Use of diffusion-weighted imaging in recurrent central nervous system Whipple's disease: a case report and review of the literature.

A case of Whipple's disease with development of antibiotic resistance is reported. The patient's symptomatology correlated with evolution of diffusion abnormality rather than with lesion enhancement. The lesion demonstrated no hyperperfusion, moderately elevated choline, and decreased N-acetylaspartate. Conventional magnetic resonance (MR) imaging findings of central nervous system Whipple's disease are nonspecific and may mimic neoplasm. MR perfusion and spectroscopy findings are reported, which may assist in diagnosis. Change in diffusion restriction appears to be a potential imaging indicator of clinical progression and response to therapy.

A glimpse of the brain transforming a sensory signal into a motor response.

Averages were made of neuronal spike activity recorded successively from eight relay regions along the auditorimotor pathway of naive cats and cats conditioned to blink in response to a 70 dB click conditioned stimulus (CS). It was hypothesized that the patterns of activity could be distinguished as sensory or motor by differences in their relationship to the pattern of the acoustic CS vs that of the conditioned response (CR). If so, it was also hypothesized that the acoustic stimulus would be better expressed at early auditorimotor relays and the motor response at later relays along the pathway. To test these hypotheses, Pearson correlation coefficients were calculated between the mean patterns of unit activity at each of the auditorimotor relays and (1) the rectified sound pattern of the CS and (2) the averaged, rectified electromyographic (EMG) activity of the muscles (orbicularis oculis) that produced the CR. In both naive and conditioned cats, there were significant positive correlations between the patterns of spike activity and the sound at early relays along the auditorimotor pathway such as the cochlear nucleus and inferior colliculus. In the conditioned animals, the spike activity of later nuclei in the auditorimotor pathway, such as the rostral thalamus and the motor cortex, had the highest positive correlations with the motor response. These correlations were low in the naive animals. Thus, the mean patterns of spike activity along the auditorimotor pathway appeared to distinguish the sound from the motor response and provided a glimpse of the process supporting transformation of the CS into the incipient CR.