Comparison of radiosurgery and conventional surgery for the treatment of glomus jugulare tumors

Molecular genetics of paragangliomas of the skull base and head and neck region: implications for medical and surgical management

Paragangliomas are rare, slow-growing tumors that frequently arise in the head and neck, with the carotid bodies and temporal bone of the skull base being the most common sites. These neoplasms are histologically similar to pheochromocytomas that form in the adrenal medulla and are divided into sympathetic and parasympathetic subtypes based on functionality. Skull base and head and neck region paragangliomas (SHN-PGs) are almost always derived from parasympathetic tissue and rarely secrete catecholamines. However, they can cause significant morbidity by mass effect on various cranial nerves and major blood vessels. While surgery for SHN-PG can be curative, postoperative deficits and recurrences make these lesions challenging to manage. Multiple familial syndromes predisposing individuals to development of paragangliomas have been identified, all involving mutations in the succinate dehydrogenase complex of mitochondria. Mutations in this enzyme lead to a state of “pseudohypoxia” that upregulates various angiogenic, survival, and proliferation factors. Moreover, familial paraganglioma syndromes are among the rare inherited diseases in which genomic imprinting occurs. Recent advances in gene arrays and transcriptome/exome sequencing have identified an alternate mutation in sporadic SHN-PG, which regulates proto-oncogenic pathways independent of pseudohypoxia-induced factors. Collectively these findings demonstrate that paragangliomas of the skull base and head and neck region have a distinct genetic signature from sympathetic-based paragangliomas occurring below the neck, such as pheochromocytomas. Paragangliomas serve as a unique model of primarily surgically treated neoplasms whose future will be altered by the elucidation of their genomic complexities. In this review, the authors present an analysis of the molecular genetics of SHN-PG and provide future directions in patient care and the development of novel therapies.

Complex glomus jugulare tumor: management issues

Glomus tumors are rare and locally aggressive, vascular paragangliomas of the skull base. Tumors may progress to cause lower cranial nerve palsies and involve the major vascular structure in the skull base, and thus pose very difficult surgical challenges. One such case is presented, the management problems in such "complex glomus jugulare" tumors are discussed, and the literature reviewed.

Lower cranial nerves function after surgical treatment of Fisch Class C and D tympanojugular paragangliomas

The aim of this study was to report the postoperative lower cranial nerves (LCNs) function in patients undergoing surgery for tympanojugular paraganglioma (TJP) and to evaluate risk factors for postoperative LCN dysfunction. A retrospective case review of 122 patients having Fisch class C or D TJP, surgically treated from 1988 to 2012, was performed. The follow-up of the series ranged from 12 to 156 months (mean, 39.4 ± 32.6 months). The infratemporal type A approach was the most common surgical procedure. Gross total tumor removal was achieved in 86% of cases. Seventy-two percent of the 54 patients with preoperative LCN deficit had intracranial tumor extension. Intraoperatively, LCNs had to be sacrificed in 63 cases (51.6%) due to tumor infiltration. Sixty-six patients (54.09%) developed a new deficit of one or more of the LCNs. Of those patients who developed new LCN deficits, 23 of them had intradural extension. Postoperative follow-up of at least 1 year showed that the LCN most commonly affected was the CN IX (50%). Logistic regression analysis showed that intracranial transdural tumor extension was correlated with the higher risk of LCN sacrifice (p < 0.05). Despite the advances in skull base surgery, new postoperative LCN deficits still represent a challenge. The morbidity associated with resection of the LCNs is dependent on the tumor's size and intradural tumor extension. Though no recovery of LCN deficits may be expected, on long-term follow-up, patients usually compensate well for their LCNs loss.

Stereotactic radiosurgery for the treatment of Glomus Jugulare Tumors

BACKGROUND

The glomus jugulare tumor is a slowly growing benign neoplasm originating from neural crest. There is a high morbidity associated with surgical resection of glomus jugulare. Radiosurgery play a relevant role as a therapeutic option in these tumors and its use has grown in popularity. The authors describe a retrospective series of 15 patients and reviewed the literature about the glomus jugulare tumors.

