LAUSR

We read with great interest the article by Totsune et al. presenting the detailed clinicoradiological data of an iNPH (Idiopathic normal pressure hydrocephalus) subject from the prodromal phase to the definite diagnosis including data of 16 years. However, we would like to make some more comments hoping to provide a better understanding of the results of this crucial report. Chronic ventriculomegaly is a known entity in adult hydrocephalus practice, however, it constitutes a highly heterogeneous group, differing substantially in terms of responsible etiologies, coexisting clinical manifestations, and treatment approaches. For instance, among them, LOVA (Long-standing overt ventriculomegaly) is an intriguing entity that is hypothesized to emerge subclinically in early childhood, but manifests in late adulthood after the slow decompensation phase. More recently, a terminology of “AVIM” (Asymptomatic ventriculomegaly with features of idiopathic normal pressure hydrocephalus) was proposed defining a prodromal phase of iNPH. The authors followed eight asymptomatic elderly subjects with hydrocephalus and DESH findings on MRI for 4–8 years; and detected the development of iNPH clinic in two of them. In the latter study, they found 52% of patients with AVIM (n = 52) developed iNPH within 3 years. The report by Totsune et al. presents more remarkable results demonstrating the occurrence of the neuroimaging clues of iNPH 13 years prior to the diagnosis. In conclusion, the authors discuss that the prediagnostic phase of iNPH may be longer than previously thought. An interesting point was that the finding of DESH had begun to occur 8 years before diagnosis and complete DESH was apparent 4 years prior to diagnosis. However, as far as we understand, the clinic of iNPH had also initiated 6–7 years before diagnosis. Taken together, an intriguing discussion may be that if the precise definition of the patient at the period after the occurrence of DESH should be “AVIM” or the “early phase of iNPH.” Therefore, we wonder if the authors include data regarding the neurological assessment of the patient or NPH-GS (iNPH Grading Scale) scores (if available) at that period which would clarify these discussions. Besides, in addition to the radiological signs, the clinical evaluation method of these patients also constitutes an important topic. Urinary symptoms and cognitive deteriorations are encountered frequently in the elderly population and subjects with various other causes of dementia which makes the clinical suspicion of iNPH challenging in the clinical practice. Besides, the discrimination between normal and abnormal gait in this population may be strictly hard and it is demonstrated that agreement on gait patterns of iNPH is not high, differing according to the professions or degrees of experience. Considering that the early shunt placement is associated with a better prognosis, making the diagnosis in the early period of the disease is critical. From our own experiences and the limited literature data, we think that the presence of subjective symptoms (albeit objective symptoms are lacking) is also important and should alert the clinicians in the setting of supportive neuroimaging signs of iNPH. Finally, the presentation of this case may also indicate the need for future prospective studies of longer follow-up periods. The clarification of this observation of ventriculomegaly in the preclinical phase of the disease in a large number of patients may provide contributions to our current understanding of the pathophysiology of iNPH and also present crucial clinical applications.