Rebecca J. Schultz

Influence of mutation type and X chromosome inactivation on Rett syndrome phenotypes.

We screened 71 sporadic and 7 familial Rett syndrome (RTT) patients for MECP2 mutations by direct sequencing and determined the pattern of X chromosome inactivation (XCI) in 39 RTT patients. We identified 23 different disease‐causing MECP2 mutations in 54 of 71 (76%) sporadic patients and in 2 of 7 (29%) familial cases. We compared electrophysiological findings, cerebrospinal fluid neurochemistry, and 13 clinical characteristics between patients carrying missense mutations and those carrying truncating mutations. Thirty‐one of 34 patients (91%) with classic RTT had random XCI. Nonrandom XCI was associated with milder phenotypes, including a mitigated classic RTT caused by a rare early truncating mutation. Patients with truncating mutations have a higher incidence of awake respiratory dysfunction and lower levels of cerebrospinal fluid homovanillic acid. Scoliosis is more common in patients with missense mutations. These data indicate that different MECP2 mutations have similar phenotypic consequences, and random XCI plays an important role in producing the full phenotypic spectrum of classic RTT. The association of early truncating mutations with nonrandom XCI, along with the fact that chimeric mice lacking methyl‐CpG‐binding protein 2 (MeCP2) function die during embryogenesis, supports the notion that RTT is caused by partial loss of MeCP2 function. Ann Neurol 2000;47:670–679

Electrocardiographic findings in Rett syndrome : an explanation for sudden death ?

Girls with Rett syndrome had significantly longer corrected QT intervals (p < 0.001) and more T-wave abnormalities (p < 0.001) than were found in age-matched healthy girls. With advancing stages of the syndrome, the proportion of corrected QT interval prolongations and T-wave changes increased. The findings suggest a possible cardiac basis for sudden, unexpected death in Rett syndrome.

Oropharyngeal dysfunction and gastroesophageal dysmotility are present in girls and women with Rett syndrome.

BACKGROUND Feeding impairment frequently complicates the course of children with neurologic disorders and places them at risk for malnutrition and growth failure. Although feeding abnormalities have been reported in female patients with Rett syndrome, the mechanisms that account for these findings have not been elucidated fully. This study was designed to characterize the clinical features of oropharyngeal and gastroesophageal dysfunction and their impact on the dietary intake and nutritional status of female subjects with Rett syndrome. METHODS The clinical features of oropharyngeal and gastroesophageal dysfunction in 13 female patients with Rett syndrome, (age range, 3.7 to 25.7 years) were characterized by an oral feeding assessment, swallowing function study, and upper gastrointestinal series. Growth, nutritional status, and body composition were determined by stadiometry and anthropometry. Dietary intakes were determined from 3-day food records. RESULTS Oropharyngeal dysfunction and gastroesophageal dysmotility were present in 100% and 69%, respectively, of the study patients with Rett syndrome. The scope and severity of these abnormalities were apparent only by videofluoroscopy. Abnormalities of oropharyngeal function included poor tongue mobility, reduced oropharyngeal clearance, and laryngeal penetration of liquids and solid food during swallowing. Esophageal dysmotility included absent primary or secondary waves, delayed emptying, atony, the presence of tertiary waves, spasm, and gastroesophageal reflux. Gastric dysmotility included diminished peristalsis or atony. Lower dietary energy intakes were associated with persistence of residue in the valleculae and pyriform sinuses and less body fat. CONCLUSION The prevalence of oropharyngeal dysfunction and gastroesophageal dysmotility warrants early diagnostic evaluation and intervention strategies to improve the nutritional status of girls and women with RS.

