Frank Vrionis, MD, MPH, PhD

MNI Institute Director

Department of Neurosurgery

Jonathan Harris, MD

Department of Neurology

CSF

Rate of production constant 0.35ml/min, dependent on ICP

80% ventricles, 20% parenchyma

Total volume of CSF 150ml, 3 fold turnover daily

Absorption through arachnoid granulations (cell clusters then project into the sinuses)

Accessory CSF pathways

CSF

Steady state: Production = Absorption

NPH early phase lack of absorption of

CSF resistance to outflow ICP,

ventricular enlargement in ICP

(Pascal’s law, P=F/S)

You can have NPH with normal or high

ICP and with normal or large ventricles

NPH

Hakim triad only seen in 50% of patients

NPH can coexist with many other

disorders including PD (10%), AD (10-

20%), SLE, G-B-D

No test pathognomonic

Best LD

Current Protocol

Patient with suspected NPH

CT or MRI

LP or LD with cognitive/gait assessment before and after

Shunt placement using image guidance for accuracy and post-intraop CT to verify

Measure OP during surgery and select valve that is close to that

Shunts

Invented by John Holter, an engineer, for his son who had HC due to spina bifida (1949)

They all have a one way valve, a reservoir, and silicone tubing

Valves open when the gradient between inflow/outflow exceeds its opening pressure

Anti-siphon valves are additional valves that prevent over drainage when the patient is in upright position

Intracranial Pressure (ICP)

Hydrostatic

Pressure

(HP)

Intra-abdominal

Pressure (IAP)

Drake & Sainte-Rose, The Shunt Book, 1995

Opening

Pressure of

Valve

(OPV)

Hydrodynamics Several different pressures interact to determine CSF flow. A shunt

introduces an additional one (OPV).

Proximal Distal

… Opening the Valve to Drain CSF

How Does It Work?

7 discrete settings + Virtual Off

o 25 mmH2O Lowest

o 215 mmH2O Highest

Virtual Off (min 400mmH2O)

MRI Resistant to 3 Tesla

Position Independent

Available with SIPHONGUARD® Anti-Siphon Device

9

Shunts

SIPHONGUARD : Dual

Pathways

The primary pathway remains open at physiological flow rates (less than 40 ml/hr)

The primary pathway closes at a flow rate of about 100 ml/hr and CSF then flows through (and only through) the secondary pathway, at 10% of the original flow rate

The secondary pathway never closes

Complications/Results

70% of patients improve after shunting

(gait most important)

Early NPH responds better (early dx

before atrophy to periventricular WM)

No correlation between reduction of

ventriculomegaly and improvement of

Sxs

Why Don’t We Have 100%

Improvement

Recall bias

Arrest of progression

Early vs late NPH

Technical factors (there is no perfect

valve!)

Shunt Problems

We are steering a safe course between

Scylla of underdrainage and the

Charybdis of over drainage

Underdrainage: same symptoms

Over drainage: HA (postural), nausea,

dizziness, subdurals

Shunts

Over drainage reduced now with

adjustable valves

Underdrainage common with antisiphon

valves (increased resistance)

Problem solving

No improvement

Partial improvement

Great improvement but subdural hygroma

Complications

Revisions 11%

Infection 6%

Subdural hematomas or

hygromas

Invisishunt

Valve/reservoir is buried in the skull

Reduced profile and tension in closure

Shunts

Shunts

Shunts

Endoscopic 3rd Ventriculostomy

No foreign body implanted

Mainly for patients with obstructive HC

(cyst, tumor, aqueductal stenosis)

Yet to be established as a treatment for

NPH

Advantages of endoscope

Ability to visualize in deep and narrow area

Visulization is independent of path

Minimal invasiveness – can be used

through the natural orifice or a small

opening.

Disadvantages of endoscope

2D image compromising 3D perception

One hand is required to hold the

endoscope, although this disadvantage

can be eliminated by use of holders

In water media or air media even small

amount of blood compromises the

visualization

Endoscopic third ventriculosomy

ETV.mpg

Orbeye

Future Directions

NPH center of Excellence with FAU

Quest for an ideal physiologic valve that drains a set amount of CSF per hour irrespective of position

Create a mathematical model FEA of the brain

Examine all failed explanted valves in vitro and assess flow/pressure curves and reason for malfunction

Study arachnoid villi in NPH patients

Supported by a grant from the Sterling Foundation (FDV)

Self-regulating CSF Shunt Device

Asghar-Lab: Micro and Nanotechnology in

Medicine

Dr. Waseem Asghar, PhD

FAU Engineering Collaboration

FAU Memory Center