Editing Normal pressure hydrocephalus (section)

==Diagnosis==
[[File:CT of Evan's index.jpg|thumb|190px|Evan's index is the ratio of maximum width of the frontal horns to the maximum width of the inner table of the cranium. An Evan's index more than 0.31 indicates hydrocephalus.<ref name="IshiiKawamata2010">{{cite journal | vauthors = Ishii M, Kawamata T, Akiguchi I, Yagi H, Watanabe Y, Watanabe T, Mashimo H | title = Parkinsonian Symptomatology May Correlate with CT Findings before and after Shunting in Idiopathic Normal Pressure Hydrocephalus | journal = Parkinson's Disease | volume = 2010 | pages = 1–7 | date = March 2010 | pmid = 20948890 | pmc = 2951141 | doi = 10.4061/2010/201089 | doi-access = free }}</ref>]]
Patients with suspected idiopathic NPH should have at least one of the symptoms in Hakim's triad (gait disturbance, urinary incontinence, and cognitive impairment) in addition to ventricular enlargement on neuroimaging. An extensive and detailed patient history is required in order to exclude other diseases that may explain the patient's symptoms. Known causes of secondary NPH (head injury, meningitis, hemorrhage) should be ruled out prior to further investigation of idiopathic NPH.<ref name=":0"/>

The international evidenced-based diagnostic criteria for primary, or idiopathic, NPH are:<ref>{{Cite journal |last1=Nakajima |first1=Madoka |last2=Yamada |first2=Shigeki |last3=Miyajima |first3=Masakazu |last4=Ishii |first4=Kazunari |last5=Kuriyama |first5=Nagato |last6=Kazui |first6=Hiroaki |last7=Kanemoto |first7=Hideki |last8=Suehiro |first8=Takashi |last9=Yoshiyama |first9=Kenji |last10=Kameda |first10=Masahiro |last11=Kajimoto |first11=Yoshinaga |last12=Mase |first12=Mitsuhito |last13=Murai |first13=Hisayuki |last14=Kita |first14=Daisuke |last15=Kimura |first15=Teruo |date=2021-02-15 |title=Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus (Third Edition): Endorsed by the Japanese Society of Normal Pressure Hydrocephalus |journal=Neurologia Medico-Chirurgica |volume=61 |issue=2 |pages=63–97 |doi=10.2176/nmc.st.2020-0292 |issn=1349-8029 |pmc=7905302 |pmid=33455998}}</ref>
* Gradual onset after age 40 years, symptoms duration of ≥ 3–6 months, clinical evidence of gait or balance impairment, and impairment of cognition or urinary incontinence
* Imaging from [[magnetic resonance imaging]] (MRI) or [[computed tomography]] (CT) is needed to demonstrate enlarged ventricles and no macroscopic obstruction to cerebrospinal fluid flow.  Imaging should show an enlargement to at least one of the [[temporal horns of lateral ventricles]], and impingement against the [[falx cerebri]] resulting in a callosal angle ≤ 90° on the [[Coronal plane|coronal]] view, showing evidence of altered brain water content, or normal active flow (which is referred to as "flow void") at the [[cerebral aqueduct]] and [[fourth ventricle]].

{|class="wikitable"
|+Typical imaging findings in normal pressure hydrocephalus versus brain atrophy.<ref name="Damasceno2015">{{cite journal | vauthors = Damasceno BP | title = Neuroimaging in normal pressure hydrocephalus | journal = Dementia & Neuropsychologia | volume = 9 | issue = 4 | pages = 350–355 | year = 2015 | pmid = 29213984 | pmc = 5619317 | doi = 10.1590/1980-57642015DN94000350 }}</ref>
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|align="center"|[[File:Normal pressure hydrocephalus versus atrophy, NPH.jpg|335px]]
|align="center"|[[File:Normal pressure hydrocephalus versus atrophy, CA.jpg|333px]]
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! Normal pressure hydrocephalus !! [[Brain atrophy]]
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| Preferable projection ||colspan=2| [[Coronal plane]] at the level of the [[posterior commissure]] of the brain.
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| Modality in this example || [[CT scan|CT]] || [[Magnetic resonance imaging|MRI]]
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| CSF spaces over the convexity near the vertex (red ellipse [[File:Red ellipse.png|20px]]) || Narrowed convexity ("tight convexity") as well as medial cisterns || Widened vertex (red arrow) and medial cisterns (green arrow)
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| Callosal angle (blue {{font color|DodgerBlue|'''V'''}}) || [[Acute angle]] || [[Obtuse angle]]
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| Most likely cause of [[leucoaraiosis]] (periventricular signal alterations, blue arrows [[File:Flecha tesela.svg|25px]])
| Transependymal [[cerebrospinal fluid]] diapedesis
| Vascular encephalopathy, in this case suggested by unilateral occurrence
|}

