Central nervous system disorders

II./3.4.: General radiologic aspects of brain tumors

Importance of MRI: excellent tissue resolution and high sensitivity renders MRI an excellent diagnostic modality regarding brain tumors: relaxation time of tumorous tissues is usually longer as one of the adjacent tissues, thus their signal is lower on T1 weighted images compared to the one of the adjacent tissues. However, their signal is higher on T2 weighted images compared to the sorrounding tissues.

Secondary signs:

• - mass dislocation

• - dislocation of midline structures (midline shift),

• - impression on or dislocation of the ventricule,

• - hydrocephalus (sign of liquor circulation disturbance).

The above mentioned contrast enhancement patterns are also characteristic.

Even if MR examination is very sensitive, its specificity is often overestimated, leading to mistakes.

To configure the right diagnosis, beyond the knowledge on clinical symptoms the following aspects play also a role:

• - the characteristic age,

• - localisation of the tumor,

• - signal characteristics (registrated relaxation times).

• - contrast enhancement and distribution.

In certain tumors, hemorrhage can be present as an almost specifically characteristic lesion, such as in multiform glioblastoma, medulloblastoma, and hypophysis adenoma.

The metastases can present hemorrhage in case of choriocarcinoma, melanoma, hypernephroma, bronchogenic carcinoma.

We have to consider along with all above information that imaging methods guided diagnosis provides only a very probable approach! Histological diagnosis is provided only by histological sampling! (biopsy or exploration - surgery followed by a histological sampling).