HYDROCEPHALUS

Brain consists of neurons and neuroglia. Apart from neural components there are blood vessels and fluid known as cerebrospinal spinal fluid (CSF). CSF is present in the subarachnoid space ( space between Arachnoid & Pia mater) and inside the ventricles. 

In hydrocephalus, there is excess accumulation of CSF. As cranial capacity is limited, so accumulation of CSF causes increase in intracranial pressure (ICP). The excess of CSF can either be due to excess production of due to obstruction of the flow leading to diminished absorption.

There is a condition in which there is excess production, i.e., Choroid Plexus Papilloma or Choroid Plexus Carcinoma. This tumor arises from choroid plexus which contributes almost 80% of daily CSF formation ( remaining CSF is formed by Ependymal lining of ventricles & brain parenchyma). As this condition involves neoplastic growth of choroid plexus, there is hydrocephalus. So, there is communicating hydrocephalus, i.e., there is ventriculomegaly despite of no ventricular obstruction. This tumour is more common in younger age group. Choroid plexus papilloma has reported in newborns and infants. There is disproportionate enlargement of ventricles despite of a small intraventricular tumor.

About 0.33 mL / min is the CSF formation rate ( about 20 mL/hour & 500 mL /day). CSF circulation occurs & it gets absorbed by brain parenchyma, choroid plexus, arachnoid villi& granulations in dural venous sinuses. Total CSF in adult brain at one time is approximately 150 mL of which 25 mL is contained inside ventricle.

hydrocephalus can be congenital or acquired. The congenital hydrocephalus is usually seen in new borns and infants. The commonest cause is congenital aqueduct stenosis. As the cranial sutures are not fused in children so enlargement of ventricle causes enlargement of the head. So, hydrocephalus in new borns presents with macro crania. There is bulging of the anterior fontanelle. It is easy to recognise. 

The acquired hydrocephalus may be due to secondary to infections, trauma, neoplasms, etc. The meningitis or encephalitis in children may present with hydrocephalus.

CT scan or MRI of the brain can diagnose this condition. It can differentiate both obstructive and communicating hydrocephalus. In obstructive hydrocephalus all ventricle or both lateral and third ventricle are enlarged. Obstruction of aqueduct is very common in tubercular infections of brain as there is vasculitis & increased granulation tissue in peri-mesencephalic cistern. Aqueduct of Sylvius is about 18 mm in length & less than 5 mm in width,  and it is a narrow duct which connects third & four ventricle, 

MRI brain can detect hydrocephalus and any other associated congenital abnormality like Chiari Maformation, Dandy Walker Malformation, Schizeccephaly, Porencephalic cyst, corpus callosal agenesis, etc. 

In conditions where hydrocephalus is due to infections or neoplasms, the MRI brain with contrast is useful.

On CT scan of brain, the increase in hydrostatic pressure is reflected as hypo density around the ventricle that is known as Periventricular lucency (PVL). The frontal horns of lateral ventricles are enlarged, third ventricle becomes globular ( 3rd ventricle is normally seen as slit like in axial images of brain CT). The temporal horns are usually not more than than 2 to 3mm or may not be seen on routine brain CT with 1 cm slices, but in hydrocephalus it is increased in size.

The conservative treatment includes Tablet Acetazolamide ( Diamox) 250 mg three times a day in an adult of 60 kg weight. It is carbonic anhydrase inhibitor & reduces CSF formation.

Surgical treatment involves Endoscopic Third Ventriculostomy (ETV), and Ventriculoperitoneal shunt( VP shunt) surgery.

Now a days, the  endoscopic treatment of hydrocephalus is an established technique of treating hydrocephalus. Previous works of Lespinase, Dandy, Mixter, Fay and Grant had contributed in the evolution of this concept. 
Lespinasse in 1910 was the first one to perform endoscopic choroid plexus fulgration for treating hydrocephalus.
Dandy described the open technique for third ventriculostomy for treatment of hydrocephalus.
In 1923, Mixter first  described percutaneous ventriculostomy, and Fay Grant published the visual record of endoscopic anatomy.
The aim of this surgery is to create a passage in the floor of the third ventricle and to allow the flow of CSF into the pre pontine cistern so that obstruction at the aqueduct can be avoided. The easiest example to explain is of obstructive hydrocephalus due to aqueductal stenosis. In this condition, patient presents with enlargement of the lateral ventricles and third ventricle. The obstruction at the aqueduct causes obstructive hydrocephalus and the cerebral sulci are effaced. So, an endoscope is introduced through the frontal horn of right lateral ventricle and advanced into the third ventricle through dilated Foramen of Monro. Floor of the third ventricle is visualized and an opening is made in the floor of the third ventricle allowing the CS flow to the pre-pontine cistern.