環椎低形成に特発性環軸椎亜脱臼を伴った頚髄症の2例

Cervical Myelopathy Caused by Atlas Hypoplasia with Idiopathic Atlanto-Axial Subluxation : Report of Two Cases

　抄録：環椎低形成に特発性環軸椎亜脱臼を伴い頚髄症を来した2例を経験した．症例1は，50歳の女性で，両手足のしびれ感，歩行障害を主訴に来院．神経学的には，腱反射は四肢で亢進し手指巧緻運動障害とけい性歩行を呈していた．JOAスコアは13点であった．症例2は，75歳の男性で，両下肢の脱力を主訴に来院．手指の巧緻運動障害を認め，歩行は不能で排尿困難がみられ，JOAスコアは6点であった．2例とも単純X線側面像およびCT像で環椎後弓は脊柱管内にくい込み，環椎椎孔前後径が狭く，低形成と診断された．MRIで著しい狭窄を認め，T2強調で髄内高輝度変化がみられた．特発性環軸椎亜脱臼を伴う頚髄症のため，C1椎弓切除にC0-2-3後方固定を要した．

　We experienced two cases of cervical myelopathy caused by atlas hypoplasia with idiopathic atlanto-axial subluxation. Case 1 was a female, 50 years of old. She presented herself in our clinic with chief complaints included numbness in limbs and dysbasia. Neurologically, exalted tendon reflex in limbs, subtlety dyskinesia of hand and spastic walking were observed. JOA score was 13 points. Case 2 was a male, 75 years of old. He presented himself in our clinic with a chief complaint of weakness of lower limbs. Subtlety dyskinesia of hand, abasia and dysuria were observed and JOA score was 6 points. Lateral views of plain x-ray film and CT-myelograms of these two cases showed that posterior arch on atlas encroached upon vertebral canal and occipitofrontal diameter of atratic vent was narrow, so we gave them diagnosis of hypoplasia. MRI showed significant stenosis, and T2-weighted image showed gross focal constriction of in pulpa. Posterior fixation of C0-2-3 was needed for C1 laminectomy because of cervical myelopathy with idiopathic atlanto-axial subluxation.