Fatal infantile encephalopathy with olivopontocerebellar hypoplasia and micrencephaly. Report of three siblings

The PARN, TOE1, and USB1 RNA deadenylases and their roles in non-coding RNA regulation

The levels of non-coding RNAs (ncRNAs) are regulated by transcription, RNA processing, and RNA degradation pathways. One mechanism for the degradation of ncRNAs involves the addition of oligo(A) tails by non-canonical poly(A) polymerases, which then recruit processive sequence-independent 3' to 5' exonucleases for RNA degradation. This pathway of decay is also regulated by three 3' to 5' exoribonucleases, USB1, PARN, and TOE1, which remove oligo(A) tails and thereby can protect ncRNAs from decay in a manner analogous to the deubiquitination of proteins. Loss-of-function mutations in these genes lead to premature degradation of some ncRNAs and lead to specific human diseases such as Poikiloderma with Neutropenia (PN) for USB1, Dyskeratosis Congenita (DC) for PARN and Pontocerebellar Hypoplasia type 7 (PCH7) for TOE1. Herein, we review the biochemical properties of USB1, PARN, and TOE1, how they modulate ncRNA levels, and their roles in human diseases.

TSEN54 missense variant in Standard Schnauzers with leukodystrophy

We report a hereditary leukodystrophy in Standard Schnauzer puppies. Clinical signs occurred shortly after birth or started at an age of under 4 weeks and included apathy, dysphoric vocalization, hypermetric ataxia, intension tremor, head tilt, circling, proprioceptive deficits, seizures and ventral strabismus consistent with a diffuse intracranial lesion. Magnetic resonance imaging revealed a diffuse white matter disease without mass effect. Macroscopically, the cerebral white matter showed a gelatinous texture in the centrum semiovale. A mild hydrocephalus internus was noted. Histopathologically, a severe multifocal reduction of myelin formation and moderate diffuse edema without inflammation was detected leading to the diagnosis of leukodystrophy. Combined linkage analysis and homozygosity mapping in two related families delineated critical intervals of approximately 29 Mb. The comparison of whole genome sequence data of one affected Standard Schnauzer to 221 control genomes revealed a single private homozygous protein changing variant in the critical intervals, TSEN54:c.371G>A or p.(Gly124Asp). TSEN54 encodes the tRNA splicing endonuclease subunit 54. In humans, several variants in TSEN54 were reported to cause different types of pontocerebellar hypoplasia. The genotypes at the c.371G>A variant were perfectly associated with the leukodystrophy phenotype in 12 affected Standard Schnauzers and almost 1000 control dogs from different breeds. These results suggest that TSEN54:c.371G>A causes the leukodystrophy. The identification of a candidate causative variant enables genetic testing so that the unintentional breeding of affected Standard Schnauzers can be avoided in the future. Our findings extend the known genotype-phenotype correlation for TSEN54 variants.

Various hereditary diseases of the cerebral white matter occur in humans and dogs. We describe a new leukodystrophy in Standard Schnauzers. Genetic mapping and whole genome sequence analysis identified a likely candidate causative variant in the TSEN54 gene encoding tRNA splicing endonuclease 54. These results provide new information about the role of TSEN54 in cell metabolism and the development of the central nervous system in the late gestational and early post-natal period. The affected dogs potentially represent a translational large animal model for similar leukoencephalopathies in human medicine. The clinical phenotype in Schnauzers included multifocal central nervous system signs. A holistic pathogenically driven understanding of disease initiation and perpetuation requires a solid analysis of the underlying genetics and characterization of the disease phenotype at the clinical and cellular as well as sub-cellular level. In contrast to the canine phenotype with a predominant manifestation in the cerebrum white matter, other TSEN54 variants in humans have been reported to result in a different pathological phenotype characterized by pontocerebellar hypoplasia. The differences between humans and dogs underscore the need for comparative analysis at the clinical, pathological and molecular level to understand species-specific protein mediated pathways, interactions and outcomes.

