Genetic disorders affecting white matter in the pediatric age

Pediatric white matter disorders can be distinguished into well-defined leukoencephalopathies, and undefined leukoencephalopathies. The first category may be subdivided into: (a) hypomyelinating disorders; (b) dysmyelinating disorders; (c) leukodystrophies; (d) disorders related to cystic degeneration of myelin; and (e) disorders secondary to axonal damage. The second category, representing up to 50% of leukoencephalopathies in childhood, requires a multidisciplinar approach in order to define novel homogeneous subgroups of patients, possibly representing "new genetic disorders" (such as megalencephalic leukoencepahlopathy with subcortical cysts and vanishing white matter disease that have recently been identified). In the majority of cases, pediatric white matter disorders are inherited diseases. An integrated description of the clinical, neuroimaging and pathophysiological features is crucial for categorizing myelin disorders and better understanding their genetic basis. A review of the genetic disorders affecting white matter in the pediatric age, including some novel entities, is provided.

Terminology and classification of the cortical dysplasias

BACKGROUND

There have been difficulties in achieving a uniform terminology in the literature regarding issues of classification with respect to focal cortical dysplasias (FCDs) associated with epilepsy.

OBJECTIVE

S: To review and refine the current terminology and classification issues of potential clinical relevance to epileptologists, neuroradiologists, and neuropathologists dealing with FCD.

METHODS

A panel discussion of epileptologists, neuropathologists, and neuroradiologists with special expertise in FCD was held.

RESULTS

The panel proposed 1) a specific terminology for the different types of abnormal cells encountered in the cerebral cortex of patients with FCD; 2) a reappraisal of the different histopathologic abnormalities usually subsumed under the term "microdysgenesis," and suggested that this terminology be abandoned; and 3) a more detailed yet straightforward classification of the various histopathologic features that usually are included under the heterogeneous term of "focal cortical dysplasia."

CONCLUSION

The panel hopes that these proposals will stimulate the debate toward more specific clinical, imaging, histopathologic, and prognostic correlations in patients with FCD associated with epilepsy.

False negative findings in intraoperative SEP monitoring: analysis of 658 consecutive neurosurgical cases and review of published reports

OBJECTIVES

To determine the sensitivity of intraoperative monitoring in neurosurgical operations using somatosensory evoked potentials and to identify reasons for false negative findings and possible settings with an increased risk for monitoring failure.

METHODS

SEP monitoring of 658 neurosurgical operations was analysed. The target of monitoring was the function of a hemisphere in 251 cases, the brain stem in 198 cases, and the spinal cord in 209 cases.

RESULTS

In 27 cases (4.1%), monitoring was classified as false negative. Further analysis showed that five of these patients had experienced delayed neurological damage. Among the remaining 22 false negative cases, 14 had a minor neurological deficit and eight had severe neurological damage. Overall sensitivity and negative predictive value of SEP monitoring was 79% and 96%, respectively. For the detection of severe neurological damage the corresponding figures were 91% and 98%. Sensitivity of monitoring varied depending on the target of monitoring and the type of lesion. Monitoring was less likely to detect neurological damage in surgery for infratentorial tumours with brain stem compression, small lesions of the motor cortex, and small vessel damage during aneurysm surgery.

CONCLUSIONS

SEP monitoring has acceptable sensitivity for detecting neurological damage during different neurosurgical procedures. Distinct settings with an increased risk of monitoring failure can be identified. In these cases measures to enhance the sensitivity of monitoring should be considered.

