Brain-water diffusion coefficients reflect the severity of inherited prion disease

OBJECTIVE

Inherited prion diseases are progressive neurodegenerative conditions, characterized by cerebral spongiosis, gliosis, and neuronal loss, caused by mutations within the prion protein (PRNP) gene. We wished to assess the potential of diffusion-weighted MRI as a biomarker of disease severity in inherited prion diseases.

METHODS

Twenty-five subjects (mean age 45.2 years) with a known PRNP mutation including 19 symptomatic patients, 6 gene-positive asymptomatic subjects, and 7 controls (mean age 54.1 years) underwent conventional and diffusion-weighted MRI. An index of normalized brain volume (NBV) and region of interest (ROI) mean apparent diffusion coefficient (ADC) for the head of caudate, putamen, and pulvinar nuclei were recorded. ADC histograms were computed for whole brain (WB) and gray matter (GM) tissue fractions. Clinical assessment utilized standardized clinical scores. Mann-Whitney U test and regression analyses were performed.

RESULTS

Symptomatic patients exhibited an increased WB mean ADC (p = 0.006) and GM mean ADC (p = 0.024) compared to controls. Decreased NBV and increased mean ADC measures significantly correlated with clinical measures of disease severity. Using a stepwise multivariate regression procedure, GM mean ADC was an independent predictor of Clinician's Dementia Rating score (p = 0.001), Barthel Index of activities of daily living (p = 0.001), and Rankin disability score (p = 0.019).

CONCLUSIONS

Brain volume loss in inherited prion diseases is accompanied by increased cerebral apparent diffusion coefficient (ADC), correlating with increased disease severity. The association between gray matter ADC and clinical neurologic status suggests this measure may prove a useful biomarker of disease activity in inherited prion diseases.

Relationship between the IQ of people with Prader-Willi syndrome and that of their siblings: evidence for imprinted gene effects

BACKGROUND

Genetic disorders occasionally provide the means to uncover potential mechanisms linking gene expression and physical or cognitive characteristics or behaviour. Prader-Willi syndrome (PWS) is one such genetic disorder in which differences between the two main genetic subtypes have been documented (e.g. higher verbal IQ in one vs. higher performance IQ in the other; slower than normal reaction time in one vs. normal in the other). In a population study of PWS, the IQ distribution of people with PWS was approximately normal. This raises the question of whether this distribution arose from a systematic effect of PWS on IQ (hypothesis 1) or whether it was the fortuitous result of random effects (hypothesis 2).

METHOD

The correlation between PWS and sibling IQ was determined in order to discriminate between the two hypotheses. In the first case we would expect the correlation to be similar to that found in the general population (0.5); in the second case it would be zero.

RESULTS

It was found that the overall PWS-sibling IQ correlation was 0.3 but that the two main genetic subtypes of PWS differed in their familial IQ relationships. As expected, the IQs of normal siblings correlated 0.5, and this was also the case with one genetic subtype of PWS (uniparental disomy) and their siblings, while the other subtype IQ correlated -0.07 with sibling IQ.

CONCLUSIONS

This is a potentially powerful result that gives another clue to the role of genes on chromosome 15 in the determination of IQ. It is another systematic difference between the genetic subtypes of PWS, which needs an explanation in terms of the very small genetic differences between them.

The phenomenology and diagnosis of psychiatric illness in people with Prader-Willi syndrome

BACKGROUND

Psychotic illness is strongly associated with the maternal uniparental disomy (mUPD) genetic subtype of Prader-Willi syndrome (PWS), but not the deletion subtype (delPWS). This study investigates the clinical features of psychiatric illness associated with PWS. We consider possible genetic and other mechanisms that may be responsible for the development of psychotic illness, predominantly in those with mUPD.

METHOD

The study sample comprised 119 individuals with genetically confirmed PWS, of whom 46 had a history of psychiatric illness. A detailed clinical and family psychiatric history was obtained from these 46 using the PAS-ADD, OPCRIT, Family History and Life Events Questionnaires.