METHODS

We reviewed retrospectively the data of 15 patients treated with stereotactic linear accelerator stereotactic radiosurgery (LINAC) radiosurgery between 2006 and 2011.

RESULTS

The average tumor volume was 18.5 cm(3). The radiation dose to the tumor margin ranged between 12 and 20 Gy. The neurological status improved in three patients and remained unchanged in 12 patients. One patient developed a transient 7(th) nerve palsy that improved after clinical treatment. All tumors remained stable in size on follow-up with resonance magnetic images.

CONCLUSIONS

The radiosurgery is a safe and effective therapy for patients with glomus jugulare tumor. Despite the short follow-up period and the limited number of patients analyzed, we can infer that radiosurgery produce a tumor growth control with low morbidity, and may be used as a good option to surgical resection in selected cases.

Successful management of a catecholamine-secreting glomus jugulare tumor with radiosurgery alone

Secretory glomus jugulare tumors are often resected surgically to control the systemic effects of the catecholamines they produce. This involves complex skull base surgery, which carries significant risks and frequent morbidity. Stereotactic radiosurgery (SRS) is a recently recognized treatment for glomus jugulare tumors, though little is known about its use in secretory tumors. Case Report A young fit patient with a catecholamine-secreting glomus jugulare tumor was treated with SRS alone and over the following 37 months her urinary catecholamine excretion fell to near normal levels, and serial magnetic resonance imaging (MRI) confirmed a reduction in tumor volume. Discussion Radiosurgery is an accepted treatment for glomus jugulare tumors and is now readily available to skull base surgeons. In this case a catecholamine-secreting tumor was successfully controlled with radiosurgery alone. Further research and long-term follow-up will determine the role of this treatment in the nonsurgical management of secreting glomus jugulare tumors.

Robotic stereotactic radiosurgery in patients with unresectable glomus jugulare tumors

We evaluated the treatment results of robotic stereotactic radiosurgery (SRS) in our patients with unresectable glomus jugulare tumors (GJTs). The medical charts of fourteen patients with GJT, who were treated with robotic SRS, were retrospectively evaluated. The gross tumor volume was described as the clinical target volume. The median dose to the tumor was 25 Gy in median 5 fractions. The dose was normalized to 80% isodose line. All patients were evaluated for tumor growth and clinical outcome every 6 months in the first 2 years and then annually. Median follow-up was 39 months (range, 7-60 months). Lesions were stable in 8 patients, and tumor regression was observed in 6 patients. We did not observe any treatment related toxicity in our patients. In conclusion, according to our early experience, robotic SRS seems to be successful treatment option in the management of unresectable GJTs.

Stereotactic radiosurgery as the primary treatment for new and recurrent paragangliomas: is open surgical resection still the treatment of choice?

OBJECTIVE

Paragangliomas (PGs) or glomus tumors are rare, and publications comparing treatment alternatives are few. We sought to analyze our experience with stereotactic radiosurgery (SRS), review the literature, and develop treatment guidelines.

METHODS

We retrospectively examined the outcomes of 41 PGs in 36 patients treated with SRS at Stanford. Our data from medical records, telephone interviews, and imaging studies were combined with previously reported SRS data and compared to results following other treatments.

RESULTS

With a median clinical follow-up of 4.8 years (3.9 years radiographic), local control was 100%. Complications included increase in preexistent vertigo in one patient and transient cranial neuropathies in two patients. Published surgical series describe a lower local control rate as well as more frequent and severe complications. Published radiation therapy (RT) series document a slightly lower local control rate than SRS, but SRS can be delivered more quickly and conveniently. Open surgery and other combinations of treatments appear to be required for several subpopulations of PG patients.