[Sleep apnea in neurological disorders]

The results of the study of sleep apnea (SA) in different forms of neurological disorders (cerebral stroke, diabetic polyneuropathy, neuromuscular diseases and amyotrophic lateral sclerosis--ALS) are presented. Two hundred and two patients, 103 male and 99 female, aged 17-84 years, have been investigated, using questionnaires and polysomnography. Nocturnal recording of EEG, EMG, electrooculography, oronasal air flow, respiratory thorax and abdomen movements, oxyhemoglobin saturation and breathing sounds has been performed. Clinical features of sleep apnea (SA) were most prominent in patients with neuromuscular diseases (58%) and ALS (54%), however the nocturnal study confirmed the presence of SA in patients with diabetic polyneuropathy (53%, mean RDI 15.7 +/- 18.7 epis./h) and cerebral stroke (41%, mean RDI 12.6 +/- 15.6 epis./h). A comparison of the patient's characteristics and sleep breathing indices revealed that factors of neurological damage contribute most significantly to ALS, but in diabetic neuropathy, age and obesity play a greater role.

Magnetic resonance spectroscopy of cerebral cortex is normal in hereditary hyperekplexia due to mutations in the GLRA1 gene

Excessive startling and stiffness in hereditary hyperekplexia has been attributed to lack of inhibition at either the cortical or brainstem level. Six patients with hereditary hyperekplexia (HH) and a confirmed mutation in the gene encoding the alpha(1) subunit of the glycine receptor (GLRA1) underwent single voxel (1)H magnetic resonance spectroscopy (MRS) of the brainstem and an area of frontal cortex and white matter using a method that allows absolute quantification of metabolites. The results of MRS were within normal limits, although there was a tendency for the neuronal marker N-acetyl aspartate to be reduced in the brainstem of patients compared with that in controls. Thus, we found no evidence to support a deficit in the cerebral cortex in patients with hereditary hyperekplexia due to mutations in the GLRA1 gene.

Pathological heterogeneity of clinically diagnosed corticobasal degeneration

Two patients fulfilling suggested clinical diagnostic criteria for corticobasal degeneration (CBD) are presented, who were found at postmortem to have alternative pathological diagnoses not suspected during life, namely, Alzheimer's disease and Pick's disease, respectively. The nosological position of these cases is considered in light of a literature review of previous reports of clinically diagnosed corticobasal degeneration with atypical (not corticobasal degeneration) pathology. Since such phenocopies may be common, we suggest that all clinically diagnosed cases of corticobasal degeneration should initially be labelled as "corticobasal degeneration syndrome" (CBDS) to emphasize that this is a diagnosis based on clinical phenotype, with the term corticobasal degeneration being reserved for the specific neuropathological phenotype, which itself may have a variety of clinical presentations.

Epilepsy and malformations of the cerebral cortex

Malformations of the cerebral cortex (MCC) are often associated with severe epilepsy and developmental delay. About 40% of drug-resistant epilepsies are caused by MCC. Classification of MCC is based on embryological brain development, recognising forms that result from faulty neuronal proliferation, neuronal migration and cortical organisation. Hemimegalencephaly, an enlarged dysplastic hemisphere, can present as early onset severe epileptic encephalopathy or as partial epilepsy. In focal cortical dysplasia (FCD), MRI shows focal cortical thickening and simplified gyration. Patients have drug-resistant, often early onset epilepsy. Complete surgical ablation of FCD is accompanied by remission in up to 90% of patients, but may be technically difficult. Tuberous sclerosis (TS) is a multisystemic disorder primarily involving the nervous system; 60% of patients having epilepsy, with 50% having infantile spasms. TS is caused by mutations in the TSC1 and TSC2 genes; 75% of cases are sporadic. TSC1 mutations cause a milder disease. Bilateral periventricular nodular heterotopia (BPNH) consists of confluent and symmetric nodules of grey matter along the lateral ventricles. X-linked BPNH presents with epilepsy in females and prenatal lethality in most males. Most patients have partial epilepsy. Filamin A mutations have been reported in families and sporadic patients. Lissencephaly (LIS smooth brain) is a severe MCC characterised by absent or decreased convolutions. Classical LIS is quite rare and manifests with severe developmental delay, spastic quadriparesis and severe epilepsy. XLIS mutations cause classical lissencephaly in hemizygous males and subcortical band heterotopia in heterozygous females. Thickness of heterotopic band and degree of pachygyria correlate well with phenotype severity. Schizencephaly (cleft brain) has a wide anatomo-clinical spectrum, including partial epilepsy in most patients. Polymicrogyria (excessive number of small and prominent convolutions) has a wide spectrum of clinical manifestations ranging from early onset epileptic encephalopathy to selective impairment of cognitive functions. Bilateral perisylvian polymicrogyria may be familial. Patients present with faciopharingo-glosso-masticatory diplegia and epilepsy, which is severe in about 65% of patients.

