Social impairments in Rett syndrome: characteristics and relationship with clinical severity

BACKGROUND

While behavioural abnormalities are fundamental features of Rett syndrome (RTT), few studies have examined the RTT behavioural phenotype. Most of these reports have focused on autistic features, linked to the early regressive phase of the disorder, and few studies have applied standardised behavioural measures. We used a battery of standardised measures of behaviour and functioning to test the following hypotheses: (1) autistic behaviour is prominent throughout childhood in RTT; (2) autistic features are more salient in individuals with milder presentation; (3) severity of autistic behaviour is associated with a wider range of behavioural problems; and (4) specific MECP2 mutations are linked to more severe autistic behaviour.

METHODS

Eighty MECP2 mutation-positive girls with RTT (aged 1.6-14.9 years) were administered: (1) the Screen for Social Interaction (SSI), a measure of autistic behaviour suited for individuals with severe communication and motor impairment; (2) the Rett Syndrome Behaviour Questionnaire (RSBQ), covering a wide range of abnormal behaviours in RTT; (3) the Vineland Adaptive Behavior Scales (VABS); and (4) a modified version of the Rett Syndrome Severity Scale (RSSS). Regression analyses examined the predictive value of age and RSSS on autistic behaviour and other behavioural abnormalities. T-tests further characterised the behavioural phenotype of individual MECP2 mutations.

RESULTS

While age had no significant effect on SSI or RSBQ total scores in RTT, VABS Socialization and Composite scores decreased over time. Clinical severity (i.e. RSSS) also increased with age. Surprisingly, SSI performance was not related to either RSSS or VABS Composite scores. Autistic behaviour was weakly linked with the RSBQ Hand behaviour factor scores, but not with the RSBQ Fear/Anxiety factor. Clinical (neurological) severity did not predict RSBQ scores, as evidenced by the analysis of individual MECP2 mutations (e.g. p.R106W, p.R270X and p.R294X).

CONCLUSIONS

Our data suggest that in RTT, autistic behaviour persists after the period of regression. It also demonstrated that neurological and behavioural impairments, including autistic features, are relatively independent of one another. Consistent with previous reports of the RTT phenotype, individual MECP2 mutations demonstrate complex associations with autistic features. Evidence of persistent autistic behaviour throughout childhood, and of a link between hand function and social skills, has important implications not only for research on the RTT behavioural phenotype, but also for the clinical management of the disorder.

White matter impairment in Rett syndrome: diffusion tensor imaging study with clinical correlations

BACKGROUND AND PURPOSE

RTT, caused by mutations in the methyl CPG binding protein 2 (MeCP2) gene, is a disorder of neuronal maturation and connections. Our aim was to prospectively examine FA by DTI and correlate this with certain clinical features in patients with RTT.

MATERIALS AND METHODS

Thirty-two patients with RTT underwent neurologic assessments and DTI. Thirty-seven age-matched healthy female control subjects were studied for comparison. With use of a 1.5T MR imaging unit, DTI data were acquired, and FA was evaluated to investigate multiple regional tract-specific abnormalities in patients with RTT.

RESULTS

In RTT, significant reductions in FA were noted in the genu and splenium of the corpus callosum and external capsule, with regions of significant reductions in the cingulate, internal capsule, posterior thalamic radiation, and frontal white matter. In contrast, FA of visual pathways was similar to control subjects. FA in the superior longitudinal fasciculus, which is associated with speech, was equal to control subjects in patients with preserved speech (phrases and sentences) (P = .542), whereas FA was reduced in those patients who were nonverbal or speaking only single words (P < .001). No correlations between FA values for tracts and clinical features such as seizures, gross or fine motor skills, and head circumference were identified.

CONCLUSIONS

DTI, a noninvasive technique to assess white matter tract pathologic features, may add specificity to the assessment of RTT clinical severity that is presently based on the classification of MeCP2 gene mutation and X-inactivation.

Two cases with progressive cystic leukoencephalopathy

Leukoencephalopathies with cystic changes in the white matter on magnetic resonance imaging are aetiologically heterogeneous neurological disorders seen in children. A group of leukoencephalopathies characterised by white matter lesions progressing to multifocal cystic degeneration has been reported in various disorders, including mitochondrial enzyme deficiencies, leukodystrophies, and infectious processes. We report two patients with leukoencephalopathy showing progressive cystic changes on serial MRI, and magnetic resonance spectroscopy resembling progressive cavitating leukoencephalopathy.

