Developmental trends of sleep-disordered breathing in Prader-Willi syndrome: the role of obesity

Neurobehavioral Dimensions of Prader Willi Syndrome: Relationships Between Sleep and Psychosis-Risk Symptoms

Background

Prader Willi Syndrome (PWS) is a genetic disorder caused by the absence of expression of the paternal copies of maternally imprinted gene(s) located at 15q11-q13. While the physical and medical characteristics of PWS, including short stature, hyperphagia and endocrine dysfunction are well-characterized, systematic investigation of the long-recognized psychiatric manifestations has been recent.

Methods

Here, we report on the first remote (web-based) assessment of neurobehavioral traits, including psychosis-risk symptoms (Prodromal Questionnaire-Brief Version; PQ-B) and sleep behaviors (Pittsburgh Sleep Quality Index), in a cohort of 128 participants with PWS, of whom 48% had a paternal deletion, 36% uniparental disomy, 2.4% an imprinting mutation and 13% unknown mutation (mean age 19.3 years ± 8.4; 53.9% female). We aimed to identify the most informative variables that contribute to psychosis-risk symptoms. Multiple domains of cognition (accuracy and speed) were also assessed in a subset of PWS participants (n = 39) using the Penn Computerized Neurocognitive Battery (Penn-CNB).

Results

Individuals with PWS reported a range of psychosis-risk symptoms, with over half reporting cognitive disorganization (63.1%) and about one third reporting unusual beliefs (38.6%) and/or suspiciousness (33.3%). Subjectively-reported sleep quality, nap frequency, sleep duration, sleep disturbance, and daytime dysfunction were significant predictors of psychosis-risk symptom frequency and severity (all p's < 0.029). Sleep disturbance ratings were the strongest predictors of psychosis-risk symptoms. Regarding cognition, individuals with PWS showed the most prominent deficits in accuracy on measures of social cognition involving faces, namely Face Memory, Age Differentiation and Emotion Recognition, and greatest slowing on measures of Attention and Emotion Recognition. However, there were no significant differences in psychosis-risk symptoms or cognitive performance as a function of PWS genetic subtype.

Conclusions

PWS is associated with a high prevalence of distressing psychosis-risk symptoms, which are associated with sleep disturbance. Findings indicate that self/parent-reported neurobehavioral symptoms and cognition can be assessed remotely in individuals with PWS, which has implications for future large-scale investigations of rare neurogenetic disorders.

Sleep Disorders in Adults with Prader–Willi Syndrome: Review of the Literature and Clinical Recommendations Based on the Experience of the French Reference Centre

Prader–Willi syndrome (PWS) is a rare, genetic, multisymptomatic, neurodevelopmental disease commonly associated with sleep alterations, including sleep-disordered breathing and central disorders of hypersomnolence. Excessive daytime sleepiness represents the main manifestation that should be addressed by eliciting the detrimental effects on quality of life and neurocognitive function from the patients’ caregivers. Patients with PWS have impaired ventilatory control and altered pulmonary mechanics caused by hypotonia, respiratory muscle weakness, scoliosis and obesity. Consequently, respiratory abnormalities are frequent and, in most cases, severe, particularly during sleep. Adults with PWS frequently suffer from sleep apnoea syndrome, sleep hypoxemia and sleep hypoventilation. When excessive daytime sleepiness persists after adequate control of sleep-disordered breathing, a sleep study on ventilatory treatment, followed by an objective measurement of excessive daytime sleepiness, is recommended. These tests frequently identify central disorders of hypersomnolence, including narcolepsy, central hypersomnia or a borderline hypersomnolent phenotype. The use of wake-enhancing drugs (modafinil, pitolisant) is discussed in multidisciplinary expert centres for these kinds of cases to ensure the right balance between the benefits on quality of life and the risk of psychological and cardiovascular side effects.

Prevalence and Phenotype of Sleep Disorders in 60 Adults With Prader-Willi Syndrome

Study Objectives

Excessive sleepiness is a common symptom in Prader-Willi syndrome (PWS), and it negatively impacts the quality of life. Obstructive sleep apnea and narcolepsy phenotypes have been reported in PWS. We characterized sleep disorders in a large cohort of adults with PWS.

Methods

All consecutive patients with genetically confirmed PWS unselected for sleep-related symptoms, underwent a clinical interview, polysomnography, and multiple sleep latency tests (MSLT, n = 60), followed by long-term (24 hours) polysomnography (n = 22/60).

Results

Among 60 adults evaluated (57% female, aged 25 ± 10 years, body mass index: 39 ± 12 kg/m2), 67% reported excessive sleepiness. According to the sleep study results, 43% had a previously unrecognized hypersomnia disorder, 15% had an isolated sleep breathing disorder, 12% had combined hypersomnia disorder and untreated breathing sleep disorder, and only 30% had normal sleep. Isolated hypersomnia disorder included narcolepsy in 35% (type 1, n = 1, and type 2, n = 8), hypersomnia in 12% (total sleep time >11 hours, n = 2, and MSLT <8 minutes, n = 1), and borderline phenotype in 53% (≥2 sleep onset in REM periods and MSLT >8 minutes, n = 10, and 8 minutes < MSLT < 10 minutes, n = 4). Sleep breathing disorders, isolated and combined, included obstructive sleep apnea (n = 14, already treated in seven), sleep hypoxemia (n = 1) and previously undiagnosed hypoventilation (n = 5). Modafinil was taken by 16 patients (well tolerated in 10), resulting in improved sleepiness over a mean 5-year follow-up period.

Conclusion

Sleepiness affects more than half of adult patients with PWS, with a variety of hypersomnia disorder (narcolepsy, hypersomnia, and borderline phenotypes) and breathing sleep disorders. Earlier diagnosis and management of sleep disorders may improve sleepiness, cognition, and behavior in these patients.

Prader-Willi Syndrome: A spectrum of anatomical and clinical features

Prader-Willi Syndrome (PWS) is estimated to affect 400,000 people worldwide. First described clinically in 1956, PWS is now known to be a result of a genetic mutation, involving Chromosome 15. The phenotypical appearance of individuals with the syndrome follows a similar developmental course. During infancy, universal hypotonia accompanied by feeding problems, hypogonadism, and dolichocephaly are evident. Characteristic facial features such as narrow bifrontal diameter, almond-shaped eyes, and small mouth (with downturned corners and thin upper lip) may also be evident at this stage. In early childhood, the craniofacial features become more obvious and a global developmental delay is observed. Simultaneously, individuals develop hyperphagia that leads to excessive or rapid weight gain, which, if untreated, exists throughout their lifespan and may predispose them to numerous, serious health issues. The standard tool for differential diagnosis of PWS is genetic screening; however, clinicians also need to be aware of the characteristic features of this disorder, including differences between the genetic subtypes. As the clinical manifestations of the syndrome vary between individuals and become evident at different developmental time points, early assessment is hindered. This article focuses on the clinical and anatomical manifestations of the syndrome and highlights the areas of discrepancy and limitations within the existing literature. Clin. Anat. 29:590-605, 2016. © 2016 Wiley Periodicals, Inc.

