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Biomedical subjects

M J LaRouere

Publications and source records attributed to M J LaRouere.

At least 19 recordsLinked to original sources
PubMed1998

Early post-laser stapedotomy hearing thresholds.

OBJECTIVE: Auditory testing is not routinely performed within 4-6 weeks after stapedotomy, because hearing acuity is thought to be transiently depressed. In rare circumstances, postsurgical auditory and vestibular complaints may lead one to test hearing soon after stapedotomy. The early postoperative effects of carbon dioxide (CO2) and potassium titanyl phosphate (KTP) lasers, which now are routinely used to perform stapedotomies, have not been reported. The purpose of this report is to present normative data for auditory thresholds measured within 2 weeks of laser stapedotomy. STUDY DESIGN: The study design was a prospective, unblinded study. SETTING: The study was conducted at three academic medical centers. PATIENTS: Thirty-six subjects undergoing 38 stapedotomies for otosclerosis by 5 surgeons participated. MAIN OUTCOME MEASURES: Behavioral audiometry was performed using standard techniques beginning before surgery and continuing through > 1 year after surgery. RESULTS: The CO2 laser was used in 26 stapedotomies and the KTP laser was used in 12. Nine cases were revision procedures. Bone conduction pure-tone averages and speech discrimination scores did not worsen during the early postoperative period. Bone conduction at 250 and 4,000 Hz dropped slightly within the first 2 weeks (-4.3 and -6.7 dB) but recovered thereafter. Bone conduction at 1,000 Hz actually improved within the first week after surgery (+6.2 dB, p = 0.021). Significant improvements in air conduction thresholds (and air-bone gap) were seen at the second week and late audiometry. The results for CO2 and KTP laser-treated groups were not significantly different. CONCLUSIONS: Cochlear function is not significantly depressed in the early postoperative period after laser (CO2 or KTP) stapedotomy.

Audiometry, Pure-Tone↗
PubMed1996

Temporal bone encephalocele and cerebrospinal fluid leaks.

Nineteen cases of temporal bone brain herniation and cerebrospinal fluid (CSF) leaks in 17 adult patients since 1987 are reviewed. Of these 19 cases, 11 were spontaneous CSF leaks, 6 were related to chronic otitis media, and 2 were posttraumatic. Among the 10 women and 7 men, the average age was 51.2 years, with average follow-up time of 2 years, 7 months. Two cases were repaired by a middle fossa craniotomy approach, 1 case by a transmastoid approach, and 16 by a combined transmastoid and middle fossa approach. Ten cases utilized the preferred technique of fascia-bone-fascia to repair the defects. The diagnosis was made on clinical grounds in 18 of the 19 cases, with ancillary diagnostic test providing little useful information. There were no postoperative surgery-related complications, and definitive repair was accomplished in one stage in all cases.

Adult↗
PubMed1996

Surgical treatment of Ménière's disease.

Several reliable surgical procedures aimed to control the vertigo associated with Meniere's disease exist. Vestibular preservation and ablative procedures are available with the latter divided between hearing preservation and destructive operations. Factors to consider prior to choosing a surgical option include the age, health, and employment status of the patient; the degree of hearing loss in the involved ear; and the status of the contralateral ear.

Adult↗
PubMed1995

Pulsatile tinnitus associated with a laterally placed sigmoid sinus.

We describe a case of subjective pulsatile tinnitus associated with a laterally placed sigmoid sinus. CT showed an enhancing eroding through the medial wall of the right mastoid. Two-dimensional time-of-flight MR angiography and conventional cerebral angiography revealed the tortuous and laterally deviated sinus.

Adult↗
PubMed1994

Facial nerve outcome in acoustic tumor surgery.

Seventy-three procedures involving 70 acoustic tumors were carried out over 3 years. The majority of tumors (65) were removed by the translabyrinthine approach. Tumor size ranged from 0.5 through 5.0 cm. All patients underwent intraoperative facial nerve monitoring: 22 patients developed immediate facial palsy (House-Brackmann grades II-VI); 11 patients recovered completely; 11 patients (15.7%) had persistent paralysis. The incidence of long-term, poor outcome (H-B grade IV-VI) was 5.7 percent. The overall incidence of facial palsy was not found to be related to tumor size; however, facial paralysis associated with large tumors exhibited a poorer House-Brackmann grade compared to small and medium lesions. The use of intraoperative facial monitoring has enhanced the surgeon's ability to preserve facial nerve function by reducing the overall incidence of postoperative facial paralysis.

Cranial Nerve Neoplasms↗
PubMed1993

Titration streptomycin therapy in Menière's disease: current concepts.

