HYDROCEPHALUS AND ITS CAUSES

29-9-2012Dewan Auditorium, HTAA

EMERGENCIES IN NEUROSURGERY 2012Symposium 7: Hydrocephalus

WHAT IS HYDROCEPHALUS?

Abnormal build-up of cerebrospinal fluid

Ventricular System in the Brain or subarachnoid space

causes an increase in pressure

Ventricular System in the Brain

• Cerebral Spinal Fluid (CSF) is mostly made in the ventricular system of the brain. This fluid then circulates throughout the brain as well as down the spine.

Normal Cerebral Spinal Fluid Flow

• Most of the CSF is produced in the body of the lateral ventricle.

• Normally, it will flow from the lateral ventricle down through the Foramen of Monro into the III ventricle.

• From there it proceeds down the aqueduct into the IV ventricle.

• There are three openings in the IV ventricle: – Laterally are the

foramen of Lushka– Medially or in the

middle is the foramen of Magendie.

Cranio-caudal systolic CSF flow

cardiac systole

Transmission of cerebral

arterial pulsation

Generalized expansion of the

intracranial volume

Monro-Kellie doctrine

The volume of the intracranial contents

(brain, CSF, blood) remains constant all times.

Increase in intracranial volume is dissipated by an outflow of CSF from intracranial subarachnoid spaces and the ventricular system down to the compliant spinal subarachnoid space,

Xavier Morandi *, Seyed F.A. Amlashi, Laurent Riffaud; Medical Hypotheses (2006) 67, 79–81

spinal subarachnoid space

Caudo-cranial diastolic CSF flow

Diastole

The elastic property of the spinal dura mater

decreased cerebral blood flow

CSF is pushed in theopposite direction in the intracranial

space

Xavier Morandi *, Seyed F.A. Amlashi, Laurent Riffaud; Medical Hypotheses (2006) 67, 79–81

Ventricular System in the Brain

• When there is too much fluid in the ventricular system, it dilates and can squeeze the surrounding brain tissue.

• This is hydrocephalus

• HYDROCEPHALUS – Ventricular system

is becoming larger – The ventricles are

becoming round• Since the skull is a

closed space containing the brain, increasing the size of the fluid compartment (the ventricles) begins to displace the adjacent parts of the brain resulting in neurological symptoms.

Ventricular System in the Brain

WHAT IS OBSTRUCTIVE HYDROCEPHALUS?

• Obstruction to normal cerebral spinal fluid pathways may involve any portion of the ventricular system.

Multicompartmental model of ventricular volume regulation. (Rekate et al. 1988)

Obstructive Hydrocephalus: Example

• There is a mass (tumor) at the level of the Foramen of Monroe and the III Ventricle.

• The CSF flow is obstructed and cannot flow down into the III Ventricle to the aqueduct, into the IV ventricle and then out around the brain and down into the spinal cord.

• The ventricular system is enlarged proximal to (before) the level of the blockage.

• Both lateral ventricles, especially the frontal horns are dilated.

Basic Clinical Anatomy: Radiographic Correlation

Causes of Hydrocephalus

Obstructive Hydrocephalus: Causes

• Aqueductal Stenosis, Tumors, Cysts and Hypertensive Hemorrhages

Obstructive Hydrocephalus: Aqueductal Stenosis

• Aqueductal Stenosis is seen mostly in infants and young adults.

• It can present later on in the teenage years as well.

• With more and more people having CT and MRI brain scans, we are seeing people in their 50's and even 70's (adult) with aqueductal stenosis.

• Essentially, the aqueduct is atretic

• Since cerebral spinal fluid (CSF) cannot flow down into the IV Ventricle, obstructive hydrocephalus develops.

• Characteristically, everything proximal to the aqueduct dilates. The IV Ventricle remains normal in size.

Aqueductal Stenosis : CT Scan

• The frontal horns, the III ventricle and the temporal horns are all enlarged.

• The IV ventricle which is distal to the aqueduct is normal in size.

Obstructive Hydrocephalus: TUMOR

• Cerebellar Brain Tumor pushing on the IV Ventricle 

• This is a common location where brain tumors cause hydrocephalus, invading the IV ventricle and blocking CSF (cerebral spinal fluid) flow

• Sometimes strokes or hemorrhages may cause this sequence of events as well.

Obstructive Hydrocephalus: TUMOR

• Cerebellar Brain Tumor pushing on the IV Ventricle 

• The CT Scan shows a cross section of the problem in a patient with a cerebellar tumor and swelling.

• The CSF can flow down its usual pathway, but it is beginning to become obstructed by the tumor.

• Unless treated, as the tumor grows the ventricle will close off and obstructive hydrocephalus will develop.

• Symmetry of the IV ventricle is lost. The black in the IV Ventricle is Cerebral Spinal Fluid. The lighter grey tissue is the cerebellum.

• The darker grey tissue is tumor plus swollen cerebellum.

Obstructive Hydrocephalus: CYST

• Loculated cysts in the III ventricle causing early obstructive hydrocephalus

• The MRI shows an enlarged III ventricle.

• There are loculated cysts within the III ventricle.

• These cyst formed due to scarring from a patient with meningitis.

• CSF cannot flow past the III ventricle, so the lateral ventricles begin to enlarge.

• The aqueduct and IV ventricle are normal in size.

Obstructive Hydrocephalus: CYST

• Enlarged III Ventricle With Development of Early Hydrocephalus

• The CSF can flow down its usual pathway, but it is beginning to become obstructed by the enlarged III ventricle.

• Unless treated, obstructive hydrocephalus will develop.

Obstructive Hydrocephalus: CYST

• Porencephalic Cyst and Enlarged Ventricles... is this Hydrocephalus?

• When a cyst communicates (is continuous with) one of the ventricles, it is usually congenital (formed during pregnancy).

• There is a large cerebellar cyst communicating with an enlarged IV ventricle.

• The III ventricle is mildly enlarged as well. Is this early hydrocephalus?

Obstructive Hydrocephalus: HYPERTENSIVE HEMORRHAGE

• Bleeding into the brain from high blood pressure causing early obstructive hydrocephalus

• The CT Scan shows an enlarged ventricular system.

• CSF cannot flow past the blood clot so the lateral ventricles begin to enlarge.

• High blood pressure (Hypertension) is a common cause of brain hemorrhages.

• When hemorrhages occur from hypertension, many times the patient will bleed into the ventricular system and/or into the surrounding brain structures.

• These structures are often the thalamus and basal ganglia.

Obstructive Hydrocephalus: HYPERTENSIVE HEMORRHAGE

• Bleeding into the brain from high blood pressure causing early obstructive hydrocephalus

• The CSF can flow down its usual pathway, but it is beginning to become obstructed by the hemorrhage.

• Obstuctive hydrocephalus is developing

COMMUNICATING HYDROCEPHALUS

• Communicating hydrocephalus develops when there is more fluid being produced than can be absorbed.

• The ventricular system enlarges to hold the excess fluid.

• This compresses the surrounding brain tissue.

• Communicating Hydrocephalus may result from various types of hemorrhages.(Post Hemorrhagic, Subarachnoid Hemorrhage, Other Hemorrhage).

• There is a special case of Communicating Hydrocephalus called Normal Pressure Hydrocephalus.

Communicating Hydrocephalus: CT Scan

• Notice how all the ventricles are enlarged. Compare this image to the CT Scans below.

Normal, No Hydrocephalus: CT Scan

Communicating Hydrocephalus: SUBARACHNOID HEMORRHAGE  • Bleeding into the brain

from an aneurysm rupture may cause communicating hydrocephalus 

• The CT Scan to the left shows an enlarging ventricular system.

• The blood results in decreased absorption of the CSF.

• The production of CSF continues so a net increase of CSF occurs.

• Thus, the ventricles begin to enlarge.

• About 10% of people who suffer SAH (subarachnoid hemorrhage) develop hydrocephalus.

Communicating Hydrocephalus: SUBARACHNOID HEMORRHAGE 

• Delayed communicating hydrocephalus from SAH

• Sometimes hydrocephalus is not apparent during the acute treatment of an aneurysm rupture.

• It may present itself several months later.

• Follow-up CT scans are important to diagnose delayed hydrocephalus if clinically indicated.

Communicating Hydrocephalus: NORMAL PRESSURE HYDROCEPHALUS (NPH)

• Clinical Triad• Various degrees of the

following three complaints: – Worsening Gait, – Worsening Memory

and – Increasing Urinary

Incontinence.

Communicating Hydrocephalus: NORMAL PRESSURE HYDROCEPHALUS (NPH) • MRI scans and normal

pressure hydrocephalus• The MRI scan usually

demonstrates large ventricles.

• In elderly individuals there may be cerebral atrophy (shrinkage of the gray matter).

• Cerebral Spinal Fluid will fill up the space of a brain with atrophy.

• However, in NPH, the enlarged fluid space (ventricles) are enlarged out of proportion to the cerebral atrophy.

1913 Johns Hopkins University

Dr. Walter Dandy

The first studies in experimental animals related to theinjection of a supravital dye into the ventricle and

attempting to recover it from the spinal subarachnoid space(SSAS) via lumbar puncture.

communicating non-communicating

“obstructive”

Why questions the simpleclassification of Dandy?

• Some patients who developed hydrocephalus in infancy or had arachnoid cysts treated with shunts in infancy develop severely increased intracranial pressure with no expansion of the ventricles or cyst at the time of shunt failure

• Never lead to the understanding of normal pressure hydrocephalus (NPH) and pseudotumor cerebri (PC)

CSF dynamics• Techniques for the study of CSF

dynamics had improved dramatically since the studies of Dandy.

• Tools such as magnetic resonance imaging (MRI), Cine MRI flow studies, cisternography utilizing dye studies and especially long-term studies of the outcomes of treatment decisions make it possible to accurately define a point of restriction of flow.

CSF compliance• Between 30% and 70% of total CSF system

compliance has been attributed to the spinal compartment

• The remaining one to two third of CSF system compliance consists of changes in the vascular pool, especially the intracranial venous system (Vascular compliance)

• These two systems are in equilibrium instantaneously and any variations in either compartment result in rapid compensatory changes in the other

Xavier Morandi *, Seyed F.A. Amlashi, Laurent Riffaud; Medical Hypotheses (2006) 67, 79–81

Compliance= to the ratio of volume and pressures changes (dV/dP)

Compliance of the spinal compartment

• Based on – an increased elasticity of the spinal dura

mater– a wide epidural space with an extended

compressible epidural venous plexus– sub-atmospheric epidural pressure

Xavier Morandi *, Seyed F.A. Amlashi, Laurent Riffaud; Medical Hypotheses (2006) 67, 79–81

Until now there has been no consensus as to a more

contemporary classification scheme

ICD 10

Members of the Hydrocephalus Classification Study Group January of 2010

The structure of the consensusFirst level of

classification of hydrocephalus

Based on the pointwhere the flow of CSF is restricted

Foramina of Monro, The aqueduct of Sylvius,

The basal cisterns, The arachnoid granulations,

Outflow of venous blood from the dural venous sinuses

without a point ofobstruction or increased resistance to flow.

communicating hydrocephaluscommunicating hydrocephalus

Modified by

Second level ofclassification of hydrocephalus

The etiology The chronicity or rapidity of onset

The age of the person

overproduction of CSF (e.g. by choroid

plexus papillomas)

Thank You