Intracranial hematolymphoid malignancies: A case series with molecular characterization.

OBJECTIVE: Central nervous system (CNS) manifestations of hematologic malignancies are uncommon and often have a poor prognosis. As hematologic neoplasms are typically chemotherapy- and radiotherapy-sensitive, surgical resection is usually not indicated; thus, opportunities for in-depth characterization of CNS hematologic tumors are limited. Here, we report four cases of rare intracranial hematologic tumors requiring surgical intervention, allowing for histopathologic and genomic characterization. METHODS: The clinical course, genetic perturbations, and histopathological features are described for a case of 1) primary marginal zone B-cell lymphoma of the dura as well as cases of brain metastases of 2) cutaneous T-cell lymphoma, 3) acute myeloid leukemia/myeloid sarcoma, and 4) multiple myeloma. Targeted DNA sequencing, fluorescence in situ hybridization, cytogenetic analysis, flow cytometry and immunohistochemical staining were used to assess the lesions. RESULT: Molecular and histopathological characterizations of four unusual presentations of hematolymphoid diseases involving the CNS are presented. Genetic abnormalities were identified in each lesion, including chromosomal aberrations and single nucleotide variants resulting in missense or nonsense mutations in oncogenes. CONCLUSIONS: Our case series provides insight into unique pathological phenotypes of hematologic neoplasms with atypical CNS involvement. We offer targets for future studies by identifying potentially pathogenic genetic variants in these lesions, as the full implications of the novel molecular abnormalities described remain unclear.

Basilar decompression via a far lateral transcondylar approach: technical note.

BACKGROUND: Treatments for symptomatic or unstable basilar invagination (BI) include posterior decompression, distraction/fusion, trans-nasal or trans-oral anterior decompression, and combined techniques, with the need for occipitocervical fusion based on the degree of craniocervical instability. Variations of the far lateral transcondylar approach are described in limited case series for BI, but have not been widely applied. METHODS: A single-institution, retrospective review of consecutive patients undergoing a far lateral transcondylar approach for odontoidectomy (± resection of the inferior clivus) followed by occipitocervical fusion over a 6-year period (1/1/2016 to 12/31/2021) is performed. Detailed technical notes are combined with images from cadaveric dissections and patient surgeries to illustrate our technique using a lateral retroauricular incision. RESULTS: Nine patients were identified (3 males, 6 females; mean age 40.2 ± 19.6 years). All patients had congenital or acquired BI causing neurologic deficits. There were no major neurologic or wound-healing complications. 9/9 patients (100%) experienced improvement in preoperative symptoms. CONCLUSIONS: The far lateral transcondylar approach provides a direct corridor for ventral brainstem decompression in patients with symptomatic BI. A comprehensive knowledge of craniovertebral junction anatomy is critical to the safe performance of this surgery, especially when using a lateral retroauricular incision.

Transsulcal parafascicular brain path-assisted approach to subcortical lesions: 2-dimensional operative video.

BACKGROUND: Approaches to subcortical lesions have traditionally been limited by the morbidity of white matter dissection and fixed blade retraction required to reach these targets. Visualization of deep surgical fields with a traditional operating microscope is also poor. Coordinated use of intra-operative image guidance, a tubular retractor (BrainPath®, Nico Corp, Indianapolis, Indiana), a high-definition exoscope (Vitom®, Karl Storz Endoscopy America, Inc, El Segundo, California), and a low-profile resection device (Myriad®, Nico Corp) facilitates atraumatic access to and resection of subcortical lesions including primary brain tumors, brain metastases, and intracerebral hemorrhages.[1] Use of pre-planned transsulcal and parafascicular trajectories based on magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) can further mitigate damage to white matter tracts with this technique. CASE DESCRIPTION: We herein present details of the transsulcal parafascicular BrainPath®-assisted approach to subcortical lesions and demonstrate the utility of this technique using two patient examples: a spontaneous deep left posterior temporal lobe hematoma in a 41-year-old male and a left hippocampal glioblastoma in a 54-year-old female. Key steps include selection of appropriate patients with non-skull base subcortical lesions, preoperative trajectory and tube depth planning based on MRI (including diffusion-weighted imaging and DTI), patient positioning and operating room setup to facilitate pre-planned trajectories and surgeon ergonomics, and use of low-profile instruments with a two-handed surgical technique. CONCLUSION: Given recent data demonstrating the utility of this approach for hematoma evacuation and a likely increased future usage of this technique,[2] surgeon familiarity with the above steps will be of increasing importance.

