What Is Hydrocephalus?
Hydrocephalus comes from the Greek: "hydro" means water, "cephalus" means head. Hydrocephalus is an abnormal accumulation of cerebrospinal fluid (CSF) within cavities called ventricles inside the brain. CSF is produced in the ventricles, circulates through the ventricular system and is absorbed into the bloodstream. CSF is in constant circulation and has many important functions. It surrounds the brain and spinal cord and acts as a protective cushion against injury. CSF contains nutrients and proteins necessary for the nourishment and normal function of the brain. It also carries waste products away from surrounding tissues. Hydrocephalus occurs when there is an imbalance between the amount of CSF that is produced and the rate at which it is absorbed. As the CSF builds up, it causes the ventricles to enlarge and the pressure inside the head to increase.
CSF Pathways
The Choroid plexus is the main source of CSF. The CSF formed in the lateral ventricles gains access to the third ventricle through the paired foramina of Munro. From there through the Aqueduct of Sylvius it enters the fourth ventricle from which is exits through the foramina of Luschka and Magendie. Part of it flows down into the spinal subarachnoid space. The bulk flows over the hemispheres and the subarachnoid pathway to be absorbed by the arachnoid villi in the superior sagittal sinus. Primary site of absorption is the arachnoid villi - by a pressure dependent process. The other sites of absorption are the parenchymal capillaries 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 Choroid Plexus tumor.
Under absorption 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 the former the obstruction can be inside the ventricular system (referred to as non communicating hydrocephalus) or in the subarachnoid spaces (termed communicating hydrocephalus).
Clinical Features
Infants: The skull is pliable and yielding in this age. The common manifestations are increased head size, bulging or full anterior fontanelle, sutural separation, sunset sign, poor feeding, irritability, vomiting, and dilated scalp veins. Cracked pot resonance is often mentioned but seldom elicited.
Hydrocephalus that is congenital (present at birth) is caused by a complex interaction of environmental and perhaps genetic factors. Aqueductal stenosis and spinal bifida are two examples. Acquired hydrocephalus may result from intraventricular hemorrhage, meningitis, head trauma, tumors and cysts. Hydrocephalus is believed to occur in about 2out of 1,000 births. Hydrocephalus in infants and young children is frequently diagnosed at birth or shortly thereafter, With the advent of sophisticated imaging technologies such as magnetic resonance imaging (MRI) and ultrasonography, hydrocephalus can be diagnosed in utero, before the baby is born.
Children: The common manifestations include increasing 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 lower extremities, paralysis of upward gaze and papilledema. Serial measurements of the head size are a good indicator of the evolution of hydrocephalus.
Older Children and Adult: Features of raised intracranial pressure, visual deficits, failing memory, gait disturbance, papilledema, increased tone in lower limbs, enlarged blind spot are encountered in these age groups
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 or fetal MRI scans.
How Is Hydrocephalus Treated?
There is no known way to prevent or cure hydrocephalus. The management of hydrocephalus is as follows:
Medical
There is no definitive medical or non-operative management of hydrocephalus. It is often resorted to till definitive surgical treatment can be carried out The drug that is widely employed is acetazolamide. This inhibits the enzyme carbonic anhydrase which is necessary for the formation of CSF. The long term use of this drug has serious side effects and in fact it may not be effective after a few days
Surgical
Diversion of CSF The most effective treatment is surgical insertion of a shunt. Endoscopic third Ventriculostomy (ETV) is growing in popularity as an alternative treatment method for hydrocephalus.
Measures to divert CSF: The CSF has been diverted commonly to the peritoneum, pleura and right atrium have proved useful. The peritoneum is the preferred location for diversion of CSF and the first choice as the “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 with different causes. The most effective treatment is surgical insertion of a shunt into the ventricle to drain the accumulated CSF from the brain to a other part of 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 use antibiotic shunts to reduce infections. Endoscopic third Ventriculostomy (ETV) is an alternative treatment method for hydrocephalus. This procedure is performed with an endoscope (small camera) which is inserted into the third ventricle and a small hole is created allowing drainage of the CSF fluid from the blocked area.
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