What's new in pontocerebellar hypoplasia? An update on genes and subtypes

Background

Pontocerebellar hypoplasia (PCH) describes a rare, heterogeneous group of neurodegenerative disorders mainly with a prenatal onset. Patients have severe hypoplasia or atrophy of cerebellum and pons, with variable involvement of supratentorial structures, motor and cognitive impairments. Based on distinct clinical features and genetic causes, current classification comprises 11 types of PCH.

Main text

In this review we describe the clinical, neuroradiological and genetic characteristics of the different PCH subtypes, summarize the differential diagnosis and reflect on potential disease mechanisms in PCH. Seventeen PCH-related genes are now listed in the OMIM database, most of them have a function in RNA processing or translation. It is unknown why defects in these apparently ubiquitous processes result in a brain-specific phenotype.

Conclusions

Many new PCH related genes and phenotypes have been described due to the appliance of next generation sequencing techniques. By including such a broad range of phenotypes, including non-degenerative and postnatal onset disorders, the current classification gives rise to confusion. Despite the discovery of new pathways involved in PCH, treatment is still symptomatic. However, correct diagnosis of PCH is important to provide suitable care and counseling regarding prognosis, and offer appropriate (prenatal) genetic testing to families.

Microcephaly, dysmorphic features, corneal dystrophy, hairy nipples, underdeveloped labioscrotal folds, and small cerebellum in four patients

Pontocerebellar hypoplasia (PCH) can occur as an isolated entity or part of a syndrome. PCH has been reported with facial dysmorphism, ocular anomalies, and genital anomalies, but the co-occurrence of all four has not been previously described. We report on four patients, born to two consanguineous families that are not related to one another, with distinctive facial features (short forehead, laterally extended, medially flared eyebrows), corneal dystrophy, underdevelopment of labioscrotal folds, and nonprogressive PCH. In addition, the patients show hair extruding from the lactiferous ducts, which to our knowledge has not been described before. The parental consanguinity, affected siblings of both genders, and absent manifestations in parents, indicate an autosomal recessive pattern of inheritance as most likely. © 2016 Wiley Periodicals, Inc.

Clinical and neuroimaging features as diagnostic guides in neonatal neurology diseases with cerebellar involvement

Cerebellar abnormalities are encountered in a high number of neurological diseases that present in the neonatal period. These disorders can be categorized broadly as inherited (e.g. malformations, inborn errors of metabolism) or acquired (e.g. hemorrhages, infections, stroke). In some disorders such as Dandy-Walker malformation or Joubert syndrome, the main abnormalities are located within the cerebellum and brainstem. In other disorders such as Krabbe disease or sulfite oxidase deficiency, the main abnormalities are found within the supratentorial brain, but the cerebellar involvement may be helpful for diagnostic purposes. In In this article, we review neurological disorders with onset in the neonatal period and cerebellar involvement with a focus on how characterization of cerebellar involvement can facilitate accurate diagnosis and improved accuracy of neuro-functional prognosis.

Pontocerebellar hypoplasia

Pontocerebellar hypoplasia (PCH) is a clinically and genetically heterogeneous group of autosomal recessively inherited neurodevelopmental disorders. Following the rapidly increasing number of genes identified in different subtypes, the clinical spectrum has been broadened to completely different neurological phenotypes. In this review we will address the clinical picture, neuroradiological, pathoanatomic, and genetic findings in the currently known PCH subtypes.

Pontocerebellar hypoplasia type 3 with tetralogy of Fallot

We report a male infant with pontocerebellar hypoplasia type 3 and tetralogy of Fallot. He showed optic nerve atrophy, progressive microcephaly, severe psychomotor developmental delay, and vesicoureteral reflux. Magnetic resonance imaging revealed severe hypoplasia of the cerebellar vermis and hemisphere, and of the brainstem including the pons, and simplified gyral patterns in bilateral frontal lobes. An unknown etiology differing from other cases of PCH type 3 might have caused not only optic nerve atrophy and hypoplasia of the cerebellum and brainstem, but also cerebral and visceral malformations. To the best of our knowledge, this represents the first report of pontocerebellar hypoplasia with congenital cardiac malformation.