Selective cerebral volume reduction in Rett syndrome: a multiple-approach MR imaging study

BACKGROUND AND PURPOSE

Previous studies have examined volumetric abnormalities in Rett syndrome (RTT), using MR imaging and focusing on selective changes. However, these studies preceded the identification of MECP2 as the gene mutated in most RTT cases. We studied regional brain volume changes as noted by MR imaging in girls with RTT who had mutations in the MECP2 gene and more or less severe clinical outcomes to further characterize the neuroanatomy of RTT and its correlations with clinical severity.

MATERIALS AND METHODS

Complementary semiautomated Talairach- and voxel-based approaches were used to study spoiled gradient-recalled acquisition sequence MR imaging scans from 23 girls with MECP2 mutations/RTT, including a pair of discordant monozygotic twins and 25 age-matched control girls. Both absolute and relative volumetric changes were examined to account for the well-documented global reduction in brain volume seen in RTT.

RESULTS

Absolute volumetric reductions were observed throughout the brain in RTT. Selective/relative decreases in parietal lobe gray matter, particularly in the dorsal parietal region, and mild, diffuse reductions in cortical white matter were observed in the RTT group compared with control subjects. In girls with RTT and a more severe phenotype, anterior frontal lobe volumes were relatively more reduced. Twin comparisons revealed selective preservation of the occipital cortex.

CONCLUSION

Selective reductions of dorsal parietal gray matter and preservation of the occipital cortex seem to be basic neuroanatomic features of RTT, whereas preferential reduction of the anterior frontal lobe appears to be a correlate of clinical severity in this disorder. The most affected brain regions include those that may underlie key functional deficits observed in RTT.

Enhanced cell death in MeCP2 null cerebellar granule neurons exposed to excitotoxicity and hypoxia

Rett syndrome (RTT) is associated with mutations in the transcriptional repressor gene MeCP2. Although the clinical and neuropathological signs of RTT suggest disrupted synaptic function, the specific role of methyl-CpG binding protein 2 (MeCP2) in postmitotic neurons remains relatively unknown. We examined whether MeCP2 deficiency in central neurons contributes to the neuropathogenesis in RTT. Primary cerebellar granule neuronal cultures from wild-type (WT) and MeCP2-/- mice were exposed to N-methyl-d-aspartate (NMDA) and AMPA-induced excitotoxicity and hypoxic-ischemic insult. The magnitude of cell death in MeCP2-/- cells after excitotoxicity and hypoxia was greater than in the WT littermate control cultures and occurred after shorter exposures that usually, in the WT, would not cause cell death. Pretreatment with the growth factor fibroblast growth factor 1 (FGF-1) under conditions at which WT cells showed complete neuroprotection, only partially protected MeCP2-/- cells. To elucidate specifically the effects of MeCP2 knockout (KO) on cell death, we examined two death cascade pathways. MeCP2-/- neurons exposed to 6 h of hypoxia exhibited enhanced activation of the proapoptotic caspase-3 and increased mitochondrial release of apoptosis inducing factor (AIF) compared with WT neurons, which did not show significant changes. However, pretreatment with the caspase inhibitor ZVAD-FMK had little or no effect on AIF release and its subcellular translocation to the nucleus, suggesting caspase-independent AIF release and their independent contribution to hypoxia-induced cell death. Reintroduction of intact MeCP2 gene in MeCP2-/- cells or MeCP2 gene silencing by MeCP2siRNA in WT cells further confirmed the differential sensitivity of the WT and MeCP2-/- cells and suggest a direct role of MeCP2 in cell death. These results clearly demonstrate increased cell death occurred in neurons lacking MeCP2 expression via both caspase- and AIF-dependent apoptotic mechanisms. Our findings suggest a novel, yet unknown, role for MeCP2 in central neurons in the control of neuronal response to cell death.

Spinal metastasis from renal cell carcinoma, 31 years following nephrectomy--case report

Most renal cell carcinomas recur or metastasize within 2 years. We present a 62-year-old lady with metastatic renal cell carcinoma in the spine, 31 years following nephrectomy of the primary tumor. This is the longest interval between diagnosis of primary renal cell carcinoma and metastasis reported in the literature.

