Hydrocephalous, shunting & shunt systems

Hydrocephalous, shunting & shunt systems

Dr Mukhtar

PG Neurosurgery

HMC Peshawar

Aims & Objectives:

• Definition

• Key Introductory points

• Epidemiology

• Types & Classification

• Special forms of hydrocephalous

• Treatment options

• Risks & complications of intervention

Definition

Hydrocephalous

• The term hydrocephalus is derived from the Greek: hydro meaning water

and kefale meaning skull

• A disturbance of cerebrospinal fluid formation, flow, or absorption, leading

to an increase in volume occupied by this fluid in the central nervous

system (CNS).

• This condition could also be termed a hydrodynamic CSF disorder.

• Net CSF production = 0.35 mL/min (500 mL/day),

• CSF turnover rate of approximately three to four times per day

Introduction

Introduction

• Its management has been the most common problem facing

neurosurgeons who treat children

• 40% to 50% of the surgical interventions and clinic visits

• Evidence suggests that the incidence of paediatric

hydrocephalus is decreasing

• Decline in the number of children with spina bifida

o Experience with managing very preterm infants

o Despite these trends, the burden of this illness remains large

• Each year ; 40,000 admissions, approximately 400,000

hospital days, and between $1.4 billion and $2 billion in

hospital charges for paediatric hydrocephalus

• The clinical manifestations are those of raised intracranial pressure, which

vary with age

• Gradually increasing head circumference.

importance of head measurement

• Unusual irritability

• Excessive vomiting with no other explanation

• Eye movement abnormalities, especially downward deviation of

the eyes (“sunsetting”), or sixth nerve paresis

• As a child gets older and the sutures fuse, the presentation differs.

• Head size can still cross percentiles, but very slowly

• so changes in percentile growth become less helpful

• In these children, the presentation usually includes headache and

eventually nausea and vomiting

• Dementia, ataxia, and incontinence seen in adult NPH are not

part of the pediatric presentation

• Papilledema may occur in long-standing cases if the onset is after

suture closure

• A child whose hydrocephalus begins while the sutures are open but presents

later usually does not have papilledema but does have a very large head

• Presentation beyond the first few years of life usually indicates

hydrocephalus secondary to an acquired disorder, such as

tumour, head injury, or meningitis.

• The decision to treat a child with ventriculomegaly can be

very difficult

• Once a shunt has been implanted, it is very difficult to determine whether it

can be removed

• The use of adjunctive measures, such as intracranial

pressure monitoring, magnetic resonance spectroscopy, and

the magnetic resonance measurement of cerebral blood flow,

has been reported in difficult cases, but the decision to treat

is usually based on observation over time.

• Progressively increasing head size, enlarging ventricles, or

progressive symptoms are the most common measures and

form the most solid basis for making the decision to treat.

Epidemiology

• Estimated prevalence: 1-1.5%.

• Incidence of congenital hydrocephalus is ≈ 0.9-3/1000 births (reported range

from 0.2 to 3.5/1000 births

• Incidence of acquired hydrocephalus is unknown

• Generally, incidence is equal in males and females

• Bimodal age curve

• Adult hydrocephalus represents approximately 40% of total cases of

hydrocephalus

Types & Classifications

• Obstructive (non-communicating):

• block proximal to the arachnoid granulations. On CT or MRI: enlargement

of ventricles proximal to block

• Communicating (non-obstructive):

• CSF circulation blocked at level of arachnoid granulations

Types of Communicating hydrocephalous

SPECIAL FORMS

1. conditions that are not actually hydrocephalus “pseudohydrocephalus”

a) hydrocephalus ex vacuo:

b) otitic hydrocephalus:

c) external hydrocephalus:

d) hydranencephaly:

2. normal pressure hydrocephalus (NPH)

3. entrapped fourth ventricle:

4. arrested hydrocephalus

Etiologies

ETIOLOGIES

1. Congenital

i. Chiari Type 2 malformation

ii. Chiari Type 1 malformation

iii. primary aqueductal stenosis

iv. secondary aqueductal gliosis

v. Dandy Walker malformation

vi. X-linked inherited disorder

2) Acquiredi. infectious

• post-meningitis

• cysticercosis

ii. post-haemorrhagic

• post-SAH

• post-IVH

iii. secondary to masses

• non neoplastic

• neoplastic

iv. post-op

v. Neurosarcoidosis

vi. “constitutional ventriculomegaly”: asymptomatic

vii. associated with spinal tumours

Special forms of hydrocephalous

EXTERNAL HYDROCEPHALUS

• Key concepts:

