Neuroimaging studies in Rett syndrome

Neuroimaging is a key instrument for determining structural and in vivo functional status of the brain, non-invasively. Multiple approaches can now determine aspects of anatomic and neurochemical changes in brain, and have been utilized effectively in Rett Syndrome patients to understand the biological basis of this neurodevelopmental disorder. Studies performed at our institute include volumetric analyses of MRI, magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), cerebral blood flow measurements with MRI, and positron emission tomography scans (PET). These studies have provided considerable insight into mechanisms underlying the clinical features of this disease. Volumetric analyses suggest that decreased brain volume in RS results from global reductions in both gray and white matter of the brain. A selective vulnerability of the frontal lobes is evidenced by the preferential reduction of blood flow, increased choline and reduced n-acetyl aspartate (NAA) by MRS, and increased glucose uptake in these same regions as shown by ((18)F)-fluorodeoxyglucose (FDG) PET scans. We hypothesize that the increased glucose uptake relates to increased glutamate cycling in synapses. The resulting neuroexcitotoxic injury to the developing brain contributes to the seizures, behavioral disturbance and respiratory irregularities commonly seen in phases 1 and 2 of this disorder.

Neurobiology of Rett syndrome: a genetic disorder of synapse development

Rett syndrome is a developmental disorder that restricts brain growth beginning in the first year of life and evidence from neuropathology and neuroimaging indicates that axonodendritic connections are especially vulnerable. In a study of amino acid neurotransmitter receptors using receptor autoradiography in tissue slices of frontal cortex and the basal ganglia, we found a biphasic age-related pattern with relatively high receptor densities in young RS girls and lower densities at later time. Using microarray analysis of gene expression in frontal cortex, we found that some of the most prominent alterations occurred in gene products related to synapses, including the NMDA receptor NR1 subunit, the cytoskeletal protein MAP-2 and synaptic vesicle proteins. Using a new antibody that recognizes MeCP2, the transcription factor mutated in RS, we established that most neurons in the rodent brain express this transcription factor. We hypothesize that a major effect of mutations in the MeCP2 protein is to cause age-related disruption of synaptic proliferation and pruning in the first decade of life.

Gene expression profiling in postmortem Rett Syndrome brain: differential gene expression and patient classification

The identification of mutations in the transcriptional repressor methyl-CpG-binding protein 2 (MECP2) gene in Rett Syndrome (RTT) suggests that an inappropriate release of transcriptional silencing may give rise to RTT neuropathology. Despite this progress, the molecular basis of RTT neuropathogenesis remains unclear. Using multiple cDNA microarray technologies, subtractive hybridization, and conventional biochemistry, we generated comprehensive gene expression profiles of postmortem brain tissue from RTT patients and matched controls. Many glial transcripts involved in known neuropathological mechanisms were found to have increased expression in RTT brain, while decreases were observed in the expression of multiple neuron-specific mRNAs. Dramatic and consistent decreases in transcripts encoding presynaptic markers indicated a specific deficit in presynaptic development. Employing multiple clustering algorithms, it was possible to accurately segregate RTT from control brain tissue samples based solely on gene expression profile. Although previously achieved in cancers, our results constitute the first report of human disease classification using gene expression profiling in a complex tissue source such as brain.

Effects of housing density on mouse physiology and behavior in the NASA Animal Enclosure Module simulators

Space flight studies using the Animal Enclosure Module (AEM) make it possible to investigate the role of microgravity on animal physiology and behavior. In this study, we compared the health and well-being of mice housed at different densities in AEM simulators (AEMS), to vivarium shoebox (control) cages (VSBC). A stress assessment battery (SAB) of measures was developed to evaluate mouse health and well-being, and to determine if any of the population sizes resulted in a stressful environment. The SAB was based, in part, on recommendations of a NASA Workshop on Rodent Cage Sizing. It includes: 1) General assessment of appearance, 2) Behavioral assessment (video), 3) Food and water consumption, 4) Body weight changes, 5) Thymus, adrenal, spleen, heart and kidney weights, 6) Plasma corticosterone concentration, 7) Total plasma protein concentration, 8) Total blood leukocyte count, 9) Differential leukocyte count: neutrophil/lymphocyte ratio; eosinophil count, 10) Gastric histology.

Clinico-pathological study of causes of perinatal mortality in a developing country

Perinatal mortality rates are an important indicator of the overall obstetric and neonatal services available, and the socio-economic status of the community. These rates are also used to identify shortcomings in services provided. The aim of this study was to identify clinical causative factors of perinatal deaths (supported by post mortem evidence where possible). This was a prospective descriptive study. The total number of deliveries and perinatal deaths over a 6-month period were recorded and clinico-demographic data noted. Post mortem examination information, if available, was also recorded. There was a total of 7789 deliveries over the 6-month period and 460 perinatal deaths, giving a perinatal mortality rate of 59/1000 deliveries; 45% (n = 207) of the perinatal deaths had post mortem examinations. The mean age was 26 years; 84.8% were single mothers. One-third of the group were un-booked: the mean gestational age of fetal death was 31 weeks, and the mean birth weight was 1700 g. Two-thirds of the perinatal deaths were stillbirths. The leading obstetric causes of deaths were: abruptio placentae (25.3%), hypertension in pregnancy (24.9%), prematurity (17.4%), unexplained stillbirth (13.4%) and intrapartum asphyxia (9.2%). The perinatal mortality rate of 59/1000 deliveries is high. Although this is comparable with other developing countries, there is a need for improvement in organisation of obstetric and neonatal care, staffing levels and access to and effective utilisation of antenatal services. These will probably lead to a significant reduction of this relatively high perinatal mortality rate.

Guidelines for reporting clinical features in cases with MECP2 mutations

An international group recommends that papers relating phenotypes to genotypes involving mutations in the X chromosome gene MECP2 should provide a minimum data set reporting the range of disturbances frequently encountered in Rett Syndrome. A simple scoring system is suggested which will facilitate comparison among the various clinical profiles. Features are described which should prompt screening for MECP2 mutations.

MeCP2 mutations in children with and without the phenotype of Rett syndrome

BACKGROUND

Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in the X-linked methyl CpG binding protein 2 (MeCP2) gene.

METHODS

One hundred sixteen patients with classical and atypical RTT were studied for mutations of the MeCP2 gene by using DHPLC and direct sequencing.

