Hydrocephalus is caused by an accumulation of cerebral spinal fluid in the ventricles of the brain. It can be congenital or acquired through events like hemorrhage or brain tumors. Shunt systems are commonly used to treat hydrocephalus by diverting CSF from the ventricles to the abdominal cavity through a series of catheters and a pressure-regulating valve. However, shunts have high failure rates, requiring multiple revision surgeries. Alternatives like endoscopic third ventriculostomy may help in some cases but have lower success rates than shunts, especially in infants.

1. HYDROCEPHALUS SHUNTS
ABBY JONES

2. WHAT IS
HYDROCEPHALUS?
• HYDROCEPHALUS IS CAUSED BY AN
ACCUMULATION OF CEREBRAL SPINAL FLUID
IN THE VENTRICLES. THE NORMAL FUNCTION
OF THE CSF IS TO CUSHION THE BRAIN AND
SPINAL CORD. IT ALSO CONSISTS OF
NUTRIENTS AND PROTEINS NEEDED TO
NOURISH THE BRAIN AND FOR THE BRAIN TO
CARRY OUT ITS NORMAL FUNCTION. CSF ACTS
AS A WASTE DISPOSAL MECHANISM AS IT
TRANSFERS WASTE AWAY FROM TISSUES.
WHEN MORE CSF IS BEING PRODUCED THAN
BEING ABSORBED, CSF ACCUMULATES AND
THE VENTRICLES EXPAND CAUSING PRESSURE
IN THE HEAD TO INCREASE. HYDROCEPHALUS
AFFECTS COGNITIVE, SOCIAL, AND PHYSICAL
DEVELOPMENT.

4. CAUSES
• HYDROCEPHALUS IS PREVALENT IN A WIDE AGE RANGE FROM BABIES TO
ADULTS. ONE TO TWO BABIES OUT OF EVERY THOUSAND ARE BORN WITH
HYDROCEPHALUS.
• HYDROCEPHALUS CAN BE CONGENITAL OR ACQUIRED:
• CONGENITAL: AQUEDUCTAL STENOSIS, NEURAL TUBE DEFECT, ARACHNOID CYST,
DANDY-WALKER SYNDROME, CHIARI MALFORMATION
• ACQUIRED: INTRAVENTRICULAR HEMORRHAGE, HEAD INJURY, MENINGITIS, BRAIN
TUMORS

5. CONGENITAL
HYDROCEPHALUS ACQUIRED HYDROCEPHALUS
• INTRAVENTRICULAR HEMORRHAGE- MOST FREQUENTLY
AFFECTS NEWBORNS. WHEN SMALL BLOOD VESSELS ALONGSIDE
THE VENTRICULAR LINING RUPTURE, BLOOD MAY BLOCK OR
SCAR THE VENTRICLES OR PLUG THE ARACHNOID VILLI, WHICH
ALLOW CSF TO BE ABSORBED.
• MENINGITIS- BACTERIAL OR VIRAL INFECTION CAN SCAR
MENINGES, WHICH CAN THEN BLOCK THE CSF’S FLOW
THROUGH THE VENTRICLES.
• HEAD INJURY- DAMAGED VESSELS, TISSUES, OR NERVES CAN
CAUSE BLOOD TO ENTER THE CSF PATHWAY LEADING TO
INFLAMMATION. THE PATHWAY CAN THEN BE BLOCKED BY
SCARRING OF THE MENINGES.
• BRAIN TUMORS- AS A TUMOR GROWS, IT MAY FILL OR
COMPRESS THE FOURTH VENTRICLE, BLOCKING THE FLOW OF
CSF.
• AQUEDUCTAL STENOSIS – THE MOST COMMON CAUSE OF
CONGENITAL HYDROCEPHALUS. THIS OCCURS WHEN THE LONG,
NARROW PASSAGEWAY BETWEEN THE THIRD AND FOURTH
VENTRICLES (THE AQUEDUCT OF SYLVIUS) IS NARROWED OR
BLOCKED, PERHAPS BECAUSE OF INFECTION, HEMORRHAGE, OR A
TUMOR. FLUID ACCUMULATES “UPSTREAM” FROM THE
OBSTRUCTION.
• ARACHNOID CYSTS- FLUID IS TRAPPED BY THE CYSTS WHICH MAY
BLOCK THE CSF PATHWAYS, CAUSING HYDROCEPHALUS.
• NEURAL TUBE DEFECT- PART OF THE CEREBELLUM AND THE FOURTH
VENTRICLE PUSH DOWNWARD THROUGH THE OPENING AT THE BASE
OF THE SKULL INTO THE SPINAL CORD AREA, BLOCKING CSF FLOW
OUT OF THE FOURTH VENTRICLE AND CAUSING HYDROCEPHALUS.
• DANDY-WALKER SYNDROME- THE FOURTH VENTRICLE BECOMES
ENLARGED BECAUSE ITS OUTLETS ARE PARTLY OR COMPLETELY
CLOSED AND PART OF THE CEREBELLUM FAILS TO DEVELOP.
• CHIARI MALFORMATIONS- THE LOWEST PORTION OF THE BRAIN IS
DISPLACED AND IS LOWER THAN NORMAL PUSHING DOWN INTO THE
SPINAL COLUMN.

