Three new patients with congenital unilateral facial nerve palsy due to chromosome 22q11 deletion.

We report three unrelated patients with congenital facial nerve palsy and chromosome 22q11 deletion, a condition hitherto poorly recognized. In the first case, facial palsy was associated with aortic coarctation, ductus arteriosus, and ostium secundum atrial septal defect. In the second case, facial palsy was associated with ostium secundum atrial septal defect, obstruction of the ureteropelvic junction, double ureteropelvic-calicial system, and distal metaphyseal widening of the forearm and leg bones. In both cases, facial palsy was the presenting feature. In the third case, an ostium secundum atrial septal defect was also present, but involvement of cranial nerves III, VI, and VIII, in addition to hypoplastic structures of cerebellar and cerebral peduncles, were the predominant features. There were no inherited deletions within chromosome band 22q11 and the de novo deletions detected in each case belonged to the paternally derived chromosome 22. Association of facial nerve palsy and congenital heart disease versus cardiofacial syndrome are different only on clinical grounds, so both conditions can be genetically identical and form part of the spectrum of defects associated with chromosome 22q11 deletions. We recommend investigation for chromosome 22q11 deletions in patients with complete nerve facial palsy.

Intracranial compartment volumes in patients with enlarged ventricles assessed by magnetic resonance-based image processing.

Magnetic resonance image-based computerized segmentation was used to measure the volumes of the brain, gray and white matter components, and to identify regions with prolonged enhancement on T2-weighted imaging, such as periventricular or deep white matter hyperintensities. The authors also determined the volumes of the ventricles and subarachnoid space in control subjects and in patients with: 1) aqueductal stenosis (AS); 2) other causes of obstructive hydrocephalus (OH); 3) Alzheimer's disease (AD); and 4) normal-pressure hydrocephalus (NPH). In AS the volume of the brain was smaller, whereas that of ventricles and subarachnoid cerebrospinal fluid space was larger than that of controls. The decrease in brain volume was due primarily to white matter loss. Although in OH the ventricles were larger, the subarachnoid space was smaller than in controls, presumably due to encroachment by the brain, in which the volume remained unchanged. In AD, loss of both gray and white matter resulted in a smaller brain volume, whereas that of ventricles and subarachnoid space was larger than in controls. In NPH patients, only ventricular volume was greater, whereas all other compartments were similar to controls. The brain normally occupies 87% to 92% of the intracranial volume and consequently, as observed in our patients, relatively small decrements in brain size lead to large increments in ventricular and/or extraventricular volumes. The magnitude of such changes differed markedly among our patient groups, and whether such changes prove useful in clinical assessment and differentiation needs to be determined.

Age-related changes in intracranial compartment volumes in normal adults assessed by magnetic resonance imaging.

Magnetic resonance (MR) image-based computerized segmentation was used to measure various intracranial compartments in 49 normal volunteers ranging in age from 24 to 80 years to determine age-related changes in brain, ventricular, and extraventricular cerebrospinal fluid (CSF) volumes. The total intracranial volume (sum of brain, ventricular, and extraventricular CSF) averaged 1469 +/- 102 cm3 in men and 1289 +/- 111 cm3 in women. The difference was attributable primarily to brain volume, which accounted for 88.6% of the respective intracranial volumes in both sexes, but was significantly larger in men (1302 +/- 112 cm3) than in women (1143 +/- 105 cm3). In both, the cranial CSF volume averaged 11.4%. Total intracranial volume did not change with age, although the normalized brain volume of both men and women began to decrease after the age of 40 years. This decrease was best reflected by expansion of the extraventricular CSF volume which, after the age of 50 years, was more marked in men than in women. The volume of the cranial CSF, as determined by MR image-based computerized segmentation, is considerably larger than traditionally accepted and resides mostly extraventricularly. Expansion of CSF volume with age provides a good index of brain shrinkage although evolving changes and growth of the head with age tend to confound the results.

Perinatal exposure to anoxia alone does not alter the susceptibility to amygdaloid-kindled seizures in the adult rabbit.

It is suggested that asphyxia on newborns increases the susceptibility to epileptic syndromes. The effect of perinatal and postnatal anoxia on subsequent seizure susceptibility was assessed by amygdaloid kindling in adult rabbits. Rabbits from 1 day pre-term to 53 days were exposed to 100% N2 for an average of 7 min or until the heart rate was reduced by 70%. Non-anoxic littermates served as controls. At 2 months of age, animals were implanted with bilateral amygdalae electrodes. After a postsurgical recovery period, afterdischarge (AD) thresholds were determined for the electrode sites and a kindling paradigm was performed. There were no significant differences in the rate of kindling in all groups studied (control, anoxic at 1 day pre-term or at term, anoxic at 44 and 53 days). These results demonstrate that perinatal anoxia did not alter the seizure susceptibility in the adult rabbit kindling model.

