Teaching Case

Increased intracranial pressure

Presented with signs and symptoms of increased intracranial pressure. MR imaging, and MR spectroscopy using single-volume, spin-echo, point resolved spectroscopy (PRESS), (TR=1500 msec, TE=135 msec), were performed with a 1.5 Tesla Unit.

Proton MR spectroscopy provides biochemical information about the brain tissue. N-acetylaspartate (NAA), choline (Cho), and creatine (Cr) are the main metabolites which are detected on spectroscopy obtained with both long TE (i.e 135-270 msec), and short TE (i.e 10-40 msec) values. Others such as myoinositol, and glutamate-glutamine are usually detected with short TE values. Lactate, amino acids, and lipids are not visible in the normal brain. NAA is exclusively located in neuronal cell bodies and axons, so it is accepted as a neuronal and axonal marker. Destruction of the brain tissue with tumors and other causes result in a reduced NAA peak. Cho is a component of phosphoglyceride, and is the main component of cell membrane. Changes in the Cho peak reflect cell membrane turnover. In disease processes associated with cell membrane breakdown, and increased cell membrane synthesis the Cho peak tends to increase, as it is the case with tumors. Cr is an indicator for energy exchange related with high-energy phosphates. Its peak tends to increase when tissue metabolism is low, and tends to decrease when tissue metabolism is high, however, it usually is a stable peak. In the current patient, at the lesion site, a sharp decrease of the NAA peak reflected destruction of the brain tissue by the tumor, and prominent Cho peak represented increased cell membrane breakdown, and neoplastic cell synthesis. Cr decrease was an indicator of a high metabolic state. (these are shown in the figures with a comparison of spectroscopy from the contralateral, normal hemisphere). These were in conformity with the histopathological diagnosis, anaplastic astrocytoma, grade 3.