PubMed · 11864872
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A Rivera. 2002. Nystagmus surgery.. https://doi.org/10.1136/bjo.86.3.254
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This review focuses on recent approaches to unravel the capacity of otolith-related brainstem neurons for coding head orientations. In the first section, the spatiotemporal features of central vestibular neurons in response to natural otolithic stimulation are reviewed. Experiments that reveal convergent inputs from bilateral vestibular end organs bear important implications on the processing of spatiotemporal signals and integration of head orientational signals within central otolith neurons. Another section covers the maturation profile of central otolith neurons in the recognition of spatial information. Postnatal changes in the distribution pattern of neuronal subpopulations that subserve the horizontal and vertical otolith systems are highlighted. Lastly, the expression pattern of glutamate receptor subunits and neurotrophin receptors in otolith-related neurons within the vestibular nuclear complex are reviewed in relation to the potential roles of these receptors in the development of vestibular function.
Head tremor is a typical feature of essential tremor. Patients with sporadic Parkinson's disease can have tremor of the tongue, lip, or chin, but classically do not have head tremor. We describe five patients with Parkinson's disease and head tremor in whom clinical and neurophysiological findings suggested that head tremor was a manifestation of Parkinson's disease.
INTRODUCTION: The effects of microgravity are often simulated by head-down tilt (HDT). While data exist for intracranial pressure (ICP) during short-term HDT, no corresponding data exist for long-term exposure to HDT or microgravity. A mathematical model was developed to predict these unknown long-term responses. Predicted pressures include those in the cerebral vasculature, ventricular and extra-ventricular cerebrospinal fluid (CSF), and the brain tissue extracellular fluid. METHODS: A mathematical model was used to predict steady-state responses to various stimuli. Simulated CSF infusion tests were used to estimate model parameters such as the filtration coefficient of the cerebral capillary bed. Short-term HDT simulations validated the model. Further simulations predicted ICP responses to long-term HDT and microgravity. RESULTS: Constant-rate infusion simulations predict that the filtration coefficient of the cerebral capillary bed is between 4.46 and 5.15 x 10(-3) {[(ml x min(-1)) x mmHg(-1)] x 100 g(-1)}. Short-term HDT simulations reproduced clinical observations for venous sinus pressure and ICP. Further simulations produced the following relationships: first, ICP is unaffected by the expected changes in central artery pressure. Second, ICP changes in parallel with central venous pressure. Third, ICP increases 0.37 mmHg per 1 mmHg decrease in blood colloid osmotic pressure. DISCUSSION: Results suggest that despite the presence of tight capillary junctions in the brain, the cerebral capillary filtration coefficient is of the same order of magnitude as measured in the calf and forearm. Simulations also suggest that ICP in microgravity is significantly less than that in long-term HDT and may be less than that in the supine position on Earth.