Classification, diagnosis and potential mechanisms in pontocerebellar hypoplasia

Pontocerebellar Hypoplasia (PCH) is group of very rare, inherited progressive neurodegenerative disorders with prenatal onset. Up to now seven different subtypes have been reported (PCH1-7). The incidence of each subtype is unknown. All subtypes share common characteristics, including hypoplasia/atrophy of cerebellum and pons, progressive microcephaly, and variable cerebral involvement. Patients have severe cognitive and motor handicaps and seizures are often reported. Treatment is only symptomatic and prognosis is poor, as most patients die during infancy or childhood. The genetic basis of different subtypes has been elucidated, which makes prenatal testing possible in families with mutations. Mutations in three tRNA splicing endonuclease subunit genes were found to be responsible for PCH2, PCH4 and PCH5. Mutations in the nuclear encoded mitochondrial arginyl- tRNA synthetase gene underlie PCH6. The tRNA splicing endonuclease, the mitochondrial arginyl- tRNA synthetase and the vaccinia related kinase1 are mutated in the minority of PCH1 cases. These genes are involved in essential processes in protein synthesis in general and tRNA processing in particular. In this review we describe the neuroradiological, neuropathological, clinical and genetic features of the different PCH subtypes and we report on in vitro and in vivo studies on the tRNA splicing endonuclease and mitochondrial arginyl-tRNA synthetase and discuss their relation to pontocerebellar hypoplasia.

Early pontocerebellar hypoplasia with vanishing testes: A new syndrome?

We report on a full-term male infant with hypoplastic male genitalia and bilateral impalpable testes noted at birth, who over the following months developed increasing hypotonia, apneic episodes, and seizures resulting in his death at age 24 weeks. During this period regression of penile corporeal tissue was observed. An endocrinological diagnosis of primary hypogonadism was made and cerebral imaging at 19 weeks showed reduced periventricular white matter with marked pontocerebellar hypoplasia (PCH)/atrophy, but a well-developed posterior fossa. We propose that this condition constitutes a new form of severe PCH/atrophy with testicular regression that has onset in the fetal period.

TSEN54 mutations cause pontocerebellar hypoplasia type 5

Pontocerebellar hypoplasia (PCH) is a group of autosomal recessive neurodegenerative disorders characterized by prenatal onset of stunted brain growth and progressive atrophy predominantly affecting cerebellum, pons and olivary nuclei, and to a lesser extent also the cerebral cortex. Six subtypes (PCH1-6) were described and genes for four types (PCH1, 2, 4 and 6) were identified. Mutations in the tRNA splicing endonuclease subunit (TSEN) genes 54, 2 and 34 are found in PCH2 and PCH4. One family with severe prenatal onset of PCH has been the only representative of PCH5 published so far, and the molecular genetic status of PCH5 has not been ascertained until now. We screened the previously reported PCH5 family for mutations in the TSEN54 gene. The PCH5 patient was found to be the result of compound heterozygosity for the common TSEN54 mutation (p.A307S) plus a novel splice site mutation. The mutations associated with PCH5 are similar to what has been reported in PCH4. Thus, PCH5, PCH4 and PCH2 represent a spectrum of clinical manifestations caused by different mutations in the TSEN genes. We, therefore, propose to classify PCH2, PCH4 and PCH5 as TSEN mutation spectrum disorders.

Pontocerebellar hypoplasia type 3 with severe vitamin A deficiency

Pontocerebellar hypoplasia consists of a rare heterogeneous group of congenital neurodevelopmental disorders. It is characterized by hypoplasia and atrophy of the cerebellar cortex, dentate nuclei, pontine nuclei, and inferior olives. We present an 18-month-old infant with pontocerebellar hypoplasia type 3 and severe vitamin A deficiency. This case emphasizes the significance of vitamin A in the proper formation of the hindbrain. The authors conclude that vitamin A screening should be considered in maternal and newborn metabolic screening.

