HYDROCEPHALUS

EVALUATION & MANAGEMENT

Anatomy and PhysiologyVentricular System & CSF

• 80% from the choroid plexus• Interstitial spaces Production• Ependymal lining• Dura of nerve root sheaths

CHOROID PLEXUS

Anatomy and PhysiologyCSF

• Absorbtion: - Primarily by the Arachnoid villi

• Rate of production- 0.3ml/min or approx 450ml/24 hrs

• Turnover: 3 times/day

CSF CIRCULATION

• Lateral ventricles – Foramen of Monro

• 3rd Ventricle – Cerebral Acqueduct

• 4th Ventricle – F. of Magendie & Luschka

• Perimedullary and Perispinal subarachnoid spaces – upward to

the basal cistern

• Superior and lateral surfaces of the cerebral hemispheres

CSF Flow path

CSF PRESSURE

• The CSF volume and pressure are

maintained every minute by the

systemic circulation

• CSF pressure is in equilibrium

with capillary pressure (arteriolar

tone)

• Hypoventilation – ↑ in blood PCO2 – ↓ pH & ↓ arteriolar resistance – ↑ cerebral blood flow – ↑ CSF pressure

• Hyperventilation has the

opposite effect

CSF PRESSURE

• Normal adult intracranial pressure 2-

8 mmHg

• Up to 16 mmHg are considered

normal

• ICP higher than 40 mmHg or lower BP

may combine to cause ischemic

damage to the brain

Definition

• An increase in CSF volume in an enlarged ventricular system resulting

- primarily from decreased absorbtion - rarely b’coz of increased production• Prevalance: 1-1.5%• Incidence: 0.3-3.5%- Upto 20% after SAH- 1% after meningitis

Definition

• Results in ventricular enlargement• Lat ventricles - frontal and occipital horns• Volumes decrease in cerebral sulci, fissures

and cisterns

Classification• Functional

• Clinical

• Age wise

• Pathological

• ICP/ R-out

• Special Types

Functional

• Communicating:- Block at the level of the arachnoid

granulations

• Non-communicating:- Block proximal to the arachnoid granulations

Clinical

• High pressure hydrocephalus - Acute - Chronic• Normal pressure hydrocephalus

• Arrested hydrocephalus

• Hydrocephalus ex vacuo

Age wise

• Paediatric• Juvenile/Adult

Pathological

• Congenital1. Chiari type 1 malformation2. Chiari type 2 malformation and/or

Meningimyelocele3. Primary aqueductal stenosis4. Secondary aqueductal gliosis ( germinal matrix

hge)5. Dandy Walker malformation6. Rare X- linked disorder

Pathological• Acquired1. Infectious - Post meningitic - Granuloma - Cysticercosis - Abscess

2. Post haemorrhagic - SAH - IVH - Trauma

Pathological

• Acquired 3. Secondary to mass effect - Non neoplastic - Neoplastic - Choroid plexus papilloma - Post operative - Neurosarcoidosis - Assoc with spinal tumours - Constitutional ventriculomegaly

ICP

• High Pressure - Monitored ICP > 15mmhg - B waves - R out increased

• Normal Pressure - Monitored ICP < 15mmHg - R out increased

Special Types

HYYDROCEPHALUS EX VACUO• enlargement of the ventricles due to loss of

cerebral tissue (cerebral atrophy)• usually as a function of normal ageing• Accelerated by Alzheimer's disease,

Creutzfeldt-Jakob, Alcoholism

Special TypesEXTERNAL HYDROCEPHALUS• 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

• Etiology :• Unclear • Defect in CSF resorption is postulated• External hydrocephalus (EH) may be a variant of communicating

hydrocephalus

Special Types

ARRESTED HYDROCEPHALUS• Compensated hydrocephalus interchangeably• There is no progression or deleterious

sequelae requiring CSF shunting • Criteriae in the absence of a CSF shunt: - Near normal ventricular size - Normal head growth curve - Continued psychomotor development

Special Types

OTITIC HYDROCEPHALUS• Obsolete term• Describes the increased ICP in patients with

otitis media

Special Types

HYDRANENCEPHAL Y • A post-neurulation defect• Total or near-total absence ofthe cerebrum • Intact cranial vault and meninges• Intracranial cavity being filled with CSF• There is usually progressive macrocrania• Most commonly cited cause : B/L ICA infarcts• Infection - Congenital or neonatal herpes - Toxoplasmosis - Equine virus

