Nuclear medicine and ultrasound in the evaluation of neurologic diseases

Echoencephalography and radionuclide brain imaging are used to aid in the diagnosis of a variety of intracranial abnormalities. Because of technical considerations, A-mode rather than B-mode echography must, under most circumstances, be employed for examination of the head. There are technical limitations to echoencephalography, and it tends to be relatively subjective and dependent on the skill of the sonographer. These factors have, to some extent, been responsible for the more limited application of ultrasound to neurologic diagnosis, as compared to the application of radionuclides. The most common use of echoencephalography is in the detection of midline shifts associated with various sequelae of head trauma. Ultrasound has also been used to detect space-occupying lesions, either directly or more usually by determing associated midline displacements. The characterization and follow-up of known lesions with ultrasound has also been described. In the above instances its usefulness is usually as a noninvasive technique complementary to nuclear medicine studies, which under most circumstances are more effective than ultrasound. The evaluation of ventricular enlargement, which is not usually possible per se with radionuclides, is possible with ultrasound. Computerized transverse tomography (CTT) can be applied more efficiently in a routine way in many of the above circumstances, including evaluation of ventricular size. The combination of CTT and nuclear medicine procedures in the brain area is so effective and comprehensive that where these are both available the demand for ultrasound will probably decrease but will not be eliminated.