Profiles of objective and subjective cognitive function in Post-COVID Syndrome, COVID-19 recovered, and COVID-19 naïve individuals.

Post-COVID Syndrome has emerged as a significant public health concern worldwide with increasing evidence to suggest that individuals who have had an acute COVID-19 infection report lingering memory and attention difficulties, even in individuals who have fully recovered and no longer experiencing symptoms of COVID-19. The present study sought to investigate the profile of objective and subjective cognitive difficulties in people who have Post-COVID Syndrome, people who have fully recovered from an acute COVID infection and people who have never had COVID-19. We further sought to explore the extent to which self-reported fatigue and stress are related to subjective and objective cognitive difficulties. 162 participants including 50 people living with Post-COVID Syndrome, 59 people who have had COVID-19 but have fully recovered and 53 people who have never experienced symptoms of COVID-19 and had never tested positive for COVID-19 were recruited from Academic Prolific to complete a series of online questionnaires and neurocognitive tasks. Subjective cognitive function was measured using the Cognitive Failures Questionnaire and objective cognitive function was measured using the Cognitron cognitive test battery. We found that objective and subjective measures of cognitive function were not significantly related, suggesting that self-reports of "brain fog" are not reflecting objectively measured cognitive dysfunction. A MANOVA revealed that subjective cognitive deficits were driven by heightened perceived stress and fatigue and not significantly related to COVID-19 status. Objective cognitive function, however, was significantly related to perceived stress and COVID status whereby we observed significant objective cognitive deficits in people who have been exposed to an acute COVID-19 infection regardless of whether they had Post-COVID Syndrome or had fully recovered, as compared to people who had never had COVID-19. This suggests that an acute infection can have long term effects on cognitive function, even without persistent COVID-19 symptoms. Encouragingly, objective cognitive function was significantly associated with time since initial infection showing that cognitive deficits improved over time for people who had recovered from COVID-19. However, we did not observe the same improvement in individuals with Post-COVID Syndrome and observed that cognitive dysfunction was significantly related to the number of neurological symptoms presently experienced. These results add to the accumulating literature that COVID-19 is associated with significant cognitive difficulties following a COVID-19 infection, which appear to improve over time for those who have recovered from COVID-19 yet persist in people living with Post-COVID Syndrome.

Just a phase? Causal probing reveals spurious phasic dependence of sustained attention.

For over a decade, electrophysiological studies have reported correlations between attention / perception and the phase of spontaneous brain oscillations. To date, these findings have been interpreted as evidence that the brain uses neural oscillations to sample and predict upcoming stimuli. Yet, evidence from simulations have shown that analysis artefacts could also lead to spurious pre-stimulus oscillations that appear to predict future brain responses. To address this discrepancy, we conducted an experiment in which visual stimuli were presented in time to specific phases of spontaneous alpha and theta oscillations. This allowed us to causally probe the role of ongoing neural activity in visual processing independent of the stimulus-evoked dynamics. Our findings did not support a causal link between spontaneous alpha / theta rhythms and behaviour. However, spurious correlations between theta phase and behaviour emerged offline using gold-standard time-frequency analyses. These findings are a reminder that care should be taken when inferring causal relationships between neural activity and behaviour using acausal analysis methods.

Assessing prospective and retrospective metacognitive accuracy following traumatic brain injury remotely across cognitive domains.

The ability to monitor one's behaviour is frequently impaired following TBI, impacting on patients' rehabilitation. Inaccuracies in judgement or self-reflection of one's performance provides a useful marker of metacognition. However, metacognition is rarely measured during routine neuropsychology assessments and how it varies across cognitive domains is unclear. A cohort of participants consisting of 111 TBI patients [mean age = 45.32(14.15), female = 29] and 84 controls [mean age = 31.51(12.27), female = 43] was studied. Participants completed cognitive assessments via a bespoke digital platform on their smartphones. Included in the assessment were a prospective evaluation of memory and attention, and retrospective confidence judgements of task performance. Metacognitive accuracy was calculated from the difference between confidence judgement of task performance and actual performance. Prospective judgment of attention and memory was correlated with task performance in these domains for controls but not patients. TBI patients had lower task performance in processing speed, executive functioning and working memory compared to controls, maintaining high confidence, resulting in overestimation of cognitive performance compared to controls. Additional judgments of task performance complement neuropsychological assessments with little additional time-cost. These results have important theoretical and practical implications for evaluation of metacognitive impairment in TBI patients and neurorehabilitation.