RESULTS

Causative mutations in the MeCP2 gene were identified in 63% of patients, representing a total of 30 different mutations. Mutations were identified in 72% of patients with classical RTT and one third of atypical cases studied (8 of 25). The authors found 17 novel mutations, including a complex gene rearrangement found in one individual involving two deletions and a duplication. The duplication was identical to a region within the 3' untranslated region (UTR), and represents the first report of involvement of the 3' UTR in RTT. The authors also report the identification of MeCP2 mutations in two males; a Klinefelter's male with classic RTT (T158M) and a hemizygous male infant with a Xq27-28 inversion and a novel 32 bp frameshift deletion [1154(del32)]. Studies examining the relationship between mutation type, X-inactivation status, and severity of clinical presentation found significant differences in clinical presentation between different types of mutations. Mutations in the amino-terminus were significantly correlated with a more severe clinical presentation compared with mutations closer to the carboxyl-terminus of MeCP2. Skewed X-inactivation patterns were found in two asymptomatic carriers of MeCP2 mutations and six girls diagnosed with either atypical or classical RTT.

CONCLUSION

This patient series confirms the high frequency of MeCP2gene mutations causative of RTT in females and provides data concerning the molecular basis for clinical variability (mutation type and position and X-inactivation patterns).

Alexander disease: diagnosis with MR imaging

BACKGROUND AND PURPOSE

To date, the demonstration of Rosenthal fibers on brain biopsy or autopsy specimens is considered a prerequisite for a definitive diagnosis of Alexander disease. We initiated a multiinstitutional survey of MR abnormalities in both presumed and confirmed cases of Alexander disease to assess the possibility of an MR-based diagnosis.

METHODS

MR imaging studies in three patients with an autopsy-based diagnosis of Alexander disease were analyzed to define MR criteria for the diagnosis. These criteria were then applied to 217 children with leukoencephalopathy of unknown origin.

RESULTS

Five MR imaging criteria were defined: extensive cerebral white matter changes with frontal predominance, a periventricular rim with high signal on T1-weighted images and low signal on T2-weighted images, abnormalities of basal ganglia and thalami, brain stem abnormalities, and contrast enhancement of particular gray and white matter structures. Four of the five criteria had to be met for an MR imaging-based diagnosis. In a retrospective analysis of the MR studies of the 217 patients, 19 were found who fulfilled these criteria. No other essentially new MR abnormalities were found in these patients. In four of the 19 patients, subsequent histologic confirmation was obtained. The clinical symptomatology was the same in the patients with and without histologic confirmation and correlated well with the MR abnormalities. MR abnormalities were in close agreement with the known histopathologic findings of Alexander disease.

CONCLUSION

The defined criteria are sufficient for an in vivo MR imaging diagnosis of Alexander disease; only in atypical cases is a brain biopsy still necessary for a definitive diagnosis.

Pharmacodynamics of orally administered sustained- release hydromorphone in humans

BACKGROUND

The disposition kinetics of hydromorphone generally necessitates oral administration every 4 h of the conventional immediate-release tablet to provide sustained pain relief. This trial examined time course and magnitude of analgesia to experimental pain after administration of sustained-release hydromorphone as compared with that after immediate-release hydromorphone or placebo.

METHODS

Using a 4 x 4 Latin square double-blind design, 12 subjects were randomized to receive a single dose of 8, 16, and 32 mg sustained-release hydromorphone and placebo. The same subjects had received 8 mg immediate-release hydromorphone before this study. Using an electrical experimental pain paradigm, analgesic effects were assessed for up to 30 h after administration, and venous hydromorphone plasma concentrations were measured at corresponding times.

RESULTS

The hydromorphone plasma concentration peaked significantly later (12.0 h [12.0--18.0] vs. 0.8 h [0.8--1.0]; median and interquartile range) but was maintained significantly longer at greater than 50% of peak concentration (22.7 +/- 8.2 h vs. 1.1 +/- 0.7 h; mean +/- SD) after sustained-release than after immediate-release hydromorphone. Similarly, sustained-release hydromorphone produced analgesic effects that peaked significantly later (9.0 h [9.0--12.0] vs. 1.5 h [1.0--2.0]) but were maintained significantly longer at greater than 50% of peak analgesic effect (13.3 +/- 6.3 h vs. 3.6 +/- 1.7 h). A statistically significant linear relation between the hydromorphone plasma concentration and the analgesic effect on painful stimuli existed.

CONCLUSION

A single oral dose of a new sustained-release formulation of hydromorphone provided analgesia to experimental pain beyond 24 h of its administration.

Pharmacokinetics, pharmacodynamics, and relative pharmacokinetic/pharmacodynamic profiles of zaleplon and zolpidem

OBJECTIVE

This study compared the pharmacokinetics, pharmacodynamics, and pharmacokinetic/pharmacodynamic (PK/PD) profile of zaleplon, a new pyrazolopyrimidine hypnotic, with those of zolpidem and placebo.

METHODS

This was a double-blind, 5-period crossover study in which healthy volunteers with no history of sleeping disorder were randomized to 10- or 20-mg oral doses of zaleplon, 10- or 20-mg oral doses of zolpidem, or placebo. The pharmacokinetic characteristics of the active drugs were estimated using a noncompartmental method and NONMEM. Pharmacodynamic characteristics were determined using psychophysical tests, including measures of sedation, mood, mental and motor speed, and recent and remote recall. Results of these tests were used to compare the drugs' relative PK/PD profiles.

RESULTS

Ten healthy male and female volunteers, aged 23 to 31 years, took part in the study. The apparent elimination half-life of zaleplon (60.1+/-8.9 min) was significantly shorter than that of zolpidem (124.5+/-37.9 min) (P < 0.001). Zaleplon produced less sedation than zolpidem at the 2 doses studied (P < 0.001). The sedation scores of the zaleplon groups returned to baseline in less time than those of the zolpidem groups (4 vs 8 hours; P < 0.05). Zaleplon had no effect on recent or remote recall, whereas zolpidem had a significant effect on both measures (P < 0.05).

CONCLUSIONS

In this study in 10 young, healthy volunteers, zaleplon was eliminated more rapidly, produced no memory loss, and caused less sedation than zolpidem at the same doses.

