Glutamate decarboxylase is not genetically linked to pyridoxine-dependent seizures

Several aspects of pyridoxine-dependent seizure (PDS) suggest a mutation affecting glutamate decarboxylase (GAD) as a possible cause. To examine the possibility of GAD linkage with PDS, the authors performed genotype analyses of three families using polymorphic markers near the GAD genes (GAD1 and GAD2). In each family, the affected siblings exhibited different genotypes for the GAD2 gene; in two families the GAD1 genotype was disparate. These findings suggest that a mutation of GAD is not directly involved in all cases of PDS.

Prenatal exposure to toluene results in abnormal neurogenesis and migration in rat somatosensory cortex

Toluene inhalant abuse during pregnancy may result in growth-retarded microcephalic newborns who subsequently demonstrate developmental impairment. By using a rat model of toluene-abuse embryopathy, we studied the effects of prenatal toluene exposure on the generation and migration of cortical neurons. Dams were exposed by gavage to either corn oil or toluene diluted in corn oil on d 6-21 of gestation. The time of origin of cortical neurons was determined in the mature pups of dams injected with the thymidine analogue 5'-bromodeoxyuridine on 1 d during the period from d 13-21 of gestation. 5'-Bromodeoxyuridine-labeled neurons were identified by immunohistochemistry in a 400-microm-wide column of somatosensory cortex. The brains of the toluene-exposed pups had a significant reduction in the number of neurons within each cortical layer (p < 0.001). Depending on the cortical layer, the generation of neurons in the toluene-exposed pups was delayed by 1 or 2 d. In addition, the brains of the toluene-exposed pups also showed evidence of abnormal neuronal migration. However, there were no differences in either brain weight or body weight between the control and toluene-exposed pups. These observations suggest that although prenatal toluene exposure results in abnormal neuronal proliferation and migration, brain weight in the toluene-exposed pups may be preserved by enhanced development of glia or the neuropil.

Longitudinal MRI findings in pyridoxine-dependent seizures

BACKGROUND

Pyridoxine dependency is an uncommon familial cause of intractable seizures in newborns and infants. Fewer than 100 patients have been reported, and only four reports have included examples of brain imaging findings. We report the first longitudinal MRI findings in two patients with this condition.

METHODS

Six brain MR scans, three each from two patients with pyridoxine-dependent seizures, were reviewed. Morphometry of selected axial images was performed to calculate the ventricle-to-brain ratio (VBR).

PATIENTS

A girl, followed for 5 years, presented with intrauterine fetal seizures and neonatal seizures, and pyridoxine dependency was confirmed at 3.5 months of age. This patient had a subsequent history of poor compliance with pyridoxine therapy and severe developmental disability. A boy, followed for 9 years, presented with neonatal seizures, and pyridoxine dependency was diagnosed at 8 months of age.

RESULTS

The serial MR scans demonstrated progressive dilation of the ventricular system and atrophy of the cortex and subcortical white matter together with an increase in the VBR. These progressive abnormalities were greater in the 5-year-old girl.

CONCLUSION

Pyridoxine-dependent seizures are due to an inborn abnormality in the pyridoxine-dependent synthesis of gamma-aminobutyric acid (GABA). The progressive MR changes may be due to chronic excitotoxicity caused by an imbalance of cerebral levels of GABA and glutamic acid.

Toluene abuse embryopathy: longitudinal neurodevelopmental effects of prenatal exposure to toluene in rats

To determine the longitudinal effects of prenatal exposure to toluene in rats, dams received daily gavage doses of toluene diluted in corn oil on Days 6 through 19 of gestation, whereas control dams received corn oil. Litters were evaluated either on Gestational Day 19, Postnatal Day 10, or Postnatal Day 21; morphometric analysis of brain and measurements of brain DNA, cholesterol, and protein were made. Prenatal toluene exposure produced growth retarded fetuses with smaller brain and caudate-putamen volumes, fewer forebrain cell nuclei (DNA), and a reduction in both hindbrain cell size (protein/DNA) and myelination per cell (cholesterol/DNA). Postnatal catch-up growth occurred in the prenatally toluene-exposed pups, and by Postnatal Day 21 these differences had resolved. However, on Postnatal Day 21, a significant reduction in forebrain myelination/cell was present in the prenatally toluene-exposed pups. Therefore, whereas the effects of toluene administered prior to the time of the brain growth spurt were, for the most part, reversible, these exposures resulted in reduced forebrain myelination that may be permanent.