Online assessment of risk factors for dementia and cognitive function in healthy adults.

OBJECTIVE: Several potentially modifiable risk factors for cognitive decline and dementia have been identified, including low educational attainment, smoking, diabetes, physical inactivity, hypertension, midlife obesity, depression, and perceived social isolation. Managing these risk factors in late midlife and older age may help reduce the risk of dementia; however, it is unclear whether these factors also relate to cognitive performance in older individuals without dementia. METHOD: Data from 14 201 non-demented individuals aged >50 years who enrolled in the online PROTECT study were used to examine the relationship between cognitive function and known modifiable risk factors for dementia. Multivariate regression analyses were conducted on 4 cognitive outcomes assessing verbal and spatial working memory, visual episodic memory, and verbal reasoning. RESULTS: Increasing age was associated with reduced performance across all tasks. Higher educational achievement, the presence of a close confiding relationship, and moderate alcohol intake were associated with benefits across all 4 cognitive tasks, and exercise was associated with better performance on verbal reasoning and verbal working memory tasks. A diagnosis of depression was negatively associated with performance on visual episodic memory and working memory tasks, whereas being underweight negatively affected performance on all tasks apart from verbal working memory. A history of stroke was negatively associated with verbal reasoning and working memory performance. CONCLUSION: Known modifiable risk factors for dementia are associated with cognitive performance in non-demented individuals in late midlife and older age. This provides further support for public health interventions that seek to manage these risk factors across the lifespan.

Adaptive working memory strategy training in early Alzheimer's disease: randomised controlled trial.

BACKGROUND: Interventions that improve cognitive function in Alzheimer's disease are urgently required. AIMS: To assess whether a novel cognitive training paradigm based on 'chunking' improves working memory and general cognitive function, and is associated with reorganisation of functional activity in prefrontal and parietal cortices (trial registration: ISRCTN43007027). METHOD: Thirty patients with mild Alzheimer's disease were randomly allocated to receive 18 sessions of 30 min of either adaptive chunking training or an active control intervention over approximately 8 weeks. Pre- and post-intervention functional magnetic resonance imaging (fMRI) scans were also conducted. RESULTS: Adaptive chunking training led to significant improvements in verbal working memory and untrained clinical measures of general cognitive function. Further, fMRI revealed a bilateral reduction in task-related lateral prefrontal and parietal cortex activation in the training group compared with controls. CONCLUSIONS: Chunking-based cognitive training is a simple and potentially scalable intervention to improve cognitive function in early Alzheimer's disease.

Putative cortical dopamine levels affect cortical recruitment during planning.

Planning, the decomposition of an ultimate goal into a number of sub-goals is critically dependent upon fronto-striatal dopamine (DA) levels. Here, we examined the extent to which the val158met polymorphism in the catechol O-methyltransferase (COMT) gene, which is thought to primarily alter cortical DA levels, affects performance and fronto-parietal activity during a planning task (Tower of London). COMT genotype was found to modulate activity in the left superior posterior parietal cortex (SPC) during planning, relative to subtracting, trials. Specifically, left SPC blood oxygenation level-dependent (BOLD) response was reduced in groups with putatively low or high cortical DA levels (COMT homozygotes) relative to those with intermediate cortical DA levels (COMT heterozygotes). These set of results are argued to occur either due to differences in neuronal processing in planning (and perhaps subtracting) caused by the COMT genotype and/or the cognitively heterogeneous nature of the TOL, which allows different cognitive strategies to be used whilst producing indistinguishable behavioural performance in healthy adults. The implications of this result for our understanding of COMT's effect on cognition in health and disease are discussed.

Prefrontal dopamine levels determine the balance between cognitive stability and flexibility.

