This document provides an overview of cerebrospinal fluid (CSF) anatomy and physiology, as well as disorders of CSF circulation. Key points include: CSF is formed in the choroid plexus and circulates through the ventricles before being absorbed into venous sinuses; intracranial pressure is regulated by CSF production, circulation and absorption; hydrocephalus is an excess accumulation of CSF within the brain that can be communicating or non-communicating; management involves medical treatment, temporary procedures like external ventricular drainage, and surgical options like shunts or endoscopic third ventriculostomy.

1. Dr. Zubair Sarkar
SR (Neurology), SGPGIMS
8th February 2019

2. List of contents
 CSF : Anatomy and Physiology
 Formation
 Circulation
 Absorption
 Intracerebral pressure (ICP)
 Cerebral perfusion pressure
 Consequences of altered CSF
hydrodynamics
 Disorders
 Classification
 Hydrocephalus
 Normal pressure hydrocephalus
 Hydrocephalus ex vacuo
 Benign external hydrocephalus
 Arrested hydrocephalus
 Intracranial hypotension
 Idiopathic Intracranial hypertension

3. CSF : Anatomy and Physiology

4. CSF Formation
 Average intracranial volume : 1400 to 1700 ml
 CSF occupies about 150 ml : 10 percent approx.
 Rate of formation : 0.35ml/min = ~20ml/hour = ~500ml/day
 Renewed 3 – 4 times a day

5. Sites of production
 Choroidal plexus : 70-80 percent
 Extra-choroidal : 20-30 percent
Ependyma
Capillaries
Brain Interstitial fluid

6. AQP1
Mechanism of choroidal production
Tight junction
 Epithelial cells
 Active process :
Uses ATP
 movement of ions
 osmotic
gradient 
secretion of H2O
 high expression of
AQP1 on apical
membrane

7. Factors affecting CSF production
Endogenous Exogenous
CSF Pressure Acetazolamide
Choroid plexus ischemia Frusemide
Hypoxia Amiloride
Acidosis/ Alkalosis Omeprazole
Hypoglycemia Glycosides
Neural Cholera toxins
Johnston, I et al. Child's Nerv Syst. 2000

8. Pathway of CSF Flow
Lateral ventricles
Foramen of Monro  Third ventricle
Aqueduct of Sylvius
Fourth ventricle
Foramina of Magendie and Luschka
Subarachnoid space of brain & spinal
cord
Reabsorption into venous sinus

9. Subarachnoid cisterns

10. Interpeduncular cistern
Ambient cistern
Quadrigeminal cistern
Sylvian cistern
Chiasmatic/
suprasellar cistern
Crural cistern

11. Mechanism of CSF flow
 The pressure gradient is highest in the lateral ventricles and diminishes
successively along the subarachnoid space
b, the negative venous pressure
(dark blue) produced during
inspiration causes temporary
pressure decrease in intracranial
compartment, resulting in CSF
outflow (Dreha-Kulaczewski et al.
2017)
Delaidelli, A et al. Journal of Neuroscience 2017
a. Arterial pulse wave (red) causes
temporary pressure increase in
intracranial compartment, resulting
in CSF outflow (O'Connell, 1943)

12. Absorption
 Arachnoid villi
 microscopic one-way valves
(modified pia and arachnoid)
 penetrate meningeal dural
layer lining venous sinuses
 Clumps of arachnoid villi =
arachnoid granulations =
macroscopic

13. Mechanism of absorption
 Hydrostatic pressure in
subarachnoid space (11 mmHg)
> dural sinuses (5 mmHg)
 Arachnoid villi open : pressure
in SAS ~1.5 mm Hg > pressure
in dural sinuses
 Passive process
Papaiconomou,C.et al News Physiol Sci 2002

14. Possible alternative sites of CSF absorption
 Arachnoid endothelium &
membrane
 Adventitia of blood vessels
and lymphatics
 Cranial/ spinal nerve roots
sleeves/ lymphatics
 Capillary endothelium
 Spinal arachnoid
projections
Johnston, I et al. Child's Nerv Syst. 2000
Papaiconomou,C.et al News Physiol Sci 2002

