Functional and Structural Connectivity Patterns Associated with Clinical Outcomes in Deep Brain Stimulation of the Globus Pallidus Internus for Generalized Dystonia

BACKGROUND AND PURPOSE

Deep brain stimulation is a well-established treatment for generalized dystonia, but outcomes remain variable. Establishment of an imaging marker to guide device targeting and programming could possibly impact the efficacy of deep brain stimulation in dystonia, particularly in the absence of acute clinical markers to indicate benefit. We hypothesize that the stimulation-based functional and structural connectivity using resting-state fMRI and DTI can predict therapeutic outcomes in patients with generalized dystonia and deep brain stimulation.

MATERIALS AND METHODS

We performed a retrospective analysis of 39 patients with inherited or idiopathic-isolated generalized dystonia who underwent bilateral globus pallidus internus deep brain stimulation. After electrode localization, the volumes of tissue activated were modeled and used as seed regions for functional and structural connectivity measures using a normative data base. Resulting connectivity maps were correlated with postoperative improvement in the Unified Dystonia Rating Scale score.

RESULTS

Structural connectivity between the volumes of tissue activated and the primary sensorimotor cortex was correlated with Unified Dystonia Rating Scale improvement, while more anterior prefrontal connectivity was inversely correlated with Unified Dystonia Rating Scale improvement. Functional connectivity between the volumes of tissue activated and primary sensorimotor regions, motor thalamus, and cerebellum was most correlated with Unified Dystonia Rating Scale improvement; however, an inverse correlation with Unified Dystonia Rating Scale improvement was seen in the supplemental motor area and premotor cortex.

CONCLUSIONS

Functional and structural connectivity with multiple nodes of the motor network is associated with motor improvement in patients with generalized dystonia undergoing deep brain stimulation. Results from this study may serve as a basis for future development of clinical markers to guide deep brain stimulation targeting and programming in dystonia.

Segmentation of the Globus Pallidus Internus Using Probabilistic Diffusion Tractography for Deep Brain Stimulation Targeting in Parkinson Disease

BACKGROUND AND PURPOSE

Although globus pallidus internus deep brain stimulation is a widely accepted treatment for Parkinson disease, there is persistent variability in outcomes that is not yet fully understood. In this pilot study, we aimed to investigate the potential role of globus pallidus internus segmentation using probabilistic tractography as a supplement to traditional targeting methods.

MATERIALS AND METHODS

Eleven patients undergoing globus pallidus internus deep brain stimulation were included in this retrospective analysis. Using multidirection diffusion-weighted MR imaging, we performed probabilistic tractography at all individual globus pallidus internus voxels. Each globus pallidus internus voxel was then assigned to the 1 ROI with the greatest number of propagated paths. On the basis of deep brain stimulation programming settings, the volume of tissue activated was generated for each patient using a finite element method solution. For each patient, the volume of tissue activated within each of the 10 segmented globus pallidus internus regions was calculated and examined for association with a change in the Unified Parkinson Disease Rating Scale, Part III score before and after treatment.

RESULTS

Increasing volume of tissue activated was most strongly correlated with a change in the Unified Parkinson Disease Rating Scale, Part III score for the primary motor region (Spearman r = 0.74, P = .010), followed by the supplementary motor area/premotor cortex (Spearman r = 0.47, P = .15).

CONCLUSIONS

In this pilot study, we assessed a novel method of segmentation of the globus pallidus internus based on probabilistic tractography as a supplement to traditional targeting methods. Our results suggest that our method may be an independent predictor of deep brain stimulation outcome, and evaluation of a larger cohort or prospective study is warranted to validate these findings.

Advances in the nutrition of preterm infants

The greatly improved survival rate of infants born both preterm and low birth weight (LBW) has led to the subsequent growth and development of these infants becoming an important focus for research. Preterm infants begin life with, or acquire as a result of their prematurity, greater morbidity than term born babies, growth deficits, an increased risk of developmental delay and an increased risk of later adult diseases compared with appropriate for gestational age (AGA) term born babies.

Research in recent decades has confirmed that there are marked differences in the nutritional requirements of preterm LBW infants compared with their AGA term born counterparts, both in the neonatal period and probably for all of infancy. In addition to the increased requirement for energy and protein, preterm LBW infants demonstrate a greatly increased requirement for some of the mineral elements, particularly iron, zinc and calcium, when compared with the needs of term AGA infants. In the UK, feeding practices for preterm infants in neonatal units and throughout infancy after hospital discharge are variable and many questions remain as to the optimal nutritional regimen for preterm LBW infants (and for subgroups of these infants) at different stages of infancy. There is some concern that the 2002 World Health Organization recommendations on infant feeding may be applied to all infants, including preterm infants, without consideration of their special nutritional needs, which may further compromise their growth and development.

