伤寒摇头。何以明之。头者诸阳之会也。诸阳之脉。皆上于头。诸阴脉皆至颈胸中
而还。阳脉不治。则头为之摇。伤寒摇头有三。皆所主不同也。有曰摇头言者。里痛
也。以里有痛者。语言则剧。欲言则头为之战摇也。有曰独摇头。卒口噤。背反张者。
痉病也。以风盛于上。风主动摇故也。里痛非邪也。痛使之然。痉病非逆也。风使之
然。至于阳反独留。形体如烟熏。直视摇头者。又谓之心绝。盖心藏神。而为阴之本。
阳根于阴。阴根于阳。阴阳相根。则荣卫上下相随矣。绝则神去而阴竭。阳无根者。
则不能自主持。故头为之摇矣。王 曰。滋苗者以固其根。伐下者必枯其上。内绝
其根。外作摇头。又何疑焉。心绝者真病也。风痉里痛者。邪气也。观其头摇。又当明
其臧否焉。
伤寒螈 。何以明之。螈者筋脉急也。 者筋脉缓也。急者则引而缩。缓者则纵而
伸。或缩或伸。动而不止者。名曰螈 。俗谓之搐者是也。黄帝内经曰。病筋脉相引
而急。名曰螈 。螈谓若契合之契也。行则缓。卧则紧。从则纵。 疾之纵者。谓若放
纵之纵也。以急为螈。以缓为 。理至明矣。螈 者。风疾也。而癫痫则螈 焉。伤寒
螈者。邪热气极也。热盛则风搏并经络。风主动。故四肢螈 而不宁也。故风温
被火者。曰发微黄色。剧者如惊痫。时螈 。言其热气之剧盛也。伤寒病至于发螈
者。疾势已过矣。多难可制。内经曰。太阳终者。戴眼反折。螈 绝汗乃出。大如贯
珠。着身不流。是见其螈 。为已过之疾也。又有四肢 习。为四肢动而不止。似螈
而无力。不得伸缩者也。此为肝绝。螈 之证虽难已。若能以祛风涤热之剂。折
其大热。则螈 亦有生者。若妄加灼火。或饮以发表之药。则死不旋踵。经曰。一逆尚引日。再逆促命期。
伤寒病出现摇头的症状，该如何阐明其机理呢？头部是诸阳经汇聚的地方。所有阳经的脉气，都上行至头部；而所有阴经的脉气，只到达颈胸部位就返回了。如果阳经之气失调，就会导致头部摇动。伤寒病中的摇头有三种情况，各自所主的病机不同。
有一种是边说话边摇头，这是体内有疼痛所致。因为体内有痛处，说话时疼痛加剧，想要说话时头就会颤抖摇动。
有一种是独自摇头，突然牙关紧闭、背部反张，这是痉病。这是因为风邪盛于上部，风性主动，所以导致摇动。体内的疼痛并非邪气本身，而是疼痛使其如此；痉病并非逆证，而是风邪使其如此。
至于阳气独留于上，形体像被烟熏一样黑晦，两眼直视且摇头的，这被称为心绝。因为心藏神，是阴的根本。阳根源于阴，阴根源于阳，阴阳相互依存，营卫之气才能上下相随。一旦心绝，则神志离去而阴液枯竭，阳气失去根本，就不能自主控制，所以头部会摇动。王叔和说：“滋养树木要巩固其根部，砍伐树根必然导致树梢枯死。”内部断绝了根本，外部就会出现摇头，这有什么可怀疑的呢？心绝是真病，风邪引起的痉病和里痛属于邪气致病。观察头部摇动的症状，应当进一步辨明其吉凶预后。
伤寒病出现抽搐（瘛疭），该如何阐明其机理呢？“瘛”是指筋脉拘急，“疭”是指筋脉弛缓。拘急则会牵引收缩，弛缓则会舒展伸长。时而收缩时而伸展，动作不止的，称为瘛疭。俗称“搐”。《黄帝内经》说：“病见筋脉相互牵引而拘急，称为瘛疭。”“瘛”字意为契合之契，行走时筋脉舒缓，躺卧时筋脉紧张；顺应病情则为舒展。“疭”字意为放纵之纵，指急速舒展的状态。以拘急为瘛，以弛缓为疭，道理非常明白。瘛疭属于风疾范畴，癫痫也会伴有瘛疭。伤寒病出现的瘛疭，是邪热极盛所致。热盛则与风邪搏结于经络，风性主动，所以四肢抽搐而不安宁。因此，患风温病又误用火疗的，会出现微黄色，严重的如同惊痫，时常发生瘛疭，这是形容热气极度亢盛。伤寒病发展到出现瘛疭的程度，疾病势态已经过了极期，大多难以控制。《内经》说：“太阳经气终绝时，表现为两目上视、角弓反张、瘛疭，绝汗流出，汗珠大如贯珠，附着在身上不流动。”见到这种瘛疭，说明是病情已至极期的重病。又有四肢微微颤动（瞤动），称为四肢跳动不止，类似瘛疭但无力，不能伸缩，这属于肝绝证。瘛疭的证候虽然难治，如果能用祛风清热的方法，折减其大热，那么瘛疭也有治愈的可能。如果妄加火灸，或饮用发表的药物，则死亡就在眨眼之间。经文说：“一次误治尚能拖延时日，再次误治则加速死亡。”
Shake of the Head in Cold Damage. How to elucidate this? The head is the convergence point of all Yang meridians. The Qi of all Yang meridians ascends to the head, whereas the Qi of all Yin meridians reaches only the neck and chest before returning. If the Qi of the Yang meridians fails to regulate properly, it results in shaking of the head. There are three types of head shaking in Cold Damage, each indicating a different pathogenesis.
