Alexander disease: Ventricular garlands and abnormalities of the medulla and spinal cord

BACKGROUND

Alexander disease is most commonly associated with macrocephaly and, on MRI, a leukoencephalopathy with frontal preponderance. The disease is caused by mutation of the GFAP gene. Clinical and MRI phenotypic variation have been increasingly recognized.

METHODS

The authors studied seven patients with Alexander disease, diagnosed based on mutations in the GFAP gene, who presented unusual MRI findings. The authors reviewed clinical history, MRI abnormalities, and GFAP mutations.

RESULTS

All patients had juvenile disease onset with signs of brainstem or spinal cord dysfunction. None of the patients had a macrocephaly. The MRI abnormalities were dominated by medulla and spinal cord abnormalities, either signal abnormalities or atrophy. One patient had only minor cerebral white matter abnormalities. A peculiar finding was the presence of a kind of garland along the ventricular wall in four patients. Three patients had an unusual GFAP mutation, one of which was a duplication mutation of two amino acids, and one an insertion deletion.

CONCLUSION

Signal abnormalities or atrophy of the medulla or spinal cord on MRI are sufficient to warrant DNA analysis for Alexander disease. Ventricular garlands constitute a new sign of the disease. Unusual phenotypes of Alexander disease are found among patients with late onset and protracted disease course.

Neuropathology of Joubert syndrome

Very little documentation of the neuropathologic changes in Joubert syndrome exists. This paper presents a detailed postmortem neuropathologic study of a clinically and radiographically well-documented case of Joubert syndrome. In addition to aplasia of the cerebellar vermis and fragmentation of the dentate nuclei, there was marked dysplasia of structures at the pontomesencephalic junction and caudal medulla. There was abnormal decussation of the superior cerebellar peduncles and an enlarged iter (rostral 4th ventricle) with elongated tegmental nuclei (including the locus coeruleus). Neurons of the basis pontis and reticular formation appeared reduced. Extensive malformations of the medulla included hypoplasia of the inferior olivary nuclei, solitary nuclei and tracts, and the nucleus and spinal tracts of trigeminal nerve (cranial nerve V). Even more striking was dysplasia of the caudal medulla at the cervicomedullary junction, which was characterized by the absence of a posterior median sulcus, neuronal swelling and axonal spheroids in the region of malformed nuclei gracilis and cuneatus, and absence of pyramidal decussation. This study suggests that, in addition to vermal agenesis, Joubert syndrome is characterized by malformation of multiple brainstem structures. The latter could explain certain clinical features of the syndrome, including episodic hyperpnea and oculomotor apraxia.

Posterior fossa magnetic resonance imaging in autism

OBJECTIVE

To determine whether the sizes and volumes of the posterior fossa structures are abnormal in non-mentally retarded autistic adolescents and adults.

METHOD

Volume measurements of the cerebellum, vermis, and brainstem were obtained from coronal magnetic resonance imaging scans in 16 autistic subjects and 19 group-matched healthy controls. For the purpose of comparison with previous studies, area measurements of the midbrain, pons, medulla, total cerebellar vermis, and its three subregions were also obtained from a larger sample of 22 autistic males (mean age: 22.4 years; range: 12.2-51.8 years) and 22 individually matched controls (mean age 22.4 years; range: 12.9-52.2 years).

RESULTS

The total volume of the cerebellum and the cerebellar hemispheres were significantly larger in the autistic subjects with and without correcting for total brain volume. Volumes of the vermis and the brainstem and all area measurements did not differ significantly between groups.

CONCLUSIONS

There is an increase in the volume of the cerebellum in people with autism consistent with the increase in regional and total brain size reported in this developmental disorder. This finding is also concordant with evidence of cerebellar abnormalities from neuropathological and neuropsychological studies that point to the role of this structure, as part of a complex neural system, in the pathophysiology of autism.

Hypoplasia of medullary arcuate nucleus in unexpected late fetal death (stillborn infants): a pathologic study

OBJECTIVES

To evaluate the frequency, morphology, and pathogenesis (primary or secondary) of the abnormally developed medullary arcuate nucleus (ARCn) in stillbirths.

