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Normal Pressure Hydrocephalus Workup

  • Author: Michael J Schneck, MD, MBA; Chief Editor: Selim R Benbadis, MD  more...
 
Updated: Jul 12, 2016
 

Laboratory Studies

After a detailed history and physical examination, further diagnostic testing is required to establish a diagnosis. In general, laboratory testing is unhelpful. However, imaging tests are invaluable in the diagnosis of this disease.

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Imaging Studies

In most cases of new onset neurologic symptoms, a CT scan of the brain is initially obtained. Although MRI is more specific than CT in NPH, a normal CT scan can exclude the diagnosis. CT and MRI findings in NPH include the following:

  • Ventricular enlargement out of proportion to sulcal atrophy, as shown in the image below
  • Prominent periventricular hyperintensity consistent with transependymal flow of CSF, also shown below
    T2-weighted MRI showing dilatation of ventricles o T2-weighted MRI showing dilatation of ventricles out of proportion to sulcal atrophy in a patient with normal pressure hydrocephalus. The arrow points to transependymal flow.
  • Prominent flow void in the aqueduct and third ventricle, the so-called jet sign, (presents as a dark aqueduct and third ventricle on a T2-weighted image where remainder of CSF is bright)
  • Thinning and elevation of corpus callosum on sagittal images
  • Rounding of frontal horns, shown below
    CT head scan of a patient with normal pressure hyd CT head scan of a patient with normal pressure hydrocephalus showing dilated ventricles. The arrow points to a rounded frontal horn.
  • A narrow CSF space at the high convexity/midline areas relative to Sylvian fissure size was recently shown to correlate with a diagnosis of probable or definite iNPH. [11]

To establish a diagnosis of NPH (and exclude hydrocephalus ex vacuo), an MRI or CT must show an Evan’s index of at least 0.3.[12] In addition, one or more of the following must also be present:

  • Temporal horn enlargement
  • Periventricular signal changes
  • Periventricular edema
  • Aqueductal/fourth ventricular flow void

Prominent medial temporal cortical atrophy favors a diagnosis of hydrocephalus ex vacuo and is related to Alzheimer disease or vascular dementia. Patients may occasionally be referred for treatment of NPH based on an imaging diagnosis of hydrocephalus. However, with hydrocephalus ex vacuo, transependymal flow is uncommon. In contrast, sulcal atrophy and significant white matter ischemic disease are commonly seen. See the images below.

This image shows ventriculomegaly, which is typica This image shows ventriculomegaly, which is typical in hydrocephalus ex vacuo.
This image shows cortical atrophy, which is the de This image shows cortical atrophy, which is the defining feature of hydrocephalus ex vacuo.

Additionally, the presence of abnormalities such as an Arnold Chiari malformation raise the possibility of a congenital hydrocephalus.

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Procedures

All patients with suspected NPH should undergo diagnostic CSF removal (either large volume lumbar puncture and/or external lumbar drainage [ELD]), which has both diagnostic and prognostic value (see Surgical Care). When the CSF opening pressure is greatly elevated, other causes of hydrocephalus should be considered, although CSF pressures may be transiently elevated in NPH. Improvement in symptoms with large volume drainage is supportive of the diagnosis of NPH.

ELD has a greater impact on brain volume expansion compared with lumbar puncture. In one study 20 patients with NPH based on clinical and radiological criteria were divided into 2 equal groups of 10 that underwent lumbar puncture or ELD. The median volume of CSF removed was 35 mL in patients who underwent lumbar puncture and 406 mL in patients who underwent ELD. Brain volume change was significantly larger in patients who underwent ELD than in patients who underwent lumbar puncture (p = 0.022) and correlated with the volume of CSF removal (r = 0.628, p = 0.004). Brain volume expansion was most pronounced adjacent to the lateral ventricles but was also detectable in the temporal and frontal regions. The median ventricular volume decreased after CSF removal. Ventricular volume reduction was more pronounced in patients who underwent ELD than in patients who underwent LP.[13]

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Contributor Information and Disclosures
Author

Michael J Schneck, MD, MBA Vice Chair and Professor, Departments of Neurology and Neurosurgery, Loyola University, Chicago Stritch School of Medicine; Associate Director, Stroke Program, Director, Neurology Intensive Care Program, Medical Director, Neurosciences ICU, Loyola University Medical Center

Michael J Schneck, MD, MBA is a member of the following medical societies: American Academy of Neurology, American Society of Neuroimaging, Stroke Council of the American Heart Association, Neurocritical Care Society

Disclosure: Received honoraria from Boehringer-Ingelheim for speaking and teaching; Received honoraria from Sanofi/BMS for speaking and teaching; Received honoraria from Pfizer for speaking and teaching; Received honoraria from UCB Pharma for speaking and teaching; Received consulting fee from Talecris for other; Received grant/research funds from NMT Medical for independent contractor; Received grant/research funds from NIH for independent contractor; Received grant/research funds from Sanofi for independe.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Nestor Galvez-Jimenez, MD, MSc, MHA The Pauline M Braathen Endowed Chair in Neurology, Chairman, Department of Neurology, Program Director, Movement Disorders, Department of Neurology, Division of Medicine, Cleveland Clinic Florida

Nestor Galvez-Jimenez, MD, MSc, MHA is a member of the following medical societies: American Academy of Neurology, American College of Physicians, International Parkinson and Movement Disorder Society

Disclosure: Nothing to disclose.

Chief Editor

Selim R Benbadis, MD Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, Tampa General Hospital, University of South Florida College of Medicine

Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Medical Association, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Cyberonics; Eisai; Lundbeck; Sunovion; UCB; Upsher-Smith<br/>Serve(d) as a speaker or a member of a speakers bureau for: Cyberonics; Eisai; Glaxo Smith Kline; Lundbeck; Sunovion; UCB<br/>Received research grant from: Cyberonics; Lundbeck; Sepracor; Sunovion; UCB; Upsher-Smith.

Additional Contributors

Arif I Dalvi, MD Director, Movement Disorders Center, NorthShore University Health System; Clinical Associate Professor of Neurology, University of Chicago Pritzker Medical School

Arif I Dalvi, MD is a member of the following medical societies: International Parkinson and Movement Disorder Society, European Neurological Society

Disclosure: Nothing to disclose.

Ashvini P Premkumar, MD Associate Director, Movement Disorders Center, NorthShore University HealthSystem, Clinical Instructor of Neurology, University of Chicago Pritzker Medical School

Ashvini P Premkumar, MD is a member of the following medical societies: American Academy of Neurology, International Parkinson and Movement Disorder Society

Disclosure: Nothing to disclose.

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T2-weighted MRI showing dilatation of ventricles out of proportion to sulcal atrophy in a patient with normal pressure hydrocephalus. The arrow points to transependymal flow.
CT head scan of a patient with normal pressure hydrocephalus showing dilated ventricles. The arrow points to a rounded frontal horn.
This image shows ventriculomegaly, which is typical in hydrocephalus ex vacuo.
This image shows cortical atrophy, which is the defining feature of hydrocephalus ex vacuo.
 
 
 
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