英语语法分析

Once hydrocephalus is ruled out, the degree of tonsillar ectopia and the presence of hydromyelia are evaluated, than the treatment may be performed, based on the indication of clinical symptoms.

一旦排除脑积水，需评价小脑下疝下移程度以及是否出现脊髓积水，基于临床症状可实施治疗。