[Object] The aim of this study was to discuss the underlying pathophysiology in failure of neuroendoscopic ventriculostomy during treatment of "non-communicating hydrocephalus" with reference to findings from analyses of specific cerebrospinal fluid (CSF) dynamics in the immature brain. [Materials and Method] Prospective analysis was performed for 12 hydrocephalic neonates and infants suspected as non-communicating hydrocephalus as the initial impressions on magnetic resonance imaging (MRI) to undergo the preoperative CSF dynamic studies using cine-mode MRI and computed tomography (CT) ventriculo-cisternography. [Results] Of the 12 cases, 9 (75%) in the prospective study of CSF dynamics revealed misdiagnosis compatible with "communicating hydrocephalus". The pattern in the ventriculo-cisternography in all these cases revealed intra-parenchymal predominant CSF flow (minor pathway) in the CSF dynamics, rather than passage in the major pathway. Four patients were selected as displaying definitive indications for neuroendoscopic ventriculostomy. Postoperatively, all 4 patients were improved with stabilized intracranial pressure (ICP), as in the condition of "post-endoscopic ventriculostomy arrested hydrocephalus". However, symptoms of increased ICP recurred in all 4 patients at a mean of 5.5 weeks (range, 4-9 weeks). Ventriculo-peritoneal (V-P) shunt was subsequently performed in all 12 patients except one who underwent craniotomy for cyst removal, with improvements noted in each case. [Discussion and Conclusion] The high incidence of "failure of neuroendoscopic ventriculostomy" in treatment for hydrocephalus in the neonatal and infantile periods may depend on the specific CSF dynamics, in which the major CSF pathway has not developed and the minor pathway plays a significant role in the individual maturation process. This clinical evidence may be supported by the hypothesis that CSF dynamics develops according to evolutionary theory, from an immature brain as seen in animals with minor CSF pathway predominance, i.e., "Minor Pathway Hydrocephalus" towards a mature adult human brain together with completion of the major CSF pathway, i.e., "Evolution Theory in CSF Dynamics".