Morphological neuroimaging of malformations of cortical development

Malformations of cortical development are classified on the basis of imaging features and stages of cortical development. They are grouped by causes of the malformation: abnormal glial and neuronal proliferation, abnormal neuronal migration and abnormal cortical organisation. Focal or multifocal and generalised forms are recognised in each of these groups. In the first group, generalised forms include microlissencephalies. Among focal-multifocal abnormalities, neoplastic forms include ganglioglioma and dysembryoplastic neuroepithelial tumours. Non-neoplastic forms include focal cortical dysplasia and tuberous sclerosis. Malformations due to abnormal migration include lissencephalies; cortical heterotopias are recognised in both focal and generalised forms. Abnormal cortical organisation includes polymicrogyria, in generalised or focal forms, and schizencephalies among the focal forms.

Etiological classification of CNS malformations: integration of molecular genetic and morphological criteria

Classification is a creative activity that helps us understand relationships. The traditional classifications of central nervous system malformations was based exclusively upon descriptive morphology, but these criteria must now be integrated with molecular genetic data to enable an etiological classification that also remains useful to the clinician, radiologist and pathologist, who rely upon imaging and tissue examination for diagnosis. Many cerebral malformations previously thought to be a single disorder are now known to be common end-results of several independent genetic mutations. Examples are holoprosencephaly and lissencephaly. Gradients of genetic expression along the axes of the neural tube, established at the time of gastrulation, may explain many varieties or anatomical and clinical manifestations of cerebral malformations, including the involvement of non-neural tissues such as in midfacial hypoplasia, that may be attributed to abnormal neural crest migration. Genes of cellular lineage and of symmetry may explain some hamartomatous malformations, such as tuberous sclerosis and hemimegalencephaly. Modern classification should be applicable to the entire CNS as well as regions; schemes that attempt to artificially isolate the cerebral cortex for a "regional classification" may be erroneous even though the genetic defect primarily affects cortical structures because genetic gradients in the neuraxis are excluded and some involve a more subtle but still important expression in subcortical structures.

Malformative intracranial cysts: diagnosis and outcome

INTRODUCTION

Prenatal investigations make it possible to follow up malformative intracranial cysts from their detection in utero through the postnatal period. By including those that will remain silent postnatally, precious information can be provided about their real natural history.

DIAGNOSIS

Contrary to common belief, the vast majority of these lesions, if not associated with other fetal anomalies, are benign in nature, remain clinically silent, do not evolve or even frequently regress spontaneously. They are compatible with a strictly normal life, whether requiring postnatal treatment or not.

TREATMENT

Surgery is rarely needed for the treatment of an evolving hydrocephalus or an expanding cyst.

PROGNOSIS

Clinical outcome is not correlated with cyst volume or location. Prognosis, therefore, does not rely upon brain deformation or translation but rather more upon brain integrity. To establish a correct prognosis all efforts must therefore aim to precisely analyze the brain anatomy. In this respect, fetal MRI is mandatory. Although chromosomal anomalies are rarely associated with isolated intracranial cysts, karyotype study is necessary.

CONCLUSION

The accuracy of diagnosis and prognosis depends mainly upon our ability to correctly interpret images, which in turn depends on the resolution of prenatal imaging and on experience. Median retrocerebellar fluid collections remain the most difficult to prognosticate, retrocerebellar cysts often being difficult to differentiate from mega cisterna magna and Dandy-Walker complex. In our hands, prenatal prognostication was correct in approximately 90% of the cases.

