Hyun-Tai Chung

Hearing preservation after gamma knife stereotactic radiosurgery of vestibular schwannoma

To evaluate the hearing preservation rate and to determine its prognostic factors after gamma knife (GK) stereotactic radiosurgery (SRS) in patients with vestibular schwannoma, the authors used a prospective study design to analyze these patients.

Gamma knife radiosurgery for skull base meningiomas: long-term radiologic and clinical outcome.

PURPOSE To analyze the long-term outcomes in patients with skull base meningiomas (SBMNGs) treated with Gamma Knife radiosurgery (GKRS). METHODS AND MATERIALS Of the 98 consecutive patients with SBMNGs treated with GKRS between 1998 and 2002, 63 were followed up for more than 48 months. The mean (+/-SD) age of the patients was 50 +/- 12 years, the mean tumor volume was 6.5 cm(3) (range, 0.5-18.4 cm(3)), the mean marginal dose was 12.6 Gy (range, 7.0-20.0 Gy), and the mean follow-up duration was 77 +/- 18 months. The mean number of shots was 13.7 +/- 3.8. The tumor volume was decreased at the last follow-up in 28 patients (44.4%) and increased in 6 (9.6%). The actuarial tumor control rate was 90.2% at 5 years. No notable prognostic factor related to tumor control was identified. Ten patients (15.9%) with a cranial neuropathy showed unfavorable outcomes. The rate of improvement in patients with a cranial neuropathy was 45.1%. Age >70 years was likely correlated with an unfavorable outcome in patients with cranial neuropathy (odds ratio = 0.027; p = 0.025; 95% confidence interval 0.001-0.632). Cavernous sinus location was significantly associated with improvement of a cranial neuropathy (odds ratio = 7.314; p = 0.007; 95% confidence interval 1.707-31.34). CONCLUSIONS Gamma Knife radiosurgery is an effective modality for the treatment of SBMNGs and provides favorable outcomes in patients with cranial neuropathy, even in the long-term follow-up period. However, radiosurgery for patients with no or only mild symptoms should be performed cautiously because neither complication rate is low enough to be negligible, especially in elderly patients. A cranial neuropathy by MNGs involving the cavernous sinus seems to have a higher chance of improvement after radiosurgery than other SBMNGs.

Radiosurgical treatment of vestibular schwannomas in patients with neurofibromatosis type 2: tumor control and hearing preservation.

The radiosurgical treatment of vestibular schwannomas in patients with neurofibromatosis type 2 (NF2) is controversial. The authors investigated the radiologically proven tumor control rate after gamma knife radiosurgery. The factors that affect tumor control and serviceable hearing preservation were analyzed.

The number of CD8+ T cells and NKT cells increases in the aqueous humor of patients with Behçet's uveitis

To determine whether there are differences in the immunopathogenesis of different endogenous uveitis syndromes, the phenotypic characteristics of immune cells were analysed among patients with endogenous uveitis. The aetiology of the uveitis included idiopathic recurrent acute anterior uveitis (18 patients), idiopathic intermediate uveitis (13 patients), Behçets uveitis (17 patients), Vogt–Koyanagi–Harada syndrome (7 patients), and so on. Flow cytometric analysis was performed using immune cells of the aqueous humor and the peripheral blood during the active phase of intraocular inflammation, and monoclonal antibodies to CD3, CD4, CD8, CD14, CD19, CD56, TCR γδ, pan TCR αβ and Vα24. CD8+ T cells were predominant in the aqueous humor of the patients with Behçets uveitis, whereas CD4+ T cells were mainly found in the aqueous humor of patients other than those with Behçets uveitis. The number of NKT (CD3+CD56+) cells was significantly higher both in the aqueous humor and the peripheral blood of the patients with Behçets uveitis compared with the other groups (P < 0·05). CD8+CD56+ cells were the predominant subtype of the increased NKT cells in patients with Behçets uveitis. In addition, intraocular infiltration of CD14+ cells significantly differed among the uveitis patients (P < 0·05). These results suggest that the immunopathogenesis of endogenous uveitis can vary between syndromes, and that CD8+CD56+ NKT cells may play an important role in the immunopathogenesis of Behçets uveitis.

