Biomedical subjects

S Blaser

Publications and source records attributed to S Blaser.

At least 19 recordsLinked to original sources

PubMed2001

Alexander disease: diagnosis with MR imaging.

BACKGROUND AND PURPOSE: To date, the demonstration of Rosenthal fibers on brain biopsy or autopsy specimens is considered a prerequisite for a definitive diagnosis of Alexander disease. We initiated a multiinstitutional survey of MR abnormalities in both presumed and confirmed cases of Alexander disease to assess the possibility of an MR-based diagnosis. METHODS: MR imaging studies in three patients with an autopsy-based diagnosis of Alexander disease were analyzed to define MR criteria for the diagnosis. These criteria were then applied to 217 children with leukoencephalopathy of unknown origin. RESULTS: Five MR imaging criteria were defined: extensive cerebral white matter changes with frontal predominance, a periventricular rim with high signal on T1-weighted images and low signal on T2-weighted images, abnormalities of basal ganglia and thalami, brain stem abnormalities, and contrast enhancement of particular gray and white matter structures. Four of the five criteria had to be met for an MR imaging-based diagnosis. In a retrospective analysis of the MR studies of the 217 patients, 19 were found who fulfilled these criteria. No other essentially new MR abnormalities were found in these patients. In four of the 19 patients, subsequent histologic confirmation was obtained. The clinical symptomatology was the same in the patients with and without histologic confirmation and correlated well with the MR abnormalities. MR abnormalities were in close agreement with the known histopathologic findings of Alexander disease. CONCLUSION: The defined criteria are sufficient for an in vivo MR imaging diagnosis of Alexander disease; only in atypical cases is a brain biopsy still necessary for a definitive diagnosis.

Brain↗

PubMed2000

Characterization and expression analysis of two human septin genes, PNUTL1 and PNUTL2.

The presence and role of septin proteins in yeast is well documented, but there is a growing appreciation for this family of proteins beyond yeast and extending to human cells. In this report we present the characterization and comparison of two highly similar human septin genes, PNUTL1 and PNUTL2. We compare the exon/intron structure of both genes, the steady-state mRNA levels in tumor cell lines and adult organs, the conceptual translation products from alternatively processed mRNAs and the development of specific immunologic reagents distinguishing either PNUTL1 or PNUTL2. The results illustrate a remarkable similarity between the two genes and their protein products while identifying specific differences in mRNA expression patterns. A summary of the described functional roles for mammalian septins is discussed along with an attempt to assimilate the alternative nomenclature existing for the same human septins, such as references to PNUTL1 and PNUTL2 as hCDCrel-1 and hCDCrel-2, respectively. The characterization of PNUTL1 and PNUTL2 represents a fundamental step in completing the characterization of the entire family of human septin genes.

Amino Acid Sequence↗

PubMed2000

Predictive value of computed tomographic myelography in obstetrical brachial plexus palsy.

Preoperative radiologic studies to detect root avulsions of the brachial plexus caused by birth trauma are considered useful in assisting with surgical planning for reconstruction. In this study, the predictive value of computed tomographic (CT) myelography in detecting nerve root avulsions at our institution was determined. Sixty-three consecutive patients with an obstetrical brachial plexus palsy who had had both preoperative CT myelography and reconstructive surgery were selected. All CT myelograms were analyzed post hoc by a single neuroradiologist in a manner blind to the surgical findings. At each root level of the brachial plexus, the presence of a pseudomeningocele was noted along with the presence or absence of rootlets within each identified pseudomeningocele. Extraforaminal root avulsions later determined at surgery were reviewed by a single surgeon in a manner blind to the radiographic results. Surgical and radiographic findings were then compared at each corresponding root level. A total of 281 roots were examined. The sensitivity, specificity, positive predictive value, and likelihood ratio for root avulsions with pseudomeningoceles were 0.63, 0.85, 0.40, and 4.2, respectively. For pseudomeningoceles for which rootlets traversing the sac could not be identified, these values were 0.37, 0.98, 0.74, and 18.5, respectively. The presence of pseudomeningoceles with or without rootlets was not a sensitive indicator of root avulsions. Root avulsions were better predicted by identifying the absence of rootlets in a pseudomeningocele. This absence on CT myelography may be used to suggest an extraforaminal root avulsion due to its high specificity and high likelihood ratio.

Birth Injuries↗

PubMed1999

Congenital toxoplasmosis: prenatal diagnosis, treatment and postnatal outcome.

