Visual fixation in the vegetative state: an observational case series PET study.
BACKGROUND
Assessment of visual fixation is commonly used in the clinical examination of patients with disorders of consciousness. However, different international guidelines seem to disagree whether fixation is compatible with the diagnosis of the vegetative state (i.e., represents "automatic" subcortical processing) or is a sufficient sign of consciousness and higher order cortical processing.


METHODS
We here studied cerebral metabolism in ten patients with chronic post-anoxic encephalopathy and 39 age-matched healthy controls. Five patients were in a vegetative state (without fixation) and five presented visual fixation but otherwise showed all criteria typical of the vegetative state. Patients were matched for age, etiology and time since insult and were followed by repeated Coma Recovery Scale-Revised (CRS-R) assessments for at least 1 year. Sustained visual fixation was considered as present when the eyes refixated a moving target for more than 2 seconds as defined by CRS-R criteria.


RESULTS
Patients without fixation showed metabolic dysfunction in a widespread fronto-parietal cortical network (with only sparing of the brainstem and cerebellum) which was not different from the brain function seen in patients with visual fixation. Cortico-cortical functional connectivity with visual cortex showed no difference between both patient groups. Recovery rates did not differ between patients without or with fixation (none of the patients showed good outcome).


CONCLUSIONS
Our findings suggest that sustained visual fixation in (non-traumatic) disorders of consciousness does not necessarily reflect consciousness and higher order cortical brain function.
Bruno
Marie-Aurélie
MA
Coma Science Group and Cyclotron Research Centre, University of Liège, Liège, Belgium.
Vanhaudenhuyse
Audrey
A
Schnakers
Caroline
C
Boly
Mélanie
M
Gosseries
Olivia
O
Demertzi
Athena
A
Majerus
Steve
S
Moonen
Gustave
G
Hustinx
Roland
R
Laureys
Steven
S
D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism*; D001927:Brain Diseases / Q000000981:diagnostic imaging / Q000209:etiology / Q000378:metabolism*; D001931:Brain Mapping; D016022:Case-Control Studies; D002908:Chronic Disease; D003243:Consciousness; D005260:Female; D005403:Fixation, Ocular; D005500:Follow-Up Studies; D005947:Glucose / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000150:complications; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination; D018458:Persistent Vegetative State / Q000000981:diagnostic imaging / Q000209:etiology / Q000378:metabolism*; D049268:Positron-Emission Tomography; D020127:Recovery of Function; D013997:Time Factors
D005947:Glucose