Clinically important age-related differences in sleep related disordered breathing in infants and children with Prader-Willi Syndrome

Background

Sleep related disordered breathing (SDB) in pediatric Prader-Willi Syndrome is gaining increased attention due to the possible association of growth hormone therapy, SDB and sudden death. However data on the patterns of SDB and their management, particularly in infants in this population, is lacking.

Objective

The aim of this study was to 1) describe patterns of SDB in growth hormone naive infants with PWS and the management of these disorders in our institution 2) Compare the patterns of sleep disorders between infants and children with PWS.

Methods and Design

Polysomnograms of infants and children (0–18 years of age) with Prader-Willi Syndrome were reviewed. Age, sex, anthropometrics, sleep architecture, obstructive and central apnea indices and oxygen saturations were recorded. Data of infants with central sleep apnea treated with oxygen were analyzed to evaluate the efficacy of this treatment. The main outcome measures were obstructive and central apnea indices on a polysomnogram.

Results

Data of 44 patients, 23 under 2 years of age and 21 older children were included. Infants when compared with older children were more likely to experience central sleep apnea (43% vs. 5%; p = 0.003). In older children obstructive was significantly more prevalent than central sleep apnea. Supplemental oxygen was used to treat 9/23 infants with central sleep apnea. Oxygen therapy resulted in a significant decrease in the median central apnea index from 14 (5,68) to 1 (0,6; p = 0.008) events/hour and an improvement in the oxygen saturation nadir from 70% (52, 92) to 81% (64, 95; p = 0.080).

Conclusions

Central sleep apnea with associated oxygen desaturations is more prevalent in infants compared with older children with Prader-Willi Syndrome. Supplemental oxygen was efficacious in treating central sleep apnea in infants. Routine sleep surveillance for all children with Prader-Willi Syndrome and treatment with oxygen for central sleep apnea should be considered.

Hereditary spastic paraplegia: clinico-pathologic features and emerging molecular mechanisms

Hereditary spastic paraplegia (HSP) is a syndrome designation describing inherited disorders in which lower extremity weakness and spasticity are the predominant symptoms. There are more than 50 genetic types of HSP. HSP affects individuals of diverse ethnic groups with prevalence estimates ranging from 1.2 to 9.6 per 100,000. Symptoms may begin at any age. Gait impairment that begins after childhood usually worsens very slowly over many years. Gait impairment that begins in infancy and early childhood may not worsen significantly. Postmortem studies consistently identify degeneration of corticospinal tract axons (maximal in the thoracic spinal cord) and degeneration of fasciculus gracilis fibers (maximal in the cervico-medullary region). HSP syndromes thus appear to involve motor-sensory axon degeneration affecting predominantly (but not exclusively) the distal ends of long central nervous system (CNS) axons. In general, proteins encoded by HSP genes have diverse functions including (1) axon transport (e.g. SPG30/KIF1A, SPG10/KIF5A and possibly SPG4/Spastin); (2) endoplasmic reticulum morphology (e.g. SPG3A/Atlastin, SPG4/Spastin, SPG12/reticulon 2, and SPG31/REEP1, all of which interact); (3) mitochondrial function (e.g. SPG13/chaperonin 60/heat-shock protein 60, SPG7/paraplegin; and mitochondrial ATP6); (4) myelin formation (e.g. SPG2/Proteolipid protein and SPG42/Connexin 47); (5) protein folding and ER-stress response (SPG6/NIPA1, SPG8/K1AA0196 (Strumpellin), SGP17/BSCL2 (Seipin), "mutilating sensory neuropathy with spastic paraplegia" owing to CcT5 mutation and presumably SPG18/ERLIN2); (6) corticospinal tract and other neurodevelopment (e.g. SPG1/L1 cell adhesion molecule and SPG22/thyroid transporter MCT8); (7) fatty acid and phospholipid metabolism (e.g. SPG28/DDHD1, SPG35/FA2H, SPG39/NTE, SPG54/DDHD2, and SPG56/CYP2U1); and (8) endosome membrane trafficking and vesicle formation (e.g. SPG47/AP4B1, SPG48/KIAA0415, SPG50/AP4M1, SPG51/AP4E, SPG52/AP4S1, and VSPG53/VPS37A). The availability of animal models (including bovine, murine, zebrafish, Drosophila, and C. elegans) for many types of HSP permits exploration of disease mechanisms and potential treatments. This review highlights emerging concepts of this large group of clinically similar disorders.

Prader-Willi syndrome: A primer for clinicians

The advent of sensitive genetic testing modalities for the diagnosis of Prader-Willi syndrome has helped to define not only the phenotypic features of the syndrome associated with the various genotypes but also to anticipate clinical and psychological problems that occur at each stage during the life span. With advances in hormone replacement therapy, particularly growth hormone children born in circumstances where therapy is available are expected to have an improved quality of life as compared to those born prior to growth hormone.

This manuscript was prepared as a primer for clinicians-to serve as a resource for those of you who care for children and adults with Prader-Willi syndrome on a daily basis in your practices. Appropriate and anticipatory interventions can make a difference.

Polysomnographic characteristics in patients with Prader-Willi syndrome

To evaluate the occurrence of sleep-disordered breathing and to clarify the characteristics of sleep among patients with Prader-Willi syndrome (PWS). Overnight continuous EEG-polysomnographic studies were performed in 30 patients with PWS (16 males and 14 females; mean age, 7.4 +/- 4.1 years; age range, 1-19 years) unselected for sleep disturbance. The baseline arterial oxygen saturation (SpO2) was 96.6 +/- 0.6%, with a nadir of 77.2 +/- 10.2%. The rapid eye movement (REM) latency was 67.4 +/- 30.0 min. The percent of total sleep time spent in sleep stages 1, 2, slow wave, and REM were 13.1 +/- 8.2%, 41.9 +/- 10.5%, 21.5 +/- 9.4%, and 21.1 +/- 5.7%, respectively. The respiratory disturbance index (RDI) was 5.8 +/- 3.7/hr and desaturation index (DI) was 8.1 +/- 7.3/hr, respectively. Age-adjusted BMI was associated with more severe hypoxemia during sleep (baseline SpO2, r = -0.53, P < 0.01; nadir SaO2, r = -0.65, P < 0.01; RDI, r = 0.37, P < 0.05; DI, r = 0.53, P < 0.01) and more sleep disruption (arousal index, r = 0.46, P < 0.01). There were no significant associations between gender or genotype pattern (deletion vs. uniparental disomy) and the results of polysomnography. Sleep hypoxemia and sleep disruption are more prevalent in patients with PWS than in normal children. Obesity in these patients is associated with more severe sleep-disordered breathing.

