Normal Pressure Hydrocephalus

• Normal pressure hydrocephalus is a slow, progressive disorder with symptoms such as abnormal gait, dementia and urinary incontinence. Ataxia is rarely observed. Gait is bradykinetic, shuffling and broad based.
• Urinary symptoms are often presented as frank incontinence. 
• Dementia: In patient with NPH, dementia is characterized by memory loss (prominent) and bradyphrenia. Other deficits are decreased attention, inertia, and forgetfulness. 
• Comorbidity is common in patients with NPH with diseases such as cerebrovascular disease.

Though some symptoms of normal pressure hydrocephalus mimic Alzheimer’s disease and Parkinson’s disease, the combination of dementia, urinary incontinence and abnormal gait in conjunction is not common in either disease. Thus, the diagnosis of NPH must be specific.

• Personal history: Medical professional inquire the patient about the medical and mental problems, family history, life-style, and medications. Physical examination of the patient forms the first step to manage NPH. Some neuropsychological tests are also performed to assess the symptoms of dementia. 
• Laboratory tests: There is no specific test available to diagnose NPH. They primarily focus on assessing the symptoms of the disease. 
• Imaging: CT scan and MRI of the head cannot confirm NPH, though the ventricular enlargement can be observed in these images. Citernography highlights the amount of absorption of the CSF. In order to establish the diagnosis of NPH, MRI and CT scan must show Evan’s index of 0.3. One or more of the symptoms such as temporal horn enlargement, periventricular edema or signal changes and fourth ventricular flow void can help confirm NPH [6].

• Medical care: Patient with normal pressure hydrocephalus does not respond significantly to levodopa or dopamine agonist challenge.
• Surgical care: Surgical CSF shunting is performed to manage NPH. Detailed testing must be done before and after the drainage of CSF. After the shunt surgery, there is significant improvement in the gait and mental status. The improvement in the gait of the patient can be assessed by videotaping the movement before and after the shunting. Another method to manage NPH is external lumbar drainage (ELD). In ELD, the clinicians use indwelling CSF catheter. The drainage catheter is placed for 3 days, which allows the body, sufficient time to return the neuronal function [9] [10].

Prognosis of normal pressure hydrocephalus is variable. Permanent neurological deficit/death is reported in 6% of all cases, with surgery requiring in 22% of the cases. There is a good long-term survival rate of 39% [7].

Complications

Shunt surgery can cause complications such as catheter breakage, cerebral infarct, infection, seizures, catheter breakage and in some cases even death in up to 10 % of the patients [8].

About 50% of the patients with NPH have idiopathic cause. Other secondary causes are head injury, meningitis, tumors, previously compensated congenital hydrocephalus and subarachnoid hemorrhage [2].

Normal pressure hydrocephalus affects the elderly with prevalence ranging from 3.3 per 100,000 (age: 50 to 59 years), 49.3 per 100,000 (age: 60 to 69 years) and 181.7 per 100,000 (age: 70 to 79 years). In a study in Japan, NPH is seen in 2.9% of the elderly subjects, while data from a Norwegian study showed the incidence of 5.5 in every 100,000 [3] [4] [8].

The clinical symptoms of NPH result from the distortion of the central portion of the corona radiata. This alteration is believed to occur due to the distended ventricles.

Nuclear imaging studies indicate the interstitial edema of the white matter in the brain and compression of the brainstem structures leading to impaired bloodflow, which manifests as dysfunction of gait and urinary incontinence. There is also a distortion of the periventricular limbic system, causing dementia in such patients [5].

1. Reducing the risk of head injury. Wearing the safety helmet while biking, skiing or rollerblading.
2. Quitting smoking. 
3. Having a healthy life-style with exercise and a healthy diet [10].

Hydrocephalus is a condition when there is accumulation of surplus cerebrospinal fluid (CSF) in the ventricles of the brain, and the drainage and absorption of extra CSF is compromised. In order to compensate this excess fluid, the ventricles enlarge causing several symptoms of normal pressure hydrocephalus (NPH).

This phenomenon is mostly seen in older patients, with the average age of patients being above 60 years. NPH develops slowly, and affects the parts of brain that control the bladder, the legs, and the cognitive functions such as memory, problem solving, speaking and reasoning. This decline of the cognitive process can cause dementia. Other symptoms of NPH are urinary incontinence, and abnormal gait. Since the symptoms of NPH mimic those of Alzheimer’s disease and Parkinson’s disease, the diagnosis of this disease remains a challenge [1].

Definition

Normal pressure hydrocephalus (NPH) is generally seen in patients with ages 60 and above. This disease develops slowly and affects the brain, bladder and legs. Loss of cognitive functions such as memory, problem solving, speaking and reasoning are affected by NPH. 

Cause

Though half of the patient with NPH have idiopathic cause, the secondary causes are head injury, meningitis, subarachnoid hemorrhage and tumors.

Symptoms

The common symptoms of the NPH are dementia, abnormal gait and urinary incontinence. 

Diagnosis

Family history and personal history detail the symptoms of the disease, allowing for the diagnosis of NPH. Physical examination of the patient forms the first step to manage the disorder. Though there is no specific lab test available to diagnose NPH, some imaging tests can be useful in correct diagnosis.

Treatment

Surgery is the most effective treatment modality to manage NPH. 

1. Hakim S, Adams RD. The special clinical problem of symptomatic hydrocephalus with normal cerebrospinal fluid pressure. Observations on cerebrospinal fluid hydrodynamics. J Neurol Sci. Jul-Aug 1965;2(4):307-27.
2. Graff-Radford NR, Godersky JC. Symptomatic congenital hydrocephalus in the elderly simulating normal pressure hydrocephalus. Neurology. Dec 1989;39(12):1596-60
3. Brean A, Eide PK. Prevalence of probable idiopathic normal pressure hydrocephalus in a Norwegian population. Acta Neurol Scand. Jul 2008;118(1):48-53. 
4. 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. 
5. Hamlat A, Adn M, Sid-ahmed S, et al. Theoretical considerations on the pathophysiology of normal pressure hydrocephalus (NPH) and NPH-related dementia. Med Hypotheses. 2006;67(1):115-23. Epub 2006 Mar 13.
6. Gyldensted C. Measurements of the normal ventricular system and hemispheric sulci of 100 adults with computed tomography. Neuroradiology. Dec 31 1977;14(4):183-92.
7. Pujari S, Kharkar S, Metellus P, et al. Normal pressure hydrocephalus: long-term outcome after shunt surgery. J Neurol Neurosurg Psychiatry. 2008 Nov;79(11):1282-6. Epub 2008 Mar 20.
8. Shprecher D, Schwalb J, Kurlan R. Normal pressure hydrocephalus: diagnosis and treatment. Curr Neurol Neurosci Rep. 2008 Sep;8(5):371-6.
9. Williams MA, Razumovsky AY, Hanley DF. Comparison of Pcsf monitoring and controlled CSF drainage diagnose normal pressure hydrocephalus. Acta Neurochir Suppl. 1998;71:328-30.
10. Lumbar infusion test for the investigation of normal pressure hydrocephalus, NICE Interventional Procedure Guideline (June 2008)

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