Clinical, neuroradiological and genetic findings in pontocerebellar hypoplasia

Pontocerebellar hypoplasia is a group of autosomal recessive neurodegenerative disorders with prenatal onset. The common characteristics are cerebellar hypoplasia with variable atrophy of the cerebellum and the ventral pons. Supratentorial involvement is reflected by variable neocortical atrophy, ventriculomegaly and microcephaly. Mutations in the transfer RNA splicing endonuclease subunit genes (TSEN54, TSEN2, TSEN34) were found to be associated with pontocerebellar hypoplasia types 2 and 4. Mutations in the mitochondrial transfer RNA arginyl synthetase gene (RARS2) were associated with pontocerebellar hypoplasia type 6. We studied a cohort of 169 patients from 141 families for mutations in these genes, of whom 106 patients tested positive for mutations in one of the TSEN genes or the RARS2 gene. In order to delineate the neuroradiological and clinical phenotype of patients with mutations in these genes, we compared this group with 63 patients suspected of pontocerebellar hypoplasia who were negative on mutation analysis. We found a strong correlation (P < 0.0005) between TSEN54 mutations and a dragonfly-like cerebellar pattern on magnetic resonance imaging, in which the cerebellar hemispheres are flat and severely reduced in size and the vermis is relatively spared. Mutations in TSEN54 are clinically associated with dyskinesia and/or dystonia and variable degrees of spasticity, in some cases with pure generalized spasticity. Nonsense or splice site mutations in TSEN54 are associated with a more severe phenotype of more perinatal symptoms, ventilator dependency and early death. In addition, we present ten new mutations in TSEN54, TSEN2 and RARS2. Furthermore, we show that pontocerebellar hypoplasia type 1 together with elevated cerebrospinal fluid lactate may be caused by RARS2 mutations.

Delayed gyration with pontocerebellar hypoplasia type 1

We report two sibling cases of pontocerebellar hypoplasia type 1 (PCH-1), which showed severe generalized hypotonia, psychomotor delay, and visual impairment. Magnetic resonance imaging in the neonatal period revealed delayed gyration compared to the postconceptional ages in both cases. The elder brother died with pneumonia at 10months of age, and the younger brother survived to over 6years of age. Repeated neuroimaging in the younger brother revealed improvement of the delayed gyration and progressive atrophy, not only in the pons and cerebellum, but also in the cerebrum. To the best of our knowledge, this is the first report of delayed gyration in PCH-1.

A developmental and genetic classification for midbrain-hindbrain malformations

Advances in neuroimaging, developmental biology and molecular genetics have increased the understanding of developmental disorders affecting the midbrain and hindbrain, both as isolated anomalies and as part of larger malformation syndromes. However, the understanding of these malformations and their relationships with other malformations, within the central nervous system and in the rest of the body, remains limited. A new classification system is proposed, based wherever possible, upon embryology and genetics. Proposed categories include: (i) malformations secondary to early anteroposterior and dorsoventral patterning defects, or to misspecification of mid-hindbrain germinal zones; (ii) malformations associated with later generalized developmental disorders that significantly affect the brainstem and cerebellum (and have a pathogenesis that is at least partly understood); (iii) localized brain malformations that significantly affect the brain stem and cerebellum (pathogenesis partly or largely understood, includes local proliferation, cell specification, migration and axonal guidance); and (iv) combined hypoplasia and atrophy of putative prenatal onset degenerative disorders. Pertinent embryology is discussed and the classification is justified. This classification will prove useful for both physicians who diagnose and treat patients with these disorders and for clinical scientists who wish to understand better the perturbations of developmental processes that produce them. Importantly, both the classification and its framework remain flexible enough to be easily modified when new embryologic processes are described or new malformations discovered.

Pena-Shokeir phenotype (fetal akinesia deformation sequence) revisited

BACKGROUND

Pena and Shokeir described the phenotype of two sisters in 1974, and subsequently their features have become recognized as a sequence of deformational changes related to decreased or absent fetal movement (fetal akinesia deformation sequence [FADS]), because of the work of Moessinger (1983).

METHODS

Identification of reported cases by searching Online Mendelian Inheritance in Man, Medlines, the London Dysmorphology Database, and the references found in these articles. These case reports were reviewed, tabulated, and summarized.

