Each patient partially preserved restricted sensory representations, as evidenced by slow evoked magnetic fields and gamma band activity. In two patients, these activations correlate with isolated behavioral patterns and metabolic activity. Remaining active regions identified in the three PVS patients with behavioral fragments appear to consist of segregated corticothalamic networks that retain connectivity and partial functional integrity. A single patient who sustained severe injury to the tegmental mesencephalon and paramedian thalamus showed widely preserved cortical metabolism, and a global average metabolic rate of 65% of normal. The relatively high preservation of cortical metabolism in this patient defines the first functional correlate of clinical–pathological reports associating permanent unconsciousness with structural damage to these regions. The specific patterns of preserved metabolic activity identified in these patients reflect novel evidence of the modular nature of individual functional networks that underlie conscious brain function. The variations in cerebral metabolism in chronic PVS patients indicate that some cerebral regions can retain partial function in catastrophically injured brains. Misdiagnoses
Statistical PVS misdiagnosis is common. An example study with 40 patients in the United Kingdom reported 43% of their patients classified as PVS were believed so and another 33% had recovered whilst the study was underway. Some PVS cases may actually be a misdiagnosis of patients being in an undiagnosed minimally conscious state. Since the exact diagnostic criteria of the minimally conscious state were only formulated in 2002, there may be chronic patients diagnosed as PVS before the secondary notion of the minimally conscious state became known.
Professor Geraint Rees, Director of the Institute of Cognitive Neuroscience at University College London, responded to the study by observing that, "As a clinician, it would be important to satisfy oneself that the individual that you are communicating with is competent to make those decisions. At the moment it is premature to conclude that the individual able to answer 5 out of 6 yes/no questions is fully conscious like you or I." In contrast, Jacob M. Appel of the Mount Sinai Hospital told the Telegraph that this development could be a welcome step toward clarifying the wishes of such patients. Appel stated: "I see no reason why, if we are truly convinced such patients are communicating, society should not honour their wishes. In fact, as a physician, I think a compelling case can be made that doctors have an ethical obligation to assist such patients by removing treatment. I suspect that, if such individuals are indeed trapped in their bodies, they may be living in great torment and will request to have their care terminated or even active euthanasia."