Gamma knife surgery of superficially located meningioma

OBJECT The authors analyzed tumor control rates and complications in patients with superficially located meningiomas after gamma knife surgery (GKS). METHODS Between 1998 and 2003, GKS was performed in 23 patients with 26 lesions in whom follow-up imaging for 1 year or more was available. The male/female ratio was 1:22. The mean age was 59 years. The median tumor volume was 4.7 cm3, and the mean margin dose was 16 Gy at the 50% isodose line. Peritumoral edema was revealed on magnetic resonance (MR) imaging in four patients before GKS. Magnetic resonance imaging and clinical examinations were performed every 6 months after GKS. The mean follow-up duration was 32 months. The tumor shrank in eight cases, was stable in 17, and enlarged in one; thus 25 (95%) of 26 tumors were controlled. A peritumoral high signal on T2-weighted MR images was found in eight lesions and preexisting edema was aggravated in three lesions after GKS. Ten of these 11 patients complained of severe headache, and three patients experienced neurological deficits at the same time after a mean latency of 3 months; however, high signal was not demonstrated on imaging before 6 months on average. Steroid agents, when required, gave relief to all patients. The complication rate was 43% (10 of 23 cases). High signal disappeared in nine patients and decreased in the remaining two. High signal was associated with a high integral dose and a large tumor volume. Tumor shrinkage at the last follow-up examination was more prominent in the patients with symptomatic high signal (p = 0.03). CONCLUSIONS There was a good tumor control rate with a high complication rate. Longer follow up of more patients is needed. Adjusting the dose-volume relationship should be considered to reduce complications.

Gamma knife radiosurgery for brain metastases: prognostic factors for survival and local control

