Cerebral processing in the minimally conscious state

Abstract

Abstract-We studied a patient in a minimally conscious state using PET and cognitive evoked potentials. Cerebral metabolism was below half of normal values. Auditory stimuli with emotional valence (infant cries and the patient's own name) induced a much more widespread activation than did meaningless noise; the activation pattern was comparable with that previously obtained in controls. Cognitive potentials showed preserved P300 responses to the patient's own name. NEUROLOGY 2004;63:916 -918 Patients in a minimally conscious state (MCS) show some limited evidence of awareness of self or environment. However, caregivers of these patients have difficulties in behaviorally evaluating their level of conscious or emotional perception. By definition, MCS patients show no functional interactive verbal or nonverbal communication. 1 We report a patient in an MCS as documented by extensive and repetitive neuropsychological evaluations. Six months after admission, resting cerebral metabolic rates for glucose (CMRGlu) and regional changes in cerebral blood flow (rCBF) in response to auditory stimuli (with different emotional content and relevance) were studied using PET imaging with simultaneous recording of cognitive event-related potentials (ERPs). Materials and methods. Patient.A 42-year-old man was brought to the hospital after abrupt loss of consciousness. Brain CT showed a left frontal intracerebral hemorrhage. The hematoma was evacuated in emergency. Follow-up MRI showed multifocal bilateral frontal hypodensities, and EEG showed diffuse theta and delta activities. Somatosensory (but not visual) evoked potentials showed preserved cortical potentials. Brainstem auditory evoked potentials were normal.Six months after the insult, CMRGlu-PET, rCBF-PET, and cognitive ERP studies were performed while the patient was in an MCS and free of centrally acting drugs. Videotaped neurologic and neuropsychological assessment included the Wessex Head Injury Matrix 2 and the Western Neuro Sensory Stimulation Profile 3 and Revised Coma Recovery Scale.10 At the time of PET scanning, the patient showed spontaneous eye opening (Ͼ30 minutes), conjugate roving eye movements, and preserved visual and auditory startle reflexes. Brainstem reflexes were normal, and grasp, palmomental, and sucking reflexes were obtained. He showed a spastic quadriparesis with bilateral pyramidal signs, made no spontaneous limb movements, sporadically uttered incomprehensible (apparently meaningless) groans, fixated and tracked family members and a moving mirror, oriented toward new sounds, and inconsistently obeyed simple commands (e.g., showed his tongue when asked by his wife in three of four trials) but failed to make functional communication.Subsequent to PET and ERP studies, the patient could make intelligible vocalizations (e.g., "hello" and "mom") and later showed signs of intentional communication. Unfortunately, the patient died 30 weeks after admission from septic shock. Given that earlier he had been slowly recovering with gradually but consistentl...

Functional neuroanatomy of disorders of consciousness

“…In line with their clinical condition, patients with MCS show a partial preservation of this large-scale associative frontoparietal network [22]. Similar findings of frontoparietal deactivation have been recorded in somnambulism as well as in absence and complex partial (mainly in the temporal lobe) seizures [6][7][8], whereas temporal lobe seizures without loss of consciousness are not accompanied by these widespread changes [7].…”

Functional neuroanatomy underlying the clinical subcategorization of minimally conscious state patients

“…The identified polymodal frontoparietal network is considered critical for the emergence of conscious awareness [12]. These results corroborate previous findings on pain [13,14], auditory [15,16], and emotional [17,18] processing showing that MCS patients demonstrate a more elaborated and integrated level of noxious, auditory, and emotional processing than vegetative state patients who only showed activation of primary ''lower level'' sensory cortices which are disconnected from ''higher order'' associative cortical networks [5,14].…”

Consciousness supporting networks

“…Similar activation and connectivity changes were observed in normal conscious controls but not in VS/UWS patients were activation was limited to isolated low-level auditory cortices, functionally disconnected from the external awareness network [24]. By contrast, emotionally salient stimuli, such as baby cries and the patient's own name, led to much more widespread temporal activation also recruiting anterior and posterior midline cortices [25,26]. Similarly, in MCS patients, presentation of a story told by their mother lead to more widespread activation [27].…”