This document provides information on the surgical management of normal pressure hydrocephalus (NPH). It discusses the history and examination findings suggestive of NPH, describes imaging techniques used for diagnosis, and outlines special tests that can aid in evaluation. It also reviews the options for surgical treatment, including ventriculoperitoneal, lumboperitoneal, and endoscopic third ventriculostomy procedures. Factors influencing shunt responsiveness are summarized, and guidelines for proceeding to shunt placement based on diagnostic classification are presented.

1. Surgical management
of NPH
Shashank A

2. Management
• History
• Examination
• Imaging
• Special tests
• Surgical treatment

3. History
• SUGGESTIVE OF NPH
• Insidious onset (versus acute)
• Origin after age 40 yr
• A minimum duration of at least 3 to 6 mo
• No evidence of an antecedent event such as head trauma,
intracerebral hemorrhage, meningitis, or other known causes of
secondary hydrocephalus
• Progression over time
• No other neurological, psychiatric, or general medical conditions that
are sufficient to explain the presenting symptoms

4. Examination
• Gait/balance
• At least two of the following should be present and not be entirely attributable to other
condition
• Decreased step height
• Decreased step length
• Decreased cadence (speed of walking)
• Increased trunk sway during walking
• Widened standing base
• Toes turned outward on walking
• Retropulsion (spontaneous or provoked)
• En bloc turning (turning requiring three or more steps for 180 degrees)
• Impaired walking balance, as evidenced by two or more corrections out of eight steps on
tandem gait testing

5. Gait in NPH
• “Apractic,” “bradykinetic,” “glue-footed,” “magnetic,” “parkinsonian,”
“short-stepped” and “shuffling.”
• Gait problems may emerge as difficulty in ascending or descending stairs.
• Patients may complain of difficulty rising from a chair, “give-way”
weakness of the lower extremities, and fatigue brought on by walking.
• As the disease progresses, turning in place becomes tenuous and
typically requires multiple steps (en bloc).
• The stance in INPH may be more forward leaning than in healthy normal
individuals
• INPH patients tend to show a wider sway and imbalance that may be
accentuated by eye closure

6. Cognition
• Documented impairment in two of following
• Psychomotor slowing (increased response latency)
• Decreased fine motor speed
• Decreased fine motor accuracy
• Difficulty dividing or maintaining attention
• Impaired recall, especially for recent events
• Executive dysfunction, such as impairment in multistep procedures,
working memory, formulation of abstractions/similarities, insight.
• Behavioral or personality changes

7. Urinary continence
• ONE of the following
• Episodic or persistent urinary incontinence not attributable to primary
urological disorders
• Persistent urinary incontinence
• Urinary and fecal incontinence
• TWO of the following
• Urinary urgency as defined by frequent perception of a pressing need to
void
• Urinary frequency as defined by more than six voiding episodes in an
average 12-hour period despite normal fluid intake
• Nocturia as defined by the need to urinate more than two times in an
average night

8. Not seen in NPH
• Papilledema
• Seizure
• Headache

10. Imaging
• Ventricular enlargement
not entirely attributable
to cerebral atrophy or
congenital enlargement
• Evan’s index > 0.3
• No macroscopic CSF
obstruction

11. • Axial MRI
• Dilatation of sulci

12. • Enlargement of the temporal horns of the lateral
ventricles not entirely attributable to hippocampus
atrophy

13. • Evidence of altered brain water content, including periventricular
signal changes on CT and MRI not attributable to microvascular
ischemic changes or demyelination
• White matter changes in the frontal lobe and periventricular region
have the strongest relation to impairments in balance and gait

14. Sagittal MRI
• Measurement of the diameter of the corpus callosum
• Decreases in many cases of INPH as the dorsal
surface of the ventricle domes upward
• Cingulate sulcus sign: Wide or normal cingulate
sulcus in the frontal lobe but compressed at the
posterior part.
• Loss of convexity of upper midbrain
• Aqueductal flow void

15. Not NPH NPH

16. • An aqueductal or fourth ventricular flow void on MRI
• Fast movement of CSF gives rise to a signal loss on T2-
weighted MRI called the flow void phenomenon
• The flow void is often increased in the cerebral aqueduct and
forth ventricle in NPH.

