Title:
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Development of a novel technique
to measure and characterise
spinal cord perfusion pressure in
patients with acute traumatic spinal cord injury
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Background
There is no method in clinical use for measuring intraspinal pressure (ISP) and spinal
cord perfusion pressure (SCPP) after traumatic spinal cord injury (TSCI) in humans.
I hypothesised monitoring ISP and optimising SCPP may improve spinal cord function
after injury. The thesis was performed in three stages.
Methods
(1) I ascertained the views of consultant neurosurgeons and neuroanaesthetists on
the acute management of TSCI , via a survey. (2) A pressure probe was placed
subdurally at the injury site in 18 patients with severe TSCI. Recording commenced
within 72 hours of injury and continued for up to one week. Spinal cord blood flow was
assessed using indocyanine green fluorescence, and spinal cord function using a
limb motor score, motor evoked potentials (MEPs) and an index of autoregulation
(sPRx). I explored the effect of different treatments on SCPP. (3) 134 magnetic
resonance (MR) scans from 93 TSCI patients were analysed. In 14 patients with
motor complete TSCI, I evaluated the effect of laminectomy on ISP, SCPP and
compensatory reserve (sRAP).
Results
(1) The acute management of TSCI by U.K. neurosurgeons and neuroanaesthetists
is highly variable, both surgically and in intensive care. (2) There were no procedure
related complications with ISP monitoring. ISP was higher in 18 TSCI patients
compared to 12 subjects without TSCI. Changes in PC02, sevoflurane concentration
and mannitol administration had no significant effect on ISP or SCPP. Inotropes
increased ISP with a net increase in SCPP. Increasing SCPP increased MEP
amplitude and ICG fluorescence in some patients. (3) On MR, 26% TSCI patients had
dural compression. Compared with intact lamina patients, the laminectomy group
had lower ISP, comparable SCPP and comparable sRAP. In the laminectomy group,
ISP remained high (>20mmHg) 41% of the time, and SCPP low «60mmHg) 24% of
the time.
Conclusions
I provide proof-of-principle that subdural intraspinal pressure at the injury site can be
measured with low risk after TSCI. Optimising SCPP improves motor function in some
patients. The dura is responsible for spinal cord compression in a quarter of patients.
Though bony realignment with laminectomy reduces ISP, it does not effectively
decompress the spinal cord and does not increase spinal cord perfusion.
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