A key mechanism by which the prefrontal cortex (PFC) supports goal-oriented behaviors is attentional set formation: the formation and maintenance of an attentional bias toward relevant features. It has previously been proposed that a common single nucleotide polymorphism (val158met) in the gene that codes for the catechol O-methyltransferase (COMT) enzyme may affect an individual's ability to form and maintain an attentional set by modulating PFC dopamine (DA) levels. Here, we present data from a functional magnetic resonance imaging study that investigated the effect of this polymorphism on the tendency for older adults to display set-like behavior, and we compare these results to preexisting data from Parkinson's Disease (PD) patients. Our results demonstrate that putatively different levels of PFC DA predict both attentional set formation and right dorsolateral PFC (DLPFC) activation. More specifically, while for PD patients, val homozygotes showed heightened DLPFC activation and increased set-like behavior, for healthy older adults, the opposite pattern of results was observed. This interaction between COMT genotype and PD accords well with previous studies that have shown an excess of DA in the PFC in early PD patients and, furthermore, supports the hypothesis that there is an inverted-U shaped functional relationship between PFC DA levels and attentional set formation.

The neural basis of effective memory therapy in a patient with limbic encephalitis.

BACKGROUND: An fMRI study is described in which a postencephalitic woman with amnesia used a wearable camera which takes photographs passively, without user intervention, to record and review recent autobiographical events. "SenseCam" generates hundreds of images which can subsequently be reviewed quickly or one by one. RESULTS: Memory for a significant event was improved substantially when tested after 4.5 weeks, if the patient viewed SenseCam images of the event every 2 days for 3 weeks. In contrast, after only 3.5 weeks, her memory was at chance levels for a similarly significant event which was reviewed equally often, but using a written diary. During the fMRI scan, the patient viewed images of these two events, plus images of an unrehearsed event and images from a novel "control" event that she had never experienced. There was no difference in behavioural responses or in activation when the unrehearsed and novel conditions were compared. Relative to the written-rehearsed condition, successful recognition of the images in the SenseCam-rehearsed condition was associated with activation of frontal and posterior cortical regions associated with normal episodic memory. CONCLUSION: SenseCam images may provide powerful cues that trigger the recall and consolidation of stored but inaccessible memories.

Parenting interventions and the prevention of unintentional injuries in childhood: systematic review and meta-analysis.

OBJECTIVES: To evaluate the effectiveness of parenting interventions in preventing unintentional injury and increasing parental safety practices. DATA SOURCES: A range of medical and social science electronic databases were searched. Abstracts from the first to seventh World conferences on injury prevention and control and the journal Injury Prevention were hand searched. REVIEW METHODS: Randomized controlled trials (RCTs), non-randomized controlled trials (non-RCTs) and controlled before and after studies, providing parenting interventions to parents of children aged 0-18 years and reporting injuries, safety equipment or safety practices were included. Studies were selected, data extracted and quality appraised independently by two reviewers. Pooled relative risks were estimated using random effect models. RESULTS: Fifteen studies (11 RCTs) were included, 11 of which were home visiting programmes and two of which were paediatric practice-based interventions. Thirteen studies recruited families at risk of adverse child health outcomes. Intervention arm families had a significantly lower risk of injury (RR 0.82, 95% CI 0.71-0.95), as measured by self-report of medically or non-medically attended injury. Several studies found fewer home hazards, a home environment more conducive to child safety, or a greater number of safety practices in intervention arm families. CONCLUSIONS: Parenting interventions, most commonly provided within the home, using multi-faceted interventions appear to be effective in reducing unintentional child injury. Further research is required to explore the mechanisms by which parenting interventions reduce injury, the features of interventions that are necessary to reduce injury, and their generalizability to different population groups.

Parenting interventions for the prevention of unintentional injuries in childhood.

