ARTICLE IN PRESS
Prostaglandins, Leukotrienes and Essential Fatty Acids 70 (2004) 357 360
In vivo MR spectroscopy in diagnosis and research of
neuropsychiatric disorders
I.J. Cox*, B.K. Puri
Faculty of Medicine, Imaging Sciences Department, Imperial College London, Division of Clinical Sciences, Robert Steiner Magnetic Resonance Unit,
Hammersmith Campus, Du Cane Road, London W12 0HS, UK
Accepted 18 December 2003
Abstract
Magnetic resonance spectroscopy is one of the most important tools for quantitative analysis of chemical composition and
structure, and this non-invasive technique is now being applied in vivo to study biochemical processes in those neuropsychiatric
disorders that are part of the phospholipid spectrum. Interpretation of a clinical magnetic resonance spectrum can provide
information about membrane phospholipid turnover, cellular energetics, neuronal function, selected neurotransmitter activity and
intracellular pH. Cerebral proton and phosphorus magnetic resonance spectroscopy findings are summarized in relation to
schizophrenia, dyslexia and chronic fatigue syndrome.
r 2004 Elsevier Ltd. All rights reserved.
1
1. Introduction atomic nuclei, such as hydrogen-1 (proton, H),
phosphorus-31 (31P), carbon-13 (13C), fluorine-19 (19F)
Nuclear magnetic resonance (NMR) spectroscopy is and nitrogen-15 (15N), can be imagined to act like tiny
one of the most important tools for quantitative analysis bar magnets when placed in a magnetic field. Each
of chemical composition and structure. Indeed four nucleus type resonates at a characteristic frequency
Nobel prizes have been awarded in the field: to Rabi in when placed in the same magnetic field. For example at
1 31
1944 for his resonance method for recording the 1.5 T the resonant frequencies for H and P nuclei are
magnetic properties of atomic nuclei; to Purcell and 63.7 and 25.8 MHz, respectively. During relaxation
Bloch in 1952 for their development of new methods for following excitation, radiofrequency signals can be
nuclear magnetic precision measurements and discov- detected which contain information about the magnetic
eries in connection therewith; to Ernst in 1991 for his environment experienced by each nucleus. In a MRI
contributions to the development of the methodology of study this information is related to the spatial position
high resolution NMR spectroscopy; and to Wuthrich in of the nucleus and in MRS studies this information is
.
2002 for his development of NMR spectroscopy for related to the molecules in which the nuclei are
determining the 3D structure of biological macromole- contained. Considering MRS applications the resulting
cules in solution. In addition, the Nobel Prize in signal, the free induction decay (FID), can be resolved
Physiology or Medicine 2003 was awarded jointly to into a frequency spectrum by the mathematical function
Lauterbur and Mansfield  for their discoveries concern- of Fourier transformation. In the absence of any
ing magnetic resonance imaging . magnetic field gradients the local magnetic environment
In the last two decades the NMR technique has been of a nucleus, and therefore it resonance frequency, is
applied in vivo to image the human brain (magnetic influenced by its immediate chemical environment. The
resonance imaging (MRI)) and also to study biochem- relative frequency position can be described by a
ical processes in the human brain (clinical magnetic parameter known as chemical shift, a dimensionless
resonance spectroscopy (MRS)). Specifically, certain unit accounting for the strength of the static magnetic
field and measured in parts per million.
In principle, the intensity of the metabolite signal is
*Corresponding author. Tel.: [phone]; fax: [phone]-
directly related to its concentration, but in practice there
3038.
E-mail address: [e-mail] (I.J. Cox). are so many variables that influence the signal intensity
0952-3278/$ - see front matter r 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.plefa.2003.12.010
ARTICLE IN PRESS
358 I.J. Cox, B.K. Puri / Prostaglandins, Leukotrienes and Essential Fatty Acids 70 (2004) 357 360
that absolute quantitation is difficult to achieve in vivo nolamine (PE), and l-phosphoserine, which are impor-
[1]. Factors that need to be considered include the tant precursors of membrane phospholipids. However,
relaxation parameters for each resonance, reference of many other metabolites, including sugar phosphates,
signal levels to a calibrated standard (for example, can contribute to this region of the spectrum, and
internal water or an external phantom) and the separation of these different peaks cannot be achieved
separation of overlapping peaks into individual compo- with the present in vivo methodology. The PDE peak
nent signals. In general many of these factors can be includes contributions from glycerphosphocholine
adequately considered with long examination times, but (GPC) as well as glycerophosphoethanolamine (GPE),
since a limiting factor for a clinical examination is the which are products of membrane breakdown.
length of time the subject can be still, time is generally of The proton is the commonest nucleus in biological
the essence. systems and has the highest absolute sensitivity. In vivo
Interpretation of a clinical MR spectrum provides MRS studies are a technical challenge for a number of
information about membrane turnover, cellular ener- reasons: the water signal is 10 000 times larger than
getics, neuronal function, selected neurotransmitter signals from metabolites of interest; the chemical shift
activity and the fate of anaesthetics and of certain covers a narrow range, so peak overlap is a problem and
drugs. The first set of 1.5 2.0 T horizontal magnets in there are stringent demands on magnetic field homo-
the early 1980s had a bore of approximately 20 cm, so it geneity; interaction between nearby protons within a
was feasible to study cerebral metabolism only in molecule (spin spin coupling) complicates the spectral
newborn infants [2]. It is now possible to obtain clinical pattern; the scalp lipid signal is many times larger than
MR spectra using whole-body 1.5 3.0 T MR systems [3], the metabolite signals, and produce broad features
either as an adjunct to a MRI examination or as a which can overlap and partially obscure the sharper
separate study. The availability of routine clinical MRI resonances from smaller, more mobile species. Never-
systems with localized spectroscopy capabilities has theless resonances can be assigned to N-acetylaspartate
considerably widened the applicability of clinical (NAA), an amino acid derivative thought to be located
MRS. There is scope for obtaining spectra from a in neurones, choline-containing compounds (Cho) such
number of different nuclei, generally on research MR as phosphoryl- and glycerophosphoryl-choline which
systems, which allows different aspects of in vivo participate in membrane synthesis and breakdown, and
biochemistry to be studied. creatine and phosphocreatine (Cr). In addition more
The phosphorus nucleus has proved to be particularly complex peaks can be identified from protons in a range
valuable in clinical in vivo MRS since resonances from of metabolites, if present, including lactate, inositols,
phosphocreatine (PCr), nucleoside triphosphate (NTP) alanine, glutamine and glutamate.
and inorganic phosphate (Pi) are readily observed. The
chemical shift of Pi is dependent on intracellular pH.
These parameters are of central importance in energy 2. Overview of clinical MRS findings
metabolism and have been invaluable in defining the
sequence of events termed as   secondary energy failure  In vivo cerebral phosphorus-31 magnetic resonance
in infants with neonatal encephalopathy due to intra- spectroscopy (31P MRS) is probably the best available
31
partum asphyxia. Whilst the P MR spectrum was technique for investigating membrane phospholipid
often normal within the first few hours following metabolism. Here, a summary is given of the cerebral
resuscitation, after 8 24 h a progressive decline in the proton and phosphorus magnetic resonance spectro-
PCr/Pi ratio and an alkaline pHi have been observed scopy findings in relation to schizophrenia, dyslexia and
despite adequate oxygenation and circulation in the chronic fatigue syndrome.
infant [4]. The magnitude of the fall in PCr/Pi correlated
with the subsequent neurodevelopmental abnormality 2.1. Schizophrenia
[4] and, for example the extent of brain alkalosis in the
31
first 2 weeks after birth has also been associated with the The first published in vivo P MRS study of brain-
severity of brain injury on MR imaging and neurode- membrane phospholipid metabolism was that of Pette-
velopmental outcome at 1 year [5]. This pattern of grew and colleagues [7]. In this study of the dorsal
secondary energy failure after hypoxia-ischemia has prefrontal cortex decreased levels of PME and Pi, and
contributed to the development of neuroprotective increased levels of PDE were found in a group of 11
strategies [6]. antipsychotic drug-na.ve, first-episode patients, com-
1

Of particular relevance to the study of membrane pared with a group of 10 matched normal controls. This
31
synthesis are the composite peaks in the P MR finding is entirely consistent with Horrobin s membrane
spectrum labelled phosphomonoester (PME) and phos- phospholipid model of schizophrenia, as it points to a
phodiester (PDE). The PME peak includes major reduction in neuronal membrane phospholipid bio-
contributions from phosphocholine (PC), phosphoetha- synthesis and an increase in phospholipid breakdown.
