Normal pressure hydrocephalus assessments

Questionnaire/assessment: (from the Neurologist)
http://neuropsychminutiae.blogspot.com/2010/07/nph-questionnaires-for-initial.html

Guidelines for the Initial Management of NPH (published in Neurosurgery)  2005; 57:3.

Links, support groups, information, etc.
http://www.ninds.nih.gov/disorders/normal_pressure_hydrocephalus/normal_pressure_hydrocephalus.htm


Well done powerpoint presentation
http://www.usafp.org/USAFP-Lectures/2007-Lectures/16%20March%20-%20Friday/Ryan%20-%20NPHredo.ppt

MRI criteria:

1. Maximal frontal horn width divided by diameter of inner table, usually >.33, but often > .4
2. Lack cortical/hippocampal atrophy/extensive white matter lesions
3. Callosal angle > 40 degrees
4. Altered brain water content
5. Aqueductal and fourth ventricular flow void on MRI

Gait criteria:  At least two of the following

1. Gait/Balance- at least two of following present
2. Decreased step height
3. Decreased step length
4. Decreased cadence/speed
5. Decreased trunk sway
6. Widened stance
7. Toes turned outward while walking
8. En bloc turning- turns take three or more steps
9. Impaired balance- two or more corrective steps for eight steps on tandem gait testing

Cognition (at least two of following)

1. Cognition- two of following present
2. Psychomotor slowing
3. Decreased fine motor speed
4. Decreased fine motor accuracy
5. Difficulty dividing or maintaining attention
6. Impaired recall especially for recent events
7. Impairment of executive functions- multi-step procedures, working memory, formulation of abstractions, insight
8. Behavioral or personality changes

Urinary symptoms: one of following

 

1. Episodic urinary incontinence not attributable to other causes
2. Persistent urinary incontinence
3. Fecal and urinary incontinence

OR  One of following

1. Urinary urgency
2. Urinary frequency- 6 or more voids in 12 hour period
3. Nocturia- more than two voids in night

 Clinical diagnosis

Probable iNPH:  Gait or balance impairment, plus cognitive or bladder control disturbance, or both.  MRI shows an Evans ratio of greater than .3 with no evidence of obstruction.  Diagnosis based on probable NPH predictes 48-64 % of time a good response to surgery.

 

Possible iNPHL  Urinary or cognitive impairment without gait impairment

 

Pearls:

1. Rely on family assessment as much as what patient says about gait assessment
2. Levodopa trial occassionally needed to sort out festination
3. TInetti Assessment Scale (TAT) for gait assessment screening has a B level of evidence from AAN reviews  and is found here:  http://agrc.ucsf.edu/files/Tinetti%20AssessmentTool%20(gait%20and%20balance%20test)%20(Week%202%20-Mobility).pdf
4. TAT misses a velocity component for gait assessment so also use TUG (timed get up and go) and is found here http://www.dhmc.org/dhmc-internet-upload/file_collection/tug_0109.pdf that also has a Level B evidence from AAN
5. Other instruments that can be used are the ten minute walk, Berg balance test  http://www.fallpreventiontaskforce.org/pdf/BergBalanceScale.pdf  and the Short Physical Performance Battery   http://www.grc.nia.nih.gov/branches/ledb/sppb/index.htm
6. Urinary incontinence may be described as urinating just before reaching the toilet
7. Cognitive differentiation from Alzheimer's disease can be accomplished by testing that includes factors that innclude components that should not be affected by NPH, such as Boston Naming Test (in addition to findings that would be affected such as letter fluency and memory and executive function)
8. Atypical presentations in young may include headache, and poor job performance rather than memory loss.
9. Obstruction of aqueduct or fourth ventricle due to "late onset aqueductal stenosis" may improve with endoscopic third ventriculostomy (ETV).  These patients should NOT undergo LP due to risk of herniation
10. Thinned /  distended callosum may predict shunt responsiveness, may be seen as "bowing" on sagittal views
11. Presence of "B" waves and increased pulse amplitudes correlate with symptomatic iNPH and responsiveness to shunting.  Authors use 48 hours of monitoring followed by 72 hours of drainage.
12. Behaviorally and by fMRI, increased Stroop testing and finger tapping correlates with SMA functional activity
13. Response to serial LP's correlates with 88 % response to surgery.  Can measure with Tinetti and TUG tests (links above) .  With high volume tap, expect improvement in velocity, turning, stride length, number of steps to turn, and tendency to fall, among others.  Test immediately before and after shunt, and again q 2-4 hours.  Consecutive day LP's x 3 days increased sensitivity to 88 %. 
14. ELD (extended lumbar drainage x 3 days) if no response, very few patients will benefit from surgery.
15. With ELF and physiologic measurements, authors claim 75-90 % improvement in first year after shunting, and 80 % sustained improvement after two years, with substantial overall Medicare expenditure savings. 
16. If a programmable shunt is used, the billing code is 62252
17. Obviously need a good neurologist to make the diagnosis and exclude various neurodegenerative diseases