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Normal-pressure hydrocephalus (NPH), also called communicating hydrocephalus.
A syndrome of impaired gait and balance, urinary urgency or incontinence, cognitive impairment, and enlarged cerebral ventricles that usually occurs in persons older than 60 years of age.
The incidence increases with age, and most patients are over the age of 60.
Prevalence is reported to be less than 1% in persons under the age of 65.
Normal pressure hydrocephalus is estimated to affect about 5 per 100,000 people, with rates increasing with age.
There are two categories of normal pressure hydrocephalus: idiopathic and secondary.
Both are forms of communicating hydrocephalus, meaning that there is no obstruction to the flow of spinal fluid within the ventricular system, and they have similar signs and symptoms.
Secondary normal pressure hydrocephalus can develop at any age and is a consequence of intracranial hemorrhage, head trauma, infection, or treatment for a brain tumor or other brain disorders.
The idiopathic form develops later in life and without any known cause.
The idiopathic form of normal pressure hydrocephalus is more common and more challenging to diagnose in secondary form.
Both forms of communicating hydrocephalus have no obstruction to the flow of spinal fluid within the ventricular system, and they have similar signs and symptoms.
In contrast, idiopathic normal pressure hydrocephalus develops later in life and without any known cause.
Intracranial, pressure, waveforms and compliance are abnormal and the use of normal pressure refers to normal or minimally, elevated CSF pressure measurements obtained during lumbar puncture or ventriculostomy placement in the context of enlarged ventricles.
The prevalence of the disorder is estimated to be as high as 1.5% among those 65 to 70 years of age and increases with age, reaching as high as 7.7% among persons 86 years of age or older.
Neurological impairment becomes more severe, and death is more likely the longer idiopathic normal pressure hydrocephalus remains untreated.
Hyperlipidemia, hypertension, diabetes, obesity, alcohol use disorder, and other risk factors are tentatively associated with idiopathic, normal pressure hydrogen, but have an underlying relationship that is unknown.
Presentation usually in the seventh decade of life.
Excess cerebrospinal fluid (CSF) causes the ventricles to enlarge.
The increased pressure inside the head compresses surrounding brain tissue and leads to neurological complications.
It manifests as a classic triad of symptoms: urinary incontinence, dementia, and gait deviations.
Hakim’s triad of gait instability, urinary incontinence, and dementia is typical manifestation of the distinct entity normal-pressure hydrocephalus.
Normal-pressure hydrocephalus may be associated with focal neurological deficits, such as abducens nerve palsy and vertical gaze palsy (Parinaud syndrome).
It is essentially a clinical diagnosis supported by neuro imaging.
Gait disturbance exists characterized by broad-based, slow, and short stepping with a tendency to fall when turning.
The onset of cognitive decline typically develops after gait dysfunction, with both sub cortical and frontal features prevailing associated with apathy, lack of concern, impaired executive function, and psychomotor slowing.
patient may have difficulty with short-term memory and activities of daily living resembling neurogenic dementia.
Remote memory is usually preserved.
Dementia without gait impairment is uncommon.
The full symptom triad is present in only 2/3 of affected patients, but impaired gait and balance occur in more than 90% of patients.
The gait and balance impairment involve difficulty in integrating motor and sensory input and executing normal gait patterns and postural reflexes.
The findings distinguish it from gait abnormalities that characterize cerebella disorders and sensory ataxia.
The gait in patients with normal pressure hydrocephalus is often wide based and non-stable, with decreased step height and stride length, and may incorporate a degree of shuffling.
Patients may have difficulty standing from a sitting position without using their arms to push off, maybe unable to easily initiate walking on may tend to freeze mid stride during walking.
Instability, while turning is common, as our falls. gait velocity is slow, typically less than 1 m/s, but leg strength, sensation, and reflexes are normal.
Treatment: surgical placement of a ventriculoperitoneal shunt to drain excess CSF into the lining of the abdomen where the CSF will eventually be absorbed.
Shunt surgery for idiopathic normal pressure hydrocephalus improves gait plus velocity by 30% on average, and disability is reduced with approximately one in three patients becoming functionally independent within the first six months of surgery, when compared with patients who do not have a shunt or who had programmable CSF shunts that were inactive mode to create a placebo condition.
