Tuesday, November 17, 2009

MRI Brain in Carbon monoxide poisoning

18 year old boy came with dizziness, head ache, nausea and loss of conciousness. Gives history of overnight sleeping in the room with burning charcoal heater. MRI FLAIR and T2 (a&b) image showing bilateral symmetrical hyperintensities in globus pallidi. (c&d) diffusion weighted images showing no restriction. features consistent with carbon monoxide poisoning.

In carbon monoxide poisoning, the gas crosses the alveolar capillary membrane and binds strongly with heme containing compounds. The toxicity is due to hypoxia and carbon monoxide mediated damage at the cellular level. Globus pallidus and pars reticulata of substantia nigra are the regions of the highest iron content in the brain. Carbon monoxide directly binds to heme iron in these two regions.

MRI in acute carbon monoxide poisoning, the abnormalities are detected as T2 hyperintensities. Lesions are in the basal ganglia involving the globus pallidus, putaman, caudate nucleus with other areas such as periventricular white matter, subcortical white matter, cerebral cortex, medial temporal lobe (hippocampus) and cerebellum. Diffusion Weighted Imaging(DWI) and MR Sprectroscopy are also useful. Diffusion weighted imaging shows diffuse hyperintensity in periventricular white matter and semiovale, splenium of corpus callosum, internal capsules, and brainstem, with moderately decreased apparent duffusion co-efficient (ADC) values. In the globus pallidus, the ADC values are rather increased, with low signal intensities on DWI as seen in this case. The MRS (MR Spectroscopy) demonstrates decreases n-acetyl aspartase in bilateral basal ganglia.

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