脑白质病变病因有以下几种：
1. 中毒性：
2. 遗传性：
3. 脱髓鞘：
4. 感染性：
5. 代谢紊乱：
6. 血管性：
7. 肿瘤性：
8. 脑积水：
网友[飘过的云]：
heroin vapor inhalation toxicity (海洛因吸入中毒)：
病因与病理：不纯海洛因放在铝箔上加热，可能产生了某种神经毒性物质。使受累脑白质产生海绵状变性（spongiform degeneration）。治疗：对症支持，辅酶Q及维生素可能有效。
影像学：Involvement of the cerebellum and the posterior limb of the internal capsule, with sparing of the anterior limb, appears to be a characteristic finding in this condition, helping to distinguish it from other causes of leukoencephalopathy such as toluene toxicity or reversible posterior leukoencephalopathy.
第一例：参考文献：Neuroimaging Features of Heroin Inhalation Toxicity: "Chasing the Dragon" （ AJR 2003; 180:847-850）
可以看出和第一例有类似的影像学特征。
男性37岁病人，但是他几乎完全恢复了。
参考文献：Toxic leukoencephalopathy after intravenous consumption of heroin and cocaine with unexpected clinical recovery （ J Neurol (1999) 246 :850–851）
甲苯是一种脂溶性芳香族碳氢化物，作为一种有机溶剂广泛运用于工业中，稀释剂、粘合剂、喷雾剂、涂漆等中都含有它。长期吸入甲苯后，经肺进入血液循环，通过亲脂的血脑屏障，从而对脑产生损害。
影像特点：可先出现侧脑室旁的白质病变，再累及半卵园中心皮层下的白质，若接触时间更长（平均8.1年），可出现丘脑对称性T2低信号。（The focal preservation of gray matter-white matter differentiation in the subcortical white matter in our patients with diffuse changes indicates that white matter changes start in the periventricular area and then extend into the subcortical white matter.），但丘脑对称性T2低信号机制尚不明：继发于脱髓鞘和轴突丢失的铁沉积是最可能的机制。（The deposition of iron caused by demyelination and axonal loss seems to be the most probable mechanism for thalamic hypointensity on T2-weighted images in toluene-containing solvent abuse.）
参考文献：Cranial MR Findings in Chronic Toluene Abuse by Inhalation（American Journal of Neuroradiology 23:1173-1179, August 2002）
接触甲苯3年：
A and B, Bilateral, symmetric hyperintensity is present in the parietal periventricular white matter (arrowheads). Note that gray matter-white matter differentiation is preserved. The widths of the cerebral sulci are normal. A suggests that the hyperintense findings may be caused by terminal myelination, which is a normal MR imaging finding in children. However, B shows that the lesions extend to the bilateral centrum semiovale, indicating that hyperintense findings were true lesions rather than terminal myelination.
接触甲苯6年： A, High signal intensity is seen in the centrum semiovale (arrows) on both sides. The peripheral cerebral white matter and gray matter-white matter differentiation are preserved.
B, High-signal-intensity changes involve the frontal and parietal periventricular white matter (arrowheads). The pattern of white matter changes is compatible with that of the restricted type. Note that the lateral ventricles and cerebral sulci are enlarged.
A, Symmetric hypointensity is present in the thalami (arrows). Symmetric hyperintensity exists in the posterior limbs of the internal capsule (arrowheads).
B, At the level of the posterior fossa, generalized increased signal intensity in the cerebellar white matter emphasizes the dentate nucleus (arrowheads).
C, At the level of midbrain, red nuclei (arrows) and substantia nigra (arrowheads) are hypointense.
D, Diffuse high-signal-intensity in the centrum semiovale causes loss of gray matter-white matter differentiation. Gray matter-white matter differentiation is preserved only in the subcortical-frontal white matter (arrow). The cerebral sulci are mildly dilated.
相对少见，通常是意外或自杀性服毒或服用假酒。甲醇在体内能代谢成更具神经毒性的甲醛（formaldehyde）和甲酸（formic acid）。通常最先的临床表现是视力减退，可出现严重的神经系统症状和后遗症。血气分析示严重的高阴离子代谢性酸中毒。特异性的治疗：给予乙醇，和甲醇竞争乙醇脱氢酶，阻止甲醇代谢成更具神经毒性的甲醛和甲酸。
影像学特点：The most characteristic MR findings in methanol toxicity are bilateral putaminal necroses, which may have varying degrees of hemorrhage。including severe alterations of subcortical white matter and central gray matter alteration with sparing of peripheral gray matter.
参考文献：CT and MR Imaging Findings in Methanol Intoxication（American Journal of Neuroradiology 27:452-454, February 2006）
甲氨蝶呤是一种常用化疗药：
MTX is a cell cycle-specific agent that inhibits the enzyme dihydrofolate reductase, preventing the conversion of folic acid to tetrahydrofolic acid and inhibiting cell replication. Both high-dose intravenous MTX and intrathecal MTX are associated with demyelination, white matter necrosis, loss of oligodendroglia, axonal swelling, microcystic encephalomalacia, and atrophy relatively selective for the deep cerebral white matter。
The incidence of acute MTX neurotoxicity ranges from 3–10% and varies with the dose and route of administration of MTX.
影像学：不对称性，局限性。以半卵园中心为主。
参考文献：Acute Methotrexate Neurotoxicity: Findings on Diffusion-Weighted Imaging and Correlation with Clinical Outcome (American Journal of Neuroradiology 25:1688-1695, November-December 2004)
cocaine(可卡因)中毒和精神药物滥用中毒
患者1有滥用可卡因史，患者2有精神药物滥用史。
影像学特点:Axial fluid attenuated inversion recovery (FLAIR) magnetic resonance imaging sequences of the brain from patient 1 (A) and patient 2 ( B ).Both scans show evidence of diffuse symmetrical white matter changes involving the periventricular region and extending superiorly to involve the corona radiata.
病理特点：Myelin pallor in frontal (A)and parietal ( B ) white matter,contrasted with normal myelin staining intensity in internal capsule (C) and cerebellum (D). Note preservation of subcortical U fibres in the frontal and parietal white matter. (All stained with
Luxol-Fast Blue.)There was relative sparing of the subcortical U fibres but the changes became progressively more severe from superficial to deep (fig 2, panels A and ( B ).Cerebellar and brain stem white matter were not involved (fig 2D).
编辑：西门吹血