METHODS

We examined 26 stillbirths (24 antepartum, 2 intrapartum) that had a gestational age between 25 and 40 weeks and a normal karyotype. All of the stillborns were described as well-developed, with body length and weight proportional to their gestational age. Each case was submitted to complete autopsy examination, which included a systematic gross and microscopic evaluation of the body, the placental disk, and the umbilical cord and membranes. The brainstem was the particular focus of the histologic examination. The study of the various nuclei (nucleus hypoglossus, dorsal vagus motor nucleus, tractus solitarii nucleus, nucleus ambiguus, trigeminal tractus and nucleus, arcuate nucleus, and ventrolateral reticular formation and its neurons and parabrachial/Kölliker-Fuse complex) was performed on transversal serial sections through the entire pons and medulla oblongata. The histologic analysis was supplemented by volumetric reconstruction and immunohistochemical detection of both apoptosis and proliferating cell nuclear antigen.

RESULTS

Histologic examination showed abnormalities of the medulla oblongata ARCn in 9 fetuses (35%). In 8, a marked hypoplasia was evident, characterized by a volume reduction of the nucleus accompanied by neuronal depletion, whereas in 1 fetus the nucleus was completely absent (agenesis). The absence of gliosis, the negativity of the proliferating cell nuclear antigen analysis, and the similarities in apoptotic indices between the hypoplastic and well-developed arcuate are in keeping with a primary developmental defect. This anomaly is frequently associated with hypoplasia of the reticular formation and chronic hypoxia.

CONCLUSIONS

A high frequency of hypoplasia of the ARCn occurs in fetuses who have died "sine causa," ie, in a similar manner to that observed in sudden infant death syndrome. Chemoreceptors, although not involved in reflexogenic oxygenation in fetal life, become of vital importance intrapartum and postpartum; therefore, whenever impaired in the course of development, chemoreceptors may underlie cardioventilatory abnormalities critical to sudden infant death syndrome.

Adverse effects of prenatal tobacco smoke exposure on biological parameters of the developing brainstem

We aimed to study the consequences of chronic exposure to tobacco smoke in utero on the morphological and functional maturation of the brainstem by comparing stillbirths of smoker mothers versus nonsmoker mothers. A total of 42 stillbirths, aged 25-40 gestational weeks, underwent autopsy according to our guidelines (). The brainstem was studied on serial sections and by immunohistochemistry to assay the expression of the EN2 gene, somatostatin (SS) and the tyrosine hydroxylase enzyme (TH). We observed a significant correlation between maternal smoking and sudden intrauterine unexplained death (SIUD), hypoplasia of the ArcN, no immunostaining of the EN2 in the arcuate nucleus (ArcN), and of TH in the locus coeruleus (LC) (P < 0.05). An increased incidence of maternal smoking was also observed in fetuses with SS negativity in the hypoglossus nucleus (HypoglN). Exposure in utero to maternal smoking may strongly interfere with brain biological parameters, giving rise not only to structural developmental abnormalities of the arcuate nucleus, but also to a decrease of noradrenergic activity in the LC, of EN2 gene expression in the ArcN and of SS in the HypoglN.

Sleep-disordered breathing in patients with Chiari malformation: Improvement after surgery

Sixteen consecutive patients with Arnold-Chiari malformation type I and syringomyelia underwent full-night polysomnography (PSG). Sleep apnea syndrome (apnea-hypopnea index > 10) was diagnosed in 12 of 16 patients with 48% of central apneas. In six patients with sleep apnea syndrome, PSG was repeated an average of 203 days after decompression surgery. Postoperative PSG showed a decrease in the central apnea index from 14.9 +/- 5.5 to 1.3 +/- 0.6 (p = 0.03).

Craniosynostosis, ataxia, trigeminal anaesthesia and parietal alopecia with pons-vermis fusion anomaly (atresia of the fourth ventricle). Report of two cases

A probably new syndrome of craniosynostosis, ataxia, trigeminal anaesthesia, and parietal alopecia area associated with pons-vermis fusion anomaly (atresia of the fourth ventricle), in two unrelated Mexican girls, is described. The cerebellar anomaly was proven by CT scan only and it correlated with ataxia. Other abnormalities seen in both patients were midfacial hypoplasia, bilateral corneal opacities, low-set ears, mental retardation and short stature. This disorder could be a new neurocutaneous syndrome.