MR imaging and proton MR spectroscopy in adult Krabbe disease

We present the MR imaging findings in four patients (two pairs of siblings from two unrelated families) with adult Krabbe disease. In the first family, clinical presentation mimicked familial spastic paraplegia. Their MR images showed selective, increased signal intensity on T2-weighted sequences along the corticospinal tracts, most prominently in the proband and barely detectable in her brother. Proton MR spectroscopy showed increased choline and myo-inositol in the affected white matter. In the second family, the clinical presentation differed in that the signs of pyramidal tract involvement were asymmetrical, with concomitant asymmetry on MR images in one. In adults, Krabbe disease may present on MR imaging with selective pyramidal fiber involvement.

Auditory brainstem response findings in Rett syndrome: stability over time

OBJECTIVE

To determine whether changes consistent with the presence of white matter neurodegenerative disease would be observed in the auditory brainstem response (ABR) in Rett syndrome in conjunction with age advancement.

STUDY DESIGN

Initial and follow-up ABR findings were analyzed in a sample of 27 female patients with Rett syndrome. The interval between ABR tests ranged from 1 to 9 years.

RESULTS

No significant group differences consistent with neurodegenerative disease were observed in the wave I-III, III-V, or I-V interpeak latency intervals between the initial and follow-up test sessions.

CONCLUSIONS

Rett syndrome is not a disorder characterized by progressive white matter degeneration affecting the integrity of the brainstem central auditory pathways.

Auditory brainstem responses in Rett syndrome: effects of hyperventilation, seizures, and tympanometric variables

This study examined the effects of tympanometric variables, stage of disease, hyperventilation, and seizures on the auditory brainstem response (ABR) in Rett syndrome (RS). Thirty-four female children with RS ranging in age from 2 years, 3 months to 15 years, 7 months participated in the study. ABRs and tympanograms were recorded from all of the subjects. When the ABR peaks were identifiable, interpeak latency intervals (IPLIs) for I-III, III-V, and I-V were computed for each waveform. The peaks (I, III, and V) and IPLIs were characterized as abnormal if either the peaks were absent or the latencies were greater than 2 SD from the normative data (obtained on female children). Analyses revealed significant prolongation of wave I latencies in Rett children with abnormal tympanograms. ABR wave III latencies were significantly affected by the presence of seizures and hyperventilation. The Pearson chi-square statistic revealed significant differences in the rate of wave III and V abnormalities due to the presence and degree of hyperventilation and the presence of seizures. Wave I abnormalities were also observed in the presence of normal middle ear function, suggesting the presence of sensorineural hearing impairment in some RS children. Clinical implications of these findings are discussed.

Quantitative 1H MR spectroscopic imaging in early Rett syndrome

OBJECTIVE

To determine cerebral regional concentrations of N-acetyl aspartate (NAA), total choline (Cho), and total creatine (Cr) in Rett syndrome (RS) using 1H magnetic resonance spectroscopic imaging (MRSI).

BACKGROUND

The biochemical defect underlying RS is unknown. Because in vivo MRSI can detect important cerebral metabolites, MRSI has a potential to reveal impairment of regional cerebral metabolism in RS noninvasively.

METHODS

High-resolution, multislice 1H MRSI was carried out in 17 girls with RS. The control group consisted of nine healthy children.

RESULTS

In patients with RS, average Cho concentration was 12% higher (p < 0.005) and average NAA concentration 11% lower (p < 0.0001) compared with the control group. Regional metabolic differences included significantly lower NAA concentration in the frontal gray and white matter, insula, and hippocampus in RS; no difference in regional Cho and Cr concentrations were found. A 20 to 38% higher Cho:NAA ratio in frontal and parietal gray and white matter, insular gray matter, and hippocampus (p < 0.05) and a 14 to 47% lower NAA:Cr ratio in frontal cortical gray matter, parietal and temporal white matter, insula, and putamen (p < 0.05) were found in subjects with RS compared with controls. Patients with seizures had higher average concentrations of Cho, Cr, and NAA compared with those without seizures (8-19%, p < 0.05).

CONCLUSION

Metabolic impairment in RS involves both gray and white matter and particularly involves frontal and parietal lobes and the insular cortex. Loss of NAA most likely reflects reduced neuronal and dendritic tree size; increased Cho concentration may result from gliosis.

Tibial and peroneal artery bypasses using polytetrafluoroethylene (PTFE) with an interposition vein cuff

The combined results of femoro-distal bypasses using prosthetic material with vein cuffs from two separate vascular units is presented.

METHOD

Over the last five years, 89 infrainguinal bypasses using polytetrafluoroethylene (PTFE) with a distal interposition vein cuff to a tibial artery have been performed in two centres. All operations were for critical limb ischaemia. The mean age was 72 years (47-90), there were 46 males and 43 females, 27 of whom were diabetic. Twenty-eight patients had a history of angina and/or previous myocardial infarct. The median follow-up was 12 months (0-68 months).

RESULTS

During the follow-up period there were 28 deaths, 35 major limb amputations and 44 graft failures. The graft patency rates at 12 and 24 months were 50 and 32%, and limb salvage rates were 53 and 44%, respectively. The patient survival rates were 66 and 61%, respectively.

CONCLUSION

The authors believe that the likely improvement in pain free quality of life the patient may enjoy with a successful bypass shifts the balance in some individuals towards bypass surgery using PTFE with a vein cuff to a tibial artery when such an option is possible.

Autosomal dominant diffuse leukoencephalopathy with neuroaxonal spheroids

OBJECTIVE

To provide clinical, MRI, and histopathologic findings in a rare white matter disorder with autosomal dominant inheritance, so-called hereditary diffuse leukoencephalopathy with spheroids (HDLS).

BACKGROUND

Progressive leukoencephalopathies often constitute a diagnostic dilemma in both children and adults. In some cases, histopathologic examination of brain tissue is required for a classifying diagnosis.

METHODS

Clinical history, MRI, and autopsy findings were reviewed in three patients with HDLS: a father, his daughter, and an unrelated patient.

RESULTS

Clinical history consisted of an adult-onset neurologic deterioration with signs of frontal lobe dysfunction, epilepsy, spasticity, ataxia, and mild extrapyramidal disturbances. MRI findings included cerebral atrophy and patchy white matter changes, most pronounced in the frontal and frontoparietal area with extension through the posterior limb of the internal capsule into the pyramidal tracts of the brainstem. Autopsy in two patients revealed a leukoencephalopathy with frontoparietal and frontal preponderance and numerous neuroaxonal spheroids in the abnormal white matter. The pyramidal tracts were affected throughout the brainstem.