CONCLUSIONS

We feel that SRS should be the primary treatment for most new and recurrent PGs. Even some very large PGs are appropriate for SRS. RT remains an appropriate option in some centers, especially those where SRS is not available. PGs occurring in the youngest patients, catecholamine secreting PGs, and PGs causing rapidly progressing neurologic deficits may be more appropriate for open resection. Metastatic PGs may benefit from combinations of chemotherapy and SRS or RT. Treatment guidelines are proposed.

Jugular and vagal paragangliomas: Systematic study of management with surgery and radiotherapy

BACKGROUND

The definitive treatment for head and neck paraganglioma (PG) is surgical excision. Unfortunately, surgery, particularly of vagal paraganglioma (VPG; "glomus vagale") and foramen jugulare ("glomus jugulare") tumors, may be complicated by injuries to the lower cranial nerves, a high price to pay for treatment for a benign tumor. Alternatively these tumors may be followed without treatment, or irradiated. The purpose of this review was to compare the existing evidence concerning the efficacy and safety of surgery, external beam radiotherapy (EBRT), and stereotactic radiosurgery (SRS), for jugular paragangliomas (JPGs) and VPGs.

METHODS

Relevant articles were reviewed using strict criteria for systematic searches. Forty-one surgical studies met the criteria which included 1310 patients. Twenty articles including 461 patients treated with EBRT, and 14 radiosurgery studies comprising 261 patients were also evaluated. Results were compared between treatment modalities using analysis of variance (ANOVA) tests.

RESULTS

A total of 1084 patients with JPGs and 226 VPGs were treated with different surgical procedures. Long-term control of the disease was achieved in 78.2% and 93.3% of patients, respectively. A total of 715 patients with JPG were treated with radiotherapy: 461 with EBRT and 254 with SRS. Control of the disease with both methods was obtained in 89.1% and 93.7% of the patients, respectively. The treatment outcomes of a JPG treated with surgery or radiotherapy were compared. Tumor control failure, major complication rates, and the number of cranial nerve palsies after treatment were significantly higher in surgical than in radiotherapy series. The results of SRS and EBRT in JPGs were compared and no significant differences were observed in tumor control. Because only 1 article reported on the treatment of 10 VPGs with radiotherapy, no comparisons with surgery could be made. Nevertheless, the vagus nerve was functionally preserved in only 11 of 254 surgically treated patients (4.3%).

CONCLUSION

There is evidence that EBRT and SRS offer a similar chance of tumor control with lower risks of morbidity compared with surgery in patients with JPGs. Although the evidence is based on retrospective studies, these results suggest that surgery should be considered only for selected cases, but the decision should be individual for every patient.

Jugular foramen paragangliomas: management, outcome and avoidance of complications in a series of 75 cases

Jugular foramen paragangliomas are rare skull base tumours posing multiple complex diagnostic and management problems. We did a study to evaluate surgical technique, outcome and complications in 75 cases of tumours treated by multidisciplinary approach (i.e. combined neurosurgery, neuroradiology, ear, nose and throat surgery and intensive care unit team). Retrospective study on 75 consecutive patients with jugular foramen paragangliomas treated surgically from 1989 to 2005. Preoperative balloon occlusion test was performed in all patients as well as embolization (100%). A combined limited infratemporal and juxtacondylar approach was used in all patients. Gross total resection was achieved in 59 patients (78.7%). The most common complication was represented by lower cranial nerve deficits in five patients (6.6%), which was only temporary in three. Postoperative facial nerve weakness occurred in five cases (6.6%) and resolved in three of them. The remaining two patients underwent facial nerve reconstruction by hypoglossal/facial nerve anastomosis. Four patients (5.3%) had a postoperative cerebrospinal fluid leak, which was successfully treated by lumbar drainage. Two patients (2.7%) died because of complications related to surgical injury of lower cranial nerves: one patient developed aspiration pneumonia and septicemia and the second one developed a large cervico-bulbar hematoma that led to severe respiratory distress and ultimately global cerebral hypoxia. Paragangliomas are rare and complex skull base lesions that may be managed with low morbidity and mortality if a multidisciplinary approach is considered. Facial and lower cranial nerve postoperative deficits can be limited.

