Translabyrinthine removal of large acoustic neuromas.

Several surgical approaches to the cerebellopontine angle and internal auditory canal have been developed for the removal of acoustic neuromas. The choice of an approach may be influenced by hearing levels and tumor size. We reviewed the records of the primary translabyrinthine removal of 167 large (> or = 4 cm) acoustic neuromas performed between 1982 and 1990. Patients ranged in age from 15 to 83 years, with a mean of 43 years (male, 49%; female, 51%). Total removal was achieved in 95%. The facial nerve was preserved anatomically intact in 91%. At follow-up (mean, 2.1 yr), facial nerve function was acceptable (Grades I-IV) in 75% and good (Grades I-II) in 42%. Vascular complications occurred in 4.8%; however, there were no deaths. A cerebrospinal fluid leak occurred in 9.6% of cases, and meningitis occurred in 8.3%. In patients with large tumors where there is little chance to preserve preoperative hearing, we have successfully used the translabyrinthine approach for total tumor removal. The advantages and disadvantages of both the translabyrinthine and suboccipital approaches are discussed.

Predicting long-term facial nerve outcome after acoustic neuroma surgery.

Although anatomic preservation of the facial nerve is achieved in nearly 90% of reported cases after acoustic neuroma surgery, postoperative long-term facial function is of most concern to the patient. This study examines long-term facial nerve function in relation to the immediate postoperative function and the function at time of discharge from the hospital. Subjects included 515 patients who underwent primary acoustic neuroma removal at House Ear Clinic from 1982 through 1989 and who had normal preoperative facial function, an intact facial nerve after surgery, and a House-Brackmann facial nerve grade available immediately postoperatively, at time of hospital discharge, and at least 1 year postoperatively. Rate of acceptable facial function (House grades I-IV) differed significantly (p < or = 0.001) at the three postoperative time intervals: 85.2%, immediate; 73.6%, discharge; 93.8%, long-term. Of those with good immediate function (grades I-II), 98.6% had acceptable long-term function. Of those with poor immediate function (grades V-VI), 69.8% had acceptable long-term function. We conclude that facial nerve recovery after acoustic neuroma surgery is characterized by slight deterioration in the immediate postoperative period, but subsequent improvement in the long-term. Patients can be reliably counseled that acceptable function immediately after surgery is associated with a favorable long-term outcome; poor function immediately after surgery, despite an intact nerve, has a more guarded prognosis.

The association of human coagulation factors VIII, IXa and X with phospholipid vesicles involves both electrostatic and hydrophobic interactions.

Blood coagulation factor X (FX) is converted to its active form (FXa) by a membrane bound multi-protein enzyme complex, comprised of factor VIII (FVIII), factor IXa (FIXa) and FX. Characterization of the molecular forces involved in the association of these proteins with phospholipids is crucial to understanding how these proteins bind to the lipid milieux of physiological membranes. In this report, the molecular forces involved in the association of FVIII, FIXa or FX with phospholipid vesicles (PLV) were characterized by ligand affinity chromatographic analyses. Treating FVIII-affinity columns with agents that disrupt electrostatic interactions caused elution of 15.2% of the total bound PLV, while agents that disrupt hydrophobic interactions caused elution of 84.8% of the total bound PLV. These results demonstrate that the association of PLV with FVIII is primarily hydrophobic. In contrast, the association of PLV with FIXa or FX is largely the result of electrostatic forces. This was established by observing that 71.3% and 78.9% of the total bound PLV was eluted from FIXa- and FX-affinity columns, respectively, by agents that disrupt electrostatic interactions. Of the total bound PLV, 28.7% and 21.2% were eluted from FIXa- and FX-affinity columns, respectively, by agents that disrupt hydrophobic interactions. These data demonstrate that hydrophobic forces play a heretofore unrecognized role in the association of PLV with FIXa or FX.

Definition of the affinity of binding between human von Willebrand factor and coagulation factor VIII.

Factor VIII and von Willebrand factor are two plasma proteins essential for effective hemostasis. In vivo, they form a non-covalent complex whose association appears to be metal ion dependent. However, a precise definition of the nature of the molecular forces governing their association remains to be defined, as does their binding affinity. In this paper we have determined the dissociation constant and stoichiometry for Factor VIII binding to immobilized von Willebrand factor. The data demonstrate that these proteins interact saturably and with relatively high affinity. Computer assisted analyses of the Scatchard data favour a two site binding model. The higher affinity site was found to have a Kd of 62 (+/- 13) x 10(-12) M while that of the lower affinity site was 380 (+/- 92) x 10(-12) M. The density of Factor VIII binding sites (Bmax) present on von Willebrand factor was 31 (+/- 3) pM for the high affinity binding site and 46 (+/- 6) pM for the lower site, corresponding to a calculated Factor VIII: von Willebrand factor binding ratio of 1:33 and 1:23, respectively.

Intraoperative facial nerve monitoring: prognostic aspects during acoustic tumor removal.

Intraoperative facial nerve monitoring with electrical stimulation (IFNMES) has become an integral part of acoustic tumor surgery. We reviewed the records of fifty-six patients who underwent translabyrinthine acoustic tumor removal with IFNMES. There was excellent correlation between intraoperative facial nerve activity and immediate postoperative facial nerve function (24 hours after surgery and at hospital discharge). Our data would suggest that patients who exhibit less than 500 microvolts of ongoing EMG activity during surgery, and who yield at least a 500-microvolt contraction when stimulated with 0.05 milliamps at the brainstem after tumor removal, can expect an excellent immediate facial nerve result (grade I or II).

Melkersson-Rosenthal syndrome.

Melkersson-Rosenthal syndrome is a rare condition, classically associated with a triad of facial and/or lip edema, fissured tongue, and relapsing facial palsy. This article offers a review of the literature and presents two cases of Melkersson-Rosenthal syndrome associated with elevated serum levels of angiotensin converting enzyme in two patients of Thai descent.

Choristomas of the intraoral soft tissues.

Choristomas are rare lesions of the head and neck and may be composed of various types of tissue whose only similarity is their close association in fetal development. We present a case of a cartilaginous choristoma that was successfully treated by surgical excision. Choristomas should be included in the differential diagnosis of any lesion in the oral cavity--especially the tongue.

Vestibular disorders.

This article reviews and updates the pathology associated with the labyrinth and peripheral central nervous system. It serves as an overview to aid in the diagnosis and treatment of vertigo.

Comparison of ossicular replacement materials in a mouse ear model.

Four biomaterials, UF45S5 Bioglass, Silastic, Plasti-Pore, and Proplast, were used to replace the incus in a mouse ear model. Bioglass, a bioactive glass ceramic, compared favorably with the other test materials in maintaining surgical positioning between malleus and stapes and remaining stable to a blast of nitrogen gas and to pick manipulation. In a short-term animal study, Bioglass showed histocompatibility comparable to that of these other implant materials now used in ossicular replacement surgery in humans.