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Using a hierarchical approach to investigate residual auditory cognition in persistent vegetative state.

Persistent vegetative state is arguably one of the least understood and most ethically troublesome neurological conditions in modern medicine. The term describes a rare disorder in which patients who emerge from coma appear to be awake, but show no signs of awareness. In recent years, a number of studies have demonstrated an important role for functional neuroimaging in the identification of residual cognitive function in patients meeting the clinical criteria for persistent vegetative state. Such studies, when successful, may be particularly useful where there is a concern about the accuracy of the diagnosis and the possibility that residual cognitive function has remained undetected. Unfortunately, functional neuroimaging in persistent vegetative state is extremely complex and subject to numerous methodological, clinical and theoretical difficulties. In this chapter, we argue that in order to most effectively define the degree and extent of preserved cognitive function in persistent vegetative state, a hierarchical approach to cognition is required. To illustrate this point, a series of functional neuroimaging paradigms in the auditory domain are described, which systematically increase in complexity in terms of the auditory and/or linguistic processes required and, therefore, the degree of preserved cognition that can be inferred from "normal" patterns of activation in persistent vegetative patients. Preliminary results in a small series of patients provide a strong basis for the systematic study of possible residual cognitive function in persistent vegetative state.

Auditory Perception↗

Legal consequences and ethical dilemmas of pain perception in persistent vegetative states.

"Persistent vegetative state" (PVS) describes brain-damaged patients who survive their injuries in a sleeplike, insensible state, with periodic awakenings. Due to technological advances, such individuals can sustain biological existence for prolonged periods of time. Their existence results in a dichotomy between the legal and medical interpretations of persistent vegetative states, giving rise to ethical conflicts. The author reviews the limitations in our understanding of what PVS signifies for the afflicted individual, and explores the conflicts arising from such limitations that may impact an individual's right to live or die. The author concludes that the medical community has yet to adopt consistent clinical criteria to diagnose PVS and that a universal standard for PVS is needed to avoid the abuse of vegetative individuals' rights.

Brain Death↗

Epidemiological studies on patients with a persistent vegetative state.

Persistent vegetative state after severe brain damage was studied epidemiologically in 110 cases from 1973 to 1976. The causes of brain damage were varied. More than one-third of the cases were due to trauma, and about one-fifth were the result of vascular accidents. Three year observation revealed that 65% of the patients died during this period. Mean survival time for dead patients was 38 months. Reactivity, clinical signs, EEG findings, methods of management, and results of various trials of treatment were investigated in connection with the patient's prognosis.

Adolescent↗

Cortical processing of noxious somatosensory stimuli in the persistent vegetative state.

The persistent vegetative state (PVS) is a devastating medical condition characterized by preserved wakefulness contrasting with absent voluntary interaction with the environment. We used positron emission tomography to assess the central processing of noxious somatosensory stimuli in the PVS. Changes in regional cerebral blood flow were measured during high-intensity electrical stimulation of the median nerve compared with rest in 15 nonsedated patients and in 15 healthy controls. Evoked potentials were recorded simultaneously. The stimuli were experienced as highly unpleasant to painful in controls. Brain glucose metabolism was also studied with [(18)F]fluorodeoxyglucose in resting conditions. In PVS patients, overall cerebral metabolism was 40% of normal values. Nevertheless, noxious somatosensory stimulation-activated midbrain, contralateral thalamus, and primary somatosensory cortex in each and every PVS patient, even in the absence of detectable cortical evoked potentials. Secondary somatosensory, bilateral insular, posterior parietal, and anterior cingulate cortices did not show activation in any patient. Moreover, in PVS patients, the activated primary somatosensory cortex was functionally disconnected from secondary somatosensory, bilateral posterior parietal, premotor, polysensory superior temporal, and prefrontal cortices. In conclusion, somatosensory stimulation of PVS patients, at intensities that elicited pain in controls, resulted in increased neuronal activity in primary somatosensory cortex, even if resting brain metabolism was severely impaired. However, this activation of primary cortex seems to be isolated and dissociated from higher-order associative cortices.

Adult↗

Life expectancy of children in a persistent vegetative state.