• enlarged subarachnoid spaces over the frontal poles in the first year of

life

• ventricles are normal or minimally enlarged

• may be distinguished from subdural hematoma by the “cortical vein

sign”

• usually resolves spontaneously by 2 years of age

• Differential diagnosis:

• EH must be distinguished from symptomatic chronic extra-axial fluid collections (or

chronic subdural hematoma), which may be accompanied by seizures, vomiting,

headache and may be the result of child abuse.

• With EH, MRI or CT may demonstrate cortical veins extending from the surface of

the brain to the inner table of the skull coursing through the fluid collection

(“cortical vein sign”), whereas the collections in subdural hematomas compress the

subarachnoid space which apposes the veins to the surface to the brain

• Treatment:

• EH usually compensates by 12-18 months age without shunting.

• Follow up serial ultrasound and/or CT to rule out abnormal ventricular

enlargement.

• Due to increased risk for positional molding, parents may need to periodically

reposition the head while the child is sleeping.

• A shunt may rarely be indicated when the collections are bloody (consider the

possibility of child abuse) or for cosmetic reasons for severe macrocrania or

frontal bossing.

X-LINKED HYDROCEPHALUS

• Inherited hydrocephalus (HCP) with phenotypic expression in males passed on through carrier mothers who are phenotypically normal. Classical phenotypic expression will skip single generations.

• Incidence: 1/25,000 to 1/60,000.

• Prevalence: ≈ 2 cases per 100 cases of hydrocephalus.

• Gene located on Xq28

• L1 syndromes

• Classical syndromes include;

• CRASH (corpus callosum hypoplasia, retardation, adducted thumbs (clasp

thumbs), spastic paralysis, Hydrocephalous),

• MSAS (mental handicap, aphasia, shuffling gate, adducted thumbs),

• HSAS (Hydrocephalous with stenosis of the aqueduct of Sylvius).

• Spectrum of disease also includes x-linked agenesis of the corpus callosum

and spastic paraparesis type 1.

• Recent delineations:

• mild L1 syndrome: adducted thumbs, spastic paralysis, hypoplasia of Corpus

Callosum

• severe L1 syndrome: as in mild L1 syndrome plus anterior cerebellar vermis

hypoplasia, large massa intermedia, enlarged quadrigeminal plate, rippled

ventricular wall following VP shunt placement (pathognomonic for X-linked

Hydrocephalous).

• Profound mental retardation in virtually all cases

• Radiographic findings if severe L1:

• severe symmetric HCP with predominant posterior horn dilation

• hypoplastic Corpus Callosum/Agenesis of Corpus Callosum

• hypoplastic anterior cerebellar vermis

• large massa intermedia

• large quadrigeminal plate

• rippled ventricular wall following VP shunt placement (pathognomonic)

• Treatment:

• no intervention demonstrates improvement in retardation status in observational papers.

• VP shunt:

• main purpose is management of head size. Does not improve neurologic outcome

• prenatal U/S: early (≈ 20-24 weeks gestational age) with frequent repeat scan in known carrier mothers. May allow for medically indicated termination early on

• male infants with ≥ 2 clinical/radiographic signs should undergo genetic testing for L1CAM mutation detection for future pregnancy counselling

ARRESTED HYDROCEPHALUS

• Some patients with hydrocephalus reach a state in which ventricular size remains unchanged in the absence of a shunt or in the presence of a non-functioning one

• The exact definition of this term is not generally agreed upon, and some use

the term compensated hydrocephalus interchangeably.