Fulminant demyelinating neuropathy mimicking cerebral death

Guillain-Barré syndrome can very rarely present with acute quadripares and cranial nerve involvement resembling a locked-in state. We describe a very unusual case of fulminant neuropathy in a child who was previously exposed to vincristine. The clinical picture resembled brain death; however, electrodiagnostic studies led to the diagnosis of a peripheral neuropathy. Serial electrodiagnostic studies and pathologic findings confirmed demyelination.

Multiple organ failure after ingestion of pennyroyal oil from herbal tea in two infants

BACKGROUND

Hepatic and neurologic injury developed in two infants after ingestion of mint tea. Examination of the mint plants, from which the teas were brewed, indicated that they contained the toxic agent pennyroyal oil.

METHODS

Sera from each infant were analyzed for the toxic constituents of pennyroyal oil, including pulegone and its metabolite menthofuran.

RESULTS

Fulminant liver failure with cerebral edema and necrosis developed in the first infant, who died. This infant was positive only for menthofuran (10 ng/mL). In the other infant, who was positive for both pulegone (25 ng/mL) and menthofuran (41 ng/mL), hepatic dysfunction and a severe epileptic encephalopathy developed.

CONCLUSION

Pennyroyal oil is a highly toxic agent that may cause both hepatic and neurologic injury if ingested. A potential source of pennyroyal oil is certain mint teas mistakenly used as home remedies to treat minor ailments and colic in infants. Physicians should consider pennyroyal oil poisoning as a possible cause of hepatic and neurologic injury in infants, particularly if the infants may have been given home-brewed mint teas.

Development of a rat model of toluene-abuse embryopathy

A rat model was developed to study toluene-abuse embryopathy, a clinical syndrome which occurs in offspring of women who abuse toluene during pregnancy. On d 6-19 of gestation, eight dams received a daily gavage dose of toluene, 650 mg/kg body weight, diluted in corn oil, whereas eight control dams and eight pair-fed dams received corn oil. The fetuses were delivered on d 19 of gestation. In the toluene-exposed group, the weights of the fetuses were reduced by 21.6% (p < 0.001), and a delay in skeletal ossification was demonstrated. Toluene exposure significantly reduced the weight of the fetal brain by 11.9% (p < 0.001), as well as the weights of the heart, liver, and kidney. Organ weight/body weight ratios did not differ significantly. Morphometric analysis of brain sections demonstrated that toluene exposure resulted in smaller brains together with an increase in the size of the ventricular system and a reduction in the size of the caudate nucleus. Although toluene exposure resulted in a 13.7% reduction in maternal food consumption, the observations made in the pair-fed group did not differ from those made in the control group. These findings suggest that prenatal exposure to toluene results in generalized fetal growth retardation, and that these effects are not due to the reduction in maternal food consumption.

Spinal arteriovenous malformation presenting as meningitis

An 8-month-old boy presented with a two-day history of lethargy. Meningitis was suspected, and cerebrospinal fluid examination demonstrated pleocytosis and elevated protein. After initial improvement with antibiotic and steroid therapy, progressive lower extremity weakness developed, and a midthoracic spinal cord arteriovenous malformation (AVM) was diagnosed. These lesions present rarely in infancy; the classification and pathophysiology of spinal cord AVMs are reviewed.

Effects of environmental tobacco smoke exposure in utero and/or postnatally on brain development

We evaluated whether environmental tobacco smoke exposure in utero and/or postnatally affects the biochemical composition of the brain. Pregnant Sprague-Dawley rats were exposed to filtered air (FA) or to sidestream smoke (SS) for 4 h/d, 7 d/wk from d 3 of pregnancy until delivery, then their female pups were exposed to either FA or SS for 9 wk postnatally. This resulted in four exposure conditions: in utero FA followed by postnatal FA (FA/FA), in utero FA followed by postnatal SS (FA/SS), in utero SS followed by postnatal FA (SS/FA), and in utero SS followed by postnatal SS (SS/SS). After completion of the exposures, the brains were removed and divided at the pontomesencephalic junction into forebrain and hindbrain; each specimen was then analyzed for DNA, protein, and cholesterol concentration. Data were analyzed by 2-way analysis of variance. In utero SS had no effect on these three biochemical measurements. However, postnatal SS reduced hindbrain DNA concentration (an indicator of cellular density) by 4.4% (p = 0.001). In addition, the hindbrain protein/DNA ratio (an index of cell size) was increased in these animals by 8.4% (p = 0.001). Hindbrain weight was not affected by SS exposure, but body weight was reduced by 6.4% (p = 0.016). These data suggest that postnatal exposure to SS affects the hindbrain (a region which undergoes significant postnatal growth) by reducing the total number of cells and by increasing cell size. Hindbrain cellular hypertrophy may help offset the decrease in cell number, thereby leaving hindbrain weight unchanged. Despite preserved hindbrain weight, these effects of postnatal exposure to SS may result in neurologic dysfunction.