Prader-Willi syndrome: an update and review for the primary pediatrician

Prader-Willi syndrome, the first known human genomic imprinting disorder, is one of the most common micro-deletion syndromes. Prader-Willi syndrome is caused by the absence of certain paternally inherited genes on the long arm of chromosome 15, resulting in a complete absence of the active copy of the genetic information in this region. It is most commonly known for its food-related characteristics of hyperphagia, food-seeking behavior, and consequent obesity. Primary care physicians play an important role in the care of children with Prader-Willi syndrome, from recognizing the presenting signs and symptoms at its various stages to understanding their unique medical, developmental, behavioral, and dietary issues. They can also serve as a valuable source of support and advocacy for the family. This article reviews the current state of knowledge about Prader-Willi syndrome and discusses up-to-date understanding of the management of this condition.

Breathing disorders in Prader-Willi syndrome: the role of obesity, growth hormone treatment and upper respiratory tract infections

Prader-Willi syndrome is a neurogenetic disorder characterized by a number of signs and symptoms, including muscular hypotonia in infancy, hypogonadism, obesity and short stature. Neurobehavioral abnormalities and cognitive impairment are common. In addition, breathing abnormalities have been described, including sleep-related breathing disorders, abnormal chemoreceptor sensitivity and pulmonary function abnormalities. Growth hormone treatment is now widely used in children with Prader-Willi syndrome to improve growth and body composition. Over the last 4 years, case reports have been published concerning unexpected death, many of which were related to respiratory abnormalities. This review focuses on breathing abnormalities in Prader-Willi syndrome individuals and the influence of obesity, growth hormone treatment and upper respiratory tract infections.

NIPA1(SPG6), the basis for autosomal dominant form of hereditary spastic paraplegia, encodes a functional Mg2+ transporter

Mutations in the NIPA1(SPG6) gene, named for "nonimprinted in Prader-Willi/Angelman" has been implicated in one form of autosomal dominant hereditary spastic paraplegia (HSP), a neurodegenerative disorder characterized by progressive lower limb spasticity and weakness. However, the function of NIPA1 is unknown. Here, we show that reduced magnesium concentration enhances expression of NIPA1 suggesting a role in cellular magnesium metabolism. Indeed NIPA1 mediates Mg2+ uptake that is electrogenic, voltage-dependent, and saturable with a Michaelis constant of 0.69+/-0.21 mM when expressed in Xenopus oocytes. Subcellular localization with immunofluorescence showed that endogenous NIPA1 protein associates with early endosomes and the cell surface in a variety of neuronal and epithelial cells. As expected of a magnesium-responsive gene, we find that altered magnesium concentration leads to a redistribution between the endosomal compartment and the plasma membrane; high magnesium results in diminished cell surface NIPA1 whereas low magnesium leads to accumulation in early endosomes and recruitment to the plasma membrane. The mouse NIPA1 mutants, T39R and G100R, corresponding to the respective human mutants showed a loss-of-function when expressed in oocytes and altered trafficking in transfected COS7 cells. We conclude that NIPA1 normally encodes a Mg2+ transporter and the loss-of function of NIPA1(SPG6) due to abnormal trafficking of the mutated protein provides the basis of the HSP phenotype.

Sleep-related breathing disorders in prepubertal children with Prader-Willi syndrome and effects of growth hormone treatment

CONTEXT

Recently, several cases of sudden death in GH-treated and non-GH-treated, mainly young Prader-Willi syndrome (PWS), patients were reported. GH treatment in PWS results in a remarkable growth response and an improvement of body composition and muscle strength. Data concerning effects on respiratory parameters, are however, limited.

OBJECTIVE

The objective of the study was to evaluate effects of GH on respiratory parameters in prepubertal PWS children.

DESIGN

Polysomnography was performed before GH in 53 children and repeated after 6 months of GH treatment in 35 of them.

PATIENTS

Fifty-three prepubertal PWS children (30 boys), with median (interquartile range) age of 5.4 (2.1-7.2) yr and body mass index of +1.0 sd score (-0.1-1.7).

INTERVENTION

Intervention included treatment with GH 1 mg/m2.d.

RESULTS

Apnea hypopnea index (AHI) was 5.1 per hour (2.8-8.7) (normal 0-1 per hour). Of these, 2.8 per hour (1.5-5.4) were central apneas and the rest mainly hypopneas. Duration of apneas was 15.0 sec (13.0-28.0). AHI did not correlate with age and body mass index, but central apneas decreased with age (r = -0.34, P = 0.01). During 6 months of GH treatment, AHI did not significantly change from 4.8 (2.6-7.9) at baseline to 4.0 (2.7-6.2; P = 0.36). One patient died unexpectedly during a mild upper respiratory tract infection, although he had a nearly normal polysomnography.

CONCLUSIONS

PWS children have a high AHI, mainly due to central apneas. Six months of GH treatment does not aggravate the sleep-related breathing disorders in young PWS children. Our study also shows that monitoring during upper respiratory tract infection in PWS children should be considered.

Sleep cycling alternating pattern (CAP) expression is associated with hypersomnia and GH secretory pattern in Prader–Willi syndrome

BACKGROUND AND PURPOSE

Hypersomnia, sleep-disordered breathing and narcoleptic traits such as rapid eye movement (REM) sleep onset periods (SOREMPs) have been reported in Prader-Willi syndrome (PWS). In a group of young adult patients with genetically confirmed PWS we evaluated sleep and breathing polysomnographically, including cycling alternating pattern (CAP), and we analyzed the potential interacting role of sleep variables, sleep-related breathing abnormalities, hypersomnia, severity of illness variables and growth hormone (GH) secretory pattern.

PATIENTS AND METHODS

Eleven males and 7 females (mean age: 27.5+/-5.5 years) were submitted to a full night of complete polysomnography and the multiple sleep latency test (MSLT). GH secretory pattern was evaluated by a standard GH-releasing hormone plus arginine test. Sixteen non-obese healthy subjects without sleep disturbances were recruited as controls.

RESULTS

Compared to controls PWS patients showed reduced mean MSLT score (P<0.001), reduced mean latency of sleep (P=0.03), increased REM sleep periods (P=0.01), and increased mean CAP rate/non-rapid eye movement (NREM) (P<0.001). Only four PWS patients had apnea/hypopnea index (AHI)>or=10. Conversely, significant nocturnal oxygen desaturation was frequent (83% of patients) and independent from apneas or hypopneas. In the PWS group, CAP rate/NREM showed a significant negative correlation with MSLT score (P=0.02) independently from arousals, respiratory disturbance variables, severity of illness measured by Holm's score or body mass index (BMI). PWS patients with CAP expression characterized by higher proportion of A1 subtypes presented less severe GH deficiency (P=0.01).

