鉴别诊断
结节性硬化症(TS)
结节性硬化症是种神经皮肤综合征,由9q34.3(编码错构瘤蛋白)和16p13.3(编码 tuberin蛋白)染色体中基因突变所致。其中2/3为散发患者,其余为常染色体显性遗传,外显率可不同。其典型的三联征包括面部血管纤维瘤、智力低下和癫痫发作,但仅在约1/3的患者中出现。在中枢神经系统,TS可表现为皮质或皮质下结节、沿神经元迁移方向呈放射状分布的白质病损、室管膜下结节和室管膜下巨细胞星形细胞瘤( SEGAs)。皮质或皮质下结节是由杂乱的神经胶质和异位的神经元组成,表现为皮质和皮质下三角形异常信号,可见钙化,有时呈现强化。室管膜下结节在T1和T2图像上信号多变,但通常可见强化。当有钙化时,结节在MRI表现为低信号,而大多数钙化发生在20岁之前。SEGAS为低级别肿瘤,在TS中的发生率为10%~15%,好发于孟氏孔,持续性生长,并可见强化。有无间隔生长是鉴别 SEGAS与室管膜下结节最好的标志。治疗通常倾向于脑脊液分流。与TS相关的常见病变很多,包括视网膜错构瘤、心脏横纹肌瘤、肾囊肿和血管平滑肌脂肪瘤、肺淋巴管平滑肌瘤病、甲下纤维瘤和皮肤病损,如灰叶斑和鲨皮斑。
Tuberous sclerosis is a neurocutaneous syndrome caused by mutations within the tuberin chromosome 9q34.3(coding for hamartoma protein) and 16p13.3(coding for tuberin protein). Among them, 2/3 are sporadic patients, while the rest are autosomal dominant with different penetrance. The typical triad includes facial angiofibroma, mental retardation and seizures, but only appears in about a third of patients. In the central nervous system,TS may present as cortical or subcortical nodules, white matter lesions radially distributed along neuronal migration, subependymal nodules, and subependymal giant cell astrocytoma (SEGAs). Cortical or subcortical nodules are composed of a jumble of glial and heterotopic neurons that appear as abnormal triangular signals in the cortex and subcortical areas. Subependymal nodules show variable signals on T1 and T2 images, but are usually enhanced. Nodules show low signal on MRI when calcified, and most calcification occurs before age 20. SEGAS is a low-grade tumor, with an incidence rate of 10%~15% in TS. It often occurs in the foramen mengele, with continuous growth and visible enhancement. The presence or absence of septal growth is the best marker for distinguishing SEGAS from subependymal nodules. Treatment usually favors cerebrospinal fluid shunt. Common TS related lesions are numerous, including retinal hamartomas, cardiac rhabdomyomas, renal cysts, and angiomyolipomas, pulmonary lymphangiomyomatosis, subthyroid fibromas, and skin lesions such as gray leaf and shark skin.
灰质异位
灰质异位是由于正常神经元从室管膜下区向皮质迁移的过程被中断所致,这种中断可由胎儿在发育过程中的某些损伤引起。灰质异位可表现为结节状或条带状。在MRI上,室管膜下的异位灰质结节与大脑灰质信号强度相同,无强化、无钙化。患者常表现为癫痫发作和发育迟缓,而轻症患者可无症状。
Ectopic gray matter is caused by the interruption of the migration of normal neurons from the subependymal region to the cortex. Heterotopic gray matter may appear nodular or banded. On MRI, the suboependymal heterotopic gray matter nodule had the same signal intensity as the gray matter in the brain, without enhancement or calcification. Patients often present with seizures and developmental delays, while mild cases may be asymptomatic.
TORCH感染
TORCH感染包括弓形虫、风疹、巨细胞病毒和单纯性疱疹病毒感染。巨细胞病毒为最常见的 TORCH感染,可致室管膜下和脑实质钙化,在CT上与结节性硬化症相似。 弓形虫病也可致颅内钙化,但分布无规律,较少 分布于脑室周。该类患者通常可伴发小头畸形和 神经元迁移异常,如多小脑回和巨脑回。患者通 常表现为智力低下、癫痫和听觉受损。
TORCH infections include toxoplasma, rubella, cytomegalovirus and herpes simplex. Cytomegalovirus is the most common TORCH infection, causing subependymal and parenchymal calcification similar to tuberous sclerosis on CT. Toxoplasmosis can also cause intracranial calcification, but its distribution is irregular and rarely distributed around the ventricle. Patients with this condition often have microcephaly and abnormal neuronal migration, such as multiple cerebellar gyrus and giant gyrus. Patients commonly present with mental retardation, epilepsy, and hearing impairment.
转移性疾病
室管膜下转移瘤可继发于原发性中枢神经系统病变,或颅外恶性肿瘤经血行转移。易于向室管膜下播散的原发性中枢神经系统病变包括:多形性胶质母细胞瘤、髓母细胞瘤、室管膜瘤、原发性中枢神经系统淋巴瘤、生殖细胞肿瘤、松果体细胞瘤和脉络丛肿瘤。多种 颅外肿瘤均可转移至室管膜下和脉络丛,尤其是乳腺癌。
Subependymal metastases may be secondary to primary central nervous system lesions, or extracranial malignancies may metastasized by blood. Primary central nervous system lesions that tend to spread subependymally include glioblastoma multiformis, medulloblastoma, ependymoma, primary central nervous system lymphoma, germ cell tumor, pineal cell tumor, and choroid plexus tumor. Many kinds of extracranial tumors can metastasize to the subependymal and choroid plexus, especially breast cancer.