CONCLUSION

Similar clinical and histopathologic findings have been reported in members of a Swedish pedigree. The homogeneity of the findings strongly suggests that HDLS is a distinct disease entity. In the absence of a biochemical or genetic marker, a definitive diagnosis requires histopathologic confirmation in one of the affected family members. Neuroaxonal spheroids.

Defining and categorizing leukoencephalopathies of unknown origin: MR imaging approach

PURPOSE

To categorize leukoencephalopathies of unknown origin into a few major groups by using magnetic resonance (MR) imaging criteria to facilitate further studies, and to assess the possibility of defining "new" (i.e., until now unknown) disease entities within these major groups.

MATERIALS AND METHODS

MR images of 92 patients (55 male, 37 female; mean age, 9.3 years) with a leukoencephalopathy were examined by using a scoring list of 68 items. Seven major categories were defined according to the predominant location of the white matter abnormalities. Statistical analysis was used to assess the validity of these seven categories.

RESULTS

Statistical analysis results showed that the seven categories could be well distinguished by either using the defining variables initially accepted as inclusion criteria or selecting a few other variables found to have discriminating value. The additional variables confirmed that the categories are essentially distinct and vary systematically with regard to items other than the inclusion criteria. The existence of two recently defined leukoencephalopathies was confirmed, but no consistent evidence of other new disease entities could be provided.

CONCLUSION

Establishing these seven categories helps in the interpretation of individual studies by demonstrating features that the patient has in common with other patients, and it may facilitate further research on homogeneous subgroups of patients and allow pooling of data across multiple centers.

The gene for leukoencephalopathy with vanishing white matter is located on chromosome 3q27

Leukoencephalopathy with vanishing white matter (VWM) is an autosomal recessive disorder with normal early development and, usually, childhood-onset neurological deterioration. At present, diagnosis of VWM is based on clinical examination and the results of repeat magnetic resonance imaging and magnetic resonance spectroscopy, which show that, with time, increasing amounts of the cerebral white matter vanish and are replaced by cerebrospinal fluid. We have performed a genome linkage screening of a panel of 19 families of different ethnic origins. Significant linkage to chromosome 3q27 was observed in a 7-cM interval between markers D3S3730 and D3S3592, with a maximum multipoint LOD score of 5.1 calculated from the entire data set. The results of genealogical studies have suggested that seven parents in four Dutch families with VWM may have inherited an allele for the disease from a common ancestor who lived at least eight generations ago. Analysis of these families provided further evidence for the localization of the gene for VWM to 3q27. The patients shared a haplotype spanning 5 cM between markers D3S1618 and D3S3592. In one family of a different ethnic background, the patient had, in the same region, homozygosity for 13 consecutive markers spanning at least 12 cM, suggesting consanguinity between the parents. A healthy sibling of this patient had the same homozygous haplotype, which suggests that the healthy sibling is presymptomatic for the disease.

Automated Talairach atlas-based parcellation and measurement of cerebral lobes in children

This study applied a Talairach-based automated parcellation method, originally proposed for adults, to the measurement of lobar brain regions in pediatric study groups. Manual measures of lobar brain regions in a sample of 15 healthy boys, girls and adults were used initially to revise the original Talairach-based grid to increase its applicability to pediatric brains. The applicability of the revised Talairach grid was then tested on an independent sample of five girls with Rett syndrome. As Tables 3 and 4 in the text demonstrate, sensitivity, specificity and positive predictive values either remained unchanged or increased as a result of revising the sectors to fit the brains of children. High levels of sensitivity and specificity were achieved for all revised Talairach-based calculations in relation to the manual measures. Both positive predictive values and intraclass correlations between volumetric measures produced by the revised automated and manual methods varied with the relative size of the brain region. Values were relatively low for smaller structures such as the brainstem and subcortical region, and high for lobar regions. These results suggest that the automated Talairach atlas-based parcellation method can produce sensitive and specific volumetric measures of lobar brain regions in both normal children and children with brain disorders. Accordingly, the method holds much promise for facilitating quantitative pediatric neuroimaging research.

Vascular surgical society of great britain and ireland: influence of contralateral stenosis on long-term mortality rate following carotid surgery

BACKGROUND: Recent evidence suggests that high-grade contralateral stenosis has an adverse effect on perioperative morbidity in carotid endarterectomy (CEA). The relationship between contralateral high-grade stenosis and long-term survival after CEA was examined. METHODS: Three hundred and twenty-seven patients undergoing 333 CEA operations were entered prospectively into a database and long-term follow-up was instituted. Cardiac and stroke risk factors were identified before operation and correlated with long-term survival and cause of death. RESULTS: Mean age at operation was 68 (range 42-86) years. Median follow-up was 2 (range 1-8) years. There were 45 deaths (seven perioperative), 17 myocardial, 16 from stroke (four perioperative), five from neoplasia, three respiratory and four others. The cumulative 5-year survival rate was 75 per cent. Patients with high-grade contralateral stenosis (greater than 80 per cent) had a significantly reduced life expectancy after CEA (P < 0. 05). CONCLUSION: Severe contralateral carotid disease is not only an adverse perioperative risk factor but also has negative implications for survival of the patient in the longer term. Following CEA, patients in general have a lower life expectancy than a normal age-matched population.

Altered development of glutamate and GABA receptors in the basal ganglia of girls with Rett syndrome

Rett syndrome (RS), a genetic disorder found almost exclusively in females, is associated with psychomotor regression and stereotyped hand movements. To determine whether a defect in basal ganglia amino acid neurotransmission plays a role in RS, NMDA-, AMPA-, kainate (KA)-, and metabotropic (mGluR)-type glutamate receptors (GluRs) and GABA receptors were labeled autoradiographically in the caudate, putamen, and globus pallidus of postmortem brain slices from 9 RS girls and 10 age-related controls. The cases were divided into younger (8 years or younger) and older age groups to study age-related changes in receptor binding density. We found significant reductions in AMPA and NMDA receptor density in the putamen and in KA receptor density in the caudate of older RS cases compared to controls. In contrast, mGluR density in the basal ganglia of RS patients was not altered significantly. The density of GluRs in control subjects generally showed more limited changes with age than in RS cases. In contrast to ionotropic GluRs, GABA receptor density was significantly increased in the caudate of young RS patients. The effects on GluR density in the putamen, which serves a primary motor function, were consistent with the motor deficits observed in RS, while those on amino acid transmitter receptors in the caudate may account for some cognitive features. Our studies demonstrate regional, receptor-subtype, and age-specific alterations in amino acid neurotransmitter receptors in the basal ganglia of RS girls. These changes may correlate with age-related clinical stages observed in RS.