MRI scans are the preferred imaging. The distinction between normal and enlarged ventricular size by [[cerebral atrophy]] is difficult to ascertain. Up to 80% of cases are unrecognized and untreated due to difficulty of diagnosis.<ref name="The differential diagnosis and trea">{{cite journal | vauthors = Kiefer M, Unterberg A | title = The differential diagnosis and treatment of normal-pressure hydrocephalus | journal = Deutsches Ärzteblatt International | volume = 109 | issue = 1–2 | pages = 15–25; quiz 26 | date = January 2012 | pmid = 22282714 | pmc = 3265984 | doi = 10.3238/arztebl.2012.0015 }}</ref> Imaging should also reveal the absence of any cerebral mass lesions or any signs of obstructions. Although all patients with NPH have enlarged ventricles, not all elderly patients with enlarged ventricles have primary NPH. Cerebral atrophy can cause enlarged ventricles, as well, and is referred to as hydrocephalus ''ex vacuo''. For these reasons it's utmost important to note that Evan's index although commonly used in imaging is not very specific for NPH. One recent systematic review and meta-analysis suggests that callosal angle has high diagnostic performance and is commonly used together with Evan's index.<ref>{{Cite journal |last1=Park |first1=Ho Young |last2=Kim |first2=Minjae |last3=Suh |first3=Chong Hyun |last4=Lee |first4=Da Hyun |last5=Shim |first5=Woo Hyun |last6=Kim |first6=Sang Joon |date=2021-07-01 |title=Diagnostic performance and interobserver agreement of the callosal angle and Evans' index in idiopathic normal pressure hydrocephalus: a systematic review and meta-analysis |url=https://link.springer.com/article/10.1007/s00330-020-07555-5 |journal=European Radiology |language=en |volume=31 |issue=7 |pages=5300–5311 |doi=10.1007/s00330-020-07555-5 |pmid=33409775 |issn=1432-1084|url-access=subscription }}</ref>
[[File:Wikipedian getting a lumbar puncture (2006).jpg|thumb|Image of patient receiving lumbar puncture (LP). Cerebrospinal fluid (CSF) obtained from an LP can be tested to aid in the diagnosis of NPH.]]
The [[Miller Fisher test]] involves a high-volume [[lumbar puncture]] (LP) with removal of 30–50 ml of CSF. Gait and cognitive function are typically tested just before and within 2–3 hours after the LP to assess for signs of symptomatic improvement. The CSF infusion test can also be used to aid in diagnosis of NPH. During the CSF infusion test, a [[Ringer's lactate solution|ringer lactate]] solution is infused into a spinal needle while another spinal needle is used to record numerous CSF pressure variables including ICP, outflow resistance, and CSF formation rate.<ref>{{Cite journal |last1=Williams |first1=Michael A. |last2=Malm |first2=Jan |date=April 2016 |title=Diagnosis and Treatment of Idiopathic Normal Pressure Hydrocephalus |journal=Continuum (Minneapolis, Minn.) |volume=22 |issue=2 Dementia |pages=579–599 |doi=10.1212/CON.0000000000000305 |issn=1538-6899 |pmc=5390935 |pmid=27042909}}</ref> The tests have a [[positive predictive value]] over 90%, but a [[negative predictive value]] less than 50%. The LP should show normal or mildly elevated CSF pressure. CSF should have normal cell contents, glucose levels, and protein levels.<ref name="pmid20477715">{{cite journal | vauthors = Tarnaris A, Toma AK, Kitchen ND, Watkins LD | title = Ongoing search for diagnostic biomarkers in idiopathic normal pressure hydrocephalus | journal = Biomarkers in Medicine | volume = 3 | issue = 6 | pages = 787–805 | date = December 2009 | pmid = 20477715 | doi = 10.2217/bmm.09.37 }}</ref><ref name="pmid16160426">{{cite journal | vauthors = Marmarou A, Bergsneider M, Klinge P, Relkin N, Black PM | author-link3=Petra Klinge|title = The value of supplemental prognostic tests for the preoperative assessment of idiopathic normal-pressure hydrocephalus | journal = Neurosurgery | volume = 57 | issue = 3 Suppl | pages = S17–28; discussion ii–v | date = September 2005 | pmid = 16160426 | doi = 10.1227/01.neu.0000168184.01002.60 | s2cid=7566152}}</ref><ref>{{cite web | work = National Institute of Neurological Disorders and Stroke | date = 29 April 2011 | title = NINDS Normal Pressure Hydrocephalus Information Page | url = http://www.ninds.nih.gov/disorders/normal_pressure_hydrocephalus/normal_pressure_hydrocephalus.htm | access-date = 13 May 2011 | archive-url = https://web.archive.org/web/20161211234632/http://www.ninds.nih.gov/disorders/normal_pressure_hydrocephalus/normal_pressure_hydrocephalus.htm | archive-date = 11 December 2016 | url-status = dead }}</ref>