Treatment of recurrent and residual glomus jugulare tumors

Residual and recurrent glomus jugulare tumors are rare but challenging. Treatment options include microsurgical resection, stereotactic radiotherapy, a combination of modalities, and "observation." Choice of treatment must be made on a case-by-case basis, considering patient age, health status, location and size of tumor, status of the lower cranial nerves, and, of course, patient desire. Surgery is preferred when total resection of the tumor with preservation of function is deemed achievable. When function of the lower cranial nerves has been compromised, total surgical resection may also be possible, provided that the patient's health allows it. Cases where function is still preserved despite presence of a large tumor are more challenging, and a combination modality may be most effective. The goal of treatment is to provide tumor control with low morbidity. Current surgical techniques and the availability of stereotactic radiotherapy make this possible in the majority of cases.

Evolving concepts in the management of jugular paraganglioma: a comparison of radiotherapy and surgery in 88 cases

Surgery for jugular paraganglioma (PGL) tumors often results in the acquisition of neurological deficits where none had been present previously. This has a significant impact on the quality of life. Radiotherapy is a recognized alternative therapy. The aim of this study was to compare the results of radiotherapy and surgery for the management of jugular PGL in terms of function and tumor control to define a treatment algorithm. We conducted a retrospective and comparative analysis of the treatment of 41 patients by conventional radiotherapy and 47 patients by surgery via tertiary referral at an academic medical center. Forty-seven patients with type C and/or D jugular PGLs (mean age, 46 years) underwent surgery after endovascular embolization between 1984 and 1998 using an infratemporal fossa type A approach. The facial nerve was transposed in 18 patients. An adjunctive neurosurgical procedure was required in 14 patients. Mean follow-up was 66 months (range, 17 months to 14 years). Forty-one patients with type C jugular PGLs (mean age, 59.5 years) were treated by external beam or conformational radiotherapy between 1988 and 2003 with a total mean dose of 45 Gy (range, 44 to 50 Gy). Mean follow-up was 50 months (range, 18 months to 13 years). The primary outcome measures were tumor control and cranial nerve status. Surgical resection, total or subtotal, yielded an overall 86% rate of either cure or tumor stabilization. Radiotherapy achieved local control in 96% of patients. For surgery, the main postoperative complications were dysphagia, aspiration, and facial paralysis. Patients treated by radiotherapy developed minor disabilities. We concluded that radiotherapy and surgery achieve similar oncologic outcomes, but the former achieves tumor control with less morbidity. Our data favor radiotherapy as treatment for jugular PGLs, but we acknowledge that the aims of these two treatment modalities are different, namely, eradication of tumor by surgery versus stabilization of tumor with radiotherapy. The search for the better quality of life has to be weighed against the uncertainty of the long-term behavior of the tumor.

Rehabilitation after treatment for jugular foramen lesions

Swallowing problems following jugular foramen surgery are more common than is often acknowledged and affect up to a third of our patients. They have a significant effect on quality of life. We have become more proactive in this respect and anticipate these problems before they become established. In this article we present our management protocol that has evolved over the past 30 years as a result of our experience treating 134 glomus jugulare tumors. Our current protocol involves a thorough preoperative assessment of swallowing. After jugular foramen surgery, patients undergo further evaluation using fiberoptic endoscopic evaluation of swallowing (FEES), videofluoroscopy, and manometry. Those with prolonged or poorly compensated dysphagia are offered rehabilitation surgery. We describe this technique, which has proved beneficial to our patients. Guidelines for management are proposed.