A brief résumé of the work of prominent researchers in the field of preterm infant nutrition in the UK, notably Lucas, Cooke and Fewtrell, is included in the review, together with information from papers published by the authors of the review. The review concludes with a summary of the generally accepted recommendations on feeding preterm LBW infants after hospital discharge and information on some practical help available to the parents of these children and to health workers in the field.

The trajectory of apathy after deep brain stimulation: from pre-surgery to 6 months post-surgery in Parkinson's disease

Deep brain stimulation (DBS) has been associated with increased apathy in patients with PD, yet studies lack longitudinal data and have not assessed differences between sites of implantation (i.e. STN versus GPi). We assessed apathy prior to surgery and 6 months post-surgery using a longitudinal design-latent growth curve modeling. We hypothesized that apathy would increase post-surgery, and be related to subthalamic nucleus (versus globus pallidus interna) implantation. Forty-eight PD patients underwent unilateral surgery to either GPi or STN and completed the Apathy Scale prior to surgery and 2, 4, and 6 months post-surgery. Forty-eight matched PD controls completed the Apathy Scale at a 6-month interval. Results indicated apathy increased linearly from pre- to 6-months post-DBS by .66 points bi-monthly, while apathy in the control group did not change. There was no relationship between apathy and DBS site. Higher baseline depression was associated with higher baseline apathy, but not with change in apathy. Middle-aged adults (<65) had a steeper trajectory of apathy than older adults (≥ 65). Apathy trajectory was not related to motor severity, laterality of DBS, levodopa medication reduction, or motor changes after surgery.

Patient-specific analysis of the relationship between the volume of tissue activated during DBS and verbal fluency

Deep brain stimulation (DBS) for the treatment of advanced Parkinson's disease involves implantation of a lead with four small contacts usually within the subthalamic nucleus (STN) or globus pallidus internus (GPi). While generally safe from a cognitive standpoint, STN DBS has been commonly associated with a decrease in the speeded production of words, a skill referred to as verbal fluency. Virtually all studies comparing presurgical to postsurgical verbal fluency performance have detected a decrease with DBS. The decline may be attributable in part to the surgical procedures, yet the relative contributions of stimulation effects are not known. In the present study, we used patient-specific DBS computer models to investigate the effects of stimulation on verbal fluency performance. Specifically, we investigated relationships of the volume and locus of activated STN tissue to verbal fluency outcome. Stimulation of different electrode contacts within the STN did not affect total verbal fluency scores. However, models of activation revealed subtle relationships between the locus and volume of activated tissue and verbal fluency performance. At ventral contacts, more tissue activation inside the STN was associated with decreased letter fluency performance. At optimal contacts, more tissue activation within the STN was associated with improved letter fluency performance. These findings suggest subtle effects of stimulation on verbal fluency performance, consistent with the functional nonmotor subregions/somatotopy of the STN.

Mood and motor effects of thalamic deep brain stimulation surgery for essential tremor

PURPOSE

The aim of this study was to evaluate the effects of unilateral and bilateral ventralis intermedius (Vim) deep brain stimulation (DBS) on mood and motor function.

METHODS

Thirty-one consecutive medication refractory patients with essential tremor who underwent unilateral or bilateral Vim DBS at University of Florida and returned for at least 6 -month follow-up completed the Visual Analog Mood (VAMS), the Beck Depression Inventory (BDI), and the Tremor Rating Scale (TRS) before and after surgery. We excluded all patients who were implanted at other institutions.

RESULTS

The tense subscale of the VAMS improved significantly in both the unilateral and bilateral DBS groups (P < 0.001). On the VAMS afraid subscale, only the bilateral group trended toward improvement (P = 0.075). There were no significant changes for either group for the happy, confused, sad, angry, energetic or tired VAMS scores. TRS subscale scores all improved after unilateral and bilateral Vim DBS surgery (P < 0.001).

CONCLUSIONS

Feelings of tenseness, tremor severity and ADLs improved following unilateral or bilateral Vim DBS for ET.

Brain penetration effects of microelectrodes and DBS leads in STN or GPi

OBJECTIVE

To determine how intraoperative microelectrode recordings (MER) and intraoperative lead placement acutely influence tremor, rigidity, and bradykinesia. Secondarily, to evaluate whether the longevity of the MER and lead placement effects were influenced by target location (subthalamic nucleus (STN) or globus pallidus interna (GPi)).

