Cases of improvement from the “minimally conscious state” are more plausible than those from the vegetative state. Contrasting the notion that late recovery is exceptional, a case series reported by Estraneo and colleagues of 50 consecutive patients in PVS for a year, 10 showed improvement at an average of 2 years but all were severely impaired. In the series by Luaté and coworkers, none of 12 vegetative patients improved at 5 years but 13 of 39 minimally conscious cases emerged to consciousness with severe disability. Of course, the application of these terms to a patient often leads to the withdrawal of care, and a self-fulfilling poor prognosis. This is a much discussed problem that has not been satisfactorily addressed but it emphasizes that simply labeling patients with PVS or MCS has implications for accurately assessing the natural history of some diseases.
Among recent therapeutic observations, one observation has come from Schiff and colleagues, who were able to improve function by stimulating the medial (intralaminar) thalamic nuclei through implanted electrodes in a patient who had been initially vegetative and had made a natural transition to a minimally conscious state after traumatic brain injury. Longer periods of eye opening and increased responses to execute commands, such as bringing a cup to his mouth, were observed, including, for the first time since his injury, intelligible verbalization. The authors point out that this individual had preserved language cortex and connections between thalamus and cortex. Whether this remarkable result is generalizable is not known.
It must be remarked that the degree of disability that families find acceptable varies greatly and leads to difficult decisions regarding the continuation of medical care. The knowledgeable, sympathetic, and flexible physician is in the best position to offer perspective and guide these matters over the long periods of time required, as discussed at the end of this chapter.
The states of coma described above and the vegetative state must be distinguished from a syndrome in which there is little or no disturbance of consciousness, but only an inability of the patient to respond adequately with motor activity and speech. This condition is referred to as the locked-in syndrome or the deefferented state. The term pseudocoma as a synonym for this state is best avoided, because it is used by some physicians to connote the unconsciousness of the hysteric or malingerer, the dissociative state, or catatonia. The locked-in syndrome is most often caused by a large lesion of the ventral pons (basis pontis), usually as a result of occlusion of the basilar artery. Such infarctions spare both the somatosensory pathways, and the ascending neuronal systems responsible for arousal and wakefulness, as well as certain midbrain elements that allow the eyelids to be raised in wakefulness. The damage essentially completely interrupts the descending corticobulbar and corticospinal tracts, depriving the patient of speech and the capacity to respond in any way except by voluntary vertical gaze and by blinking. Severe motor neuropathy (e.g., Guillain-Barré syndrome), pontine myelinolysis, or periodic paralysis may produce a similar effect.
One could logically refer to the locked-in state as akinetic mutism insofar as the patient is akinetic (motionless) and mute, but this is not the sense in which the term was originally used by Cairns and colleagues, who described a patient who gave the appearance of being awake but was unresponsive (actually, their patient was able to answer in whispered monosyllables). Following each of several drainings of a third ventricular cyst, the patient again became responsive but had no memory of events that had taken place when she was in the akinetic mute state. This state of apparent vigilance in an imperceptive and unresponsive patient has been referred to by French authors as coma vigile, but this is also confusing because the same term has been applied to the vegetative state.