Hydrocephalus, Normal Pressure
- Normal pressure hydrocephalus (NPH) is a clinical triad of gait instability, incontinence, and dementia (mnemonic: wet, wobbly, wacky); originally described by Hakim in 1957
- Two forms of the disorder: idiopathic and obstructive (the latter usually due to physical insult—posttrauma, meningitis, or subarachnoid hemorrhage)
- There is an absence of papilledema on clinical exam and normal cerebrospinal fluid (CSF) pressures at lumbar puncture
- Idiopathic NPH (iNPH) primarily affects persons >60 years; extremely rare before 40 years
- Consider NPH in ground level falls of patients >60 years. In one study, over 10% had findings of NPH (1).
- iNPH form primarily affects elderly, at least >40 years of age.
- Secondary form can occur at any age.
- Estimated to be a contributing factor in 6% of all cases of dementia
Varies from 1.1% to 2.2%. Arriving at accurate data is hampered by uncertain diagnosis (2).
Ranges from 1.3% in the >65 years age group and increases to 5.9% in those 80 years and older. It is estimated that approximately 700,000 are affected in the United States (compared with 400,000 with multiple sclerosis) and 2,000,000 in Europe (2).
Etiology and Pathophysiology
- Idiopathic form is a communicating hydrocephalus, a disorder of decreased CSF absorption (not overproduction). In iNPH, the leading theory suggests that poor venous compliance impairs the subarachnoid granulations’ ability to maintain baseline removal of CSF. In secondary NPH, scarring is likely.
- The result is a pressure gradient between the subarachnoid space and ventricular system.
- CSF production decreases in the face of an increased pressure set point (but still in excess of the amount of CSF absorbed).
- Elevated pressure distends ventricles and compresses the brain parenchyma, disrupting the normal cerebral blood flow with resulting ischemic changes leading to subsequent tissue damage and loss.
- Some believe that the idiopathic form is a result of persistently insufficient removal of CSF by immature subarachnoid granulations from childhood.
- Secondary NPH may result from the following:
- Head trauma (most common)
- Subarachnoid hemorrhage
- Resolved acute meningitis
- Chronic meningitis (tuberculosis, syphilis)
- Paget disease of the skull
Secondary form is due to head trauma, subarachnoid hemorrhage, meningitis, or encephalitis.
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Domino, Frank J., et al., editors. "Hydrocephalus, Normal Pressure." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2020. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116839/all/Hydrocephalus__Normal_Pressure.
Hydrocephalus, Normal Pressure. In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2020. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116839/all/Hydrocephalus__Normal_Pressure. Accessed May 29, 2023.
Hydrocephalus, Normal Pressure. (2020). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (27th ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116839/all/Hydrocephalus__Normal_Pressure
Hydrocephalus, Normal Pressure [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2020. [cited 2023 May 29]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116839/all/Hydrocephalus__Normal_Pressure.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Hydrocephalus, Normal Pressure ID - 116839 ED - Domino,Frank J, ED - Baldor,Robert A, ED - Golding,Jeremy, ED - Stephens,Mark B, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116839/all/Hydrocephalus__Normal_Pressure PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -