Normal pressure hydrocephalus (NPH)

Normal pressure hydrocephalus (NPH) is another potentially reversible cause of “dementia” or rather memory problems in the elderly. NPH is characterized by the triad of gait disturbance, urinary incontinence and memory problems. The dementia in NPH is of the subcortical type meaning that it is mostly characterized by psychomotor retardation (patients are slow to respond), unlike cortical dementias like Alzheimers disease they do not have language deficits (aphasia), inability to do learned things (apraxia) or agnosia.

The etiology of NPH is still not fully elucidated but it is thought to involve some obstruction to the normal flow of the cerebrospinal fluid (CSF). This obstruction may be due to previous history of meningitis or CNS trauma. When you image these patients with either a CT scan or a MRI scan, one finds the ventricles are dilated (large enlarged ventricles) but there is not much corresponding cortical (brain0 atrophy. This is against what is found in cortical dementias like Alzheimers disease where apart from the ventricles been dilated and enlarged, the brain also is shrunken (atrophy).

So in which patients should the diagnosis of NPH be entertained? Mostly these are patients who are elderly and who have had a subacute onset of memory problems accompanied by difficulty in walking (patients who have NPH have a characteristic gait (they walk slowly and stiffly, we call their gait as magnetic gait). They may or may not have urinary incontinence (the entire triad may not be present in all the patients). Neurologists entertain the diagnosis of NPH if they see a patient with the above symptoms and if the imaging is characteristic.

To confirm the diagnosis though requires further testing. Normally what we do is a therapeutic as well as diagnostic spinal tap. What does that mean you may ask?

Well we bring the patient into the hospital and do a spinal tap. Before the tap is done the patient is examined to determine the memory deficits. A timed walking test is carried out ( we make the patient walk a fixed distance and measure the time taken to do so ). Then a good amount of spinal fluid is removed about 20-30 cc. The pressure of the spinal fluid is measured at that time and in a typical patient of NPH it should be normal (hence the name normal pressure hydrocephalus). Once the spinal fluid has been removed the patient is again tested. Has the memory improved. We make the patient walk the same distance as before. If now the walk is much faster and steadier, then we document a positive reponse to large volume CSF removal. Our diagnosis of NPH is now strengthened and there has also been a therapeutic response to the procedure ( remember I told you the test is both diagnostic and therapeutic).

Before I usually subject the patient to a surgical option for more definitive treatment, I usually like to repeat the above test at least two more times. If there is a consistent positive response to large volume CSF removal, then I feel confident in going ahead and asking the neurosurgeon to place a shunt.  What is a shunt? Well a shunt is a device which as the name suggests shunts the spinal fluid from the brain into the peritoneal cavitiy (the gut). It has a valve which can be set to open at a particular pressure. So whenever the CSF pressure rises above that pressure, the valve shall open and the extra spinal fluid shall be shunted from the brain into the gut.

Simple device but does have its own risk of complications. Shunts can get infected, they can get dislodged from the brain and start migrating, they may get obstructed and have to be replaced etc. Hence before I advise putting any sort of hardware into the brain, I try to be as sure as possible that my patient indeed does have NPH and not a cortical dementia like Alzheimers or Parkinsons disease (as these do not respond to shunt placement).

It is Friday the 20th, I am off home on my vacation but shall be keeping the blog active. Please do contact me if you have any questions or want me to discuss something particular.

Personal Regards,

Nitin Sethi, MD

12 thoughts on “Normal pressure hydrocephalus (NPH)

  1. Dr. Sethi, thank you for the information re NPH. My 74 year old sister recently had a radioisotope study to rule out NPH. Her gait and urinary problems have been progressive for about 3 years but her gait improved for several days following the study. When her symptoms first started, I thought that large lipoma on the back of her neck might be a cause of spinal obstruction and have subsequently read that a lipoma such as hers might be indicative of intracranial lipomas as well. I don’t suppose one showed up on her MRI. What do you think of the the possibility that the lipoma in her cervical spine area could be the cause of the blockage? In such a patient would you recommend removal of the lipoma before shunting? Thank you for your attention to my question.