Development of amino acid receptors in frontal cortex from girls with Rett syndrome

To determine whether a disorder of excitatory neurotransmission plays a role in the pathophysiology of Rett syndrome (RS), N-methyl-D-aspartate (NMDA), adenosine monophosphate acid (AMPA), kainate, and metabotropic types of glutamate receptors were labeled autoradiographically in the superior frontal gyrus (SFG) from 9 RS patients and 10 female controls. The results showed a trend for the densities of NMDA, AMPA, gamma-aminobutyric acid, and metabotropic glutamate receptors to be higher in younger patients than in controls and for densities in older patients to fall below those of controls. The age-related changes in SFG NMDA receptor density may be correlated with the shift from psychomotor regression and seizures in younger stage II/III RS girls to the less epileptic plateau stage in older girls.

Different mutations in the same codon of the proteolipid protein gene, PLP, may help in correlating genotype with phenotype in Pelizaeus-Merzbacher disease/X-linked spastic paraplegia (PMD/SPG2)

Pelizaeus-Merzbacher disease/X-linked spastic paraplegia (PMD/SPG2) comprises a spectrum of diseases that range from severe to quite mild. The reasons for the variation in severity are not obvious, but suggested explanations include the extent of disruption of the transmembrane portion of the proteolipid protein caused by certain amino acid substitutions and interference with the trafficking of the PLP molecule in oligodendrocytes. Four codons in which substitution of more than one amino acid has occurred are available for examination of clinical and potential structural manifestations: Valine165 to either glutamate or glycine, leucine 045 to either proline or arginine, aspartate 202 to asparagine or histidine, and leucine 223 to isoleucine or proline. Three of these mutations, Val165Gly, Leu045Pro, and Leu223Ile have not been described previously in humans. The altered amino acids appear in the A-B loop, C helix, and C-D loop, respectively. We describe clinically patients with the mutations T494G (Val165Gly), T134C (Leu045Pro), and C667A (Leu223Ile). We discuss also the previously reported mutations Asp202Asn and Asp202His. We have calculated the changes in hydrophobicity of short sequences surrounding some of these amino acids and compared the probable results of the changes in transmembrane structure of the proteolipid protein for the various mutations with the clinical data available on the patients. While the Val165Glu mutation, which is expected to produce disruption of a transmembrane loop of the protein, produces more severe disease than does Val165Gly, no particular correlation with hydrophobicity is found for the other mutations. As these are not in transmembrane domains, other factors such as intracellular transport or interaction between protein chains during myelin formation are probably at work.

Plasma very long chain fatty acids in 3,000 peroxisome disease patients and 29,000 controls

The assay of plasma very long chain fatty acids (VLCFAs), developed in our laboratory in 1981, has become the most widely used procedure for the diagnosis of X-linked adrenoleukodystrophy (X-ALD) and other peroxisomal disorders. We present here our 17 years' experience with this assay. Three VLCFA parameters, the level of hexacosanoic acid (C26:0), the ratio of C26:0 to tetracosanoic acid (C24:0), and of C26:0 to docosanoic acid (C22:0), were measured in 1,097 males (hemizygotes) with X-ALD, 1,282 women heterozygous for this disorder, including 379 obligate heterozygotes, 797 patients with other peroxisomal disorders, and 29,600 control subjects. All X-ALD hemizygotes who had not previously received Lorenzo's oil or a diet with a high erucic acid content had increased VLCFA levels, but the application of a discriminant function based on all three measurements is required to avoid the serious consequences of a false-negative result. VLCFA levels are increased at day of birth, thus providing the potential for neonatal mass screening, are identical in the childhood and adult forms, and do not change with age. Eighty-five percent of obligate heterozygotes had abnormally high VLCFA levels, but a normal result does not exclude carrier status. VLCFA levels were increased in all patients homozygous for Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum's disease, and in patients with deficiencies of peroxisomal acyl-coenzyme A oxidase, bifunctional enzyme, and 3-oxoacyl-coenzyme A thiolase. In these patients the degree of VLCFA excess correlated with clinical severity.

Mutation analysis of the M6b gene in patients with Rett syndrome

Human Xp22.2 has been proposed as a candidate region for the Rett syndrome (RTT) gene. M6b, a member of the proteolipid protein gene family, was mapped to Xp22.2 within one of the RTT candidate regions. In this article we describe the structure of the M6b gene, refine the physical mapping of M6b between markers DXS69E and DXS414, and present the results of mutation analysis of the M6b gene in patients with RTT. The data from mutation analysis on 55 RTT patients make it very unlikely that M6b is involved in RTT.

Rett syndrome: natural history and underlying disease mechanisms

Rett syndrome (RS) is a neurological disorder that mainly, and possibly exclusively, affects girls. Diagnosis continues to be based upon a consistent constellation of clinical features observed in all of the patients worldwide. A biological marker has not been identified. In spite of this serious limitation, it is generally agreed that RS is a distinct entity and that it is genetically determined. Although it is associated with loss of function between infancy and the fifth year of life, its course becomes relatively static thereafter, setting it apart from most of the genetic neurodegenerative disorders of childhood. Neuropathological and neurochemical studies call attention to RS as a neurodevelopmental disorder of infancy resulting in failed brain growth. Clarification of its pathogenesis may provide new insight into normal brain development.

Abnormalities in neuronal maturation in Rett syndrome neocortex: preliminary molecular correlates

In correspondence with the severe cognitive impairment and autistic features of Rett syndrome (RS), multiple anomalies of the cerebral cortex that include generalized reductions in dendritic arborizations and in cholinergic markers have been found. Considering the potential role of neurotransmitters in cortical differentiation, we have studied the relationship between cholinergic deficit and dendritic protein expression in RS and in a relevant animal model. Dendritic development is characterized by the sequential expression of cytoskeletal proteins whose levels remain relatively stable in adult life. Using quantitative immunoblotting, we have determined that in RS there is a reduction in proteins linked to early dendritic development [microtubule-associated protein (MAP)-5, MAP-2]. By contrast, in Down syndrome there is relative generalized increase in dendritic proteins. Mice with basal forebrain lesions at birth, which transiently decrease cholinergic innervation to the cortex, showed in adulthood reductions in MAP-2 that resemble those seen in RS. We conclude that dendritic anomalies in RS represent disturbances in early cortical differentiation and that cholinergic deficit may play a critical role in their pathogenesis as suggested by the animal data.