We report a female patient with congenital toxoplasmosis who presented with hydrops fetalis and cerebral abnormalities, detected on fetal ultrasound. Following prenatal treatment, the hydrops fetalis resolved and at four months of age she has normal growth and development. This case emphasizes the potential good prognosis in cases with congenital toxoplasmosis detected and treated prenatally.

Adult↗

PubMed1999

Neurofibromatosis type 1: the role of neuroradiology.

Neurofibromatosis type 1 is the commonest of the phakomatoses with a prevalence of 1 in 3-4000. In common with most of the other phakomatoses it is a genetic disorder with typical dermatological manifestations. Many organ systems can be affected but brain, spine, cranial nerve and peripheral nerve involvement is frequent. In this review we will describe the central nervous system manifestations of neurofibromatosis type 1 and discuss some of the controversies raised by investigating children with this disorder.

Brain↗

PubMed1999

Neurofibromatosis bright objects in children with neurofibromatosis type 1: a proliferative potential?

OBJECTIVES: The purpose of this study was to investigate the natural history of the high signal intensities shown on long TR sequences-neurofibromatosis type 1 bright objects (NBO)-in children with neurofibromatosis type 1 (NF1). We have paid particular attention to the development of tumors in these areas of abnormality. METHODS: During a 12-month period in 1992 to 1993, 46 children with clinically proven NF1 had a magnetic resonance (MR) examination at our institution. These were reviewed along with any previous or subsequent MR examinations that had been performed. We recorded the number, volume, and distribution of the abnormal high signal intensities and their change with time when serial examinations were performed. RESULTS: NBO were found in 93% of 46 children with NF1 on the original cross-sectional study. The most common anatomic sites were the globus pallidus (30.4%), cerebellum (23.5%), and midbrain (16.2%). The number and volume of NBO varied significantly with age. NBO were uncommon in children younger than 4 years but were very common and extensive between 4 to 10 years. A significant reduction in the number and volume of NBO was demonstrated in children older than 10 years as shown on both the cross-sectional and longitudinal portions of the study. Eight brain tumors (nonoptic pathway) were demonstrated in the 46 children (17%) with 1 child having two tumors. Only 1 child had symptoms referable to the tumor at the time of diagnosis. Five tumors developed in NBO that were documented on serial MR examinations. All those cases developed in children aged 7 to 12 years, and all these children had higher than average numbers and volumes of NBO. CONCLUSIONS: NBO occur commonly in children with NF1 and are most prevalent between the ages of 4 and 10. We have shown a high frequency of brain tumors in our children with NF1, but the majority of these were asymptomatic. We have demonstrated proliferative change NBO in 11% of 46 children. Most NBO regress with age and seem to be benign, however, young children with a large number and volume of NBO should be followed closely with regular MR examinations because of an increased risk of proliferative change. neurofibromatosis type 1, magnetic resonance, tumor, astrocytoma, childhood.

Brain↗

PubMed1999

Anatomical and embryological considerations in the repair of a large vertex cephalocele. Case report.

The case of a neonate with a large vertex cephalocele is presented. The anatomical features of this anomaly were evaluated by means of magnetic resonance imaging and magnetic resonance angiography. Fusion of the thalami, dysgenesis of the corpus callosum, and failure of adequate formation of the interhemispheric fissure were characteristics of the major cerebral anomalies associated with the cephalocele. The absence of a falx in the midline, a split configuration of the superior sagittal sinus, and a dysgenetic tentorium with a concomitant abnormal venous drainage pattern were found in association with a large dorsal cyst. Repair of the anomaly was undertaken on the 3rd postnatal day. A cerebrospinal fluid shunt was required to treat hydrocephalus on Day 30. The child is well at age 3 years, but with significant developmental delay. The pathogenesis of this vertex cephalocele relates to semilobar holoprosencephaly and dorsal cyst formation. In addition, a disturbance in the separation of the diencephalic portion of the neural tube from the surface ectoderm or skin during the final phases of neurulation had occurred to help create the large cephalocele. Detailed preoperative imaging studies and awareness of the embryology and anatomy of this lesion facilitated the repair of the cephalocele. The prognosis of the child is determined not only by the presence of hydrocephalus, but also by the number of associated major cerebral anomalies. Options for treatment are discussed.

Embryonic and Fetal Development↗

PubMed1998

Familial growth hormone deficiency associated with MRI abnormalities.