[Classical crossed syndromes of the medulla oblongata. A historical and topodiagnostic discussion]

Historical publications of the classical alternating medulla oblongata syndromes of Wallenberg, Babinski-Nageotte, Cestan-Chenais, Hughlings Jackson, Avellis, Schmidt, Dejerine, Spiller and Tapia were reviewed and critically analysed. We compare these descriptions with descriptions of the brainstem syndromes in well-known modern German, English and Russian neurological textbooks. The anatomic basis and etiology of the alternating medullar syndromes, and the main publications relating to these syndromes were discussed. Causes of the inconsistencies of the modern and historical descriptions of these syndromes might be an ignorance of the historical references. Progress and development of the clinical neurology and neuroanatomy in the late twentieth century, however, has also lead to correction and perfection of some historical descriptions in the modern neurological literature.

MR imaging of acquired fetal brain disorders

INTRODUCTION

Acquired fetal brain disorders represent the third indication of fetal brain MRI, after ventricular dilatation and malformations of the central nervous system.

DISCUSSION

MRI is an adequate imaging technique for evaluating fetal brain damage. Fetal brain response to brain injury may be acute, chronic or a combination of acute and chronic. An acute response is not as common in the fetal brain as in the postnatal period. A chronic response or the combination of chronic and acute response are the most common responses of the fetal brain to injury, whatever its origin. MRI also provides the natural history of acquired fetal brain lesions with regard to the stage of development.

LF 16-0687 Ms, a new bradykinin B2 receptor antagonist, improves neurologic outcome but not brain tissue prostaglandin E2 release in a rat model of closed head trauma combined with ethanol intoxication

BACKGROUND

LF 16-0687 Ms previously was reported to improve Neurological Severity Score (NSS) and decrease cerebral edema and prostaglandin E(2) (PGE(2)) release after closed head trauma (CHT) in rats. Here, we examined whether these beneficial effects of LF 16-0687 Ms are altered when CHT is accompanied by acute ethanol administration.

METHODS

Six groups of rats (n = 8 per group) were examined during combination of the following experimental conditions: CHT versus sham operation, LF 16-0687 Ms 3 mg/kg subcutaneously versus saline, and ethanol 2 g/kg versus saline.

RESULTS

After CHT, brain water content decreased and NSS improved with ethanol + LF 16-0687 Ms as compared with values after saline or ethanol. PGE(2) release decreased with ethanol (147 +/- 59 pg/mg tissue) but not with ethanol + LF 16-0687 Ms (286 +/- 194 pg/mg tissue).

CONCLUSION

Ethanol does not affect the improvement of NSS and the decrease of cerebral edema seen with LF 16-0687 Ms after CHT, but does reverse the ability of LF 16-0687 Ms to minimize the increase of PGE(2) release. In intoxicated patients, bradykinin antagonist therapy may improve post-CHT outcome without altering PGE(2) release.

Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT): Clinical Applications

Positron emission tomography and single-photon emission computed tomography are nuclear imaging modalities that excel in depicting the biological function of tissue. Unlike structural imaging methods, they provide functional diagnostic information about brain neoplasms, stroke, neurodegenerative disorders, epilepsy, cortical visual loss, and migraine.

A new leukoencephalopathy with brainstem and spinal cord involvement and high lactate

We identified eight patients with a distinct magnetic resonance imaging pattern of inhomogeneous cerebral white matter abnormalities and selective involvement of brainstem and spinal tracts. Proton magnetic resonance imaging showed increased lactate in the abnormal white matter. Clinically, the patients had slowly progressive pyramidal, cerebellar, and dorsal column dysfunction. The uniform, highly characteristic magnetic resonance imaging pattern and the similarities in clinical and magnetic resonance spectroscopy findings provide evidence for a new disease entity. Autosomal recessive inheritance is likely.

A multivariate classification study of attentional orienting in patients with right hemisphere lesions

OBJECTIVE

To characterize patterns of orienting dysfunction that were typical to patients with lesions in the right hemisphere (RH).