6. SHUNTS
• THE SHUNT SYSTEM CAN BE USED WHEN TREATING
HYDROCEPHALUS AND IT IS THE MOST COMMON SURGERY
PERFORMED BY PEDIATRIC NEUROSURGEONS IN THE US.
• THE SHUNT DIVERTS CEREBRAL SPINAL FLUID TO DIFFERENT
REGIONS OF THE BODY TO PREVENT ACCUMULATION OF CFS IN
THE VENTRICLES. THE CSF IS TYPICALLY DIVERTED TO THE
ABDOMINAL CAVITY (CAN BE THE HEART) WHERE IT IS THEN
ABSORBED.
• THERE IS A VALVE THAT REGULATES THE FLUID IN THE VENTRICLES
TO KEEP IT AT A NORMAL PRESSURE. THESE VALVES ACT LIKE
SWITCHES AS THEY OPEN AND CLOSE BASED ON THE DIFFERENTIAL
PRESSURE. THESE VALVES CAN BE SET AT A FIXED PRESSURE OR A
MODIFIABLE PRESSURE. THERE ARE NON-INVASIVE WAYS TO
ADJUST THE DIFFERENTIAL PRESSURE INCLUDING USING A MAGNET
OR SOME ARE SELF-ADJUSTING TO REGULATE FLOW.
• WITHIN THE PEDIATRIC POPULATION, 50% OF SHUNTS FAIL WITHIN
TWO YEARS OF INSTALLMENT. WITHIN THESE COMPLICATIONS,
THERE CAN BE AN OVER DRAINAGE, INFECTIONS, OBSTRUCTIONS
OR AN ELEVATED PRESSURE. WITH THIS BEING SAID, TYPICALLY
MULTIPLE NEUROLOGICAL OPERATIONS ARE NECESSARY. IF THESE
SHUNTS ARE LEFT UNMONITORED, CSF CAN ACCUMULATE, WHICH
CAN LEAD TO INTRACRANIAL PRESSURE LEADING TO AN
INTRACRANIAL HEMATOMA, CEREBRAL EDEMA, OR CRUSHED
BRAIN TISSUE.

8. SHUNT COMPONENTS
• THE SHUNTS ARE GENERALLY MADE UP OF 3 PARTS:
• INFLOW CATHETER
• THE INFLOW CATHETER DRAINS THE FLUID FROM THE VENTRICLES OR SUBARACHNOID SPACE
• VALVE
• THE VALVE MONITORS THE DIFFERENTIAL PRESSURES AND THE FLOW AND CAN BE FOUND ON TOP OF THE HEAD OR
RIGHT BEHIND THE EAR.
• THE VALVE CAN HAVE A FIXED PRESSURE OR BE ADJUSTABLE FROM THE OUTSIDE.
• OUTFLOW CATHETER
• THE OUTFLOW CATHETER DIVERTS THE CEREBRAL SPINAL FLUID FROM THE VALVE TO THE ABDOMINAL CAVITY OR
HEART.
• EACH SHUNT TYPICALLY HAS A SIPHON CONTROL DEVICE WHICH PREVENTS OVER DRAINAGE DUE
TO GRAVITY.

9. SHUNT ROUTES
• THE ROUTE AT WHICH THE CSF IS TAKEN TO
DRAIN IS BASED ON THE TYPE AND LOCATION
OF THE BLOCKAGE THAT IS CAUSING THE
HYDROCEPHALUS.
• VENTRICULO-PERITONEAL SHUNT- PERITONEAL
CAVITY
• VENTRICULO-ATRIAL SHUNT- RIGHT ATRIUM
OF THE HEART
• VENTRICULO-PLEURAL SHUNT- PLEURAL
CAVITY
• VENTRICULO-CISTERNAL SHUNT- CISTERNA
MAGNA

10. SHUNTS

11. SHUNT REMOVAL
• VERY RARE, BUT NOT UNHEARD OF
• HARD FOR DOCTORS TO DISCERN WHEN THE PATIENT BECOMES SHUNT
INDEPENDENT AND IF THE PATIENT WOULD BE ABLE TO SURVIVE WITHOUT THE
SHUNT
• TOO GREAT OF A RISK

12. ALTERNATIVES
• THERE IS AN ALTERNATIVE SURGERY FOR INFANTS TO UNDERGO TO TREAT
HYDROCEPHALUS WHICH IS CALLED ENDOSCOPIC THIRD VENTRICULOSTOMY WITH
CHOROID PLEXUS CAUTERIZATION. THIS PROCEDURE IS DONE BY PUNCTURING A
MEMBRANE IN THE FLOOR OF THE THIRD VENTRICLE AS WELL AS USING A TOOL TO
BURN/CAUTERIZE TISSUE FROM THE CHOROID PLEXUS, WHICH IS A GROUP OF
VESSELS THAT MAKE UP THE VENTRICLES WHERE CFS IS MADE. THIS PROCEDURE
SHOULD ALLOW CSF TO FLOW NORMALLY WITHIN THE CAVITIES OF THE BRAIN.
• THE RATES OF SUCCESS ARE A LOT LOWER FOR THIS PROCEDURE IN INFANTS, SO
THAT IS WHY IT IS NOT AS COMMON OF A PROCEDURE AS THE IMPLANTATION OF A
SHUNT. THE SUCCESS RATE IS REALLY DEPENDENT ON THE AGE OF THE PATIENT,
THE ETIOLOGY OF THE HYDROCEPHALUS, AND WHETHER THERE WILL BE SCARRING
IN THE FLUID SPACE IN THE VENTRICLE.

13. RESOURCES
• HTTP://WWW.HYDROASSOC.ORG/SHUNT-SYSTEMS/
• HTTPS://WWW.NCBI.NLM.NIH.GOV/PUBMED/15838593