Coma

Andrew Baker

Coma: disorder of consciousness

• Critical and ultimate component of health

• Components include:• Alertness

• Attention

• Awareness

1946

1968

1971

2002

Coma: disorder of consciousness

• Alertness (arousal)• Network of neurons: Ascending Reticular Activating

System

• Midbrain and rostral pontine tegmentum projecting to the diencephalon hypothalamus and midline and intralaminar nuclei of the thalamus – and on to projections to bilateral cortex.

• Awareness and Attention• Content of consciousness

• Sum of functions by cerebral cortical neurons and projections to and from subcortical structures

Coma: disorder of consciousness

• Upper brainstem reticular formation and related structures

• Bilateral regions of the cerebral cortex

• Bilateral lesions of the thalamus

• Vegetative State

– Wakefulness without awareness

• Sleep wake cycles; eye-open periods; lake of awareness of self or environment

• Minimally conscious state

– Severely impaired consciousness with minimal but definite behavioral evidence of self or environmental awareness

Plum and Posner

The diagnosis of stupor and coma

1966

Steven D. Colquhoun, Caroline A. Connelly

Tate, 2012

Take Home Messages

• Coma is a disorder of consciousness:

– Alertness, Attention, Awareness

• Anatomic Correlates vs. metabolic/structural

• Locked-in is not a coma-state

• SAE involves several parallel mechanisms

• Anatomy – Tracts -- BOLD -- DTI/Neuronal Pathways -- concept of the connectome

bakera@smh.ca