Dr. T. Balasubramanian M.S.
Definition: CSF discharging from the
nose is known as CSF rhinorrhoea. Cerebrospinal fluid is a clear
colorless fluid that bathes the brain and spinal cord, cushioning
them against trauma. In fact in literal terms the brain and spinal
cord floats in the cerebrospinal fluid. The specific gravity of
brain is only 4% of that of CSF, hence it could float easily in the
Functions of CSF:
1. It cushions the brain and spinal cord against
2. It nourishes the brain tissue.
3. It removes waste materials.
The brain and spinal cord is covered by 3 layers of
meninges: They are 1. The duramater
These layers of meninges bound three spaces between them.
1. Epidural space: is the space that lies between the
inner perioseteal lining of the skull / vertebral canal and the
2. Subdural space: is the space that lie between the
duramater and the arachnoid.
3. Subarachnoid space: lies between arachnoid and
piamater. This space contains the cerebrospinal fluid. This space
continues with the ventricles of the brain. Large blood vessels of
the brain traverse this space. This space also extends along the
olfactory nerves to the mucoperiosteum of the nasal cavity. It also
extends along blood vessels as they enter and exit the
brain. At its inferior aspect the subarachnoid
space is dilated and becomes lumbar cistern. This area is accessed
while doing a lumbar puncture.
showing anatomy of meninges
Ventricles: are 4 CSF filled cavities in the brain. These
ventricles are lined by ependyma (cuboidal epithelium). This lining
has a secretory function.
Lateral ventricles: are two in number one in each
cerebral hemisphere. These lateral ventricles communicate with the
Foramen of Munroe to the third ventricle. Choroid plexus of the
lateral ventricle are located in the medial wall of the
3rd and 4th ventricles: are unpaired, midline ventricles.
The third ventricle is connected to the lateral ventricles by the
Foramen of Munroe. The third and the fourth ventricles are connected
to each other by the Aqueduct of Sylvius. This aqueduct is lined by
ependyma and does not contain choroid tissue. The choroid plexus of
the third ventricle is found over the roof.
The third ventricle is a slit like cleft lying between
the thalami of the brain. The fourth ventricle is situated anterior
to cerebellum and posterior to the pons. The fourth ventricle
continues inferiorly with the central canal of the spinal
These ventricles communicate with the subarachnoid space
through 3 openings in the roof of the 4th ventricle. They are 1.
Foramen of Magendie, which is a single foramen located over the roof
of the 4th ventricle and 2. Foramen of Luschka which are 2 in number
Physiology of CSF circulation:
The normal CSF pressure ranges between 60 - 150 mm of
water. This pressure varies according to age, position of the head
and other associated factors. It is increased during valsalva
manuvers, coughing and straining. It is also increased during
jugular vein compression.
CSF pressure in neonates is very low due to the
pliability of the cranial cavity prior to the closure of cranial
CSF production: The choroid plexus located inthe lateral
3rd and 4th ventricles produces CSF. This accounts for 2/3 of the
total production. Extra choroidal production occurs in the ependyma
tissue of the ventricle. The rate of production of CSF is about 500
cc / day, or 0.30ml/min. In adults the total CSF volume is 150ml.
The whole volume of the CSF is turned over about 3 times a
CSF absorption: Occurs at the arachnoid villi and
arachnoid granulation. These are finger like projections intimately
associated with the dural venous sinus. Resorption is a passive
phenomenon, obeying the laws of pressure gradiant.
showing lateral view of ventricles and csf
CSF flows from the site of production in the ventricles
through the foramen of Megendie and Luschka exiting the cisterna
magna and the basal cisterns to enter the subarachnoid space. The
arterial pulsations propels the CSF from the ventricles into the
subarachnoid spaces overlying central convexities. Flow within the
spinal cord is facilitated by motions of the vertebral column.
CSF Leaks always occur when the barrier that retains the
Cerebrospinal fluid is breached. These barriers are skin, galeal
periosteum, skull, dura and arachnoid. The mucosal lining of the
nasal cavity also forms its last line of defence.
Causes of CSF rhinorrhoea:
a. Accidental: Acute /
b. Iatrogenic: Acute / Delayed
a. High pressure
i. Tumors: Direct / Indirect
b. Normal pressure:
i. congenital anamolies
ii. Focal atrophy - Olfactory / Sellar
iii. Osteomyelitic erosion
Types of CSF rhinorrhoea:
II. Non traumatic (spontaneous) - a.
High pressure leaks (always associated with
The high pressure leaks are commonly encountered in the
cribriform area. This is due to the fagility and unique anatomy in
this area i.e. (prolongation of the subarachnoid space along the
olfactory filaments). The leak during these conditions functions as
a safety valve alleviating the increased intracranial
pressure. These high pressure leaks are associated
with slow growing tumors and 1/4 of them have hydrocephalus.
Pituitary neoplasms are the most common type of intracranial tumor
found, next common are the posterior cranial fossa lesions. Direct
invasion of the skull base is not the usual mechanism of this leak.
Closure of these leaks may worsen the condition of the patient if
the causative lesion is left untreated.
b. Normal pressure leaks - These leaks
are associated with congenital dehiscence or thin bone along the
skull base. Commonly this type of leaks occur in the ethmoidal sinus
adjacent to the cribriform plate. Potential leak
pathways include the prolongation of the subarachnoid space along
the olfactory nerves and stalk of the hypophysis. Minor degrees of
maldevelopment of the cribriform plate or the diaphragma sella may
allow further extension of the subarachnoid space through the
foramina of the cribriform plate or around the hypophysis (empty
sella). The former is common and accounts for the majority of normal
Cerebrospinal leaks needs to be treated because of the
impending threat of meningeal infections.
showing AP view of
showing the various routes of CSF
Spontaneous CSF rhinorrhoea:
True spontaneous leaks are really rare. There is almost
always some antecedent traumatic event.
Nuss postulated the various causes of spontaneous CSF
rhinorrhoea. He named them as "4 P's".
1. Increased intracranial pressure
2. Brain pulsations which continuously occur along the
3. Degree of pneumatisation of the paranasal
4. Arachnoid pits / villi exist normally along the skull
base. Continued transmission of pulsation, erodes the bone until the
arachnoid communicates with a pneumatised space with the potential
to develop fistula.
Trauma: is the commonest etiology
Iatrogenic: Surgery involving skull base and paranasal
sinuses may cause CSF rhinorrhoea due to breach in the skull
Congenital: Meningocele and
Bedsite tests for detecting CSF rhinorrhoea:
Reservoir sign: This test is ideally
performed immediatly on rising from the bed. The patient is asked to
place the chin over their chest. The patient must stay in that
position for one full minute. Clear fluid dripping from the nose is
Handkerchief test: Discharge from the nose is blown into
a handkerchief and is allowed to dry. If the discharge is CSF the
handherchief will not stiffen, if the discharge is secretions from
the nose the handkerchief stiffens due to the presence of mucin in
the nasal secretions.
The most sensitive laboratory test is to look for Beta 2
transferrin in the nasal secretions. In CSF Beta 2 transferrin is
present, and it is absent in normal nasal secretions.
The most sensitivve test to detect CSF leak is
intrathecal radionucleotide test.
Tests that help to localise the CSF leak:
1. Flow sensitive MRI is useful. The leak must be active
at the time of the scan for visualising the site. The advantage of
this test is that it is non invasive.
2. Intra thecal administration of non ionic contrast with
high resolution CT scan. Intra thecal administration of low
quantities of flurescein can also be used. If the leak is present it
can be viewed in the nasal cavity with a 490 nm light generated by a
special optical filter. Dye injection is done using Barbolage
technique in which 1 - 2 drops of 5 % Fluoresate is diluted with the
patients own CSF, and then injected partially, then CSF is withdrawn
further diluting the dye and then reinjecting the dye.
1. Bed rest
2. Elevation of the head end of the bed
3. Stool softeners
4. Short course of azetazolamide
5. Continuous / daily intermittent lumbar spinal drainage
helps to reduce the fistula
6. Antibiotic prophylaxis to prevent meningitis.
CSF leaks into the nose can be approached by two
1. Intracranial repair
2. Extracranial repair
Intracranial repair: till recently this was the commonest
approach adopted to repair CSF rhinorrhoea. Leaks from the anterior
defects can be repaired by frontal anterior fossa craniotomy. A
middle cranial fossa craniotomy or posterior fossa craniotomy can be
used to mangage leaks from these areas. Leaks from the sphenoid
sinus area are diffucult to approach via the intracranial route. The
repair techniques involve use of a pedicled periosteal or dural
flaps, muscle plugs can be used to plug the defects, mobilised
portions of falx cerebri or other facial grafts can be utilised.
Fibrin glue can be used to stabilise the grafts used in case of
The advantages of this approach are
1. The adjacent brain tissue can be directly
2. Direct visualisation of the dural defect
3. The repair can also be done even under conditions of
increased intracranial tension
4. Even if efforts to localise the leak fails blind
repair is possible in this approach. The areas covered with grafts
must include the cribriform plate and the sphenoid
Disadvantages of this approach:
1. Increased morbidity
2. Increased risk of permanent anosmia
3. Trauma related to brain retraction (hematoma, oedema,
seizures, cognitive dysfunction etc)
4. Longer hospital stay
Extracranial repair: This can be divided into external
approaches and endoscopic techniques
This include anterior osteoplastic approach via bicoronal
or eyebrow incision, external ethmoidectomy, transethmoidal
sphenoidectomy, and transeptal sphenoidectomy. Graft materials used
could range from fascia lata, temproalis fascia, septal cartilage,
turbinate mucosa, muscle and fat. For cribriform plate, or fovea
leaks a transnasal ethmoidectomy is performed. For sphenoid leaks
sphenoidectomy is performed.
Disadvantages of this procedure include:
1. Inability to repair associated intracranial
2. Ineffective in repairing high pressure leaks
3. Ineffective in repairing frontal and sphenoid sinus
leaks when they have prominent lateral extensions
This method has several advantages including better
visualisation and magnification. Other advantages include the
ability to clean the mucosa adjacent to the leak, and in accurate
positioning of the graft to plug the leak. There is no threat of
anosmia, and this procedure has low morbidity.
site contents © Copyright drtbalu 2006, All rights