CONCLUSIONS

Our study suggests a relationship between hypersomnia and CAP rate, and between CAP expression and GH secretory pattern in PWS, possibly reflecting underlying central dysfunctions.

Hereditary spastic paraplegia

The hereditary spastic paraplegias (HSPs) comprise a large group of inherited neurologic disorders. HSP is classified according to the mode of inheritance, the HSP locus when known, and whether the spastic paraplegia syndrome occurs alone or is accompanied by additional neurologic or systemic abnormalities. Analysis of 11 recently discovered HSP genes provides insight into HSP pathogenesis. Hereditary spastic paraplegia is a clinical diagnosis for which laboratory confirmation is sometimes possible, and careful exclusion of alternate and co-existing disorders is an important element in HSP diagnosis. Treatment for HSP is presently limited to symptomatic reduction of muscle spasticity, reduction in urinary urgency, and strength and gait improvement through physical therapy. Prenatal genetic testing in HSP is possible for some individuals with the increasing availability of HSP gene analysis.

Sleep-disordered breathing in Prader-Willi syndrome and its association with neurobehavioral abnormalities

OBJECTIVES

To determine the prevalence and type of sleep-disordered breathing among patients with Prader-Willi syndrome (PWS) and its relationship to such neurobehavioral abnormalities as mental retardation, obsessive-compulsive behavior, and conduct disorders.

STUDY DESIGN

Polysomnography (PSG) studies were conducted in 13 unselected subjects with PWS (age 1.5 to 28 years). PSG results were compared with tests of behavior and cognition (Development Behavior Checklist [DBC], Auditory Continuous Performance Test [ACPT], and Wechsler Intelligence Scale appropriate for age).

RESULTS

Nine of 13 (69%) subjects had > 10 apneas and hypopneas per hour of sleep. Apart from a 2-year-old subject with normal body weight who demonstrated severe central hypopnea in rapid eye movement sleep, the sleep-breathing disturbance was due to upper airway obstruction. Age-adjusted body mass index was associated with more severe hypoxemia during sleep (min SaO2, r = -.87, P < .005) and more sleep disruption (arousals/hour of sleep, r = .62, P < .05; sleep efficiency, r = -.66, P < .05). Increasing severity of obstructive sleep apnea (OSA) or sleep disturbance was associated with daytime inactivity/sleepiness and autistic-relating behavior (DBC) and with impulsiveness (ACPT). Unexpectedly, sleep hypoxemia appeared to be predictive of increased performance IQ.

CONCLUSIONS

OSA is prevalent among subjects with PWS and is associated with increased body mass, daytime inactivity/ sleepiness, and some behavioral disturbances.

Cause of sudden, unexpected death of Prader-Willi syndrome patients with or without growth hormone treatment

Patients with Prader-Willi syndrome (PWS) are recognized to have a tendency of sudden, unexpected death (SED), but its exact cause is unknown because of paucity of such case reports. Since growth hormone (GH) treatment was applied to PWS patients worldwide, several cases of death have been reported. However, whether the therapy is directly related to their SED remains unknown, too. We collected 13 deceased PWS patients (Group A, aged 9 months to 34 years) who had never received GH therapy, and seven deceased patients (Group B, all boys aged 0.7-15 years) having received the therapy from the registration in PWS-patient-support associations and from the literature, respectively. We then compared the cause of SED between the two groups. Irrespective of GH therapy, SED of infants under age 1 year was associated with milk aspiration or hypothalamic dysregulation of respiration, while SED of patients in early childhood or adolescence occurred at sleeping in association with preceding viral infections. In contrast, SED of four adult (>20 years of age) patients who never received GH therapy was associated with complications, such as leg cellulites and pulmonary embolism, secondary to massive obesity and diabetes mellitus (DM). Two Group-B patients (aged 14 and 20 years) without any obesity-related or diabetes-related complications died of drowning in a bath tub, and their drowning death could be related to poor respiratory control. These findings indicated that the cause of SED is not essentially different between PWS patients with and without GH treatment. Deceased PWS patients may have had underlying respiratory dysregulation and hypothalamic dysfunction, and GH therapy might have led to certain obstructive respiratory disturbances that exacerbated the respiratory conditions. This will call clinicians' attention when using GH in PWS patients, for example, careful determination of the dose of GH and careful monitoring of patient's respiratory conditions, especially in male obese patients with respiratory problems.

Prader-Willi syndrome: causes of death in an international series of 27 cases

Prader-Willi syndrome (PWS) is a complex condition with many medical and psychological features. In individuals with this syndrome, causes of death were studied. Data of 27 case reports were collected. Ages at death ranged from neonatal to 68 years. None of the individuals were treated with growth hormone (GH). Most cases were not completely documented and autopsy was performed in a minority of cases only. In five cases, death was considered not to be causally related to PWS. Hypotonia with hypoventilation was noted in the babies, and acute respiratory illness with unexpected sudden death was experienced in young children with PWS. Two young children died after a short period of fever and gastroenteritis. Obesity and its complications leading to death were pronounced in the adult group. One (possibly two) adult(s) died from gastric dilatation and shock. Based on these data, some cautious conclusions can be drawn. In babies with PWS hypoventilation is a risk factor; upper airway infection may be more serious than anticipated and any other clinical features pointing to an infection should be taken very seriously. Therefore, young infants with PWS hospitalized with an upper airway infection and/or hypoventilation or gastroenteritis symptoms, should be closely monitored. Early diagnosis and prevention of overweight is a major factor in preventing early causes of death in individuals with PWS. In the adult group, weight reduction is important but difficult to manage. Sleep apnea should be recognized and treated. Pain in the upper stomach and/or vomiting should be taken as a possible sign of acute intestinal dilatation; intravenous support may be life saving.

Neurologic disorders masquerading as pediatric sleep problems

Neurologic disorders may present or masquerade as pediatric sleep problems and fool the pediatrician, which may delay diagnosis and treatment. Many of the sleep problems in children with neurologic disorders arise directly from primary dysfunction or delayed maturation of their sleep-wake regulation systems. It is important to realize that nocturnal frontal lobe seizures or cluster headaches can be mistaken for night terrors, and craniopharyngiomas or myotonic dystrophy may present as narcolepsy-cataplexy. Hypothalamic dysfunction may explain not only the impaired circadian rhythm disorders in children with profound mental retardation but also excessive sleepiness and hyperphagia in Prader-Willi and Kleine-Levin syndromes. Intellectually challenged children perform better, learn more, and are better behaved with sufficient restorative sleep.

