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Kurt R. Lehner and Michael Schulder

Sir Victor Horsley was a pioneering British neurosurgeon known for his numerous neurosurgical, scientific, and sociopolitical contributions. Although word of these surgical and scientific achievements quickly spread throughout Europe and North America in the late 19th century, much of modern neurosurgery’s view of Horsley has been colored by a single anecdote from John Fulton’s biography of Harvey Cushing. In this account, Cushing observes a frenetic Horsley hastily removing a Gasserian ganglion from a patient in the kitchen of a British mansion. Not long after, Cushing left Britain saying that he had little to learn from British neurosurgery. The authors of this paper examined contemporary views of Horsley to assess what his actual reputation was in the US and Canada. The authors conducted a thorough search of references to Horsley using the following sources: American surgical and neurosurgical textbooks; major biographies; diary entries and letters; PubMed; newspaper articles; and surgical and neurosurgical texts. The positive reception of his work is corroborated by invitations for Horsley to speak in America. Research additionally revealed that Horsley had numerous personal and professional relationships with prominent Americans in medicine, including William Osler, John Wheelock Elliot, Ernest Sachs, and (yes) Harvey Cushing. Horsley’s contributions to medicine and science were heavily reported in American newspapers; outside of neurosurgery, his strong opposition to the antivivisectionists and his support for alcohol prohibition were widely reported in popular media. Horsley’s contributions to neurosurgery in America are undeniable. Writings from and about prominent Americans reveal that he was viewed favorably by those who had met him. Frequent publication of his views in the American media suggests that medical professionals and the public in the US valued his contributions on scientific as well as social issues. Horsley died too young, but not without the international recognition that was rightly his.

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Topic Editor Michael Schulder

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Michael Schulder, Danny Liang, and Peter W. Carmel

Object. In this article the authors report on a novel, compact device for magnetic resonance (MR) imaging that has been developed for use in a standard neurosurgical operating room.

Methods. The device includes a permanent magnet with a field strength of 0.12 tesla. The poles of the magnet are vertically aligned, with a gap of 25 cm. When not in use the magnet is stored in a shielded cage in a corner of the operating room; it is easily moved into position and attaches to a regular operating table. The magnet is raised for imaging when needed and may be lowered to allow surgery to proceed unencumbered. Surgical navigation with optical and/or magnetic probes is incorporated into the system.

Twenty-five patients have undergone removal of intracranial lesions with the aid of this device. Operations included craniotomy for tumor or other lesion in 18 patients and transsphenoidal resection of tumor in seven. The number of scans ranged from two to five per surgery (average 3.4); image quality was excellent in 45%, adequate in 43%, and poor in 12%. In four patients MR imaging revealed additional tumor that was then resected; in five others visual examination of the operative field was inconclusive but complete tumor removal was confirmed on MR imaging. In 21 patients early postoperative diagnostic MR studies corroborated the findings on the final intraoperative MR image.

Using a water-covered phantom, the accuracy of the navigational tools was assessed; 120 data points were measured. The accuracy of the magnetic probe averaged 1.3 mm and 2.1 mm in the coronal and axial planes, respectively; the optical probe accuracy was 2.1 mm and 1.8 mm in those planes.

Conclusions. This device provides high-quality intraoperative imaging and accurate surgical navigation with minimal disruption in a standard neurosurgical operating room.

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Charles Davis

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Ceslovas Vaicys, Michael Schulder, Linda A. Singletary, and Arthur A. Grigorian

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Ceslovas Vaicys, Michael Schulder, Leo J. Wolansky, and Frank B. Fromowitz

✓ Intracranial solitary plasmacytomas are extremely rare tumors and are often misdiagnosed preoperatively. The authors report the successful treatment of a patient who harbored such a tumor involving both the falx and tentorium; this is the second case reported. A 59-year-old woman suffered from a seizure disorder due to a falcotentorial lesion, which had been identified 3 years earlier and was thought at the time to be an en plaque meningioma. Most recently, the patient presented with symptoms of increased intracranial pressure and hemiparesis. Computerized tomography and magnetic resonance imaging of her head revealed progressive growth of the tumor. The patient underwent partial resection of the tumor and chemo- and radiation therapies. Intracranial plasmacytomas must always be included in a differential diagnosis because potential complete cure can be achieved using fairly conservative treatment modalities.