17. • Coronal MRI
• Calculation of the callosal angle
• Assessment of the perihippocampal morphology
• Useful in distinguishing ventriculomegaly
secondary to cerebral atrophy

18. • Callosal angle of 40 degrees or more

19. • Dilated sylvian fissure

20. DESH:Disproportionately Enlarged
Subarachnoid Space Hydrocephalus
Circles: fronto-parietal convexity sulcal effacement and sagittal sinus abutment
Arrows: Enlargement and upward displacement of roof of Sylvian fissure
Not NPH NPH

24. Other radiological tests
• Radionuclide cisternogram showing delayed
clearance of radiotracer over the cerebral
convexities after 48–72 h.
• Cine MRI study or other technique showing
increased ventricular flow rate
• SPECT-acetazolamide challenge showing
decreased periventricular perfusion that is not
altered by acetazolamide

25. Special tests

26. Lumbar puncture
• A cerebrospinal fluid (CSF) opening pressure (CSF-OP) as diagnostic purpose
• Measured by lumbar puncture in the lateral recumbent position
• Range of 5–18 mm Hg
• Pressure > 18 mm Hg implies other causes of HCP
• Up to 50 cc of CSF is removed to see if symptoms are temporarily relieved by this
CSF volume reduction.
• If removal of some CSF dramatically improves symptoms, even temporarily, then
surgical treatment is likely to be successful.
• Limitation of lumbar puncture
• Some people may have little or no improvement after the test, and yet may still
improve with a shunt.
• When the response to a lumbar puncture is “negative” or uncertain, further
evaluation may be helpful

27. External lumbar drainage or
continuous lumbar drainage
• It also allows for more accurate recording of CSF pressure and response
• 300 ml to be removed over a 5-day period.
• ELD was initially described by Haan and Thomeer et al and consisted of draining 10
ml of CSF per hour for a period of 72 hours (total, 720 ml).
• Prospective study of ELD reported by Walchenbach et al.
• 49 patients from three hospitals (43 with INPH) were studied. Patients who did
not improve with a tap were given ELD in which 300 ml was removed over a 5-
day period.
• Of 38 patients given ELD, 16 improved after drainage and 22 did not. Of the 16
who were improved after drainage, 14 improved after shunting.
• The overall accuracy of ELD in this study equaled 62%.
Haan J, Thomeer RT: Predictive value of temporary external lumbar drain- age in normal pressure hydrocephalus. Neurosurgery 22:388–391, 1988.
RT, Vanneste J: The value of temporary external lumbar CSF drainage in predicting the outcome of shunting on normal pressure hydrocephalus. J Neurol

28. CSF flow resistance
• The measurement of CSF outflow resistance is a more
involved test that requires a specialized clinical setting.
• The resistance to CSF is considered to be the impedance to flow
offered by the CSF absorption pathways.
• This test begins with a lumbar tap and assesses the degree of
blockage of CSF absorption back into the bloodstream.
• It requires the simultaneous infusion of artificial spinal fluid and
measurement of CSF pressure.
• If the calculated resistance value is abnormally high, then there is a
very good chance that the patient will improve with shunt surgery,
since the shunt mimics the function of the body’s normal CSF
drainage pathways.

29. Method of CSF resistance
study
• ICP measurements used for the calculation of Ro are obtained from a cranial epidural monitor.
• Katzman test
• Pump introduces mock CSF fluid or saline at a known rate through a needle placed in the lumbar
subarachnoid space.
• The Ro, as defined by the Katzman infusion test, is the difference in the final steady-state pressure
reached and the initial pressure divided by the infused flow rate.
• R0 = Pf - Pi/I
• Trakeuchi et al.measureed Ro in 25 shunted INPH patients.
• The average Ro for the shunted group with improved outcome equaled 35.3 mm Hg/ml/min.
• The average value of Ro for the shunted group with no improvement equaled 9.1 mm Hg/ml/min (P <
0.01).
• On the basis of this threshold, the calculated sensitivity and specificity equaled 100 and 92%,
respectively
Takeuchi T, Kasahara E, Iwasaki M, Mima T, Mori K: Indications for shunting in patients with idiopathic normal pressure hydrocephalus presenting with
dementia and brain atrophy (atypical idiopathic normal pressure hydrocephalus). Neurol Med Chir (Tokyo) 40:38–47, 2000.

