Article
SleepDisordered Breathing in Chiari Malformation Type 1
Child Development Center, Department of Paediatric Neurology, Leicester Royal Infirmary, Leicester, United Kingdom.
Pediatric Neurology (Impact Factor: 1.7). 10/2008; 39(3):2078. DOI: 10.1016/j.pediatrneurol.2008.05.017 Source: PubMed
ABSTRACT
Type 1 Chiari malformation is defined as an elongation of the cerebellar tonsils >6 mm below the foramen magnum. Central sleep apnea is a wellrecognized sign, and can be an initial presentation, of this malformation. Obstructive sleep apnea is not a widely recognized sign of Chiari type 1 malformation, though there were a few case reports. We present a 13yearold girl who presented at our respiratory clinic with excessive nighttime snoring. Magnetic resonance imaging revealed a Chiari type 1 malformation requiring decompression. We emphasize the importance of including cervicomedullary junction disorders in the differential diagnosis of apnea, and we review the literature concerning mixed apneas and obstructive sleep apneas in Chiari type 1 malformation.

 "A decision to proceed with suboccipital decompression for relief of symptoms can therefore become subjective and vulnerable to bias of the treating neurologist or neurosurgeon [8]. Coexisting compression of the medullary respiratory control centers may lead to sleep related breathing disturbance in the form of central sleep apnea, obstructive sleep apnea or hypoventilation [9] [10] [11] [12] [13]. Sudden unexplained death has also been reported [14]. "
Article: The role of nocturnal polysomnography in assessing children with Chiari type I malformation
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ABSTRACT: To evaluate nocturnal polysomnogram findings in children with suspected symptomatic Chiari type I malformation, correlate them with clinical and magnetic resonance imaging data and to determine if this information has value in clinical decision making process. A retrospective review identified 24 children with type I Chiari malformation, presumed symptomatic who had undergone neurological assessment, cranial magnetic resonance imaging and nocturnal polysomnography. Perimedullary subarachnoid space effacement on the magnetic resonance studies and the magnitude of cerebellar tonsillar descent in relation to the McRae line were correlated with frequency of obstructive or central sleep apnea, number of cortical arousals and evidence of impaired vocal mobility on laryngoscopy. The Wilcoxon rank sum test was applied for continuous variables and the Fisher exact test for categorical variables. The median age of the subjects was 6 years. The findings from 16/24 subjects with perimedullary subarachnoid space effacement (effaced group) were compared with those of 8/24 in the noneffaced group. The central apnea index [1.5 (IQR 13.5) versus 0.5 (IQR 01.5)] and cortical arousal index [12 (IQR 1019) versus 8 (IQR 6.59)] were significantly higher in the effaced group than in the noneffaced group (p=0.0376 and 0.0036 respectively). Greater descent of tonsils as measured by distance from the McRae line to the tonsil tip was associated with significantly higher central apnea index, total arousal index and respiratory event related arousals. Measurements of clivuscanal angle, Klauss index and pBC2 line did not correlate with abnormalities on polysomnography. The central apnea and arousal indices derived from the nocturnal polysomnogram correlate well with magnetic resonance imaging findings of subarachnoid space effacement and degree of tonsillar herniation. In children with Chiari type I malformation, the nocturnal polysomnogram findings provides important information that aids in the decision making process about proceeding with surgical decompression. 
