筋収縮性頭痛の研究（第1報）—MEP-Blockの紹介を中心として

MECHANISM AND TREATMENT OF MUSCLE CONTRACTION HEADACHE WITH SPECIAL REFERENCE TO THE BLOCK OF MOST ELECTROSENSITIVE POINT OF CRANIOCERVICAL MUSCLES

はじめに

　筋収縮性頭痛（Muscle contraction headache，以下MCHと略す）はtension headache, muscle tensionheadacheともいわれ，Wolffによればindurative he—adache, myalgic headache，nodular headache, rheuma—tic headache, spastic myalgiaと同義である^16）。日本語名も，筋収細性頭痛の他に，緊張性頭痛・筋攣縮性頭痛・筋緊張性頭痛等々さまざまであり，混乱をまねきやすい。しかし1962年の米国神経学会のAd Hoc commi—tteeの頭痛分類ではtension headacheは廃され，mu—scle contracion headacheが採られたので^1），木稿も筋収縮性頭痛とする。

　このMCHは精神的な緊張が最も大切な原因だが，頸椎捻挫，眼・耳鼻科疾患の頭痛，高血圧の頭痛，偏頭痛その他種々の原因でも誘発ないし併存する非常に普偏的な頭痛である^11）16）。また，頭部外傷後遺症としての頭痛（posttraumatic headache）は脳外科医ときつてもきれない関係にあるが，MCHはこの頭痛の主要病態の一つでもある^11）16）。

Local anesthetic block is available for diagnosis and treatment of the muscle contraction headache. Authors proposed a new method of local anes-thetic block for the treatment of the muscle contraction headache, called "MEP-Block". The procedures consist of detecting the Most Electro-sensitive Point (MEP) of the muscle and infilt-rating the local anesthetic agent there, which produce a prompt relief of headache

The procedures are as follows.

1) The skin over the aching muscle is electric-cally stimulated through the monopolar cathode saline-soaked-swab electrode, the indifferent elect-rode being a lead plate attached to the leg.

2) Electrical stimulus is a square pulse of 0. 5 msec in duration, and about 20 V in intensity, which is delivered repeatedly with the frequency of 2-3 cps.

3) The point of the lowest threshold for themuscle twitching is sought.

4) When the electrosensitive point is deter-mined, the injection needle insulated exept for the tip is introduced into the muscle perpendi-cularly at this point.

5) The same electrical stimuli are applied to the muscle through the needle, which is inserted untill the point showing the lowest threathold for the muscle twitching is encountered. Thus MEP has been hit.

6) A small amount of local anesthetic solution (for example, O. 2-2 ml of 1% Xylocaine) is in-jected at this point which eliminates the twitch responses and pain promptly.

MEPs for the craniocervical muscles are usually located as shown in Fig. 2. In Fig. 3 are the areas depicted to which each component of the craniocervical muscles is responsible in producing pain. Those figures might give some reference in determining where should be injected in an individual cases of the muscle contraction head-ache.

The mechanism of MEP-Block, which has an excellent effect on the muscle contraction head-ache, was discussed from the anatomical and physiological point of view. It is tenable that MEP is just the point where the peripheral nerves enter the muscles. This may be the reason why the MEP-Block promptly eliminates the pain as well as the persistent contraction of involved muscle. In other words, the fundamen-tal mechanism of the MEP-Block is not only the interruption of the pain conduction of pain fibers from the muscle, but also the block of moter fibers which results in a reluxation of the muscle, and breaks down the vicious circle consisted of correation between muscle contraction and noxi-ous pain stimuli.