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How can you best diagnose idiopathic normal pressure hydrocephalus?
Diagnose idiopathic normal pressure hydrocephalus (INPH) by clinical history, brain imaging, physical findings, and physiological criteria.
The clinical examination must show the characteristic gait disturbance and either impaired cognition or impaired urinary continence (strength of recommendation [SOR]: B, based on systematic review of small randomized controlled trial [RCT] and prospective trials).
The cerebrospinal fluid (CSF) opening pressure should be between 70 and 245 mm H2o (SOR: B, based on systematic review of small RCT and prospective trials). No single test has sufficient sensitivity to rule out the diagnosis of INPH (SOR: B, based on systematic review of small RCT and prospective trials).
Subtle clues help make the diagnosis
Sumathi Devarajan, MD
Oregon Health and Science University Family Medicine, Portland
Normal pressure hydrocephalus is primarily diagnosed clinically. The classic triad of gait instability, cognitive dysfunction, and urinary incontinence, however, seldom present together. The only promising diagnostic and therapeutic intervention is the response observed with a ventriculoperitoneal shunt. However, this intervention is invasive and not without risks. Neuroimaging plays a role, but only when the clinical suspicion is high.
Therefore, understanding the subtleties in the character of the gait, the time of onset, the progression of dementia, and the onset of urinary incontinence in relationship to one another helps in making the final diagnosis.
Evidence summary
Current uncertainty in diagnostic criteria makes estimates of the incidence of INPH unclear, but it is thought to cause fewer than 5% of cases of dementia.1
Two systematic reviews have looked at the question of diagnosing INPH.2,3 Unfortunately, there is no definitive test or physical finding for INPH. For patients over 40 years of age, INPH has an insidious onset, a progressive course, and lacks an identifiable antecedent cause. A brain imaging study reveals ventricular enlargement not attributable to other causes. Some suggest that the diagnosis be assessed as “probable,” “possible,” and “unlikely” based on the degree of fulfillment of a set of historical, imaging, clinical, and physiological criteria (TABLE).3
TABLE
Categorizing the likelihood of idiopathic normal pressure hydrocephalus3
| Probable INPH |
| HISTORY (MUST FULFILL ALL) |
|
| BRAIN IMAGING (MUST FULFILL ALL) |
|
| CLINICAL |
|
| Gait/balance should reveal at least 2 of the following 9 items: |
|
| Tests of cognition should show evidence of at least 2 of the following 7 characteristics that are not fully attributable to other conditions: |
|
| Symptoms of urinary incontinence not attributable to other primary urological disorders should be present: |
|
| PHYSIOLOGICAL |
|
| Possible INPH |
| HISTORY (MUST FULFILL ALL) |
|
| BRAIN IMAGING (MUST FULFILL ALL) |
|
| CLINICAL |
|
| PHYSIOLOGICAL |
|
Which patients will benefit from shunting?
Supplemental prognostic tests have been developed to help decide which patients are most likely to benefit from a ventriculoperitoneal shunt. Complicating comparisons between the various tests is the lack of a standard set of measures of function in gait, cognition, and urination; nor is there agreement on how long after shunting the clinician should make these measurements.
A systematic review4 of the most commonly used prognostic tests identified a response to a large-volume (40–50 mL) CSF tap test as having a positive predictive value (PPV) between 73% and 100% but a negative predictive value (NPV) of only 23% to 42%. Thus, observing an improvement of function after such a test is a good predictor of improvement after shunting, but many patients who do not respond to the test respond to shunting.
A variation of the CSF tap test is the extended lumbar drainage test, which involves placing a lumbar intrathecal catheter and allowing the drainage of 10 mL of CSF/hour for 72 hours. The PPV for this test ranges from 80% to 100%, and NPV from 66% to 100%.
A third possible test is the measurement of resistance to an infusion of saline into the lumbar subarachnoid space (CSF Ro test). This test has multiple variations of technique. Reported values for PPV are 75% to 92%, and for NPV of 27% to 92%.