One type involves shaking the head while speaking, which indicates internal pain. Due to pain within, speaking exacerbates the discomfort, causing the head to tremble and shake when attempting to speak.
Another type presents as isolated head shaking, sudden lockjaw (trismus), and opisthotonos (backward arching of the back). This is Jing disease (Spasm Disease). It occurs because Wind pathogen is abundant in the upper body; since Wind has the nature of movement, it causes shaking. Internal pain is not caused by the pathogen itself but by the pain inducing the symptom; Jing disease is not a reversal syndrome but induced by Wind.
Regarding the case where Yang Qi remains exclusively above, the complexion appears dark like smoke, the eyes stare fixedly, and the head shakes: this is termed Heart Jue (Heart Exhaustion). The Heart houses the Shen (Spirit) and serves as the root of Yin. Yang roots in Yin, and Yin roots in Yang. When Yin and Yang mutually support each other, Ying (Nutritive) and Wei (Defensive) Qi follow each other up and down. Upon exhaustion, the Shen departs and Yin fluids are depleted. Without a root, Yang cannot maintain self-control, hence the head shakes. Wang Shuhe stated: "To nourish the shoots, one must consolidate the roots; to cut the roots, the tops will inevitably wither." Internally severing the root manifests externally as head shaking; what doubt could there be? Heart Jue is a true organ failure, whereas Jing disease from Wind and internal pain are manifestations of pathogenic factors. Observing head shaking requires further differentiation of auspicious or inauspicious prognosis.
Chorea-like Movements (Chi Zong) in Cold Damage. How to elucidate this? "Chi" refers to tendon and vessel contraction/tightness; "Zong" refers to relaxation/looseness. Tightness leads to pulling and shrinking; looseness leads to extending and stretching. Alternating between shrinking and extending, with continuous motion, is named Chi Zong. Commonly known as "Chu" (twitching). The *Huangdi Neijing* states: "When diseases involve tendons and vessels pulling and contracting tightly, it is named Chi Zong." "Chi" implies fitting together like a tenon and mortise; walking makes them loose, lying down makes them tight; following the condition allows extension. "Zong" implies letting go freely; rapid extension is described as such. Taking tightness as Chi and looseness as Zong, the principle is clear. Chi Zong belongs to Wind diseases, and epilepsy also involves Chi Zong. Chi Zong in Cold Damage is due to extreme excess of Evil Heat. Excessive Heat combines with Wind in the meridians; since Wind is active, the four limbs undergo Chi Zong restlessly. Therefore, those suffering from Feng Wen (Wind-Warmth) treated incorrectly with fire therapy may develop a slight yellow hue; severe cases resemble convulsive epilepsy with intermittent Chi Zong, describing the extreme abundance of Heat. When Cold Damage progresses to Chi Zong, the disease momentum has passed its peak and is often difficult to control. The *Neijing* states: "When Taiyang Qi terminates, symptoms include upward staring eyes, opisthotonos, Chi Zong, and the emergence of Jue Han (Exhaustion Sweat), large like beads on a string, adhering to the body without flowing." Witnessing such Chi Zong indicates a disease that has reached an advanced/exhausted stage. There is also a condition called Si Xi (trembling/flapping of limbs), where limbs move continuously, resembling Chi Zong but lacking strength and unable to extend or contract; this is Liver Jue (Liver Exhaustion). Although Chi Zong is difficult to cure, if agents that dispel Wind and purge Heat are used to reduce the intense Heat, recovery is possible. If cauterization is wrongly applied, or diaphoretic medicines are drunk, death will follow instantly. The Canon states: "One error may prolong life for a day; two errors hasten the time of death."