Asymptomatic ventriculomegaly with features of idiopathic normal pressure hydrocephalus on MRI (AVIM)
Disproportionately enlarged subarachnoid space hydrocephalus (DESH) is a pattern of communicating hydrocephalus characterized by crowding of the sulci superiorly near the vertex accompanied by enlargement of CSF spaces more inferiorly, particularly in the Sylvian fissures 1. It is a prominent feature of idiopathic normal pressure hydrocephalus (iNPH) and is a central component of the Japanese iNPH diagnostic guidelines 2.
Multiple, but not all, studies have found that the presence of DESH is predictive of shunt-response in patients with iNPH 1,3.
The finding of DESH without neurologic symptoms has been termed asymptomatic ventriculomegaly with features of idiopathic normal pressure hydrocephalus on MRI (AVIM)4. It is felt by some authors that AVIM is actually a pre-clinical form of iNPH 5.
1. Virhammar J, Laurell K, Cesarini KG, Larsson EM. Preoperative prognostic value of MRI findings in 108 patients with idiopathic normal pressure hydrocephalus. (2014) AJNR. American journal of neuroradiology. 35 (12): 2311-8. doi:10.3174/ajnr.A4046 - Pubmed
2. Mori E, Ishikawa M, Kato T, Kazui H, Miyake H, Miyajima M, Nakajima M, Hashimoto M, Kuriyama N, Tokuda T, Ishii K, Kaijima M, Hirata Y, Saito M, Arai H. Guidelines for management of idiopathic normal pressure hydrocephalus: second edition. (2012) Neurologia medico-chirurgica. 52 (11): 775-809. Pubmed
3. Hashimoto M, Ishikawa M, Mori E, Kuwana N. Diagnosis of idiopathic normal pressure hydrocephalus is supported by MRI-based scheme: a prospective cohort study. (2010) Cerebrospinal fluid research. 7: 18. doi:10.1186/1743-8454-7-18 - Pubmed
4. Mori E, Ishikawa M, Kato T, Kazui H, Miyake H, Miyajima M, Nakajima M, Hashimoto M, Kuriyama N, Tokuda T, Ishii K, Kaijima M, Hirata Y, Saito M, Arai H. Guidelines for management of idiopathic normal pressure hydrocephalus: second edition. (2012) Neurologia medico-chirurgica. 52 (11): 775-809. Pubmed
5. Iseki C, Kawanami T, Nagasawa H, Wada M, Koyama S, Kikuchi K, Arawaka S, Kurita K, Daimon M, Mori E, Kato T. Asymptomatic ventriculomegaly with features of idiopathic normal pressure hydrocephalus on MRI (AVIM) in the elderly: a prospective study in a Japanese population. (2009) Journal of the neurological sciences. 277 (1-2): 54-7. doi:10.1016/j.jns.2008.10.004 - Pubmed