• Arrested hydrocephalus satisfies the following criteria in the absence of a CSF

shunt:

• near normal ventricular size

• normal head growth curve

• continued psychomotor development

Shunt independence

• Not universally accepted concept

• May occur in communicating hydrocephalous

• Patients must be followed closely

• Increased chance of sudden death due to asymptomatic increased ICP

ENTRAPPED FOURTH VENTRICLE

• 4th ventricle that neither communicates with the 3rd ventricle nor with the basal cisterns

• Usually seen with chronic shunting of the lateral ventricles

• Possibly as a result of adhesions forming from prolonged apposition of the ependymal lining of the aqueduct

• Occurs in 2-3% of shunted patients. May also occur in Dandy Walker malformation

• The choroid plexus of the 4th ventricle continues to produce CSF which enlarges the ventricle when there is 4th ventricular outlet obstruction or obstruction at the level of the arachnoid granulations

• Presentation:

• Headache

• Lower CN palsies

• Bilateral abducens palsy

• Ataxia

• Reduced level of consciousness

• Nausea/vomiting

Treatment

• Insertion of shunt from below the tonsils

• Passing through a cerebellar hemisphere

• Ventriculocisternal shunt

• LP shunt

• Radiologic Criteria

• the size of both temporal horns (TH) is ≥ 2 mm in width, and the sylvian & interhemispheric fissures and cerebral sulci are not visible

• OR

• both temporal horns are ≥ 2 mm, and the ratio FH/ID ≥ O.5 (where FH is the largest width of the frontal horns, and ID is the internal diameter from inner-table to inner-table at this level)

• Other features suggestive of hydrocephalus:

• ballooning of frontal horns of lateral ventricles (“Mickey Mouse” ventricles) and/or 3rd ventricle (the 3rd ventricle should normally be slit-like)

• periventricular low density on CT, or periventricular high intensity signal on T2WI on MRI suggesting transependymal absorption of CSF

Hydrocephalous & paediatric tumours

• Common in children due to propensity of tumours towards posterior fossa

• Shunting before tumour removal is no longer a favoured procedure

• Third ventriculostomy before tumour removal reduces risk

• Canadian preoperative prediction rule for development of hydrocephalous

after tumour surgery

DIFFERENTIAL

• Conditions that may mimic hydrocephalous but are not due to inadequate CSF

absorption include:

• atrophy: sometimes referred to as “hydrocephalus ex vacuo”

• hydranencephaly:

• developmental anomalies where the ventricles appear enlarged:

• agenesis of the corpus callosum:

• septo-optic dysplasia

Clinical:

• In younger infants:• Skull enlargement > facial growth

• Irritability, poor head control, vomiting

• Fontanelle

• Scalp veins

• McEwen's sign

• 6th nerve palsy

• Setting sun sign/Perinaud’s syndrome

• Hyperactive reflexes

• Irregular respiration, splaying of cranial sutures

• In Older patients (including older children)

• In addition to the above; papilloedema, headache, vomiting, gait changes, abducens palsy

Chronic hydrocephalous

• Beaten copper skull

• 3rd ventricle herniation into the sella

• Erosion of the sella

• Less prominent temporal horns

• Macrocrania

• Corpus callosum atrophy

• Suture diastasis, delayed fontanelle closure & failure to thrive in infants

Occipitofrontal circumference

• Technique:

• Measure around forehead & occiput three consecutive times & record the largest

value. Plot against the OFC percentile curves.

• Following findings may prompt further workup:

• Upward deviation (crossing curves)

• Continued head growth > 1.25 cm/week

• OFC > 2 SD above normal

• OFC > body proportion in length & width even if within normal limits for age

• As a rule of thumb; OFC = Crown Rump Length

OFC for premature infants as a function of gestational age

Head circumference, weight and length

Treatment

• Medical:

• Hydrocephalous remains a surgically treated illness

• Acetazolamide as a temporary therapy (25mg/Kg/day in TDS)

• Premature infants with IVH

• Simultaneous use of furosemide (1mg/kg/day in TDS)

• Provide treatment to counteract acidosis

• Serial electrolyte measurement

• Maintain HCO3 > 18 mEq/L

• Potassium supplementation

• Weekly head Ultrasound or CT to determine the need for surgical intervention

• Maintain therapy for 6 months, then taper over 3 to 4 weeks

• Spinal taps:• LPs can only be used for communicating hydrocephalous

• Shunting if CSF reabsorption does not resume

• Surgical Intervention:• Goals:

• Optimum neurologic function & good cosmetic result instead of normal sized ventricles

• Options:

• Choroid plexectomy:

• Opening stenosed sylvian aqueduct:

• Third ventriculostomy:

• Shunting:

• Third ventriculostomy:

• Overall success rate 56% (60—94% for nontumoural aqueductal

stenosis)

• Indications:

• Obstructive hydrocephalous

• One option in managing repeated shunt infections

• Patients who develop subdural haematoma after shunting

• Slit ventricle syndrome following shunting

• Contraindications:

• Communicating hydrocephalous

• Presence of any factor with low success for ventriculostomy

• Complications:

• Hypothalamic injury

• 3rd & 6th nerve palsy

• Uncontrollable bleeding

• Cardiac arrest & basilar artery aneurysm

• Shunts:

A. Types of Shunts:

1. Shunt Types By Categorya. VP Shunt

• Most commonly used shunt in modern era

• Lateral ventricle is the usual proximal location

• Intraperitoneal pressure

b) Ventriculo-atrial shunt (Vascular shunt)

• Through jugular veins to sup. Vena cava

• Treatment of choice in abdominal abnormalities

c) Torkildsen shunt:

• Shunting ventricle to cisternal space

• Rarely used

• Effective only in acquired obstructive hydrocephalous

d) Miscellaneous:

• Distal projections at different locations

• Pleural space:

• Gall bladder:

• Ureter/Urinary Bladder:

e) Lumboperitoneal shunt:

• Only for communicating hydrocephalous

f) Cyst/Subdural-Peritoneal shunt:

• Draining arachnoid cyst/subdural hygroma

cavity

Complications/Disadvantages:

• The likelihood of shunt failure is 40% in the first year after shunt implantation

• Most common presentation of a shunt failure is typical hydrocephalic presentation

• Multiple shunt failures in a patient usually has the identical picture of presentation

• Patients with MMC develops frequent UTIs and present similar to shunt failure

• Diagnosis & treatment of UTIs in these patients is rewarding

• Ventricle size reduces at the end of the first post-op year

Slit Ventricles Syndrome

• The lateral ventricles collapse secondary to overshunting or remain at a

fixed size subependymal gliosis

• Intermittent or complete shunt malfunction

• Raised ICP without ventricular enlargement,

• unresponsive ventricles

• Progressive neurological deterioration secondary to raised ICP may require

subtemporal decompression

• Third ventriculostomy possible during periods of relative ventricular

dilation

i. General:a. Obstruction:

b. Disconnection:

c. Infection:

d. Erosion through Skin:

e. Seizures:

f. Metastatic route:

g. Silicone allergy:

ii. With VP Shunt:a. Inguinal hernia: 17% incidence

b. Needs lengthening with age:

c. Obstruction:

d. Malposition of tip:

e. Peritonitis with shunt infection:

f. Hydrocele:

g. CSF ascites:

h. Migration into scrotum/bowel/stomach:

i. Intestinal obstruction:

j. Volvulus:

k. Overshunting:

iii. VA shunt:

• Requires repeated lengthening:

• High risk of infection/septicaemia:

• Risk of retrograde flow of blood: in case of valve malfunction

(rare)

• Shunt embolus:

• Vascular complications: perforation, thrombophlebitis,

pulmonary micro-emboli

iv. LP Shunt:

• Laminectomy incurs 15% chance of scoliosis

• Progressive cerebellar tonsillar herniation (up to 70%)

• Slit ventricle syndrome:

• Overshunting is harder to control:

• Difficult proximal end revision (if required):

• Lumber radiculopathy:

• CSF leak:

• Difficult pressure regulation:

• Bilateral 6th, 7th, nerve dysfunction due to overshunting:

• High incidence of arachnoiditis & adhesions:

• CONCLUSION

• Hydrocephalus remains a rich and rewarding subject area in which successful surgical management requires meticulous clinical assessment, direct physiologic testing, and careful interpretation of the underlying pathophysiologic processes. It is likely that this field will continue to develop with the evolution of neuroimaging tools and novel shunt technology.

Thanks!

CSF drainage devices

i. Fixed differential pressure valves

ii. Adjustable differential pressure valves

iii. Flow-regulating valves

iv. Accessory devices Antisiphon devices

• Valves designs:i. Silicone membrane

ii. Ball-on-spring

iii. Miter valve

iv. Proximal or distal slit valves

v. Moving diaphragm