Hydrocephalus
Hydrocephalus
Hydrocephalus
Clinical Management
Definition:
Hydrocephalus refers to an excessive accumulation of the cerebrospinal fluid (CSF)
within the cerebral ventricles &/or subarachnoid space, associated with ventricular
enlargement (ventriculomegaly) due to a disturbance of the CSF circulation (CSF
production, flow or reabsorption) causing high-CSF pressure (high-ICP)-related clinical
problems.
Basic Anatomy/Physiology:
The spaces within which the CSF circulates are:
1) The cerebral ventricles.
2) The subarachnoid space (cranial and spinal).
3) The basal subarachnoid CSF cisterns.
The Cerebral ventricles are the cavities in the central part of the brain, lined by a
layer of ependymal cells (ciliated-epithelial glial cells). There are 1) two lateral
ventricles (right and left, each of which has a body and three horns, namely the
anterior, posterior and inferior horns), 2) a median third and 3) fourth ventricles.
CSF is a clear fluid produced mostly (70-80%) by dialysis of blood in the choroid
plexus. The choroid plexus is found in all the cerebral ventricles. A small proportion of
CSF may be produced from ventricular ependyma and brain parenchyma.
CSF is produced at a rate of 0.33 ml/min, which is approximately 500 ml/day. The total
volume of CSF varies with age and in the adults is 100–150 ml of which 15–25 ml is
contained within the ventricles. Once produced, CSF will then circulate, due to
hydrostatic pressure (pressure gradient between ventricles and cerebral venous
system), and end in the cerebral venous blood.
Functions of CSF:
* To keep the brain tissue floating (cushion or shock-absorber).
* Delivering nutrients to brain.
* Removal of waste materials.
* Compensate for changes in intracranial blood volume (raised ICP) by moving between
the brain and the spinal cord.
Classifications of Hydrocephalus:
Hydrocephalus may be classified on various basis and for particular purposes.
1) Congenital or Acquired:
this classification aims primarily to identify the causative pathology behind the
hydrocephalus (What to treat?), besides establishing plans to prevent the occurrence of
more cases by following certain prophylactic measures.
Congenital: present at birth (can be diagnosed antenatally). Common causes are
congenital anomalies (aqueduct stenosis or neural tube defect) and intrauterine CNS
infections.
Acquired: develops at the time of birth or at any time afterwards. Brain tumours and
meningitis are common examples.
2) Communicating or non- communicating (Obstructive):
the aim of this classification is to decide the preferred modality of treatment
accordingly (How to treat?)
Communicating: normal CSF flow between the ventricles but disturbed absorption to
the venous system. The pathology lies after the exit of CSF from the fourth ventricle to
the subarachnoid space, mostly due to obliteration of subarachnoid CSF cisterns or
arachnoid villi. Common example for this type is the post aneurysmal SAH
hydrocephalus. Only CSF shunting can be used for treatment. The ventriculomegaly
here includes all the cerebral ventricles.
Obstructive: the flow of CSF between the ventricles is blocked. Most commonly
affected is the cerebral aqueduct by tumours or congenital narrowing. This lead to
enlargement of the lateral and third ventricles but not the fourth ventricle.
3) Acute or Chronic: When to treat?
The acute hydrocephalus can develop in hours (after SAH due to aneurysm rupture)
and is often associated with acute rise in ICP, hence prompt intervention is required.
The chronic one may take years to develop (as in normal pressure hydrocephalus) and
the problem of intracranial hypertension isn’t the main concern.
Pathogenesis
The main problem in Hydrocephalus is the raised CSF pressure and hence the
intracranial pressure, whether globally (in all the ventricles and the subarachnoid
space and hence the whole brain) or locally at the CSF cisterns and recesses causing
pressure on specific brain parts. The raised ICP when severe enough and not treated
promptly will eventually lead to ischemic changes and death.
Clinical Features:
The clinical presentation of hydrocephalus relies to a good extent on the age of the
patient and whether it develops acutely or slowly.
Infants:
The opened cranial sutures will be reflected on the way babies with hydrocephalus
present clinically. The most common features are:
1) abnormally rapid head growth beyond the 99th centile (macrocephaly),
2) tense fontanelle
3) distended scalp veins
4) poor feeding/vomiting
5) poor head control
6) poor activity and mile stone development
7) splayed cranial sutures
8) sun-setting eyes
9) frontal bossing.
sun-setting eyes.
Children:
Headache/Neck pain.
