无脑白质影像学改变的晚发婴儿型异染性脑白质营养不良

目的 分析3例脑白质影像学无改变的晚发婴儿型异染性脑白质营养不良患儿的临床、电生理、影像学和病理学改变特点，总结其特征表现和诊断规律。方法 3例均为男性婴儿，月龄分别为20个月、27个月和28个月。均于出生后15～21个月出现运动发育停滞和倒退，以下肢运动障碍为主，表现有锥体束征。收入院后予以体格检查、电生理检查、头部MRI检查及腓肠神经活检。结果 （1）体格检查：例1双下肢肌力4级，肌张力降低；双膝腱反射亢进，双侧Babinski征阳性。例2四肢肌力5级，肌张力明显增高；腱反射亢进，双侧Babinski征阳性。例3眼球向左、右注视时可发现细小水平眼震，四肢肌力4级，肌张力低；四肢腱反射对称引出，双下肢病理征阴性。（2）辅助检查：3例患儿电生理检查均提示为周围神经病变，MRI检查无异常发现。（3）实验室检查：仅例1行外周血白细胞芳基硫酯酶A检查，显示活性显著下降。（4）腓肠神经活检：3例患儿均显示髓神经纤维显著减少，残存的有髓神经纤维的髓鞘变薄，甲苯胺蓝染色见部分雪旺细胞及吞噬细胞内出现紫红色异染颗粒，超微结构呈指纹样、髓样和平行排列的棒状结构。结论 病理检查证实细胞内沉积物具有异染性，而周围神经病变具有髓鞘发育不良特点。由于脑白质MRI无改变，这组以周围神经损害为主的息儿可能是异染性脑白质营养不良的一种特殊类型，诊断为伴有中枢神经系统损害的异染性周围神经病更符合临床表现规律。

Late-onset infantile metachromatic leukodystrophy without MRI abnormalities in white matter

Objective The clinical manifestation, electrophysiological, imaging and pathological characteristics and diagnosis of 3 patients with late-onset infantile metachromatic leukodystrophy without marked cranial MRI changes were analyzed and reviewed. Methods The first case of the 3 boy patients, 20 months old, developed progressive walking difficulty at the age of 15 months. Physical examinations showed paresis in lower limbs with hypotonia and positive pyramidal signs. Electrophysiological study showed a reduction of the nerve conduction velocity while abnormalities were not found in cranial MRI. The second boy, 27 months old, also developed weakness in 15 months old early in lower limbs and later in upper limbs. He also showed positive pyramidal signs with hypertonia. Neurogenic impairment was found in electromyography. Cranial and spinal MRI revealed no abnormalities. The third boy, 28 months old, was found motor development retardation at the age of 21 months. His disorder was so severe that he could not walk without help. Neurological examinations showed weakness in extremities and hypotonia. Sural nerve biopsies were performed in all the three patients and arylsulfatase A activity was measured in the first boy and his parents. Results Sural nerve biopsies showed definite demyelinating neuropathy. The purple-red, metachromatic granules were found in schwann cells and phagocytes, which appeared as finger-like, myelinated or paralleled patterns under ultramicroscopy. Conclusion The pathological examination of sural nerve demonstrates the intracellular deposites are metachromatic and the peripheral nerves are characterized with underdevelopment of myelin sheath. These patients without MRI abnomality in white matter but involving of peripheral nerve lesions as main clinical symptom may be a peculiar type of metachromatic leukodystrophy. Thus the diagnosis of metachromatic peripheral neuropathy associated with central nervous system impairment is more appropriate for the clinical manifestations.