Early descriptions of the Arnold-Chiari malformation. The contribution of John Cleland

✓ John Cleland described an unusual congenital anomaly of the brain stem in 1883 in which the medulla was elongated, the fourth ventricle extended into the cervical canal, and the inferior vermis distorted caudally. In 1891 Chiari described two types of brain stem malformation; in one the cerebellar tonsils extended into the cervical canal without medullary deformation, while in the other there was caudal extension of the brain stem and cerebellum and prolongation of the inferior vermis into the cervical canal. The second type was termed the “Arnold-Chiari” malformation by other authors in 1907, and corresponds to the condition described earlier by Cleland. The anatomical features and differences between the types of malformation are tabulated.

Syringobulbia-myelia with obstructive sleep apnea

Central nervous system disorders may cause obstructive sleep apnea, but this sleep-related breathing disorder is rarely associated with a structural abnormality of the medulla. We present a patient with obstructive apnea resulting from autopsy-proven syringobulbia-myelia.

Pontocerebellar hypoplasia associated with respiratory-chain defects

Pontocerebellar hypoplasias are congenital disorders of brain morphogenesis which include such diverse etiologies as carbohydrate-deficient glycoprotein syndrome type 1, cerebromuscular dystrophies (Walker-Warburg syndrome, Fukuyama syndrome, muscle-eye-brain disease) and at least two types of autosomal recessive neurodegenerations known as pontocerebellar hypoplasia type I and II. Pontocerebellar hypoplasia type 1 is a lethal phenotype and clinical features include congenital contractures, respiratory insufficiency, central and peripheral motor dysfunction and spinal anterior horn degeneration. Type 2 is characterized by progressive microcephaly, extrapyramidal dyskinesia and normal spinal cord findings. In this paper, we describe a girl, born at 33 weeks of gestation, presenting with respiratory insufficiency and multiple contractures. MRI scan of the brain demonstrated pontocerebellar hypoplasia and cortical and diffuse periventricular white matter abnormalities. Postmortem examination showed pontocerebellar hypoplasia with extensive gliosis of the periventricular white matter and of the basal ganglia with normal spinal cord findings. Histology of skeletal muscle was normal. Biochemical analysis demonstrated multiple deficiencies of respiratory chain enzymes in skin fibroblasts. This case demonstrates a lethal phenotype of pontocerebellar hypoplasia without spinal cord abnormalities associated with a respiratory-chain disorder. The diagnostic workup in a patient whose brain image shows pontocerebellar hypoplasia should include a search for respiratory-chain impairment.

Brainstem involvement in high functioning autistic children

To determine involvements of the brainstem and/or cerebellum in autism, we compared midsagittal magnetic resonance images of the brains of high functioning autistic children with those of normal controls. We found that the midbrain and medulla oblongata were significantly smaller in these autistic children than in the control children. The pons area did not differ between the two groups, nor was there any difference in the cerebellar vermis area. The ratio of the brain stem and cerebellum to the posterior fossa area did not differ significantly between the high functioning autistic and the control children. A positive correlation between age and area of the cerebellar vermis was observed in autistic children but not in control children. Thus, it was suggested that significant anatomical changes in the midbrain and medulla oblongata existed in the autistic children and that growth of the cerebellar vermis in autistic children was different from normal children.

Brainstem tegmental necrosis and olivary hypoplasia: a lethal entity associated with congenital apnea

Previously, we reported an isolated case of a newborn with central apnea at birth, ventilator-dependence, and combined malformative and destructive brainstem lesions (1). We now report 2 additional cases with similar clinicopathologic features. All 3 patients were male (XY karyotype) and required immediate ventilatory support in the delivery room. Perinatal complications included polyhydramnios and breech presentation. Variable cranial nerve palsies and orofacial and limb anomalies were present. The patients dies within minutes of withdrawal of ventilatory support at 2 to 11 weeks after birth. Significant neuropathologic findings were localized to the caudal pons and medulla, and included tegmental necrosis (neuronal loss, gliosis, mineralization) with involvement of respiratory-related nuclei, and anomalies of rhombic lip derivatives (olivary hypoplasia, arcuate nucleus hyperplasia). Three-dimensional computer reconstructions facilitated clinicoanatomic correlations, and underscored the restriction of the lesions to pontine and medullary rhombomeres and rhombic lip. The histopathology of these cases suggests a malformative process occurring at the end of the first trimester (time of rhombic lip migrations), and a superimposed destructive process (tegmental necrosis) in the second half of gestation. Although the etiology is unknown, the segmental nature of the lesions suggests the possibility of an abnormality in homeobox gene regulation. These cases likely represent a distinct clinicopathologic entity that should be considered in the differential diagnosis of Moebius syndrome and failure to breathe at birth.