The purpose of this paper was to note a potential source of error in magnetic resonance (MR) imaging. Magnetic resonance images were acquired for stereotactic planning for GKS of a vestibular schwannoma in a female patient. The images were acquired using three-dimensional sequence, which has been shown to produce minimal distortion effects. The images were transferred to the planning workstation, but the coronal images were rejected. By examination of the raw data and reconstruction of sagittal images through the localizer side plate, it was clearly seen that the image of the square localizer system was grossly distorted. The patient was returned to the MR imager for further studies and a metal clasp on her brassiere was identified as the cause of the distortion.A-60-year-old man with medically intractable left-sided maxillary division trigeminal neuralgia had severe cardiac disease, was dependent on an internal defibrillator and could not undergo magnetic resonance imaging. The patient was successfully treated using computerized tomography (CT) cisternography and gamma knife radiosurgery. The patient was pain free 2 months after GKS. Contrast cisternography with CT scanning is an excellent alternative imaging modality for the treatment of patients with intractable trigeminal neuralgia who are unable to undergo MR imaging.The authors describe acute deterioration in facial and acoustic neuropathies following radiosurgery for acoustic neuromas. In May 1995, a 26-year-old man, who had no evidence of neurofibromatosis Type 2, was treated with gamma knife radiosurgery (GKS; maximum dose 20 Gy and margin dose 14 Gy) for a right-sided intracanalicular acoustic tumor. Two days after the treatment, he developed headache, vomiting, right-sided facial weakness, tinnitus, and right hearing loss. There was a deterioration of facial nerve function and hearing function from pretreatment values. The facial function worsened from House-Brackmann Grade 1 to 3. Hearing deteriorated from Grade 1 to 5. Magnetic resonance (MR) images, obtained at the same time revealed an obvious decrease in contrast enhancement of the tumor without any change in tumor size or peritumoral edema. Facial nerve function improved gradually and increased to House-Brackmann Grade 2 by 8 months post-GKS. The tumor has been unchanged in size for 5 years, and facial nerve function has also been maintained at Grade 2 with unchanged deafness. This is the first detailed report of immediate facial neuropathy after GKS for acoustic neuroma and MR imaging revealing early possibly toxic changes. Potential explanations for this phenomenon are presented.In clinical follow-up studies after radiosurgery, imaging modalities such as computerized tomography (CT) and magnetic resonance (MR) imaging are used. Accurate determination of the residual lesion volume is necessary for realistic assessment of the effects of treatment. Usually, the diameters rather than the volume of the lesion are measured. To determine the lesion volume without using stereotactically defined images, the software program VOLUMESERIES has been developed. VOLUMESERIES is a personal computer-based image analysis tool. Acquired DICOM CT scans and MR image series can be visualized. The region of interest is contoured with the help of the mouse, and then the system calculates the volume of the contoured region and the total volume is given in cubic centimeters. The defined volume is also displayed in reconstructed sagittal and coronal slices. In addition, distance measurements can be performed to measure tumor extent. The accuracy of VOLUMESERIES was checked against stereotactically defined images in the Leksell GammaPlan treatment planning program. A discrepancy in target volumes of approximately 8% was observed between the two methods. This discrepancy is of lesser interest because the method is used to determine the course of the target volume over time, rather than the absolute volume. Moreover, it could be shown that the method was more sensitive than the tumor diameter measurements currently in use. VOLUMESERIES appears to be a valuable tool for assessing residual lesion volume on follow-up images after gamma knife radiosurgery while avoiding the need for stereotactic definition.This study was conducted to evaluate the geometric distortion of angiographic images created from a commonly used digital x-ray imaging system and the performance of a commercially available distortion-correction computer program. A 12 x 12 x 12-cm wood phantom was constructed. Lead shots, 2 mm in diameter, were attached to the surfaces of the phantom. The phantom was then placed inside the angiographic localizer. Cut films (frontal and lateral analog films) of the phantom were obtained. The films were analyzed using GammaPlan target series 4.12. The same procedure was repeated with a digital x-ray imaging system equipped with a computer program to correct the geometric distortion. The distortion of the two sets of digital images was evaluated using the coordinates of the lead shots from the cut films as references. The coordinates of all lead shots obtained from digital images and corrected by the computer program coincided within 0.5 mm of those obtained from cut films. The average difference is 0.28 mm with a standard deviation of 0.01 mm. On the other hand, the coordinates obtained from digital images with and without correction can differ by as much as 3.4 mm. The average difference is 1.53 mm, with a standard deviation of 0.67 mm. The investigated computer program can reduce the geometric distortion of digital images from a commonly used x-ray imaging system to less than 0.5 mm. Therefore, they are suitable for the localization of arteriovenous malformations and other vascular targets in gamma knife radiosurgery.

Gamma knife radiosurgery for central neurocytoma: primary and secondary treatment.

Little is known about long‐term results of gamma knife (GK) stereotactic radiosurgery (SRS) as a primary or a secondary postoperative therapy for central neurocytomas (CNs). The authors retrospectively reviewed long‐term outcomes of 13 patients with CN treated with GK SRS.

Long-Term Outcome of Gamma Knife Radiosurgery for Treatment of Typical Trigeminal Neuralgia

PURPOSE To analyze the long-term outcomes of patients with typical trigeminal neuralgia treated with gamma knife radiosurgery (GKRS). PATIENTS AND METHODS A total of 62 consecutive patients with typical trigeminal neuralgia were treated with GKRS between 1998 and 2004. Of the 62 patients, 2 were lost to follow-up; the remaining 60 patients were followed for >12 months. The mean prescribed maximal dose was 79.7 Gy (range, 75-80), using a 4-mm shot. RESULTS Of the 60 patients, 48 were followed for >4 years. An additional 3 patients, followed for <4 years, experienced recurrent pain after a favorable initial response and were incorporated into the long-term response analysis. Of these 51 patients (mean age, 61 +/- 11 years; 37 women [72.5%]; and mean follow-up duration, 58 +/- 14 months), 46 (90.2%) responded to GKRS, as demonstrated by an improvement in their Barrow Neurological Institute pain intensity score. Of the 46 patients, 24 (52.2%) had pain recurrence. The actuarial recurrence-free survival rate was 84.8%, 76.1%, 69.6%, 63.0%, and 45.8% at 1, 2, 3, 4, and 5 years after radiosurgery, respectively. Patient age >70 years correlated with a favorable outcome in terms of pain recurrence after radiosurgery (hazard ratio, 0.125; 95% confidence interval, 0.016-0.975; p = .047) on multivariate analysis. CONCLUSION GKRS seems to be an effective treatment modality for patients with typical trigeminal neuralgia considering the initial response rate; however, fewer than one-half of patients might continue to benefit from GKRS after long-term follow-up. Elderly patients might be good candidates for radiosurgery considering the long-term durability of efficacy.