Idiopathic growth hormone deficiency is, in most cases, a sporadic condition. In a number of these patients magnetic resonance imaging (MRI) demonstrates a small anterior pituitary, small or absent pituitary stalk, and ectopically located posterior pituitary. These findings have been attributed to a developmental defect, trauma, or ischemia at birth. We report on a case of familial isolated growth hormone deficiency with mother and son demonstrating the MRI findings described above. The son also had a Chiari type I malformation and medial deviation of the carotid arteries secondary to a narrow skull base. Testing failed to identify a mutation in either the Pit-1 gene or GH gene cluster. This case appears to be an autosomal dominant defect in early development, lending support to the hypothesis that dysgenesis, rather than birth trauma, may cause a small anterior pituitary and ectopic posterior pituitary.

Child↗

PubMed1998

Cerebellar arteriovenous malformations in children.

We review the presentation, imaging findings and outcome in 18 children with cerebellar arteriovenous malformations (AVM). This group is of particular interest because of the reported poor outcome despite modern imaging and neurosurgical techniques. All children had CT and 15 underwent catheter angiography at presentation. Several of the children in the latter part of the study had MRI. Of the 18 children, 17 presented with a ruptured AVM producing intracranial haemorrhage. The remaining child presented with temporal lobe epilepsy and was shown to have temporal, vermian and cerebellar hemisphere AVM. This child had other stigmata of Osler-Weber-Rendu syndrome. Three other children had pre-existing abnormalities of possible relevance. One had a vascular malformation of the cheek and mandible, one a documented chromosomal abnormality and another a midline cleft upper lip and palate. Six of the 17 children with a ruptured cerebellar AVM died within 7 days of the ictus. Vascular pathology other than an AVM was found in 10 of the 14 children with a ruptured cerebellar AVM who had angiography: 4 intranidal aneurysms, 5 venous aneurysms and 2 cases of venous outflow obstruction (one child having both an aneurysm and obstruction). The severity of clinical presentation was directly related to the size of the acute haematoma, which was a reasonable predictor of outcome.

Adolescent↗

PubMed1998

Cerebellar involvement in metabolic disorders: a pattern-recognition approach.

Inborn errors of metabolism can affect the cerebellum during development, maturation and later during life. We have established criteria for pattern recognition of cerebellar abnormalities in metabolic disorders. The abnormalities can be divided into four major groups: cerebellar hypoplasia (CH), hyperplasia, cerebellar atrophy (CA), cerebellar white matter abnormalities (WMA) or swelling, and involvement of the dentate nuclei (DN) or cerebellar cortex. CH can be an isolated typical finding, as in adenylsuccinase deficiency, but is also occasionally seen in many other disorders. Differentiation from CH and CA is often difficult, as in carbohydrate deficient glycoprotein syndrome or 2-L-hydroxyglutaric acidaemia. In cases of atrophy the relationship of cerebellar to cerebral atrophy is important. WMA may be diffuse or patchy, frequently predominantly around the DN. Severe swelling of white matter is present during metabolic crisis in maple syrup urine disease. The DN can be affected by metabolite deposition, necrosis, calcification or demyelination. Involvement of cerebellar cortex is seen in infantile neuroaxonal dystrophy. Changes in DN and cerebellar cortex are rather typical and therefore most helpful; additional features should be sought as they are useful in narrowing down the differential diagnosis.

Adolescent↗

PubMed1998

Etiology of acute childhood encephalitis at The Hospital for Sick Children, Toronto, 1994-1995.

Of 145 patients admitted to our hospital because of encephalitis-like illness, 50 patients hospitalized for > or =72 hours underwent standardized microbiological investigations. A confirmed or probable etiologic agent was identified in 20 cases (40%), including Mycoplasma pneumoniae (9 cases). M. pneumoniae and enterovirus (2), herpes simplex virus (4), Epstein-Barr virus (1), human herpes-virus 6 (HHV-6) (1), HHV-6 and influenza virus type A (1), influenza virus type A (1), and Powassan virus (1). In 13 cases (26%), a possible pathogen was identified, including M. pneumoniae in nine cases. Presenting features included fever (80% of patients), seizures (78%), focal neurological findings (78%), and decreased consciousness (47%). The frequency of findings at the time of admission vs. later in hospitalization was as follows: pleocytosis, 59% vs. 63%; electroencephalogram abnormalities, 87% vs. 96%; and neuroimaging abnormalities, 37% vs. 69%, respectively. The outcomes at the time of discharge were as follows: normal results of physical examination, 32% (16) of the patients; death, 2% (1); motor difficulties, 26% (13); global neurological deficits, 16% (severe, 6; mild, 2); mental status changes, 14% (7); visual defects, 8% (4); and hearing impairment, 2% (1).

