Endoscopic/Microscopic approach to sphenopetroclival complex: an anatomical study

A dilemma presents itself to the otoneurologist and neurosurgeon when determining the least invasive surgical approach to giant cholesterol cysts (GCC) of the petrous apex of the temporal bone. These lesions can be diagnosed with a fair degree of certainty with imaging studies. Transmastoid and subcochlear approaches may be inadequate to access these lesions, and the transcochlear approach results in the sacrifice of hearing. A minimally invasive, combined microscopic and endoscopic sublabial transsphenoid approach to drain and marsupalize these lesions has been chosen by the authors in those cases that are anatomically possible. The purpose of this article is to establish the feasibility of exenterating anterior petrous apex cells by way of this approach, and to better conceptualize the anatomy of the Spheno-Petro-Clival Complex (SPC). Ten Fresh cadaveric "whole head" specimens were dissected with, endoscopic/microscopic control, through midline, sublabial, transseptal, and transsphenoidal routes to the petrous apex. The three-dimensional relationships of the sphenoid sinus, petrous apex, and the clivus were further demonstrated by dissections of the same specimens from the posterior fossa. Sagittal cut sections were also performed. After confirming the feasibility of this approach by dissections, the technique was adopted for performing drainage of GCC of the petrous apex in clinical cases.

Transsphenoidal surgery utilizing computer-assisted stereotactic guidance

Computer-assisted guidance technology represents the next step in the application of stereotactic techniques to skull base surgery. Use of this 3-D technique reduces operative time and complications as the technique allows a more direct approach with precise real-time anatomical guidance. We present seven cases of transsphenoidal parasellar surgery where this technique has been employed. The pathology included lesions of the sella turcica, parasellar region and the petrous apex.

delta-Aminolevulinic acid effects on neuronal and glial tumor cell lines

Acute intermittent porphyria (AIP) or precursor syndrome is a well described neuropathic clinical entity with incompletely known etiology. The most prominent biological abnormalities associated with this syndrome are elevations in serum and hepatic delta-aminolevulinic acid (ALA) and porphobilinogen (PBG). We determined the impact of ALA and PBG on human neuroblastoma and glioblastoma tumor cell survival as measured by the MTT assay. ALA proved to be cytotoxic in neuroblastoma cells, while PBG lacked cytotoxic effects. This cytotoxic effect of ALA could be enhanced by deferoxamine and diminished by heme, presumably through modulation of ALA synthesis. In conclusion, ALA excess may prove to be associated with the development of neuropathy in AIP.

A saturation threshold for taxol cytotoxicity in human glial and neuroblastoma cells

The cytotoxic effects of taxol at concentrations of 0.001-1.0 microgram/ml were determined in two human glioblastoma multiforme, two neuroblastoma and two primitive neuroectodermal tumor cell lines. The neuroectodermal cell lines were established from previously treated patients, while the glioblastomas were from untreated patients. At exposure durations of 1, 4 and 24 h there was an inverse taxol concentration-survival relationship for all six cell lines as measured by the MTT method. Significant differences in sensitivity to taxol among these cell lines were observed; the most resistant cell line SK-N-FI is characterized by very high levels of MDR1 expression and the most sensitive SK-N-AS by very low levels. An additional level of complexity concerns a saturation threshold for taxol-induced cytotoxic effects which when reached precludes additional effects of prolonged or additional exposure. Tumors of the brain and peripheral nervous system appear to be sensitive to taxol. However, dosage necessary to maximize cytocidal effects in tumors requires knowledge of at least the range of each tumors constitutive sensitivity to taxol and a way to optimize drug delivery.

Combined approach for excision of cervical nerve tumors with dural extension

Tumors of the cervical plexus are rare. Often these tumors are found on routine exam as asymptomatic masses. We present our experience in managing four patients with tumors with dural extension. Three of these lesions were neurilemomas and one was a meningioma. Symptoms and signs included weakness and hypoesthesia. Evaluation included complete neurologic examination with electromyography (EMG). Magnetic resonance imaging (MRI) was the best diagnostic tool to see tumor extent into the epidural and intradural space. Computed tomography (CT) or plain x-rays were used to evaluate the degree of destruction of the cervical spine. The surgical removal of these tumors was performed by a two-team approach. A posterior laminectomy was combined with an anterior neck exploration. Follow-up shows persistent upper extremity weakness in two patients, hypesthesia in three patients, and anesthesia of the anterior chest wall in two patients. Patients with these lesions should be informed of the potential neurologic consequences of removal.

Extensive advanced maturation of medulloblastoma to astrocytoma and ependymoma

Four cases of medulloblastoma in children are reported in which a marked degree of differentiation towards neoplastic adult glioma cells was observed. The original immature and highly malignant tissue had largely disappeared in three and completely disappeared in the fourth. The mature tissues which replaced them included astrocytoma tissues in all four, but ependymoma tissues predominated in two. These cases illustrate a general principle applicable to embryonic tumors, defined as those originating in cells that are still immature. Such maturation and differentiation are presumably associated with a decrease in growth rate and an improved prognosis. A continuation of the process of maturation may account for the unexpectedly favorable course sometimes noted with gliomas in children. The processes of differentiation, dedifferentiation, and anaplasia are discussed, particularly the semantic implications of the terms, and it is suggested that the term "dedifferention" is unfortunate since it may have two different meanings. It may be used as a synonym of anaplasia, or it may imply a progression of change backward on the embryologic pathways along which primitive cells normally mature. The latter may not occur, but the assumption that it does leads to views concerning the glioma group as a whole and the phenomena described in this paper, which we hold to be untentable.