Normal pressure hydrocephalus

Normal pressure hydrocephalus
Classification and external resources
Specialty neurology
ICD-10 G91.2
ICD-9-CM 331.9, 331.5
DiseasesDB 9089
MedlinePlus 000752
eMedicine neuro/277 radio/479
Patient UK Normal pressure hydrocephalus
MeSH D006850

Normal pressure hydrocephalus (NPH), also termed symptomatic hydrocephalus, is a type of brain malfunction caused by expansion of the lateral cerebral ventricles and distortion of the fibers in the corona radiata. Its typical symptoms are urinary incontinence, dementia, and gait disturbance. CSF pressure is usually normal. Ventricles are chronically dilated.

The usual treatment is surgical installation of a ventriculoperitoneal shunt to drain excess CSF into the lining of the abdomen where the CSF will eventually be absorbed.

Types

There are two types of normal pressure hydrocephalus: idiopathic and secondary. The secondary type of NPH can be due to a subarachnoid hemorrhage, head trauma, tumor, infection in the central nervous system, or a complication of cranial surgery.[1]

Mechanism

NPH is caused by an increase in intracranial pressure (ICP) due to an abnormal accumulation of CSF in the ventricles of the brain, leading to ventriculomegaly. The intracranial pressure gradually falls but still remains slightly elevated, and the CSF pressure reaches a high normal level of 150 to 200 mm H2O. Measurements of ICP, therefore, are not usually elevated. Because of this, patients do not exhibit the classic signs that accompany increased intracranial pressure such as headache, nausea, vomiting, or altered consciousness, although some studies have shown pressure elevations to occur intermittently. However, enlarged ventricles put increased pressure on the adjacent cortical tissue and cause myriad effects in the patient. The classic symptom triad (gait disturbance, urinary incontinence, and dementia) was first described by Hakim and Adams in 1965.[2] NPH is often misdiagnosed as Parkinson's disease, Alzheimer's disease, or dementia, due to its chronic nature and nonspecific presenting symptoms.

Signs and symptoms

NPH may exhibit a classic triad of clinical findings (known as the Adams triad or Hakim's triad) of urinary incontinence, gait disturbance, and dementia (commonly referred to as "wet, wacky and wobbly" or "weird walking water").

Diagnosis

Diagnosis of NPH is usually first led by brain imaging, either CT or MRI, to rule out any mass lesions in the brain. This is then followed by lumbar puncture and evaluation of clinical response to removal of CSF. This can be followed by continuous external lumbar CSF drainage during 3 or 4 days.

Treatment

Patients with dementia who are confined to a nursing home and may have undiagnosed NPH can possibly become independent again once treated. So far only one study was able to evaluate the prevalence of NPH, both diagnosed and undiagnosed, among residents of assisted-living facilities, showing a prevalence in 9 to 14% of the residents.[8]

NPH may be relieved by surgically implanting a ventriculoperitoneal shunt to drain excess cerebrospinal fluid to the abdomen where it is absorbed. Once the shunt is in place, the ventricles usually diminish in size in 3 to 4 days, regardless of the duration of the hydrocephalus. Even though the ventricular swelling diminishes, only 21% of patients show a marked improvement in symptoms. The most likely patients to show improvement are those that show only gait disturbance, mild or no incontinence, and mild dementia.[9] A more recent study (2004) found better outcomes, concluding that if patients with idiopathic normal pressure hydrocephalus are correctly identified, shunt insertion yielded beneficial outcomes in 86% of patients, in either gait disturbance (81%), improved continence (70%), or both. They also observed that measurements in the diagnostic clinical triad, the cortical sulci size, and periventricular lucencies were related to outcome. However, other factors such as age of the patient, symptom duration, dilation of ventricles, and the degree of presurgical dementia were unrelated to outcome.[10]

Epidemiology

Recent population-based studies have estimated the prevalence of NPH to be about 0.5% in those over 65 years old, with an incidence of about 5.5 patients per 100,000 of people per year.[11][12] This is in accordance with comparable findings stating that although normal pressure hydrocephalus can occur in both men and women of any age, it is found more often in the elderly population, with a peak onset generally in the sixth to seventh decades.[5]