30. CSF flow study
• It has been proposed that NPH patients have a higher CSF flow velocity through
the cerebral aqueduct.
• This was first noted by an exaggerated aqueductal flow void on axial MRI scans
• Subsequently, methodologies were developed to estimate the actual maximum
flow velocity at that site
• Luetmer et al. suggested that velocities greater than 18 ml/min were predictive for
good outcome after shunting.
• The pathophysiological basis of increased CSF flow void velocity in INPH has not
been established.
• On the basis of current evidence, neither MRI CSF flow void sign nor quantitative
CSF flow velocity seems to have significant diagnostic value.
Luetmer PH, Huston J, Friedman JA, Dixon GR, Petersen RC, Jack CR, McClelland RL, Ebersold MJ: Measurement of cerebrospinal fluid flow at the cerebral aqueduct
by use of phase contrast magnetic resonance imaging: Technique validation and utility in diagnosing idiopathic normal pressure hydrocephalus. Neurosurgery
50:534–544, 2002.

31. ICP monitoring
• In addition to measuring the baseline opening pressure, many have
been interested in possible relationships between continuous ICP
recording variables and outcome for NPH.
• Studies have been done for correlation between the number of B
waves recorded (overnight during sleep) and outcome
• It has been proposed that the increased frequency in B waves is
indicative of lowered compliance and/or may play an important role
in the pathophysiology of the ventriculomegaly and neuronal
dysfunction.
• Class III evidence does not currently support continuous ICP
monitoring to determine the frequency of B or A waves.
• ICP to be measured only when opening pressure on LP is equivocal.

32. MR cisternogram
• Persistance of contrast beyond 48 hrs predict good
outcome

33. Shunt responsiveness
• Considered separately as a measure of treatment outcome and does not enter into
diagnostic classification
• On the basis of clinical presentation alone, evidence shows that favorable response to
shunting will vary from 46 to 63%
• INDICATORS of SHUNT responsiveness
• The onset of gait disturbance as the first and most prominent symptom
• A known cause for NPH, such as trauma or hemorrhage
• The scan (MRI or CT) shows the ventricular size to be disproportionately
• Larger than the CSF in the subarachnoid space
• Removal of spinal fluid via lumbar puncture or lumbar catheter gives dramatic,
temporary relief of symptoms
• ICP or spinal fluid pressure monitoring shows an abnormal range or pattern of spinal
fluid pressure or an elevated CSF outflow resistance
• Minimal evidence of disease of the small blood vessels nourishing the brain

34. GUIDENILE FOR PROCEEDING TO
SHUNT
• On the basis of the history, neurological examination, and basic neuroimaging (CT and/or MRI
scans), the patient is categorized as
• Probable
• Possible
• Unlikely INPH
• Shunt placement for probable and possible INPH with good outcome ranges from 43 - 60 %
• The probability of improvement for an unlikely INPH designation is presumably less
• To avoid complications and improve the certainty of a positive shunt response beyond 50 to 61%,
all probable and possible INPH patients should be considered for supplemental testing.
• One or more of the following three tests is recommended:
• CSF tap test
• Ro determination,
• ELD.

36. Shunt
• Options
• Ventriculoperitoneal shunt
• Lumboperitoneal shunt
• ETV

37. Recepient sites
• Peritoneum
• Provides little pressure of its own and allows drainage and reabsorption of a large volume of fluid.
• Cardiac atrium
• Provides an egress for a very large volume of CSF.
• It can also handle high protein content that could cause malabsorption of fluid in the peritoneal space.
• Pleural space
• Generates its own negative pressure.
• This can be used to advantage in constructing a shunting system that provides less-than-normal
pressure or even negative pressure if the valve is chosen appropriately.2
• Antisiphoning components, which prevent negative pressure in the shunt tubing, can be used to
counteract the negative pressure “sink” of the pleural space.
• Gallbladder
• Provides a positive pressure postprandially that prevents over drainage
• Torkildsen shunt (ventricle to the cisternal space)
• Sinushunt (ventricle to the venous sinus).