A male child with the rumpshaker mutation, X-linked spastic paraplegia/Pelizaeus-Merzbacher disease and lysinuria

A 3.5-year-old boy had intact cognition, delayed walking, progressive spastic paraparesis and congenital nystagmus. The mother denied family history of any neurological disorders, so an extensive work-up was begun. Lysinuria, increased signal on cerebral T2-weighted MRI imaging and the rumpshaker mutation (Ile186Thr) in his proteolipid protein gene. PLP, were found. When faced with these facts, the mother admitted that she was related to the family reported by Johnston and McKusick in 1962 and Kobayashi in 1994, in whom this mutation has been reported. This is the first report of an abnormal MRI scan in this family.

Mesenteric revascularisation for acute-on-chronic intestinal ischaemia

Eleven patients (eight women) underwent urgent revascularisation for acute-on-chronic mesenteric ischaemia. Four patients had dual vessel and seven single vessel reconstructions. Two patients underwent simultaneous bowel resection and one patient has had three separate grafts to the superior mesenteric artery. There were two peri-operative deaths and three have died in the late follow-up period after 18, 24 and 36 months. The remainder have survived for between five and 63 months. Revascularisation for acute-on-chronic mesenteric ischaemia has been shown to be technically possible and of substantial benefit to patients who would otherwise be treated as terminal cases.

Glutaraldehyde-tanned bovine carotid artery graft for infrainguinal vascular reconstruction: 5-year follow-up

OBJECTIVE

To assess the long-term patency of a modified biological conduit, the glutaraldehyde-tanned bovine carotid artery, in above-knee infrainguinal arterial reconstruction.

PATIENTS AND METHODS

Prospective follow-up of a cohort of 58 above-knee femoropopliteal grafts in 55 patients. Graft patency was assessed at yearly intervals with doppler ankle pressure measurements.

RESULTS

The median follow-up period has been 67 months. Nine grafts occluded within 30 days of surgery and a further 19 graft closures have been observed in the follow-up period. The overall cumulative primary graft patency at 1, 3 and 5 years was 70%, 61% and 56%, respectively. If the 30-day graft failures are excluded, the primary graft patency rises to 83%, 74% and 68% at 1, 3 and 5 years, respectively. Six limbs have been amputated, four above the knee and two below the knee. There were no graft aneurysms and no graft infections.

CONCLUSION

Results indicate that the modified bovine carotid artery graft with an above-knee anastomosis does not seem to be inferior to PTFE, but is inferior to reversed vein. Modified biological conduits offer a reasonable alternative to synthetic grafts for infrainguinal arterial reconstruction and appear to maintain acceptable long-term mechanical stability.

The radiological appearance of atherosclerotic popliteal artery aneurysms: the "dog-leg" sign

The radiological appearance of popliteal aneurysms is described. Althought the lumen of the artery is often of normal diameter there is elongation of the vessel which frequently results in an acute "dog-leg". This sign has not been previously described.

Assessment of adrenal function in women heterozygous for adrenoleukodystrophy

Adrenoleukodystrophy (ALD) is an X-linked recessive disorder that destroys the white matter of the brain and is associated with adrenal insufficiency. The prevalence of adrenal dysfunction in 71 women carriers of the X-linked ALD gene was studied. These subjects were identified initially on the basis of being obligate carriers of the X-linked trait by pedigree analysis and were confirmed by plasma very long chain fatty acid levels consistent with a heterozygote status. One subject had well documented overt adrenal insufficiency, diagnosed and treated since age 9 yr. Among the remaining women, the mean serum 0800 h and 1 h post-ACTH cortisol concentrations [16 +/- 7 (+/-SD) and 34 +/- 8 micrograms/dL, respectively] were normal. All subjects had normal ACTH-stimulated serum cortisol levels, i.e. more than 20 micrograms/dL. However, 4 subjects (6%) had subnormal ACTH-stimulated aldosterone concentrations (mean, 9 +/- 6 vs. 42 +/- 16 ng/dL for other subjects; P = 0.001, by Mann Whitney rank sum test). Three of these women (75%) were taking nonsteroidal antiinflammatory agents (NSAIDs), whereas only 4 of 67 (6%) subjects with normal aldosterone responsiveness were NSAIDs users (P < 0.01, by Fisher's exact test). Thus, NSAIDs use was associated with increased risk of hypoaldosteronism (odds ratio, 50.2; 95% confidence interval, 3.3-266; P < 0.002). Three of these four women had symptoms consistent with mineralocorticoid deficiency. Serum sodium and potassium concentrations were normal in all subjects. Basal and metyrapone-stimulated plasma ACTH concentrations were also normal in adequately tested subjects with and without mineralocorticoid insufficiency. Five of eight subjects (63%) who underwent testing with synthetic ovine CRH (oCRH) had abnormalities. Three did not meet the criteria for adequate cortisol stimulation (i.e. > 20 micrograms/dL) and had peak ACTH levels greater than 30 pg/mL. Two other subjects had exaggerated ACTH responses with normal cortisol levels. There were no significant differences in the mean or median levels of very long chain fatty acid, C26:0, C24/22 ratios, or C26/22 ratios among the entire subject group, the subgroup with blunted aldosterone responses to ACTH, and the subgroup with blunted responses to oCRH (P > 0.05, by ANOVA and Kruskall-Wallis test for C26, C24/22 ratio, and C26/22 ratio). We conclude that 1) adrenal cortical insufficiency rarely develops in ALD heterozygotes; 2) isolated mineralocorticoid insufficiency can occur in ALD heterozygotes, as has been previously reported to occur with autoimmune and acquired immunodeficiency syndrome-related adrenal dysfunction; 3) ALD heterozygosity may predispose these individuals to NSAID-related hypoaldosteronism; and 4) a subclinical decrease in glucocorticoid reserve, as measured by oCRH testing, may be present in a majority of these women. Aldosterone levels should be included in the ACTH stimulation testing when seeking evidence of adrenal insufficiency in affected women. NSAIDs should be considered a risk factor for the development of hypoaldosteronism in women heterozygous for ALD.