Clinical and electrophysiological presentation of pronator syndrome

Median neuropathy at the elbow (pronator syndrome [PS]) is rare compared to compression at the wrist. We sought to evaluate the clinical/electrophysiological parameters of this focal neuropathy. Between 1992 and 2002, we retrospectively reviewed records of eighty-three limbs in seventy-two patients with PS. Electrodiagnostic data as well as clinical symptoms, physical findings, demographic information and treatment modalities were examined. The main symptoms were forearm pain, numbness and weakness. One patient (two limbs) had nocturnal paresthesias. Twenty-five limbs (30%) showed decreased median forearm velocity. Fifty-four (65%) had abnormal median sensory studies of either abnormal conduction velocity or amplitude. Needle exam showed an abnormality of at least one median innervated muscle, abductor pollicis brevis, flexor carpi radialis, or pronator teres, in 70% (58/83). Sixteen limbs were identified as having undergone surgical decompression. In the surgical group, 10/16 (63%) were found to have constriction with a band which was released during surgery. Eight of the sixteen patients who underwent surgery were found to have documented improvement. Eleven patients (13%) had undergone previous surgery for Carpal Tunnel Syndrome (CTS) without benefit. The clinical and electrophysiological features of PS are quite different from patients with CTS. Proper localization is crucial to treatment options. Surgery can provide benefit in selected cases.

Cystic leukoencephalopathy without megalencephaly: A distinct disease entity in 15 children

OBJECTIVE

To describe a distinctive syndrome of nonprogressive encephalopathy, normo- or microcephaly, and early onset of severe psychomotor impairment in 15 white patients, including two siblings and two first cousins.

METHODS AND RESULTS

MRI revealed bilateral cysts in the anterior part of the temporal lobe and white matter abnormalities with pericystic abnormal myelination and symmetric lesions in frontal and occipital periventricular regions. None of the usual inborn errors of metabolism/infectious diseases associated with leukoencephalopathy and bilateral anterior temporal lobe cysts were detected.

CONCLUSIONS

These patients' clinical signs and cranial MRI abnormalities are strikingly similar and may represent a distinctive disease with autosomal-recessive inheritance: cystic leukoencephalopathy without megalencephaly.

Thromboelastography in abruptio placentae

The purpose of this study was to document thromboelastographic (TEG) changes in abruptio placentae and to compare these results with that of conventional tests used to monitor coagulation. This was a prospective study of 30 patients with abruptio placentae. All coagulation investigations including the TEG were performed on admission, immediately following delivery, and after periods of 4 hours and 24 hours. Results showed that standard coagulation tests detected coagulation abnormalities except the platelet count returned to normal limits within 24 hours of delivery. There was strong correlation between fibrinogen levels and the TEG parameters, ma and k time (r=0.8). There was moderate correlation between platelet count and ma (r=0.6). In conclusion, minor abnormalities in the clotting profile are clinically unimportant. The TEG does not detect such minor abnormalities because of its inherent ability to test the coagulation cascade as a whole. Major abnormalities are clinically relevant and the TEG detect 75% of them. Further, the TEG establishes the diagnosis of hypercoagulability an early sign of disseminated intravascular coagulation. Although standard laboratory tests are still necessary to detect coagulation abnormalities on admission, the TEG is a useful test in large obstetric units where laboratory results are not immediately available for the purposes of monitoring and treating ongoing coagulation defects.

Leukoencephalopathy, cerebral calcifications, and cysts

We describe three cases of the rare syndrome of leukoencephalopathy, brain calcifications, and cysts. Conventional MRI, proton spectroscopy, and diffusion-weighted imaging yielded additional information on the disease. Imaging findings favor increased water content rather than a demyelinating process in the pathophysiology of this disease. Clinical features of Coats disease and consanguinity were also encountered.

Indian Agarwal megalencephalic leukodystrophy with cysts is caused by a common MLC1 mutation

BACKGROUND

A distinct clinical syndrome characterized by megalencephaly, mild to moderate cognitive decline, slowly progressive spasticity, ataxia, occasional seizures, and extensive white matter changes with temporal cysts by imaging studies has been described in a particular ethnic group (Agarwals) in India. This disorder is very similar to megalencephalic leukoencephalopathy with subcortical cysts (MLC), a newly characterized leukodystrophy whose molecular basis was recently shown to be mutations in a gene (KIAA0027) that has been renamed MLC1.

OBJECTIVE

To determine if this disorder among the Agarwals is due to mutations in MLC1 by a mutation screening study conducted on affected Agarwal patients.

METHODS

Genomic DNA from these Indian leukodystrophy patients was screened for mutations in the entire coding region, including the exon-intron boundaries, of the MLC1 gene.

RESULTS

Thirty-three affected individuals whose clinical and imaging presentations were consistent with MLC were screened. All were from northern India and included 31 known Agarwals, 1 non-Agarwal, and 1 adopted patient whose ethnicity is unknown. All 31 Agarwal patients tested positive for a homozygous insertion of a cytosine in exon 2. The adopted patient was homozygous for A157E. No mutation in the coding region was found in the non-Agarwal patient.

CONCLUSIONS

Indian patients with megalencephaly and MRI changes that show extensive white matter changes with temporal cysts should raise suspicion for MLC. Members of the Agarwal ethnic group affected with the disorder present with a mildly progressive course and show a common mutation (320insC) in the MLC1 gene, suggesting a founder effect.