RESULTS

Individuals with mUPD had a higher rate of psychiatric illness than those with delPWS (22/34 v. 24/85, p<0.001). The profile of psychiatric illness in both genetic subtypes resembled an atypical affective disorder with or without psychotic symptoms. Those with delPWS were more likely to have developed a non-psychotic depressive illness (p=0.005) and those with mUPD a bipolar disorder with psychotic symptoms (p=0.00005). Individuals with delPWS and psychotic illness had an increased family history of affective disorder. This was confined exclusively to their mothers.

CONCLUSIONS

Psychiatric illness in PWS is predominately affective with atypical features. The prevalence and possibly the severity of illness are greater in those with mUPD. We present a 'two-hit' hypothesis, involving imprinted genes on chromosome 15, for the development of affective psychosis in people with PWS, regardless of genetic subtype.

The course and outcome of psychiatric illness in people with Prader-Willi syndrome: implications for management and treatment

BACKGROUND

This study is part of a larger UK-wide study investigating psychiatric illness in people with Prader-Willi syndrome (PWS), and describes the longitudinal aspect of psychiatric illness, in particular psychotic illness, and examines the use and role of psychotropic medication.

METHOD

A total of 119 individuals with genetically confirmed PWS were included in the study. An informant-based questionnaire was administered for each participant to screen for a history of psychopathology. Those who screened positive were visited at their homes to obtain further information. This assessment included a full psychiatric history and mental state examination using the Psychiatric Assessment Schedule for Adults with Developmental Disability and the Operational Criteria Checklist for psychotic and affective illness to collect information regarding phenomenology and course of illness, and a modified life events questionnaire. At the end of the study period, informant-based telephone interviews were again carried out, up to 2.5 years after the initial screening. Information regarding medication usage was collected.

RESULTS

The results confirm previous findings that psychiatric illness in people with PWS resembles an affective disorder. Individuals with the maternal uniparental disomy genetic subtype had a more severe course of illness than those with the deletion genetic subtype in terms of a greater risk of recurrence, more episodes, higher incidence and a possibly poorer response to medication with more side-effects. Individuals with a recurrent episode during the follow-up period had a poorer course of illness. Selective serotonin reuptake inhibitor medication is frequently used, and beneficial effects may reflect fundamental pathological processes in PWS. Mood-stabilizing medication was found to be of little benefit and reasons for this are examined.

CONCLUSION

The longitudinal course of psychiatric illness and response to medication in people with PWS is fully described. Further research is needed regarding the effect of psychotropic medications, particularly mood-stabilizing medication. These data will enable informed decisions to be made regarding management options and provide information on the possible long-term outcome of illness.

COSMIC 2005

The Catalogue Of Somatic Mutations In Cancer (COSMIC) database and web site was developed to preserve somatic mutation data and share it with the community. Over the past 25 years, approximately 350 cancer genes have been identified, of which 311 are somatically mutated. COSMIC has been expanded and now holds data previously reported in the scientific literature for 28 known cancer genes. In addition, there is data from the systematic sequencing of 518 protein kinase genes. The total gene count in COSMIC stands at 538; 25 have a mutation frequency above 5% in one or more tumour type, no mutations were found in 333 genes and 180 are rarely mutated with frequencies <5% in any tumour set. The COSMIC web site has been expanded to give more views and summaries of the data and provide faster query routes and downloads. In addition, there is a new section describing mutations found through a screen of known cancer genes in 728 cancer cell lines including the NCI-60 set of cancer cell lines.

CD36 expression and its relationship with obesity in blood cells from people with and without Prader-Willi syndrome

Although Prader-Willi syndrome (PWS) has been linked to the loss of function of imprinted genes in 15q11q13, very little is known about the pathogenesis. Using quantitative real-time PCR, we have confirmed the previous observation of an abnormality of CD36 expression in cells with maternal uniparental disomy 15, obtained from a proband with mosaicism for PWS, by demonstrating reduced expression levels in blood cells from a series of non-mosaic probands with PWS. Furthermore, we have extended these observations to show that CD36 expression in a non-PWS population is inversely correlated with body mass index but that this correlation does not hold in PWS. CD36 which maps to 7q11.2 is the first gene outside the 15q11q13 region whose level of expression appears to be reduced in people with PWS. Low CD36 expression levels in PWS point to an abnormal control of lipid and glucose homeostasis which may explain the insatiable hunger in these patients.