Hereditary spastic paraparesis: disrupted intracellular transport associated with spastin mutation

The commonest cause of hereditary spastic paraplegia (HSP) is mutation in the spastin gene. Both the normal function of spastin in the central nervous system and the mechanism by which mutation in spastin causes axonal degeneration are unknown. One hypothesis is that mutant spastin disrupts microtubule dynamics, causing an impairment of organelle transport on the microtubule network, which leads to degeneration in the distal parts of long axons. To study this neuronal and non-neuronal cells were transfected with either wild type or mutant spastin proteins. We demonstrated evidence of a transient interaction of wild-type spastin with microtubules, with resulting disassembly of microtubules, supporting a role for wild-type spastin as a microtubule-severing protein. Mutant spastin demonstrated an abnormal interaction with microtubules, colocalizing with but no longer severing microtubules. The abnormal interaction of mutant spastin with microtubules was demonstrated to be associated with an abnormal perinuclear clustering of mitochondria and peroxisomes, suggestive of an impairment of kinesin-mediated intracellular transport. Our findings indicate that an abnormal interaction of mutant spastin with microtubules, which disrupts organelle transport on the microtubule cytoskeleton, is likely to be the primary disease mechanism in HSP caused by missense mutations in the spastin gene.

Narrowing of the critical region in autosomal recessive spastic paraplegia linked to the SPG5 locus

Hereditary spastic paraplegias are neurodegenerative disorders characterized clinically by progressive spasticity of the lower limbs. They are inherited as autosomal dominant, autosomal recessive, and X-linked traits. Four Italian families with autosomal recessive pure spastic paraplegia are reported. We show evidence of linkage to the SPG5 locus on chromosome 8p and our data reduce the candidate interval for SPG5 to the11-cM interval spanned by D8S285 and D8S544. We also report the search for mutations in five genes located in the region and their exclusion as candidates for SPG5.

Absence of Ndn, encoding the Prader-Willi syndrome-deleted gene necdin, results in congenital deficiency of central respiratory drive in neonatal mice

necdin (Ndn) is one of a cluster of genes deleted in the neurodevelopmental disorder Prader-Willi syndrome. necdin is upregulated during neuronal differentiation and is thought to play a role in cell cycle arrest in terminally differentiated neurons. Most necdin-deficient Ndn(tm2Stw) mutant pups carrying a targeted replacement of Ndn with a lacZ reporter gene die in the neonatal period of apparent respiratory insufficiency. We now demonstrate that the defect can be explained by abnormal neuronal activity within the putative respiratory rhythm-generating center, the pre-Bötzinger complex. Specifically, the rhythm is unstable with prolonged periods of depression of respiratory rhythmogenesis. These observations suggest that the developing respiratory center is particularly sensitive to loss of necdin activity and may reflect abnormalities of respiratory rhythm-generating neurons or conditioning neuromodulatory drive. We propose that necdin deficiency may contribute to observed respiratory abnormalities in individuals with Prader-Willi syndrome through a similar suppression of central respiratory drive.

Infantile ascending hereditary spastic paralysis (IAHSP): clinical features in 11 families

OBJECTIVE

To report clinical, neuroradiologic, neurophysiologic, and genetic findings on 16 patients from 11 unrelated families with a remarkable uniform phenotype characterized by infantile ascending hereditary spastic paralysis (IAHSP).

METHODS

Sixteen patients from 11 families, originating from North Africa and Europe, who presented severe spastic paralysis and ascending progression were studied.

RESULTS

Spastic paraplegia started in the first 2 years of life in most patients and extended to the upper limbs by the end of the first decade. The disease progressed to tetraplegia, anarthria, dysphagia, and slow eye movements in the second decade. The clinical course showed a long survival and preservation of intellectual skills. Clinical, neuroradiologic, and neurophysiologic findings were consistent with a relatively selective early involvement of the corticospinal and corticobulbar pathways. No signs of lower motor neuron involvement were observed, whereas motor evoked potentials demonstrated predominant involvement of the upper motor neurons. MRI was normal in young patients but showed brain cortical atrophy in the oldest, predominant in the motor areas, and T2-weighted bilateral hyperintense signals in the posterior arm of the internal capsule. The ALS2 gene, recently found mutated in consanguineous Arabic families with either an ALS2 phenotype or a juvenile-onset primary lateral sclerosis, was analyzed. Alsin mutations were found in only 4 of the 10 families, whereas haplotype analysis excluded the ALS2 locus in one family.

CONCLUSIONS

The syndrome of IAHSP is genetically heterogeneous, and no clinical sign can help to distinguish patients with and without Alsin mutations.

Sleep and breathing in Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a genetic disorder, with hypotonia being the predominant feature in infancy, and developmental delay, obesity, and behavioral problems becoming more prominent in childhood and adolescence. Children with this disorder frequently suffer from excessive daytime sleepiness and have a primary abnormality of the circadian rhythm of rapid eye movement sleep. They also have primary abnormal ventilatory responses to hypoxia and hypercapnia, and these abnormalities may be exacerbated by obesity. Children with PWS are at risk of a variety of abnormalities of breathing during sleep, including obstructive sleep apnea and sleep-related alveolar hypoventilation. Clinical evaluation should include a careful history of sleep-related symptoms and assessment of the upper airway and lung function. Polysomnography should be considered for those with symptoms suggestive of sleep-disordered breathing. Treatment options depend on the underlying problem, but may include behavioral interventions, weight control, adenotonsillectomy, and nocturnal ventilation.

Novel locus for autosomal dominant pure hereditary spastic paraplegia (SPG19) maps to chromosome 9q33-q34

Hereditary spastic paraplegia is a clinically and genetically heterogeneous disorder characterized by progressive spasticity of the lower limbs. Seven loci for autosomal dominant pure hereditary spastic paraplegia (ADPHSP) have already been mapped on chromosomes 14q, 2p, 15q, 8p, 12q, 19q, and 2q. We report on an Italian family affected by ADPHSP for which we excluded linkage with the known loci and performed a genome-wide search. Linkage analysis and haplotype construction permitted the identification of a novel ADPHSP locus on the long arm of chromosome 9, designated SPG19. The phenotype was characterized by late onset (range, 36-55 years) and mild disability, with only 1 patient bound to a wheelchair after 31 years of disease. Urinary disturbances (urgency and/or incontinence) were always present, even in young patients with a short disease history.