A videotaped intervention to enhance child control and reduce anxiety of the pain of dental injections

AIM

While the psychological literature shows that perceptions of uncontrollability contribute to anxiety and other pathologies, interventions that enhance perceived control have been shown to reduce anxiety. This study attempted to assess a brief videotape to enhance child perceived control in a dental setting.

METHODS

101 children aged 7-9 years completed warm-up procedures and viewed either: a) the experimental intervention, a 2 minutes video of a dentist explaining what an injection will feel like and proposing hand raising as a signal mechanism; or b) the control condition, a 2 minutes video of Disneyland. Fear of dental injections was assessed on a 10 cm visual analogue scale before and after the intervention.

RESULTS

In the experimental group there was a significant fear reduction from pre- to post-intervention, while this was not the case in the control group. Children with higher pre-existing levels of fear benefited more from the intervention than children with lower levels of fear.

CONCLUSION

The results of this pilot study suggest that intervention packages that impact child control have promise in lowering anxiety.

MRI and proton MRSI in women heterozygous for X-linked adrenoleukodystrophy

OBJECTIVE

To utilize neuroimaging procedures to assess the extent of cerebral involvement in female subjects heterozygous for X-linked adrenoleukodystrophy (X-ALD).

METHODS

Brain MRI studies were performed in 76 female subjects heterozygous for X-ALD (mean age 43 years, range 8 to 75 years). Sixty-five had clinical evidence of spinal cord involvement resembling that in males with adrenomyeloneuropathy (AMN), two had clinical evidence of cerebral involvement, and nine showed no neurologic abnormality. Readers blinded to clinical findings further analyzed abnormal MRI studies. In eight women whose MRI results were normal, four-slice long echo time MRS imaging (MRSI) studies were performed and compared to those of eight age-matched controls.

RESULTS

MRI results were normal in 65 subjects and abnormal in 11. In eight of the latter group, the MRI changes were judged to be due to causes other than X-ALD. Lesions were attributed to X-ALD in the remaining three. Two of these patients had lesions that resembled those in male patients with cerebral X-ALD. In one patient with a mild AMN-like syndrome, brain MRI abnormalities were confined to the corticospinal tract. When compared to those of controls, MRSI studies in eight female patients with normal results on brain MRI showed a significant reduction of N-acetylaspartate/creatine and N-acetylaspartate/choline ratios in the internal capsule and corticospinal projection fibers. The N-acetylaspartate/choline ratio was significantly reduced in the parieto-occipital white matter and the choline/creatine ratio was significantly increased in the frontal white matter.

CONCLUSION

Brain involvement demonstrable by MRI is rare in female subjects heterozygous for X-ALD, including those who have clinical evidence of spinal cord involvement. Nevertheless, N-acetylaspartate levels are reduced in the corticospinal projection fibers in female subjects with normal results on MRI, suggesting axonal dysfunction.

Associations between MeCP2 mutations, X-chromosome inactivation, and phenotype

Rett syndrome is a neurodevelopmental disorder of early postnatal brain growth in girls. Patients show a normal neonatal period with subsequent developmental regression and a loss of acquired skills (communication and motor skills), deceleration of head growth, and development of typical hand stereotypies. Recent studies have shown that mutations in the X-linked methyl CpG binding protein 2 gene (MeCP2) cause most typical cases of Rett syndrome. The MeCP2 gene encodes a protein that binds methylated cytosine residues of CpG dinucleotides and mediates, with histone deacetylases and transcriptional repressors, the transcription "silencing" of other genes. Girls with Rett syndrome exhibit mosaic expression for the MeCP2 defect at the cellular level, with most patients showing random X-inactivation and approximately equal numbers of cells expressing the normal MeCP2 gene and the mutated MeCP2 gene. In rare cases, females with a MeCP2 mutation escape phenotypic expression of the disorder because of nonrandom X-inactivation and the preferential inactivation of the mutated MeCP2 allele. Nonrandom patterns of X-inactivation may also contribute to the clinical variability often seen in girls with Rett syndrome. The spectrum of clinical phenotype caused by MeCP2 mutations is wide, including milder "preserved speech" variants, the severe congenital Rett variant, and a subset of X-linked recessive mental retardation in boys. Studies have shown that atypical and classical Rett syndrome can caused by the same MeCP2 mutations, indicating clinical phenotype is variable even among girls with the same MeCP2 mutation. The relationship between type of MeCP2 mutation, X-inactivation status, and clinical phenotype of Rett syndrome is complex and likely involves other environmental and polygenic modifiers.