38. Parts of shunt
• Inlet tubing (ventricular drain),
which is a thin short tube with an
inner diameter of 0.9 to 1.2 mm
• Valve
• Distal drain, a longish silicone
rubber tube
• Acssesories
• Reservoirs, Siphon Devices
• Connectors, Filters, Pumping
Chamber

39. • Silicon membrane—flow is controlled by an elastic membrane that
changes the area of the outlet orifice.
• A simpler, less accurate mechanism consists of a valve mechanism
derived from two apposing semirigid membranes.
• These valves, which include the Medtronic, Pudenz, and Codman distal
slit valves, are manufactured and then individually tested to determine
the approximate opening pressure.
• They are then segregated into different bins covering a range of
pressures.
• Valves - Classified according to their construction

40. • Ball-on-spring—flow depends on compression of a spring(flat
or helical) supporting a ball moving along the cone that
constitutes the outlet orifice.
• It consists of a tiny ball situated on a ring, with a spring
pushing the ball downward on the ring. CSF passes through
the ring, elevating the ball if the pressure exceeds the
pressure exerted by the spring.
• This creates a one-way flow mechanism because reverse flow
will not occur as the ball sits down onto the ring.
• In ball-on-spring valves, this pressure is very stable over time
but is sensitive to dynamic changes in ICP.
• Medtronic Strata valve, the Codman Hakim programmable
and Precision valves, and the Aesculap proGAV valve
• A Proximal or distal slit valves—flow depends on the area of a
slit in soft silicone rubber.

42. Programmable shunt in NPH
• Adults are less able to adapt to a fixed pressure than children, whose brains are
more plastic.
• Opening and closing pressure may be programmed externally
• Strata valve (Medtronic) with a fused antisiphoning chamber
• Codman-Hakim valve, Codman/Johnson & Johnson, NON SIPHONING
• Sophy valve, Sophysa NON SIPHONING
• 3 to 20 cm H2
O by various increments.

43. Shunt insertion
• Ventriculoperitoneal shunt - Frontal or occipital burr hole
• Ventriculo pleural shunt
• Incision at the third or fourth rib off the midline in the same line that we would use for
passage of the peritoneal catheter for a ventriculoperitoneal shunt.
• Then dissect down to the pleura through the muscles of the anterior chest wall and the
intercostal muscles.
• Once the pleura is identified, it is not opened until the shunt is entirely connected.
• Connect the ventricular catheter to the shunting device, visualize distal runoff of CSF,
and then under direct vision make a pleural egress with a long hemostat and place
approximately 20 cm of tubing into the pleural space.
• Placement of a positive end–expiratory pressure valve in the anesthesia circuit to
maintain lung inflation during placement of the pleural catheter and thus avoid
pneumothorax.

44. Ventriculoatrial shunt placement
• Fluoroscopic or angiographic assistance
• Tunnel is made to a point over the internal jugular vein.
• This point is selected by placement of a “finding” needle and then a larger
needle and J wire into the internal jugular vein on the neck lateral to the
sternocleidomastoid muscle.
• Tubing is tunneled to the neck incision to allow the blunt-end catheter tubing
into the cardiac atrium with an additional several centimeters for positioning.
• Once the wire is visualized in the cardiac atrium by fluoroscopy, a 10-Fr
introducer sheath is placed over the wire, the wire is removed, and the tubing
is threaded directly through the introducer sheath into the cardiac atrium
under fluoroscopic guidance.
• Intraoperative cardiac angiography to confirm the placement of the catheter at
the junction between the superior vena cava and the right atrium.

