Published online by Cambridge University Press: 04 August 2010
Key points
MRS can provide useful clinical, metabolic information in infection, inflammation, and demyelination.
Pyogenic abscess have a unique metabolic pattern with decreased levels of all normally observed brain metabolites, and elevation of succinate, alanine, acetate, and amino acids, as well as lipids and lactate. This pattern is quite distinct from that seen in brain tumors.
Tuberculomas are characterized by elevated lipid and an absence of all other resonances.
MRS is extensively used in research studies of HIV infection; early changes include elevated choline and myo-inositol perhaps associated with microglial proliferation, while later changes (associated with cognitive impairment, and dementia) include reduced NAA (neuronal loss).
MRS may also be useful in assisting differential diagnosis in HIV-associated lesions.
MRS shows decreased NAA (suggesting axonal dysfunction and loss) in early multiple sclerosis, as well as increased Cho and myo-inositol and lipids (suggesting demyelination). NAA correlates with clinical disability. White matter that appears normal on T2 MRI may be abnormal metabolically in MS. Lactate may be elevated in acute, inflammatory demyelination.
Acute disseminated encephalomyelitis (ADEM) may show similar spectral patterns to MS; however, ADEM with good clinical outcome usually only shows mild NAA losses in lesions.
Introduction
Intracranial infection, inflammation, and demyelination include a wide range of disorders of the central nervous system (CNS). Magnetic resonance imaging (MRI) plays a crucial role in the diagnosis and therapeutic decision making in these diseases.
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