BACKGROUND

Currently most groups who perform deep brain stimulation (DBS) for Parkinson disease (PD) use MER, as well as macrostimulation (test stimulation), to refine DBS lead position. Following MER and/or test stimulation, however, there may be a resultant "collision/implantation" or "microlesion" effect, thought to result from disruption of cells and/or fibres within the penetrated region. These effects have not been carefully quantified.

METHODS

47 consecutive patients with PD undergoing unilateral DBS for PD (STN or GPi DBS) were evaluated. Motor function was measured at six time points with a modified motor Unified Parkinson Disease Rating Scale (UPDRS): (1) preoperatively, (2) immediately after MER, (3) immediately after lead implantation/collision, (4) 4 months following surgery-off medications, on DBS (12 h medication washout), (5) 6 months postoperatively-off medication and off DBS (12 h washout) and (6) 6 months-on medication and off DBS (12 h washout).

RESULTS

Significant improvements in motor scores (p<0.05) (tremor, rigidity, bradykinesia) were observed as a result of MER and lead placement. The improvements were similar in magnitude to what was observed at 4 and 6 months post-DBS following programming and medication optimisation. When washed out (medications and DBS) for 12 h, UPDRS motor scores were still improved compared with preoperative testing. There was a larger improvement in STN compared with GPi following MER (p<0.05) and a trend for significance following lead placement (p<0.08) but long term outcome was similar.

CONCLUSION

This study demonstrated significant acute intraoperative penetration effects resulting from MER and lead placement/collision in PD. Clinicians rating patients in the operating suite should be aware of these effects, and should consider pre- and post-lead placement rating scales prior to activating DBS. The collision/implantation effects were greater intraoperatively with STN compared with GPi, and with greater disease duration there was a larger effect.

LRRK2 mutations in a clinic-based cohort of Parkinson's disease

In the last decade, major breakthroughs in the understanding of genetic contributions to Parkinson's disease (PD) have been achieved. Recently, mutations in LRRK2, encoding dardarin, have been found to be responsible for an autosomal dominant parkinsonism (OMIM 607060). We screened 311 subjects (cases: n = 202, controls: n = 109) for the three previously reported LRRK2 mutations. Our investigation revealed a sporadic case of PD with a heterozygous mutation G2019S (c.6055G>A). Here, we present the clinical phenotype of this patient and discuss the implications of genetic testing for the G2019S mutation in patients with sporadic PD.

Panic and fear induced by deep brain stimulation

BACKGROUND

Mood, cognitive, and behavioural changes have been reported with deep brain stimulation (DBS) in the thalamus, globus pallidus interna, and anterior limb of the internal capsule/nucleus accumbens region.

OBJECTIVE

To investigate panic and fear resulting from DBS.

METHODS

Intraoperative DBS in the region of the right and then left anterior limb of the internal capsule and nucleus accumbens region was undertaken to treat a 52 year old man with treatment refractory obsessive-compulsive disorder (OCD). Mood, anxiety, OCD, alertness, heart rate, and subjective feelings were recorded during intraoperative test stimulation and at follow up programming sessions.

RESULTS

DBS at the distal (0) contact (cathode 0-, anode 2+, pulse width 210 ms, rate 135 Hz, at 6 volts) elicited a panic attack (only seen at the (0) contact). The patient felt flushed, hot, fearful, and described himself as having a "panic attack." His heart rate increased from 53 to 111. The effect (present with either device) was witnessed immediately after turning the device on, and abruptly ceased in the off condition

CONCLUSIONS

DBS of the anterior limb of the internal capsule and nucleus accumbens region caused severe "panic." This response may result from activation of limbic and autonomic networks.

Mood and cognitive changes with deep brain stimulation. What we know and where we should go

AIM

The aim of this study was to completely review the literature on cognitive and mood changes resulting from deep brain stimulation (DBS), and to examine the factors that might lead to these changes. DBS has been shown to improve motor symptoms in many movement disorders. Despite the widespread use of this technique, there are relatively few well controlled studies describing the potential cognitive, mood and behavioral consequences that may result from DBS. Additionally, the factors that may influence these changes have not been carefully studied.

METHODS

A complete survey of the articles exploring the effects of DBS on mood and cognition was performed. Each study identified was examined and categories of factors that may have influenced mood and cognition were noted. These factors included surgical target, number of patients studied, whether procedures were unilateral or bilateral, average age of patients, diagnosis, condition of the DBS during the study (on or off), pre-operative screening tests (e.g., dementia rating scale, mini mental state exam), and changes on mood and cognitive tests (categorized as no change, improved, or worsened). Studies were divided into evidence-based categories.

RESULTS

There are many mood and cognitive changes that may result from DBS. Due to methodological limitations of existing studies there are important unanswered questions about cognitive and mood changes resulting from this type of surgery. The predominant amount of data regarding changes in mood and cognition with DBS is level 3 or case based evidence.

