The mysterious science of pain - Joshua W. Pate

譯者: Lilian Chiu 審譯者: Helen Chang

In 1995, the British Medical Journal

1995 年，英國醫學期刊刊出了

published an astonishing report about a 29-year-old builder.

一篇關於一名二十九歲 建築工人的驚人報告。

He accidentally jumped onto a 15-centimeter nail,

他意外跳到了一根 十五公分的釘子上，

which pierced straight through his steel-toed boot.

釘子直接穿過了他的鋼頭靴。

He was in such agonizing pain that even the smallest movement was unbearable.

他非常痛苦，連最小的 動作都無法忍受。

But when the doctors took off his boot, they faced a surprising sight:

但當醫生取下他的靴子時， 他們看到的景象讓他們驚呆了：

the nail had never touched his foot at all.

釘子根本沒有碰到他的腳。

For hundreds of years,

數百年來，

scientists thought that pain was a direct response to damage.

科學家認為疼痛是 對於損傷的直接反應。

By that logic, the more severe an injury is, the more pain it should cause.

根據這樣的邏輯，越嚴重的傷 會造成越大的疼痛。

But as we’ve learned more about the science of pain,

但，隨著我們對疼痛的 科學有更多的了解，

we’ve discovered that pain and tissue damage don’t always go hand in hand,

我們發現，疼痛和組織損傷 不見得是一致相符的，

even when the body’s threat signaling mechanisms are fully functioning.

即使身體的威脅信號機制 完全正常運作亦然。

We’re capable of experiencing severe pain out of proportion to an actual injury,

我們能夠經歷到和實際傷口 不成比例的劇烈疼痛，

and even pain without any injury,

甚至可能在沒受傷時感到疼痛，

like the builder, or the well-documented cases of male partners

就像那位建築工人， 或是有許多文件記載的案例，

懷孕女性在懷孕過程或分娩時，

of pregnant women experiencing pain during the pregnancy or labor.

男性伴侶也會經歷到疼痛。

What’s going on here?

這是怎麼回事？

There are actually two phenomena at play:

其實，這背後有兩種現象：

the experience of pain, and a biological process called nociception.

對疼痛的體驗以及一種 生物過程，叫做痛覺。

Nociception is part of the nervous system’s protective response

神經系統會對於有害或可能 有害的刺激產生保護性反應，

to harmful or potentially harmful stimuli.

而痛覺是反應的一部分。

Sensors in specialized nerve endings

專門的神經末端的感測器

detect mechanical, thermal, and chemical threats.

會偵測機械的、溫度的， 及化學的威脅。

If enough sensors are activated,

如果有足量的感測器被觸發，

electrical signals shoot up the nerve to the spine and on to the brain.

電訊號就會透過神經 傳到脊椎，再傳到大腦。

The brain weighs the importance of these signals

大腦會判斷這些訊號的重要性，

and produces pain if it decides the body needs protection.

如果它覺得身體需要保護， 便會產生疼痛。

Typically, pain helps the body avoid further injury or damage.

疼痛通常協助身體 避免進一步受傷或受損。

But there are a whole set of factors besides nociception

但除了痛楚之外，有一整組因子

that can influence the experience of pain— and make pain less useful.

都有可能影響到疼痛的體驗—— 讓疼痛變得不那麼有用。

First, there are biological factors that amplify nociceptive signals to the brain.

首先，有生物因子， 會放大發送到大腦的痛覺訊號。

If nerve fibers are activated repeatedly,

如果神經纖維不斷重覆被觸發，

the brain may decide they need to be more sensitive

大腦可能會判斷它們得要更敏感些，

to adequately protect the body from threats.

才能夠妥當地保護身體不受威脅。

More stress sensors can be added to nerve fibers

會有更多壓力感測器 被加到神經纖維上，

until they become so sensitive that even light touches to the skin

直到神經纖維變得非常敏感， 即使輕輕一碰到皮膚

spark intense electrical signals.

也會發出強烈的電訊號。

In other cases,

在其他的情況中，神經會適應，

nerves adapt to send signals more efficiently, amplifying the message.

以更有效地發送訊號， 將訊息放大。

These forms of amplification

這些放大的形式

are most common in people experiencing chronic pain,

最常在長期疼痛的人身上看到，

which is defined as pain lasting more than 3 months.

長期疼痛指的是持續 超過三個月的疼痛。

When the nervous system is nudged into an ongoing state of high alert,

當神經系統進入了 持續高度警戒的狀態，

pain can outlast physical injury.

疼痛可能會持續得比傷口還久。

This creates a vicious cycle in which the longer pain persists,

這會造成惡性循環， 痛苦持續越久，

the more difficult it becomes to reverse.

它就越難反轉。

Psychological factors clearly play a role in pain too,

很明顯，心理因子也和疼痛有關，

potentially by influencing nociception and by influencing the brain directly.

它有可能會影響痛覺 以及直接影響大腦。

A person’s emotional state, memories,

人的情緒狀態、記憶、

beliefs about pain and expectations about treatment

有多相信疼痛，以及對治療的預期

can all influence how much pain they experience.

都有可能會影響他們 體驗到的疼痛程度。

In one study,

在一項研究中，認為自己 無法控制痛苦的孩子

children who reported believing they had no control over pain

actually experienced more intense pain

會經歷到更強烈的疼痛，

than those who believed they had some control.

而相信能控制疼痛的人 就沒這麼嚴重。

Features of the environment matter too:

環境的特徵也很重要：

In one experiment,

在一項實驗中，

volunteers with a cold rod placed on the back of their hand

將一根冰冷的桿子 放在自願者的手背上，

reported feeling more pain when they were shown a red light than a blue one,

當他們看到紅燈時，所回報的 疼痛度就高於看到藍燈時，

even though the rod was the same temperature each time.

但桿子的溫度一直都沒有變過。

Finally, social factors like the availability of family support

最後是社會因子， 比如是否能取得家人支持

can affect perception of pain.

就可能影響對痛苦的感知。

All of this means that a multi-pronged approach to pain treatment

上述這些意味著， 在治療疼痛時若能多管齊下，

that includes pain specialists, physical therapists, clinical psychologists, nurses

配合疼痛專家、物理治療師、 臨床心理學家、護士，

and other healthcare professionals is often most effective.

及其他健康照護專業人士， 會有最好的效果。

We’re only beginning to uncover the mechanisms behind the experience of pain,

我們才剛開始發掘 感受疼痛背後的機制，

but there are some promising areas of research.

但有一些研究領域的前景看好。

Until recently,

到最近之前，

we thought the glial cells surrounding neurons were just support structures,

我們都認為神經周圍的膠質細胞 只是支撐用的結構，

but now we know they have a huge role in influencing nociception.

但現在我們知道它們在影響痛覺 方面，扮演重要的角色。

Studies have shown that disabling certain brain circuits in the amygdala

研究顯示，關閉 杏仁核中的某些腦迴路

can eliminate pain in rats.

就可以消除老鼠的疼痛。

And genetic testing in people with rare disorders

針對無法感受疼痛的特殊疾病病人

that prevent them from feeling pain

所做的基因檢測

have pinpointed several other possible targets for drugs

找出了數個可能的用藥方向，

and perhaps eventually gene therapy.

也許最終還能用上基因治療。