RESULTS

It is now possible to recognize at least 20 familial types of Pena-Shokeir phenotype (PSP), based on the differences found in the reports of the natural history and pathology found at fetal and newborn autopsy. In addition, characteristic changes in the central nervous system seen with embryonic/fetal vascular compromise have been recognized in many reported cases. Most of the reported cases of PSP/FADS related to vascular compromise are sporadic, but familial cases have also been reported.

CONCLUSION

Lack of fetal movement (fetal akinesia) in humans produces a recognizable sequence of deformations. Many developmental processes must be accomplished for fetal movement to be normal, and for extra-uterine life to be sustainable. Prenatal diagnosis is possible through real-time ultrasound studies as early as 12 weeks. Most reported cases die in utero, at birth, or in the newborn period. Advances in embryo/fetus pathology have led to the recognition of the many familial subtypes, allowing improved genetic counseling and early recognition in subsequent pregnancies.

tRNA splicing endonuclease mutations cause pontocerebellar hypoplasia

Pontocerebellar hypoplasias (PCH) represent a group of neurodegenerative autosomal recessive disorders with prenatal onset, atrophy or hypoplasia of the cerebellum, hypoplasia of the ventral pons, microcephaly, variable neocortical atrophy and severe mental and motor impairments. In two subtypes, PCH2 and PCH4, we identified mutations in three of the four different subunits of the tRNA-splicing endonuclease complex. Our findings point to RNA processing as a new basic cellular impairment in neurological disorders.

Congenital pontocerebellar atrophy and telencephalic defects in three siblings: a new subtype

We report three siblings, two of whom had a neuropathological study, with a new subtype of congenital ponto-cerebellar atrophy (PCH). In addition to the brain stem and cerebellar anomalies common to all types of this heterogeneous condition, there were unique developmental defects in the telencephalon: absence of the claustrum, diffuse cortical changes particularly in the insula and an extremely small brain. In an attempt to shed some light on the pathogenesis of this developmental disorder, we have analyzed the pattern of brain stem and cerebellar abnormalities in ours and in previously reported patients with PCH, to possibly distinguish primary from secondary effects of the mutant gene upon the cerebellar circuitry, and compared our patients' cerebellar and cerebral defects to those of some other human brain malformations and to mutant mice with both hindbrain and forebrain anomalies. Although this and previous observations of familial congenital PCH with apparent autosomal recessive inheritance spawn the endeavor to compare and classify patients into subgroups, any final classification must await identification and molecular characterization of the causal gene(s).

Pontocerebellar hypoplasia type 2: a neuropathological update

Pontocerebellar hypoplasia type 2 (PCH-2; MIM 277470), an autosomal recessive neurodegeneration with fetal onset, was studied in six autopsies with ages at death ranging between 1 and 22 years. Three patients were distantly related. A case of olivopontocerebellar hypoplasia (OPCH; MIM 225753) was studied for comparison. Typical findings are: short cerebellar folia with poor branching ("hypoplasia"), relative sparing of the vermis, sharply demarcated areas of full thickness loss of cerebellar cortex probably resulting from regression at an early stage of development, segmental loss of dentate nuclei with preserved islands and reactive changes, segmental loss in the inferior olivary nucleus with reactive changes, loss of ventral pontine nuclei with near absence of transverse pontine fibers and sparing of spinal anterior horn cells. Variable findings are: cystic cerebellar degeneration, found in two, with vascular changes limited to the cerebellum in one. Comparison to olivopontocerebellar hypoplasia (OPCH) strongly suggests a continuum of pathology between this disorder and PCH-2. Immunohistochemical evaluation of the endoplasmic reticulum stress response is negative. We conclude that the neuropathological findings in PCH-2 are sufficiently specific to enable an unequivocal diagnosis based on neuropathology.