Acute Disease↗

PubMed1998

Fetal bilateral subdural haemorrhages. Prenatal diagnosis and spontaneous resolution by time of delivery.

We report a patient diagnosed prenatally on routine fetal ultrasound, at 30 weeks' gestation, with subdural haemorrhage. The mother had suffered a mild abdominal trauma and had Factor XI deficiency; however, both were felt to be aetiologically insignificant. Prenatal follow-up showed a complete resolution of the haematoma and no postnatal sequelae have been noted to date. The aetiologies and outcomes in the few previously reported cases are reviewed and compared with our case.

Adult↗

PubMed1998

MR imaging in idiopathic growth hormone deficiency.

BACKGROUND AND PURPOSE: MR imaging findings of one or more of the following has been suggested to be a sensitive and specific indicator of hypopituitarism: small anterior pituitary gland, attenuated or absent pituitary stalk, and ectopic posterior pituitary. We hypothesized that these MR findings would be common in our group of patients with idiopathic isolated growth hormone deficiency (GHD) or multiple pituitary hormone deficiencies (MPHD) and would be a good indicator of the severity of the hypopituitarism. METHODS: MR images were obtained for 35 patients with idiopathic GHD (20 with isolated GHD and 15 with MPHD; age range, 2 to 17 years) and analyzed to define one or more of the following triad of abnormalities: 1) small/absent anterior pituitary, 2) truncated/absent pituitary stalk, and 3) ectopic posterior pituitary, as well as for any other associated anomalies. The findings were correlated with the clinical and biochemical presentation. RESULTS: Pituitary abnormalities were common in both groups (80% with isolated GHD, 93% with MPHD). We found a high frequency of midline CNS malformations, including optic nerve hypoplasia (9%), Chiari type I malformations (20%), and medial deviation of the carotid arteries (37%). Breech delivery, neonatal hypoglycemia, jaundice, micropenis, or single central incisor occurred equally with both isolated GHD and MPHD. In patients whose peak growth hormone level was less than 3 microg/L (n = 19), 90% had the MR triad, compared with 390% of those with growth hormone levels 3 microg/L or greater or less than 8 microg/L (n = 13) (P <.01). Almost all (92%) of those with ectopic posterior pituitary had anterior pituitary heights less than -2 SD for age. CONCLUSION: MR abnormalities were common in children with both isolated GHD and MPHD and were closely associated with peak growth hormone levels less than 3 microg/L. The presence of other CNS and clinical findings (eg, single central incisor and micropenis) supports the theory of an embryologic defect as the cause of the pituitary abnormalities.

Adolescent↗

PubMed1997

Omphalocele in Miller-Dieker syndrome: expanding the phenotype.

We report on a patient prenatally diagnosed with omphalocele, mild cerebral ventriculomegaly, nuchal fold thickening, and cystic changes in the umbilical cord who was found postnatally to have lissencephaly type I. Prenatal chromosome analysis showed a normal male karyotype; however, postnatal high resolution banding and FISH analysis, using a probe for locus D17S379 in chromosome region 17p13.3, demonstrated a deletion at 17p13.3 consistent with Miller-Dieker syndrome (MDS). A review documented four more cases with MDS/isolated lissencephaly/17p-, with omphalocele. Because MDS is a contiguous gene disorder, we speculate that a gene or genes in this region have a major role in the closure of the lateral folds or the return of the midgut from the body stalk to the abdomen at 5-11 weeks of gestation. Prenatal diagnosis of omphalocele with mild ventriculomegaly should prompt FISH analysis for a deletion in 17p13.3.

Abnormalities, Multiple↗

PubMed1997

99mTechnetium HMPAO imaging in children with the Sturge-Weber syndrome: a study of nine cases with CT and MRI correlation.