MR studies of brain oedema in the developing animal.

Assessment of perinatal brain oedema is complicated by normal changes in brain water that accompany the marked physiological, biochemical and morphological alterations occurring during this phase of development. Multiexponential analysis of transverse decay curves (TDCs), derived from 128 echo CPMG images, of white matter (WM) made oedematous by either exposure of animals to triethyltin (TET) or cryogenic cortical lesions revealed a second, slower decay component not apparent in controls. More significantly, an obvious difference was noted between the TET and cryogenic lesion fast decay components which might serve as a basis to differentiate non-invasively cytotoxic and vasogenic oedemas.

Suppression of cerebrospinal fluid (CSF) production by a Na+/K+ pump inhibitor extracted from human cerebrospinal fluid.

A low molecular weight compound (about 600 daltons) extracted from human cerebrospinal fluid, and sensitive to proteolytic enzymes, has been shown to mimic the specific inhibitory effects of cardiac glycosides on the Na+/K+ pump of erythrocytes. The compound, which was labelled CSF-inhibitor (CSF-I) and reconstituted in artificial rabbit CSF, was used to study its effects on the rate of CSF formation in rabbits. Three groups of adult New Zealand white rabbits of either sex, anesthetized with ketamine and xylazine, and artificially respired were subjected to ventriculocisternal perfusions. Baseline rates of CSF formation were obtained during the first 2 hours of perfusion when plain rabbit CSF was used as the perfusate. Thereafter, the animals were perfused for an additional 2 to 3 hours with either plain rabbits CSF (controls), rabbit CSF containing 10(-6) M ouabain (group 2) or CSF-I (group 3). The rate of CSF formation in control animals was observed to gradually decline with time (about 7.5% in 4 hours). The addition of ouabain to the perfusate caused an abrupt and marked 43% decline in the rate of formation while the addition of CSF-I resulted in a 57% decline. These results suggest that the peptide CSF-I which is present in human CSF may act as an endogenous regulator of CSF production.

Ultrastructure of blood vessels in the ganglionic eminence of premature rabbits with spontaneous germinal matrix hemorrhages.

Approximately 20% of preterm rabbit pups develop spontaneous germinal matrix hemorrhages (GMH). To understand better the pathogenesis of GMH we studied the ultrastructure of germinal matrix (GM) blood vessels in rabbits delivered at gestational day 28. Regardless of luminal size, the walls of most GM vessels had the structural characteristics associated with a blood-brain barrier (BBB) and consisted of endothelial cells and pericytes, surrounded by GM cell processes. Endothelial cells ranged from voluminous to attenuated, with some cells containing intracytoplasmic, membrane-bound vacuoles, and luminal as well as abluminal cytoplasmic projections. Some short interendothelial junctions had no puncta adherentia, whereas long ones often possessed intermittent pores. In two animals with GMH, intact endothelial cells were separated by narrow and wide gaps filled with luminal contents that occasionally extended beyond the interendothelial opening. The basal lamina (BL) was ill-defined, thin, often discontinuous and of low electron density. Smooth muscle cells and collagen were not present, which precluded any classification into arteries, capillaries and veins. Germinal matrix cell processes lacking both micro- and intermediate filaments were haphazardly disposed around the blood vessel walls in place of astrocytic endplates. Recent reports indicate that an astrocytic environment may be necessary for the development of the interendothelial tight junctions and BL. The presence of "glial foot" processes that lack ultrastructural characteristics of mature astrocytes suggests that interendothelial junctions and basal laminae in the vessels of the ganglionic eminence may not have the necessary structural and functional potential to withstand the transmural pressures or the pathophysiological influence of hypertension, hyperosmolarity, sepsis, and other factors known to open the BBB and to contribute to GMH.

Proton magnetic resonance in myelin deficient brains of mutant mice.

The role of myelin in determining the magnetic resonance (MR) characterization of the central nervous system (CNS) was investigated in unmyelinated brains of normal fetal mice, as well as myelin-deficient adult mutant mice (shi, qk, mld) and their age-matched controls. In vitro NMR relaxation time measurements at 10 MHz for whole brains showed consistently longer T1 (range 558 +/- 8 to 580 +/- 27 msec) and T2 (range 81 +/- 3 to 89 +/- 3 msec) values for the adult myelin-deficient animals than the age-matched controls (T1 = 496 +/- 31, T2 = 79 +/- 4 msec). The fetal brains exhibited even more prolonged relaxation times (T1 = 976 +/- 60, T2 = 158 +/- 7 msec). MR images obtained at 81 MHz using spin echo (SE) sequences, which unlike the in vitro approach allowed discrimination between white and gray matter areas, revealed an absence of gray-white matter contrast in the brains of mutant mice, consistent with longer than normal relaxation of the myelin-deficient white matter. While larger tissue water components such as those present in the immature brain and edematous white matter contribute a greater effect, myelin and its associated bound water may still play an important role in the MR characterization of normal gray and white matter.