Extrapyramidal involvement in Rett's syndrome

Extrapyramidal dysfunction is poorly characterized in Retts syndrome, a neurodegenerative disorder in girls. We studied the motor and behavioral findings in 32 Retts syndrome patients, 21 months to.30 years old. In addition to the typical stereotyped movements and scoliosis, other motor disturbances included bruxism, sialorrhea, ocular deviations, parkin-sonian findings, dystonia, myoclonus, and athetosis. The types of movement disorders seemed to be age-related, with the hyperkinetic disorders occurring in the younger patients and the bradykinetic disorders occurring more frequently in the older patients.

Increased energy expenditure associated with repetitive involuntary movement does not contribute to growth failure in girls with Rett syndrome

OBJECTIVE To determine whether increased total daily energy expenditure (TDEE) associated with repetitive, involuntary movements contributes to growth failure in girls with Rett syndrome (RS). STUDY DESIGN Fourteen girls with RS and 11 healthy girls were studied for 10 days to obtain measurements of height, weight, body circumference, and skin-fold thickness with stadiometric and anthropometric methods; whole-body potassium by potassium 40 counting; 72-hour dietary energy intakes by test weighing; 24-hour activity patterns using observational methods; and TDEE using the doubly-labeled water technique. RESULTS TDEE, when adjusted for differences in lean body mass, did not differ significantly between girls with RS and healthy girls. Although girls with RS spent more waking hours in physical activity than their healthy counterparts (85%+/-10% vs. 73%+/-11% awake time per day, p < 0.05), their repetitive movements were not sufficiently intense to increase TDEE. However, girls with RS had significantly less lean body mass, but not body fat, which contributed to their lower absolute TDEE in comparison with that of healthy girls (845+/-251 vs. 1453+/-534 kcal/day, p < 0.01). Dietary energy intake, when adjusted for differences in body weight, was not significantly different in girls with RS compared with healthy girls. CONCLUSIONS Increased TDEE as a result of repetitive, involuntary movements does not explain the alterations in growth and body composition of girls with RS.

Altered Energy Balance May Account for Growth Failure in Rett Syndrome

To determine whether alterations in energy balance account for growth failure in Rett syndrome, we measured dietary energy intakes, fecal fat losses, activity patterns, and sleeping as well as quietly and actively awake metabolic rates in Rett syndrome girls and healthy controls. Dietary energy intakes and fecal fat losses did not differ between the groups. Metabolic rates while sleeping and quietly awake were 23% lower (P < .05) in Rett syndrome girls than in controls; metabolic rates while actively awake did not differ between the groups. However, because of the 2.4-fold greater time (P < .001) spent in involuntary motor movement, energy expenditure associated with activity was twofold greater (P < .05) in Rett syndrome girls than in controls. Although total daily energy expenditure of the two groups did not differ significantly, energy balance was less positive in the Rett syndrome girls than in the controls. This small difference in energy balance, if sustained over months to years, is sufficient to account for growth failure in Rett syndrome girls. (J Child Neurol 1994;9:315-319).

Zonisamide for absence seizures

This chart review investigated the efficacy and safety of zonisamide in 45 patients aged < or = 18 years with absence seizures. Of these patients, 23 (51.1%) achieved freedom from absence seizures. Two patients discontinued zonisamide, 1 for increased seizures and 1 for sleepiness and inefficacy. These data support the efficacy of zonisamide in treating absence seizures.

Organ growth in Rett syndrome: a postmortem examination analysis.

Rett syndrome is a disorder of unknown etiology in females that manifests as severe mental and motor retardation during the first years of life. A postnatal pattern of altered growth is its earliest clinical expression. Head growth decelerates during the first year of age and is followed by a decline in somatic (height/weight) growth. The decreased occipitofrontal circumference (OFC) is reflected in decreased brain size, and measurements of the dendrites of cortical neurons suggest that a developmental and growth arrest have occurred. To further document growth in Rett syndrome, measurements of organ weights, as recorded in 39 postmortem examination studies were compared with normal organ weights for females of comparable age and height. These organ weights suggest that the pattern of growth failure in Rett syndrome, as compared with other forms of mental handicap, such as Down syndrome and Turners syndrome, may be unique. In Rett syndrome the rate of brain growth, as derived from OFC, decelerates after birth. The increment in normal brain weight after 4 years of age, the age of the first postmortem examinations, is not observed in the Rett brain. The heart, kidneys, liver, and spleen grow at the normally defined rate until 8-12 years of age, when their growth rate decelerates, but their growth continues achieving organ weights that are appropriate for the height of the female. Adrenal weights are normal. These observations suggest that despite a generalized decreased growth in Rett syndrome the brain may be preferentially affected in this syndrome.