  2. Dear Sara,
    thank you for writing in. That is truly a tough question for me to answer since I have not examined your sister nor have seen her scans. NPH is a commmunicating hydrocephalus also called as non-obstructive hydrocephalus meaning thereby that there is no observable obstruction to the flow of spinal fluid. So I am not sure if the lipoma is indeed the cause of her symptomatology.
    Usually when it comes to NPH, it is the gait which improves the most after shunting while the urinary incontinence improves the least.
    Hope that sheds some light on your query.

    Personal Regards,
    Nitin Sethi, MD

  3. Dear Dr Sethi,

    Thank you for the nice review of NPH. Is not Parkinson Disease a classic type of a SUBcortical dementia though? You call it a cortical dementia. Thank you.

    Steve Schwartz, MD

    1. Dear Dr. Schwartz,
      thank you for writing in. You raise a good point. Parkinson disease dementia (PDD) usually occurs late in the disease course of classical Parkinson disease. As it is accompanied with signs and symptoms of basal ganglia involvment (rigidity, bradykinesia) it does look like a sub-cortical dementia with patients presenting with psychomotor retardation and slowing. It though is not a sub-cortical dementia in the classical sense as autopsy studies have revealed cortical as well as sub-cortical involvement.
      I personally feel the distinction between cortical and sub-cortical dementia is not perfect though it helps in classifying patients.
      Personal Regards,
      Nitin Sethi, MD

  4. Dear Dr Sethi

    I am a 43 year old male living with adult onset hydrocephalus as a result of meningo-encephalitis (as a complication of mumps) which I contracted at age 16 (1981).

    During the last lumbar puncture, the intracranial pressure was raised, albeit mildly (2003).
    Since then, I have had a few worrying new manifestations of the disease i.e. daytime sleepiness (severe) loss of hearing, slight imbalance, memory problems (slight) and a feeling of being detached from my surroundings.

    The neurosurgeons I have consulted with (I live in South Africa) are still reluctant to place a shunt. I suppose my main question is (and please try to understand my bitterness) how far does my mental function have to deteriorate before the advantages of shunt placement outweigh the risks? Surely it must have a detrimental effect on the brain to constantly be under increased pressure? Is the continued raised ICP not the reason for the worsening of my condition? I can feel the deterioration, and it is causing me significant psychological stress.

    Thanks for your time.

  5. Dear Mr. Wagner,
    thank you for writing in. Broadly speaking hydrocephalus is of two kinds: obstructive and non-obstructive. Obstructive hydrocephalus is caused by some physical obstruction to the flow of spinal fluid while non-obstructive also called communicating hydrocephalus is not caused by any obstruction, rather there is a problem with CSF flow dynamics (absorption of CSF is impaired).
    There can be many causes of both obstructive as well as non-obstructive hydrocephalus. It is usually the obstructive hydrocephalus which presents with increased intra-cranial pressure and hence at times needs surgical correction or a shunt placement so that CSF flow can be diverted.
    Your doctors shall be the best people to determine what kind of hydrocephalus you have, is it indeed causing raised ICP and does it need a shunt placement.
    I hope I have been able to shed some light on this topic for you. Please feel free to write again.

    Personal Regards,
    Nitin Sethi, MD

  6. Dear Dr Sethi
    Thanks a lot for your lucid explanation on NPH.For last four years my father in law (78 years old) is suffering from this(?).We had done three spinal taps so far,but it has not improved any of the symptoms.He has all the three symptoms the gait( worsening),urinary incontinence ( used to 7 to 8 days in a month but from this new year it is continuous and now he has lost bowel control as well) and dementia( was occasional but now it is more frequent like 7 to 8 days in a month).Added to this he cannot do any logical functions for example cannot instruct the maid to prepare more food if he had eaten all.This is his new fad.He has become very food fussy.Either he overeats or eats very less. Neither he can use any numbers, cannot make a phone call or cannot transact any money.
    Is it normal for NPH?All the literature is about AD I do not think he has that.Is there any literature on NPH that talks about stages?Is there any solution to his problems?
    Or is it due to old age?doctors tell me to expect partial improvement, but i cannot not see any.It saddens and depresses me a lot
    Thanks once again

