Impaired: Preliminary Findings

Physiological evidence from many studies has infered a. close correspondence between elevated thresholds and a reduction in frequency resolution. Data to support such a relationship is of three types. First, animals with an induced thres-hold loss exhibit broadened frequency threshold (tuning) curves (FTC) compared to other animals with normal hearing (e. g. Kiang, Moxon and Levine, 1970). Second, FTCs measured in auditory nerve fibers show elevated thresholds and broadened FTCs after cochlear insult (e. g. ototoxicity, noise exposure, mechanical damage) compared to other nerve fibers recorded from the same animal but before the insult (e. g. Evans et al.1974). Third, measurements within single fibres have been obtained before and after cochlear insult (e. g. Evans and Klinke, 1974, 1982 a,b; Robertson and Manley, 1974). The results showed elevated thresholds and broadened FTCs.

Book Review: Tumors of the Head and Neck

The illustrations are generally good, but surgical sophistication in aesthetic surgery has reached a point where visualization of results shown in standard photographs is almost a sine qua non of any procedures described. It is grossly unfair to the tyro surgeon to deprive him of the opportunity of learning their shortcomings; after all, what one surgeon considers a good result, another may not.