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Sudhakar Vadivelu, Leroy Sharer, and Michael Schulder

The authors present the case of a patient that demonstrates the long-standing use of megestrol acetate, a progesterone agonist, and its association with multiple intracranial meningioma presentation. Discontinuation of megestrol acetate led to shrinkage of multiple tumors and to the complete resolution of one tumor. Histological examination demonstrated that the largest tumor had high (by > 25% of tumor cell nuclei) progesterone-positive expression, including progesterone receptor (PR) isoform B, compared with low expression of PR isoform A; there was no evidence of estrogen receptor expression and only unaccentuated collagen expression. This is the first clinical report illustrating a causal relationship between exogenous hormones and modulation of meningioma biology in situ.

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Mitchell R. Gropper, Michael Schulder, Harry L. Duran, and Leo Wolansky

✓ There are only scattered case reports of intracranial tuberculosis in industrialized nations; brainstem tuberculoma is even more unusual, accounting for 2.5% to 8% of all intracranial tuberculoma. In developing nations, however, central nervous system tuberculosis (CNS-TB) is not rare and intracranial tuberculoma may account for 5% to 30% of all intracranial masses. The authors present two cases of CNS-TB with expansion to brainstem tuberculoma in patients who were undergoing treatment and had no known prior exposure to Mycobacterium tuberculosis.

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Rachel Pruitt, Alexander Gamble, Karen Black, Michael Schulder, and Ashesh D. Mehta

OBJECTIVE

Complications of laser interstitial thermal therapy (LITT) are underreported. The authors discuss how they have modified their technique in the context of technical and treatment-related adverse events.

METHODS

The Medtronic Visualase system was used in 49 procedures in 46 patients. Between 1 and 3 cooling catheters/laser fiber assemblies were placed, for a total of 62 implanted devices. Devices were placed using frameless stereotaxy (n = 3), frameless stereotaxy with intraoperative MRI (iMRI) (n = 9), iMRI under direct vision (n = 2), MRI alone (n = 1), or frame-based (n = 47) techniques. LITT was performed while monitoring MRI thermometry. Indications included brain tumors (n = 12), radiation necrosis (n = 2), filum terminale ependymoma (n = 1), mesial temporal lobe epilepsy (n = 21), corpus callosotomy for bifrontal epilepsy (n = 3), cavernoma (n = 1), and hypothalamic hamartomas (n = 6).

RESULTS

Some form of adverse event occurred in 11 (22.4%) of 49 procedures. These included 4 catheter malpositions, 3 intracranial hemorrhages, 3 cases of neurological deficit related to thermal injury, and 1 technical malfunction resulting in an aborted procedure. Of these, direct thermal injury was the only cause of prolonged neurological morbidity and occurred in 3 of 49 procedures. Use of frameless stereotaxy and increased numbers of devices were associated with significantly increased complication rates (p < 0.05). A number of procedural modifications were made to avoid complications, including the use of 1) frame-based catheter placement, a 1.8-mm alignment rod to create a track and titanium skull anchors for long trajectories to improve accuracy; 2) a narrow-gauge instrument for dural puncture and coregistration of contrast MRI with CT angiography to reduce intracranial hemorrhage; 3) general endotracheal anesthesia for posterior-placed skull anchors to reduce the likelihood of damage to the cooling catheter; 4) use of as few probes as possible to reduce complications overall; and 5) dose modification of thermal treatment and use of short (3-mm) diffusing tips to limit treatment when structures to be spared do not have intervening CSF spaces to act as heat sinks.

CONCLUSIONS

Laser ablation treatment may be used for a variety of neurosurgical procedures for patients with tumors and epilepsy. While catheter placement and thermal treatment may be associated with a range of suboptimal operative and postoperative courses, permanent neurological morbidity is less common. The authors' institutional experience illustrates a number of measures that may be taken to improve outcomes using this important new tool in the neurosurgical arsenal.