See also

Low pressure hydrocephalus

References

  1. National Institute of Neurological Disorders and Stroke. (2011, April 29). NINDS Normal Pressure Hydrocephalus Information Page. Retrieved from http://www.ninds.nih.gov/disorders/normal_pressure_hydrocephalus/normal_pressure_hydrocephalus.htm
  2. Adams, R. D.; Fisher, C. M.; Hakim, S.; Ojemann, R. G.; Sweet, W. H. (15 July 1965). "Symptomatic Occult Hydrocephalus with Normal Cerebrospinal-Fluid Pressure". New England Journal of Medicine. 273 (3): 117–126. doi:10.1056/NEJM196507152730301. PMID 14303656.
  3. Krauss, J.K., Faist, M., Schubert, M., Borremans, J.J., Lucking, C.H., & Berger, W. (2001). Evaluation of Gait in Normal Pressure Hydrocephalus Before and After Shunting. In R’uzicka, E., Hallett, M., & Jankovic, J. (Eds.), Gait Disorders (pp.301-309). Philadelphia, PA: Lippincott Williams & Wilkins.
  4. 1 2 Ropper, A.H. & Samuels, M.A. (2009). Adams and Victor’s Principles of Neurology (9th edition). New York, NY: McGraw-Hill Medical.
  5. 1 2 3 4 Younger, D.S. (2005). Adult Normal Pressure Hydrocephalus. In Younger, D.S. (Ed.), Motor Disorders (2nd edition) (pp. 581-584). Philadelphia, PA: Lippincott Williams & Wilkins.
  6. Tarnaris, Andrew; Toma, Ahmed K; Kitchen, Neil D; Watkins, Laurence D (1 December 2009). "Ongoing search for diagnostic biomarkers in idiopathic normal pressure hydrocephalus". Biomarkers in Medicine. 3 (6): 787–805. doi:10.2217/bmm.09.37. PMID 20477715.
  7. Marmarou, A; Bergsneider, M; Klinge, P; Relkin, N; Black, PM (September 2005). "The value of supplemental prognostic tests for the preoperative assessment of idiopathic normal-pressure hydrocephalus.". Neurosurgery. 57 (3 Suppl): S17–28; discussion ii–v. doi:10.1227/01.neu.0000168184.01002.60. PMID 16160426.
  8. Marmarou, Anthony; Young, Harold F.; Aygok, Gunes A. (1 April 2007). "Estimated incidence of normal-pressure hydrocephalus and shunt outcome in patients residing in assisted-living and extended-care facilities". Neurosurgical FOCUS. 22 (4): 1–8. doi:10.3171/foc.2007.22.4.2. PMID 17613187.
  9. Vanneste, J; Augustijn, P; Dirven, C; Tan, WF; Goedhart, ZD (January 1992). "Shunting normal-pressure hydrocephalus: do the benefits outweigh the risks? A multicenter study and literature review.". Neurology. 42 (1): 54–9. doi:10.1212/wnl.42.1.54. ISSN 0028-3878. PMID 1734324.
  10. Poca, Maria A.; Mataró, Maria; Matarín, Maria Del Mar; Arikan, Fuat; Junqué, Carmen; Sahuquillo, Juan (1 May 2004). "Is the placement of shunts in patients with idiopathic normal pressure hydrocephalus worth the risk? Results of a study based on continuous monitoring of intracranial pressure". Journal of Neurosurgery. 100 (5): 855–866. doi:10.3171/jns.2004.100.5.0855. PMID 15137605.
  11. Brean, A.; Eide, P. K. (1 July 2008). "Prevalence of probable idiopathic normal pressure hydrocephalus in a Norwegian population". Acta Neurologica Scandinavica. 118 (1): 48–53. doi:10.1111/j.1600-0404.2007.00982.x. PMID 18205881.
  12. Tanaka, Naofumi; Yamaguchi, Satoshi; Ishikawa, Hiroyasu; Ishii, Hiroshi; Meguro, Kenichi (1 January 2009). "Prevalence of Possible Idiopathic Normal-Pressure Hydrocephalus in Japan: The Osaki-Tajiri Project". Neuroepidemiology. 32 (3): 171–175. doi:10.1159/000186501. PMID 19096225.
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