Fractional calcium absorption is increased in girls with rett syndrome

Background: Rett syndrome (RTT), an X-linked neurodevelopmental disorder primarilyaffecting girls, is characterized in part by osteopenia and increased risk of skeletal fractures. We hypothesized that decreased intestinal calcium (Ca) absorption relative to dietary Ca intake and increased renal Ca excretion might cause these problems in RTT. Objective: We measured fractional Ca absorption, urinary Ca loss, dietary Ca intake, and the hormonal factors regulating Ca metabolism to determine whether abnormalities in Ca balance might relate to poor bone mineralization in RTT girls and to evaluate the contribution of these factors to the overall dietary Ca needs of RTT girls. Study Design: Ten RTT girls and 10 controls, matched for age, sex, and pubertal status, were given a 3 day constant Ca diet that mimicked their habitual intakes. At the end of each dietary period, girls received single doses of 42Ca (intravenous) and 46Ca (oral). Fractional urinary excretion of 42Ca, 46Ca, 24 hour urinary Ca, and urinary cortisol excretion were determined. Serum Ca, phosphorous, alkaline phosphatase, vitamin D metabolites, parathyroid hormone (PTH), and osteocalcin were measured in the postabsorptive state. Bone mineral content (BMC) was measured by dual-energy x-ray absorptiometry. Results: Fractional Ca absorption was significantly higher in RTT than in control girls (mean ± SDp, 52 vs. 33 ± 13%). Dietary Ca intake (mean ± SDp, 1,100 vs. 1,446 ± 440 g/d) and net Ca absorption (mean ± SDp, 513 vs. 362 ± 306 mg/d) did not differ significantly between RTT and controls, respectively. Although urinary Ca excretion did not differ between groups, the increased urinary Ca:creatinine ratio (mean ± SDp, 0.39 vs. 0.23 ± 0.38) was consistent with clinical hypercalcuria and paralleled the significantly increased urinary cortisol excretion (mean ± SDp, 3.1 vs. 1.7 ± 1.1 mg/kg lean body mass per day) in the RTT girls. BMC was significantly lower in RTT than in controls (mean ± SDp, 527 vs. 860 ± 275 g). Serum Ca, P, alkaline phosphatase, vitamin D metabolites, PTH, and osteocalcin concentrations did not differ between the groups. Conclusion: Fractional Ca absorption showed a compensatory increase in the presence of adequate dietary Ca intakes, mild hypercalcuria, and pronounced bone mineral deficits in RTT girls. Whether supplemental dietary Ca could enhance fractional Ca absorption and improve bone mineralization in RTT girls is unknown.

Vagus nerve stimulation for treatment of epilepsy in Rett syndrome

This case series presents the outcomes of seven females with Rett syndrome and medically refractory epilepsy who were treated with adjunctive vagus nerve stimulation (VNS) therapy for a minimum of 12 months. Patients ranged in age from 1 to 14 years (median age 9 y) at the time of implantation, had experienced seizures for a median period of approximately 6 years, and had failed at least two trials of antiepileptic drugs before receiving VNS. The median number of seizures per month was 150 (range 12-3600). At 12 months, six females had >or=50% reduction in seizure frequency. VNS was safe and well tolerated, with no surgical complications and no patients requiring explantation of the device. Quality of life outcomes of note among these patients included reports at 12 months of increased alertness among all seven patients. No change in mood or communication abilities was noted.