2008 ICD-9-CM Volume 1 Diagnosis Codes Home > Diseases Of The Nervous System And Sense Organs 320-389 > Hereditary And Degenerative Diseases Of The Central Nervous System 330-337 > Other Cerebral Degenerations 331.* > 2008 ICD-9-CM Diagnosis 331.5 Idiopathic normal pressure hydrocephalus (inph)  On October 1, 2008 the 2009 ICD-9-CM codes came into effect. Therefore, this code may be out of date. The 2009 version of ICD-9-CM 331.5 can be accessed here. 331.5 is a specific code that can be used to specify a diagnosis 331.5 contains 3 index entries View the ICD-9-CM Volume 1 331.* hierarchy ICD9Data's sister site ProcedureCodes.com launches with the 2008/09 CPT® codes - read more on the ICD9Data.com blog. 331.5 also known as: Normal pressure hydrocephalus NOS 331.5 excludes: congenital hydrocephalus (742.3) secondary normal pressure hydrocephalus (331.3) spina bifida with hydrocephalus (741.0) Index entries containing 331.5: Hydrocephalus (acquired) (external) (internal) (malignant) (noncommunicating) (obstructive) (recurrent) 331.4 normal pressure 331.5 idiopathic (INPH) 331.5 secondary 331.3 INPH (idiopathic normal pressure hydrocephalus) 331.5