Surgical Relevance of the Suprameatal Tubercle During Superior Petrosal Vein-Sparing Trigeminal Nerve Microvascular Decompression.

BACKGROUND: An enlarged suprameatal tubercle (SMT) can obscure visualization of the trigeminal nerve and require removal during microvascular decompression (MVD) surgery, especially when the superior petrosal vein (SPV) complex is preserved. OBJECTIVE: To define the incidence and important variables affecting the need for SMT removal with an SPV-sparing trigeminal nerve MVD. METHODS: Retrospective single-institution review identified patients who underwent a first-time, SPV-sparing MVD for trigeminal neuralgia (TGN) over a 26-mo period. SMT length (SMT-L), SMT width (SMT-W), and peri-trigeminal cerebellopontine cisternal thickness (CT) were measured from axial high-resolution magnetic resonance images. Need for SMT removal and use of endoscopic assistance was recorded. Data were analyzed using unpaired t-tests, and receiver operating characteristic (ROC)/area under the curve testing. RESULTS: A total of 43 MVD surgeries for TGN on 42 patients (mean age 52.7 ± 14.4 yr) were analyzed. Mean SMT-L, SMT-W, and CT were 9.8 ± 1.6, 2.0 ± 0.8, and 4.2 ± 1.5 mm, respectively. SMT removal via drilling was required in 4/43 cases (9.3%). Endoscopic assistance was used in 3 cases (2 SMT removed and 1 SMT preserved). SMT-W was the biggest predictor of the need for SMT removal on ROC analysis (area under the curve 0.97, 0.92-1.0 95% CI). The combined thresholds of SMT-W ≥ 3.2 mm and CT ≤ 3.5 mm demonstrated 100% sensitive and 100% specificity for the need to remove the SMT on optimal cutoff analysis. CONCLUSION: SMT drilling is necessary in nearly 10% of SPV-sparing MVDs for TGN. The combination of SMT width and cerebellopontine cistern thickness is predictive of the need for SMT removal.

Immune therapeutic strategies using optimal controls with L1 and L2 type objectives.

Therapeutic strategies to correct an excessive immune response to pathogenic infection is investigated as an optimal control problem. The control problem is formulated around a four dimensional mathematical model describing the inflammatory response to a pathogenic insult with two therapeutic control inputs which have either a direct pro- or anti-inflammatory effect in the given system. We use Pontryagin's maximum principle and discuss necessary optimality conditions. We consider both an L1 type objective functional as well as an L2 type objective. For the former, the presence of singular control will be addressed. For each case, numerical simulations using a nonlinear programming optimization solver to acquire different drug treatment strategies are presented and discussed. The results provide insight for possible treatment strategies and the methods could be a relevant tool for future practice to assist in better prediction of clinical outcomes and subsequently better treatment for patients.

The Safety and Feasibility of Image-Guided BrainPath-Mediated Transsulcul Hematoma Evacuation: A Multicenter Study.

