Hydrocephalus
Hydrocephalus comes from the Greek: "hydro" meanswater, "cephalus" means head. Hydrocephalus is an abnormalaccumulation of cerebrospinal fluid (CSF) within cavities called ventriclesinside the brain. CSF is produced in the ventricles, circulates through theventricular system and is absorbed into the bloodstream. CSF is in constantcirculation and has many important functions. It surrounds the brain and spinalcord and acts as a protective cushion against injury. CSF contains nutrientsand proteins necessary for the nourishment and normal function of the brain. Italso carries waste products away from surrounding tissues. Hydrocephalus occurswhen there is an imbalance between the amount of CSF that is produced and therate at which it is absorbed. As the CSF builds up, it causes the ventricles toenlarge and the pressure inside the head to increase.
CSF Pathways
The Choroid plexus is the mainsource of CSF. The CSF formed in the lateral ventricles gains access to thethird ventricle through the paired foramina of Munro. From there through theAqueduct of Sylvius it enters the fourth ventricle from which is exits throughthe foramina of Luschka and Magendie. Part of it flows down into the spinalsubarachnoid space. The bulk flows over the hemispheres and the subarachnoidpathway to be absorbed by the arachnoid villi in the superior sagittal sinus. Primary site of absorption is thearachnoid villi - by a pressuredependent process. The other sites of absorption are the parenchymalcapillaries and root sleeves of the large cranial nerves). The production,circulation and absorption of CSF is a continuous and dynamic process.
Etiopathogenesis
Hydrocephalus can result from
1. Over production of CSF
2. Under absorption of CSF
Over production
The only known condition causing hydrocephalus by overproduction is ChoroidPlexus tumor.
Underabsorption
Under absorption may result from:
1. A block in the CSF pathways interfering with the flow of CSF (i.e. obstructive hydrocephalus).
2. A defect in the absorptive mechanism itself.
Both result in an accumulation of CSF. In theformer the obstruction can be inside the ventricular system (referred to as noncommunicating hydrocephalus) or in the subarachnoid spaces (termedcommunicating hydrocephalus).
Clinical Features
Infants: The skull is pliable and yielding in thisage. The common manifestations are increased head size, bulging or fullanterior fontanelle, sutural separation, sunset sign, poor feeding,irritability, vomiting, and dilated scalp veins. Cracked pot resonance is often mentioned butseldom elicited.
Hydrocephalus that is congenital (present at birth) iscaused by a complex interaction of environmental and perhaps genetic factors.Aqueductal stenosis and spinal bifida are two examples. Acquired hydrocephalusmay result from intraventricular hemorrhage, meningitis, head trauma, tumorsand cysts. Hydrocephalus is believed to occur in about 2out of 1,000 births. Hydrocephalusin infants and young children is frequently diagnosed at birth or shortlythereafter, With the advent of sophisticated imaging technologies such asmagnetic resonance imaging (MRI) and ultrasonography, hydrocephalus can bediagnosed in utero, before the baby is born.
Children: The common manifestations includeincreasing head size, vomiting, bulging fontanelles (if it is still open),irritability, poor feeding or even refusal of feeds, headache, visual deficits,abnormal ocular movements, gait disturbance, increased tone in the lowerextremities, paralysis of upward gaze and papilledema. Serial measurements ofthe head size are a good indicator of the evolution of hydrocephalus.
Older Children and Adult: Features of raisedintracranial pressure, visual deficits, failing memory, gait disturbance, papilledema,increased tone in lower limbs, enlarged blind spot are encountered in these agegroups
How Is Hydrocephalus Diagnosed?
Hydrocephalus is most commonly diagnosed by ultrasound, CT,or MRI scans. It may also be diagnosed before birth by prenatal ultrasound orfetal MRI scans.
How Is Hydrocephalus Treated?
There is no known way to prevent or cure hydrocephalus. Themanagement of hydrocephalus is as follows:
Medical
There is no definitive medical or non-operative managementof hydrocephalus. It is often resorted to till definitive surgical treatmentcan be carried out The drug that is widely employed is acetazolamide. Thisinhibits the enzyme carbonic anhydrase which is necessary for the formation ofCSF. The long term use of this drug has serious side effects and in fact it maynot be effective after a few days
Surgical
Diversion of CSF The most effective treatment issurgical insertion of a shunt. Endoscopic third Ventriculostomy (ETV) isgrowing in popularity as an alternative treatment method for hydrocephalus.
Measures to divert CSF: The CSF has been divertedcommonly to the peritoneum, pleura and right atrium have proved useful. Theperitoneum is the preferred location for diversion of CSF and the first choice asthe “destination” of CSF.
Components of the shunt
There are three parts in a shunt
(1) the proximal or ventricular catheter
(2) valve
(3) the distal catheter.
I treat a wide spectrum of hydrocephalus withdifferent causes. The most effective treatment is surgical insertion of a shuntinto the ventricle to drain the accumulated CSF from the brain to a other partof the body to be absorbed. A common type of shunt is the ventriculoperitoneal(VP) shunt, which drains spinal from the ventricle to the abdomen. Recently useantibiotic shunts to reduce infections. Endoscopic third Ventriculostomy (ETV)is an alternative treatment method for hydrocephalus. This procedure isperformed with an endoscope (small camera) which is inserted into the third ventricleand a small hole is created allowing drainage of the CSF fluid from the blockedarea.
