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Eben Alexander III, Hanne M. Kooy, Marcel van Herk, Marc Schwartz, Patrick D. Barnes, Nancy Tarbell, Robert V. Mulkern, Edward J. Holupka and Jay S. Loeffler

✓ Distortions of the magnetic field, such as those caused by susceptibility artifacts and peripheral magnetic field warping, can limit geometric precision in the use of magnetic resonance (MR) imaging in stereotactic procedures. The authors have routinely found systematic error in MR stereotactic coordinates with a median of 4 mm compared to computerized tomography (CT) coordinates. This error may place critical neural structures in jeopardy in some procedures. A description is given of an image fusion technique that uses a chamfer matching algorithm; the advantages of MR imaging in anatomical definition are combined with the geometric precision of CT, while eliminating most of the anatomical spatial distortion of stereotactic MR imaging.

A stereotactic radiosurgical case is presented in which the use of MR localization alone would have led to both irradiation of vital neural structures outside the desired target volume and underdose of the intended target volume. The image fusion approach allows for the use of MR imaging, combined with stereotactic CT, as a reliable localizing technique for stereotactic neurosurgery and radiosurgery.

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Richard B. Schwartz, B. Leonard Holman, Basem M. Garada, Paulo A. Carvalho, Rebecca Folkerth, Marc S. Schwartz, Jay S. Loeffler, Dennis C. Shrieve, Joseph F. Polak, Peter McL. Black and Eben Alexander III

This study was conducted to determine the sensitivity of dual-isotope single-photon emission computerized tomography (SPECT) in predicting tumor recurrence and survival in patients treated with high-dose radiotherapy for malignant gliomas.

Studies using SPECT with thallium-201 (Tl-201) and technetium-99m (Tc-99m) hexamethypropyleneamine oxime (HMPAO) in 50 consecutive patients with malignant astrocytomas treated by surgery and high-dose radiotherapy were performed 1 day before reoperation. Maximum uptake of Tl-201 in the lesion was expressed as a ratio to that of the contralateral scalp, and uptake of Tc-99m HMPAO was expressed as a ratio to that of the cerebellar cortex. Patients were stratified into groups based on maximum radioisotope uptake values in their tumor beds. Differences in tumor histopathology at reoperation and 1-year survival between SPECT groups were determined by using chi-square analysis.

The majority of patients in Group IA (Tl-201 ratio less than 2 or Tc-99m HMPAO ratio less than 0.5) showed radiation changes in their biopsy specimens (85.7%); they had an 85.7% 1-year survival rate. Group II (Tl-201 ratio between 2 and 3.5) had predominantly infiltrating tumor (78.6%); they had a 42% 1-year survival rate. Almost all of the patients in Group III (Tl-201 ratio greater than 3.5) had solid tumor (93.3%) and they had a 6.7% 1-year survival. Survival and pathological data differed significantly among groups (p less than 0.009).

Dual-isotope SPECT data correlates with histological findings on reoperation and postoperative survival in patients with malignant gliomas.

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Richard B. Schwartz, B. Leonard Holman, Joseph F. Polak, Basem M. Garada, Marc S. Schwartz, Rebecca Folkerth, Paulo A. Carvalho, Jay S. Loeffler, Dennis C. Shrieve, Peter McL. Black and Eben Alexander III

Object. The study was conducted to determine the association between dual-isotope single-photon emission computerized tomography (SPECT) scanning and histopathological findings of tumor recurrence and survival in patients treated with high-dose radiotherapy for glioblastoma multiforme.

Methods. Studies in which SPECT with 201Tl and 99mTc-hexamethypropyleneamine oxime (HMPAO) were used were performed 1 day before reoperation in 47 patients with glioblastoma multiforme who had previously been treated by surgery and high-dose radiotherapy. Maximum uptake of 201Tl in the lesion was expressed as a ratio to that in the contralateral scalp, and uptake of 99mTc-HMPAO was expressed as a ratio to that in the cerebellar cortex. Patients were stratified into groups based on the maximum radioisotope uptake values in their tumor beds. The significance of differences in patient gender, histological characteristics of tissue at reoperation, and SPECT uptake group with respect to 1-year survival was elucidated by using the chi-square statistic. Comparisons of patient ages and time to tumor recurrence as functions of 1-year survival were made using the t-test.