Phosphodiesterase 11 (PDE11) regulation of spermatozoa physiology

Fertilization is well correlated with sperm concentration, rate of forward motility, and percentage of live, uncapacitated ejaculated spermatozoa, which is regulated in part by cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Phosphodiesterases (PDEs) hydrolyze cyclic nucleotides to their corresponding monophosphates, thereby counterbalancing the activities of cAMP and cGMP, and PDE11 is highly expressed in the testis, prostate, and developing spermatozoa. However, a physiological role of PDE11 is not known. We generated PDE11 knockout (PDE11-/-) mice to investigate the role of PDE11 in spermatozoa physiology. Ejaculated sperm from PDE11-/- mice displayed reduced sperm concentration, rate of forward progression, and percentage of live spermatozoa. Pre-ejaculated sperm from PDE11-/- mice displayed increased premature/spontaneous capacitance. These data are consistent with human data and suggest a role for PDE11 in spermatogenesis and fertilization potential. This is the first phenotype described for the PDE11-/- mouse and the first report of a physiological role for PDE11.

Cognitive abilities and genotype in a population-based sample of people with Prader-Willi syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is characterized by extreme floppiness at birth, impaired sexual development, short stature, severe over-eating, characteristic physical features and learning disabilities (LD). Impaired social cognition, literal mindedness and cognitive inflexibility are also present. The syndrome has two main genetic subtypes that both result in the failure of expression of maternally imprinted genes on chromosome 15 at the locus q11-13.

METHODS

Through multiple sources, we attempted to identify all people with PWS living in one health region in the UK. Additional people with PWS identified in other regions were also recruited to augment the study sample. A comparison group of people with LD as a result of aetiologies other than PWS was also identified. All people from these three groups, over age three, who gave their consent, were assessed using tests of ability and attainment. In addition, their main carers were interviewed using a semistructured interview. Blood samples for genetic diagnosis were obtained from all consenting participants.

FINDINGS

The IQ distribution of the population sample was approximately normal with a mean IQ 40 points below that of the general population. There were systematic differences between the two main genetic subtypes. Those with disomies differed in cognitive profiles from both those with deletions and the comparison LD group (the latter two groups were very similar) in terms of better verbal abilities and impaired coding ability. Some people with PWS deletions had strong visuospatial skills.

INTERPRETATION

We propose that the normal distribution of IQ, shifted downwards relative to that of the general population, is the result of a global effect on IQ of the PWS gene(s), and that the different cognitive profile seen in those with chromosome 15 maternal disomies is a specific effect of a gene, or genes, on chromosome 15 which is differentially either expressed or not expressed in those with disomies relative to those with deletions. One hypothesis is that these subtle cognitive differences are a manifestation of the genetic influences of gender-specific imprinted genes on cerebral lateralization. This requires further investigation.

Academic underachievement by people with Prader-Willi syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is a genetically determined neurodevelopmental disorder that is associated with the under-expression of maternally imprinted genes at the 15q11-q13 chromosomal locus. In addition to a characteristic physical and behavioural phenotype, those with the syndrome have impaired social cognition, literal mindedness and inflexibility. The present authors investigated the relationship between the PWS cognitive and behavioural phenotype, educational experience, and levels of attainment in reading, writing and arithmetic.

METHODS

All subjects from a population-based sample of people with PWS, augmented by those with PWS living in other regions together with a contrast group of people with learning disability (LD) of other aetiologies, are included in the present study. Those children over 3 years of age whose families consented or adults who themselves consented were assessed for ability and attainment (over 7 years of age), and information on functional ability was also obtained from an informant. Underachievement was defined as the difference between the score predicted from full-scale IQ and the actual achievement score.

RESULTS

Commonly, levels of achievement were lower than would have been predicted on the basis of IQ among those in the groups with PWS and LD. In the group with PWS, underachievement across academic domains was positively correlated with the percentage of time in education in a special school and negatively correlated with Vineland Socialization domain standard score. There were no across-domain significant correlations in the group with LD. When using multiple regression analysis, the percentage of time in special school was the only predictor of underachievement and only in the group with PWS. However, some children with PWS in special schools did achieve as expected in at least one academic domain.