15. The functions of the CSF
 Support: wt. of brain ~1500 gm  ~50 gm
 Shock absorber : protects brain during head trauma
 Homeostasis
 Maintains stable intrinsic CNS temperature
 Maintains osmotic pressure  normal CSF pressure  normal cerebral
perfusion
 Removes biochemical waste products
 Nutrition : glucose/proteins/lipids/electrolytes  essential CNS nutrition
 Immune function : contains immunoglobulins and mononuclear cells

16. Intra Cranial Pressure (ICP)
 ≤ 15 mmHg in adults
 Intracranial hypertension (ICH) : pressure ≥ 20 mmHg
 Normally lower in children than adults
 Homeostatic mechanisms stabilize ICP
 Intracranial contents include :
Brain parenchyma — 80 %
Cerebrospinal fluid — 10 %
Blood — 10 %

17. Compliance
 Compliance is the
interrelationship between
changes in the volume of
intracranial contents and
changes in ICP
 The compliance relationship is
nonlinear
 Compliance decreases as the
combined volume of the
intracranial contents increases
Point of exhaustion
of compliance

18. The Monroe-Kellie doctrine
 Sum of volumes of the 3 components
is constant  an increase in volume
of any one component 
accompanied by a reduction in
volume of at least one of the
remaining two components
 ICP : Function of the volume and
compliance of each component of the
intracranial compartment
 The magnitude and the rate of
change in the volume of each
component determines its effect on
ICP

19. Factors that influence ICP
 Arterial pressure
 Venous pressure
 Intra-abdominal and intra-thoracic pressure
 Posture
 Temperature
 Blood gases (hypoxia / hypercapnia)
 The degree to which these factors ↑ ICP depends on the ability of the
brain to accommodate to the changes.

20. Cerebral Perfusion Pressure (CPP)
 The pressure needed to overcome ICP in order to deliver O2 &
nutrients.
 Clinical surrogate for the adequacy of cerebral perfusion.
 MAP is the DRIVING FORCE ---------- ICP is the RESISTENCE
 CPP = MAP – ICP = 100 mmHg – 15 mmHg = 85 mmHg (Normal)
 CPP < 50 mmHg → cerebral ischemia
 CPP < 30 mmHg → brain death

21. Consequences of altered CSF hydrodynamics
 Abnormal fluid movement (transependymal/transparenchymal)
 Effects of raised ICP
 Circulatory changes (micro and macro)  Ischemia
 Changes in brain morphology/parenchymal damage
 Changes in CSF circulatory path : obstruction/ shunt/ surgery 
Effects of loss or misdistribution of CSF
 Post-shunt or other post-surgical changes
Johnston, I et al. Child's Nerv Syst. 2000

22. Disorders

23. Classification of CSF circulation disorders
Johnston, I et al. Child's Nerv Syst. 2000

24. Hydrocephalus

25. Definition
 Hydrocephalus : derived from two Greek words: hydro = water, and
cephalus = head
 Condition wherein excess of CSF accumulates within ventricular system
and cisterns of the brain leading to increased ICP and related
consequences

26. Types & causes
Functional
Time of onset
of the lesion
Rate of
appearance
of clinical
symptoms
Clinical
symptoms
Intracranial
pressure
Non-
communicating
(obstructive)
Congenital Acute (within
days)
Active Normal pressure
hydrocephalus
(NPH)
Communicating
(non-
obstructive)
Acquired Subacute
(within
weeks)
Occult /
Arrested
Increasing pressure
hydrocephalus
Chronic

27. Types & causes

28. Types & causes
Congenital Acquired
Aqueductal stenosis (MC) SAH/ IVH
Dandy-Walker malformation Infections : TBM
Arnold-Chiari malformation Mass lesions /Tumors
Agenesis of the foramen of Monro Posterior fossa cyst/ Arachnoid cyst
Congenital toxoplasmosis Increased venous sinus pressure
Bickers-Adams syndrome Traumatic brain injury
Neural tube defects Idiopathic

29. Clinical features
 Clinical features of hydrocephalus are influenced by:
 Patient's age
 Cause
 Location of obstruction
 Duration
 Rapidity of onset

