CSF may yield normal routine results in one fourth of patients, and be minimally abnormal in as many as one half, thus it is crucial to identify the organism via India ink and serology. Opening pressure is elevated to above 200 mm H2O in approximately two thirds of patients, so this is an important test. Appearance can be clear or turbid. Titers may reach dilutions of 1000. False negatives can occur.
False positives occur with positive and due to test kit variations.
But a positive titer is sufficient to initiate therapy, while cultures are pending, in the appropriate clinical setting. Commonly in patients with increased intracranial pressure the ventricles are actually small. With MRI, T1 images may show low intensity lesions in the basal ganglia, which are hyperintense on T2 and may enhance with gadolinium. At times, intracranial hypertension, secondary to obstruction of the basal meninges or impaired absorptive mechanisms, and in the absence of mass lesions and or other risk of herniation, can be managed by CSF removal through repeated lumbar puncture, while others favor ventriculoperitoneal shunt. This results in many patients in almost immediate relief of headache, nausea and vomiting.