Susceptibility of Primary Sensory Cortex to Spreading Depolarizations.
Spreading depolarizations (SDs) are recognized as actors in neurological disorders as diverse as migraine and traumatic brain injury (TBI). Migraine aura involves sensory percepts, suggesting that sensory cortices might be intrinsically susceptible to SDs. We used optical imaging, MRI, and field potential and potassium electrode recordings in mice and electrocorticographic recordings in humans to determine the susceptibility of different brain regions to SDs. Optical imaging experiments in mice under isoflurane anesthesia showed that both cortical spreading depression and terminal anoxic depolarization arose preferentially in the whisker barrel region of parietal sensory cortex. MRI recordings under isoflurane, ketamine/xylazine, ketamine/isoflurane, and urethane anesthesia demonstrated that the depolarizations did not propagate from a subcortical source. Potassium concentrations showed larger increases in sensory cortex, suggesting a mechanism of susceptibility. Sensory stimulation biased the timing but not the location of depolarization onset. In humans with TBI, there was a trend toward increased incidence of SDs in parietal/temporal sensory cortex compared with other regions. In conclusion, SDs are inducible preferentially in primary sensory cortex in mice and most likely in humans. This tropism can explain the predominant sensory phenomenology of migraine aura. It also demonstrates that sensory cortices are vulnerable in brain injury.



Spreading depolarizations (SDs) are involved in neurologic disorders as diverse as migraine and traumatic brain injury. In migraine, the nature of aura symptoms suggests that sensory cortex may be preferentially susceptible. In brain injury, SDs occur at a vulnerable time, during which the issue of sensory stimulation is much debated. We show, in mouse and human, that sensory cortex is more susceptible to SDs. We find that sensory stimulation biases the timing but not the location of the depolarizations. Finally, we show a relative impairment of potassium clearance in sensory cortex, providing a potential mechanism for the susceptibility. Our data help to explain the sensory nature of the migraine aura and reveal that sensory cortices are vulnerable in brain injury.
Department of Neurology.
Volodymyr B
VB
Bogdanov
Department of Neurology.
Natalie A
NA
Middleton
Department of Neurology.
Jeremy J
JJ
Theriot
Department of Neurology, Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, Utah 84108.
Patrick D
PD
Parker
Department of Bioengineering and Small Animal Imaging, and.
Osama M
OM
Abdullah
Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90095, and.
Y Sungtaek
YS
Ju
Department of Neurosurgery, University of Cincinnati, Cincinnati, Ohio 45220.
Jed A
JA
Hartings
Department of Neurology, k.c.brennan@hsc.utah.edu.
K C
KC
Brennan
D000818:Animals; D001930:Brain Injuries / Q000503:physiopathology; D013181:Cortical Spreading Depression / Q000187:drug effects* / Q000502:physiology*; D006801:Humans; D007649:Ketamine / Q000008:administration & dosage; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008881:Migraine Disorders / Q000503:physiopathology; D011189:Potassium Chloride / Q000008:administration & dosage; D013003:Somatosensory Cortex / Q000187:drug effects*
D011189:Potassium Chloride; D007649:Ketamine
anoxic depolarization; cortical spreading depression; migraine; sensory cortex; traumatic brain injury