30. In infants
Symptoms Signs
Poor feeding Head enlargement
Vomiting Disjunction of sutures
Irritability Dilated scalp veins
Reduced activity/
lethargy
Tense fontanels
Setting sun sign
Increased limb tone

31. In children / adults
Symptoms Signs
Cognitive decline Papilledema
Headache Failure of upward gaze &
accommodation
Vomiting -- morning U/L or B/L sixth nerve palsy
Neck pain Lower limb spasticity
Blurred / double vision Gait apraxia
Difficulty in walking Other signs of raised ICP
Stunted growth and sexual
maturation in children
Macewen sign : A "cracked
pot" sound on percussion of
head in children

32. Diagnostic techniques
 USG
 in infants (due to open fontanel)
and in utero
 CT/MRI scanning : the mainstay of diagnosis
 CSF Flow study
 CSF pressure measurement

33. CT/MRI features
 Increased frontal horn radius
(Mickey mouse ventricle)
 Dilatation of the temporal horns
(>2mm)
 Acute ventricular angles

34. CT/MRI features
 Periventricular interstitial edema
from the transependymal flow :
high T2 signal on MRI or low-
density change on CT
 Intra-ventricular flow void from
CSF movement

35. CT/MRI Features
 Inferior displacement of the
floor of the 3rd ventricle
 Outward bowing / ballooning
of the lateral walls & recesses
of the third ventricle
(infundibular, optic and pineal
recesses)
 Ballooning of the suprapineal
recess

36. CT/MRI Features
 On mid-sagittal plane :
 Upward displacement of corpus
callosum
 Thinned out corpus callosum
 Depression of the posterior
fornix
 Decreased mamillopontine
distance ( normal >5.5mm)

37. CSF flow study
 To qualitatively assess and quantify pulsatile CSF flow
 MC technique : time-resolved 2D phase contrast MRI with velocity
encoding (VENC)
 CSF flow in the context of imaging : pulsatile to-and-fro flow due to
vascular pulsations NOT bulk transport of CSF
 Typical CSF flow is 5-8 cm/s
 Hyperdynamic circulation : much higher velocities : up to 25 cm/s

38. CSF flow study
 Images are typically presented in sets of 3 for each plane and velocity
obtained.
 The set comprises of
 re-phased image (magnitude of flow compensated signal)
• flow is of high signal
• background is visible

39. CSF flow study
 magnitude image (magnitude of difference signal)
• flow is of high signal (regardless of direction)
• background is suppressed
 phase image (phase of difference signal)
• signal is dependent on direction:
forward flow is of high signal;
reverse flow is of low signal
• background is mid-grey

40. CSF flow study
 Clinical applications
 aqueduct stenosis
 normal pressure hydrocephalus (NPH)
 patency of third ventriculostomy
 flow at the cervicomedullary junction (foramen magnum)
 Chiari I malformation

41. CSF pressure measurement
 Direct assessment of elevated ICP
 Surgical placement of ventricular /
intraparenchymal pressure transducer
 Intraparenchymal transducer : more
invasive /real time data/ accurate
determination of ICP
 Helps in management decisions

42. Management
 The main goal is to minimize or prevent brain damage by decreasing ICP
and improving CSF flow.
 Medical management
 Temporary procedures
 External ventricular drainage
 Spinal tap
 Surgical management
 Shunt
 Endoscopic Third Ventriculostomy (ETV)/other endoscopic procedure
 Eliminating the cause of obstruction

43. Medical management
 Acetazolamide:
 Carbonic anhydrase inhibitor
 Reduces CSF production
 Cannot be used as a long-term treatment modality
 Diuretics therapy – tried in infants with bloody CSF : resumption of
normal CSF reabsorption.
 Watch for electrolyte imbalance and acetazolamide side effects:
Lethargy , tachypnea, diarrhea , paresthesias

44. External Ventricular Drainage (EVD)
 Acute hydrocephalus, whether communicating or not : necessitates
urgent or emergent placement of EVD
 It is temporary drainage of CSF
from the lateral ventricles or
the lumbar space of the spine
into an external collection bag.
 An EVD system drains CSF
by using a combination of
gravity and ICP