Mitochondria and degenerative disorders

In mammalian cells, mitochondria provide energy from aerobic metabolism. They play an important regulatory role in apoptosis, produce and detoxify free radicals, and serve as a cellular calcium buffer. Neurodegenerative disorders involving mitochondria can be divided into those caused by oxidative phosphorylation (OXPHOS) abnormalities either due to mitochondrial DNA (mtDNA) abnormalities, e.g., chronic external ophthalmoplegia, or due to nuclear mutations of OXPHOS proteins, e.g., complex I and II associated with Leigh syndrome. There are diseases caused by nuclear genes encoding non-OXPHOS mitochondrial proteins, such as frataxin in Friedreich ataxia (which is likely to play an important role in mitochondrial-cytosolic iron cycling), paraplegin (possibly a mitochondrial ATP-dependent zinc metalloprotease of the AAA-ATPases in hereditary spastic paraparesis), and possibly Wilson disease protein (an abnormal copper transporting ATP-dependent P-type ATPase associated with Wilson disease). Huntingon disease is an example of diseases with OXPHOS defects associated with mutations of nuclear genes encoding non-mitochondrial proteins such as huntingtin. There are also disorders with evidence of mitochondrial involvement that cannot as yet be assigned. These include Parkinson disease (where a complex I defect is described and free radicals are generated from dopamine metabolism), amyotrophic lateral sclerosis, and Alzheimer disease, where there is evidence to suggest mitochondrial involvement perhaps secondary to other abnormalities.

Genome organization, function, and imprinting in Prader-Willi and Angelman syndromes

The chromosomal region, 15q11-q13, involved in Prader-Willi and Angelman syndromes (PWS and AS) represents a paradigm for understanding the relationships between genome structure, epigenetics, evolution, and function. The PWS/AS region is conserved in organization and function with the homologous mouse chromosome 7C region. However, the primate 4 Mb PWS/AS region is bounded by duplicons derived from an ancestral HERC2 gene and other sequences that may predispose to chromosome rearrangements. Within a 2 Mb imprinted domain, gene function depends on parental origin. Genetic evidence suggests that PWS arises from functional loss of several paternally expressed genes, including those that function as RNAs, and that AS results from loss of maternal UBE3A brain-specific expression. Imprinted expression is coordinately controlled in cis by an imprinting center (IC), a genetic element functional in germline and/or early postzygotic development that regulates the establishment of parental specific allelic differences in replication timing, DNA methylation, and chromatin structure.

Recent advances in hereditary spastic paraplegia

The hereditary spastic paraplegias are a group of rare disorders that are characterized by great clinical and genetic heterogeneity. There has been an exponential increase in the number of HSP loci mapped in recent years, with nine out of the 17 loci reported during the past 2 years. Eight loci have now been identified for the autosomal-dominant form, and seven of these are associated with pure HSP. Spastic paraplegia-4 remains the most frequent locus, and is usually associated with a pure phenotype. Although the corresponding spastin gene was only recently identified, over 50 mutations have been described to date, which renders molecular diagnosis difficult. Five loci are known for autosomal-recessive HSP, and four of these are associated with complex forms, all with different phenotypes. Two genes have been identified: paraplegin and sacsin. Finally, three loci have been identified in X-linked HSP, two of which are complex forms. The genes that encode L1 and PLP were the first to be identified in HSP disorders. Surprisingly, the five genes encode proteins of different families, making understanding and diagnosis of HSP even more difficult. The discovery of new genes should hopefully help to clarify the pathophysiology of these disorders.

Silver syndrome is not linked to any of the previously established autosomal dominant hereditary spastic paraplegia loci

The hereditary spastic paraplegias are a clinically variable and genetically heterogeneous group of disorders characterized by progressive and lower limb spasticity and weakness. Silver syndrome (SS) is a particularly disabling autosomal dominant form of the disease in which there is associated wasting of the hand muscles. In view of the fact that genes for hereditary spastic paraplegia can produce highly variable phenotypes, the eight known autosomal dominant loci were investigated for linkage to Silver syndrome. Genotyping of these loci in two large multigenerational families was incompatible with linkage to any of these regions, suggesting that an additional locus is responsible for this syndrome.

Increased intracortical facilitation in patients with autosomal dominant pure spastic paraplegia linked to chromosome 2p

There are at least seven clinically indistinguishable but genetically different types of autosomal dominant pure spastic paraplegia (ADPSP). In this study we investigated electrophysiological characteristics in patients with ADPSP linked to chromosome 2p (SPG4). Twelve patients from six different families with ADPSP linked to chromosome 2p and 15 control persons were included. Electromyography (EMG), motor and sensory nerve conduction, and motor evoked potentials using single and paired transcranial magnetic stimulation (PTMS) was performed. From the peripheral nervous system we found signs of motor and sensory axonal neuropathy. Motor evoked potentials disclosed greatly reduced corticospinal tract conduction velocity and amplitude of evoked potentials to the lower extremities indicating that the very marked spasticity predominantly seems to rely on dysfunction of the fast conducting axons of the pyramidal tract. PTMS showed an increased intracortical facilitation (ICF), which may reflect an impaired function of gamma-aminobutyric acid (GABA)-controlled interneuronal circuits in the motor cortex, alternatively an increased glutamatergic transmission or a compensatory recruitment of a larger number of neurones with corticospinal projections.

Prader-Willi and Angelman syndromes: sister imprinted disorders

Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are clinically distinct complex disorders mapped to chromosome 15q11-q13. They both have characteristic neurologic, developmental, and behavioral phenotypes plus other structural and functional abnormalities. However, the cognitive and neurologic impairment is more severe in AS, including seizures and ataxia. The behavioral and endocrine disorders are more severe in PWS, including obsessive-compulsive symptoms and hypothalamic insufficiency. Both disorders can result from microdeletion, uniparental disomy, or an imprinting center defect in 15q11-q13, although the abnormality is on the paternally derived chromosome 15 for PWS and the maternally derived 15 for AS because of genomic imprinting. Although the same gene may control imprinting for both disorders, the gene(s) causing their phenotypes differ. AS results from underexpression of a single gene, UBE3A, which codes for E6-AP, a protein that functions to transfer small ubiquitin molecules to certain target proteins, to enable their degradation. The genes responsible for PWS are not determined, although several maternally imprinted genes in 15q11-q13 are known. The most likely candidate is SNRPN, which codes for a small nuclear ribonucleoprotein, a ribosome-associated protein that controls gene splicing and thus synthesis of critical proteins in the brain. Animal models exist for both disorders. The genetic relationship between PWS and AS makes them unique and potentially highly instructive disorders that contribute substantially to the population burden of cognitive impairment.

Clinical and pathologic findings in hereditary spastic paraparesis with spastin mutation

OBJECTIVE

To describe a family with chromosome 2p-linked hereditary spastic paraparesis (HSP) associated with dementia and illustrate the cerebral pathology associated with this disorder.