Behavioral and neurochemical changes in folate-deficient mice

Weanling mice were fed an amino acid-based diet supplemented with 0 or 11.3 mumol folic acid/kg diet for approximately 38 days to study behavior and neurochemistry in folate deficiency. After approximately 5 wk, mice fed the unsupplemented diet weighted approximately 70% as much those fed the supplemented diet. After 2 wk, mice fed the unsupplemented diet consistently discarded (spilled) more food, and after approximately 5 wk, they had spilled 3 times more than mice fed the supplemented diet. Serum folate, brain folate and brain S-adenosylmethionine of mice fed the unsupplemented diet were 4, 53, and 60% as high, respectively, as those of mice fed the supplemented diet. Pathologic changes were not evident in brain, spinal cord, or skeletal muscle of folate-deficient mice. The hypothalamic 5-hydroxyindole acetic acid/serotonin ratio and caudate dopamine, homovanillic acid, and 3,4-dihydroxyphenylacetic acid concentrations were lower in deficient than control mice. Folate-deficient mice develop a behavioral activity, food spilling, which may have a neurochemical basis in the serotonin and dopamine systems.

Transient cortical blindness in an infant exposed to methamphetamine

An 11-month-old boy was brought to the pediatric emergency department for evaluation of acute onset of irritability and involuntary side-to-side turning of the head. Neurologic examination revealed cortical blindness. Toxicologic studies of blood and urine were positive for methamphetamine. The infant's vision and activity returned to normal within 12 hours. The possible mechanisms of this unusual form of amphetamine toxicity are discussed.

Proton magnetic resonance spectroscopic imaging in childhood ataxia with diffuse central nervous system hypomyelination

The spatial distribution of metabolite signal intensities can be measured within entire sections of the brain by proton magnetic resonance spectroscopic imaging (1H-MRSI). A group of six patients (4 unrelated girls and 2 brothers from 5 families) with childhood ataxia with diffuse CNS hypomyelination (CACH) underwent long-echo-time, single-slice 1H-MRSI. Relative to controls, there was a decrease in the signal intensity of N-acetylaspartate, choline, and creatine throughout the white matter in all six patients. We identified lactate signals in white matter in three of them with advanced disease. The degree of white matter involvement was not homogeneous over the entire patient group, but did correlate with clinical presentation. Deep and posterior white matter tended to be more involved. There were no 1H-MRSI abnormalities in the gray matter. 1H-MRSI findings suggest that this syndrome is secondary to a metabolic defect causing hypomyelination, axonal degeneration, and, in the most compromised cases, accumulation of lactate. This study shows that CACH is not limited to girls.

Fatal infantile polyarteritis nodosa with predominant central nervous system involvement

BACKGROUND

Infantile polyarteritis nodosa usually presents in children under 2 years of age as a multiorgan system disease with signs of congestive heart failure or renal failure. This disease and Kawasaki disease may share certain clinical and pathological features.

CASE DESCRIPTION

We describe a child who first presented at 8 months of age with a febrile illness followed by a delay in motor and language development and a mild right hemiparesis. Five years later he died after developing oculomotor dysfunction, hypertension, and intracranial hemorrhage. Autopsy revealed focal segmental necrotizing vasculitis of cerebral arteries, without involvement of coronary or renal vessels.

CONCLUSIONS

Although this child was evaluated on several occasions during this time period, the diagnosis was not made antemortem. The predominant central nervous system features, both clinical and pathological, together with the prolonged course are the two unique features of this child's disease that need to be emphasized.

Cerebrospinal fluid 5-hydroxyindoleacetic acid and homovanillic acid in the pediatric opsoclonus-myoclonus syndrome