Rhabdomyolysis in pontocerebellar hypoplasia type 2 (PCH-2)

Pontocerebellar hypoplasia type 2, an autosomal recessive neurodegeneration with prenatal onset, is characterised by progressive microcephaly and chorea/dystonia and has not previously been associated with muscular involvement. The gene associated with PCH-2 is unknown. An episode of rhabdomyolysis is reported in two non-related children with PCH-2, fatal in one, precipitated by intercurrent disease. Muscle biopsies in two other PCH-2 patients, and in one rhabdomyolysis patient whose biopsy antedated this complication showed areas of myofibrillar disruption or necrosis. Postmortem muscle sampled in another case without neuromuscular symptoms revealed focal necrosis, regenerating small fibres and upregulation of HLA-ABC. Random serum creatine kinase values in six other PCH-2 patients without clinical signs of neuromuscular involvement were increased in four. Collected data provide preliminary evidence of a subclinical myopathy associated with PCH-2.

Pontocerebellar hypoplasia type 2: variability in clinical and imaging findings

We report 24 children (14 girls) who presented with the typical neuroimaging findings of pontocerebellar hypoplasia (PCH) to describe the clinical spectrum of type 2. Twenty-one presented with the classical form described by Barth; characteristic features (15/21) were breathing and/or sucking problems during neonatal period and early onset hyperkinetic movement disorder. Eighteen were normocephalic at birth, but all developed microcephaly during infancy. Development was severely affected with none of the children being capable of sitting, walking, or talking. Social contact and visual fixation were persistently poor. Dyskinetic movement disorder was present in all, in some together with mild spasticity. Seizures occurred in 14 (in 7 as neonates). Eight children died (age 1 day-6 years). Neuroimaging showed an absent or severely flattened pons, different degrees of vermian hypoplasia, with cerebellar hemispheres (wing-like structures) being equally or more affected. Three (all girls) were less severely affected clinically and did not develop the dyskinetic movement disorder, motor and cognitive development were somewhat better. Microcephaly was also a prominent sign. Severity of pontocerebellar neuroimaging findings did not differentiate between the typical and atypical clinical group and did not correlate with clinical outcome.

Severe, fetal-onset form of olivopontocerebellar hypoplasia in three sibs: PCH type 5?

We present three siblings with a precise onset of fetal seizure-like activity who had severe olivopontocerebellar hypoplasia (OPCH) and degeneration. Autopsies at 20, 27, and 37 weeks gestation showed diffuse central nervous system volume loss that was most marked for the cerebellum and brain stem structures. Neuropathological abnormalities included dysplastic, C-shaped inferior olivary nuclei, absent or immature dentate nuclei, and cell paucity more marked for the cerebellar vermis than the hemispheres. Delayed development was seen in layer 2 of the cerebral cortex and in Purkinje cells of the cerebellum. Prenatal monitoring defined a developmental window of 16-18 weeks gestation when ultrasonic assessment of cerebellar width was used for prenatal diagnosis. We discuss our findings in the context of the differential diagnosis for infantile (O)PCH and propose a classification scheme for the pontocerebellar hypoplasias. These patients represent the earliest reported with OPCH and provide unique information regarding the developmental neuropathology of this condition.

Extended phenotype of pontocerebellar hypoplasia with infantile spinal muscular atrophy

Pontocerebellar hypoplasia (PCH) is rarely associated with anterior horn cell disease and designated as PCH-1. This phenotype is characterized by severe muscle weakness and hypotonia starting prenatally or at birth with a life span not exceeding a few months in most cases. Milder disease courses with later onset and longer survival are normally not diagnosed as PCH-1. We describe the clinical and neuroradiological findings in nine patients out of six siblingships with evidence of cerebellar defects and early onset spinal muscular atrophy (SMA), representing a broad spectrum of clinical variability. In all patients, the diagnosis of SMA (Werdnig-Hoffmann disease) was made on the basis of electrophysiological data and muscle biopsy; however, genetic testing failed to confirm the diagnosis of infantile SMA with a gene defect on chromosome 5q and resulted in clinical reevaluation. Age at onset was after a normal period in the first months of life in three siblingships and pre- and postnatally in the other three families. Life span was 2-4 years in patients with later onset, and age at death occurred after birth or within months in the more severe group. Two siblingships showed discordant ages at death despite similar treatment. In contrast to the previous definition of PCH-1, our observations suggest the existence of milder phenotypes with pontocerebellar hypoplasia or olivopontocerebellar atrophy in combination with anterior horn cell loss. A pontine involvement is not necessarily seen by neuroimaging methods. The genetic basis of PCH-1 remains to be determined. The gene locus for infantile SMA on chromosome 5q could be excluded by linkage studies. Parental consanguinity and affected siblings make autosomal recessive inheritance most likely.

