Article
The hibernating brain – first evidence for metabolic cerebral suppression in patients with chronic hemodynamic cerebral ischemia
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Authors
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Daniel Jussen
- Klinik für Neurochirurgie, Charité – Universitätsmedizin Berlin, Deutschland
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Anna Zdunczyk
- Klinik für Neurochirurgie, Charité – Universitätsmedizin Berlin, Deutschland
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Thomas Picht
- Klinik für Neurochirurgie, Charité – Universitätsmedizin Berlin, Deutschland
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Peter Vajkoczy
- Klinik für Neurochirurgie, Charité – Universitätsmedizin Berlin, Deutschland
| Published: | September 16, 2010 |
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Outline
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Objective: Patients with chronic ischemia are characterized by a >80% of normal baseline perfusion and loss of reserve capacity resulting in an increased annual stroke risk, i.e. by hemodynamic criteria. In contrast, only little is known about the metabolic state of the chronic ischemic brain. To this end we used navigated transcranial magnetic stimulation and determined the resting motor threshold (RMT) in patients with chronic hemodynamic ischemia as a surrogate marker for metabolic function. RMT is the minimum intensity at a cortical “hot spot” that is necessary to elicit a small motor evoked potential (MEP). It reflects the excitability of central core neurons that arises from the excitability of individual neurons and their local density.
Methods: We examined patients with atherosclerotic stenoocclusive cerebrovascular disease who fulfilled the criteria for EC-IC bypass surgery. Angiographic data and CVR were determined preoperative via Technetium-99m-L, L-ECD SPECT. The RMT "hot-spot" was defined over both hemispheres for MEPs of the first dorsal interosseus (FDI) muscle. We acquired the electrophysiolgical data preoperative as a comparison to the contralateral unharmed hemisphere and three months postoperative as a follow-up.
Results: Our study revealed significantly higher RMTs for the hemispheres which were symptomatic and shown to have an impaired CVR preoperatively compared to the contralateral side (50.7±15.4% compared to 41.6±8.1% p=0.46). In follow-up measurements we compared preoperative and postoperative thresholds showing a reduction of the RMTs (55.4±17.6% → 43.1±9.4% p=0.07), while thresholds of the asymtomatic hemisphere remained nearly unchanged (42.5±6.0% → 41.5±5.7% p=0.7).
Conclusions: For the first time, our study provides evidence for a metabolic suppression and cerebral dysfunction in chronically ischemic, non-infarcted, viable brains. We found reduced excitability in chronic ischemic brain tissue detected via resting motor threshold measurement. This state is reversible as evidenced by post-revascularization normalization. Thus, our results support a novel hibernating brain concept in chronic cerebral ischemia.