Other tests, such as radionuclide cisternography or magnetic resonance imaging CSF flow void, have predictive values too low or have too few studies to be recommended.4
Recommendations from others
A recently published expert consensus statement proposes that the diagnosis of INPH be made using the history, clinical examination, and neuroimaging.4 Cases of probable INPH can proceed directly to ventriculoperitoneal shunt, or supplemental testing can be used to improve the certainty of a positive shunt response. A positive CSF tap test should lead to shunting.
Follow up negative tap tests with the extended lumbar drainage test or the CSF Ro test (or both). A positive response to any of the tests should lead to shunting; negative responses to all the tests indicates a low chance (<10%) of responding to a ventriculoperitoneal shunt.4
1. Hebb AO, Cusimano MD. Idiopathic normal pressure hydrocephalus: A systematic review of diagnosis and outcome. Neurosurgery 2001;49:1166-1184.
2. Marmarou A, Bergsneider M, Klinge P, Relkin N, Black PM. The value of supplemental prognostic tests for the preoperative assessment of idiopathic normal-pressure hydrocephalus. Neurosurgery 2005;57(3 suppl):S17-S28.
3. Relkin N, Marmarou A, Klinge P, Bergsneider M, Black PM. Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery 2005;57(3 suppl):S4-S16;discussion ii-v.
4. Verrees M, Selman WR. Management of normal pressure hydrocephalus. Am Fam Physician 2004;70:1071-1078.
Diagnose idiopathic normal pressure hydrocephalus (INPH) by clinical history, brain imaging, physical findings, and physiological criteria.
The clinical examination must show the characteristic gait disturbance and either impaired cognition or impaired urinary continence (strength of recommendation [SOR]: B, based on systematic review of small randomized controlled trial [RCT] and prospective trials).
The cerebrospinal fluid (CSF) opening pressure should be between 70 and 245 mm H2o (SOR: B, based on systematic review of small RCT and prospective trials). No single test has sufficient sensitivity to rule out the diagnosis of INPH (SOR: B, based on systematic review of small RCT and prospective trials).
Subtle clues help make the diagnosis
Sumathi Devarajan, MD
Oregon Health and Science University Family Medicine, Portland
Normal pressure hydrocephalus is primarily diagnosed clinically. The classic triad of gait instability, cognitive dysfunction, and urinary incontinence, however, seldom present together. The only promising diagnostic and therapeutic intervention is the response observed with a ventriculoperitoneal shunt. However, this intervention is invasive and not without risks. Neuroimaging plays a role, but only when the clinical suspicion is high.
Therefore, understanding the subtleties in the character of the gait, the time of onset, the progression of dementia, and the onset of urinary incontinence in relationship to one another helps in making the final diagnosis.
Evidence summary
Current uncertainty in diagnostic criteria makes estimates of the incidence of INPH unclear, but it is thought to cause fewer than 5% of cases of dementia.1
Two systematic reviews have looked at the question of diagnosing INPH.2,3 Unfortunately, there is no definitive test or physical finding for INPH. For patients over 40 years of age, INPH has an insidious onset, a progressive course, and lacks an identifiable antecedent cause. A brain imaging study reveals ventricular enlargement not attributable to other causes. Some suggest that the diagnosis be assessed as “probable,” “possible,” and “unlikely” based on the degree of fulfillment of a set of historical, imaging, clinical, and physiological criteria (TABLE).3
TABLE
Categorizing the likelihood of idiopathic normal pressure hydrocephalus3
| Probable INPH |
| HISTORY (MUST FULFILL ALL) |
|
| BRAIN IMAGING (MUST FULFILL ALL) |
|
| CLINICAL |
|
| Gait/balance should reveal at least 2 of the following 9 items: |
|
| Tests of cognition should show evidence of at least 2 of the following 7 characteristics that are not fully attributable to other conditions: |
|
| Symptoms of urinary incontinence not attributable to other primary urological disorders should be present: |
|
| PHYSIOLOGICAL |
|
| Possible INPH |
| HISTORY (MUST FULFILL ALL) |
|
| BRAIN IMAGING (MUST FULFILL ALL) |
|
| CLINICAL |
|
| PHYSIOLOGICAL |
|
Which patients will benefit from shunting?
