The contribution of magnetic resonance (MR) imaging was retrospectively evaluated in 24 patients in whom CT demonstrated a supratentorial mass effect without significant additional localising features. Using a combination of T1-weighted inversion recovery (IR) and T2-weighted spin echo sequences, the MR images localised the lesion with greater precision than CT in 80% of cases. Areas of contrast enhancement were visible on the IR images in five of nine (56%) patients assessed after intravenous gadolinium-diethylenetriamine pentaacetic acid, where no comparable enhancement was seen on CT. Twenty of the 24 patients subsequently underwent surgery; eight had biopsies and 12 had resections. Magnetic resonance accurately predicted the site of the tumour in all these patients. Three of the remaining four cases were treated with radiotherapy on the basis of the MR findings without a tissue diagnosis being sought. Magnetic resonance produces better localization than CT and provides a sound basis for further diagnostic and therapeutic procedures.

Adult↗

PubMedDate not supplied

Voluntary, non-visual control of the human vestibulo-ocular reflex.

Voluntary control of the human vestibulo-ocular reflex with and without visual targets was investigated. Subjects were rotated sinusoidally from 0.1 to 1.0 Hz using d.c. electro-oculography to record eye position. The ratio of eye to head movement, or gain, of the vestibulo-ocular reflex was measured. When subjects were rotated in the dark at 0.3 Hz whilst performing mental arithmetic the gain was 0.65. When subjects were asked to fixate imaginary targets in the dark that were stationary in space, the gain rose to 0.95. When they imagined targets rotating with them on the chair, the gain dropped to 0.35. Our results indicate that the ability to modulate the gain of the vestibulo-ocular reflex does not depend entirely on the smooth pursuit system. Higher centers must modulate eye velocity so that it is appropriate to the subject's choice of a frame of reference, whether or not vision is available.

Adolescent↗