To study the purported role of central monoamine disturbances in the pathophysiology of the opsoclonus-myoclonus syndrome, the serotonin metabolite 5-hydroxyindoleacetic acid and the dopamine metabolite homovanillic acid were measured in cerebrospinal fluid samples from 27 affected children and 47 age- and gender-matched control subjects by high-pressure liquid chromatography with electrochemical detection. 5-Hydroxyindoleacetic acid and homovanillic acid concentrations in the cerebrospinal fluid were approximately 30 to 40% lower in opsoclonus-myoclonus patients compared to control subjects, and the normal inverse correlation between age and monoamine metabolite concentrations in the cerebrospinal fluid of control subjects was not found in opsoclonus-myoclonus patients. Patients with the lowest values were less than 4 years old, and a subgroup had extremely low levels, but differences in older children were not significant. Cerebrospinal fluid levels of 5-hydroxyindoleacetic acid and homovanillic acid were more positively correlated in control subjects than in opsoclonus-myoclonus patients. None of the patients exhibited high levels of monoamine metabolites. Homovanillic acid levels were slightly lower in the cerebrospinal fluid of patients receiving corticotropin or steroids at the time of lumbar puncture. Clinical variables that could be excluded were paraneoplastic etiology, anesthetic for lumbar puncture, syndrome duration, age at onset, gender, response to steroids, length of time until initiation of corticotropin or steroids, presence of seizures, opsoclonus, and functional impairment. These data suggest a disturbance and possible altered ontogeny of serotonin or dopamine neurotransmission in a subpopulation of children with opsoclonus-myoclonus with low cerebrospinal fluid levels of 5-hydroxyindoleacetic acid and homovanillic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of high-dose toluene on embryonic development in the rat

Developmental disability, intrauterine growth retardation, renal anomalies, and dysmorphic features have been described in offspring of women who abuse toluene during pregnancy. A Sprague-Dawley rat model was developed to study this clinical syndrome. During d 6-19 of gestation, 11 treated dams received daily gavage doses of toluene, 520 mg/kg body weight, diluted in corn oil, and 11 control dams received corn oil. This dose of toluene simulates the blood toluene levels obtained after an inhalation exposure to 3290 ppm toluene, an inhalation level in the lower end of the range experienced by toluene abusers. Maternal weight gain was 24% less in the toluene-exposed group (p < 0.002); however, there were no maternal deaths. The fetuses were delivered on d 19 of gestation, and 287 fetuses (148 toluene exposed, 139 control) were examined. Toluene treatment did not affect the number of implantations or stillbirths. There were no toluene-induced major congenital malformations or neuropathologic changes noted. In the toluene-treated group, the weights of the fetuses were reduced by 9.4% (p < 0.004) and placental weights were reduced by 10.3% (p < 0.01). Toluene exposure also reduced fetal organ weights as follows: brain 4.6%, heart 5.9%, liver 13.2% (p < 0.02), and kidney 13% (p < 0.05). Organ weight/body weight ratios did not differ significantly, suggesting that prenatal toluene exposure produced a generalized growth retardation.

Stable-isotope dilution GC-MS for determination of toluene in submilliliter volumes of whole blood

An accurate and sensitive yet simple protocol for the analysis of toluene in submilliliter quantities of whole blood using stable-isotope dilution GC-MS has been developed and evaluated for use in pharmacokinetic studies of toluene exposure. The method involves the use of toluene-d8, a relatively inexpensive chemical used as a solvent for nuclear magnetic resonance spectroscopy, as an internal standard and extraction with pentane. This procedure allows for the determination of toluene in whole blood down to approximately 5 ng/mL and is suitable for pharmacokinetic measurements and biomonitoring of exposure to toluene.

Reduced GABA synthesis in pyridoxine-dependent seizures

An abnormality in the pyridoxal-5'-phosphate (PLP) dependent enzyme, glutamic acid decarboxylase (GAD), which synthesizes gamma-aminobutyric acid (GABA), may underlie the epileptic syndrome of pyridoxine-dependent seizures. GABA synthesis by skin fibroblasts from an infant with pyridoxine-dependent seizures, and from five controls, was measured. PLP independent GAD activity was similar in control and patient fibroblasts, whereas the patient's PLP dependent GAD activity was reduced compared with controls. These findings support the hypothesis for the expression of this familial disease.

Nutritional factors and anticonvulsant therapies: effect on growth in children with epilepsy

Factors influencing growth before puberty were examined in a group of 32 epileptic children in a cross-sectional investigation. Participants in the study were divided into two groups according to what anticonvulsant drug, carbamazepine or valproic acid, they were currently taking. Dietary intakes of energy, iron, and zinc were assessed and hemoglobin and serum zinc concentrations were evaluated. Measurements of height and weight were compared with standard growth charts prepared by the National Center for Health Statistics, Hyattsville, MD. A Student's t test comparison was made along with analyses of covariance and stepwise regression, and no significant differences were found between the two groups of children in terms of height or weight. Linear growth was normal. We found that low dietary zinc intake, 64-87% of the recommended dietary allowance, was not associated with reduced height in children. In addition, neither the number of years taking anticonvulsant medication nor the total amount of drug intake had a significant effect on weight. This was an unanticipated result because valproic acid has been associated with weight gain because of increased appetite.