Supplemental prognostic tests have been developed to help decide which patients are most likely to benefit from a ventriculoperitoneal shunt. Complicating comparisons between the various tests is the lack of a standard set of measures of function in gait, cognition, and urination; nor is there agreement on how long after shunting the clinician should make these measurements.
A systematic review4 of the most commonly used prognostic tests identified a response to a large-volume (40–50 mL) CSF tap test as having a positive predictive value (PPV) between 73% and 100% but a negative predictive value (NPV) of only 23% to 42%. Thus, observing an improvement of function after such a test is a good predictor of improvement after shunting, but many patients who do not respond to the test respond to shunting.
A variation of the CSF tap test is the extended lumbar drainage test, which involves placing a lumbar intrathecal catheter and allowing the drainage of 10 mL of CSF/hour for 72 hours. The PPV for this test ranges from 80% to 100%, and NPV from 66% to 100%.
A third possible test is the measurement of resistance to an infusion of saline into the lumbar subarachnoid space (CSF Ro test). This test has multiple variations of technique. Reported values for PPV are 75% to 92%, and for NPV of 27% to 92%.
Other tests, such as radionuclide cisternography or magnetic resonance imaging CSF flow void, have predictive values too low or have too few studies to be recommended.4
Recommendations from others
A recently published expert consensus statement proposes that the diagnosis of INPH be made using the history, clinical examination, and neuroimaging.4 Cases of probable INPH can proceed directly to ventriculoperitoneal shunt, or supplemental testing can be used to improve the certainty of a positive shunt response. A positive CSF tap test should lead to shunting.
Follow up negative tap tests with the extended lumbar drainage test or the CSF Ro test (or both). A positive response to any of the tests should lead to shunting; negative responses to all the tests indicates a low chance (<10%) of responding to a ventriculoperitoneal shunt.4
Diagnose idiopathic normal pressure hydrocephalus (INPH) by clinical history, brain imaging, physical findings, and physiological criteria.
The clinical examination must show the characteristic gait disturbance and either impaired cognition or impaired urinary continence (strength of recommendation [SOR]: B, based on systematic review of small randomized controlled trial [RCT] and prospective trials).
The cerebrospinal fluid (CSF) opening pressure should be between 70 and 245 mm H2o (SOR: B, based on systematic review of small RCT and prospective trials). No single test has sufficient sensitivity to rule out the diagnosis of INPH (SOR: B, based on systematic review of small RCT and prospective trials).
Subtle clues help make the diagnosis
Sumathi Devarajan, MD
Oregon Health and Science University Family Medicine, Portland
Normal pressure hydrocephalus is primarily diagnosed clinically. The classic triad of gait instability, cognitive dysfunction, and urinary incontinence, however, seldom present together. The only promising diagnostic and therapeutic intervention is the response observed with a ventriculoperitoneal shunt. However, this intervention is invasive and not without risks. Neuroimaging plays a role, but only when the clinical suspicion is high.
Therefore, understanding the subtleties in the character of the gait, the time of onset, the progression of dementia, and the onset of urinary incontinence in relationship to one another helps in making the final diagnosis.
Evidence summary
Current uncertainty in diagnostic criteria makes estimates of the incidence of INPH unclear, but it is thought to cause fewer than 5% of cases of dementia.1
Two systematic reviews have looked at the question of diagnosing INPH.2,3 Unfortunately, there is no definitive test or physical finding for INPH. For patients over 40 years of age, INPH has an insidious onset, a progressive course, and lacks an identifiable antecedent cause. A brain imaging study reveals ventricular enlargement not attributable to other causes. Some suggest that the diagnosis be assessed as “probable,” “possible,” and “unlikely” based on the degree of fulfillment of a set of historical, imaging, clinical, and physiological criteria (TABLE).3
TABLE
Categorizing the likelihood of idiopathic normal pressure hydrocephalus3
| Probable INPH |
| HISTORY (MUST FULFILL ALL) |
|
| BRAIN IMAGING (MUST FULFILL ALL) |
|
| CLINICAL |
|
| Gait/balance should reveal at least 2 of the following 9 items: |
|
| Tests of cognition should show evidence of at least 2 of the following 7 characteristics that are not fully attributable to other conditions: |
|
| Symptoms of urinary incontinence not attributable to other primary urological disorders should be present: |
|
| PHYSIOLOGICAL |
|
| Possible INPH |
| HISTORY (MUST FULFILL ALL) |
|
| BRAIN IMAGING (MUST FULFILL ALL) |
|
| CLINICAL |
|
| PHYSIOLOGICAL |
|
Which patients will benefit from shunting?