Soon after its discovery, streptomycin sulfate was found to be beneficial in the treatment of tuberculosis. However it also was found to have toxic effects, primarily vestibular and typically sparing the auditory nerve until higher doses were administered. The first reported use of streptomycin in the treatment of vertigo was in 1948. This was soon followed by its use for treating Menière's disease. Although excellent control of vertigo was achieved significant post-treatment oscillopsia was experienced by these completely ablated patients. A protocol of titration streptomycin therapy was established that effectively controls vertigo while decreasing the incidence of oscillopsia. This report presents three patients with Menière's disease treated with this protocol.

Adult↗
PubMed1992

The effect of pentoxifylline on cochlear blood flow.

Pentoxifylline, a phosphodiesterase inhibitor and hemorrheologic agent has been found to increase oxygen delivery to ischemic tissue. Intravenous pentoxifylline was administered to normal guinea pigs in order to assess the effect of pentoxifylline on cochlear blood flow and to elucidate its mechanism of action. Intravenous pentoxifylline was found to acutely increase cochlear blood flow in a dose-dependent manner. In normal animals, the effect appeared strongly related to the rheologic properties of this agent rather than a vasodilative action. Normovolemic hemodilution with 75% dextran resulted in no increase in cochlear blood flow during infusion of pentoxifylline, whereas the application of nitroprusside over the round window failed to abolish the effect of pentoxifylline.

Animals↗
PubMed1991

The effects of Carbogen, carbon dioxide, and oxygen on noise-induced hearing loss.

An investigation into the effect of Carbogen (95% O2/5% CO2), 5% CO2/air, and 100% oxygen on cochlear threshold shifts caused by noise was undertaken. Five groups of eight pigmented guinea pigs were exposed to 105 dB broad band noise for 6 h per day for five consecutive days with each group receiving the various gaseous mixtures either during noise exposure or for 1 h immediately after noise exposure. A control group received the same noise exposure but respired air. Auditory threshold shifts, as measured by the auditory evoked brainstem response, were measured at 2,4,8,12,16, 20 and 24 kHz. Recordings were taken pre-exposure and at Day 1, 3, 5, and Weeks 2 and 3 after noise exposure. Carbogen, given during noise exposure, resulted in a trend toward less post noise exposure threshold shift (as compared to controls) which reached statistical significance by Week 3 at all frequencies except 2 and 20 kHz. Subjects given Carbogen after exposure also showed a general trend toward decreased noise induced threshold shifts, as compared to controls, but this was not statistically significant. The mixture of 5% CO2/air given during noise exposure yielded no difference in threshold shifts as compared to controls. When 100% oxygen was administered during noise exposure, a marked decrease in noise induced threshold shifts could be seen as compared to controls, with differences reaching statistical significance by day 5 at most frequencies. These results indicate that oxygen (i.e. cochlear-oxygenation) is a more important factor than CO2 (i.e., as a vasodilator) in protection of the cochlea from noise induced damage.

Animals↗
PubMed1990

Massive ossifying fibroma of the temporal bone.

Ossifying fibromata are rare lesions of the temporal bone. Because the tumors tend to progress and can become clinically massive, early complete resection is advised whenever feasible to prevent clinically evident recurrences and potentially life-threatening complications.

Adult↗
PubMed1990

Three-dimensional x-ray computed tomography of the temporal bone as an aid to surgical planning.

Three-dimensional x-ray computed tomography (3DCT) has been useful in planning surgical procedures involving craniofacial reconstruction, the pelvis, hip, spine, knee and shoulder. The clinical use of 3DCT in temporal bone surgery has not been evaluated. We used 3DCT to assess temporal bone anatomy in 9 patients. These cases evaluated two encephaloceles, two postinflammatory dehiscences, two temporal bone fractures, one glomus jugulare tumor, one acoustic neuroma, and one meningioma. We found 3DCT useful in these temporal bone applications as a supplement to standard two-dimensional CT scanning (2DCT). While 3DCT provided a better preoperative understanding of the underlying anatomy, no treatment was modified solely on the basis of the information derived from the 3-D presentation of data. We conclude that, although 3DCT images have some qualitative advantages over 2DCT techniques, their value in further defining temporal bone morphology must be evaluated against the cost entailed by their use.

Adult↗
PubMed1990

Hearing preservation following suboccipital removal of acoustic neuromas.

Advances in the diagnosis and intraoperative management of acoustic neuromas have greatly reduced the incidence of neurologic deficits following their removal. Ninety-three patients underwent acoustic tumor removal during a 41/2-year period, and hearing preservation was attempted in 20 cases. Hearing was preserved in 65% of the entire series, and excellent results were obtained in tumors less than 1.5 cm. No patient with a tumor greater than 1.5 cm had serviceable hearing preserved when total tumor removal was performed. Two patients, one with neurofibromatosis and one with an acoustic neuroma in an only-hearing ear, had planned partial tumor removal with preservation of hearing. Preoperative auditory brainstem response results were not predictive of postoperative hearing preservation. Intraoperative auditory brainstem response monitoring demonstrated that loss of wave V consistently correlated with loss of hearing postoperatively, whereas persistence of wave V (with a latency prolongation not exceeding 3.00 ms) was predictive of successful hearing preservation regardless of latency increases.