 "Coexisting compression of the medullary respiratory control centers may lead to sleep related breathing disturbance in the form of central sleep apnea, obstructive sleep apnea or hypoventilation [9] [10] [11] [12] [13] "
Dataset: The role of nocturnal polysomnography in assessing children with Chiari type I malformation
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ABSTRACT: a b s t r a c t Objective: To evaluate nocturnal polysomnogram findings in children with suspected symptomatic Chiari type I malformation, correlate them with clinical and magnetic resonance imaging data and to determine if this information has value in clinical decision making process. Methods: A retrospective review identified 24 children with type I Chiari malformation, presumed symptomatic who had undergone neurological assessment, cranial magnetic resonance imaging and nocturnal polysomnography. Perimedullary subarachnoid space effacement on the magnetic resonance studies and the magnitude of cerebellar tonsillar descent in relation to the McRae line were correlated with frequency of obstructive or central sleep apnea, number of cortical arousals and evidence of impaired vocal mobility on laryngoscopy. The Wilcoxon rank sum test was applied for continuous variables and the Fisher exact test for categorical variables. Results: The median age of the subjects was 6 years. The findings from 16/24 subjects with perimedullary subarachnoid space effacement (effaced group) were compared with those of 8/24 in the noneffaced group. The central apnea index [1.5 (IQR 1–3.5) versus 0.5 (IQR 0–1.5)] and cortical arousal index [12 (IQR 10–19) versus 8 (IQR 6.5–9)] were significantly higher in the effaced group than in the noneffaced group (p = 0.0376 and 0.0036 respectively). Greater descent of tonsils as measured by distance from the McRae line to the tonsil tip was associated with significantly higher central apnea index, total arousal index and respiratory event related arousals. Measurements of clivuscanal angle, Klauss index and pBC2 line did not correlate with abnormalities on polysomnography. Conclusion: The central apnea and arousal indices derived from the nocturnal polysomnogram correlate well with magnetic resonance imaging findings of subarachnoid space effacement and degree of tonsillar herniation. In children with Chiari type I malformation, the nocturnal polysomnogram findings provides important information that aids in the decision making process about proceeding with surgical decompression. 
Article: NMR relaxation in solution of paramagnetic complexes: Recent theoretical progress for S >= 1
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ABSTRACT: Paramagnetic systems are materials with positive magnetic susceptibility, associated with unpaired electrons. The paramagnetic solutions of interest to chemists contain usually free radicals or transition metal complexes. In addition, certain species with triplet ground state, such as oxygen molecule, need to be considered sometimes. The presence of unpaired electron spins has a profound influence on NMR spectra of such solutions. The origin of the effects is found in the large value of the electronic magnetic moment, about 650 times that of the proton. The paramagnetic species influence the NMR spectra of liquids in several ways. First, the nuclear spin relaxation rates are enhanced. The paramagnetic relaxation enhancement (PRE) is caused by a random variation of the electron spinnuclear spin interactions, which open new pathways for longitudinal as well as transverse relaxation. The PRE is most often studied for I = 1/2 nuclei, but applications of oxygen17 (I = 5/2) are also quite common. Second, the NMR signals may be shifted, provided the relevant electron spinnuclear spin interaction has a nonzero average. Third, the spinspin splittings may also be affected. Moreover, paramagnetic complexes in solution often contain exchangeable ligands, and the exchange phenomena, together with the intrinsic relaxation, shift and splitting properties, contribute to the observed lineshapes and line positions in onedimensional as well as multidimensional NMR spectra. The paramagnetic effects have been used for several decades by chemists and biochemists as a source of structural, thermodynamic, and dynamic information. Applications of this type have been described in numerous books and reviews, recently by Bertini and coworkers (13). Another very active field of application of paramagnetic relaxation enhancement in recent years, is the development and use of paramagnetic materials as contrast agents in magnetic resonance imaging (MRI) (4,5). The fundamental origin of the paramagnetic effects on NMR spectral parameters is the magnetic hyperfine interaction between the nuclear and electronic magnetic moments (6). Assuming that the orbital angular momentum is quenched (7), the nuclear and electronic magnetic moments are proportional to the corresponding spin operators. Employing the language of spinHamiltonians (8), the