BACKGROUND: Parent education and training programmes can improve maternal psychosocial health, child behavioural problems and parenting practices. This review assesses the effects of parenting interventions for reducing child injury. OBJECTIVES: To assess the effects of parenting interventions for preventing unintentional injury as well as increasing possession and use of safety equipment and parental safety practices. SEARCH STRATEGY: We searched CENTRAL, MEDLINE, EMBASE, Biological Abstracts, Psych INFO, Sociofile, Social Science Citation Index, CINAHL, Dissertation Abstracts, ERIC, DARE, ASSIA, Web of Science, SIGLE and ZETOC. We also handsearched abstracts from the World Conferences on Injury Prevention & Control and the journal Injury Prevention. The searches were conducted in May 2005. SELECTION CRITERIA: We included randomised controlled trials (RCTs), non-randomised controlled trials (non-RCTs) and controlled before and after studies (CBAs), which evaluated parenting interventions administered to parents of children aged 18 years and under, and reported outcome data on injuries (unintentional or unspecified intent), and possession and use of safety equipment or safety practices. Parenting interventions were defined as those with a specified protocol, manual or curriculum aimed at changing knowledge, attitudes or skills covering a range of parenting topics. DATA COLLECTION AND ANALYSIS: Studies were selected, data were extracted and quality appraised independently by two authors. Pooled relative risks (RR) were estimated using random effect models. MAIN RESULTS: Fifteen studies were included in the review: 11 RCTs (one included a CBA within the same study), one non-RCT, one study contained both randomised and non-randomised arms and two CBAs. Two provided solely educational interventions. Thirteen provided interventions comprising parenting education and other support services; 11 of which were home visiting programmes and two of which were paediatric practice-based interventions. Thirteen studies recruited families at risk of adverse child health outcomes. Nine RCTs were included in the primary meta-analysis, which indicated that intervention families had a significantly lower risk of injury (RR 0.82, 95% CI 0.71 to 0.95). Several studies found fewer home hazards, a home environment more conducive to child safety, or a greater number of safety practices in intervention families. AUTHORS' CONCLUSIONS: Parenting interventions, most commonly provided within the home using multi-faceted interventions may be effective in reducing child injury. The evidence relates mainly to interventions provided to families at risk of adverse child health outcomes. Further research is required to explore mechanisms by which these interventions reduce injury, the features of parenting interventions that are necessary or sufficient to reduce injury and the generalisability to different population groups.

When thoughts become action: an fMRI paradigm to study volitional brain activity in non-communicative brain injured patients.

The assessment of voluntary behavior in non-communicative brain injured patients is often challenging due to the existence of profound motor impairment. In the absence of a full understanding of the neural correlates of consciousness, even a normal activation in response to passive sensory stimulation cannot be considered as proof of the presence of awareness in these patients. In contrast, predicted activation in response to the instruction to perform a mental imagery task would provide evidence of voluntary task-dependent brain activity, and hence of consciousness, in non-communicative patients. However, no data yet exist to indicate which imagery instructions would yield reliable single subject activation. The aim of the present study was to establish such a paradigm in healthy volunteers. Two exploratory experiments evaluated the reproducibility of individual brain activation elicited by four distinct mental imagery tasks. The two most robust mental imagery tasks were found to be spatial navigation and motor imagery. In a third experiment, where these two tasks were directly compared, differentiation of each task from one another and from rest periods was assessed blindly using a priori criteria and was correct for every volunteer. The spatial navigation and motor imagery tasks described here permit the identification of volitional brain activation at the single subject level, without a motor response. Volunteer as well as patient data [Owen, A.M., Coleman, M.R., Boly, M., Davis, M.H., Laureys, S., Pickard J.D., 2006. Detecting awareness in the vegetative state. Science 313, 1402] strongly suggest that this paradigm may provide a method for assessing the presence of volitional brain activity, and thus of consciousness, in non-communicative brain-injured patients.

Variation in how mothers, health visitors and general practitioners use the personal child health record.

BACKGROUND: In the UK, a national personal child health record (PCHR) with local adaptations is in widespread use. Previous studies report that parents find the PCHR useful and that health visitors use it more than other health professionals. This study was carried out in Nottingham, where the local PCHR is similar to the national PCHR. OBJECTIVES: To explore variation in use of the PCHR made by mothers with differing social characteristics, to compare heath visitors' and general practitioners' (GPs') use of the PCHR, and to compare health visitors' and GPs' perceptions of the PCHR with those of mothers for whose children they provide care. METHODS: Questionnaires to 534 parents registered with 28 general practices and interviews with a health visitor and GP at each practice. A score per mother for perceived usefulness of the PCHR was developed from the questionnaire, and variation in the score was investigated by linear regression adjusted for clustering. RESULTS: Four hundred and one (75%) questionnaires were returned. Three hundred and twenty-five (82%) mothers thought the PCHR was very good or good. Higher scores for usage of the PCHR were significantly associated with teenage and first-time mothers, but no association was found with mother's social class, education or being a single parent. There was no association between variation in the score and practice, health visitor or GP characteristics. Mothers, health visitors and GPs reported that mothers took the PCHR to baby clinic more frequently than when seeing their GP, and that health visitors wrote in the PCHR more frequently than GPs. Eighteen (67%) health visitors and 20 (71%) GPs said they had difficulty recording information in the PCHR. CONCLUSION: The PCHR is used by most mothers and is important for providing health promotion material to all families with young children. It may be particularly useful for first-time and teenage mothers.