CONCLUSIONS

Children with PWS may be placed in special schools largely because of their behavioural problems or physical disabilities, or expectations based on their PWS status. Their intellectual abilities may well be masked by their immature social behaviour. The present authors propose that a failure to recognize and address the specific educational needs which follow from this combination of poor socialization skills and complex maladaptive behaviours, in the context of relatively mild LD, may explain their findings.

Behavioural phenotypes associated with specific genetic disorders: evidence from a population-based study of people with Prader-Willi syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is a genetic disorder resulting in obesity, short stature, cryptorchidism, learning disabilities (mental retardation) and severe neonatal hypotonia. Associated with the syndrome are a number of behaviours that are sufficiently distinctive that the syndrome is considered to have a specific 'behavioural phenotype'.

METHODS

Through multiple sources we attempted to identify all people with PWS living in one region in the U K. This cohort was augmented by people with PWS from other regions, and a contrast group of people with learning disabilities of varied aetiologies. The main carers were interviewed, using structured and semi-structured interview schedules, to establish the presence and severity of specific behaviours, and PWS diagnostic criteria. The intellectual functioning and attainments of all were determined. Blood samples were obtained for genetic diagnosis from all consenting participants.

RESULTS

Although excessive eating was recognized as a potentially severe problem in those with PWS, it was almost universally controlled by food restriction, and therefore not seen as a 'problem behaviour'. Those with PWS differed from a learning disabled group of other aetiologies in the prevalence rates of skin picking, temper tantrums, compulsive behaviours and mood fluctuations, and also in the profile of their adaptive behaviours.

CONCLUSIONS

The study confirms the distinct behavioural phenotype of PWS. Specific behaviours occurred significantly more frequently in PWS, compared with an age and BMI matched learning disabled comparison group. A factor analysis of the behaviours involved resulted in three factors that we hypothesized to be independent, and to arise from different mechanisms.

A study of the influence of different genotypes on the physical and behavioral phenotypes of children and adults ascertained clinically as having PWS

A population-based cohort of people with a clinical diagnosis of Prader-Willi syndrome (PWS) was genetically assessed using molecular diagnostic methods and subsequently divided into the following genetic subtypes involving chromosome 15: 'deletion', 'disomy' and genetically negative (referred to as 'PWS-like'). The physical and behavioral characteristics of the three groups were compared in order to evaluate the unique characteristics of the phenotype resulting from loss of expression of imprinted genes at 15q11q13 (PWS vs. PWS-like cases), the possible effect of either haploid insufficiency of non-imprinted genes (deletion cases), or gain of function of imprinted genes (disomy cases) located within the PWS critical region at 15q11q13. In this study, the main differences between probands with either a deletion or disomy are considered, and the possible involvement of contributing genes discussed. The differences within the PWS group proved difficult to quantify. It would appear that haploid insufficiency or gain of function are more subtle contributors than gender-specific genomic imprinting in the production of the PWS phenotype.

Prevalence of, and risk factors for, physical ill-health in people with Prader-Willi syndrome: a population-based study

The medical findings from a population-based study of Prader-Willi syndrome (PWS) are discussed (in which birth incidence of PWS was estimated at 1:22,000 and death rate at over 3% per annum). In this study the prevalence of specific medical disorders that might account for a shortened life expectancy were investigated. Of all people with a possible diagnosis of PWS, only those meeting clinical criteria and/or with a confirmed genetic diagnosis were included in the study. Sixty-six individuals, 40 males and 26 females with a mean age of 19 years (range of 0 to 46 years) agreed to participate in the population-based study group. A prevalence rate of 25% for non-insulin dependent diabetes mellitus (NIDDM) was found in adults. Mean age at onset was 20 years. Those with NIDDM had a higher past maximum body weight and a greater likelihood of positive family history. Nearly 50% across the age groups reported a history of recurrent respiratory infections. High rates of fractures (29%), leg ulceration (22% in adults), sleep disorders (20%), and severe scoliosis (15% in childhood) were also reported. It is postulated that hypotonia is a possible contributory factor to the risk of strabismus, scoliosis, and respiratory infections. Other causes of morbidity, in particular the high rates of NIDDM, may be due to a failure to manage over-eating resulting in severe obesity. Early diagnosis and clear guidance to families about these risks and how they might be prevented is recommended. It is hypothesized that the high pain threshold may result in the presence of some illness not being apparent.