Supplemental prognostic tests have been developed to help decide which patients are most likely to benefit from a ventriculoperitoneal shunt. Complicating comparisons between the various tests is the lack of a standard set of measures of function in gait, cognition, and urination; nor is there agreement on how long after shunting the clinician should make these measurements.
A systematic review4 of the most commonly used prognostic tests identified a response to a large-volume (40–50 mL) CSF tap test as having a positive predictive value (PPV) between 73% and 100% but a negative predictive value (NPV) of only 23% to 42%. Thus, observing an improvement of function after such a test is a good predictor of improvement after shunting, but many patients who do not respond to the test respond to shunting.
A variation of the CSF tap test is the extended lumbar drainage test, which involves placing a lumbar intrathecal catheter and allowing the drainage of 10 mL of CSF/hour for 72 hours. The PPV for this test ranges from 80% to 100%, and NPV from 66% to 100%.
A third possible test is the measurement of resistance to an infusion of saline into the lumbar subarachnoid space (CSF Ro test). This test has multiple variations of technique. Reported values for PPV are 75% to 92%, and for NPV of 27% to 92%.
Other tests, such as radionuclide cisternography or magnetic resonance imaging CSF flow void, have predictive values too low or have too few studies to be recommended.4
Recommendations from others
A recently published expert consensus statement proposes that the diagnosis of INPH be made using the history, clinical examination, and neuroimaging.4 Cases of probable INPH can proceed directly to ventriculoperitoneal shunt, or supplemental testing can be used to improve the certainty of a positive shunt response. A positive CSF tap test should lead to shunting.
Follow up negative tap tests with the extended lumbar drainage test or the CSF Ro test (or both). A positive response to any of the tests should lead to shunting; negative responses to all the tests indicates a low chance (<10%) of responding to a ventriculoperitoneal shunt.4
1. Hebb AO, Cusimano MD. Idiopathic normal pressure hydrocephalus: A systematic review of diagnosis and outcome. Neurosurgery 2001;49:1166-1184.
2. Marmarou A, Bergsneider M, Klinge P, Relkin N, Black PM. The value of supplemental prognostic tests for the preoperative assessment of idiopathic normal-pressure hydrocephalus. Neurosurgery 2005;57(3 suppl):S17-S28.
3. Relkin N, Marmarou A, Klinge P, Bergsneider M, Black PM. Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery 2005;57(3 suppl):S4-S16;discussion ii-v.
4. Verrees M, Selman WR. Management of normal pressure hydrocephalus. Am Fam Physician 2004;70:1071-1078.
1. Hebb AO, Cusimano MD. Idiopathic normal pressure hydrocephalus: A systematic review of diagnosis and outcome. Neurosurgery 2001;49:1166-1184.
2. Marmarou A, Bergsneider M, Klinge P, Relkin N, Black PM. The value of supplemental prognostic tests for the preoperative assessment of idiopathic normal-pressure hydrocephalus. Neurosurgery 2005;57(3 suppl):S17-S28.
3. Relkin N, Marmarou A, Klinge P, Bergsneider M, Black PM. Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery 2005;57(3 suppl):S4-S16;discussion ii-v.
4. Verrees M, Selman WR. Management of normal pressure hydrocephalus. Am Fam Physician 2004;70:1071-1078.
Evidence-based answers from the Family Physicians Inquiries Network