45. Siphoning
• Change in pressure when the patient suddenly stands from
lying posture in siphoning
• ANTI SIPHON DEVICES (ASDs)
• In general, the device is based on a membrane that is
mechanically coupled to the subcutaneous tissue overlying
it.
• When the intraluminal pressure becomes significantly
negative (relative to atmospheric pressure), the membrane
is drawn inward—interacting with other fixed components of
the ASD

46. • Membrane devices (Delta chamber)
• Subcutaneous membrane is designed to
stop drainage when its outlet pressure is
negative
• Could also impede CSF flow when
compressed by tense skin or external
pressure through the skin.
• Flow-regulating (Siphon Guard) device
• Hakim programmable valve
• Limits excessive flow but may
permanently increase the hydrodynamic
resistance of the shunt system to very
high values
• May cause intracranial hypertension

47. Complications
• Shunt Malfunction
• In growth of choroid plexus or other debris into the catheter
• Shunt Infection
• Overdrainage
• Low-pressure headaches
• Small or slit ventricles -
• Subdural collections
• Chronic hematomas
• CSF overdrainage

48. Underdrainage
• Patient presents with recurrence of symptoms
• Removing an antisiphoning component or by replacing a
differential pressure valve with a flow-regulated valve may
sometimes provide additional drainage.
• Revising the terminus of the shunting device from the
peritoneal space to the pleural space, which generates
negative pressure, can improve drainage characteristics
• Ventriculoatrial shunts provide more drainage than
ventriculoperitoneal shunts do, and therefore shunt
revision to a ventriculoatrial shunt can be done.

49. • Subdural heamtoma
• Ventricular collapse and disruption of the subdural
bridging veins, causing subdural hematoma.
• Other complications
• Infection
• Bleeding - Incidence of intracerebral hematoma= 3%
• CSF leakage
• Seizures

50. Post shunt pressure setting
• Theoretical benefit with placing a
shunt with a high differential
pressure and then slowly decreasing
that pressure to a more normal or
even less-than-normal one.
• This may allow better
accommodation and prevent
ventricular collapse from sudden
over drainage
• But some studies have used fixed
pressure setting at 100 mm of h2O
and then then reducing pressure

51. J Neurosurg 124:359–367, 2016

52. ETV
• Some patients with NPH have a late-onset form of
relative aqueduct stenosis.
• These patients, there is a mismatch between the
degree of ventriculomegaly in the lateral ventricles
and third ventricle and between the aqueduct of
Sylvius and the fourth ventricle.
• Gangemi and coauthors reported improvement in
72% of NPH patients with this technique and a
relatively low complication rate

54. Lumboperitoneal shunt
• Lumboperitoneal (LP) shunt has been used occasionally
• The main reason LP shunt is considered when treating
patients with NPH is the avoidance of the risk of
intracranial hemorrhage while passing a catheter
through the brain parenchyma.
• Higher failure rates compared to ventriculoperitoneal
shunts
• SINPHONI 2 trial of Japan

56. • Published rates of improvement after surgical intervention range from 53% to
78.9%
• 31% of patients who are shunt non responders, have potential overlap with
other neurodegenerative conditions, including Parkinson’s and Alzheimer’s
disease.
• In a study by Pojari et al
• Gait showed the highest improvement over baseline (83% at 3 years and
87% at the last analysed follow-up of 7 years)
• Cognition showed intermediary improvement (84% and 86%, respectively)
• Urinary incontinence showed the least improvement (84% and 80%,
respectively)
jari S, Kharkar S, Metellus P, Shuck J, Williams MA, Rigamonti D. Normal pressure hydrocephalus: long-term outcome after shunt surgery. J Neurol Neurosurg Psychiatry. 2008 Nov;79(11):1282
Outcome

57. • Comorbid AD and iNPH is common
• Increased with the presence of hypertension and
advancing age.
• AD pathology is present in cortical biopsy of 75% of those iNPH
patients with significant dementia at the time of shunt surgery
• Gait can improve with shunting, dementia typically does not.
• Surgical treatment is generally discouraged for patients with
severe dementia, even in the setting of gait dysfunction and
incontinence, regardless of radiographic findings
• Gait is the easiest symptom to assess objectively
• 10m walking test- in which the number of steps taken and the
time necessary to traverse this distance is used to compare
preoperative and postoperative status.
Miller DC, et al. Alzheimer’s disease comorbidity in normal pressure hydrocephalus: prevalence and shunt response. J Neurol Neurosurg Psychiatry 2000

58. Thank you