Gamma knife radiosurgery for cerebral arteriovenous malformations.

Since its introduction, gamma knife radiosurgery has become an important treatment modality for cerebral arteriovenous malformations. This paper is a brief overview of the technique used, of the clinical results achieved and of the experience gained in Sheffield.

Gamma knife stereotactic radiosurgery for unilateral acoustic neuromas.

OBJECTIVE: To evaluate the clinical results achievable using current techniques of gamma knife stereotactic radiosurgery to treat sporadic unilateral acoustic neuromas. METHODS: A retrospective review of 234 consecutive patients treated for unilateral acoustic neuromas between 1996 and 1999, with a mean (SD) follow up of 35 (16) months. Tumour control was assessed with serial radiological imaging and by the need for surgical intervention. Hearing preservation was assessed using Gardner-Robertson grades. Details of complications including cranial neuropathies and non-specific vestibulo-cochlear symptoms are included. RESULTS: A tumour control rate in excess of 92% was achieved, with only 3% of patients undergoing surgery after radiosurgery. Results were less good for larger tumours, but control rates of 75% were achieved for 35-45 mm diameter lesions. Of patients with discernible hearing, Gardner-Robertson grades were unchanged in 75%. Facial nerve function was adversely affected in 4.5%, but fewer than 1% of patients had persistent weakness. Trigeminal symptoms improved in 3%, but developed in 5% of patients, being persistent in less than 1.5%. Transient non-specific vestibulo-cochlear symptoms were reported by 13% of patients. CONCLUSIONS: Tumour control rates, while difficult to define, are comparable after radiosurgery with those experienced after surgery. The complications and morbidity after radiosurgery are far less frequent than those encountered after surgery. This, combined with its minimally invasive nature, may make radiosurgery increasingly the treatment of choice for small and medium sized acoustic neuromas.

Characterization of an ecto-phosphatase activity in the human parasite Trichomonas vaginalis.

We have characterized phosphatase activity present on the external surface of Trichomonas vaginalis, using intact living parasites. This enzyme hydrolyzes the substrate p-nitrophenylphosphate (p-NPP) at a rate of 134.3+/-14.8 nmol Pi/h per 10(7) cells. This phosphatase activity decreased by increasing the pH from 6.8 to 8.4, a pH range in which cell viability was maintained for at least 1 h. Experiments using classical inhibitors of acid phosphatases, such as ammonium molybdate and sodium fluoride, as well as inhibitors of phosphotyrosine phosphatase, such as sodium orthovanadate, [monoperoxo(picolinato)oxovanadate(V)] (mpV-PIC) and [potassiumbisperoxo(1,10-phenanthroline)oxovanadate(V)] (bpV-PHEN), showed a decrease in this phosphatase activity, with different patterns of inhibition. Cytochemical analysis showed the localization of this enzyme on the parasite surface (cell body and flagellum) and in intracellular vacuoles. Phosphatase reaction products were also observed in exocytosed membrane-bound material.

Assessing the quality of preschool child health surveillance in primary care: a pilot study in one health district.

OBJECTIVE: To develop a framework for measuring the quality of preschool child health surveillance acceptable to primary health care teams and measurable at individual primary health care team level. DESIGN: Published research evidence was identified and criteria developed by a local multidisciplinary expert group. The criteria were discussed with primary health care teams. How well they were achieved was assessed. SETTING: Twenty-eight general practices in one health authority area. METHODS: Data collection included observation of baby clinics, interviews with health visitors and general practitioners (GPs), questionnaires to parents, collation of child health surveillance reviews recorded in personal child health records and immunization rates. RESULTS: The criteria for assessing preschool child health surveillance were thought to be acceptable and achievable by primary health care teams. Fifteen of the 22 criteria used to assess baby clinics were met by over 90 of practices. Almost all practices completed child health surveillance reviews within a standard time and achieved 90 coverage for primary immunizations. At many practices, less than 90 of parents felt welcome at the baby clinic, usually had enough time to talk to their health visitor or had the purpose or results of the 6 to 8 week child health surveillance review explained to them. GPs were less likely than health visitors to discuss health promotion at child health surveillance reviews (chi(2) 11.52, P = 0.0007). Few practices had a call-up and recall system for all reviews. CONCLUSION: The framework that we developed for assessing preschool child health surveillance was acceptable and achievable by primary health care teams.