Neuroanatomy in Rett syndrome: cerebral cortex and posterior fossa

Rett syndrome (RS), a neurodevelopmental disorder of unknown etiology occurring almost exclusively in females, is characterized by autistic-like behavior, motor dysfunction, loss of language skills, dementia, and microcephaly. This study is a follow-up and extension of a previously reported neuroimaging study of patients with RS. We replicated previously reported findings with a larger patient population, and the volumetric MRI analysis was extended to include an analysis of neuroanatomy of the posterior fossa. Twenty girls with RS were compared with individually age- and gender-matched normal controls. Patients with RS showed global reduction in gray- and white-matter volumes. The prefrontal, posterior-frontal, and anterior-temporal regions showed the largest bilateral decrease in gray-matter volume, whereas white-matter volume was uniformly reduced throughout the brain. We found confirmation for the preferential reduction in caudate nucleus volume. However, we observed no preferential reduction in midbrain volume despite a preferential reduction in the midsagittal area of this region. We also present an individual case comparison between monozygotic twins discordant for RS.

The efficacy of phenytoin in eclampsia

Although the Eclampsia Trial Collaborative Group reported that magnesium sulphate was more effective in preventing recurrent convulsions in eclampsia than phenytoin, confirmatory evidence that phenytoin is not useful as a prophylactic anticonvulsant agent in eclampsia is necessary. This prospective descriptive study enrolled 68 women with eclampsia. Recurrence of seizures occurred in 18 (26.5%) patients following phenytoin therapy. In 16 patients, the seizure recurrence occurred between the loading dose and first maintenance dose at 6 hours. There was no statistical difference in the clinical characteristics of those who had seizure recurrence compared with those that did not. Seizure recurrence following phenytoin therapy in eclampsia is unacceptably high. These results suggest that phenytoin is not effective as a prophylactic anticonvulsant in eclampsia. No conclusions about its effectiveness compared with alternative prophylactic anticonvulsants can be made from this descriptive study.

Nurses' perceptions of urinary catheter selection and management

Nurses are often responsible for the initiation of catherization procedures for patients within the hospital or community setting. This nursing role requires contemporary information on catheter selection and problem solving in the maintenance of urinary catheters. A descriptive survey with a questionnaire sent to registered and enrolled nurses (N = 709) within an Australian metropolitan area health service was undertaken to determine their current knowledge level in relation to catheter care practices. Registered nurses represented 91% of the sample, with 66% of the entire sample having 7 or more years of nursing experience. Only 14% of nurses believed that their knowledge levels were adequate, with very few receiving postregistration education. Only 31% of the respondents recommended the use of purely silicone catheters, these being the least cytotoxic to the urethra for longterm use. Less than half of the respondents were unaware of the availability of female-length catheters. There was a general lack of knowledge of current catheter costs that would have major implications for unit budgets. The apparent gaps in nursing knowledge of catheter care suggest the need for urgent educational programs on catheter care practices for nurses within this service and the initiation of an area-wide standardized policy in catheter selection and management.

Cognitive and brain magnetic resonance imaging findings in adrenomyeloneuropathy

Neuropsychological functioning and brain magnetic resonance imaging (MRI) were evaluated in 84 men with adrenomyeloneuropathy (AMN). MRI was normal in 61%, the "pure AMN" group, while 39%, the "cerebral AMN" group, showed brain white matter abnormalities. Except for mild deficits in psychomotor speed and visual memory, neuropsychological function was normal in pure AMN. Most patients with cerebral AMN had normal IQ and language but evidenced impaired psychomotor speed, spatial cognition, memory, and executive functions. Patients with MRI evidence of very severe cerebral disease had global and language impairment as well, and deficits in all patients were highly correlated with degree of brain MRI involvement.

Dopamine transporters are markedly reduced in Lesch-Nyhan disease in vivo

Dopamine (DA) deficiency has been implicated in Lesch-Nyhan disease (LND), a genetic disorder that is characterized by hyperuricemia, choreoathetosis, dystonia, and compulsive self-injury. To establish that DA deficiency is present in LND, the ligand WIN-35,428, which binds to DA transporters, was used to estimate the density of DA-containing neurons in the caudate and putamen of six patients with classic LND. Comparisons were made with 10 control subjects and 3 patients with Rett syndrome. Three methods were used to quantify the binding of the DA transporter so that its density could be estimated by a single dynamic positron emission tomography study. These approaches included the caudate- or putamen-to-cerebellum ratio of ligand at 80-90 min postinjection, kinetic analysis of the binding potential [Bmax/(Kd x Vd)] using the assumption of equal partition coefficients in the striatum and the cerebellum, and graphical analysis of the binding potential. Depending on the method of analysis, a 50-63% reduction of the binding to DA transporters in the caudate, and a 64-75% reduction in the putamen of the LND patients was observed compared to the normal control group. When LND patients were compared to Rett syndrome patients, similar reductions were found in the caudate (53-61%) and putamen (67-72%) in LND patients. Transporter binding in Rett syndrome patients was not significantly different from the normal controls. Finally, volumetric magnetic resonance imaging studies detected a 30% reduction in the caudate volume of LND patients. To ensure that a reduction in the caudate volume would not confound the results, a rigorous partial volume correction of the caudate time activity curve was performed. This correction resulted in an even greater decrease in the caudate-cerebellar ratio in LND patients when contrasted to controls. To our knowledge, these findings provide the first in vivo documentation of a dopaminergic reduction in LND and illustrate the role of positron emission tomography imaging in investigating neurodevelopmental disorders.

Neuronal migration abnormality in peroxisomal bifunctional enzyme defect

Patterns of brain dysgenesis that resemble those in the Zellweger syndrome were demonstrated in a boy with an isolated defect of the peroxisomal bifunctional enzyme. There was bilateral centrosylvian pachygyria and polymicrogyria, diffuse hemispheric hypomyelination with heterotopic neurons, Purkinje cell heterotopias, and simplified convolutions of the dentate nucleus and inferior olive. This association of Zellweger syndrome-like brain dysgenesis with a defect of a single peroxisomal enzyme provides new opportunities for the study of pathogenetic mechanisms in peroxisomal disorders.