Vomiting (early morning).
Blurred/Double vision.
Parinaud’s sign (upward gaze palsy): Limited upward
gaze leads to a preference for downward gaze in primary
position.
Slow mental development.
Stunted physical growth & sexual maturation.
Walking difficulty (spasticity).
Papilledema.
Adults:
Headache/Neck pain.
Blurred/Double vision/Papilledema.
Confusion/lethargy (loss of consciousness in acute obstructive hydrocephalus)
Nausea & vomiting.
Walking difficulty: Gait apraxia.
Seizures.
Urine incontinence.
Parinaud’s sign
NPH
* Idiopathic intracranial Hypertension (IIH):
Also called Pseudotumor Cerebri, it’s mostly in young
overweight women. It’s often characterized by a very high
CSF pressure, but without ventriculomegaly (the ventricles,
in contrast, are slit-like small). Patients commonly present
with acute vision changes (besides other features of raised
ICP). Without a prompt treatment, loss of vision had been
reported. The definitive treatment is a VP shunt.
IIH
Ex-Vacuo
Diagnosis:
Clinical Assessment:
This relies on a careful and detailed history taking that should include (besides the
pathognomonic clinical features of hydrocephalus) any family history and also history
of the pregnancy (for the congenital hydrocephalus). The clinical examination should
include a good cognitive functions assessment and a detailed neurological examination.
Clinical CSF pressure Testing:
In cases where the clinical and radiological investigations give equivocal data,
measuring the CSF pressure (ICP) could be the decisive tool for diagnosis. This could be
achieved by a lumbar puncture (if no obstruction on brain images, like in aneurysmal
SAH) or implanting an intracranial ICP measuring devices (ICP bolt or external
ventricular drain (EVD). If the pressure readings shown to be significantly high a
treatment plan would be decided.
Radiological Tests:
* Brain Ultrasound: this is mainly for congenital
hydrocephalus in newly born (or even antenatally before
birth) babies. It’s done through the widely opened anterior
fontanelle. Mostly regarded as an urgent tool to diagnose large ventricles in order to
start an immediate temporary CSF drainage (fontanelle tap).
* CT scan: this is the main tool for diagnosing hydrocephalus and to a good extent its
causative pathology.
Treatment
Hydrocephalus can be treated either medically or surgically.
The ultimate goal of treating hydrocephalus is to mitigate the symptoms and reverse
the neurologic deficit caused by the raised ICP (high CSF pressure) by resuming the
normal CSF circulation. This could be achieved through:
* Reducing CSF production.
* Removing the obstructive pathology.
* CSF diversion.
* Urgently draining out the CSF (lifesaving).
Medical Treatment:
No medical therapy can definitively treats hydrocephalus effectively. The commonly
used medications are:
1) Acetazolamide (carbonic anhydrase inhibitor) and 2) Furosemide may reduce the
rate of CSF production temporarily and hence control the ICP.
3) Dexamethasone: to compensate temporarily for the raised ICPc aused by the
associated brain edema of the rapidly enlarging ventricles or the one surrounding an
obstructing brain lesion.
Surgical treatments:
Urgent (temporary) treatments:
On certain circumstances where an acute hydrocephalus presents with clinical
evidence of very high ICP (loss of consciousness), an immediate intervention is
mandatory to save the patient’s life by draining out a volume of CSF to relief the high
pressure. This can be achieved by any of the following procedures:
1) Lumbar puncture (LP): Can only be done
in communicating hydrocephalus (as in
aneurysmal SAH where no blood is seen on CT
scan but with hydrocephalus). This can be
repeated according to the need. LP is
absolutely contraindicated in obstructive
hydrocephalus.
2) Fontanelle (Ventricular) tap: This procedure can only be done in infants with an
opened anterior fontanelle. The lateral ventricle can be approached percutaneously and
a good (and safe) amount of CSF can be aspirated to relieve the ICP pressure. It can also
be repeated on need. May only need some sedation in restless babies.
Fontanelle tap
External ventricular drain (EVD):
This procedure is done under GA, in which a catheter is percutaneously placed in the
lateral ventricle to drain the CSF into an external drainage bag that is hanged at a
certain height to control the amount of CSF to be drained out. It’s both therapeutic and
diagnostic as it’s used to measure the CSF pressure (ICP). Patients may later stop being
in need of it when their condition stabilizes, and the drain is taken out or they remain
dependant on a CSF drain where a permanent VP shunt is implanted instead.
EVD