BACKGROUND: Subcortical injury resulting from conventional surgical management of intracranial hemorrhage may counteract the potential benefits of hematoma evacuation. OBJECTIVE: To evaluate the safety and potential benefits of a novel, minimally invasive approach for clot evacuation in a multicenter study. METHODS: The integrated approach incorporates 5 competencies: (1) image interpretation and trajectory planning, (2) dynamic navigation, (3) atraumatic access system (BrainPath, NICO Corp, Indianapolis, Indiana), (4) extracorporeal optics, and (5) automated atraumatic resection. Twelve neurosurgeons from 11 centers were trained to use this approach through a continuing medical education-accredited course. Demographical, clinical, and radiological data of patients treated over 2 years were analyzed retrospectively. RESULTS: Thirty-nine consecutive patients were identified. The median Glasgow Coma Scale (GCS) score at presentation was 10 (range, 5-15). The thalamus/basal ganglion regions were involved in 46% of the cases. The median hematoma volume and depth were 36 mL (interquartile range [IQR], 27-65 mL) and 1.4 cm (IQR, 0.3-2.9 cm), respectively. The median time from ictus to surgery was 24.5 hours (IQR, 16-66 hours). The degree of hematoma evacuation was ≥90%, 75% to 89%, and 50% to 74% in 72%, 23%, and 5.0% of the patients, respectively. The median GCS score at discharge was 14 (range, 8-15). The improvement in GCS score was statistically significant ( P < .001). Modified Rankin Scale data were available for 35 patients. Fifty-two percent of those patients had a modified Rankin Scale score of ≤2. There were no mortalities. CONCLUSION: The approach was safely performed in all patients with a relatively high rate of clot evacuation and functional independence.

Mortality and cost of radiation therapy for oesophageal cancer according to hospital accreditation level: a nationwide population-based study.

This study examined and analysed the relationship between the cost-effectiveness and outcome of radiotherapy for oesophageal cancer among hospitals with varying accreditation levels. We selected 428 oesophageal cancer patients from medical and non-medical centres using the National Health Insurance Research Database, which is maintained by the Taiwanese National Health Research Institutes, and compared their medical expenditure and the outcome of their radiotherapy treatment. In this study cohort of patients with oesophageal cancer, 278 patients were treated in medical centres (mean age: 60.1 years) and 150 patients were treated in non-medical centres (mean age: 62.0 years, P = 0.16). The medical centre group exhibited significantly lower medical expenses, mortality and risk of death compared with the non-medical centre group (adjusted hazard ratio = 1.38, 95% confidence interval = 1.11-1.71). Our study determined that radiotherapy for oesophageal cancer costs significantly less, and medical centres had lower mortality rates than non-medical centres. These findings could provide professional organisations and healthcare policy makers with essential information for allocation of resources.

Synergy of local, regional, and systemic non-specific stressors for host defense against pathogens.

The immune brinksmanship conceptual model postulates that many of the non-specific stressful components of the acute-phase response (e.g. fever, loss of appetite, iron and zinc sequestration) are host-derived systemic stressors used with the "hope" that pathogens will be harmed relatively more than the host. The concept proposes that pathogens, needing to grow and replicate in order to invade their host, should be relatively more vulnerable to non-specific systemic stress than the host and its cells. However, the conceptual model acknowledges the risk to the host in that the gamble to induce systemic self-harming stress to harm pathogens may not pay off in the end. We developed an agent-based model of a simplified host having a local infection to evaluate the utility of non-specific stress, harming host and pathogen alike, for host defense. With our model, we explore the benefits and risks of self-harming strategies and confirm the immune brinksmanship concept of the potential of systemic stressors to be an effective but costly host defense. Further, we extend the concept by including in our model the effects of local and regional non-specific stressors at sites of infection as additional defenses. These include the locally hostile inflammatory environment and the stress of reduced perfusion in the infected region due to coagulation and vascular leakage. In our model, we found that completely non-specific stressors at the local, regional, and systemic levels can act synergistically in host defense.

Microvascular decompression of the vestibulocochlear nerve for disabling positional vertigo: the House Ear Clinic experience.