CONCLUSIONS

There exists a paucity of well-controlled studies addressing the mood and cognitive changes that result from DBS. Carefully performed prospective studies may help us to understand the effects of DBS on mood and cognition.

Efficacy and acceptability of a new topical skin lotion of sodium cromoglicate (Altoderm) in atopic dermatitis in children aged 2-12 years: a double-blind, randomized, placebo-controlled trial

BACKGROUND

Atopic dermatitis (AD) is a common inflammatory allergic disease of children. The primary anti-inflammatory therapy is topical steroids. An effective treatment without the topical and systemic adverse effects of corticosteroids would be useful. Topical formulations of sodium cromoglicate have been researched in the past, but without consistent results. We report a trial of a new aqueous skin lotion of sodium cromoglicate (Altoderm) in children with AD.

OBJECTIVES

To compare the efficacy, safety and acceptability of Altoderm lotion with a placebo control in the treatment of AD in children.

METHODS

A double-blind, controlled study in which children aged 2-12 years with AD were randomized to 12 weeks of treatment with a lotion containing 4% sodium cromoglicate (Altoderm) or the lotion base. To be included subjects had to have a SCORAD score of > or = 25 and < or = 60 at both of two clinic visits 14 days apart. Subjects continued using existing treatment which included emollients and topical steroids. The primary outcome was the change in the SCORAD score. The two groups were compared for the change in the SCORAD score from the second baseline visit to the visit after 12 weeks of treatment using an analysis of variance. Secondary outcome measures included parents' assessment of symptoms, usage of topical steroids recorded on daily diary cards, and final opinions of treatment by parent and clinician. Parents were asked about adverse effects at each clinic visit and the responses recorded.

RESULTS

Fifty-eight children were randomized to Altoderm and 56 to placebo and all were included in the intention-to-treat analysis. The mean +/- SD SCORAD scores at baseline were 41.0 +/- 9.0 (Altoderm) and 40.4 +/- 8.73 (placebo). These scores were reduced after 12 weeks by 13.2 (36%) with Altoderm and by 7.6 (20%) with placebo. The difference of 5.6 (95% confidence interval 1.0-10.3) is statistically significant (P = 0.018). Diary card symptoms improved with both treatments but the improvement was greater in the Altoderm-treated patients. Topical steroid usage was reduced in both groups and was larger in the Altoderm-treated patients. The differences were statistically significant for the mean of all symptoms, the overall skin condition and use of topical steroids. Those for itching and sleep loss were not. Treatment-related adverse events were reported in 11 subjects (Altoderm seven, placebo four). Most of these referred to irritation, redness and burning at the site of application. There were four reports of erythema and pruritus (Altoderm three, placebo one), and three reports of application site burning (Altoderm two, placebo one). None was reported as severe or very severe.

CONCLUSIONS

These results show a clinically useful benefit of this sodium cromoglicate lotion in children with moderately severe AD.

Development and initial validation of a screening tool for Parkinson disease surgical candidates

As there is currently no standardized assessment tool for evaluating Parkinson disease (PD) patients for deep brain stimulation (DBS), the authors developed the Florida Surgical Questionnaire for Parkinson Disease (FLASQ-PD). Part I of the study was a retrospective analysis of 174 patients presenting for a surgical screening. Part II was a multicenter study to assess the correlation of FLASQ-PD scores. The results of this study suggest that the FLASQ-PD may be a useful triage tool for screening PD patients for DBS surgery.

Mood changes with deep brain stimulation of STN and GPi: results of a pilot study

The results of this study suggest that there are mood changes associated with deep brain stimulation of the subthalamic nucleus (STN) and the globus pallidus interna (GPi). Further, optimal placement of electrodes in both STN and GPi seems to result in overall improvement in mood and is associated with a lower incidence of adverse mood effects than stimulation outside the optimal site. Preliminary data from this study, however, suggest that slight movement dorsal or ventral to the site of optimal motor performance may be associated with more adverse changes in mood with STN stimulation than with GPi stimulation.

Weaning preterm infants: a randomised controlled trial

OBJECTIVE

To assess the effect on growth and iron status in preterm infants of a specially devised weaning strategy compared with current best practices in infant feeding. The preterm weaning strategy recommended the early onset of weaning and the use of foods with a higher energy and protein content than standard milk formula, and foods that are rich sources of iron and zinc.

SUBJECTS AND DESIGN

In a blinded, controlled study, 68 preterm infants (mean (SD) birth weight 1470 (430) g and mean (SD) gestational age 31.3 (2.9) weeks) were randomised to either the preterm weaning strategy group (n = 37) or a current best practice control group (n = 31), from hospital discharge until 1 year gestation corrected age (GCA).

