Coma - A Classical Disorder of Consciousness

Three years ago Michael Schumacher suffered a traumatic brain injury during a skiing accident and was put into a medically induced coma. Mid 2014 he was showing "moments of consciousness" and moved from intensive care into a rehabilitation ward. In November 2014, it was reported that Schumacher was "paralysed and in a wheelchair"; he "cannot speak and has memory problems". Not much more is known about his beeing. Let's have a closer look at this disorder of concisousness.


Every now and then, popular media reports stories of miraculous coma recoveries. Even in modern and motor criteria [1].

Michael Schumacher 2010  by ph-stop via flickr

neurology, disorders of consciousness are little understood and among the least curable. They are classified into coma, vegetative state, and minimally conscious state [1]. Coma is characterized by a lack of arousal and wakefulness - patients do not respond to even rigorous stimulation, whereas the vegetative state is marked by wakefulness without awareness. The minimally conscious state is characterized by a minimal but obvious behavioural evidence of awareness. To assess the conscious state of a patient, the Glasgow coma scale is used to classify the severity of unconsciousness based on eye opening, verbal response,
Coma may occur after functional impairments from toxic or metabolic causes, or structural injuries such as lesions of the ascending reticular activating system (connecting the upper brainstem to the cortex). Coma prognosis is determined by the etiology and severity of injury [2]. If applicable, treatment consists of a reversal of the cause, e.g. stopping brain swelling or reversing metabolic abnormalities.

COMA  CAN LAST FROM HOURS TO YEARS

Most coma patients regain consciousness over hours to weeks, while others transition into a vegetative state. Recovery is usually gradual, and seldom leads to full neurological recovery. Patients acquire more and more of their former abilities but are often left with residual cognitive impairment. Physiological recovery depends on functional restoration of cortico-thalamo-cortical connections, restoration of a neurotransmitter balance and recovery of neuronal plasticity [2].
To date, there is no accepted pharmacological therapy for coma patients, but recent studies suggest that some drugs may contribute to consciousness recovery by restoring neurotransmitter balances, leading to an increase in synaptic plasticity and functional connectivity [3]. Among them are CNS stimulants such as some antidepressants and dopaminergic agents, for example amantadine, but also CNS depressants such as zolpidem - having a rather acute effect suggesting rapid neurotransmitter changes, or baclofen - likely playing a role in plasticity and reported to result in dramatic recovery from the vegetative state [3].
In summary, coma is a severe disorder of consciousness that can last from hours to years. Ongoing research is investigating what happens in the damaged brain during recovery and how drugs can induce recuperation from disorders of consciousness.


[1] Bernat, Lancet, 2006
[2] Goldfine and Schiff, Neurol Clin, 2011
[3] Pistoia et al, CNS Drugs, 2010


by Claudia Willmes, PhD Student AG Eickholt / AG Schmitz
this articel was originally published March 2014 in Volume 07, Issue 1"Mind and Brain".