The effect of furosemide on intracranial pressure and hemorrhage in preterm rabbits.

The hypothesis that intracranial hypotension due to excessive postnatal fluid loss places the premature infant at risk for germinal matrix and intraventricular hemorrhage (GM-IVH) was tested in preterm rabbits delivered at 28 and 29 days of gestation (term 32 days). Furosemide administered to newborn pups induced a diuresis that resulted in a 11% to 22% loss in body weight and a concomitant decline in muscle water (13% to 16%) and sodium (18% to 21%). Paradoxically, no change occurred in the water or electrolyte content of the brain even though cerebrospinal fluid and brain tissue pressure, but not blood pressure, declined. These changes were absent in littermates treated with saline. Microscopic examination of brain sections revealed a greater incidence of intracranial hemorrhage, particularly in the germinal matrix and choroid plexus, in furosemide-treated than in saline-treated preterm rabbit pups. These results are consistent with the hypothesis that intracranial hypotension promotes the incidence of GH-IVH in preterm animals.

Proton magnetic resonance studies of triethyltin-induced edema during perinatal brain development in rabbits.

To better understand the role of myelin-associated water in the differentiation of white and gray matter in magnetic resonance (MR) imaging, changes in MR relaxation processes were studied in rabbits during myelination and after induction of cytotoxic edema with triethyltin (TET). Normal rabbits were killed at various age intervals ranging from premature (28 days' gestation) to adult, and changes in MR relaxation times (T1 and T2) and in water and electrolyte content were determined for various areas of brain and muscle. Similar measurements were made in rabbits of comparable age exposed to TET. Light and electron microscopy and MR imaging were used to follow myelin development and morphological changes induced by TET. During the first 30 postnatal days, both T1 and T2 declined by 50% in normal rabbits, a fall that paralleled the loss in brain water and sodium that occurred during the same period. Exposure to TET prolonged T1 and T2 in white but not gray matter, reflecting the accumulation of sodium and water (edema fluid) in white matter areas. Multiexponential analysis revealed a second, longer component in T2 magnetization decay of TET-exposed white matter, presumably attributable to accumulation of non-ordered water within intramyelinic vacuoles, a supposition consistent with electron microscopic and MR imaging findings. In contrast to reports by others, changes in T1 (but not T2) closely correlated with alterations in brain water (r = 0.93, df = 39). The absence of tissue disruption in the animals in the present study may account for these differences, but further studies will be required both to resolve this question and to fully understand MR images of white matter edema in mature and immature brain.

Developmental changes in proton magnetic resonance relaxation times of cardiac and skeletal muscle.

Proton magnetic resonance relaxation time measurements were used to study developmental changes in rabbit cardiac and skeletal muscles during the last days of gestation and at several postnatal times. Tissue water content decreased steadily during late fetal and early postnatal stages of development. During this period T1 and T2 for cardiac and skeletal muscles also decreased. The relaxation times stabilized after the 20th postnatal day, and at this juncture the T1 and T2 values for myocardium remained consistently higher than for skeletal muscle. The developmental changes in proton relaxation time probably represent changes in water distribution and mobility as well as macromolecular structure during muscle maturation.

Brain tissue pressure measurements in perinatal and adult rabbits.

Brain tissue pressure (BTP) in pre- and post-natal anesthetized rabbits, held in a stereotactic head holder, was measured with a fluid filled 23 gauge open-ended cannula connected distally to a pressure transducer. By advancing the cannula step wise through a hole in the cranium it was possible to sequentially measure pressure from the cranial subarachnoid space, cortex, ventricle and basal ganglia. Separate cannulas and transducers were used to measure CSFP from the cisterna magna and arterial and/or venous pressure. Pressure recordings obtained when the tip of the BTP cannula was located in the cranial subarachnoid space or ventricle exhibited respiratory and blood pressure pulsations equivalent to and in phase with CSF pulsations recorded from the cisterna magna. When the tip was advanced into brain parenchymal sites such pulsations were suppressed or non-detectable unless communication with a CSF compartment had been established inadvertently. Although CSF pressures in the three spinal fluid compartments were equivalent, in most animals BTP was higher than CSFP. However, after momentary venting of the system BTP equilibrated at a pressure below that of CSFP. We speculate that venting of the low compliance system (1.20 x 10(-5) ml/mmHg) relieves the isometric pressure build-up due to insertion of the cannula into brain parenchyma. Under these conditions, and at all ages examined, BTP in the rabbit is consistently lower than CSFP and, as with CSFP, it increases as the animal matures.

