Spinal Lipomas

Jeffrey P. Blount, MD, and Scott Elton, MD, Division of Neurosurgery, University of Alabama at Birmingham, Children's Hospital of Alabama, Birmingham, Alabama

Neurosurg Focus. 2001;10(1) 

In This Article

Other Possible Causes of Neurological Deterioration

Perhaps there are additional mechanisms operating in the setting of a tethered cord that may cause injury to neural tissue. One such possibility is that the tethering adversely affects the cord's capability to move and, thus, diminishes the impact of the pulsations of the CSF. The cord normally hangs free in the subarachnoid space and is fixed only superiorly at the level of the foramen magnum. Lateral fixation by the dentate ligaments is minimally restrictive. As such, it is anticipated that the normal cord moves freely. If the cord becomes distally fixated by a tethering mechanism, then one can speculate that the free movement of the cord may become reduced and, thus, that the cord may have to absorb fluid dynamic stresses imparted by the pulsatile CSF. Such stresses may otherwise have been dampened by cord movement. Perhaps there are fluid dynamic waves that act constructively to increase the degree of insult on the cord. The cumulative impact of a CSF pressure wave -- associated with thousands or millions of heartbeats in the setting of a fixed cord -- could conceivably, over time, impart neurological damage. This hypothesis does not negate or disprove previous notions of the cause of tethering-induced cord dysfunction. Indeed, the impact of fluid dynamics may be more important in a cord already compromised by mechanical sheer forces or ischemia.

The variability of neurological decline could be attributed to differences in CSF flow dynamics and tethered cord in affected individuals. Clearly the patterns of pressure waves in the spinal CSF are highly complex and related to multiple factors, including the relative size of cord and canal, cord vasculature, and the fixation points of the cord. There is likely adequate variability to account for the disparate symptoms observed in clinical practice. Although the typical scenario would involve neurological decline, there could conceivably be those individuals in whom the pattern of tethering allowed the cord to move adequately to diminsh the pulsations of the CSF.

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