1999 Fiscal Year Final Research Report Summary
To confirm the usefulness of N18 and other SEP components of medullary origin for the diagnosis of brain death
| Project/Area Number |
09670669
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Neurology
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| Research Institution | Teikyo University |
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Principal Investigator |
SONOO Masahiro School of Medicine, Teikyo University, Assistant Professor, 医学部, 講師 (40231386)
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| Co-Investigator(Kenkyū-buntansha) |
MOCHIZUKI Atsuko School of Medicine, Teikyo University, Lecturer, 医学部, 助手 (50286994)
FUKUDA Hiroyuki School of Medicine, Teikyo University, Lecturer, 医学部, 助手 (60286961)
SHOZAWA Yasunobu School of Medicine, Teikyo University, Lecturer, 医学部, 助手 (30256052)
HATANAKA Yuuki School of Medicine, Teikyo University, Lecturer, 医学部, 助手
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| Project Period (FY) |
1997 – 1999
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| Keywords | somatosensory evoked potentials (SEPs) / median nerve / brain death / criteria to diagnose brain death / N18 / auditory brainstem responses (ABRs) / brainstem function / cuneate nucleus in medulla oblongata |
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| Research Abstract |
1. We collected around 140 recordings of SEP and ABR together with clinical signs from around 100 brain-dead or comatous patients during the 3 years we accepted the grants. As a result, N18 in median SEPs was lost in all the brain-dead recordings whereas it was preserved in nearly 90% of comatous but not brain-dead recordings. Namely, N18 had perfect specificity and very high sensitivity (higher than ABR which was preserved for about 80% of comatous recordings) for detecting the remaining brainstem function.
2. We managed to follow the course progressing from coma to brain-death in 8 patients having brain herniation. Signs reflecting midbrain function such as light reflex and oculocephalic reflex were first lost, those reflecting pontine function such as corneal reflex and wave III in ABR followed. Lastly, loss of cough reflex and pharyngeal reflex, cease of spontaneous respiration, sudden fall of blood pressure and loss of N18 occurred within a short time and brain-death was judged to be established. The fact that N18 disappeared concomitantly with these signs reflecting medullary functions further supported our opinion that N18 is generated by the cuneate nucleus located in the medulla oblongata.
3. There has been no neurophysiological or other method which can objectively evaluate the function of medulla oblongata which plays the most important role for maintaining the vital functions. ABR can evaluate only pontine and midbrain functions. The present investigation established N18 as the first objective indicator for the medullary function. Wide clinical application of N18 must increase the reliablity of the diagnose is of brain death.
4. Other related researches performed include: the origin of the P13-like potential which remains after brain death (by Sonoo), the origin of P9 (by Mochizuki and Sonoo) and the best method to determine the stimulus intensity in median SEPs (by Fukuda and Sonoo).
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