BACKGROUND

Brain lesions in the right hemisphere are commonly associated with dysfunction of visual orienting (e.g., visual neglect and extinction). In a clinical study of these symptoms, the multicomponent nature of attentional orienting calls upon a multivariate statistical design with careful selection of neurocognitive variables.

METHODS

Thirty-eight patients with verified brain lesions and four patients with peripheral motor dysfunction after poliomyelitis were included in the study. Cognitive function was evaluated in all patients. Three reaction-time (RT) measures derived from the cue-target paradigm were selected as features in a data-driven multivariate classification scheme to generate natural subgroups of patients.

RESULTS

Four subgroups were generated, with only RH patients allocated to two of them. All patients within one of the RH subgroups were characterized by a pattern of impairment earlier described as a "disengage failure" by Posner et al. ( 5, 6), signs of visual neglect on Behavioral Inattention Test, and a severely impaired cognitive function. Results for the other RH subgroup were heterogeneous on both experimental and clinical variables. Age and cognitive function were found to strongly influence two of the features, but could not predict the clusters generated from the RT measures.

CONCLUSIONS

The present findings show that the cue-target paradigm together with multivariate clustering of selected feature variables can serve as a useful tool to explore and characterize patients with right hemisphere lesions. Although the concept of "disengage failure" was suited to describe the typical RT pattern in patients with neglect, other neurocognitive models and concepts can be applied to the results in the current study.

An analysis of the definitions of mental illness used in state parity laws

OBJECTIVE

Thirty-four states have enacte mental health parity laws that require a health plan, insurer, or employer to provide coverage for mental illness equal to that for physical illness. This study analyzed definitions of mental illness used in state parity laws, identified factors influencing the development of these definitions, and examined the effects of different definitions on access to care for persons with mental illness.

METHODS

Specific language in each state's parity legislation was analyzed. Interviews were conducted with policy makers, mental health providers, advocates, and insurers to determine factors influencing a state's definition. Current definitions of mental illness used in the clinical literature and in federal policy were reviewed and compared with definitions used in state parity laws.

RESULTS

The definitions of mental illness used in state parity legislation vary significantly and fall into one of three major categories: "broad-based mental illness," "serious mental illness," or "biologically based mental illness." To define each of these categories, state legislatures do not rely on clinically accepted definitions or federal mental health policy. Rather, influenced by political and economic factors, they are developing their own definitions.

CONCLUSIONS

Definitions of mental illness in state parity laws have important implications for access, cost, and reimbursement; they determine which populations receive a higher level of mental health services. Future research must qualitatively examine how state definitions affect the use and cost of mental health services.

The topographic diagnosis of acquired nystagmus in brainstem disorders

Evidence is presented for a clinical classification of central vestibular syndromes according to the three major planes of action of the vestibulo-ocular reflex (VOR): yaw, pitch, and roll. The plane-specific vestibular syndromes are determined by ocular motor, postural, and perceptual signs. Yaw plane signs are horizontal nystagmus, horizontal past pointing, rotational and lateral body falls to the right or to the left, and horizontal deviation of perceived straight-ahead. Pitch plane signs are upbeat/downbeat nystagmus, forward/backward tilts and falls, and upward or downward deviations of the perceived horizontal. Roll plane signs are torsional nystagmus, skew deviation, ocular torsion, tilts of head, body, and perceived subjective visual vertical. The VOR syndromes defined in this way allow a precise topographic analysis of brainstem lesions according to their level and side. The lesional sites of yaw syndromes are restricted to the pontomedullary level (vestibular nucleus). A tone imbalance in pitch indicates bilateral (paramedian) lesions of the medullary or pontomesencephalic brainstem or bilateral dysfunction of the flocculus. A tone imbalance in roll indicates unilateral lesions, ipsiversive at the pontomedullary level (vestibular nuclei) and contraversive at the pontomesencephalic level (MLF and INC). A unilateral lesion (or stimulation) of the graviceptive pathways, which transduce input from vertical semicircular canals and otolith, affects function in roll, whereas bilateral lesions affect function in pitch.