Audiometry, Evoked Response↗
PubMed1990

Malleus head fixation: association with pseudohypoparathyroidism.

Pseudohypoparathyroidism (PHP) is a heterogenous syndrome resulting from bone and renal resistance to parathyroid hormone (PTH). Hypocalcemia and hyperphosphatemia occur despite elevated PTH levels. Head and neck manifestations of PHP include tetany, laryngeal spasm, and ectopic calcification in the eye, dentition, subcutaneous tissue and brain. The first case of malleus head fixation caused by ectopic calcification in a PHP patient is reported. Normalization of serum calcium and phosphate levels does not appear to retard or correct this abnormality. Ossiculoplasty or amplification is currently the recommended treatment in PHP patients with malleus head fixation.

Adult↗
PubMed1989

Electrically stimulated increases in cochlear blood flow: I. Frequency and intensity effects.

Charge-balanced, sinusoidal current was passed differentially between the apex and round window of the guinea pig cochlea. Cochlear blood flow was measured using a laser Doppler flow monitor. Systemic blood pressure was monitored from a cannula within the common carotid artery. Electrical stimulation increased cochlear blood flow, while systemic blood pressure was unaffected. A cochlear blood flow response parameter, normalized for transient changes in systemic blood pressure, was defined. The magnitude of the response parameter was found to be frequency selective and was also found to be an increasing function of current intensity, with maximum responses obtained with 500 Hz sinusoids. This cochlear blood flow response was not observed in dead animals; was present in preparations paralyzed with gallamine hydrochloride; and was correlated with an increase in cochlear red blood cell velocity, as directly observed by intravital microscopy. These observations imply that electrical stimulation induces a local vasodilation within the temporal bone. The fact that decreased cochlear blood flow was never observed with current injection implies that ischemia is not a likely mechanism of electrically induced tissue damage within the inner ear. The mechanism of this cochlear blood flow response is addressed in a companion report.

Animals↗
PubMed1989

Electrically stimulated increases in cochlear blood flow: II. Evidence of neural mediation.

In a companion paper, we reported that electrical stimulation increased cochlear blood flow (CBF). This response was found to be an increasing function of current intensity and was frequency-selective, with the best response at approximately 500 Hz continuous sinusoidal current. The present investigation seeks to discover the mechanism of this effect. Direct measurement of cochlear temperature during electrical stimulation revealed no evidence of local heating. Autonomic neuronal activation is not likely, as neither atropine, hexamethonium, nor propranolol abolished the evoked CBF response. Strial activity could be suppressed by the use of furosemide, but the evoked CBF response persisted. Inactivation of auditory afferent neurons with kainic acid also did not change the evoked CBF response. Dimethyl sulfoxide, a potent oxygen-free radical scavenger, did suppress the evoked CBF response to a small but significant degree. This suggests that oxygen-free radicals may be produced within the cochlea during electrical stimulation. Finally, the evoked CBF response was completely suppressed by procaine and tetrodotoxin, with recovery of evoked CBF response accompanying recovery of cochlear action potentials. These data indicate that stimulation of neural fibers, distinct from autonomic and auditory afferent neurons, may modulate CBF.

Animals↗
PubMed1989

A comparison of laser Doppler and intravital microscopic measures of cochlear blood flow.

Many inner ear disorders may be caused by alterations in cochlear blood flow (CBF). However, each measurement technique used to monitor CBF has limitations in examining the relationship between otopathologic states and blood flow. This study investigates laser Doppler flowmetry (LDF) and its fundamental drawback: the unknown relationship of LDF output to actual CBF. LDF readings are directly compared with concurrent intravital microscopy (IVM) measures of erythrocyte velocity in the lateral wall of the guinea pig cochlea. Positive end expiratory pressure, spontaneous respiration of 5% and 10% carbon dioxide, phenylephrine, and direct electrical stimulation of the cochlea were used to manipulate CBF. High, positive correlations were found between simultaneous LDF and IVM measurements of CBF. In addition, the study demonstrated that current microdissection techniques used to perform IVM do not cause changes in CBF. IVM measurements of CBF are a more sensitive indicator of CBF changes than are LDF measures. Despite the high correlation between measurement techniques within a single manipulation, simultaneous LDF and IVM measurements differed between manipulations. This may reflect regional changes in CBF affected by these manipulations and differences in the sampled vascular beds contributing to these two measures. It is unlikely that a single calibration factor can be defined that would allow the conversion of LDF output to actual units of blood flow across different manipulations used to alter CBF.

Animals↗