45. External Ventricular Drainage (EVD)
 Cannot be maintained indefinitely
 Unable to tolerate weaning/clamping of the EVD : permanent shunt
 Acute communicating hydrocephalus patients (i.e. SAH) can
sometimes be managed with EVD with successful weaning and no
shunt placement
 Additional benefits:
 ICP monitoring
 Intraventricular antibiotics
 CSF sampling

46. Spinal tap
 Hydrocephalus after IVH may be transient
 Serial taps (ventricular or LP) may temporize until resorption resumes
 LPs only for Communicating HCP
 No reabsorption when the protein content of the CSF is < 100 mg/dl
Spontaneous resorption unlikely
SHUNTING

47. Shunt surgery
 Recommended for communicating hydrocephalus, including NPH
 Can be used in obstructive hydrocephalus f/b ventriculostomy
 Purpose : to divert CSF flow to another area of the body, where it can be
absorbed
 Ancillary testing before shunt surgery:
 Radionuclitide cisternography
 CSF flow study
 Intracranial pressure measurement
 CSF tap test - 40-50ml of CSF and assessment of gait & cognition.

48. Shunt system & types
 Shunt systems include three components:
 a ventricular catheter (with reservoir)
 a one way valve and
 a distal catheter.
 The ventricular catheter is a straight piece of tubing, closed on the
proximal end with multiple holes for the entry of CSF
 Shunts are composed of a material called Silastic (polymerized
silicone).

49. Shunt system & types

50. Shunt system & types
 Preferred location for the distal catheter : peritoneal cavity
 ease of access
 fewer complications.
 Previous abdominal surgery or peritonitis: ventriculoatrial shunt /
ventriculopleural shunt
 More complications risk of emboli, pleural effusion, pneumothorax,
respiratory distress, and endocarditis with ventriculoatrial /
ventriculopleural shunt

51. Rare types of shunts
 Torkildsen shunt:
 Shunting ventricle to cisternal space
 Lumbo-peritoneal shunt:
 Only for communicating hydrocephalus
 If proximal catheter cannot be placed in ventricle
 Not used in children due to risk of scoliosis
 Cyst/Subdural-Peritoneal shunt:
 Draining arachnoid cyst/subdural hygroma cavity

52. Complications of shunt surgery
 Shunt malfunction:
 caused by infection or mechanical failure
 Approx. 40 percent malfunction : within the first year after placement
 5 percent per year malfunction in subsequent years
 Possible shunt malfunction : development of new or worsening signs
or symptoms of elevated ICP
 Urgent evaluation with detailed neurologic examination and
neuroimaging : CT scan

53. Complications of shunt surgery
 Infection:
 common complication
 5 to 15 percent of procedures
 Can lead to ventriculitis
 Contribute to impaired cognitive outcome and death
 Max risk : first 6 months after shunt placement

54. Complications of shunt surgery
 Common presentation in VP shunt : increasing abdominal pain
associated with peritoneal signs and/or fever
 Only fever in children
 Antibiotics : often not effective alone
 Infected shunt must be removed  placement of EVD
 Perioperative antibiotic prophylaxis / use of antibiotic-impregnated
catheters : lowers risk of infection

55. Complications of shunt surgery
 Mechanical failure :
 Most common : first year after shunt placement
 Major cause : obstruction at the ventricular catheter
 Fractured tubing : approx. 15 % of cases.
 Other causes include
shunt migration (partial or complete) and
excessive CSF drainage (over drainage)
 Requires prompt recognition and surgical intervention

56. Complications of shunt surgery
 Over drainage:
 Functional shunt failure
 Causes subnormal ICP (particularly in the upright position)
 Associated with characteristic symptoms : postural headache and
nausea
 Can lead to slit-ventricle syndrome : small or slit-like ventricles, coupled
with transient episodes of symptoms of raised ICP

57. Endoscopic Third Ventriculostomy
 Involves creating an opening in the
floor of third ventricle to allow CSF to
flow into pre-pontine cistern and
subarachnoid space
 All patients with obstruction between
the third ventricle and the cortical
subarachnoid spaces are potential
candidates for ETV
 Absolute contraindication :
obstruction at the level of the
arachnoid villi or the venous flow in
the superior sagittal sinus