Intradural jugular paragangliomas: complications and sequelae

OBJECTIVES

To present the long-term results of a group of patients who underwent surgery for intradural jugular paragangliomas. We discuss the complications, sequelae, and evolution of recurrences and behavior of residual tumors.

METHODS

From 1989 to 2002, 11 patients with intradural jugular paragangliomas underwent surgery using different approaches. The paragangliomas were grouped according to the classification of Fisch.

RESULTS

Total removal of the paraganglioma was possible in eight patients, while a subtotal resection was achieved in the other three cases. The tumor remnant remained stable in two patients but continued to grow in one. Recurrence was observed in one patient. There were preoperative deficits in cranial nerves IX to XI in four patients and of XII in two patients. Deficits of cranial nerves IX to XI were acquired as a result of surgery in three cases and of XII in another. Six patients had a pure-tone average of 45 to 75 dB while the others had dead ears. Persistent dysphagia and dysphonia were managed in two patients by injection of the paralyzed cord with fat and subsequent medialization of the vocal cord by thyroplasty. Two patients had a cerebrospinal fluid leak.

CONCLUSIONS

Surgical results in patients with extensive jugular paragangliomas are consistent and offer an acceptable quality of life even in advanced cases.

Radiosurgery of glomus jugulare tumors: a meta-analysis

PURPOSE

During the past two decades, radiosurgery has arisen as a promising approach to the management of glomus jugulare. In the present study, we report on a systematic review and meta-analysis of the available published data on the radiosurgical management of glomus jugulare tumors.

METHODS AND MATERIALS

To identify eligible studies, systematic searches of all glomus jugulare tumors treated with radiosurgery were conducted in major scientific publication databases. The data search yielded 19 studies, which were included in the meta-analysis. The data from 335 glomus jugulare patients were extracted. The fixed effects pooled proportions were calculated from the data when Cochrane's statistic was statistically insignificant and the inconsistency among studies was <25%. Bias was assessed using the Egger funnel plot test.

RESULTS

Across all studies, 97% of patients achieved tumor control, and 95% of patients achieved clinical control. Eight studies reported a mean or median follow-up time of >36 months. In these studies, 95% of patients achieved clinical control and 96% achieved tumor control. The gamma knife, linear accelerator, and CyberKnife technologies all exhibited high rates of tumor and clinical control.

CONCLUSIONS

The present study reports the results of a meta-analysis for the radiosurgical management of glomus jugulare. Because of its high effectiveness, we suggest considering radiosurgery for the primary management of glomus jugulare tumors.

Sellar paraganglioma: a unique route to a rare destination case report and literature review

OBJECTIVE

Paragangliomas of the sella are rare; 14 cases have been reported in the literature. We describe here the unique case of a sellar paraganglioma that extended into the orbit through the superior orbital fissure. We have also reviewed all reported cases of sellar paragangliomas to better define best management strategies.

CLINICAL PRESENTATION

A 63-year-old male presented with left eye proptosis and conjunctival vessel dilatation.

INTERVENTION

Resection of the intraorbital component of the tumor was accomplished using a transcranial-transorbital approach.

CONCLUSION

This is the first report of a sellar/parasellar paraganglioma extending into the orbit through the superior orbital fissure. While an appropriate treatment paradigm has not been established, a review of all previously reported cases suggests that radiotherapy is an important consideration.

Recurrent paraganglioma of Meckel's cave: Case report and a review of anatomic origin of paragangliomas

BACKGROUND

Paragangliomas are rare, usually benign tumors of neural crest origin. They account for only 0.6% of all head and neck tumors. In the craniocervical area, they are more common in the carotid body and tympanico-jugular regions. To the authors' knowledge, a case of paraganglioma in Meckel's cave has not yet been reported in the medical literature. The pathogenesis and natural history of paragangliomas are still not well understood. We present a case of recurrent paraganglioma in Meckel's cave.

