Boxerの聴性脳幹反応について

AUDITORY BRAIN STEM RESPONCES OF KNOCKED-OUT BOXERS

　抄録　脳振盪における脳幹機能変化の有無を調べるため，最も日常的に脳振盪を発生し得るスポーツ，ボクシングの選手を対象とし，試合後，練習後，knock-out （KO）後などに，聴性脳幹反応（ABR）潜時を測定した。試合後，KO後においても，また，脳振盪の意識障害期間中にも，ABR潜時の延長は認められず，既報のpostconcussion syndromeにおける潜時延長や，実験的脳振盪での結果とは異なるものであった。脳振盪の責任病巣を考える上で，今回の結果は，脳幹ではなく，より上位の中枢の関与を示すものであると考えられる。また，試合，練習に限らず，全てのボクサーに運動負荷後のABR潜時短縮が見られたが，これは運動による体温上昇が影響している可能性がある。

We studied about ABRs of boxers, who receive repeated impact to the head and are often con-cussed, immediately after bouts or training in order to reveal the influence of knock-out or re-peated mild head injuries.

Forty-six male professional boxers ranged from18 to 28 years old, were examined at the stadium and the boxing gymnasium. 85 recordings were done since some boxers were examined more than once. 27 cases of pre-exertion group (resting : 5, pre-sparring : 10, pre-training : 12) were compared with post-bout group (35 cases).

The I -V IPL (interpeak latency) of pre-exertion group was 4.30 ±0.18 m sec and that of post-bout group was 4.02 ±0.15 m sec. The latter showed signifiantly shorter (p<0.01) IPL.

Among 35 cases of post-bout group, the I-V IPL of knocked-out group (14 cases) was 4.04±0.11 m sec, and that of non-knocked-out group (21 cases) was 4.01±0.17 m sec. There was no signi-ficant difference.

The I -V IPL of pre-sparring state was 4.24 ±0.15 m sec, and that of post-sparring state was 4.10±0.13 m sec. The difference was significant between these two groups (p<0.01).

After training without impacts to the head, I -V IPLs were shortened in all 12 cases.

IPL of pre-training state was 4.34±0.2 m sec, and that of post training state was 4.19±0.22 m sec.

This also showed significant difference (p<0.01).

On one boxer, we recorded ABRs during dis-turbance of consciousness. He was knocked-out by a blow to the face in the first round, and was completely unconscious.

ABRs were recorded twice immediately after he had been laid on the bed. I -V IPL was 4.12 m sec on both recordings. Ten minutes later, he recovered and showed no neurological deficit ex-cept for amnesia. Subsequent ABRs recorded 30 minutes after the initial recordings showed almost the same wave pattern, and I -V IPL was exactly the same.

Knocked-out boxers, even in unconscious state, did not show any delay of ABR IPL, comparing with non-knocked-out boxers. Therefore it was considered that a man can be concussed to get unconscious without alteration of ABRs. This finding indicated that the responsible lesion for cerebral concussion is cerebrum or the higher level than brain stem, not the brain stem itself.

The reason for shortened ABR IPL after exer-tion was unknown. However the alteration of body temperature was considered to have a effect to central conduction velocity as well as to peri-pheral conduction velocity.

This phenomenon is under investigation.