58. Ratke H.,Cerebrospinal Fluid Research 2008

59. Endoscopic Third Ventriculostomy
 Indications:
 Aqueductal stenosis
 Posterior fossa tumors and cysts with hydrocephalus
 Postinfectious hydrocephalus
 Tuberculous meningitis with hydrocephalus
 Hydrocephalus associated with myelomeningocoele and Chiari
malformation
 Hydrocephalus secondary to intracerebral / intraventricular hemorrhage
 Shunt dysfunction

60. Endoscopic Third Ventriculostomy
 Complications:
 infection
 CSF leak
 Surgical complications : subdural, intracerebral, and epidural
hematoma
 hemiparesis, gaze palsy, memory disorders, altered
consciousness, and/or hypothalamic dysfunction
 Postoperative mortality (0.2 percent)
 Delayed sudden death (i.e., >2 years following ETV) due to acute
hydrocephalus from stoma occlusion

62. Recent studies
 Endoscopic third ventriculostomy was found to be safe and effective in TBM
hydrocephalus (Yadav YR et al. Neurology India 2011)
 The evidence at the moment is not sufficient to recommend ETV in the routine
management of TBM related hydrocephalus especially in the early stage ( Misra
UK et al., Ann Indian Acad Neurol. 2012)
 ETV should be considered as treatment of choice in chronic phase of tubercular
meningitis associated obstructive hydrocephalus (Yadav R. et al., Asian J
Neurosurg. 2016)
 ETV gives comparable results in pediatric hydrocephalus with the distinct
advantage of freedom from hardware and its associated risks ( Deopujari et al., J
Korean Neurosurg Soc. 2017)
 Early surgical outcome following ETV is better than VPS surgery in patients with
obstructive hydrocephalus ( Rehman MM et al. Asian J Neurosurg. 2018)

63. Normal Pressure Hydrocephalus

64. Definition
 Refers to a condition of pathologically enlarged ventricular size with
normal opening pressure on lumbar puncture
 A form of communicating hydrocephalus

65. Types
 Idiopathic NPH : When no obvious cause is identified
 Secondary NPH : Impaired absorption of CSF is the suspected
mechanism in most cases of secondary NPH.
 The MC causes are :
 Intra-ventricular or subarachnoid hemorrhage
 Prior acute or ongoing chronic meningitis
 Paget disease at the skull base, mucopolysaccharidosis of the meninges,
and achondroplasia are other rarely reported causes of secondary NPH

66. Clinical features
 Three cardinal features:
 Gait difficulty : most prominent clinical feature, a magnetic or "glue-
footed" gait
 Cognitive impairment with subcortical and frontal features, including:
• Psychomotor slowing
• Decreased attention and concentration
• Impaired executive function
• Apathy
 Urinary incontinence
 Absence of signs and symptoms related to increased ICP : headaches,
nausea and vomiting, visual loss or papilledema

67. Additional Radiological findings
 The Evans' index
Ratio of maximum width of the frontal horns of the lateral ventricles (A)
and maximal internal diameter of skull (B) at the same level
Employed in axial CT / MRI images
Varies with the age and sex
Marker of ventricular volume
A/B > 0.3 - Hydrocephalus

68.  Narrow callosal angle :
Angle measured on a coronal image perpendicular to the anterior
commissure - posterior commissure (AC-PC) plane at the level of the
posterior commissure
Normal = 100-120°
NPH = 50-80°

69.  Cingulate sulcus sign :
Denotes the posterior part of the cingulate sulcus being narrower than
the anterior part.
Divider b/w anterior and posterior parts of the sulcus : line drawn parallel
to the floor of 4th ventricle

70.  Cerebral aqueduct flow void
Loss of signal in the aqueduct of Sylvius
Represents higher-than-normal flow velocity of CSF in the aqueduct