Survival data at 1 year were presented according to the Kaplan—Meier method, and the significance of potential differences was evaluated using the log-rank method. The effects of different variables (tumor type, time to recurrence, and SPECT grouping) on long-term survival were evaluated using Cox proportional models that controlled for age and gender.

All patients in Group I (201Tl ratio < 2 and 99mTc-HMPAO ratio < 0.5) showed radiation changes in their biopsy specimens: they had an 83.3% 1-year survival rate. Group II patients (201T1 ratio < 2 and 99mTc-HMPAO ratio of ≥ 0.5 or 201Tl ratio between 2 and 3.5 regardless of 99mTc-HMPAO ratio) had predominantly infiltrating tumor (66.6%); they had a 29.2% 1-year survival rate. Almost all of the patients in Group III (201Tl ratio > 3.5 and 99mTc-HMPAO ratio ≥ 0.5) had solid tumor (88.2%) and they had a 6.7% 1-year survival rate. Histological data were associated with 1-year survival (p < 0.01); however, SPECT grouping was more closely associated with 1-year survival (p < 0.001) and was the only variable significantly associated with long-term survival (p < 0.005).

Conclusions. Dual-isotope SPECT data correlate with histopathological findings made at reoperation and with survival in patients with malignant gliomas after surgical and high-dose radiation therapy.

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Marc S. Schwartz, Seth A. Riddle, Johnny B. Delashaw Jr., Michael A. Horgan, Jordi X. Kellogg and Sean O. McMenomey

In the treatment of acoustic neuroma, operative results have improved greatly during recent years, with high rates of functional cranial nerve preservation. Because of this, it has become more important to consider issues of patient satisfaction and quality of life (QOL) following treatment for these lesions. The authors have developed a novel questionnaire designed to measure QOL in patients with acoustic neuromas, and they administered it to 50 consecutive patients at least 6 months after acoustic neuroma surgery. Overall QOL was judged to be good but with definite minor difficulties, including some problems with hearing, facial nerve function, headache, tinnitus, dizziness, activity level, enjoyment of life, and emotional well-being. No significant differences were found between age groups and different operative approaches, and only minor differences were found in relation to tumor size. Patients with intracanalicular tumors fared no better than those with cerebellopontine angle tumors. Analysis of the data suggests an overall good outcome from acoustic neuroma surgery; however, when discussing the possible effects on postoperative QOL, even the potential minor problems should not be minimized, especially in patients undergoing operation for small or intracanalicular tumors.

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Michael A. Horgan, Jennifer C. Kernan, Johnny B. Delashaw, Marc S. Schwartz and Todd Kuether

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Marc S. Schwartz and R. Michael Scott

The authors report the case of a 30-year-old woman who was a long-term intranasal cocaine abuser and who presented with transient ischemic attacks and multiple cerebral infarctions that were associated with moyamoya syndrome. The authors suggest that, because of its sympathomimetic effects, chronic cocaine use may promote intracranial arterial stenosis, distal ischemia, and subsequent formation of moyamoya-like vessels. The patient has remained clinically stable with no new episodes of stroke 6 years after undergoing “pial synangiosis” (modified encephaloduroarteriosynangiosis) to revascularize both hemispheres. Cocaine abuse may lead to moyamoya syndrome and may represent a chronic effect on the cerebral vasculature.

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Marc S. Schwartz, James I. Cohen, Toby Meltzer, Michael J. Wheatley, Sean O. McMenomey, Michael A. Horgan, Jordi X. Kellogg and Johnny B. Delashaw Jr.

Object. Reconstruction of the cranial base after resection of complex lesions requires creation of both a vascularized barrier to cerebrospinal fluid (CSF) leakage and tailored filling of operative defects. The authors describe the use of radial forearm microvascular free-flap grafts to reconstruct skull base lesions, to fill small tissue defects, and to provide an excellent barrier against CSF leakage.

Methods. Ten patients underwent 11 skull base procedures including placement of microvascular free-flap grafts harvested from the forearm and featuring the radial artery and its accompanying venae comitantes. Operations included six craniofacial, three lateral skull base, and two transoral procedures for various diseases. Excellent results were obtained, with no persistent CSF leaks, no flap failures, and no operative infections. One temporary CSF leak was easily repaired with flap repositioning, and at one flap donor site minor wound breakdown was observed. One patient underwent a second procedure for tumor recurrence and CSF leakage at a site distant from the original operation.

