**9. Supportive radiological investigations include**


Distinguishing dilated ventricles due to cerebral atrophy from NPH is difficult [19–22]. Focal atrophy is often indicative of a degenerative dementia, particularly if it is asymmetric (e.g., frontotemporal dementia) or is stereotypical, such as hippocampal atrophy in Alzheimer dementia. In NPH, the Sylvain fissures are disproportionately widened in comparison to the cortical sulci, which are flattened ("high tight" convexity). The appearance of a pulsation artifact in the cerebral aqueduct, or measurements of CSF stroke volume or velocity in the aqueduct using phase – contrast methods cannot be used alone to recommend shunt surgery, but can support the diagnosis of NPH and the need for further testing.

## **10. Classification of INPH**

Based on clinical and radiological features, INPH can be classified into probable, possible, and unlikely categories [19]. Probable criteria include age > 40, symptoms > 3 months, gait disorder, urinary incontinence or dementia, Evan's index > 0.3, temporal horn enlargement, aqueductal/Fourth ventricle flow void, and callosal angle > 40 [19]. If there is papilloedema, or absence of triad or no ventriculomegaly, the diagnosis of NPH is unlikely [19].

#### **11. Prognostic tests**

The tests which are done to ascertain the benefit of surgical intervention in INPH include: lumbar puncture which has a sensitivity of 26%, and specificity of 100%, extended lumbar drainage (sensitivity of 50–80% and specificity of 80%), measurement of CSF outflow resistance measurement (if >18 mm Hg/ml/min than 46% sensitive and 87% specific) and cine phase-contrast MRI (has insufficient evidence).

#### **12. Tap test**

In this, 40-50 ml of CSF is removed, and pre- and post-tap with the Gait Scale (walking score + step score + time score) is assessed. The step score is based on the

**61**

**17. Treatment**

*Normal Pressure Hydrocephalus*

*DOI: http://dx.doi.org/10.5772/intechopen.92058*

**13. External lumbar drainage**

**14. CSF infusion testing**

**15. ICP monitoring**

**16. Practice guidelines**

ness to MRI CSF flow studies [19, 20].

number of steps required for the patient to walk 10 m. Similarly, pre- and post-tap cognitive function assessed Folstein Mini Mental State Exam and within 2–4 hours after the CSF tap post-tap assessments are conducted. A significant response to the tap test indicates responsiveness to shunt surgery [23]. However, lack of significant response does not exclude shunt responsiveness because the tap test is specific, rather than sensitive. External lumbar drainage can be considered if iNPH is still

In this test, CSF is drained (10 to 15 cc per hour) for 72 hours and patient is assessed before and after the drainage (positive predictive value 90% and negative predictive value 78%). Positive ELD indicates good benefit with shunt. Negative ELD indicates low risk-benefit ratio. Neuropsychological testing before and after external lumbar drainage may also be helpful. Most publications have cited 72 hours of CSF drainage, although some centers drain CSF for shorter periods [19, 20]. This

Infusion testing for assessment of CSF hydrodynamics is commonly used in Europe to diagnose NPH, but is rarely used in the United States or Canada. In CSF infusion test, Ringer lactate is infused via one spinal needle and a second needle simultaneously records CSF pressure. One of the most consistent findings in NPH

The recordings in NPH reveal wave-form abnormalities similar to those originally described for brain tumor or acute injury, (i.e., B waves and A waves). The presence of unstable ICP (predominantly B waves) in NPH is well known, and the correlation with NPH shunt responsiveness ranges from 50 to 90%. Recently, analysis of the amplitudes of the ICP pulse pressure has been pro-posed as a predictive test in NPH.

If the CSF pressure is high, the patient should be investigated for other causes of obstructive hydrocephalus. If there is improvement of the patient after a 40 to 50-mL (high-volume) lumbar tap that the patient will likely respond well to shunting. An external ventricular drainage may be used in patients who fail to respond to a high-volume tap. Currently, there is no substantial evidence to support predictive-

Treatment includes conservative measures and surgery for patients with favorable risk benefit ratio. Temporizing measures include acetazolamide and high volume tap. As per practice guidelines, surgery is considered for patients

test has the risk of headache, lumbar radiculopathy, and risk of meningitis.

research is that patients have an increased resistance to outflow.

clinically suspected after a patient has failed to improve after the tap test.

*Normal Pressure Hydrocephalus DOI: http://dx.doi.org/10.5772/intechopen.92058*

*New Insight into Cerebrovascular Diseases - An Updated Comprehensive Review*

• Bicaudate ratio > 0.25

**10. Classification of INPH**

the diagnosis of NPH is unlikely [19].

**11. Prognostic tests**

• Enlargement of temporal horn

• Periventricular abnormal signals

• Flow void in aqueduct or fourth ventricle

**9. Supportive radiological investigations include**

• Cine MRI can show increased ventricular flow rate

which is not reversed with acetazolamide

• Radionuclide cisternogram may show delayed clearance.

can support the diagnosis of NPH and the need for further testing.

• SPECT-acetazolamide will demonstrate decreased periventricular perfusion

Distinguishing dilated ventricles due to cerebral atrophy from NPH is difficult [19–22]. Focal atrophy is often indicative of a degenerative dementia, particularly if it is asymmetric (e.g., frontotemporal dementia) or is stereotypical, such as hippocampal atrophy in Alzheimer dementia. In NPH, the Sylvain fissures are disproportionately widened in comparison to the cortical sulci, which are flattened ("high tight" convexity). The appearance of a pulsation artifact in the cerebral aqueduct, or measurements of CSF stroke volume or velocity in the aqueduct using phase – contrast methods cannot be used alone to recommend shunt surgery, but

Based on clinical and radiological features, INPH can be classified into probable, possible, and unlikely categories [19]. Probable criteria include age > 40, symptoms > 3 months, gait disorder, urinary incontinence or dementia, Evan's index > 0.3, temporal horn enlargement, aqueductal/Fourth ventricle flow void, and callosal angle > 40 [19]. If there is papilloedema, or absence of triad or no ventriculomegaly,

The tests which are done to ascertain the benefit of surgical intervention in INPH include: lumbar puncture which has a sensitivity of 26%, and specificity of 100%, extended lumbar drainage (sensitivity of 50–80% and specificity of 80%), measurement of CSF outflow resistance measurement (if >18 mm Hg/ml/min than 46% sensitive and 87% specific) and cine phase-contrast MRI (has insufficient

In this, 40-50 ml of CSF is removed, and pre- and post-tap with the Gait Scale (walking score + step score + time score) is assessed. The step score is based on the

**60**

evidence).

**12. Tap test**

number of steps required for the patient to walk 10 m. Similarly, pre- and post-tap cognitive function assessed Folstein Mini Mental State Exam and within 2–4 hours after the CSF tap post-tap assessments are conducted. A significant response to the tap test indicates responsiveness to shunt surgery [23]. However, lack of significant response does not exclude shunt responsiveness because the tap test is specific, rather than sensitive. External lumbar drainage can be considered if iNPH is still clinically suspected after a patient has failed to improve after the tap test.
