INTRACEREBRAL TEMPERATURE ALTERATIONS ASSOCIATED WITH FOCAL SEIZURES
Abstract number :
1.033
Submission category :
Year :
2002
Submission ID :
3438
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Xiao-Feng Yang, Steven M. Rothman, Jong Hee Chang. Neurology, Washington University School of Medicine, St. Louis, MO; Neurology and Epilepsy Center, St. Louis Children[ssquote]s Hospital, St. Louis, MO; Neurological Surgery, Washington University School
RATIONALE: Because focal seizures produce an increase in cerebral blood flow and metabolic activity, they might also change brain temperature and, thereby, alter seizure susceptibility.
METHODS: We induced focal neocortical seizures in halothane-anesthetized rats by microinjection of 4-aminopyridine (4-AP; 0.5 [mu]l of a 25 mM solution) and measured the temperature over the site of convulsant injection with a miniature thermocouple. In some experiments, relative blood flow was monitored with a laser Doppler probe (Laserflo Blood Perfusion Monitor, TSI).
RESULTS: In control animals, brain and rectal temperature remained constant at 33.5 and 37.2[degree] C, respectively, over a two hour period. In animals treated with 4-AP to induce focal seizures, brain temperature rose an average of 0.3[degree] C within a few seconds of seizure onset, while rectal temperature remained constant. This temperature elevation was preceded by an increase in cortical blood flow. Brain temperature, but not blood flow, was also elevated eight mm away from the seizure focus. When blood flow was increased independently of neuronal activity, by elevating pCO[sub]2[/sub], brain temperature also rose by about 0.3[degree] C. We did not detect any change in seizure durations, when we used a Peltier device to [italic]elevate[/italic] focal cortical temperature 1[degree] C, so the functional significance of this 0.3[degree] C temperature rise is unclear.
CONCLUSIONS: Focal neocortical seizures in rats produce a small, but statistically significant increase in local brain temperature. This temperature increase is the result of increased blood flow that [dsquote]clamps[dsquote] brain temperature close to body temperature. In humans, seizures might cause a [italic]reduction[/italic] in brain temperature, because brain temperature is normally higher than body temperature. While the functional significance, if any, of this small elevation of brain temperature induced by focal seizures is unclear, this may be the first direct demonstration that elevation of physiological brain activity can alter brain temperature.
[Supported by: Citizens United for Research in Epilepsy, Inc. (CURE), the Stein Fund for Pediatric Neurology Research, and NS14834 from the NIH.]