MAIN OUTCOME MEASURES

Weight, supine length, occipitofrontal head circumference, and intakes of energy, protein, and minerals were determined at 0, 6, and 12 months GCA. Levels of haemoglobin, serum iron, and serum ferritin were assayed at 0 and 6 months GCA.

RESULTS

Significant positive effects of treatment included: greater increase in standard deviation length scores and length growth velocity; increased intake of energy, protein, and carbohydrate at 6 months GCA and iron at 12 months GCA; increased haemoglobin and serum iron levels at 6 months GCA.

CONCLUSIONS

The preterm weaning strategy significantly influenced dietary intakes with consequent beneficial effects on growth in length and iron status. This strategy should be adopted as the basis of feeding guidelines for preterm infants after hospital discharge.

Weaning of infants

The WHO 2001 global recommendation is a one size fits all approach to weaning, an approach which may not take sufficient account of the special needs of some infants and fails to allow for the different problems encountered in the industrialised nations compared with economically developing countries. For the healthy normal birth weight full term infant born in an industrialised country, current research supports the benefit of exclusive breast milk feeding until 4-6 months. Evidence of harm through introducing solid food to these infants earlier than this is weak. Infants should be managed individually according to their needs.

Analysis of risk factors associated with radiosurgery for vestibular schwannoma

OBJECT

The aim of this study was to identify factors associated with delayed cranial neuropathy following radiosurgery for vestibular schwannoma (VS or acoustic neuroma) and to determine how such factors may be manipulated to minimize the incidence of radiosurgical complications while maintaining high rates of tumor control.

METHODS

From July 1988 to June 1998, 149 cases of VS were treated using linear accelerator radiosurgery at the University of Florida. In each of these cases, the patient's tumor and brainstem were contoured in 1-mm slices on the original radiosurgical targeting images. Resulting tumor and brainstem volumes were coupled with the original radiosurgery plans to generate dose-volume histograms. Various tumor dimensions were also measured to estimate the length of cranial nerve that would be irradiated. Patient follow-up data, including evidence of cranial neuropathy and radiographic tumor control, were obtained from a prospectively maintained, computerized database. The authors performed statistical analyses to compare the incidence of posttreatment cranial neuropathies or tumor growth between patient strata defined by risk factors of interest. One hundred thirty-nine of the 149 patients were included in the analysis of complications. The median duration of clinical follow up for this group was 36 months (range 18-94 months). The tumor control analysis included 133 patients. The median duration of radiological follow up in this group was 34 months (range 6-94 months). The overall 2-year actuarial incidences of facial and trigeminal neuropathies were 11.8% and 9.5%, respectively. In 41 patients treated before 1994, the incidences of facial and trigeminal neuropathies were both 29%, but in the 108 patients treated since January 1994, these rates declined to 5% and 2%, respectively. An evaluation of multiple risk factor models showed that maximum radiation dose to the brainstem, treatment era (pre-1994 compared with 1994 or later), and prior surgical resection were all simultaneously informative predictors of cranial neuropathy risk. The radiation dose prescribed to the tumor margin could be substituted for the maximum dose to the brainstem with a small loss in predictive strength. The pons-petrous tumor diameter was an additional statistically significant simultaneous predictor of trigeminal neuropathy risk, whereas the distance from the brainstem to the end of the tumor in the petrous bone was an additional marginally significant simultaneous predictor of facial neuropathy risk. The overall radiological tumor control rate was 93% (59% tumors regressed, 34% remained stable, and 7.5% enlarged), and the 5-year actuarial tumor control rate was 87% (95% confidence interval [CI] 76-98%). Analysis revealed that a radiation dose cutpoint of 10 Gy compared with more than 10 Gy prescribed to the tumor margin yielded the greatest relative difference in tumor growth risk (relative risk 2.4, 95% CI 0.6-9.3), although this difference was not statistically significant (p = 0.207).

CONCLUSIONS

Five points must be noted. 1) Radiosurgery is a safe, effective treatment for small VSs. 2) Reduction in the radiation dose has played the most important role in reducing the complications associated with VS radiosurgery. 3) The dose to the brainstem is a more informative predictor of postradiosurgical cranial neuropathy than the length of the nerve that is irradiated. 4) Prior resection increases the risk of late cranial neuropathies after radiosurgery. 5) A prescription dose of 12.5 Gy to the tumor margin resulted in the best combination of maximum tumor control and minimum complications in this series.