BACKGROUND

HSP comprises a heterogeneous group of inherited disorders in which the main clinical feature is severe, progressive lower limb spasticity. Nongenetic classification relies on characteristics such as mode of inheritance, age at onset, and the presence or absence of additional neurologic features. Several loci have been identified for autosomal dominant pure HSP. The most common form, which links to chromosome 2p (SPG4), has recently been shown to be due to mutations in spastin, the gene encoding a novel AAA-containing protein.

RESULTS

The authors report four generations of a British family with autosomal dominant HSP in whom haplotype analysis indicates linkage to chromosome 2p. In addition, a missense mutation has been identified in exon 10 of the spastin gene (A1395G). Dementia was documented clinically in one member of the family, two other affected family members were reported to have had late onset memory loss, and a younger affected individual showed evidence of memory disturbance and learning difficulties. Autopsy of the demented patient confirmed changes in the spinal cord typical of HSP and also demonstrated specific cortical pathology. There was neuronal depletion and tau-immunoreactive neurofibrillary tangles in the hippocampus and tau-immunoreactive balloon cells were seen in the limbic and neocortex. The substantia nigra showed Lewy body formation. The pathologic findings are not typical of known tauopathies.

CONCLUSIONS

The authors confirm that chromosome 2p-linked HSP can be associated with dementia and that this phenotype may be associated with a specific and unusual cortical pathology.

Brazilian family with pure autosomal dominant spastic paraplegia maps to 8q: analysis of muscle beta 1 syntrophin

The autosomal dominant hereditary spastic paraplegias (AD-HSP) are a heterogeneous group of degenerative disorders of the central motor system, characterized by progressive spasticity of the lower limbs. Five loci for pure AD-HSP have been identified to date: SPG3 at 14q, SPG4 at 2p, SPG6 at 15q, SPG8 at 8q, and more recently SPG10 at 12q. We have analyzed a Brazilian family with 16 affected individuals by pure AD-HSP who developed progressive gait disturbance with onset at age 18-26 years. Linkage analysis performed with 13 relatives (6 affected and 7 normal) excluded SPG3, SPG4, and SPG6 as candidate regions. However, positive LOD scores were obtained with markers flanking the candidate region for the SPG8 locus [maximum two point Lod score (Zmax) = 3.3 at theta = 0 for D8S1804]. In this region lies the syntrophin beta 1 gene (SNT2B1), a widely expressed dystrophin-associated protein and therefore a good positional and functional candidate for this disease. Immunohistochemical and Western Blot (WB) studies showed that the distribution, expression, and apparent molecular weight of the beta 1 syntrophin protein were comparable to those of normal control individuals. Therefore, it is unlikely that defects in this protein are related to SPG8, at least in the present family.

Spastin, a new AAA protein, is altered in the most frequent form of autosomal dominant spastic paraplegia

Autosomal dominant hereditary spastic paraplegia (AD-HSP) is a genetically heterogeneous neurodegenerative disorder characterized by progressive spasticity of the lower limbs. Among the four loci causing AD-HSP identified so far, the SPG4 locus at chromosome 2p2-1p22 has been shown to account for 40-50% of all AD-HSP families. Using a positional cloning strategy based on obtaining sequence of the entire SPG4 interval, we identified a candidate gene encoding a new member of the AAA protein family, which we named spastin. Sequence analysis of this gene in seven SPG4-linked pedigrees revealed several DNA modifications, including missense, nonsense and splice-site mutations. Both SPG4 and its mouse orthologue were shown to be expressed early and ubiquitously in fetal and adult tissues. The sequence homologies and putative subcellular localization of spastin suggest that this ATPase is involved in the assembly or function of nuclear protein complexes.

Sleep and behaviour disturbance in Prader-Willi syndrome: a questionnaire study

The present authors describe sleep problems, including sleep apnoea and excessive daytime sleepiness (EDS), in subjects with Prader-Willi syndrome (PWS). The present paper reports a questionnaire study regarding sleep and behaviour in a group of 29 subjects with PWS, compared with an age- and gender-matched control group. Those with PWS suffered from sleep problems more frequently than the control subjects. Problems included EDS, snoring and early waking. Sleep problems in PWS were not associated with body mass index or weight. Excessive daytime sleepiness was a distinctive feature of the group with PWS, and behavioural disturbance in PWS children and adolescents was associated with EDS. Excessive daytime sleepiness seems to be characteristic of PWS, and may be related to problems with the sleep-wake cycle and hypothalamic dysfunction.

Mitochondrial involvement in Parkinson's disease, Huntington's disease, hereditary spastic paraplegia and Friedreich's ataxia

Respiratory chain dysfunction has been identified in several neurodegenerative disorders. In Friedreich's ataxia (FA) and Huntington's disease (HD), where the respective mutations are in nuclear genes encoding non-respiratory chain mitochondrial proteins, the defects in oxidative phosphorylation are clearly secondary. In Parkinson's disease (PD) the situation is less clear, with some evidence for a primary role of mitochondrial DNA in at least a proportion of patients. The pattern of the respiratory chain defect may provide some clue to its cause; in PD there appears to be a selective complex I deficiency; in HD and FA the deficiencies are most severe in complex II/III with a less severe defect in complex IV. Aconitase activity in HD and FA is severely decreased in brain and muscle, respectively, but appears to be normal in PD brain. Free radical generation is thought to be of importance in both HD and FA, via excitotoxicity in HD and abnormal iron handling in FA. The oxidative damage observed in PD may be secondary to the mitochondrial defect. Whatever the cause(s) and sequence of events, respiratory chain deficiencies appear to play an important role in the pathogenesis of neurodegeneration. The mitochondrial abnormalities induced may converge on the function of the mitochondrion in apoptosis. This mode of cell death is thought to play an important role in neurodegenerative diseases and it is tempting to speculate that the observed mitochondrial defects in PD, HD and FA result directly in apoptotic cell death, or in the lowering of a cell's threshold to undergo apoptosis. Clarifying the role of mitochondria in pathogenesis may provide opportunities for the development of treatments designed to reverse or prevent neurodegeneration.

Radiofrequency volumetric tissue reduction of the palate in subjects with sleep-disordered breathing

STUDY OBJECTIVES

To evaluate pain, swallowing, speech, edematous response, tissue shrinkage, sleep, snoring, and safety (energy limits and adverse effects) following radiofrequency (RF) treatment to the palate in 22 subjects with sleep-disordered breathing.

DESIGN

This investigation is a prospective nonrandomized study. Polysomnography, radiographic imaging, and infrared thermography, along with questionnaires and visual analog scales, were used to evaluate the effects of RF treatment to the palate.

SETTING

Treatments were delivered on an outpatient basis at Stanford University Medical Center.

PATIENTS

Twenty-two healthy patients (18 men), with a mean age of 45.3+/-9.1 years, were enrolled. All were snorers seeking treatment and met predetermined criteria: a respiratory disturbance index < or = 15, oxygen saturation > or = 85%, and a complaint of daytime sleepiness.