CASE DESCRIPTION

A 53-year-old woman was diagnosed with trigeminal neuralgia, dysesthesia and hypoesthesia on the left side of the face, hearing disturbance and a history of chronic, persistent temporal headaches. Magnetic resonance imaging (MRI) showed a lesion located in Meckel's cave on the left side, extending to the posterior cranial fossa and compressing the left cerebral peduncle. The lesion was first thought to be a recurrence of an atypical meningioma, as the pathologist described it in the tissue specimen resected 3 years earlier, and a decision for re-operation was made. A lateral suboccipital approach to the lesion was used under neuronavigational guidance. The tumor was removed, and histological examination proved the lesion to be a paraganglioma. Five months later, the follow-up MRI showed local regrowth, which required subsequent surgical intervention.

CONCLUSIONS

A paraganglioma in Meckel's cave is an uncommon tumor in this location. Although ectopic paragangliomas have been described in the literature, a paraganglioma atypically located in Meckel's cave makes a topographic correlation difficult, mainly because paraganglionic cells are usually not found in Meckel's cave. Another peculiarity of the case is the local recurrence of the tumor in a relatively short time despite an attempted, almost gross total resection.

The Role of Radiotherapy in the Management of Paraganglioma

Paragangliomas or glomus tumors are usually low-grade hypervascular tumors occurring in various sites of the autonomic nervous system including the carotid body, glomus vagale and glomus tympanicum. Although the grading of the tumor suggests a benign clinical course, the tumor can be locally malignant and surgical management is sometimes difficult because of postoperative functional loss and local recurrence. In addition, the operative field is generally very bloody and tissue planes are not always well-defined.

Though the optimal management of paraganglioma occurs in a multidisciplinary setting, considering the excellent local control rates with primary irradiation alone, a nonsurgical definitive approach should initially be considered.

The safety and efficacy of gamma knife surgery in management of glomus jugulare tumor

Background

Glomus jugulare is a slowly growing, locally destructive tumor located in the skull base with difficult surgical access. The operative approach is, complicated by the fact that lesions may be both intra and extradural with engulfment of critical neurovascular structures. The tumor is frequently highly vascular, thus tumor resection entails a great deal of morbidity and not infrequent mortality. At timeslarge residual tumors are left behind. To decrease the morbidity associated with surgical resection of glomus jugulare, gamma knife surgery (GKS) was performed as an alternative in 13 patients to evaluate its safety and efficacy.

Methods

A retrospective review of 13 residual or unresectable glomus jagulare treated with GKS between 2004 and 2008.. Of these, 11 patients underwent GKS as the primary management and one case each was treated for postoperative residual disease and postembolization. The radiosurgical dose to the tumor margin ranged between 12-15 Gy.

Results

Post- gamma knife surgery and during the follow-up period twelve patients demonstrated neurological stability while clinical improvement was achieved in 5 patients. One case developed transient partial 7th nerve palsy that responded to medical treatment. In all patients radiographic MRI follow-up was obtained, the tumor size decreased in two cases and remained stable (local tumor control) in eleven patients.

Conclusions

Gamma knife surgery provids tumor control with a lowering of risk of developing a new cranial nerve injury in early follow-up period. This procedure can be safely used as a primary management tool in patients with glomus jugulare tumors, or in patients with recurrent tumors in this location. If long-term results with GKS are equally effective it will emerge as a good alternative to surgical resection.

Radiosurgery for glomus jugulare: history and recent progress

In this article the authors review the literature for recent studies of radiosurgical treatment for glomus jugulare. These studies demonstrate that radiosurgery results in similar glomus jugulare tumor control and a superior morbidity profile compared with surgical treatment. In addition, patients treated with radiosurgery usually remain stable clinically or improve. Given the indolent nature of these tumors, however, more follow-up is required to ensure that the immediate benefits are lasting. These preliminary reports demonstrate that the use of radiosurgery as a primary treatment for glomus jugulare should be extended to encompass more of the patients who are currently assigned to microsurgical treatment.