A geometrically based method for automated radiosurgery planning

PURPOSE

A geometrically based method of multiple isocenter linear accelerator radiosurgery treatment planning optimization was developed, based on a target's solid shape.

METHODS AND MATERIALS

Our method uses an edge detection process to determine the optimal sphere packing arrangement with which to cover the planning target. The sphere packing arrangement is converted into a radiosurgery treatment plan by substituting the isocenter locations and collimator sizes for the spheres.

RESULTS

This method is demonstrated on a set of 5 irregularly shaped phantom targets, as well as a set of 10 clinical example cases ranging from simple to very complex in planning difficulty. Using a prototype implementation of the method and standard dosimetric radiosurgery treatment planning tools, feasible treatment plans were developed for each target. The treatment plans generated for the phantom targets showed excellent dose conformity and acceptable dose homogeneity within the target volume. The algorithm was able to generate a radiosurgery plan conforming to the Radiation Therapy Oncology Group (RTOG) guidelines on radiosurgery for every clinical and phantom target examined.

CONCLUSIONS

This automated planning method can serve as a valuable tool to assist treatment planners in rapidly and consistently designing conformal multiple isocenter radiosurgery treatment plans.

Calculation of cranial nerve complication probability for acoustic neuroma radiosurgery

PURPOSE

Estimations of complications from stereotactic radiosurgery usually rely simply on dose-volume or dose-diameter isoeffect curves. Due to the sparse clinical data available, these curves have typically not considered the target location in the brain, target histology, or treatment plan conformality as parameters in the calculation. In this study, a predictive model was generated to estimate the probability of cranial neuropathies as a result of acoustic schwannoma radiosurgery.

METHODS AND MATERIALS

The dose-volume histogram reduction scheme was used to calculate the normal tissue complication probability (NTCP) from brainstem dose-volume histograms. The model's fitting parameters were optimized to provide the best fit to the observed complication data for acoustic neuroma patients treated with stereotactic radiosurgery at the University of Florida. The calculation was then applied to the remainder of the patients in the database.

RESULTS

The best fit to our clinical data was obtained using n = 0.04, m = 0.15, and alpha/beta = 2.1 Gy(-1). Although the fitting parameter m is relatively consistent with ranges found in the literature, both the volume parameter, n, and alpha/beta are much smaller than the values quoted in the literature. The fit to our clinical data indicates that brainstem, or possibly a specific portion of the brainstem, is more radiosensitive than the parameters in the literature indicate, and that there is very little volume effect; in other words, irradiation of a small fraction of the brainstem yields NTCPs that are nearly as high as those calculated for entire volume irradiation. These new fitting parameters are specific to acoustic neuroma radiosurgery, and the small volume effect that we observe may be an artifact of the fixed relationship of acoustic tumors to specific regions of the brainstem. Applying the model to our patient database, we calculate an average NTCP of 7.2% for patients who had no cranial nerve complications, and the average NTCP for was 66% for patients who sustained a cranial neuropathy. For the entire patient population, the actual percentage of patients suffering either facial or trigeminal neuropathy was 14.7%, whereas the calculated average NTCP was 14.8%.

DISCUSSION

NTCP calculations using brainstem dose-volume histograms can be used to estimate the rate of cranial neuropathies from acoustic neuroma radiosurgery. More clinical data and further study will lead to refinement of the model with time.

Image localization for frameless stereotactic radiotherapy

PURPOSE

Infrared light-emitting diodes (IRLEDs) have been used for optic-guided stereotactic radiotherapy localization at the University of Florida since 1995. The current paradigm requires stereotactic head ring placement for the patient's first fraction. The stereotactic coordinates and treatment plan are determined relative to this head ring. The IRLEDs are attached to the patient via a maxillary bite plate, and the position of the IRLEDs relative to linac isocenter is saved to file. These positions are then recalled for each subsequent treatment to position the patient for fractionated therapy. The purpose of this article was to report a method of predicting the desired IRLED locations without need for the invasive head ring.

METHODS AND MATERIALS

To achieve the goal of frameless optic-guided radiotherapy, a method is required for direct localization of the IRLED positions from a CT scan. Because it is difficult to localize the exact point of light emission from a CT scan of an IRLED, a new bite plate was designed that contains eight aluminum fiducial markers along with the six IRLEDs. After a calibration procedure to establish the spatial relationship of the IRLEDs to the aluminum fiducial markers, the stereotactic coordinates of the IRLED light emission points are determined by localizing the aluminum fiducial markers in a stereotactic CT scan.

