基于MRI的眼运动神经和眼外肌影像学改变:KIF21A基因突变的先天性眼外肌纤维化

MRI demonstrates abnormalities of motor nerves and extraocular muscles in congenital fibrosis syndrome due to mutations in KIF21A

摘要:

目的：利用高分辨MRI观察KIF21A基因突变的先天性眼外肌纤维化Ⅰ型的眼运动神经和眼外肌的影像特征。

方法：对11例KIF21A基因R954W突变的先天性眼外肌纤维化综合征Ⅰ型患者行MRI扫描。眼外肌和眼运动神经的眶内段采用二元-相位线圈，2-mm层厚T1加权像扫描； 眼运动神经的脑池段采用头线圈，0.6-mm层厚3D-FIESTA序列扫描。

结果：先天性眼外肌纤维化Ⅰ型患者的动眼神经、外展神经及滑车神经的眶内段和脑池段都表现出不同程度的发育不良，其中8例的眶内段见可疑由动眼神经向外直肌发出的异常神经支配。全部患者双侧六条眼外肌不同程度的萎缩，以上直肌和提上睑肌最为严重。

结论：高分辨MRI显示KIF21A基因突变的先天性眼外肌纤维化Ⅰ型患者眼运动神经和眼外肌及‘Pulley'结构发育不良，提示先天性眼外肌纤维化的原发病变是运动神经发育缺陷。

Abstract:

AIM:To observe the structural basis of ocular motility abnormalities in patients with congenital fibrosis of the extraocular muscles type Ⅰ(CFEOM Ⅰ)due to missense mutations in the developmental kinesin KIF21A using high-resolution magnetic resonance imaging(MRI).

METHODS: Totally 11 affected individuals reported KIF21A mutations were correlated with MRI studies demonstrating extraocular muscles(EOMs)size, location, contractility, and innervation. EOMs and the motor nerve in the orbits were imaged with T1 weighted in a triplanar scan using a dual-phased coils with 2.0mm thick. Motor nerves were imaged at the brainstem using head coils and 3D-FIESTA with 0.6-mm thick.

RESULTS: Patients with CFEOM Ⅰ exhibited different degrees of hypoplasia of oculomotor nerve, the abducens nerve and the trochlear nerve were also affected, of which 8 cases of orbital section could see the signal of abnormal nerve dominated by oculomotor nerve to lateral rectus. The both sides of six EOMS in all patients exhibited variable atrophy and abnormal bright internal signal on T1 imaging, particularly severe for the superior rectus and levator muscles.

CONCLUSION: High-resolution MRI can directly demonstrate pathology of motor nerves,affected EOMs, and ‘Pulley' hypoplasia caused by CFEOM Ⅰ due to mutations in KIF21A,and these findings suggest that the neuronal hypoplasia is the etiological factor of CFEOM.