The persistent vegetative state (PVS) is a state of wakeful unconsciousness occurring in adults and children. Despite preservation of vegetative functions, PVS patients have a shortened life-span, although accurate information concerning this issue remains limited. The survival of children in PVS was examined to determine whether age, etiology of the vegetative state, or type of residence in which the patient lived affected the estimated survival. The data of 155,851 developmentally disabled California state residents were reviewed using the Client Development Evaluation Report (CDER). Criteria from the CDER were selected to define the vegetative state and included: lack of interaction with peers; absence of auditory, visual, and expressive or receptive language function; no hand or arm use; inability to eat, sit, roll over, or lift head; and no bowel or bladder control. There were 847 patients who met these criteria on the initial and follow-up CDERs. A product limit survival model was used to develop survival curves and to calculate the median survival time for patients grouped by age, etiology, and type of residence. Median survival (yrs) for patients who remained in PVS for the following age groups was: < 1 yr: 2.6, 1 < 2 yrs: 4.2, 2-6 yrs: 5.2, 7-18 yrs: 7.0, > or = 19 yrs: 9.9. Median survival based on etiology varied from 3.0 to 8.6 years; no consistent relationship existed between etiology and duration of survival. Survival (yrs) for patients younger than age 18 years based on type of residence included: own home: 4.5, institutions: 5.2, skilled nursing facility/private hospital: 3.2, and other community care facilities: 3.7.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗

Auditory processing in severely brain injured patients: differences between the minimally conscious state and the persistent vegetative state.

BACKGROUND: The minimally conscious state (MCS) is a recently defined clinical condition; it differs from the persistent vegetative state (PVS) by the presence of inconsistent, but clearly discernible, behavioral evidence of consciousness. OBJECTIVE: To study auditory processing among patients who are in an MCS, patients who are in a PVS, and healthy control subjects. METHODS: By means of (15)O-radiolabeled water-positron emission tomography, we measured changes in regional cerebral blood flow induced by auditory click stimuli in 5 patients in an MCS, 15 patients in a PVS, and 18 healthy controls. RESULTS: In both patients in an MCS and the healthy controls, auditory stimulation activated bilateral superior temporal gyri (Brodmann areas 41, 42, and 22). In patients in a PVS, the activation was restricted to Brodmann areas 41 and 42 bilaterally. We also showed that, compared with patients in a PVS, patients in an MCS demonstrated a stronger functional connectivity between the secondary auditory cortex and temporal and prefrontal association cortices. CONCLUSIONS: Although assumptions about the level of consciousness in severely brain injured patients are difficult to make, our findings suggest that the cerebral activity observed in patients in an MCS is more likely to lead to higher-order integrative processes, thought to be necessary for the gain of conscious auditory perception.

Acoustic Stimulation↗

[Role of multimodal evoked potentials in evaluations of persistent vegetative state of nontraumatic origin].

Persistent vegetative state (PVS) is a kind of release from coma, manifesting by absence of any signs of cognitive activity. Progress in reanimatology leads to an increase in the number of patients with PVS, thus creating a new medical and social problem. Study of atraumatic PVS acquires special importance because of a drastic increase in its incidence, necessitating definition of criteria of this state formation and its prognostic signs. Multimodal evoked potentials (MEP) now play an important role in diagnosis and prediction of PVS. The impact of acoustic stem (ASEP), visual (VEP), somatosensory (SSEP), and cognitive (CEP) evoked potentials is analyzed and early diagnostic and prognostic neurophysiological criteria are defined. Results of dynamic examinations of 23 patients (9 men and 14 women) aged 10-67 years with atraumatic PVS are presented. According to neurophysiological data, PVS in the majority of patients is characterized by absence of cognitive responses to a significant stimulus (wave P300) during examinations of CEP and of cortical response during examination of SSEP. VEP and long latent acoustic evoked potentials are as rule intact in atraumatic PVS. According to ASEP, stem functions were intact or slightly changed in the examined patients with PVS. Prognostically unfavorable and relatively favorable signs in the time course of MEP are defined.

Adolescent↗

Deep brain stimulation therapy for a persistent vegetative state.

Twenty cases of a persistent vegetative state (PVS) caused by various kinds of brain damage were neurologically and electrophysiologically evaluated at 3 months after persistence of the PVS, and were treated by deep brain stimulation (DBS) therapy. The stimulation sites were the mesencephalic reticular formation (2 cases) and CM-pf complex (18 cases). Seven of the patients emerged from the PVS, and became able to obey verbal commands. However, they remained in a bedridden state. These 7 cases revealed a desynchronization or slight desynchronization pattern on continuous EEG frequency analysis. The Vth wave of ABR and N20 of SEP could be recorded even with a prolonged latency, and the pain-related P250 was recorded with an amplitude of over 7 microV. We conclude that chronic DBS therapy may be useful for allowing the patient to emerge from a PVS, if the candidates are selected according to the neurophysiological criteria. In view of the severely disabled state of the patients who emerged from the PVS, a special rehabilitation program which includes neurostimulation therapy may be necessary for treatment of the PVS.

Adult↗

Impairment of non-specific immunity in patients in persistent vegetative state.

In fourteen patients in persistent vegetative state (PVS) immune responsiveness was investigated. In particular, we studied the relationship between brain lesions following traumatic injury and immune system. In this respect, phagocytosis and killing of Candida albicans by polymorphonuclear cells (PMN) and monocytes were tested. In addition serum levels of Interferon-gamma (IFN-gamma) were evaluated. The patients come out from PVS by 3-4 month were used as control group. Data shown a profound impairement of phagocytosis and killing of monocytes and low serum levels of IFN gamma when compared with normal values. Taken together, these findings suggest that brain lesions, may affect non-specific immune response.