71.  DESH (Disproportionately
enlarged subarachnoid space
hydrocephalus)
Characterized by:
• Ventriculomegaly
• Tight high-convexity and medial
subarachnoid spaces
• Disproportionate enlargement of
the Sylvian fissures
• Focally dilated or entrapped sulci
without adjacent cortical atrophy
• Acute callosal angle

72.  Feature of idiopathic NPH = DESH-iNPH
 May be complete or incomplete
 Predicts favorable outcome after shunt surgery
Akiguchi I.et al, Annals of Clinical and Translational Neurology 2014
Shinoda N. et al, Journal of Neurosurg 2017

73. Management
Bradley’s Neurology 7th ed.

74. Hydrocephalus ex vacuo
 Compensatory enlargement of the CSF spaces
 Seen in :
 asymptomatic elderly people : aging brain with related volume loss
 pathological conditions that promote brain shrinkage:
• generalised brain degeneration (e.g. Alzheimer disease and
leukodystrophies)
• encephalomalacia due to focal damage (e.g. stroke and traumatic
injuries)

75. Benign external hydrocephalus
 Enlargement of the subarachnoid space
 frontal or
 frontoparietal regions
 Ventriculomegaly : absent or mild.
 Clinically, infants have macrocephaly but otherwise well-appearing and
have normal development.
 Presentation : progressive increase in the head circumference with normal
anterior fontanel.
 Family history of macrocephaly : Frequent
 Self-limited
 Do not require any intervention

76. Arrested hydrocephalus
 Asymptomatic/ occult/ compensated/ long
standing overt ventriculomegaly of adulthood/
late onset idiopathic aqueductal stenosis
 Moderate to severe tri-ventricular enlargement
 No evidence of periventricular fluid
accumulation on imaging
 Stable for years
 Incidental diagnosis
 Conservative approach with serial imaging
 May be associated with cognitive decline or
sudden decompensation

77. Intracranial Hypotension

78. Definition & Types
 Defined as CSF pressure < 60 mm H2O in patients with clinical
presentation compatible with intracranial hypotension
 Most commonly results from a CSF leak somewhere along the neuraxis
 Intracranial hypotension can broadly be divided into:
 primary: referred to as spontaneous intracranial hypotension (SIH)
 secondary:
• iatrogenic (lumbar puncture or surgery)
• over-shunting due to diversion devices,
• traumatic

79. Causes
 SIH : usually result from CSF leak in the spine.
 Causes include :
 spontaneous dural dehiscence of meningeal diverticula (perineural
cyst)
 degenerative dural tears
 congenital focal absence of dura (nude nerve root) - rare
 CSF-venous fistula

80. Presentation
 Presentation : positional headache
 relieved by lying in recumbent position within 15-30 minutes
 Nausea/vomiting/vertigo/neck pain
 Traumatic or iatrogenic intracranial hypotension : history of
abundant, clear rhinorrhea or otorrhea present.
 Occasionally, presentation is more sinister, with reported cases of
decreased level of consciousness and coma

81. Radiographic features
 Imaging is crucial both for confirming the diagnosis of intracranial
hypotension and identifying the location of the leak
 CT
 subdural collection
 acquired tonsillar ectopia
 dural venous sinus distention

82. MRI
 pachymeningeal enhancement
 venous distension sign
 Subdural effusions / hematomas
 sagging brainstem /
acquired tonsillar ectopia
 pituitary enlargement
 diffuse cerebral edema
 reduced CSF volume
 decreased fluid within
the optic nerve sheath

83. Other useful investigations
 Spine MRI
 CT cisternography
 Radioisotope cisternography
 CT myelography / Dynamic CT myelography
 MR myelography

84. Management
 Conservative
 Avoidance of the upright position : strict bed rest and the possible
addition of analgesics.
 Restoring CSF volume : oral or i.v. hydration, high oral caffeine intake,
and high salt intake
 Epidural blood patches : first line
 infusion of 10 to 20 cc of autologous blood into the epidural space
 may be repeated
 Adverse effects : back pain, radiculopathy, leg paresthesias, and fever
 Epidural fibrin glue
 Surgical repair

85. Next Seminar:
Idiopathic Intracranial Hypertension (IIH)
By Dr. Sarvesh