Disproportionately Enlarged Subarachnoid Space Hydrocephalus in Idiopathic Normal-Pressure Hydrocephalus and Its Implication in Pathogenesis

Abstract

Idiopathic normal-pressure hydrocephalus (iNPH) has become socially significant in Japan. Japanese guidelines for iNPH in 2011 described the diagnostic importance of "disproportionately enlarged subarachnoid space hydrocephalus" (DESH) on magnetic resonance imaging (MRI). However, some patients with iNPH have equivocal or no features of DESH. To clarify the diversity of MRI findings in iNPH, we classified iNPH into three types based on MRI findings. Using this, we investigate predictable MRI findings for shunt effectiveness in iNPH. A total of 83 patients with suspected iNPH who were treated with shunt surgery were reviewed in this study. All patients had a positive cerebrospinal fluid (CSF) tap test. Among the 83 patients, DESH was noted in 64 %, incomplete DESH in 23 %, and no DESH in 13 % (see Fig. 3). Among the three types of incomplete DESH, incomplete DESH-v (ventricle) was 0 %, DESH-c (convexity) in 13 %, and DESH-s (Sylvian fissure) in 10 %. A high improvement rate after the shunt surgery was noted in the DESH and incomplete DESH-s groups, showing 73.5 % and 87.5 %, respectively. The non-DESH group showed a fairly large improvement of 63.6 %. A common MRI finding in DESH and incomplete DESH-s was high convexity tightness with ventriculomegaly. This combination was promising for shunt effectiveness in patients with suspected iNPH. Further study is necessary to elucidate the pathogenesis.

The prevalence and clinical associations of disproportionately enlarged subarachnoid space hydrocephalus (DESH), an imaging feature of idiopathic normal pressure hydrocephalus in community and memory clinic based Singaporean cohorts

“…Previous reports also suggested the importance of high convexity tightness as the most predictive feature of the three components of DESH, for surgical outcomes in terms of Mini-Mental State Examination score, gait disturbance, and the total scoring [19]. Another study also reported that high convexity tightness combined with ventriculomegaly was a predictor for shunt effectiveness in patients with suspected iNPH [27]. Similarly, it has been reported that volumetry of CSF spaces in the ventricle and supra-Sylvian regions could differentiate iNPH from AD and vascular dementia [28,29].…”

Absence of Disproportionately Enlarged Subarachnoid Space Hydrocephalus, a Sharp Callosal Angle, or Other Morphologic MRI Markers Should Not Be Used to Exclude Patients with Idiopathic Normal Pressure Hydrocephalus from Shunt Surgery

“…The prevalence of DESH in this study is lower in comparison with previous publications. 8,13,28 This outcome might be because in accordance with the international diagnostic guidelines, the components of the DESH phenomenon were not part of the diagnostic criteria for the evaluated iNPH group. Furthermore, we graded sulcal compression at the vertex as obliterated or not, meaning that patients who did not show complete sulcal obliteration but still had some degree of compression in conjunction with Sylvian dilation were graded as not having DESH.…”

The Tight Medial and High Convexity Subarachnoid Spaces Is the First Finding of Idiopathic Normal Pressure Hydrocephalus at the Preclinical Stage

“…Ishikawa et al 16) reported that symptomatic probable iNPH consists of three groups (DESH, incomplete DESH, and non DESH). The radiological features of incomplete DESH were defined as two definite and one equivocal of the three DESH findings (TMC, enlarged Sylvian fissure, and ventriculomegaly).…”