Conclusions. Microvascular free tissue transfer reconstruction of skull base defects by using the radial forearm flap provides a safe, reliable, low-morbidity method for reconstructing the skull base and is ideally suited to “low-volume” defects.

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Marc S. Schwartz, Gregory J. Anderson, Michael A. Horgan, Jordi X. Kellogg, Sean O. McMenomey and Johnny B. Delashaw Jr.

Object. Use of orbital rim and orbitozygomatic osteotomy has been extensively reported to increase exposure in neurosurgical procedures. However, there have been few attempts to quantify the extent of additional exposure gained by these maneuvers. Using a novel laboratory technique, the authors have attempted to measure the increase in the “area of exposure” that is gained by removal of the orbital rim and zygomatic arch via the frontotemporal transsylvian approach.

Methods. The authors dissected five cadavers bilaterally. The area of exposure provided by the frontotemporal transsylvian approach was determined by using a frameless stereotactic device. With the tip of a microdissector placed on targets deep within the exposure, the position of the end of the microdissector handle was measured in three-dimensional space as the microdissector was rotated around the periphery of the operative field. This maneuver was performed via the frontotemporal approach alone as well as with orbital rim and orbitozygomatic osteotomy approaches. After data manipulation, the areas of exposure corresponding to the polygons used to define these handle positions were calculated and directly compared. On average, the area of exposure provided by the frontotemporal transsylvian approach was increased 26 to 39% (p < 0.05) by adding orbital rim osteotomy and an additional 13 to 22% (not significant) with removal of the zygomatic arch.

Conclusions. Significant and consistent increases in surgical exposure were obtained by using orbital osteotomy, whereas zygomatic arch removal produced less consistent gains. Both maneuvers may be expected to improve surgical access. However, because larger and more consistent gains were afforded by orbital rim removal, the threshold for removal of this portion of the orbitozygomatic complex should be lower.

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Michael A. Horgan, Gregory J. Anderson, Jordi X. Kellogg, Marc S. Schwartz, Sergey Spektor, Sean O. McMenomey and Johnny B. Delashaw

Object. The petrosal approach to the petroclival region has been used by a variety of authors in various ways and the terminology has become quite confusing. A systematic assessment of the benefits and limitations of each approach is also lacking. The authors classify their approach to the middle and upper clivus, review the applications for each, and test their hypotheses on a cadaver model by using frameless stereotactic guidance.

Methods. The petrosal approach to the upper and middle clivus is divided into four increasingly morbidity-producing steps: retrolabyrinthine, transcrusal (partial labyrinthectomy), transotic, and transcochlear approaches. Four latexinjected cadaveric heads (eight sides) underwent dissection in which frameless stereotactic guidance was used. An area of exposure 10 cm superficial to a central target (working area) was calculated. The area and length of clival exposure with each subsequent dissection was also calculated.

The retrolabyrinthine approach spares hearing and facial function but provides for only a small window of upper clival exposure. The view afforded by what we have called the transcrusal approach provides for up to four times this exposure. The transotic and transcochlear procedures, although producing more morbidity, add little in terms of a larger clival window. However, with each step, the surgical freedom for manipulation of instruments increases.

Conclusions. The petrosal approach to the upper and middle clivus is useful but should be used judiciously, because levels of morbidity can be high. The retrolabyrinthine approach has limited utility. For tumors without bone invasion, the transcrusal approach provides a much more versatile exposure with an excellent chance of hearing and facial nerve preservation. The transotic approach provides for greater versatility in treating lesions but clival exposure is not greatly enhanced. Transcochlear exposure adds little in terms of intradural exposure and should be reserved for cases in which access to the petrous carotid artery is necessary.

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Michael A. Horgan, Johnny B. Delashaw, Marc S. Schwartz, Jordi X. Kellogg, Sergey Spektor and Sean O. McMenomey

✓ As a term, the “petrosal approach” to the petroclival region has a variety of meanings. The authors define a common nomenclature based on historical contributions and add new terminology to describe a technique of hearing preservation that allows for greater exposure of the petroclival region. The degree of temporal bone dissection defines five stages of operation. The authors used the second or “transcrusal” stage, in which the posterior and superior semicircular canals are sacrificed while preserving hearing, in six consecutive cases. Use of a common terminology ensures better understanding among surgeons. In the authors' hands, hearing has been successfully preserved in six patients after partial labyrinthectomy.