RESULTS

To test the accuracy of direct CT determination of the IRLED positions, phantom tests were performed. The average accuracy of isocenter localization using the IRLED bite plate was 0.65 +/- 0. 17 mm for these phantom tests. In addition, the optic-guided system has a unique compatibility with the stereotactic head ring. Therefore, the isocentric localization capability was clinically tested using the stereotactic head ring as the absolute standard. The ongoing clinical trial has shown the frameless system to provide a patient localization accuracy of 1.11 +/- 0.3 mm compared with the head ring.

CONCLUSION

Optic-guided radiotherapy using IRLEDs provides a mechanism through which setup accuracy may be improved over conventional techniques. To date, this optic-guided therapy has been used only as a hybrid system that requires use of the stereotactic head ring for the first fraction. This has limited its use in the routine clinical setting. Computation of the desired IRLED positions eliminates the need for the invasive head ring for the first fraction. This allows application of optic-guided therapy to a larger cohort of patients, and also facilitates the initiation of extracranial optic-guided radiotherapy.

Linear accelerator radiosurgery in the management of brain tumours

Radiosurgery is an increasingly popular method for treating a variety of intracranial tumours. A great deal of treatment data has been accumulated suggesting that radiosurgery may be the treatment of choice for small acoustic schwannomas. Moreover, radiosurgery promises excellent tumour control and minimal risk in the treatment of small meningiomas in risky surgical locations such as the cavernous sinus. Radiosurgery offers superior local control rates for many metastatic neoplasms and has promise as an adjuvant 'boost' technique in certain malignant gliomas. This article presents a brief description of the linear accelerator, LINAC, radiosurgical technique, followed by a review of the more common applications of stereotactic radiosurgery in the treatment of intracranial neoplastic disease.

Linear accelerator radiosurgery in brain tumor management

This article begins with a brief introduction to the concepts and techniques of linear accelerator-based stereotactic radiosurgery. The expanding role of radiosurgery in the treatment of brain tumors is explored in depth, including detailed discussions of the five intracranial neoplasms most frequently treated with radiosurgery. These include both benign (i.e., vestibular schwannoma, meningioma, pituitary adenoma) and malignant (i.e., cerebral metastasis, malignant glioma) pathologies. For each of these, a thorough review of published radiosurgical results is presented along with a discussion of common treatment modalities. The role of radiosurgery in the treatment of brain tumors continues to be defined, but an effort is made to provide reasonable indications for and against radiosurgery based on the current state of the art.

Activity level and performance of weaner pigs exposed to 915 MHz microwave radiation

Microwave radiation (MWR) (915 MHz) is considered a possible source of supplementary heat for early-weaned pigs. To determine the behavioural effect of this form of heat on weaner pigs, four trials were carried out in which 64 pigs were exposed to microwave (MW) treatment at 11.4 (MW1) or 6.1 (MW2) mW cm−1 or infrared (IR) radiation at 500 W (IRR), each following a 4-d adaptation period. Pigs exposed to both MW treatments displayed greater (P < 0.05) daily percent resting time compared with IR exposed pigs [86.0 ± 1.6 vs. 82.3 ± 2.5 vs. 79.4 ± 3.7% (mean ± SD) for MW1, MW2 and IRR, respectively]. The increase in resting time was greatest after the first day of treatment and gradually returned to pretreatment levels over the course of the 3-wk experiment. The treatment effect over time was also significant (P < 0.05) between IR and both MW treatments and indicated similar patterns of resting time for the MW treatments. The pattern of resting behaviour for the IR group remained relatively unchanged throughout the experiment. Microwave exposure did not have an effect (P > 0.05) on average daily gain [0.32 ± 0.12 vs. 0.28 ± 0.07 vs. 0.30 ± 0.13 kg day−1 (mean ± SD) for IRR, MW1 and MW2, respectively]. The results indicate that 915 MHz MWR causes a power-level-dependent decrease in activity in weaner pigs. However, MW exposure does not significantly affect performance in weaner pigs. Key words: Weaner pigs, microwaves, behaviour, performance, supplementary heat

Effect of early introduction of formula vs fat-free parenteral nutrition on essential fatty acid status of preterm infants

Previous studies have used relative (%) values of plasma 18:2n-6 (18:2 omega-6) and the ratio of 20:3n-9 to 20:4n-6 (triene/tetrene) to indicate the essential fatty acid (EFA: 18:2n-6 and 18:3n-3) status of preterm infants. The extent to which these indices reflect milligrams per liter quantities of n-6 and n-3 long-chain polyunsaturated derivatives of EFA (LCPs), required for cell membrane accretion, is unknown. Thus, 18:2n-6, the triene-tetrene ratio, and n-6 and n-3 LCPs were measured in plasma phospholipid of preterm infants' cord blood (n = 22) and of preterm infants fed formula (n = 12) or of preterm infants who received fat-free parenteral nutrition (n = 15) on postnatal day 3. Whether expressed as percent or milligrams per liter, 18:2n-6 was markedly higher and the triene-tetrene ratio lower in infants fed formula than in infants who had received no lipid. However, concentrations of n-6 and n-3 LCPs were similar in the two groups of infants and significantly higher than cord values. In the absence of an exogenous lipid source, it is suggested that tissue stores of LCPs are released in response to birth.