hyperfine interaction can be expressed as:1Hhf=I·A·Swhere I denotes the nuclearspin vector operator and S the electronspin operator. Throughout this paper the spin operators are assumed dimensionless and the Hamiltonians are in angular frequency units. The symbol A is the hyperfine coupling tensor. It is often practical to split the hyperfine interaction into two components: the dipoledipole interaction between the nuclear magnetic moment and the electrons outside of the nucleus and the scalar interaction between the nuclear moment and the electron spin density at the site of the nucleus. The scalar interaction is also called the Fermi contact interaction, or simply contact interaction. The rotational average of the dipoledipole interaction is sometimes denoted as a pseudocontact term. In this review, we concentrate in the first place on the phenomenon of paramagnetic relaxation enhancement but we also mention recent theoretical developments in the neighboring fields. The first issue that needs to be clarified is the relation between macroscopic, observable properties of nuclear spins, and their microscopic counterparts. In solutions of transition metal ions or complexes, one can commonly consider a situation where the ligands carrying nuclear spins can reside in two types of environment: in the coordination sphere of the paramagnetic metal ion or in the bulk. If the ligand contains only one type of magnetic nuclei (which is the case for example for 1H216O isotopomer of water) or if we can disregard interactions between nuclear spins, each of the two sites can be characterized by nuclear spinlattice and spinspin relaxation times, T1 and T2, respectively. Assuming the paramagnetic species to be dilute, Swift and Connick (9) and Luz and Meiboom (10) derived a set of equations relating the observables of NMR experiments and the relaxation, shift and lifetime properties of nuclei in the paramagnetic complexes:2T1P1= PM τM+T1M3T2P1= PM τM T2M2+T2MτM1 +ΔωM2 T2M1+τM12+ ΔωM24ΔωP= PMΔωM τMT2M+12+τM2ΔωM2T1P1, T2P1, and ΔωP are the excess spinlattice relaxation rate, spinspin relaxation rate and shift measured for the ligand in solution (a difference between the quantity of interest in a paramagnetic solution and the corresponding value in a diamagnetic reference solution), while the properties with index M refer to the ligand in the paramagnetic complex. The symbol τM is the lifetime of the ligand in the complex and PM is the molefraction of ligand nuclei in bound positions. The concept of PRE is often used synonymous with the enhancement of the spinlattice relaxation rate. The PRE as given by Eq. (2) is commonly denoted as the "innersphere PRE". If only one type of paramagnetic species exists in solution, the PRE is proportional to the concentration of that species. The PRE normalized to 1 mM concentration of paramagnetic complexes is called "relaxivity". Another limiting situation arises when the paramagnetic species interact only weakly with the molecules carrying the nuclear spins. In such a case, it is not meaningful to speak about exchange between discrete sites, but rather about free diffusion or diffusion in a potential. One then speaks about outersphere PRE, still referring to the enhancement of the spinlattice relaxation rate. The outersphere PRE is also proportional to the concentration of paramagnetic material, in this case through the idea of "density of electron spins", and the concept of relaxivity is equally useful in this case. The theory of PRE has been subject to a comprehensive review in the mid1980s (11); different types of methods have been reviewed more recently (1214). The structure of the present review is as follows. We begin in Section II with a brief discussion of the "classical" SolomonBloembergen theory, a highfield limit, perturbationtype theoretical model, and some of its modifications. In Section III, we proceed with the socalled Curie spin relaxation, a relaxation mechanism occurring at high magnetic fields through the thermally averaged magnetic moment associated with the electron spin. In that context, we review briefly other interesting relaxation phenomena. In Section IV, we cover the PRE theory for a more general case, when the coupling between the electron spin and classical degrees of freedom in the surroundings, in the first place molecular rotations, is so strong that the perturbation approach breaks down. Next, in Section V, we go back to the perturbationbased theories (Redfieldlimit theories) for electron relaxation, but avoid some approximations inherent in the SolomonBloembergen approach. Spindynamics models, a nonanalytical way of taking rotations into consideration, are covered in Section VI. Section VII deals with the outersphere relaxation while Section VIII investigates the relation between the electron spin relaxation and vibrational degrees of freedom. Finally, concluding remarks are provided in Section IX. This review was completed in August 2003.
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