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Biomedical subjects

Gary L Hedlund

Publications and source records attributed to Gary L Hedlund.

8 recordsLinked to original sources
PubMed2006

Non-enhancing pilocytic astrocytoma of the spinal cord.

Pilocytic astrocytomas are among the most common intramedullary spinal cord tumors in the pediatric age group. The presence of contrast enhancement is a major factor used to distinguish these tumors from other spinal cord lesions. We present a case of histologically proved non-enhancing intramedullary spinal cord pilocytic astrocytoma in a 12-year-old girl. This case represents an exception to the conventional wisdom that pediatric spinal neoplasms enhance with administration of intravenous contrast material.

Arm↗
PubMed2006

Glutaric acidemia type 1.

Glutaric acidemias comprise different disorders resulting in an increased urinary excretion of glutaric acid. Glutaric acidemia type 1 (GA-1) is an autosomal recessive disorder of lysine, hydroxylysine, and tryptophan metabolism caused by deficiency of glutaryl-CoA dehydrogenase. It results in the accumulation of 3-hydroxyglutaric and glutaric acid. Affected patients can present with brain atrophy and macrocephaly and with acute dystonia secondary to striatal degeneration in most cases triggered by an intercurrent childhood infection with fever between 6 and 18 months of age. This disorder can be identified by increased glutaryl (C5DC) carnitine on newborn screening. Urine organic acid analysis indicates the presence of excess 3-OH-glutaric acid, and urine acylcarnitine profile shows glutaryl carnitine as the major peak. Therapy consists in carnitine supplementation to remove glutaric acid, a diet restricted in amino acids capable of producing glutaric acid, and prompt treatment of intercurrent illnesses. Early diagnosis and therapy reduce the risk of acute dystonia in patients with GA-1.

Amino Acid Metabolism, Inborn Errors↗
PubMed2005

Chiari I malformation in patients with FG syndrome.

OBJECT: The FG syndrome (FGS) is a common, heterogeneous group of clinically indistinguishable X-linked disorders comprising congenital hypotonia, macrocephaly, psychomotor delay, abnormalities in sensory integration, agenesis of corpus callosum, an unusual personality with behavior abnormalities, and disturbances of gastrointestinal function. On magnetic resonance (MR) imaging, some patients have evidence of tonsillar ectopia. The authors describe the incidence of Chiari I malformation in patients with FGS and attempt to determine the optimal treatment of these patients. METHODS: The authors performed a retrospective chart and radiological review of 144 pediatric patients with FGS for evidence of tonsillar ectopia on brain MR imaging. Eleven (7.6%) of these 144 patients had tonsillar ectopia, and in eight patients (5.6%), the tonsils were located more than 5 mm below the foramen magnum. Four of these patients underwent posterior fossa decompression, and surgery was performed at a mean age of 3 years. Indications for surgery included significant headaches and behavioral problems in two patients and failure to thrive with severe breathing and feeding difficulties in two infants. All four improved after surgery. The other patients remained asymptomatic from their tonsillar ectopia, showed no clinical or radiological signs of progression, and did not require surgery. CONCLUSIONS: Chiari I malformation is more common in individuals with FGS than in the general population. Some of these patients with FGS require decompression surgery, but the decision to operate can be difficult because of their developmental delay, difficulties with language skills, general fatigue, possibility of upper motor neuron dysfunction, behavioral problems, or failure to thrive, which may mask the symptoms of a Chiari I malformation.

Arnold-Chiari Malformation↗
PubMed2005

Nitric oxide increases the signal intensity of the T1-weighted magnetic resonance image of blood.

Human blood was infused through a gas permeable membrane to determine if treatment with nitric oxide affects the signal intensity of its T1-weighted magnetic resonance image. Equal volumes of blood with increasing concentrations of methemoglobin were placed in glass tubes. T1-weighted images of the samples were obtained with a 1.5T magnetic resonance scanner. There was a linear correlation between the signal intensity of the T1-weighted images and the amount of methemoglobin in each sample (r2 = 0.94, p = 0.0015). Thus, blood that has been treated with nitric oxide can potentially be used as an autologous intravascular contrast agent for magnetic resonance imaging.

Biomarkers↗
PubMed2004

Percutaneous cholecysto-cholangiography in the diagnosis of obstructive jaundice in infants.

BACKGROUND: Once it is established that a jaundiced infant has an elevated direct bilirubin level, the principal diagnostic concern is the differentiation of hepatocellular from obstructive cholestasis, of disorders of physiology from disorders of anatomy, and of disease that is managed medically from disease that is managed surgically. Traditional tests such as ultrasonography, liver biopsy, and technotium 99m HIDA scan are often not sufficiently discriminating. General anesthesia is required for invasive imaging with endoscopic retrograde cholangio pancreatography (ERCP) or operative cholangiogram. The authors describe a facile alternative using percutaneous cholecystocholangiography (PCC) with intravenous sedation. METHODS: Nine cholestatic infants underwent PCC (age, 27 to 73 days; mean, 44 days) after ultrasoundscan, liver biopsy, and (99mTc)HIDA scan failed to provide a definitive diagnosis. RESULTS: In the 4 infants without complete biliary filling, we found biliary atresia (3) and biliary hypoplasia (1). The biliary tree was completely opacified in 5 infants with the following diagnosis: neonatal hepatitis (2), duplication of the gallbladder (1), choledochocele (1), total parenteral nutrition (TPN) cholestasis (1). There were no complications. CONCLUSIONS: When the etiology of cholestasis remains elusive after traditional firstline tests, PCC has proven to be an accurate simple alternative in differentiating obstructive from hepatocellular causes of infantile cholestatic jaundice.

Biliary Atresia↗
PubMed2004

Spinal cord schwannomas mimicking drop metastases in a patient with intramedullary ependymoma and neurofibromatosis 2.

The authors describe a 9-year-old boy with a large spinal cord ependymoma whose apparent drop metastases on imaging studies were later demonstrated to be schwannomas. This finding led to the discovery of small bilateral acoustic neuromas and an intracranial meningioma, establishing the diagnosis of neurofibromatosis 2. The presence of additional radiographic abnormalities in a patient with a spinal cord tumor should prompt careful consideration of the diagnosis of neurofibromatosis 2, as early identification of this disorder may significantly affect patient management.

Child↗
PubMed2002

Neuroradiology of the central nervous system in childhood.

The purpose of this article is to familiarize readers with new imaging applications, identify the relative strengths of imaging modalities, and emphasize practical applications of imaging the child's nervous system. Because of recent advances in MRI, the article emphasizes the expanding role of MRI in evaluating children with neurologic disease.

Brain↗