OBJECTIVE: To review characteristics of and outcome in patients undergoing microvascular decompression of the vestibulocochlear nerve. Patients studied had a diagnosis of disabling positional vertigo caused by a vascular loop compressing the VIIIth cranial nerve. STUDY DESIGN: Retrospective chart review and telephone interview. SETTING: Private practice tertiary neurotologic referral center. PATIENTS: Twenty patients with disabling positional vertigo underwent 25 retrosigmoid craniotomies for microvascular decompression between November 1990 and June 1999. The 4 men and 16 women ranged in age from 30 to 71 years (mean age, 46 yr). MAIN OUTCOME MEASURES: Charts were reviewed and patients were contacted by telephone and asked to rate severity of symptoms (tinnitus and dizziness) on a 4-point scale (none = 1, mild = 2, moderate = 3, and severe = 4) before and after surgery. They were also asked to rate their overall disability from their symptoms on the six-point scale established by the American Academy of Otolaryngology-Head and Neck Surgery. Preoperative and postoperative four-frequency (500 Hz, 1 kHz, 2 kHz, and 4 kHz) pure-tone average and speech discrimination scores were calculated and compared. Complications of surgery are also reported. RESULTS: Postoperative tinnitus score and dizziness score showed significant improvement from preoperative scores (p < or = 0.047 and p < or = 0.001, respectively), with 80% of patients improved in dizziness rating; 85% improved in their overall disability rating, and the difference from preoperative to postoperative was significant (p < or = 0.001). The mean postoperative pure-tone averages (15.4 dB) and speech discrimination scores (99%) did not differ from preoperative scores (11.9 dB and 98%). One patient lost all vestibular function in the operated ear (hearing remained intact) as the only complication of surgery. When asked, 83% of patients responded that they would have the surgery again. CONCLUSIONS: Diagnosing disabling positional vertigo secondary to vascular compression of the VIIIth cranial nerve remains the clinical challenge; a clear history plus air-contrast computed tomographic or magnetic resonance imaging make the diagnosis. Microvascular decompression of the vestibulocochlear nerve is a safe and effective operation for these carefully selected patients.

Exposure of mice to topical bovine thrombin induces systemic autoimmunity.

Bovine thrombin is used as an aid to hemostasis in medical and surgical procedures. At least 500,000 Americans are exposed to this therapeutic annually and reports suggest that exposure is associated with the development of autoreactive antibodies. To determine whether bovine thrombin can induce pathological autoimmunity we exposed nonautoimmune-prone galactose-alpha1-3-galactose-deficient mice to the two bovine thrombin preparations currently approved for use in the United States. We found that, like humans exposed to bovine thrombin, mice developed an immune response against the therapeutic and the xenogeneic carbohydrate galactose-alpha1-3-galactose, and some mice developed autoantibodies against clotting factors. Further, unexpectedly, a single exposure to this therapeutic also induced autoimmunity with features characteristic of systemic lupus erythematosus including antibodies against nuclear antigens, native DNA, double-stranded DNA, and cardiolipin. High levels of these autoantibodies correlated with glomerulonephritis in all mice evaluated. This autoimmune syndrome was detected in mice 15 weeks after a secondary exposure to bovine thrombin and female mice were found to develop the syndrome at a significantly greater frequency than males. Thus, these studies indicate that exposure to bovine thrombin preparations can induce a pathological systemic autoimmune syndrome with lupus-like serology.

Early proactive management of vestibular schwannomas in neurofibromatosis type 2.

OBJECTIVE: The treatment of patients with neurofibromatosis Type 2 has always been challenging for neurosurgeons and neurotologists. Guidelines for appropriate management of this devastating disease are controversial. METHODS: A retrospective study of 28 patients with neurofibromatosis Type 2 who underwent 40 middle fossa craniotomies for excision of their acoustic tumors is reported. Eleven patients underwent bilateral procedures. The study focused on hearing preservation and facial nerve results for this group of patients. The 16 male patients and 12 female patients ranged in age (at the time of surgery) from 10 to 70 years, with a mean age of 22.6 years. The mean tumor size was 1.1 cm (range, 0.5-3.2 cm), and the majority of tumors were less than 1.5 cm. RESULTS: Measurable hearing was preserved in 28 ears (70%), with 42.5% being within 15 dB pure-tone average and 15% speech discrimination score of preoperative levels. In 55% of cases there was no change in the hearing class, as defined by the American Academy of Otolaryngology-Head and Neck Surgery. Of the 11 patients who underwent bilateral operations, 9 (82%) retained some hearing bilaterally. After 1-year follow-up periods (mean, 12.8 mo), 87.5% of patients exhibited normal facial nerve function (House-Brackmann Grade I). CONCLUSION: Early surgical intervention to treat acoustic tumors among patients with neurofibromatosis Type 2 is a feasible treatment strategy, with high rates of hearing and facial nerve function preservation.