Ventriculoperitoneal, ventriculoatrial, and lumbarperitoneal shunt systems have similar efficacy.
Programmable magnetic shunt valves can be adjusted non-invasively to regulate the amount of CSF drainage
Often misdiagnosed as Parkinson’s disease or Alzheimer’s disease.
The diagnose is ultimately realized on improvement of symptoms after spinal fluid drainage.
Gait deviations are usually the first symptom.
Gait disturbances are seen in most patients and is caused by expansion of the lateral ventricles to impinge on the corticospinal tract motor fibers.
The typical gait abnormality manifests as a broad-based, slow, short-stepped, stuck to the floor appearance.
The gait abnormalities resemble those of Parkinson disease, and can be classified as mild, marked, or severe.
Gait impairment includes the feeling that feet are glued to the floor.
Patients have difficulty in motor planning, especially turning, with increased falls.
Not associated with tremor.
Dementia presents as progressive cognitive impairment.
Dementia present in 60% of patients at time of treatment is caused by changes predominantly at the frontal lobe and the subcortex.
Mental impairments include: planning, organization, executive function deficits attention, concentration, managing finances, taking medications, driving, keeping track of appointments, daytime sleeping, short-term memory impairments, and psychomotor slowing.
Cognitive features include generalized slowing, deficits in attention, concentration, or memory.
Late stage manifestations include: apathy, reduced drive, slowed thinking, and reduced speech.
Apathy acts like a lack of motivation, mimics depression, delaying diagnosis.
Urinary incontinence appears late in the disease process.
Urinary incontinence is present in 50% of patients at time of treatment.
The urinary dysfunction includes urgency and difficulty inhibiting bladder emptying due to the tracer overactivity.
The urinary dysfunction begins as increased frequency often at night, and progresses to urge incontinence and subsequently permanent incontinence.
Urinary urgency occurs more frequently than urinary incontinence.
Every day, the body makes roughly 600–700 ml of CSF, and about the same amount is reabsorbed into the bloodstream.
Hydrocephalus is due to an imbalance between the amount of fluid produced and its absorption rate.
Enlarged ventricles put increased pressure on the adjacent cortical tissue and cause varying effects in the patient, including distortion of the fibers in the corona radiata.
Enlarged ventricles lead to an increase in intracranial pressure (ICP).
The ICP remains slightly elevated, and the CSF pressure reaches a high normal level of 150 to 200 mm H2O.
Because measurements of ICP are not usually elevated, 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.
Possible causes:
An imbalance exists between production and resorption of CSF.
The resistance to CSF outflow is often elevated.
It is not caused by overproduction of CSF or obstruction of CSF flow at the ventricles.
The underlying cause of primary NPH has not been identified.
Primary NPH affects adults age 40 years or older, most commonly affecting the elderly.
Secondary NPH can affect persons of any age and occurs due to conditions such as subarachnoid hemorrhage, meningitis, brain surgery, brain radiation, or traumatic brain injury.
The Evan’s index is the ratio of maximum width of the frontal horns to the maximum width of the inner table of the cranium and is used to determine the presence of hydrocephalus.
An Evan’s index more than 0.31 indicates hydrocephalus.
Diagnostic criteria for primary NPH are:
Gradual onset after age 40 years
symptoms duration of ≥ 3–6 months
clinical evidence of gait or balance impairment
and impairment of cognition or urinary incontinence
Imaging from brain MRI or CT is needed to demonstrate enlarged ventricles and no macroscopic obstruction to cerebrospinal fluid flow.
Imaging criteria should show enlargement of at least one of the temporal horns of lateral ventricles, and falx cerebri impingement, evidence of altered brain water content, or normal flow at the cerebral aqueduct and fourth ventricle.
The diagnostic distinction between normal and enlarged ventricular size by cerebral atrophy is difficult to determine.
As many as 80% of cases are unrecognized and treatment is not applied due to the difficulty of making the diagnosis.
Imaging should also reveal the absence of any cerebral mass lesions or any signs of obstructions.
All patients with NPH have enlarged ventricles.