ARTICLE IN PRESS
I.J. Cox, B.K. Puri / Prostaglandins, Leukotrienes and Essential Fatty Acids 70 (2004) 357 360 359
Furthermore, an offshoot of the same study also pointed phospholipid abnormality in dyslexia, these findings
31
to the ability of in vivo P MRS to detect presympto- provided additional support for this hypothesis and
matic cerebral metabolism changes [8]. could be interpreted as difficulties in either the biosynth-
Numerous 31-phosphorus and proton studies have esis of PME and/or their incorporation into membranes
been carried out to investigate spectroscopy changes in this could lead to an excess of PME precursors.
different brain regions in schizophrenia. The findings These studies were complemented by a comparison of
from these studies have not always been consistent. For PME and PDE levels with erythrocyte membrane fatty
example, some, but by no means not all, subsequent acid concentrations [16]. Levels of PDE were signifi-
31
in vivo P MRS studies have replicated the above cantly correlated with reduced concentrations of the
findings of alterations in membrane phospholipid highly unsaturated fatty acids docosahexaenoic acid
metabolites in the prefrontal cortex [9,10] and temporal (DHA) (r ź 0:68; Po0:05) and eicosapentaenoic acid
lobe [11]. However, such studies of medicated patients (EPA) (r ź 0:78; Po0:02). No significant correlations
with chronic schizophrenia have not been consistent, were found between peripheral concentrations of any
although the more consistent findings in the prefrontal highly unsaturated fatty acids and PME levels, nor
region again include decreased PME and increased PDE between their essential fatty acid precursors and either
31
[12]. The range of different findings with P MRS have PDE or PME levels. Other 31-phosphorus metabolites
recently been reviewed by Pettegrew and colleagues [12]. also showed no significant correlations with the blood
Interestingly, in the case report by our group [13] of fatty acid measures. The correlations between central
an antipsychotic-na.ve patient with schizophrenia who measures of PDE and peripheral measures of DHA and
1

31
responded clinically to ethyl eicosapentaenoic acid, it EPA provide validation of cerebral P MRS as a non-
was found that following such treatment his PME and invasive technique for the study of membrane phospho-
31
PDE levels fell. This suggests that in vivo P MRS may lipid metabolism in vivo.
be useful in indexing the way in which eicosapentaenoic The first published proton MRS study consisted of 14
acid alters neuronal membrane phospholipid metabo- dyslexic men and 15 age-matched control men [17]. The
lism. main positive finding was a decrease in Cho/NAA in the
Proton MRS studies in schizophrenia have been left temporo-parietal lobe, which was considered to
reviewed by Puri [14]. In general, one of the most represent a decrease in Cho in this cerebral region. The
consistent findings of in vivo proton MRS studies of authors interpreted this to be indicative of a decrease in
schizophrenia is a reduction in NAA in the left total cell membranes in this brain region in develop-
(dominant) temporal lobe [14]. As mentioned above, mental dyslexia, without a concomitant decrease in the
NAA is believed to be located in neurones, so that this total neuronal volume. However, an alternative expla-
finding is consistent with the temporal lobe atrophy that nation of these findings has been put forward, which
has been described in post mortem studies of schizo- relates to the role of essential fatty acids in dyslexia [18].
phrenia. Since a major component of Cho consists of metabolites
of phosphatidylcholine, which is one of the major
2.2. Dyslexia phospholipids of mammalian cell membranes, then
these findings are consistent with reduced catabolism
In a study of dyslexia, two different possibilities for of phospholipids in the left temporo-parietal lobe in
MRS findings were considered. First, that the MR dyslexia. In turn, this is compatible with the findings of
31
spectrum from dyslexia and schizophrenia would be our group of increased PME on P MRS.