Intraoperative computerized tomography scanning to assess the adequacy of decompression in anterior cervical spine surgery.

OBJECT: The purpose of this study was to improve the accuracy of bone removal during anterior spinal surgery. Intraoperative computerized tomography (CT) scanning was used to assess the success of bone resection and permit immediate correction in the event of inadequate bone removal. METHODS: The Phillips Tomoscan M was used to obtain preoperative cervical scans before and after cervical bone resection was complete. The completeness of bone removal was assessed by the operating neurosurgeon by reviewing the postresection CT scan. If the bone removal was deemed inadequate, additional bone was removed using a high-speed drill. A CT scan was obtained after each subsequent decompression until adequate bone removal was achieved. In 31 patients undergoing anterior cervical decompression intraoperative CT scanning was performed. Nineteen patients underwent corpectomy and 12 discectomy. Of the 31 patients, assessment of intraoperative CT scans obtained in 17 indicated further bone removal was required. CONCLUSIONS: Intraoperative CT scanning to monitor bone removal during anterior cervical surgery is a valuable tool to ensure the adequacy of surgery.

Cranial base surgical techniques for large sphenocavernous meningiomas: technical note.

OBJECTIVE: Large meningiomas arising from the dura covering the sphenoid ridge present surgical challenges because of frequent involvement of the carotid artery and its branches, the optic nerve and tract, the superior orbital fissure, and cavernous sinus structures. To circumvent the inherent difficulties of a traditional approach strategy, cranial base approaches were applied to: 1) isolate and interrupt the major blood supply as an initial step, 2) minimize brain retraction, and 3) isolate the neurovascular structures exiting the tumor at the cranial base to protect and better separate them. METHODS: Six patients were treated with such a strategy in the past 2 years (five women and one man, ages 34-69 yr). All tumors measured at least 5 cm in their greatest diameter and arose at the sphenoid ridge. All tumors extended posteriorly to involve the cavernous sinus to varying degrees. In two patients a frontotemporal bone flap was used; in two patients, a transzygomatic approach was used; and in the remaining two patients, an orbitozygomatic strategy was used. Extensive bone removal at the cranial base was performed in all cases. RESULTS: Four patients had gross total resections, and two were subtotal owing to invasion of the cavernous sinus or the middle cerebral artery. There were no permanent cranial nerve deficits; however, two patients sustained transient IIIrd nerve paresis. Two patients postoperatively developed transient cerebral edema that required intensive treatment. All six patients had good outcomes, resuming independent activity by 3 months after surgery. CONCLUSION: Contemporary cranial base surgical techniques have a role in the treatment of large sphenoid ridge meningiomas. These strategies result in safe resection with low morbidity and obviate the need in most cases for preoperative embolization. The anatomic foundation for using these approaches is discussed.

Extended transbasal approach: anatomy, technique, and indications.

Appropriate indications for the transbasal approach have not been clearly established. The focus of this study is to determine the feasibility of maximal exposure of the clivus and surrounding regions via this strategy. Further, we sought to determine the key anatomical landmarks and morphometric data necessary for safe, radical exposure. In 20 injected cadaveric specimens, anatomical observations were made grossly and microscopically with 4-40 x magnification. The three basic variations of the transbasal craniotomy were compared with regard to surgical exposure. Maximum exposure of the ventral clivus could be obtained by total ethmoidectomy and sphenoidectomy through the extensive transbasal craniotomy. The lateral limits of exposure were found to be the optic nerves, intracavernous carotid arteries, and hypoglossal canals. Inferiorly, the foramen magnum is the limit of exposure. Morphometric measurements were determined between the key landmarks and were found helpful in subsequent dissections due to the lack of bony structures in relation to neural and vascular structures within the bone. The keys to optimizing the transbasal approach are beyond the simple initial steps of the craniotomy. Maximal exposure from the suprasellar compartment to the foramen magnum is possible via the extended transbasal approach.

