eMedicine Specialties > Neurology > Movement and Neurodegenerative Diseases

Normal Pressure Hydrocephalus

Author: Arif I Dalvi, MD, Neurologist, NorthShore University Health System Medical Group
Coauthor(s): Ashvini P Premkumar, MD, Clinical Instructor of Neurology, Associate Director, Movement Disorders Center, University of Chicago School of Medicine, Northshore University Health Systems
Contributor Information and Disclosures

Updated: Nov 17, 2009

Introduction

Background

Normal pressure hydrocephalus (NPH) is a clinical symptom complex characterized by abnormal gait, urinary incontinence, and dementia. It is an important clinical diagnosis because it is a potentially reversible cause of dementia. First described by Hakim in 1965, NPH describes hydrocephalus in the absence of papilledema and with normal cerebrospinal fluid (CSF) opening pressure on lumbar puncture.1

Pathophysiology

NPH differs from other causes of adult hydrocephalus. An increased subarachnoid space volume does not accompany increased ventricular volume. Clinical symptoms result from distortion of the central portion of the corona radiata by the distended ventricles. This may also lead to interstitial edema of the white matter and impaired blood flow, as suggested in nuclear imaging studies. The periventricular white matter anatomically includes the sacral motor fibers that innervate the legs and the bladder, thus explaining the abnormal gait and incontinence. Compression of the brainstem structures (ie, pedunculopontine nucleus) could also be responsible for gait dysfunction, particularly the freezing of gait that has been well described. Dementia results from distortion of the periventricular limbic system.

The term normal pressure hydrocephalus was based on the finding that all 3 patients reported by Hakim and Adams showed low CSF pressures at lumbar puncture, namely 150, 180, and 160 mm H2 O. However, an isolated CSF pressure measurement by lumbar puncture clearly yields a poor estimation of the real intracranial pressure (ICP) in patients with NPH.

Hakim first described the mechanism by which a normal or high-normal CSF pressure exerts its effects. Using the equation, Force = Pressure X Area, increased CSF pressure over an enlarged ependymal surface applies considerably more force against the brain than the same pressure in normal-sized ventricles. Normal pressure hydrocephalus may begin with a transient high-pressure hydrocephalus with subsequent ventricular enlargement. With further enlargement of the ventricles, CSF pressure returns to normal; thus the term NPH, at least in view of the initial pathophysiologic events, is a misnomer. Intermittent intracranial hypertension has been noted in some patients.

Some authors prefer the term extraventricular obstructive hydrocephalus. They believe that the initial event is diminished CSF absorption at the arachnoid villi. This obstruction to CSF flow leads to transient high-pressure hydrocephalus with subsequent ventricular enlargement. As the ventricles enlarge, CSF pressure returns to normal.

Frequency

International

  • A Norwegian study of a population of 220,000 inhabitants found a prevalence of probable idiopathic NPH of 21.9 per 100,000 population and an incidence of 5.5 per 100,000 population; the investigators suggested that those numbers be regarded as minimum estimates.2
  • A Japanese study found radiological and clinical features consistent with idiopathic NPH in 2.9% of community-dwelling elderly subjects.3
  • In another Japanese study, elderly individuals (age >65) underwent MRI and the prevalence of NPH was 1.4%.4
  • The prevalence of NPH may be as high as 14% in extended care facility patients.5

Race

Race is not associated with the development of NPH.

Sex

Gender is not associated with the development of NPH.

Age

NPH is predominantly a disease of the elderly, and thus with the aging of the population, its recognition is of increased importance. The Norwegian study mentioned above showed the incidence and prevalence of NPH increasing with age.2

Clinical

History

Patients present with a gradually progressive disorder. As noted above, the classic triad consists of abnormal gait, urinary incontinence, and dementia. The gait disturbance is typically the earliest feature noted and considered to be the most responsive to treatment. The primary feature is thought to resemble an apraxia of gait. True weakness or ataxia is typically not observed.