similar i.e. PDE would be elevated and PME reduced,
and second that the membrane abnormality in dyslexia 2.3. Chronic fatigue syndrome
is different to that in schizophrenia i.e. there would be
reduced incorporation of phospholipids into membranes The first systematic study of chronic fatigue syndrome
in dyslexia and therefore an increase in PME would be using magnetic resonance spectroscopy was published by
31
expected. In a P MRS study of 12 subjects who had our group and consisted of a proton MRS study in eight
previously been identified by educational psychologists patients with chronic fatigue syndrome and eight age-
as dyslexic were compared with 10 age- and sex-matched and sex-matched healthy control subjects [19]. The mean
normal controls [15]. The relative level of phosphomo- ratio of Cho/Cr in the occipital cortex in the chronic
noesters (PMEs), PME/bNTP and PME/PDE ratios was fatigue syndrome group was significantly higher than in
increased across the brain in the dyslexic adults the controls. No other metabolite ratios were significantly
compared with the matched controls in. The relative different between the two groups in either the frontal or
level of PDE and PDE/ATP did not differ significantly occipital cortex (the two regions of the brain investi-
between dyslexic and control groups. No other spectral gated). In addition, there was a loss of the normal spatial
parameters differed significantly between the groups. variation of Cho in chronic fatigue syndrome. Since
Given that there was already indirect evidence for a increased choline levels are associated with abnormal
ARTICLE IN PRESS
360 I.J. Cox, B.K. Puri / Prostaglandins, Leukotrienes and Essential Fatty Acids 70 (2004) 357 360
membrane phospholipid metabolism, specifically relating first-episode, drug-naive schizophrenics. A pilot study of the
dorsal prefrontal cortex by in vivo phosphorus 31 nuclear
to phospholipid head groups [20], our results suggest that
magnetic resonance spectroscopy, Arch. Gen Psychiatry 48
there may be an abnormality of phospholipid metabolism
(1991) 563 568.
in the brain in chronic fatigue syndrome.
[8] M.S. Keshavan, J.W. Pettegrew, K.S. Panchalingam, D. Kaplan,
In the year following the publication of the above
E. Bozik, Phosphorus 31 magnetic resonance spectroscopy detects
in vivo proton MRS study of chronic fatigue syndrome, altered brain metabolism before onset of schizophrenia, Arch.
Gen Psychiatry 48 (1991) 1112 1113.
another such study, also involving eight patients and
[9] P. Williamson, D. Drost, J. Stanley, T. Carr, S. Morrison, H.
eight matched control subjects and specifically investi-
Merskey, Localized phosphorus 31 magnetic resonance spectro-
gating the left basal ganglia, has been published by
scopy in chronic schizophrenic patients and normal controls,
another, independent, group [21]. The key finding from
Arch. Gen Psychiatry 48 (1991) 578.
this study was also an increase in Cho in the chronic [10] J.A. Stanley, P.C. Williamson, D.J. Drost, T.J. Carr, R.J. Rylett,
A. Malla, R.T. Thompson, An in vivo study of the prefrontal
fatigue syndrome patients, so that these results are
cortex of schizophrenic patients at different stages of illness via
consistent with the findings of our group.
phosphorus magnetic resonance spectroscopy, Arch. Gen Psy-
chiatry 52 (1995) 399 406.
[11] H. Fukuzako, T. Fukuzako, T. Hashiguchi, S. Kodama, M.
3. Discussion
Takigawa, T. Fujimoto, Changes in levels of phosphorus
metabolites in temporal lobes of drug-naive schizophrenic
In this paper we have seen that the non-invasive
patients, Am. J. Psychiatry 156 (1999) 1205 1208.
[12] J.W. Pettegrew, M.S. Keshavan, J.A. Stanley, R.J. McClure, C.R.
technique of in vivo MRS provides a powerful
Johnson, K. Panchalingam, Magnetic resonance spectroscopy in
investigative tool that allows the living chemistry of
the assessment of phospholipid metabolism in schizophrenia and
the brain to be studied. Its application to schizophrenia,
other psychiatric disorders, in: M. Peet, I. Glen, D.F. Horrobin
dyslexia and chronic fatigue syndrome has shed light on
(Eds.), Phospholipid Spectrum Disorders in Psychiatry and
changes in phospholipid metabolism that occur in these
Neurology, 2nd Edition, Marius Press, Carnforth, Lancashire,
2003, pp. 239 255.
disorders of otherwise unknown aetiology. It also
[13] B.K. Puri, A.J. Richardson, D.F. Horrobin, T. Easton, N. Saeed,
provides a method of following the development of
A. Oatridge, J.V. Hajnal, G.M. Bydder, Eicosapentaenoic acid
neonatal encephalopathy following hypoxia-ischaemia.
treatment in schizophrenia associated with symptom remission,
The applications of MRS as both a research tool and as
normalisation of blood fatty acids, reduced neuronal membrane
a diagnostic investigation in phospholipid spectrum
phospholipid turnover and structural brain changes, Int. J. Clin.
disorders in psychiatry and neurology are set to grow in Pract. 54 (2000) 57 63.
[14] B.K. Puri, MRI and MRS in neuropsychiatry, in: I.R. Young,
the years ahead.
D.M. Grant, R.K. Harris (Eds.), Methods in Biomedical
Magnetic Resonance Imaging and Spectroscopy, Wiley, New
York, 2000, pp. 1135 1143.
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