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Biomedical subjects

G Mezger

Publications and source records attributed to G Mezger.

5 recordsLinked to original sources
PubMed2005

Information processing in severe disorders of consciousness: vegetative state and minimally conscious state.

OBJECTIVE: To study the presence of electrophysiological indicators of remaining cortical functions in patients with persistent vegetative state (PVS) and minimally conscious state (MCS). Previous electrophysiological and PET data indicated that some PVS patients have partially intact cortical processing functions. However, it remains unclear whether the reported patients were representative for PVS population or just some exceptional cases. METHODS: Event-related brain responses to stimuli of different complexity levels, recorded in 98 patients with extremely severe diffuse brain injuries, 50 of which in PVS. Four main indicators of cortical functions were: (i) N1-P2 complex as an index of simple, undifferentiated cortical processing; (ii) mismatch negativity as an index of pre-attentive, probably unconscious, cortical orientation; (iii) P3 wave as an index of deep cortical analysis of physical stimuli, and (iv) brain responses to semantic stimuli. RESULTS: Cortical responses were found in all PVS patients with a background EEG activity > 4 Hz. All responses investigated, including those to semantic stimuli that indicated comprehension of meaning, occurred significantly above chance, though less frequently than in patients with severe brain injuries who were conscious. CONCLUSIONS: Cortical responses were lacking in most patients with severe EEG slowing (< 4 Hz). Follow-up data revealed that the presence of a mismatch negativity, a short disease duration, and the traumatic etiology were related to a better outcome. SIGNIFICANCE: The data show that in a subpopulation of PVS patients with preserved thalamocortical feedback connections, remaining cortical information processing is a consistent finding and may even involve semantic levels of processing.

Auditory Cortex↗
PubMed2001

Brain potentials in human patients with extremely severe diffuse brain damage.

To test higher cortical functions of neurological patients, oddball tasks are often used in which a frequent and a rare stimulus are randomly presented and a P3 brain wave is recorded to the rare stimulus. We examined 33 patients with extremely severe brain injury. Three oddball conditions were used: with two sine tones (ST), with two complex tones (CT) and with vowels 'o' and 'i'. Across all patients, CT elicited P3 more often than ST, and the occurrence of the P3 after vowels was intermediate. However, among patients who showed a distinct P3 wave, its amplitude in the subgroup with traumatic brain injury was larger to vowels than to CT. In patients with non-traumatic etiology, CT and vowels elicited a P3 of a nearly equal amplitude. Stimuli of sufficient complexity should be used when the P3 technique is applied for assessment of cortical functions in severely impaired patients.

Adolescent↗
PubMed1988

[Rehabilitation prognosis of aphasias of various etiologies with reference to clinical, neurolinguistic and computerized tomography findings].

To obtain further insights into the rehabilitation outlook in different baseline conditions, a comparison was made of data and treatment outcomes in 92 patients having aphasias of different etiology and disease duration. Rating as "improved" was contingent on significant changes in at least 2 subtests of the AAT (Aachener Aphasietest), which is a fairly stringent requirement. This criterion was met by some 35% of the patients overall, independent of their age; the percentage increased to 45% in case of treatment onset during the first year, while in later onset, significant improvement was achieved in 15% only. Aphasic syndromes secondary to hemorrhage, trauma, tumors, or infections, usually are less severe than the predominant classical syndromes, i.e. Global, Broca and Wernicke aphasia, caused by ischemic stroke. CT lesion size did not yield any definite information. Minor improvements below the required significance levels, and, above all, gains in communication performance, i.e. further consolidation, could be achieved by appropriate management even after the crucial initial year, which, however, does not imply any fundamental changes in the rehabilitation prognosis as such.

Aphasia↗