Context modulates effects of nicotine abstinence on human cooperative responding.

The effects of ad libitum smoking, abstinence, and 0-, 2-, and 4-mg nicotine gum on human cooperative responding were examined. Participants were provided the opportunity to respond cooperatively or independently to episodes initiated by a computer-simulated other person. Participants could also initiate episodes that ostensibly provided the other person the opportunity to respond cooperatively or independently of the participant. Working cooperatively added points to both the participant's and other person's counters. Working independently added points only to the participant's counter. Results demonstrated that abstinence decreased cooperative responses during episodes initiated by the computer-stimulated other person. Relative to abstinence and placebo gum conditions, ad libitum smoking and administration of 2- and 4-mg nicotine gum increased these cooperative responses. No gender differences were observed. The number of cooperative episodes initiated by the participants was not affected significantly by the smoking or gum conditions. Nicotine increased reports of vigor and decreased abstinence-engendered reports of depression, anger, confusion, and tension. The difference in the effects of nicotine abstinence on the 2 classes of cooperative responding demonstrates that the social contingency mediates the behavioral effects of abstinence.

The Quilty lesion enigma: focal apoptosis/necrosis and lymphocyte subsets in human cardiac allografts.

Quilty lesions, as first described by Billingham in 1981, or 'Quilty Effect' (QE) are distinct endomyocardial mononuclear cell infiltrates that have been observed in human heart transplant recipients, as well as in experimental models of heart transplantation. In the present investigations, the pattern and extent of apoptosis (programmed cell death) and myocyte necrosis, as well as specific lymphocyte subsets in Quilty lesions was assessed. Endomyocardial biopsies obtained from 13 patients at 10-3362 days post-transplant were examined. Apoptosis, as identified by DNA nick end-labeling, was found in myocytes at the periphery of Quilty lesions in 11 of 13 cases (85%), and 'early' stages of myocyte necrosis, as demonstrated by specific staining with alpha light chain myosin monoclonal antibodies (mAb), was observed at the same sites in 10 of 13 cases (77%) of both Quilty type A and type B lesions. Apoptosis was not identified in the lymphocyte infiltrates of any of the lesions examined. Lymphocyte subsets were characterized using mAb for T cell receptor (CD3), for helper/inducer T cells (CD4), for cytotoxic/suppressor T cells (CD8) and for mature B cells (CD20). Immunostaining revealed separate clusters of T lymphocytes with less prevalent B cells within the Quilty lesions. CD4+ cells were found in larger numbers than CD8+ cells in all cases. Non-B, non-T large lymphocytes were occasionally present. Except for the extent of the cellular infiltrate, no major cytochemical lymphocyte distribution differences were found between Quilty type A and B lesions. Myocyte apoptosis and early necrosis at the periphery of Quilty lesions suggest that early myocyte injury occurring in B lesions may represent initial or 'abortive stages' of cardiac allograft rejection. Why these lesions do not progress to overt rejection indeed warrant further detailed studies.

Neurotopographic considerations in the microsurgical treatment of small acoustic neurinomas.