Peak inspiratory pressure requirements in infants born weighing less than 750 g

The possibility that peak inspiratory pressure requirements or the arterial:alveolar oxygen ratio can predict the clinical outcome in infants weighing less than 750 g at birth was explored in a consecutive series. Nine of 10 infants (90%) with a peak inspiratory pressure requirement of more than 18 cm H2O at 48 hours or more than 16 cm H2O at 72 hours from age subsequently died later of respiratory causes (defined as death after 72 hours of pulmonary interstitial emphysema, bronchopulmonary dysplasia, or cor pulmonale). Twenty of 21 remaining infants (95%) survived until discharge. Using these data a 95th centile for peak inspiratory pressure requirement during the first 72 hours of life was constructed. The potential value of this centile in predicting later death of respiratory causes was examined in a separate series. Twelve of 15 infants (80%) whose peak inspiratory pressure requirements remained below the 95th centile, or were not ventilated (n = 6), survived. In contrast, 11 of 12 (92%) infants whose requirements crossed the 95th centile died later of respiratory causes. The infants who died had more radiological changes and higher mean arterial carbon dioxide pressure than survivors suggesting that the severity of the initial lung disease rather than the way that ventilation was managed determined prognosis. Peak inspiratory pressure requirement was more useful than arterial:alveolar oxygen ratio in clearly distinguishing between survivors and infants who died later of respiratory causes.

Plasma and red blood cell fatty acids of low-birth-weight infants fed their mother's expressed breast milk or preterm-infant formula

The fatty acid composition of plasma phospholipids, red blood cell (RBC) phosphatidylcholine (PC), and phosphatidylethanolamine (PE) was determined for low-birth-weight (LBW) infants when full oral feeding commenced (day 0) and after a further 28 d (day 28). They were fed their mother's expressed breast milk (PTM, n = 9), formula (SCF, n = 16) with 2% 18:3n-3 fatty acids, 20% 18:2n-6 fatty acids, or a combination of SCF and PTM (n = 11). Concentrations of all 20- and 22-carbon n-6 and n-3 fatty acids were similar among the infant groups on days 0 and 28 (mean postnatal age 42 +/- 1.3 d). The results suggest that formula with greater than or equal to 2% 18:3n-3 and a ratio of 18:2n-6 to 18:3n-3 similar to that of human milk may permit incorporation of n-3 fatty acids in LBW infant tissues equivalent to that from human milk.

Brain synaptosomal, liver, plasma, and red blood cell lipids in piglets fed exclusively on a vegetable-oil-containing formula with and without fish-oil supplements

Clinical studies showed that a decrease in red blood cell 22:6n-3 caused by feeding infants formula (F) can be prevented by supplementation with fish oil (F + O). It is not known whether fish-oil supplementation is able to support normal accretion of fatty acids with greater than or equal to 20 carbons (LCPs) in the brain. Therefore piglets were fed exclusively F + O, F, or sow milk (SM) for 15 d and their liver and brain synaptosomal fatty acids were determined. Feeding F + O corrected the low n-3 LCP in the liver phospholipid (PL) and synaptosomal phosphatidylethanolamine (PE) of piglets fed F compared with SM. An apparent compensatory increase in n-6 LCPs in liver PL and synaptosomal PE of piglets fed F compared with SM was suppressed by feeding F + O. F + O also reduced the ratio of plasma PL 20:4n-6 to 20:5n-3, important for eicosanoid metabolism. Supplementation of F with n-3 LCPs as fish oil, without n-6 LCPs, at levels giving normal brain n-3 LCP, may alter n-6 LCP accretion.

Height attainment in children with steroid-responsive nephrotic syndrome

The heights of 80 patients with steroid-responsive nephrotic syndrome (SRNS) were measured 5-24 years after diagnosis. During childhood most patients had received repeated courses of high-dose corticosteroids and prolonged maintenance therapy. Although at the time of taking corticosteroids growth was suppressed, those who had completed growth had a mean height standard deviation score (SDS) of -0.22, equivalent to a height on the 40th centile. Total corticosteroid dose prescribed was correlated only weakly with height SDS; there was no correlation between total dose and height when the post-pubertal patients were studied separately, indicating that their ultimate height attainment was not affected significantly.