The gait of NPH is characterized as bradykinetic, broad based, magnetic, and shuffling. The urinary symptoms of NPH can present as urinary frequency, urgency, or frank incontinence. While incontinence can result from gait disturbance and dementia, in a study by Sakakibara and colleagues, 95% of patients had urodynamic parameters consistent with detrusor overactivity.6

The dementia of NPH is characterized by prominent memory loss and bradyphrenia. Frontal and subcortical deficits are particularly pronounced. Such deficits include forgetfulness, decreased attention, inertia, and bradyphrenia. The presence of cortical signs such as aphasia or agnosia should raise suspicion for an alternate pathology such as Alzheimer disease or vascular dementia. However, comorbid pathology is not uncommon with advancing age. In one study, more than 60% of patients with iNPH had cerebrovascular disease.7 In another similar study, more than 75% had AD pathology at the time of shunt surgery.8

Patients commonly present with a gait disorder and dementia. On neurologic examination, pyramidal tract findings may be present in addition to the above findings.

Causes

Normal pressure hydrocephalus may occur due to a variety of secondary causes but may be idiopathic in approximately 50% of patients. Secondary causes of NPH include head injury, subarachnoid hemorrhage, meningitis, and CNS tumor. Another potential cause could be previously compensated congenital hydrocephalus.9

More on Normal Pressure Hydrocephalus

Overview: Normal Pressure Hydrocephalus
Differential Diagnoses & Workup: Normal Pressure Hydrocephalus
Treatment & Medication: Normal Pressure Hydrocephalus
Follow-up: Normal Pressure Hydrocephalus
Multimedia: Normal Pressure Hydrocephalus
References
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References

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  2. Brean A, Eide PK. Prevalence of probable idiopathic normal pressure hydrocephalus in a Norwegian population. Acta Neurol Scand. Jul 2008;118(1):48-53. [Medline].

  3. Hiraoka K, Meguro K, Mori E. Prevalence of idiopathic normal-pressure hydrocephalus in the elderly population of a Japanese rural community. Neurol Med Chir (Tokyo). May 2008;48(5):197-99; discussion 199-200. [Medline].

  4. Tanaka N, Yamaguchi S, Ishikawa H, Ishii H, Meguro K. Prevalence of possible idiopathic normal-pressure hydrocephalus in Japan: the Osaki-Tajiri project. Neuroepidemiology. 2009;32(3):171-5. [Medline].

  5. Marmarou A, Young HF, Aygok GA. Estimated incidence of normal pressure hydrocephalus and shunt outcome in patients residing in assisted-living and extended-care facilities. Neurosurg Focus. Apr 15 2007;22(4):E1. [Medline].

  6. Sakakibara R, Uchiyama T, Kanda T, Uchida Y, Kishi M, Hattori T. [Urinary dysfunction in idiopathic normal pressure hydrocephalus]. Brain Nerve. Mar 2008;60(3):233-9. [Medline].

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  28. Tsakanikas D, Relkin N. Normal pressure hydrocephalus. Semin Neurol. Feb 2007;27(1):58-65. [Medline].

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Further Reading

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Keywords

normal pressure hydrocephalus, NPH, occult hydrocephalus, extraventricular obstructive hydrocephalus, abnormal gait, urinary incontinence, dementia, intracranial pressure, ICP, CSF pressure, cerebrospinal fluid pressure, extraventricular obstructive hydrocephalus, gait apraxia, gait disorder, parkinsonism

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Contributor Information and Disclosures

Author

Arif I Dalvi, MD, Neurologist, NorthShore University Health System Medical Group
Arif I Dalvi, MD is a member of the following medical societies: European Neurological Society and Movement Disorders Society
Disclosure: Novartis Honoraria Speaking and teaching

Coauthor(s)

Ashvini P Premkumar, MD, Clinical Instructor of Neurology, Associate Director, Movement Disorders Center, University of Chicago School of Medicine, Northshore University Health Systems
Ashvini P Premkumar, MD is a member of the following medical societies: American Academy of Neurology and Movement Disorders Society
Disclosure: Nothing to disclose.

Medical Editor

Joseph F Hulihan, MD, Vice President, Medical Affairs, Ortho-McNeil Janssen Scientific Affairs, LLC
Joseph F Hulihan, MD is a member of the following medical societies: American Academy of Neurology, American Clinical Neurophysiology Society, American Epilepsy Society, American Headache Society, and American Medical Association
Disclosure: Johnson & Johnson Salary Employment; Johnson & Johnson Stock Employment

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Nestor Galvez-Jimenez, MD, MSc, MHA, 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, and Movement Disorders Society
Disclosure: Nothing to disclose.

CME Editor

Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.

Chief Editor

Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.

 
 
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