Adolescent↗

Three-piece oral appliance with herbst attachments for persistent vegetative state patient with sleep-disordered breathing.

PURPOSE: Persistent vegetative state is a form of wakefulness without awareness. This report describes a dental appliance for the treatment of sleep breathing disorders in this condition. The device can be easily inserted and removed by the patient's family or nurse. MATERIALS AND METHODS: A 19-year-old woman had been in a persistent vegetative state since having hypoxic-ischemic encephalopathy because of cardiopulmonary arrest. Although she exhibited a sleep-wake cycle and normal respiration, she had sleep apnea and snoring, and produced snoring-like sounds even in an awake state. A three-piece device with Herbst attachments was fabricated to treat the symptoms. Overnight sleep studies were carried out to evaluate the effectiveness of the appliance. RESULTS: The device could be handled by the patient's family. Snoring was satisfactorily reduced after insertion of the device. Sleep apnea, desaturation, and minimal oxygen saturation were markedly improved. CONCLUSION: If the family of a persistent vegetative state patient wishes to treat sleep-disordered breathing, the appliance may be helpful as an alternative to relieve the symptoms. The device could be applied for sleep apnea patients who experience difficulties using other types of oral appliances.

Adult↗

Detecting residual cognitive function in persistent vegetative state.

Despite converging agreement about the definition of persistent vegetative state, recent reports have raised concerns about the accuracy of diagnosis in some patients, and the extent to which, in a selection of cases, residual cognitive functions may remain undetected. Objective assessment of residual cognitive function can be extremely difficult as motor responses may be minimal, inconsistent, and difficult to document in many patients, or may be undetectable in others because no cognitive output is possible. Here we describe strategies for using H(2)(15)O positron emission tomography activation studies to study covert cognitive processing in patients with a clinical diagnosis of persistent vegetative state. Three cases are described in detail. Of these, two exhibited clear and predicted regional cerebral blood flow responses during well-documented activation paradigms (face recognition and speech perception) which have been shown to produce specific, robust and reproducible activation patterns in normal volunteers. Some months after scanning, both patients made a significant recovery. In a third case, blood flow data were acquired during a speech perception task, although methodological difficulties precluded any systematic interpretation of the results. In spite of the multiple logistic and procedural problems involved, these results have major clinical and scientific implications and provide a strong basis for the systematic study of possible residual cognitive function in patients diagnosed as being in a persistent vegetative state.

Adult↗

The persistent vegetative state: an analysis of clinical correlates and costs.

A review was compiled of 23 patients in the persistent vegetative state; a condition that developed while the patients were in an acute care hospital. Before the onset of the persistent vegetative state, eight patients had had dementia, 11 were functionally dependent, and seven had neurologic disorders that gradually led to the persistent vegetative state. For patients in the persistent vegetative state, three types of mechanical support--respirators, nasogastric or gastrotomy tubes, and intravenous lines--were utilized. All three were necessary in 43% of patients, two types in 52%, and one type in 4%. All patients in the persistent vegetative state required at least one type of mechanical assistance. Their course was complicated in all cases by incontinence, and in the majority, by decubiti, pneumonia, and urinary tract infection. Only one patient improved enough to be able to say a few words. These patients required active medical care and invasive procedures that were costly but futile. The hospital bills obtained for 13 patients averaged $170,000, and the length of stay for all patients averaged 197 days, the equivalent to a total number of bed-days of 12.5 bed-years. The poor outcomes, requirements for mechanical support, and frequency of complications--especially when neurologic impairments were present before the onset of the persistent vegetative state--should be considered when evaluating the cost in hospital bills and bed occupancy.

Adult↗

Persistent vegetative state: important considerations for the neuroscience nurse.

Persistent vegetative state is a rare condition but one which evokes many emotional, psychosocial, bioethical, legal and economic concerns. Because neuroscience nurses are among the caregivers most likely to be involved in caring for patients in PVS, they need to be knowledgeable in the diagnosis, prognosis and ethical management of these patients and be able to assist families, loved ones and surrogates make informed decisions about treatment choices.

Adult↗

Anaesthetic management of a pregnant patient in a persistent vegetative state.

Pregnancy in a patient in a persistent vegetative state presents challenging therapeutic questions about the level of supportive management required, the assessment of fetal well-being, the timing and mode of delivery and the anaesthetic management of labour and delivery. We report the case of a 29-yr-old woman who had a favourable fetal outcome despite suffering hypoxic brain damage after a suicide attempt by a drug overdose. She was managed until the onset of labour on an intensive care unit and had a spontaneous vaginal delivery assisted by epidural anaesthesia.

Adult↗