Central nervous system disorders

III./3.1.: Computed tomography – CT 

III./3.1.1.: Unenhanced CT examination

Results of unenhanced imaging scans (CT/MR) performed in acute meningitis can be negative, i.e. existence of acute meningitis cannot be excluded by these methods. Ventricular dilation and squashed sulci can be percieved in over half of the patients. Although CT is not the imaging method of choice, CT scan is performed frequently in order to detect any sign which contraindicates the performance of lumbal punction. For example, no lumbal punction can be performed in case of increased intracranial pressure because of the risk of tonsillar herniation. Yet, negative CT report does not exclude the presence of increased intracranial pressure!

III./3.1.2.: Contrast enhanced CT examination

Enhancement appears in the filled basal cisterns. Besides the enhancement of the exsudate located in the subarachnoid space, enhancement of the pia mater is caused by the hypervascularisation as well developing due to leptomeningeal inflammation. Thus meningeal contrast enhancement  is surrounded by the cerebrum, especially frontally and parietally. Enhancement can extend into the Sylvius sulci and appear interhemispherically as well. Attention! If leaving the unenhanced series this strong enhancement can be illusive: it can be confounded with subarachnoid hemorrhage. Dural enhancement can be also accompanied.