Demonstration of the full extent of abnormality in patients with the Struge-Weber syndrome (SWS) is important for prognosis and in planning surgery to remove the seizure focus. We compared single-photon emission computed tomography (SPECT), MRI and CT in nine children under the age of 4 years with seizures as part of SWS, in an attempt to determine the optimal method of imaging in different clinical settings. Seven unilateral and two bilateral cases were studied by interictal 99mtechnetium hexamethylpropyleneamineoxime (HMPAO) SPECT, and contrast-enhanced CT and MRI, giving information on 11 abnormal hemispheres. All imaging modalities showed abnormalities in every child. Perfusion imaging showed focal regions of decreased uptake in 9 of 11 (82%) abnormal hemispheres and demonstrated a widespread decrease but no focal defect in 2; it also revealed crossed cerebellar diaschisis in 2 cases. CT demonstrated typical gyriform calcification in 9 of 11 (82%) affected hemispheres. Contrast-enhanced MRI showed more extensive involvement than contrast-enhanced CT in 5 of 11 (45%) cases. The area of hypoperfusion shown by SPECT was smaller than the area of contrast enhancement on MRI in 6 of 11 cases (55%), comparable in 3 (27%) and larger in 2 cases (18%). CT is sufficient to confirm the clinical diagnosis of SWS, but MRI frequently shows more extensive abnormal areas. 99mTc HMPAO imaging is a useful addition when it is important to know the full extent of the disease, for example prior to surgery. It is likely to detect areas of hypoperfusion, representing ischaemic regions, which may act as an epileptogenic focus and may not be shown by CT or MRI.

Adolescent↗

PubMed1997

Coexistence of hemimegalencephaly and chronic encephalitis. Detection of cytomegalovirus by the polymerase chain reaction.

We report the extraordinary association of hemimegalencephaly with chronic encephalitis and cytomegalovirus (CMV) positivity in a 5-month-old infant with intractable seizures and a left hemisphere resection. Microscopy revealed a severe neuronal migration disorder (NMD) with fusion of gyri, marked disarray of neuronal lamination, neuronal gigantism and extensive neuronal heterotopias. Also widespread were microglial nodules, gliosis and nodular calcifications and some foci of frank necrosis with calcification. Occasional perivascular and leptomentingeal lymphocytic infiltrates were present. No viral inclusions were identifiable. Polymerase chain reaction on multiple specimens showed unequivocal CMV positivity. In intrauterine CMV infection. NMDs such as polymicrogyria are well recognized, but the association of hemimegalencephaly with CMV infection has not previously been described. Our finding of chronic encephalitis with CMV positivity and hemimegalencephaly in the same patient raises questions about the role of CMV in the etiopathogenesis of the NMD.

Brain↗

PubMed1997

Intracranial and spinal metastases from a ganglioglioma with unusual cytogenetic abnormalities in a patient with complex partial seizures.

We describe an unusual clinical presentation of a ganglioglioma in a patient with complex partial seizures. The patient underwent a right temporal lobectomy with subtotal tumor resection at age 15 years, followed by a complete resection 1 year later. Follow-up MRI scan a year later documented recurrence and leptomeningeal dissemination. Another biopsy was performed. Pathological examination revealed similar histology in all three resections, with a ganglioglioma showing no evidence of anaplasia. The tumor exhibited a number of karyotypic abnormalities, notably, a paracentric inversion of chromosome 7. In summary, despite lacking anaplastic features by conventional histological criteria, this ganglioglioma showed an unsusual karyotype and demonstrated radiological evidence of widespread dissemination.

Adolescent↗

PubMed1997

Positive epileptiform discharges in children with neuronal migration disorders.

Most epileptiform abnormalities show a negative polarity on EEG. Focal positive spike waves have rarely been identified in seizure disorders and are generally associated with physiological and neurological impairment. Results of EEG, computed tomography, MRI, and pathologic studies of 15 children with focal neuronal migration disorders who underwent surgery for refractory localization-related epilepsy were compared to examine the association between positive discharges and other findings. Subjects were studied both ictally and interictally by scalp EEG with the International 10-20 system and zygomatic or sphenoidal electrodes, and video EEG telemetry. The 5 children with positive discharges were significantly more likely to develop hemiparesis during the preoperative period (P < or = .025). Correlations were observed between positive discharges and lesions apparent on MRI situated around the rolandic fissure (P < or = .025). Children with positive discharges had a significantly less favorable outcome after surgical treatment (P < or = .025). Positive epilepti-form discharges in children with neuronal migration disorders may signal a more dysfunctional cortex leading to a focal neurological deficit or a more extended lesion than is detected on MRI. This would explain the less favorable outcome of seizures after surgery, since the epileptogenic areas and neuronal migration lesions cannot be completely resected.

Brain↗