Paragangliomas of head and neck: a treatment option with CyberKnife radiosurgery

Paragangliomas are highly vascular and predominantly benign neoplasms that have traditionally been treated by surgery, embolization and/or external beam radiotherapy (EBRT). The aim of this study is to evaluate the short-term local tumor control and safety of CyberKnife radiosurgery for these lesions. Nine patients, eight with jugular glomus paragangliomas and one with a carotid body paraganglioma, were treated. The target contouring was performed on merged CT and MR images. Eight patients were treated with doses ranging from 11 to 13 Gy (mean 12.5 Gy) in a single fraction and one with 24 Gy in three fractions prescribed to 72-83% isodose line. The mean follow-up was 20 months. One patient died from unrelated causes. There were no local recurrences. All eight patients also demonstrated neurological stability or improvement. Neither cranial nerve palsies have arisen, nor has deterioration beyond baseline been observed. In conclusion, CyberKnife radiosurgery appears to be both safe and effective in the treatment of skull base paragangliomas. Determining whether long-term complications will arise will require further investigation.

Glomus jugulare tumours: certain clinical and radiological aspects observed following Gamma Knife radiosurgery

INTRODUCTION

Glomus jugulare tumours represent a great therapeutic challenge. Previous papers have documented good results from Gamma Knife surgery (GKS) with these tumours. However, the relationship between clinical improvement and tumour shrinkage has never been assessed.

MATERIALS AND METHODS

There were 14 patients, 9 women and 5 men. The mean follow-up period was 28 months (range 6 to 60 months). All the tumours except one were Fisch type D and the mean volume was 14.2 cm(3) (range 3.7-28.4 cm(3)). The mean prescription dose was 13.6 Gy (range 12-16 Gy).

RESULTS

None of the tumours have continued to grow. Eight are smaller and 6 unchanged in volume. Two patients with bruit have had no improvement in their symptoms. Among the other 12 patients, 5 have had symptomatic improvement of dysphagia, 4 in dysphonia, 3 in facial numbness, 3 in ataxia and 2 in tinnitus. Individual patients have experienced improvement in vomiting, vertigo, tongue fasciculation, hearing, headache, facial palsy and accessory paresis. One patient developed a transient facial palsy. Symptomatic improvement commonly began before any reduction in tumour volume could be detected. The mean time to clinical improvement was 6.5 months whereas the mean time to shrinkage was 13.5 months.

CONCLUSIONS

Gamma Knife treatment of glomus jugulare tumours is associated with a high incidence of clinical improvement with few complications, using the dosimetry recorded here. Clinical improvement would seem to be a more sensitive early indicator of therapeutic success than radiological volume reduction. Further follow-up will be needed.

Definitive radiotherapy in the management of paragangliomas arising in the head and neck: a 35-year experience

BACKGROUND

An evaluation of the treatment results for 104 patients with 121 paragangliomas of the temporal bone, carotid body, and/or glomus vagale who were treated with radiation therapy (RT) at the University of Florida between 1968 and 2004.

METHODS

Eighty-nine paragangliomas (86%) were treated with conventional megavoltage techniques, 15 (14%) patients with stereotactic fractionated radiation therapy, 6 (6%) patients with stereotactic radiosurgery (SRS), and 11 (11%) patients with intensity-modulated radiation therapy (IMRT).

RESULTS

There were 6 local recurrences. One recurrence was salvaged with additional RT. The actuarial local control and cause-specific survival rates at 10 years were 94% and 95%. The overall local control rate for all 121 lesions was 95%; the ultimate local control rate was 96%. The incidence of treatment-related complications was low.

CONCLUSION

Fractionated RT offers a high probability of tumor control with minimal risks for patients with paragangliomas of the temporal bone and neck.