Neurenteric cyst of the craniocervical junction--case report

A 60-year-old female presented with occipital headache and limitation of neck movement. Neurological examination showed weakness of the right sternocleidomastoid muscle. Magnetic resonance imaging revealed a cystic lesion at the craniocervical junction and posterior compression of the brain stem. The lesion was totally removed through the transcondylar approach. The histological diagnosis was neurenteric cyst. The transcondylar approach provides a direct operative view of the clivus and anterior craniovertebral junction.

Spectrum of malformations of the hindbrain (cerebellum, pons, and medulla) in a cohort of children with high rate of parental consanguinity

We review 25 patients with a spectrum of hindbrain (cerebellum, pons, and medulla) malformations from a cohort of children with high parental consanguinity rate. Twenty-three of the 25 patients were born to consanguineous parents. The patients were classified in four groups. Eleven patients of 6 families had malformation of the hindbrain and midbrain with molar tooth sign (10 patients of 5 families with typical Joubert syndrome), 5 patients showed severe supratentorial anomalies in addition to the hindbrain malformations, 5 patients had pontocerebellar or cerebellar hypoplasia with anterior horn cell disease in the spinal cord (spinal muscular atrophy), and 4 patients showed malformations affecting predominantly the hindbrain without substantial involvement of other systems. A locus for Joubert syndrome was previously identified on chromosome 9q34.3 in two families, and a second locus on chromosome 11p12-q13.3 in another family. A third Joubert syndrome locus has been mapped at 6q23 and a mutation in the AHI1 gene at this site has been found recently in a further family from this cohort. Delineation of homogeneous subgroups of patients with hindbrain malformations and molecular genetic analysis of these groups may lead to identification of further loci, genes and mutations responsible for the malformations.

Cervical diastematomyelia in cervico-oculo-acoustic (Wildervanck) syndrome: MRI findings

Cervico-oculo-acoustic (COA) or Wildervanck syndrome is characterized by the triad of Klippel-Feil anomaly, bilateral abducens palsy with retracted bulbs (Duane 'syndrome') and hearing loss. The clinical findings of this syndrome have been well documented. A few case reports with MRI findings have appeared in the literature showing brainstem and cerebellar hypoplasia and vertebral segmentation anomalies. Our case is unique in that diastematomyelia of the lower medulla and cervical cord was accompanied by vermian hypoplasia, tonsillar herniation and resulting triventricular hydrocephalus in a child with Wildervanck syndrome. This case is presented with MR images. Children with Wildervanck syndrome should be investigated for craniospinal abnormalities with MR imaging.

Velocardiofacial syndrome associated with atrophy of the shoulder girdle muscles and cervicomedullary narrowing

Velocardiofacial syndrome is the most common microdeletion syndrome in humans. It is secondary to a chromosome 22q11 rearrangement and is characterized by craniofacial abnormalities, heart defects and learning disability. We report a case of a 10-year-old girl with a chromosome 22q11 deletion who, in addition to learning difficulties, hypernasal speech and mild dysmorphic features, had weakness and wasting of the shoulder girdle muscles but no cardiac involvement. Brain magnetic resonance imaging revealed narrowing of the cervicomedullary junction. The clinical features of this patient with velocardiofacial syndrome further expand the spectrum of abnormalities associated with this condition.

Pontomedullary disconnection: fetal and neonatal considerations

The cerebellar and pontocerebellar hypoplasias present a unique challenge when detected in the developing fetus. A diverse aetiology and prognosis make counselling of these families difficult. Advances in fetal imaging allow for more accurate diagnosis and counselling, but postnatal MRI is still required. A case is presented in which cerebellar hypoplasia was detected at 20 weeks gestation. Later fetal imaging provided further information, but a diagnosis of pontomedullary disconnection was not made until the postnatal MRI scan. The clinical findings and possible causes of such pontocerebellar abnormalities are discussed.

Late fetal pontine destruction

A child with an absent pons is described who died 8 weeks after birth. At postmortem examination, the defect was consistent with a vascular event in the last trimester.