血流豊富な甲状腺腫瘍に関連した鎖骨下動脈盗血現象

Subclavian Steal Phenomenon Associated with Hypervascular Thyroid Tumor

Ⅰ．はじめに

　鎖骨下動脈盗血症候群（subclavian steal syndrome：SSS）は一側椎骨動脈の発育不全や鎖骨下あるいは腕頭動脈の高度狭窄・閉塞により脳循環障害を来す疾患である³⁾．典型的には，椎骨脳底動脈系の虚血に伴うめまいや失神，患側上肢の痺れなどの症状が一般的であるが，無症候性である場合も多く，椎骨動脈の逆流現象のみで症候を認めないものを鎖骨下動脈盗血現象（subclavian steal phenomenon：SSP）と呼び区別される．

　SSSおよびSSPの原因としては，動脈硬化症がそのほとんどを占めている^3,5,8,9)．しかし今回われわれは，中大脳動脈狭窄症に伴う急性期脳梗塞症例において，脳血管造影検査にて高濃染像を呈する甲状腺腫瘍に関連したSSPを経験したので，文献的考察を加え報告する．

　Subclavian steal syndrome (SSS) is caused by hypoplasia of a vertebral artery or stenosis or occlusion of the subclavian artery or the brachiocephalic artery with subsequent retrograde filling of the subclavian artery via the contralateral vertebral artery. Symptoms of SSS are due to vertbrobasilar insufficiency or ischemia of the ipsilateral upper extremity,and they may include dizziness,syncope,ataxia,arm claudication,hand numbness or a decrease in brachial blood pressure on the affected side. However,most SSS cases are asymptomatic and they are classified as subclavian steal phenomenon (SSP). Atherosclerosis is the common cause of SSS,and Takayasu arteritis,neurofibromatosis,trauma,embolization,congenital vascular anomalies and surgical interruption of the subclavian artery can be identified among the other causes. We describe a rare case of hypervascular thyroid nodule presenting with features of SSP. The patient was hospitalized with acute cerebral infarction due to middle cerebral artery (MCA) severe stenosis. The patient had conservative therapy in the acute stage,and underwent STA-MCA anastomosis for MCA stenosis in the chronic stage. SSS was asymptomatic although there was laterality in blood pressure in the patient's bilateral upper limbs. Thyroid tumor was regarded as benign by radiological findings,laboratory data,and physical examination. If SSS becomes symptomatic,removal of the thyroid tumor may be indicated.