Faculty Bibliography

The Integrative Action of the Nervous System by the British physiologist Charles Sherrington was published 100 years ago. Its goal was to explain how the nervous system welds a collection of disparate body parts and organs into a unified individual. Sherrington postulated that the reflex is the simplest unit of nervous integration. He introduced the concept of the synapse as the site where elementary reflexes interact to enable more complex and unified behavior and argued that a synaptic nervous system facilitated the evolution of the cerebrum and cerebellum. The concept of the synapse as a physiological entity provided a theoretical schema into which the richly varied phenomenology of nineteenth century reflex physiology could be assimilated. Sherrington's book also provided the conceptual framework for a century of research into the mechanisms of synaptic transmission and the neuronal discharges associated with perception and action

This group of researchers showed previously that patients with back pain alter the pattern of activation of the trunk muscles during limb movement. Normally, during . . . Covering: Moseley GL et al., Brain 2004 Oct; 127:2339-47

Syringomyelia is frequently accompanied by an extramedullary lesion at the foramen magnum, particularly a Chiari I malformation. Although syringomyelia associated with foramen magnum obstruction has characteristic clinical, radiological, and neuropathological features, its pathogenesis remains unclear. Currently prevalent hydrodynamical theories assert that obstruction of the subarachnoid space at the foramen magnum interferes with flow of cerebrospinal fluid (CSF) between the spinal and the intracranial subarachnoid compartments. As a result, spinal CSF is driven into the spinal cord through the perivascular spaces to form a syrinx. These theories are implausible biophysically because none postulates a pump adequate to drive fluid through these spaces. None of the theories can explain why syrinx pressure is higher than CSF pressure; why extensive gliosis, edema, and vascular wall thickening regularly occur; and why the composition of syrinx fluid is not identical with that of CSF. A new theory of pathogenesis is proposed to address these difficulties. In the presence of subarachnoid obstruction at the foramen magnum, a variety of activities, such as assuming the erect posture, coughing or straining, and pulsatile fluctuations of CSF pressure during the cardiac cycle, produce transiently higher CSF pressure above the block than below it. There are corresponding changes in transmural venous and capillary pressure favoring dilation of vessels below the block and collapse of vessels above the block. The spatially uneven change of vessel caliber produces mechanical stress on the spinal cord, particularly caudal to the block. The mechanical stress, coupled with venous and capillary dilation, partially disrupt the blood-spinal cord barrier, allowing ultrafiltration of crystalloids and accumulation of a protein-poor fluid. The proposed theory is consistent with the neuropathological findings in syringomyelia and with the pressure and composition of syrinx fluid. It also accounts for the prolonged course of syringomyelia and its aggravation by cough, strain, and assumption of an erect posture. It contributes to understanding the low incidence and the morphology of syringobulbia. It explains the poorly understood presentation of foramen magnum meningiomas with symptoms of a mid- to low-cervical myelopathy. The theory also affords an understanding of the late recurrence of symptoms in children with hydromyelia who are treated with a ventricular shunt

Jacks and Miller review the clinical significance and physiology of spontaneous retinal vein pulsations (SVPs). SVPs occur in the terminal segments of the retinal veins . . . Covering: Jacks AS and Miller NR., J Neurol Neurosurg Psychiatry 2003 Jan; 74:7-9

The pathophysiology of lumbar puncture headache (LPH) is still unclear. There is evidence that leakage of cerebrospinal fluid (CSF) leads to CSF hypotension, which causes dilation of intracranial veins, resulting in LPH. However, CSF leaks at the skull base are not associated with orthostatic headache; there is poor correlation between recumbent CSF pressure and LPH; and there has been no satisfactory explanation of how venous dilation causes orthostatic headache. We propose the hypothesis that LPH is caused by an abnormal distribution of craniospinal elasticity. Increased compliance at the lumbar end of the spinal CSF space, resulting both from anatomic joining of the subarachnoid to the epidural space and from reduced CSF filling pressure, causes the hydrostatic indifferent point to move caudally, creating additional intracranial hypotension and venous dilation in the erect position. We are, thus, able to explain the orthostatic character of LPH, the fact that spinal but not cranial sites of leakage produce orthostatic headache and the imperfect correlations both between recumbent CSF pressure and LPH and between reduced CSF volume and LPH. The near absence of LPH in the very young and in the elderly relates to the relative stiffness of the epidural space at these ages. Epidural injections of blood or saline give immediate relief by reducing epidural distensibility

An 'alien hand' moves in a seemingly purposeful way but interferes with, or is irrelevant to, intended activity. The patient may want milk, but the . . . Covering: Fisher CM., Can J Neurol Sci 2000 Aug ; 27:192-203