什麼是發作性運動誘發性運動障礙

發作性運動誘發性運動障礙(Paroxysmal Kinesigenit Dyskinesia，PKD)又稱發作性運動誘發性舞蹈手足徐動症，由Kertesz(1967)首先報導並命名，是發作性運動障礙中最多見的一種類型，以靜止狀態下突然隨意運動誘發短暫、多變的運動異常為特徵。

PKD可為遺傳性或散發性，有遺傳家族史的病例約占60%，遺傳方式大多為常染色體顯性遺傳，有外顯不全現象。

致病基因定位於16p11.2-q12.1、16p11.2-q11.2和16q13-q22.1，這種基因定位的不重疊，提示PKD可能存在遺傳異質性。

PKD雖已有初步的基因定位，但迄今為止PKD的致病基因尚未知。

具發病機制不明，Menkes(1995)認為PKD是介於運動障礙與癲痢之間的一類疾病，目前傾向於是—種離子通道病，認為本病與癲癇可能有共同的生物學基礎和離子通道缺陷，其病理生理機制之一很可能與Na+通道缺陷有關。

PKD起病於兒童和青少年期，發病年齡從4個月至57歲，多在6～16歲，以男性多見，男女之比為(2～4):1。

發作前少數患者可有感覺先兆，如受累部位肢體發麻、發涼、發緊等。

發作常由突然的動作觸發，如起立、轉身、邁步、舉手等，也可由驚嚇、恐懼、精神緊張、過度換氣等誘發。

發作時患者表現為肢體和軀幹的肌張力不全、舞蹈、手足徐動、投擲樣動作等多種錐體外系症狀。

症狀可累及單肢、偏身，也可為雙側交替或同時出現，當面部和下頒肌肉受累時，可出現構音障礙。

發作時間短暫，一般持續數秒，80%以上的病例發作持續時間短於1min，很少超過5min。

發作時無意識障礙，停止動作或減慢動作常可終止發作。

發作次數不定，1年數次，1個月數次或1日數次，呈病初發作次數少，至青春期發作次數增多，再隨年齡增長而發作逐漸減少或停止。

發作可以使患者喪失活動能力，干擾其行走、學習、工作和日常活動。

發作間期神經系統檢查正常，發作時腦電圖檢查80%未見癇樣放電。

SPECT檢查在發作時可見基底節區血流灌注增強，說明本病在陣發性發作時有基底節區功能增強現象。

Bmno等在綜合分析121例PKD後，提出PKD新的診斷標準為：特定的觸發因素(如突然的運動)，短暫的發作持續時間(<1min)，發作時無意識障礙和疼痛，抗癲癇藥物治療有效，排除其他器質性疾病，起病年齡為1～20歲(有家族史的病例不受此限)。

本病雖非癲癇，但絕大部分患者服用卡馬西平、苯巴比妥、苯妥英鈉、丙戊酸、托吡酯、拉莫三嗪等抗癲癇藥物均能控制發作，緣於阻滯鈉離子通道作用。

Familial paroxysmal kinesigenic dyskinesia 家族性運動誘發運動障礙

疾病特徵

Familial paroxysmal kinesigenic dyskinesia (referred to as familial PKD in this entry) is characterized by unilateral or bilateral involuntary movements precipitated by other sudden movements such as standing up from a sitting position, being startled, or changes in velocity; attacks include combinations of dystonia, choreoathetosis, and ballism, are sometimes preceded by an aura, and do not involve loss of consciousness. Attacks can be as frequent as 100 per day to as few as one per month. Attcks are usually a few seconds to five minutes in duration but can last several hours. Familial PKD has been associated with infantile- but not adult-onset seizures. Severity and combinations of symptoms occur. Age of onset is typically in childhood and adolescence, but ranges from four months to 57 years. Familial PKD is predominantly seen in males.

診斷與測試

The diagnosis of familial PKD is based on the clinical findings of attacks of dystonia, chorea, ballismus, or athetosis triggered by sudden movements that occur many times per day and can be prevented or reduced in frequency by phenytoin or carbamezepine. The gene/s associated with PKD have not been identified. Linkage of familial PKD to chromosome 16q has been established in several families. Linkage testing is available on a research basis only.

治療與處理

Attack frequency is reduced or prevented by the anticonvulsants phenytoin or carbamezepine, typically given at lower doses than are used to treat epilepsy. Other effective anticonvulsants include oxcarbazepine, ethosuximide, and lamotrigine.

遺傳諮詢

Familial PKD is inherited in an autosomal dominant manner. More than 90% of individuals with familial PKD have an affected parent.

The proportion of cases caused by de novo mutations is unknown. Offspring of affected individuals with familial PKD have a 50% chance of inheriting the gene mutation. Because familial PKD demonstrates incomplete penetrance, a clinically unaffected parent may still have a gene mutation, placing the sibs of the proband at a 50% risk of inheriting the mutation. Prenatal testing is not available.

最新研究進展

2011年，Nature Genetics上發表文章，發現大多數家族性PKD均由PRRT2基因的突變引起，該基因編碼一種跨膜蛋白，突變後的蛋白無法定位於細胞膜。

之後，陸續有人在家族性良性嬰兒驚厥BFIC以及發作性手足舞蹈徐動症ICCA中，發現PRRT2基因的突變，提示PKD與BFIC以及ICCA可能為同一致病基因所導致的一類疾病。

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