Visual evoked potentials and visual processing in stimulant drug-exposed infants

Prenatal exposure to cocaine and amphetamines has been associated with many adverse effects in infants, including neurological abnormalities. Recent evidence shows that the visual system may be useful in infancy to evaluate neurological functioning. Visual evoked potentials (VEPs) and visual recognition memory testing were carried out on eight infants with prenatal drug-exposure and eight controls, matched for ethnicity and socio-economic status. The drug-exposed infants performed significantly worse on the visual recognition test. However, there were no differences between groups on VEP testing and no correlations between tests. The results suggest that the difficulties found in visual recognition memory of drug-exposed infants are not related to neurological maturity, as measured by VEPs.

Brain injury and protective effects of hypothermia using triphenyltetrazolium chloride in neonatal rat

Colorless 2,3,5-triphenyltetrazolium chloride (TTC) is reduced by enzymes in functioning mitochondria to a red-colored compound, and has been used to differentiate areas of viable tissue from areas of infarction in adult animals. TTC was used to study the central nervous system protective effects of hypothermia on the neonatal rat exposed to hypoxia and ischemia. The effect of hypothermia on survival and weight gain was also determined. Seven-day-old Wistar rats with right carotid artery ligation were exposed to 3 hours of 8% oxygen and maintained at either 37 degrees C (n = 22) or 30 degrees C (n = 18). The survivors were sacrificed 2 days later and brain slices exposed to TTC. These slices were photographed and the percentage of damage to the right brain was estimated gravimetrically from the stained and unstained areas of enlarged images. The mean weight gains were 4.2 +/- 1.2 gm in the 30 degrees C group and -1.0 +/- 2.8 gm in the 37 degrees C group (P < .001). The survival in the 37 degrees C group was 77% and in the 30 degrees C group 100% (P < .025). The mean percentage damage to the right side of the brain in the 37 degrees C group was 45.5% (range: 0-87.5%); there was no detectable damage in any of the 30 degrees C group pups (P < .0001). In our study, TTC proved to be a rapid and simple method for assessing central nervous system injury in the neonatal rat. This study also confirms that moderate hypothermia is protective against hypoxic-ischemic brain injury.

Brainstem bilirubin toxicity in the newborn primate may be promoted and reversed by modulating PCO2

The auditory brainstem response (ABR) was monitored during infusion of bilirubin in six ventilated newborn rhesus monkeys (138-145 d gestation) while acute changes in pH were produced by varying inspired CO2. Prolonged respiratory acidosis without bilirubin infusion produced minimal changes in the ABR (one animal). CO2 exposure, usually initiated when the bilirubin level reached approximately 20 mg/dL, decreased arterial pH to values ranging from 6.85 to 7.10. ABR changes, including prolongation of the wave II-IV peak to peak intervals and decreased wave amplitudes, first developed 2-4 h after initial exposure to CO2. Total and unbound bilirubin levels at this time ranged from 376 to 564 mumol/L (22-33 mg/dL) and 38 to 65 nmol/L (2.5-3.8 micrograms/dL), respectively. Correction of respiratory acidosis produced partial to complete reversal of ABR changes within 3 to 20 min. Reexposure to CO2 immediately reproduced the ABR abnormality. Production and reversal of the abnormal ABR was obtained through two to three cycles in three animals. Thus, when the brainstem bilirubin level was near the threshold for toxicity, the effect of changes in PCO2 on the ABR were immediate, suggesting that auditory pathway toxicity is initially mediated by a reversible pH-dependent bilirubin-membrane complex. In contrast to humans, in monkeys auditory toxicity appeared to be a late manifestation of bilirubin toxicity, inasmuch as all monkeys were obtunded and apneic 30-70 min before ABR abnormalities appeared. Notwithstanding these limitations, the results support the hypothesis that bilirubin toxicity can be both promoted and reversed by modulating brain pH.

Electroencephalography laboratory diagnosis of prolonged QT interval

Patients with prolongation of the QT interval are at risk for significant neurological morbidity and mortality secondary to ventricular tachyarrhythmias. These patients frequently undergo electroencephalographic (EEG) examination to evaluate episodes of loss of consciousness, which may be associated with convulsions. Electrocardiogram recording as a part of the EEG is a simple and common practice, but analysis for possible QT prolongation is not routinely performed by electroencephalographers. This is, in part, due to the fact that while calculation of the corrected QT interval is straight forward, a calculator is generally required. A nomogram that is presented simplifies determination of the corrected QT interval, facilitating diagnosis of prolongation of the QT interval in the EEG laboratory.