Radiosurgery for unruptured cerebral arteriovenous malformations Long-term seizure outcome

Objective: To date, seizures in relation to arteriovenous malformations (AVM) have been a secondary target of most studies. The insufficient evaluation, in conjunction with the lack of consistent seizure outcome assessment, has made it been difficult to draw conclusions about seizure outcome after radiosurgery for AVM. This study aimed to determine the effect of radiosurgery on seizure outcome depending on AVM obliteration and on the development of new seizure in patients with AVM. Methods: Between 1997 and 2006, 161 consecutive patients underwent radiosurgery for unruptured AVM and were retrospectively assessed with a mean follow-up of 89.8 months by their medical records, updated clinical information, and, when necessary, direct patient contact. Seizure outcome was assessed using the Engel seizure frequency scoring system. Results: Of the 86 patients with a history of seizure before radiosurgery, 76.7% (66/86) were seizure-free and 58.1% (50/86) were medication-free at the last follow-up visit. Of the patients who achieved AVM obliteration, 96.7% (58/60) were seizure-free while 30.8% (8/26) of those patients who did not achieve AVM obliteration were seizure-free (p = 0.001). The proportion of patients who were medication-free was 81.7% (49/60) of the patients with obliteration and 3.8% (1/26) of patients without obliteration (p < 0.001). Of the 75 patients with no history of seizure before radiosurgery, 10 had provoked seizures due to the direct and indirect radiosurgical influences after radiosurgery. Conclusions: Although radiosurgery tends to cause seizures temporarily, the radiosurgery may improve seizure outcomes in patients with AVM-related seizures, especially in patients with AVM obliteration.

Evaluation of tumour response after gamma knife radiosurgery for residual vestibular schwannomas based on MRI morphological features

Objective: To evaluate tumour response after gamma knife (GK) radiosurgery for residual vestibular schwannoma (VS) based on MRI morphological features. Methods: Sixty-one patients with histopathologically confirmed VS underwent GK radiosurgery with marginal tumour doses of 9.0–14.0 Gy (mean, 12.5). Mean tumour volume at GK radiosurgery was 3.65 ml (range, 0.52–15.50). GK radiosurgery was performed 0.3–95.7 months (median, 5.8) after microsurgery. Tumour volumes and half-reduction time were calculated using serial MRI. The morphological features of VS were documented by pre-microsurgical MRI. Histopathological investigation included Antoni-type dominance, the proliferation marker Ki-67 and tumour vascularity. Results: Median duration of radiological follow-up was 53.7 months (range, 24.1–102.2) and the 8-year actuarial tumour control rate was 93.5%. No factor was associated with tumour control, although a cystic VS had borderline significance (p = 0.089). Mean tumour half-reduction time was 8.70 years (range, 0.57–79.89) and tumour half-reduction time in cystic VS proved to be significantly shorter than those in solid VS (p = 0.006). Thrombotic vessels (p = 0.015) and abnormal vessel proliferation (p = 0.003) were significantly more prominent in cystic VS than those in solid VS. Conclusions: GK radiosurgery appeared to be an effective treatment modality for residual tumour control after microsurgery. Owing to having relatively abundant tumour vascularity, residual solid portions of cystic VS resulted in efficient shrinkage after GK radiosurgery. Therefore, GK radiosurgery was found to be a rewarding therapeutic approach to the residual solid portions of cystic VS.