    1. Dear Bhushana,
      thank you very much for writing in. Sometimes it is very difficult to determine that the cause of the patient’s cognitive decline is indeed normal pressure hydrocephalus and not another neurodegenerative condition such as Alzheimer’s dementia. One may do a high volume spinal tap and the patient may show little or no improvement. Some of these patients may have dual pathology (meaning they indeed have a primary dementia such as Alzheimer’s disease). Still every attempt should be made to rule out normal pressure hydrocephalus, since it is one of the few causes of reversible “dementia” (as you know most of the other dementias are irreversible and progress till the patient becomes completely bed-ridden and dependent upon caregivers for all activities of daily living).
      Normal pressure hydrocephalus does not have any well demarcated stages. My advise would be to continue to follow up with his doctors, at times time yields the answer.
      Personal Regards,
      Nitin Sethi, MD

  7. Dear Dr. Sethi,
    I am the caregiver of my 57 year old brother who was born in 1951 with hydrocephalus, which arrested on it’s own. A shunt was not used, they were not perfected at that time from what I have read.
    He worked for 35 years at a local hospital, drove a car, bowled, etc. until a year ago. He retired and had to stop driving due to his neck lowering and some vision problems.
    In September of ’08 he began experiencing problems walking and then getting up from a sitting position. He has been in a nursing home for the past 2 weeks and is deteriorating rapidly. He cannot walk without PT assistance.
    He has had a brain MRI, spinal cat scans, blood work, abdominal ultrasound, venous doppler (for lyphedema) and lymphedema therapy. All testing was normal in that his brain MRI was no different than over a year ago. Is this just a normal deterioration of his congenital condition?? He has some confusion and urinary/ bowel problems just in the last two weeks.
    Any advice is welcome. Thank you, Susan

  8. Dear Susan,
    thank you for writing in. I am sorry to hear about your brother’s recent deterioration of health. It is indeed difficult for me to answer your question since I have not examined him and do not have the benefit of looking at his recent scans.
    From what you tell me I am not certain if this can be attributed to his arrested hydrocephalus. His “neck lowering” (from this I assume he has weakness in his neck muscles and is unable to hold his head up) localizes the problem to either the brain or high up in the spinal cord.
    Your brother’s case history though intrigues me. Email me on I shall email you back with my office number. Maybe if we can talk on the phone, I shall be able to give you some constructive suggestions.

    Personal Regards,
    Nitin Sethi, MD

  9. Dear Doctor,
    Is just leaking urine concidered incontence? WHat about mostly when sneezing, coughing or when you let your bladder get to full and you leak some of the urine but not all. Is this concidered incontinence for the purposes of NPH? How about unexplainable spotting of feces on a daily basis? I have that ,but I also have hemroids which bother me sometmes. ANd can demtia come and go? Can I be on the ball one day and feel “dead” on the next day. I have always been an enthusiastic teacher of young children, but now i often feel absolutely no enthusiasm. I just want to go home and go to bed. But maybe I am just depressed. I almost caused several car accidents by not apyhing attention to what I was doing, but maybe I am just an ari -hjaed.Does depression occur wiht NPH? My Dr. suspects NPH but I can athink of reasons for all of my symptoms besides NPH.

  10. Hello dr sethi,

    Thank you very much for the above useful information. My father who is 60 year old is suffering from NPH and doctors have performed NPH on him thrice 2 years ago and also advised for shunt but as read in your article it has adverse effects too, we have not done that. My question is that, is this illness related to depression or is caused due to depression? I have searched for this question everywhere but did not find any answer to it. And should NPH be done everytime as the liquid is accumulated if yes then after what time it should be done? Though it is very painful treatment.

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s