Surgery of the skull base.

Tumors involving the base of the skull are often occult and may become quite large before detection is possible. Symptomology varies depending upon the nature of the tumor and its placement. These neoplasms have frequently been considered inoperable simply because of their location, but in recent years microsurgical technique and high speed air drills have allowed the modern temporal bone surgeon to gain improved access to the skull base. A wide variety of surgical approaches to tumors in this area have been described in the past 20 years: translabyrinthine, middle fossa, transcochlear, retrolabyrinthine, retrosigmoid, transpalatal-transclival, and through the jugular bulb. The purpose of this paper is to review the indications, complications, and results of each of these procedures in relation to specific tumors involving the skull base. Case reports illustrate the diagnosis and surgical management of a variety of unusual neoplasms, including an extradural meningioma of the temporal bone and clivus, a low grade squamous cell carcinoma on the tegmen in a radical cavity, a large primary cholesteatoma, an osteoblastoma of the temporal and occipital bones, an XIth nerve neuroma in the jugular bulb area, and an osseous hemangioma involving the facial nerve at the geniculate ganglion.

Preservation of hearing in tumors of the internal auditory canal and cerebellopontine angle.

One hundred thirty-nine tumor removals are reviewed with special interest in ten attempts to save hearing. Three patients with bilateral tumors had some hearing preserved. One of these individuals had a 1 cm tumor removed and his postoperative SRT and discrimination scores were the same as his preoperative ones. Overall, the authors were able to maintain some hearing in six out of ten attempts. While there is no question that patients with bilateral tumors benefit from residual hearing, this is not always true in unilateral cases. The suboccipital and middle fossa procedures are discussed as well as the relative merits of each approach in the preservation of hearing. The total series (139 tumors) is discussed in detail regarding results and complications.

Surgical management of Ménière's disease with the endolymphatic subarachnoid shunt: A five-year study.

The majority of individuals with Ménière's Disease can be successfully managed by medical means; however, there are some patients who become refractory to this form of therapy. It is this group of patients who are candidates for some type of surgical procedure. This paper reviews 109 patients who underwent 112 endolymphatic subarachnoid shunt procedures for the control of their Ménière's Disease. Medical therapy, indications for surgery, surgical technique, results, and complications are covered in detail.

Pulse structure of four pulsars.

The pulse structure of the four known pulsars is given. The pulse is about 38 milliseconds for the two pulsars of longest period, and within the pulsewidth three subpulses typically appear. The pulsar of next longest period typically radiates two pulses separated about 23 milliseconds in time. The one short-period pulsar emits single pulses of constant shape. The first subpulses of all pulsars have nearly the same shape. The shape of the first subpulse agrees well with the pulse shape expected from a radio-emitting sphere which is excited by a spherically expanding disturbance, and in which the radio emission, once excited, decays exponentially.

Parameters of the plasma affecting the radiation of pulsar 1.

Analysis of the relation between time delay and frequency for pulses from Pulsar 1 shows that the dispersive region of the ray path must exceed 300 astronomical units and have an average electron number density less than 8000 per cubic centimeter and average magnetic field strength less than 2 x 10(-3) gauss. These requirements almost guarantee that the observed dispersion takes place in the interstellar medium.

Pulse structure of the pulsating radio source in vulpecula.

The pulses from the pulsating radio source at right ascension 19 hours 19 minutes, declination +22 degrees have the following characteristics: (i) they begin with a sharp leading edge; (ii) they terminate after 37 milliseconds; and (iii) they consist of three subpulses, the first of which is both the strongest and the best defined.