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Biomedical subjects

D Schmalohr

Publications and source records attributed to D Schmalohr.

6 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↗
PubMed2003

Stimulus complexity enhances auditory discrimination in patients with extremely severe brain injuries.

There is controversy as to what extent the processing of spectrally rich sounds in the human auditory cortex is related to the processing of singular frequencies. An informative index of the function of the auditory cortex, particularly important in neurological patients, is the mismatch negativity (MMN), a component of auditory event-related potentials. In the present study the MMN was recorded in 79 patients with extremely severe diffuse brain injuries, most of them in persistent vegetative state or minimal consciousness state. Both sinusoidal ('pure') and complex musical tones were used. Different statistical approaches converged in that musical tones elicited an MMN significantly more frequently, and of a larger amplitude, than simple sine tones. This implies that using simple stimuli in clinical populations may lead to a severe underestimation of the functional state of a patient's auditory system. The findings are also in line with behavioral and physiological data indicating independent processing of complex sounds in the auditory cortex.

Acoustic Stimulation↗
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↗
PubMed2001

[Early rehabilitation in Baden-Wurttemberg--a study of all Baden-Wurrtemberg early rehabilitation centers].

Over a period of 12 months, all persons among the 10.4 million inhabitants of the state of Baden-Württemberg were included in the study who had suffered severe brain damage and were treated in special early rehab units, comprising 147 beds for adults and 43 for children. With 830 patients admitted, the incidence of severe brain damage was 7.98/100.000 in adults and 1.11/100.000 in children. 50 to 70 year old patients were over-represented, those older than 70 years were underrepresented due to geriatric rehab facilities for the latter. Male patients dominated, while female were somewhat younger. 54% of the patients were admitted from the hospital which had performed primary care, with an average stay of 67 days. Average early rehab duration was 53 days (arithmetic average; median 40 days, some patients required up to one year). 32.8% of the patients had suffered traumatic brain damage (ICD 851, 852, 854) and 40.9% non-traumatic brain affection (ICD 430, 431, 433-438, 310, 348), including 12.2% CVA (ICD 433-438), 8.5% subarachnoid and 12.3% intracerebral hemorrhage. Severity as indexed by the early rehab Barthel index improved from an initial average of -119 to -34 at discharge. 80% of the patients showed an overall improvement (71% of them by up to 200 points and 46% by up to 100 points).

Adolescent↗