What can students learn from studying medicine in literature?

OBJECTIVE: To identify what students can learn from studying medicine and literature as part of a final-year special study module in general practice. METHOD: The project reports and evaluation forms completed by all eight students who had chosen to study medicine and literature as part of their special study module in general practice at Nottingham University Medical School were analysed qualitatively. RESULTS: Students said that they gained a greater understanding of the patient's experience of illness, as a result of the texts they had read. They learned how illness can affect family or friends of the patient and about the psychological impact of physical illness. Most students thought their future care of patients would be influenced by what they had learned. Studying medicine in literature during a clinical attachment allowed students to draw comparisons between literature and their clinical experience. DISCUSSION: This study is based on a small number of students who chose to study medicine in literature. The results may not be generalizable to all medical students and not all students may be receptive to this method of learning. However, we recommend that students who are interested should be given the opportunity to study medicine in literature during their clinical years. This can enable them to reflect on their clinical experience and can provide a more profound understanding of the consequences of illness for the patient and their family.

The clinician's role in meeting patient information needs: suggested learning outcomes.

BACKGROUND: Patients have always fulfilled their information needs from a variety of different sources over time. Clinician-patient consultations are one part of that process. Some patients have increasing opportunities to obtain information through new sources such as the internet, touch-screens, and patient-held records. Others remain poorly informed. OBJECTIVES: To identify learning outcomes for clinicians in meeting patient information needs and working with well-informed patients. DESIGN: Four-stage multicentre multidisciplinary qualitative study. SETTING AND SUBJECTS: (1) Semistructured interviews with 20 clinicians in Glasgow; (2) semistructured interviews with 52 clinicians in Nottingham and London; (3) testing of consensus by postal questionnaire and Delphi method amongst 37 clinicians in medicine, nursing and the professions allied to medicine, and (4) conference to discuss results. RESULTS: 46 learning outcomes were identified in the eight areas of: placing a higher priority on patient information and education; understanding the patient's information needs and environment; understanding the emotional aspects of learning; developing patient understanding; helping patients to understand about health care and health care information; learning from the patient; knowing about information sources and their use, and issues of multidisciplinary working. CONCLUSIONS: The suggested learning outcomes provide the basis for wider discussion, for possible inclusion in curricula both at undergraduate and continuing education levels, and as the basis for the development of new educational materials.

Distortion in magnetic resonance images obtained for stereotactic localization. Case report.

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.

Development of a relocatable frame technique for gamma knife radiosurgery. Technical note.

OBJECT: One of the limiting factors in gamma knife radiosurgery is the restriction to one treatment imposed by the fixed stereotactic frame. The ability, in selected cases, to remove the frame and replace it on a subsequent occasion in the same location would facilitate fractionated treatments and provide flexibility in the timing of treatment delivery. It is the purpose of this work to investigate techniques for frame fixation and for essential verification of frame position once it has been reapplied. METHODS: A technique is proposed that requires four surgical self-tapping screws to be inserted into the skull. Aluminum pins are inserted through the frame pillars and are tightened against the head of the screws, providing a firm fixation of the frame. Pin lengths are recorded on gauges to ensure reproducibility of the position. In phantom tests, test objects were localized (using the angiographic localizer) before and after each of five frame removal/reapplications to test the reproducibility of frame position. The mean error in the observed target coordinates was 0.3 mm and the maximum error observed was 0.7 mm, indicating that the frame can be reapplied with some confidence. Repetition of bubble skull measurements has been investigated as a means of verifying that the frame was repositioned correctly; however, reproducibility of patient measurements was found to be poor even when no frame movement had occurred. In contrast, the use of a radiotherapy simulator to obtain repeated lateral and anteroposterior projections of the head was shown to be capable of detecting frame movements of as little as 1 mm. CONCLUSIONS: Using this technique of frame application facilitates the reapplication of the frame with an accuracy of plus or minus 0.7 mm. Bubble measurements are inadequate for the detection of frame movement. Simple techniques in which a radiotherapy simulator is used can verify correct frame placement and indicate frame movements of less than 1 mm.