Special Types

ENTRAPPED FOURTH VENTRICLE • AKA isolated fourth ventricle, • 3rd Ventricle X 4th ventricle X Foramina of

Luschka or Magendie- Post-infectious hydrocephalus( fungal) - Repeated shunt infections• Choroid plexus of the 4th ventricle : produces

CSF which enlarges the ventricle

Special Types

NPH• Classic triad: - Dementia - Gait disturbance - Urinary incontinence • Communicating hydrocephalus on CT or MRI • Normal pressure on random LP • Symptoms remediable with CSF shunting

NPH

• Etiology- Post SAH - Post-traumatic - Post-meningitic- Following posterior fossa surgery - Tumors including carcinomatous meningitis - Also seen in -15% of patients with Alzheimer's disease - Deficiency of the arachnoid granulations- Aqueductal stenosis

CLINICAL FEATURES

INFANCY• Head grows at alarming rate with hydrocephalus.

– First sign: Bulging pulsatile fontanelles

– Tense, non-pulsatile anterior fontanelle

– Dilated scalp veins

– Thin skull bones with separated sutures

• Cracked pot sounds on percussion : Mc Ewans

sign

INFANCY

• Depressed eyes or SUN SET sign

– Eyes downward with sclera visible

above

• Pupils sluggish with unequal response to

light

• Irritability, lethargy, feeds poorly,

• Changes in Level of Consciousness

• Arching of back (Opisthotonus)

• Lower extremity spasticity

INFANCY

• Brain Stem Compression

– Swallowing difficulties, Stridor, Apnea, Aspiration,

Respiratory difficulties

• Lower Brainstem Dysfunction

– Difficulty in sucking and feeding

– High-pitched shrill cry

INFANCY

• Emesis, Somnolence, Seizures, and Cardio Pulmonary Distress

• Severely affected infants may not survive neonatal period

CHILDHOOD

• Headache on awakening, improvement following emesis or sitting

• Papilledema, strabismus, and Extrapyramidal signs, ataxia

• Irritability, Lethargy, Apathy, Confusion, and often incoherent

SYMPTOMS AND SIGNS

• Irritability

• Poor feeding

• Headache

• Nausea, vomiting

• Diplopia

• Visual impairment

• Dementia

• Incontinence

• Gait disturbances

• Accelerated head growth

• Bulging fontanelles

• Forced down gaze

• Developmental delay

• Exotropia

• Papilledema

• Posturing

• Bradycardia

• Apnea / Death

Evaluation

• Clinical• CT• MRI• ICP• R (out)• Isotope cisternography

Clinical

• Occipito Frontal Circumference- OFC of a normal infant = Distance from Crown to

Rump• Indicators:- Crossing curves- Head growth > 1.25cm/wk- OFC approaching 2 SD above normal- Out of proportion with body length or weight, even

if normal for age

CT CRITERIAE

CT CRITERIAE

<40% - Normal

FH/ID 40-50% - Borderline

> 50% - Hydrocephalus

Evan’s Index

CT/ MRI FindingsAcute Hydrocephalus

• Preferential AP dilatation of the Temporal Horns > 2mm

• Ballooning of the Frontal Horns and 3rd Ventricles (Mickey Mouse sign)

• Periventricular interstitial edema• Flattening of the Inter-hemispheric and Sylvian

fissures• Upward bowing of corpus callosum on sagittal MRI• 4th Ventricle normal in size

CT/ MRI FindingsChronic Hydrocephalus

• Temporal horns may be less prominent• 3rd ventricle may herniate into Sella Turcica• Erosion of Sella• Corpus callosum atrophy• Irreversible white matter demyelination

R (Out)

• Assesses the degree of blockage to CSF absorbtion back into the blood stream

• Simultaneous infusion of artificial CSF and measurement of ICP

• Spinal subarachnoid space cannulated• ICP monitor inserted• Calculated resistance value high

Better response to surgery

Isotope Cisternography

• Radioisotope injected into Lumbar Sub-arachnoid space

• Absorbtion of CSF monitored periodically over 96 hrs

• Positive cisternogram does not predict response to shunt surgery

TREATMENT OF HYDROCEPHALUS

THERAPEUTIC MANAGEMENT

• Goals:

– Relieve hydrocephaly

– Treat complications

– Manage psychomotor problems

– Usually surgical

Drug Therapy

• The choroid plexus shares many ion pumps and enzyme

systems with renal tubular epithelium

– Acetazolamide:

Start @ 25mg/kg/day PO TID

Increase @ 25mg/kg/day to 100mg/kg/day

Simultaneously start Frusemide @1mg/kg/day

Drug Therapy

To counteract acidosis: • tricitrate (Polycitra®) 4 ml/kg/day divided QID (each ml is

equivalent to 2 mEq of bicarbonate, and contains 1 mEq K+ and 1 mEq Na+)

• measure serial electrolytes, and adjust dosage to maintain serum HC03 > 18 mEqIL .

• change to Polycitra-K® (2 mEq K+ per ml, no Na+) ifserum potassium becomes low

• or to sodium bicarbonate if serum sodium becomes low

Drug Therapy

• Watch for electrolyte imbalance and acetazolamide side effects:

- Lethargy - tachypnea- diarrhea - paresthesias • Perform weekly CT scan and insert ventricular shunt

if progressive ventriculomegaly occurs. • Otherwise, maintain therapy for a 6 month trial, then

taper dosage over 2-4 weeks

Spinal Taps

• HCP after IVH may be transient• Serial taps (ventricular or LP) may temporize until

resorption resumes • LPs only for Communicating HCP• No reabsorption when the protein content of the CSF

is < 100 mg/dl

Spontaneous resorption unlikely

SHUNTING

Surgical Modalities

1. Choroid Plexectomy2. 3rd Ventriculostomy3. Shunts

Choroid Plexectomy

• Described by Dandy in 1918 for communicating hydrocephalus

• May reduce the rate but does not totally halt CSF production

• Open surgery associated with a high mortality rate

• Endoscopic choroid plexus coagulation - 1910

3rd Ventriculostomy

• Resurgence of interest in third ventriculostomy (TV) with the recent increased use ofventriculoscopic surgery

• Indications: - Obstructive HCP. - Mgt of shunt infection - Subdural hematomas after shunting - Slit ventricle syndrome

3rd Ventriculostomy

• Contraindications: - Communicating Hydrocepalus - Tumor - Previous shunt - Previous SAH - Previous whole brain radiation - Significant adhesions visible when perforating

through the floor of the 3rd ventricle at the time of performance of TV

3rd Ventriculostomy

• Complications- Hypothalamic injury - Transient 3rd and 6th nerve palsies - Uncontrollable bleeding - Cardiac arrest - Traumatic basilar artery aneurysm

Shunts

Types of Shunt

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

hydrocephalus

d. Miscellaneous:»Pleural space»Gall bladder»Ureter/Urinary Bladder

e. Lumbo-peritoneal shunt:

»Only for communicating hydrocephalous

f. Cyst/Subdural-Peritoneal shunt:

»Draining arachnoid cyst/subdural

hygroma cavity

SHUNT MATERIALS

• Shunts are composed of Silastic material made from silicone.

VP SHUNT

• Shunt systems include three components: – Ventricular catheter

– One way valve

– Distal catheter

• The ventricular catheter – Straight piece of tube

– Closed on the proximal end

– With multiple holes upto 2cm for the entry of CSF

VA Shunt

• The VA shunt

– Must be accurately located

– Requires frequent revisions

– Distal end position to be maintained

– Infection may be more serious

VP SHUNT

• If both the VPS & VAS do not function to absorb CSF the shunt have to

placed in the pleural space

POST-OP CARE

• Observe for signs of Increased ICP

– Assessment pupil size

– Cushing’s Reflex

– Abdominal distention

• due to CSF peritonitis or post-op ileus due to catheter placement.

Complicationsi. General:

a. Obstructionb. Disconnectionc. Infectiond. Erosion through Skine. Seizuresf. Metastatic routeg. Silicone allergy

• VP Shunt- Inguinal hernia- Hydrocele- Peritonitis- Intestinal Obstruction- Volvulus- Migration of tip to scrotum/ bowel/ stomach- Malposition of tip- Over-shunting- Needs frequent length adjustment

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

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