A biomechanical study of artificial cervical discs using computer simulation

STUDY DESIGN

A virtual simulation model of the subaxial cervical spine was used to study the biomechanical effects of various disc prosthesis designs.

OBJECTIVE

To study the biomechanics of different design features of cervical disc arthroplasty devices.

SUMMARY OF BACKGROUND DATA

Disc arthroplasty is an alternative approach to cervical fusion surgery for restoring and maintaining motion at a diseased spinal segment. Different types of cervical disc arthroplasty devices exist and vary based on their placement and degrees of motion offered.

METHODS

A virtual dynamic model of the subaxial cervical spine was used to study 3 different prosthetic disc designs (PDD): (1) PDD-I: The center of rotation of a spherical joint located at the mid C5-C6 disc, (2) PDD-II: The center of rotation of a spherical joint located 6.5 mm below the mid C5-C6 disc, and (3) PDD-III: The center of rotation of a spherical joint in a plane located at the C5-C6 disc level.

RESULTS

A constrained spherical joint placed at the disc level (PDD-I) significantly increased facet loads during extension. Lowering the rotational axis of the spherical joint towards the subjacent body (PDD-II) caused a marginal increase in facet loading during flexion, extension, and lateral bending. Lastly, unconstraining the spherical joint to move freely in a plane (PDD-III) minimized facet load build up during all loading modes.

CONCLUSION

The simulation model showed the impact simple design changes may have on cervical disc dynamics. The predicted facet loads calculated from computer model have to be validated in the experimental study.

Biomechanical testing simulation of a cadaver spine specimen: development and evaluation study

STUDY DESIGN

This article describes a computer model of the cadaver cervical spine specimen and virtual biomechanical testing.

OBJECTIVES

To develop a graphics-oriented, multibody model of a cadaver cervical spine and to build a virtual laboratory simulator for the biomechanical testing using physics-based dynamic simulation techniques.

SUMMARY OF BACKGROUND DATA

Physics-based computer simulations apply the laws of physics to solid bodies with defined material properties. This technique can be used to create a virtual simulator for the biomechanical testing of a human cadaver spine. An accurate virtual model and simulation would complement tissue-based in vitro studies by providing a consistent test bed with minimal variability and by reducing cost.

METHOD

The geometry of cervical vertebrae was created from computed tomography images. Joints linking adjacent vertebrae were modeled as a triple-joint complex, comprised of intervertebral disc joints in the anterior region, 2 facet joints in the posterior region, and the surrounding ligament structure. A virtual laboratory simulation of an in vitro testing protocol was performed to evaluate the model responses during flexion, extension, and lateral bending.

RESULTS

For kinematic evaluation, the rotation of motion segment unit, coupling behaviors, and 3-dimensional helical axes of motion were analyzed. The simulation results were in correlation with the findings of in vitro tests and published data. For kinetic evaluation, the forces of the intervertebral discs and facet joints of each segment were determined and visually animated.

CONCLUSIONS

This methodology produced a realistic visualization of in vitro experiment, and allowed for the analyses of the kinematics and kinetics of the cadaver cervical spine. With graphical illustrations and animation features, this modeling technique has provided vivid and intuitive information.

Less Common Indications for Stereotactic Radiosurgery or Fractionated Radiotherapy for Patients with Benign Brain Tumors

Microsurgical resection remains the mainstay of treatment for truly benign brain tumors that can be safely resected because of the potential for permanent cure with most histologic findings, including most of the histologic findings discussed in this article. Physicians must keep in mind the indolent nature of many of the benign brain tumors and realize that many patients are likely to live out normal life spans if tumor control is achieved. Therefore, it is not sufficient simply to consider local tumor control rates and short-term toxicity risks when choosing between surgery, stereotactic radiosurgery, and fractionated radiotherapy. Patients need to be apprised of all therapeutic options and to make their decisions with all information required to evaluate the risks and benefits. For benign brain tumors, these decisions may have consequences that last for decades.