Randomised study assessing the effect of phenytoin and magnesium sulphate on maternal cerebral circulation in eclampsia using transcranial Doppler ultrasound

OBJECTIVE

To assess maternal middle cerebral artery flow velocity patterns as measured by transcranial Doppler ultrasound (TCD) in eclampsia and to investigate the effect of the anticonvulsants magnesium sulphate (MgSO4) and phenytoin on cerebral circulation.

DESIGN

Prospective randomised study.

SETTING

High care obstetric unit, King Edward VIII Hospital, Durban, South Africa.

PARTICIPANTS

Twenty-four eclamptic patients: 13 received MgSO4 and 11 phenytoin.

INTERVENTION

Middle cerebral artery flow velocity waveforms were measured using 2 MHz pulsed Doppler ultrasound via the transtemporal approach in eclamptic patients, before and 15 minutes after the loading dose of anticonvulsant.

RESULTS

Magnesium sulphate significantly reduced the pulsatility index (P = 0.002) and mean flow velocity (P = 0.02) in the middle cerebral artery, whereas phenytoin failed to produce any statistically significant effect. However, differences between groups were not statistically significant. Systolic and diastolic blood pressures were reduced in both the MgSO4 and phenytoin groups.

CONCLUSION

These findings provide firm evidence that MgSO4 relieves cerebral vasospasm, compared with phenytoin, and may therefore be the better drug for the prevention of eclamptic convulsion.

Phenotype of patients with peroxisomal disorders subdivided into sixteen complementation groups

OBJECTIVE

To use the technique of complementation analysis to help define genotype and classify patients with clinical manifestations consistent with those of the disorders of peroxisome assembly, namely the Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), infantile Refsum disease (IRD), and rhizomelic chondrodysplasia punctata (RCDP).

STUDY DESIGN

Clinical findings, peroxisomal function, and complementation groups were examined in 173 patients with the clinical manifestations of these disorders.

RESULTS

In 37 patients (21%), peroxisome assembly was intact and isolated deficiencies of one of five peroxisomal enzymes involved in the beta-oxidation of fatty acids or plasmalogen biosynthesis were demonstrated. Ten complementation groups were identified among 93 patients (54%) with impaired peroxisome assembly and one of three phenotypes (ZS, NALD, or IRD) without correlation between complementation group and phenotype. Forty-three patients (25%) had impaired peroxisome assembly associated with the RCDP phenotype and belonged to a single complementation group. Of the 173 patients, 10 had unusually mild clinical manifestations, including survival to the fifth decade or deficits limited to congenital cataracts.

CONCLUSIONS

At least 16 complementation groups, and hence genotypes, are associated with clinical manifestations of disorders of peroxisome assembly. The range of phenotype is wide, and some patients have mild involvement.

Diagnoses of neuronal ceroid-lipofuscinosis by immunochemical methods

The neuronal ceroid-lipofuscinoses (NCL), also known as Batten disease, are a not uncommon group of disorders affecting infants, children, and young adults. The abnormal ultrastructural profiles seen in NCL are used for standard diagnosis; however, they can be missed, and are also found in other neurodegenerative conditions. Furthermore, there is an overlap between the types of inclusion profiles among the different forms of NCL. Therefore, a more specific and biochemically-based marker is necessary to confirm the diagnosis of NCL. Antibodies raised against the storage material from the ovine form of NCL (mitochondrial ATP synthase subunit c) were utilized to determine whether NCL could be distinguished from other metabolic-neurodegenerative disorders. By immunoblotting and immunohistochemistry, several brain samples of well-evaluated NCL cases confirmed increased accumulations in all NCL cases except in the brain of an infantile-onset NCL patient. The immunoblot studies of skin fibroblasts and brain were sensitive but not highly specific to NCL, due to the recognition of this material in normal controls as well as in other neurogenetic diseases. Immunocytochemistry of skin fibroblasts clearly distinguished LINCL and JNCL cases from controls, and with further refinement has the potential for becoming a diagnostic tool.

Rett syndrome studies of natural history and search for a genetic marker

The commonly held notion that Rett syndrome (RS) is a neurodegenerative disorder with normal early development was examined by an epidemiological survey and review of medical records and serial neurological and development evaluations. In some subjects, deviance from normal development was evident from the perinatal period, and gradually became more prominent with age. These findings are convincing when seen in conjunction with a reduction in velocity of brain growth, as early as 2-4 months of life, well before the recognition of gross neurological deficits. Neurodevelopmental evaluations provide no indication that there is progressive loss of adaptive behaviors, or communication skills to indicate a neurodegenerative process. Taken together with the known neuropathological and neurochemical changes in RS brain we hypothesize that RS is a neurodevelopmental disorder, which has a genetic basis, and affects subsets of neurons and their connections during a period of vigorous brain growth, when synapse formation and pruning are at a peak. Studies of mitochondrial (mt) DNA in brain to understand the genetic mechanisms underlying matrilineal inheritance in the few familial cases, and mt structural and enzyme deficiencies have been unrevealing to date.

Abnormal expression of microtubule-associated protein 2 (MAP-2) in neocortex in Rett syndrome

Immunocytochemical evaluations of the neocortex of three classical Rett syndrome (RS) individuals revealed a selective abnormality in the expression of microtubule-associated protein 2 (MAP-2). MAP-2 immunoreactivity (ir) was reduced throughout the neocortex of all three RS cases with a reversal of the normal pattern of more intense staining in deep cortical layers. This anomaly was selective for MAP-2 because nonphosphorylated neurofilament (SMI-32) labeling of deep pyramidal neurons and calbindin (CaBP)-stained GABAergic cells remained unchanged. Moreover, MAP-2 ir was virtually undetected in white matter while GABAergic and, particularly, peptidergic (neuropeptide Y: NPY) profiles were easily recognized. These results demonstrate a marked disruption of a major cytoskeletal component in neocortex in RS which seems to affect, predominantly, pyramidal projection and white matter neurons. MAP-2 expression appears early in neuronal maturation of the neocortex, particularly in the subplate region, the future superficial white matter, suggesting that these reported abnormalities in RS represent a developmental disturbance. Considering that MAP-2 expression is regulated by several neurotransmitter systems in adult cerebral cortex, particularly dopaminergic and cholinergic afferents that are deficient in RS, these neurochemical alterations could be related to this anomalous MAP-2 expression.