Increased release of brain serotonin reduces vulnerability to ventricular fibrillation in the cat.

Brain serotoninergic neurons are known to participate in cardiovascular regulation. Administration of the serotonin precursor 5-l-hydroxytryptophan in conjunction with the monamine oxidase inhibitor phenelzine and the selective peripheral l-amino acid decarboxylase inhibitor carbidopa has been shown to raise the repetitive extrasystole threshold in the canine heart. The present investigation demonstrates that this drug regimen increases the cerebrospinal fluid concentration of serotonin and its major metabolite, 5-hydroxyindoleacetic acid, by 330 and 830%, respectively. By contrast, cerebrospinal fluid concentrations of norepinephrine and its major brain metabolite, 3-methoxy-4-hydroxyphenylethyleneglycol sulfate, and of dopamine's metabolite, 3, 4-dihydroxyphenylacetic acid, were not significantly altered. Concomitantly, the ventricular fibrillation threshold was elevated by 42% and the effective refractory period prolonged by 7%. Efferent sympathetic neural activity was suppressed in the normal heart (from 7.9 +/- 1.3 to 3.9 +/- 1.1 impulses/s). The surge in sympathetic activity associated with acute myocardial ischemia was markedly attenuated. These results indicate that enhancement of central serotoninergic neurotransmission can reduce the susceptibility to ventricular fibrillation mediated through a decline in sympathetic neural traffic to the heart.

Furosemide lowers intracranial pressure by inhibiting CSF production.

Furosemide administration effectively lowers intracranial pressure in newborn preterm and term rabbit pups. This effect may be due to the diuretic action of the drug, its ability to inhibit cerebrospinal fluid production or to a combination of both. To test these possibilities newborn rabbits were either injected with furosemide and left unmolested for 6 hours, or anaesthetized and subjected to ventriculocisternal perfusions. During the 6 hour postnatal period the decrease in body weight was 8 times greater in furosemide than in saline treated pups. However, no difference was noted between the average brain weights of these two groups. Secondary effects of the diuretic were noted in blood (12.5% increase in the haematocrit over control value) and in muscle in which tissue water content and NA+ concentration were decreased while K+ concentration was increased. The fact that these parameters remained unchanged in brain suggests that the lowering of intracranial pressure was not attributable to the secondary effects of the diuretic agent. However, the marked reduction in cerebrospinal production noted following furosemide administration indicates that in newborn rabbits this may represent the primary mechanism by which furosemide lowers intracranial pressure.

Vasculature to the germinal matrix in rabbit pups.

The authors report a study of the cerebral vasculature of premature rabbits pertaining to the germinal matrix (GM). A pigmented silicone material (Microfil) was injected into the carotid artery of anesthetized rabbits. Methyl methacrylate vascular casts of a similar group of premature rabbits were examined by scanning electron microscopy. The GM is supplied by arteries from both the basal and convexity surfaces of the brain. Vessels could be identified as arteries or veins by their typical patterns of branching and by the characteristic impressions made on the methyl methacrylate casts by endothelial nuclei. Specific evidence of structural weaknesses in the vasculature, which could be a site of predilection for GM bleeding, was not observed. The similarities in basal ganglia vasculature between premature rabbits and humans justifies using the rabbit model to study vascular aspects of the GM and intraventricular hemorrhage.

The lowering of cerebral spinal fluid and brain interstitial pressure of preterm and term rabbits by furosemide.

CSF, brain interstitial, and arterial or venous pressures were measured in preterm and term rabbits. Ten to sixty minutes after the infusion of furosemide, in concentrations reported to inhibit CSF production, CSF and brain interstitial pressures fell an average of 1.4 and 1.8 cm H2O, respectively. No changes were observed in plasma osmolality, arterial or venous pressures. Histopathological examination of coronal brain sections showed the presence of germinal matrix and/or choroid plexus haemorrhages in four of eight brains examined. These results indicate that CSF and brain interstitial pressures of anaesthetised, restrained rabbits can be reduced to subatmospheric levels without altering serum osmolality. It remains to be established whether diminution of intracranial pressure by this method will increase the incidence of IVH in the awake, unrestrained preterm animal.

The preterm rabbit: a model for the study of acute and chronic effects of premature birth.

The fetal rabbit delivered by caesarean section 0 to 5 days before term (32 days) can serve as a reliable animal model to study the short- and long-term consequences of premature birth. More than 80% of the fetal rabbits delivered at day 28 of gestation will survive 24 h if anesthetics are avoided during delivery and measures designed to meet the metabolic demands of extrauterine life are met. Sixty percent will survive up to and beyond the 7th day postpartum if the preterm pups are kept in a temperature and humidity controlled environment and are fed rabbit milk. Theoretical and practical advantages of this animal model are discussed.