Critical neural targets for (the level of) human consciousness: Arousal arrest and unconsciousness after sumatriptan administration.
BACKGROUND
Insufficient understanding of the mechanisms of consciousness can make unconsciousness a diagnostic challenge, directly effecting the treatment and the outcome of the patient. Consciousness is a product of brainstem arousal (wakefulness, the level of consciousness) and cortical information integration (awareness, the contents of consciousness). The thalamus serves as a critical hub in the arousal pathway. The nuclei within the internal medullary lamina, together with the associated thalamocortical connections, have been implicated as being especially important for human consciousness.


METHODS
A 17-year old male migraineur developed a sudden episode of unconsciousness after receiving a single dose of intranasal sumatriptan for the treatment of prolonged migraine-associated symptoms. Diffusion-weighted magnetic resonance imaging revealed a small bilateral thalamic infarction affecting the centromedian and parafascicular nuclei and the associated non-specific thalamocortical connections as the likely reason for the impairment of consciousness. With the exception of occasional fatigue due to a persistent lesion on the left thalamus, the patient experienced full recovery. Corresponding to the injury, diffusion tensor tractography imaging revealed a distinctive defect on the thalamocortical fibres originating from the left centromedian/parafascicular nuclei complex.


CONCLUSIONS
The presented case offers an outstanding example of the importance of the arousal system and non-specific thalamocortical connectivity for normal waking consciousness.
a Department of Intensive Care Medicine , Tampere University Hospital , Tampere , Finland.|b Turku PET Centre, University of Turku , Turku , Finland.
Jaakko W
JW
Långsjö
c Department of Neurosciences and Rehabilitation , Tampere University Hospital , Tampere , Finland.
Kai
K
Lehtimäki
d Department of Radiology.
Jyrki
J
Ruohonen
d Department of Radiology.
Anne
A
Sajanti
e Department of Clinical Neurophysiology.|f Department of Neurology , Seinäjoki Central Hospital , Seinäjoki , Finland.
Satu
S
Sandell
e Department of Clinical Neurophysiology.
Hannu T
HT
Heikkilä
g Department of Radiology , Tampere University Hospital , Tampere , Finland.
Antti
A
Brander
h Department of Intensive Care Medicine , Seinäjoki Central Hospital , Seinäjoki , Finland.
Kari
K
Saarinen
f Department of Neurology , Seinäjoki Central Hospital , Seinäjoki , Finland.
Lauri
L
Herrala
D000293:Adolescent; D001143:Arousal / Q000187:drug effects*; D056324:Diffusion Tensor Imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008881:Migraine Disorders / Q000188:drug therapy; D018170:Sumatriptan / Q000009:adverse effects*; D013788:Thalamus / Q000000981:diagnostic imaging / Q000187:drug effects; D014474:Unconsciousness / Q000139:chemically induced* / Q000000981:diagnostic imaging; D014662:Vasoconstrictor Agents / Q000009:adverse effects*
D014662:Vasoconstrictor Agents; D018170:Sumatriptan
DBS; Intralaminar nuclei; centromedian thalamus; diffusion tensor imaging; diffusion-weighted MRI; electroencephalography; neuromodulation; stroke; thalamocortical connectivity; tractography