Malformations of the posterior fossa: current perspectives

Posterior fossa malformations are a special group of central nervous system anomalies that present during infancy with hypotonia, developmental delay, microcephaly, or hydrocephalus. Recent discoveries of the genetic and epigenetic factors that control hindbrain ontogenesis explain some of these disturbances in cerebellar development. A comprehensive classification of posterior fossa malformations is proposed with particular attention to Dandy-Walker malformation, Joubert syndrome, and other cerebellar hypoplasias. A rare form of cerebellar hypertrophy which caused repeated obstruction at the foramen magnum is recognized. The importance of the cerebellum in language, cognition, and brain growth is stressed.

Fetal akinesia deformation sequence: a study of 30 consecutive in utero diagnoses

The etiology of the fetal akinesia deformation sequence (FADS) is heterogeneous and can be the result of neurogenic and myopathic disorders, restrictive dermopathy, teratogen exposure, and intrauterine constraint. We present the prenatal and fetopathological findings in a consecutive series of 30 affected fetuses with normal chromosomal results. According to the in utero time of onset of the fetal akinesia, the severity of the phenotype varied from a severe, generalized FADS in the early-onset group to milder defects, as isolated distal arthrogryposis in the late-onset group. No more than 10% (3/30) were diagnosed in the first trimester of pregnancy and all presented a severe phenotype. Twenty-seven of the thirty (90%) were diagnosed after the first trimester, with a severe FADS in 15/27 and a milder phenotype of distal arthrogryposis in 12/27. In all 30 patients, extensive neuropathological studies (brain, spinal cord, and muscles) were performed. In 16 patients (53%) a specific diagnosis could be made (central nervous system abnormalities 9/16; spinal cord 1/16; primary myopathy 3/16; syndromic 3/16). In 10 others (33%), pathological neuromuscular findings were present but no definitive diagnosis was established. In 4 patients (13%), neuromuscular findings were normal, and the etiology of the FADS remained unexplained.

Fatal outcome in a case of pontocerebellar hypoplasia type 2

Pontocerebellar hypoplasia (PCH) is a very rare congenital (autosomal recessive) condition with fetal onset. Only a few cases have been published on the basis of both clinical data (symptoms/neuroradiological imaging) and autopsy results. This paper reports on such a case involving a 1.5-year-old male infant. The child suffered from severe psychomotor delay, extrapyramidal dyskinesia and epileptic seizures, but did not exhibit signs of spinal muscular atrophy as related to PCH type 1. Magnetic resonance imaging (MRI) at the age of 6 months demonstrated olivo-pontine and bilateral cerebellar hypoplasia. The boy was unexpectedly found dead. Autopsy disclosed a severe aspiration of gastric contents as the final cause of death. The neuropathological examination confirmed PCH type 2 (according to Barth [Brain Dev., 15 (1993) 411-422]) with marked microcephaly and olivopontocerebellar hypoplasia. Histologically, decreased density of olivo-pontine neurons, reduction of granular and Purkinje's cell layers of the cerebellum, slight astroglial proliferation and fragmented appearance of the dentate nuclei were observed. The immunohistochemical expression pattern was determined using antibodies against glial fibrillary acidic protein, synaptophysin and neurofilament protein. Summarizing, typical features of PCH type 2 were present and proved by clinical course, MRI and autopsy. Despite severe symptoms due to a natural disease this rare neurogenetic entity can become of forensic interest, when sudden unexpected death occurs.