INTERVENTION

RF was delivered to the submucosa of the palate with a custom-fabricated electrode for a mean duration of 141+/-30 s with a mean of 3.6+/-1.2 treatments per patient. Reduction of their snoring scores determined the end point of the study.

RESULTS

Neither speech nor swallowing was adversely affected. Pain was of short duration (0 to 48 h) and was controlled with acetaminophen. There were no infections. Although there was documented edema at 24 to 48 h, there were no clinical airway compromises. Polysomnographic data showed improvement in esophageal pressure measurements of the mean nadir and the 95th percentile nadir (p=0.031, p=0.001) respectively, as well as the mean sleep efficiency index (p=0.002). Radiographic imaging showed a mean shrinkage of 5.5+/-3.7 mm (p< or =0.0001). Subjective snoring scores fell by a mean of 77% (8.3+/-1.8 to 1.9+/-1.7, p=0.0001) accompanied by improved mean Epworth sleepiness scores (8.5+/-4.4 to 5.2+/-3.3, p=0.0001).

CONCLUSION

The results of this investigation allowed the formulation of safety parameters for RF in this defined population with mild sleep-disordered breathing. There was a documented tissue reduction and improvement in symptoms in all subjects. However, given the small sample size and short-term follow-up, these results should be confirmed by further investigation.

Prader-Willi and Angelman syndromes. Disorders of genomic imprinting

Prader-Willi and Angelman syndromes are 2 clinically distinct disorders associated with multiple anomalies and mental retardation. They are only discussed together because they share a similar and uncommon genetic basis: they involve genes that are located in the same region in the genome and are characterized by genetic imprinting. This normal process has contributed to these 2 complex and severe conditions through inactivation of 1 copy of the genes relevant to each disorder: the maternally derived copy of genes for Prader-Willi syndrome in proximal 15q are normally silent, and a paternally derived copy of 1 gene for Angelman syndrome in 15q is normally silent. For both disorders, when the normally active copy of the gene or genes is missing, abnormality results. Since the genes for these 2 disorders are located very close together, and since the center involved in inactivating the genes involved in imprinting may be the same, both these disorders usually result from the same chromosomal deletion; which disorder results depends on the parent of origin of the chromosome 15 that becomes deleted. Both Prader-Willi and Angelman syndrome can also occur as a result of having both members of the chromosome 15 pair derived from 1 parent, a condition known as uniparental disomy. Both can also result from a structural abnormality of the imprinting center, known as an imprinting mutation. In addition, Angelman syndrome can be caused by a mutation in the gene that causes it; a comparable cause is not present in Prader-Willi syndrome since it results from abnormality in more than 1 gene. Finally, despite the complexity of possible causes, all but the single gene mutation of the Angelman syndrome gene can be detected through methylation-sensitive DNA probes, since DNA methylation is the process by which the genes for these 2 disorders are imprinted. This unusual property of specific areas of the DNA holds promise for future treatment of these and other disorders related to imprinting through reversal of the imprinting process.

Prader-Willi syndrome

Prader-Willi syndrome is a complex disorder affecting multiple systems with many manifestations relating to hypothalamic insufficiency. Major findings include infantile hypotonia, developmental delay and mental retardation, behaviour disorder, characteristic facial appearance, obesity, hypogonadism, and short stature. Obesity and the behavioural problems are the major causes of morbidity and mortality. Prader-Willi syndrome is caused by abnormalities of the imprinted region of proximal 15q and results from absence of the normally active paternal genes in this region. Such absence results from paternal interstitial deletion, maternal uniparental disomy, or a mutation or other abnormality in the imprinting process. Diagnostic identification of all causes has become available in recent years, permitting early detection and institution of appropriate management. This testing has permitted recent identification of some phenotypic differences among affected subjects of different race and between those with deletions and uniparental disomy as a cause.

A family with hereditary spastic paraparesis and epilepsy

PURPOSE

We describe a family with hereditary spastic paraparesis (HSP) in which 4 of 6 affected members also have epilepsy.

METHODS

All family members were examined by 2 neurologists. Four affected and 3 unaffected family members had EEG recordings. Four affected members were investigated for other causes of spastic paraparesis and epilepsy.

RESULTS

Epileptic symptoms varied among family members: 1 had complex partial seizures, another had focal myoclonic epilepsy, and 2 had simple partial seizures secondarily generalized. All 4 had clinical or EEG evidence to support a focal origin for the epilepsy, and 2 had photoparoxysal responses on EEG. Symptoms were more severe and occurred earlier in the younger generation, suggesting genetic anticipation in this family. The onset of epilepsy developed simultaneously with, or < or = 18 years before, onset of gait disturbance. Three unaffected family members had normal EEGs.

CONCLUSIONS

The association of HSP and epilepsy should no longer be assumed to be fortuitous.

Familial spastic paraparesis: evaluation of locus heterogeneity, anticipation, and haplotype mapping of the SPG4 locus on the short arm of chromosome 2

Familial spastic paraparesis (SPG) is a clinically and genetically heterogeneous group of disorders. At least three loci have been implicated in autosomal dominant pure SPG and mutations in either of two loci may cause the X-linked form. Although the penetrance is high for all forms by age 60, there is wide variation in clinical characteristics, including age of onset. Two-point and multi-point linkage analyses in nine families provided supportive evidence that the most common form of SPG is linked to chromosome 2 (SPG4). Haplotype analysis localized the critical region to a 6 cM interval between D2S392 and D2S367. By haplotype analysis, the disease in at least one family does not appear to be linked to any of the presently known SPG loci, suggesting that there is at least one additional SPG gene. Evaluation at ages of onset in 11 families gave suggestive evidence for anticipation with mean age of onset in parents (41.3 years) being older than mean age of onset in children (26.9 years; P < 0.005).

Extensive genetic heterogeneity in the "pure" form of autosomal dominant familial spastic paraplegia (Strümpell's disease)

Three dominantly inherited "pure" form of familial spastic paraplegia (FSP) genes have been genetically mapped to regions of chromosomes, yet no specific genes or mutations have been identified (FSP1; chromosome 14q, FSP2; chromosome 2p and FSP3; chromosome 15q). We studied a "pure" form of autosomal dominant FSP family from North American of Italian descent for linkage to three dominant FSP loci. We excluded all three known loci with markers (D14S288, D14S269, D14S281, D2S352, D2S367, D15S210, D15S122, and D15S156) in our "pure" dominant FSP family. Our result suggests that dominant FSP is very genetically heterogeneous, and the existence of at least a fourth locus (FSP4) for the pure form of autosomal dominant FSP (Strümpell's disease).