OBJECT: The authors studied the relationships between tumor size, location, and topographic position relative to the intact facial nerve bundles in acoustic neurinomas to determine the influence of these factors on hearing preservation postoperatively. Consistent topographic relationships were found. METHODS: Four hundred fifty-two patients with acoustic neurinoma treated via a retrosigmoid approach were analyzed with respect to hearing preservation and facial nerve function. One hundred fifteen tumors were identified as small and were categorized as Grades I and II. Patients with Grade I tumors, that is, purely intracanalicular lesions, all had good hearing preoperatively, defined by a less than 50-dB pure tone average and 50% speech discrimination score. All 14 Grade I tumors were removed, resulting in preservation of the patient's hearing by these criteria. There were no particular topographic anatomical relationships associated with these tumors that affected hearing preservation. Grade II tumors, defined as those protruding into the cerebellopontine angle without contacting the brainstem, were found in 101 patients and were divided by size into two grades: IIA (< 1 cm) and IIB (1-1.8 cm). In 90 patients with Grade IIA tumors, 72 (89%) of 81 who had preserved hearing preoperatively maintained it postoperatively, and in the 11 patients with Grade IIB tumors, six of whom had good hearing preoperatively, four (67%) had preserved hearing postoperatively. Six morphological types were identified based on their neurotopographic relationships to the elements of the vestibulocochlear nerve. CONCLUSIONS: Hearing preservation postsurgery by tumor type was as follows: 1A, 92%; 1B, 88%; 1C, 100%; 2A, 83%; 2B, 92%; and 3, 57%. Combined, this represents a hearing preservation rate of 87% after surgical treatment of Grade II acoustic neurinomas. Full nerve function was maintained in 88% of patients with anatomically preserved facial nerves in both Grade I and II tumors. The remaining 12% of patients retained partial function of the facial nerve. Two patients in the series lost anatomical integrity of the nerve due to surgery.

The surgical management of trigeminal neuromas.

OBJECTIVE: Trigeminal neuromas are rare tumors that may involve any part of the nerve complex, including peripheral divisions of the nerve. These rare lesions are treated primarily surgically. We present our series of 38 patients who were treated surgically since 1981, with special emphasis on surgical approach. METHODS: We have surgically treated 38 patients with 39 trigeminal neuromas since 1981. This series of patients was reviewed with regard to clinical presentation, tumor characteristics, surgical approach, and outcome. RESULTS: Sixteen women and 22 men (mean age, 48 yr) all presented with some abnormality of trigeminal dysfunction. Twenty-eight patients presented with trigeminal hypesthesia, 10 with hypesthesia also had facial pain, 3 presented with only facial pain, and 7 presented with diplopia. Eighteen patients had tumors originating from the ganglion, nine from the posterior fossa nerve root, two from the ophthalmic division, and one from the mandibular division, and nine had tumors involving both posterior and middle fossae (dumbbell type). Eighteen tumors were large (>3 cm), 16 were medium sized (2-3 cm), and 5 were small (<2 cm). Tumor location was the prime determinant of surgical approach. Patients with peripheral and ganglion type lesions were treated via an entirely extradural temporopolar approach. Lesions confined to the posterior fossa were approached via a lateral suboccipital approach. Dumbbell-shaped lesions required a combined petrosal strategy. Total resection of tumor was accomplished in 30 patients. Three patients with subtotal resection displayed malignant histology. Postoperatively, 30 patients remained with some degree of trigeminal hypesthesia, two had facial pain (one persistent and one new), and five were left with total trigeminal anesthesia. Four patients were relieved of diplopia, five were relieved of headache, and two were relieved of ataxia. There were no perioperative deaths. CONCLUSION: Trigeminal neuroma is a surgically treatable disease that may be operated on, in many cases, via an entirely extradural approach. These lesions may be successfully resected with low morbidity and a very low rate of recurrence.

Anatomic position of the asterion.

OBJECTIVE: The asterion is defined as the junction of the lambdoid, parietomastoid, and occipitomastoid sutures. The asterion has been used as a landmark in lateral approaches to the posterior fossa. However, its reliability as a landmark comes into question considering the apparent variability of its position. This study was performed to determine the reliability of the asterion as a surgical landmark. METHODS: One hundred dried skulls were obtained for study. A 2-mm drill hole was placed at the asterion on each side. The position of the drill hole on the inner surface of the skull was next determined and recorded. RESULTS: The asterion was located over the posterior fossa dura in 32% on the right and 25% on the left. Its position was over the transverse or sigmoid sinus complex in 61% on the right and 66% on the left. The landmark was located above the transverse-sigmoid sinus complex in 7% on the right and 9% on the left. CONCLUSIONS: The asterion is not a strictly reliable landmark in terms of locating the underlying posterior fossa dura. Its location is very often directly over the transverse-sigmoid sinus complex. Burr holes placed at the asterion may often open the bone directly over the sinus, leading to potential damage.