Prader-Willi syndrome, compulsive and ritualistic behaviours: the first population-based survey

BACKGROUND

Obsessive-compulsive disorder has been reported in association with Prader-Willi syndrome.

AIMS

To report the nature and prevalence of compulsive and similar symptoms associated with Prader-Willi syndrome in a population ascertained as completely as possible.

METHOD

Attempted complete ascertainment of people with Prader-Willi syndrome in eight English counties. Administration of standardised rating scales and a structured interview. Comparison with people with learning disability and high body mass indices.

RESULTS

Prader-Willi syndrome was associated with high rates of ritualistic behaviours, such as the need to ask or to tell something, insistence on routines, hoarding and ordering objects and repetitive actions and speech, compared with the control group, and was negatively correlated with IQ and socialisation age. Typical obsessive-compulsive symptoms, such as checking, counting and cleaning compulsions or obsessional thoughts, were not found.

CONCLUSIONS

Ritualistic and compulsive behaviours occur more frequently in association with Prader-Willi syndrome than among people with intellectual disability and significant obesity.

The recovery of cognitive function after general anesthesia in elderly patients: a comparison of desflurane and sevoflurane

We evaluated the cognitive recovery profiles in elderly patients after general anesthesia with desflurane or sevoflurane. After IRB approval, 70 ASA physical status I-III consenting elderly patients (> or =65 yr old) undergoing total knee or hip replacement procedures were randomly assigned to one of two general anesthetic groups. Propofol and fentanyl were administered for induction of anesthesia, followed by either desflurane 2%-4% or sevoflurane 1%-1.5% with nitrous oxide 65% in oxygen. The desflurane (2.5 +/- 0.6 MAC. h) and sevoflurane (2.7 +/- 0.5 MAC. h) concentrations were adjusted to maintain comparable depths of hypnosis using the electroencephalogram bispectral index monitor. The Mini-Mental State (MMS) test was used to assess cognitive function preoperatively and postoperatively at 1, 3, 6, and 24-h intervals. The use of desflurane was associated with a more rapid emergence from anesthesia (6.3 +/- 2.4 min versus 8.0 +/- 2.8 min) and a shorter length of stay in the postanesthesia care unit (213 +/- 66 min versus 241 +/- 87 min). However, there were no significant differences between the Desflurane and the Sevoflurane groups when the MMS scores were compared preoperatively, and postoperatively at 1, 3, 6, and 24 h. Compared with the preoperative (baseline) MMS scores, the values were significantly decreased at 1 h postoperatively (27.8 +/- 1.7 versus 29.5 +/- 0.5 in the Desflurane group, and 27.4 +/- 1.7 versus 29.2 +/- 1.0 in the Sevoflurane group, respectively). However, the MMS scores returned to preoperative baseline levels within 6 h after surgery. At 1 h and 3 h after surgery, 51% and 11% (versus 57% and 9%) of patients in the Desflurane (versus Sevoflurane) Group experienced cognitive impairment. In conclusion, desflurane is associated with a faster early recovery than sevoflurane after general anesthesia in elderly patients. However, recovery of cognitive function was similar after desflurane and sevoflurane-based anesthesia.

IMPLICATIONS

Desflurane was associated with a faster early recovery than sevoflurane after general anesthesia in elderly patients. However, recovery of cognitive function was similar with both volatile anesthetics.

Feeling the effects of PPS. One year later

The introduction of the PPS system has brought with it many unanticipated challenges and obstacles. It demands a constant reassessment and creative modification of the present and future services, as well as the modes of delivery, without any reduction in the quality of patient care. One agency shares its experience with PPS--one year later.