Prenatal diagnosis of fatal infantile olivopontocerebellar hypoplasia syndrome

We report the first case of prenatal diagnosis of fatal infantile olivopontocerebellar hypoplasia syndrome, OMIM 225753. Ultrasound findings noted at 28 weeks' gestation included polyhydramnios, a small stomach bubble, a small but morphologically normal cerebellum, dilatation of the fourth ventricle, and long periods of normal fetal movement punctuated by sudden bursts of violent seizure-like activity of the fetal extremities. At birth, the child was noted to be hypertonic, myoclonic, hyper-reflexic, demonstrated poor gastrointestinal motility, and had severe apneic episodes. Magnetic resonance imaging (MRI) demonstrated marked hypoplasia or atrophy of the cerebellum, pons and medulla, mild atrophy of the cerebral cortex, and mild ex vacuo venticulomegaly of the fourth, third and lateral ventricles. This child died from respiratory insufficiency at 14 days of age. The parents of this child had previously lost a child with similar clinical and anatomical findings. Prenatal sonographers should be aware of the existence of this rare syndrome and should look carefully at the size of the cerebellum in cases of polyhydramnios or when in utero 'seizure-like' activity is seen. The importance of establishing this diagnosis lies in the fact that it appears to have a very poor postnatal prognosis and is likely to be inherited as an autosomal recessive disease.

Three siblings of fatal infantile encephalopathy with olivopontocerebellar hypoplasia and microcephaly

We report three male siblings born with fatal encephalopathy comprising microcephaly, myoclonus and muscle hypertonia. All three patients died during infancy. Postmortem examination on the brain revealed that all infants had neuronal loss in the cerebellar cortex, inferior olivary and pontine nuclei, which were more pronounced in the older subject than the younger ones. In addition, they were associated with polymicrogyria in the cerebral cortex of the insula, olivary and dentate nuclear dysplasia, and a hypoplastic corticospinal tract. The clinical and neuropathological findings in our cases were identical to those in fatal infantile encephalopathy with olivopontocerebellar hypoplasia and microencephaly [Albrecht et al., Acta Neuropathol 1993;85:394-399], but an association of malformations suggests a new genetic factor in pathogenesis of olivopontocerebellar hypoplasia.

Non-progressive familial congenital cerebellar hypoplasia

A syndrome is reported of congenital non-progressive, gradually slightly improving, ataxia in 3 out of 5 male sibs, issues of a first-order consanguineous mating. Additional characteristic features included: moderate microcephaly, generalised muscle weakness and hypotonia, nystagmus, and moderate mental retardation. A pyramidal syndrome of hyperreflexia and Babinski signs, without any spasticity, became manifest in the 2nd or 3rd year of life. In all three, the caudal part of the vermis was absent, the enlarged IVth ventricle opening up via Magendie's foramen into the cisterna magna. The middle and rostral vermian parts as well as the sagittal paravermian parts of the cerebellar hemispheres were hypoplastic. The differential diagnosis of this syndrome is analysed and the developmental pathogenetic mechanisms likely to produce the typifying distribution of aplasia are indicated.

Pontocerebellar hypoplasias. An overview of a group of inherited neurodegenerative disorders with fetal onset

Cerebellar hypoplasia is common to a variety of congenital disorders. Both stable conditions and progressive (degenerative) disorders may cause cerebellar hypoplasia. Pontocerebellar hypoplasia (PCH) is distinct from cerebellar hypoplasias in general, because the ventral pons is affected. Reviewing both clinical and neuropathological evidence, two specific neurogenetic entities are delineated. It is proposed to call these, respectively, type 1 (PCH-1) and type 2 (PCH-2). In type 1 the hallmark is the presence of spinal anterior horn degeneration similar to Werdnig-Hoffmann disease. Presentation in the neonatal period is characterized by respiratory insufficiency, frequent congenital contractures, and a combination of central and peripheral motor signs. Patients die early, usually before 1 year of age. In type 2 the hallmark is the presence of chorea/dystonia, which is often severe, while spinal anterior horn pathology is absent. Patients have microcephaly and severely impaired mental and motor development. They frequently die during childhood. Neuronal degeneration in both types of PCH is non-specific. Reactive changes in the degenerated parts appear more extensive in type 1. Examples of both types are given. Differentiation of the two types appears straightforward and possible by clinical means. Carbohydrate-deficient glycoprotein syndrome, one other cause of (ponto)cerebellar hypoplasia, should be excluded in all cases of PCH by appropriate means.