This document discusses cerebrospinal fluid (CSF) circulation and the mechanics of hydrocephalus. It describes CSF production and flow, intracranial pressure, choroid plexus structure and function, CSF regulation and absorption. Hydrocephalus is classified based on overproduction, obstruction, or absorption defects. Pathophysiologic mechanisms including gliosis, inflammation, intracranial pulsatility and CSF absorption are examined. Specific causes of hydrocephalus like post-hemorrhagic, meningomyelocele, aqueduct stenosis and more are outlined.

1. CSF CIRCULATION
AND
MECHANICS OF
HYDROCEPHALUS

2.  CSF formation - 0.4 mL/min per gram
of choroid plexus or 0.35 mL/min
 Choroidal blood flow- 4 mL/min per
gram
 80% - Lateral, 3rd and 4th ventricles
 20% - Interstitial space and
ependymal lining
INTRODUCTION

3. Total CSF volume
◦ Infant - 50 mL
◦ Adults - 150 mL
Production rate
◦ Infant - 25 mL/day
◦ Adults - 500 mL/day
Intracranial pressure
◦ Infants - 9 to 12 cm H2O
◦ Adults - less than 18 to 20 cm H2O

4. The Monro-Kellie Doctrine
The sum of intracranial contents to
include blood, CSF, and brain should
remain constant in a fixed container,
such as the skull.
 < 2 to 3 years of age – this does not
apply

5. CHOROID PLEXUS

6. BLOOD SUPPLY OF CHOROID
PLEXUS

8. A
T
P
3Na
2K
A
T
P
Na
Na Na
Na
K 2Cl- Cl-
Cl-
HCO3
-
HCO3
-
HCO3
-
HCO3
-
H+
CA
H2O + CO 2  HCO3
- +H+
H2O
AQ 1
CSF
INTERSTITIUM
Choroidal cell
Apica
l
Basolater
al

9. REGULATION OF
CEREBROSPINAL
FLUID FORMATION
 Neurohumoral Ligands and Receptors
 Sympathetic
 Parasympathetic
 Serotonin (5HTc)
 AVP
 ANP
 Diuretic Agents and Ion Transporters
 Ouabain
 Digoxin
 Bumetanide
 Furosemide

10. CEREBROSPINAL FLUID
FLOW
CSF flow rate depends on
◦ Upstream choroidal
◦ Mainstream ventriculocisternal
◦ Downstream arachnoidal fluid throughput

12.  Slowing of CSF flow disturbs both
trophic and excretory functions in the
CNS
 Pulsatile movement during each
cardiac cycle – CSF movement
Anterograde caudal flow
Retrograde cranial flow

13. ABSORPTION OF
CEREBROSPINAL FLUID
The only proven force responsible for
bulk CSF absorption is that of a
hydrostatic gradient

14.  Absorption via the Arachnoid Villus
 Absorption into the Lymphatic System
 Absorption via the Brain
 Absorption via Blood Vessels
 Absorption at the Nerve Root Sleeves
 Absorption from the Subarachnoid
Space

15. CLASSIFICATION OF
HYDROCEPHALUS

16. A. Over production of CSF (a rare entity)
B. Obstructive: wherein there is
obstruction to the flow of CSF in the
◦ Lateral ventricles
◦ Foramen of Monroe
◦ Third ventricle
◦ Aqueduct of Sylvius
◦ Fourth ventricle
◦ Subarachnoid spaces
C. Absorption defect

17. Based on the site of blockage :
 Monoventricular
 Biventricular
 Triventricular
 Panventricular

18. Based on exact aetiology
1. Congenital
2. Traumatic
3. Inflammatory
4. Neoplastic
5. Degenerative

19. CSF FORMATION RATE IN
HYDROCEPHALUS

20.  Reduced fluid turnover in hydrocephalus:
◦ Reduced choroid plexus blood flow
◦ Epithelial cell shrinkage or damage
◦ Diminution of blood-CSF surface area
 Ventricular pressure = Net fluid
filtration
 ICP  Release of neurohumoral agents
 Choroid plexus epithelial receptor–
mediated inhibition of CSF production.

21. PATHOPHYSIOLOGIC MECHANISMS
Gliosis and Inflammation
 Glial fibrillary acidic protein (GFAP)
 Aquaporin 4 (AQP4)
 Minocycline as a specific inhibitor of
microglial cells

22. Intracranial Pulsatility
 Ventricular dilation can be caused by
abnormal intracranial pulsatility
 Dissipation of cerebral arterial
pulsatility, resulting in minimal
(homeostatic) capillary and venous
pulse pressure, is believed to be
critical for normal cerebrovascular
function

23. CSF Absorption
 Lymphatic, Arachnoid, Microvascular
 Latest in vivo studies - cranial
lymphatics, most notably the nasal
pathways surrounding the olfactory
nerves, are capable of transporting
large volumes of CSF.

24. A
T
P
3Na
2K
A
T
P
Na
Na Na
Na
K 2Cl- Cl-
Cl-
HCO3
-
HCO3
-
HCO3
-
HCO3
-
H+
CA
H2O + CO 2  HCO3
- +H+
H2O
AQ 1
CSF
INTERSTITIUM
Choroidal cell
Apica
l
Basolater
al
Ouabain Bumetanide
Digoxin
Furosemide
Furosemide
Acetazolamide
Amiloride

25. Post-Haemorrhagic
 Premature infants born before 34
weeks have a high incidence of
intracranial haemorrhage
 majority occurs within the first few
days of birth

26. Meningomyelocoele
 It may manifest after closure of the
meningomyelocoele, as the sac acts
as a CSF sump

27. Aqueduct Stenosis
 Communicating hydrocephalus with
external pressure on the
mesencephalon
 Scaring and gliosis following infection
or haemorrhage
 Tumours from the surrounding
structures

28. Dandy Walker Syndrome
 Agenesis of the cerebellar vermis
 Cystic dilation of the fourth ventricle
 Enlargement of the posterior fossa
 Hydrocephalus

29. Post-Meningitic
 Bacterial, parasitic and granulomatous
 infections like tuberculosis and fungal
infections.
 Hydatidosis
 Toxocara
 Viral infections

30. Subarachnoid Haemorrhage
 Can occur in 10–15% of patients with
subarachnoid haemorrhage
 Impaired absorption due to blockage
at multiple sites.

31. Normal Pressure
Hydrocephalus
 In some cases, it may be secondary to
infection or haemorrhage in the past

32. Hydrocephalus and Venous
Hypertension
 Otitic-hydrocephalus
 Seen in anchondroplasia and
syndromic craniostenosis

33. Arrested Hydrocephalus
 Persistent ventricular enlargement
with normal CSF pressures
 Disproportionate headgrowth,
progression of ventricular size and
intellectual decline are indications for
intervention

34. Multiloculated Hydrocephalus
 Usually occurs after an initial episode
of neonatal meningitis or a germinal
matrix haemorrhage
 Different from cysts associated with
hydrocephalus - Dorsal cyst
malformations.

35. Hydrocephalus Ex-vacuo
 Enlargement of the ventricles
secondary to cerebral parenchymal
damage.
 Ageing, head trauma, severe infection,
hypoxia or ischaemic insults,
radiotherapy ,chemotherapy
 Associated with white matter loss and
concomitant enlargement of the
cortical sub-arachnoid spaces and
basal cisterns.