But, not all elderly patients with enlarged ventricles have primary NPH: Cerebral atrophy can cause enlarged ventricles.
The Miller Fisher test involves a high-volume lumbar puncture (LP) with removal of 30–50 ml of CSF.
Among individuals with idiopathic normal pressure hydrocephalus who have a response to temporary CSF drainage, shunting resulted in significant improvements at three months in gait, velocity and a measure of gait and balance, but not in measures of cognition or incontinence (Luciano MG).
With the Miller Fisher test Gait and cognitive function are typically tested just before and within 2–3 hours after the LP to assess for signs of improvement.
An LP should show normal or mildly elevated CSF pressure.
CSF analysis have normal cell contents, glucose levels, and protein levels.
CSF shunting is the first-line treatment.
Ventriculoperitoneal (VP) shunts, which drain CSF fluid to the peritoneal cavity,are the most common type of shunts.
Shunts have adjustable valves allowing fine-tuning of CSF drainage.
NPH symptoms reportedly improve in 70–90% of patients with CSF shunt:
Gait symptoms improve in ≥ 85% patients, cognitive symptoms improve in up to 80% of patients with early surgery, and incontinence improves in up to 80% of patients.
With late surgery only in ≤ 50–60% of patients with shunt implanted late in disease course have improvement in incontinence.
Adverse effects of shunting include subdural hematoma (12%) and orthostatic headache.
The most likely patients to show improvement with shunting are those who show only gait deviation, mild or no incontinence, and mild dementia.
Complications of shunts11%: shunt failure, infections such as ventriculitis, shunt obstruction, over- or under-drainage, and development of a subdural hematoma.
The most common serious complications of shunt surgery are infection, brain injury from catheter misplacement, and subdural hematoma.
In a study of 193 patients with idiopathic normal pressure hydrocephalus over a year: Found more than 91% of the patients who underwent surgery had no complications in 6% had major complications requiring an extended hospital stay or further surgery.
Sustained symptom abatement after shunt surgery has been reported for approximately 90% of patients with idiopathic normal pressure hydrocephalus.
Functional decline overtime occurs primarily impatient older than 80 years of age.
Delay in the diagnosis and treatment of idiopathic normal pressure hydrocephalus by more than six months is it associated with worsening of their symptoms and less improvement afterward.
Mortality among patients who surgery is delayed by more than six months is 2.6 times as high as those among those who underwent surgery sooner.
No medications are effective for primary NPH.
The majority of cases are primary NPH.
The incidence of NPH increases with advancing age, and most patients are over the age of 60. Its prevalence is reported to be less than 1% in persons under the age of 65, and up to 3% for persons aged 65 or older.
No difference in incidence is seen between genders.
NPH is thought to account for between 2 and 6% of patients with dementia.
Early diagnosis is crucial in order to avoid irreversible cortical damage.
Because there are no reliable markers for a definitive diagnosis of idiopathic normal pressure hydrocephalus, guidelines recommend tests that assess the physiology of CSF circulation or the clinical response to CFS drainage to determine whether improvement after shunt surgery is likely.
Lumbar infusion testing with Ringers lactate can assess CSF volume high pressure relationship, and CSF outflow resistance to predict shunt responsiveness.
While large volume lumbar puncture was the earliest invasive diagnostic test in predicting response to shunt surgery, external lumbar drainage (ELD) is being used with increased frequency.
An indwelling CSF catheter in lieu of repeated lumbar punctures.
The drainage catheter is generally left in place for 3 days, allowing sufficient time for return of neuronal function: about 30 to 50 mL of CSF can be removed in an outpatient setting.
This method carries a higher risk of meningeal infection but may allow for a more accurate prognosis.(1-2%).
The gait and balance are assessed shortly before and within several hours after the CSF removal to determine improvement, and likely a likelihood for the benefit of shunting.
In a prospective study of 151 patients with suspected idiopathic NPH, all patients underwent ELD.
Patients with clinical improvement after ELD were offered shunt surgery, 90% of whom improved.
Others have confirmed the positive predictive value of improvement after ELD.
Negative predictive value of ELD: In one study, 64% of patients who underwent shunt surgery had improvement, despite a negative ELD result.