Materials and Methods:
Retrospective analysis of 60 patients during the period 2011 to 2015 ,
presented with clinical and morphological findings suggestive of hydrocephalus where various imaging modalities was utilised to assess CSF flow dynamics in diagnosis and follow up.
Findings and procedure detail:
Role of different modalities like neurosonography (NSG),
CT,
MRI,
phase contrast-MRI (PC-MRI),
3D- heavily T2W MRI ,
Diffusion weighted imaging in identifying/localising the pathological cause of hydrocephalus and associated secondary changes .
Physiology of CSF production & circulation:
Normal Cerebrospinal fluid (CSF) production is 500ml/day from the choroid plexus,
located within the choroid plexus located at lateral and fourth ventricles.
Fig. 1: Properties of CSF
References: Dr Anirudh Nair
From choroid plexus,
CSF flows to lateral ventricle,
foramen of Monro,
third ventricle,
aqueduct of Sylvius,
fourth ventricle,
lateral foramina of Luschka and medial foramen of Magendie,
subarachnoid space,
arachnoid granulations into the dural sinus.
Fig. 2: CSF circulation
References: Dr Anirudh Nair
Functions of CSF are mechanical protection of brain and spinal cord,
nutrient supply and elimination of products of catabolism.
Fig. 3: Functions of CSF
References: Dr Anirudh Nair
Patho-physiology affecting CSF circulation:
Intracranial pressure (ICP) rises if production of CSF exceeds absorption as a result of overproduction,
increased resistance to CSF flow,
or increased venous sinus pressure.
As ICP rises CSF production is impaired.
Compensation occur through transventricular seepage of CSF and also by absorption along nerve root sleeves.
Temporal horns dilate first,
resulting in elevation of the corpus callosum,
stretching of septum pellucidum.
Definition- Hydrocephalus:
Hydrocephalus is a hemodynamic disorder of cerebrospinal fluid (CSF),
due to disturbances in flow,
formation or absorption that leads to increased cerebrospinal fluid volume in the central nervous system
Imaging in hydrocephalus:
CT/MRI brain: To assess the size of ventricles,
chiari malformation,
site and type of obstruction.
Neurosonogram: To asses grade of intraventricular haemorrhage,
screening for hydrocephalus and follow up.
Skull radiography: Detect erosion of sella tursica or copper beaten cranium.
Confirm the shunt position/hardware patency.
CSF flow study: Assess the stroke volume (SV) in cerebral aqueduct,
select patients for whom there shall be an improvement in clinical symptoms post shunting 1.
The SV values however is institution dependent and varies.
Diffusion tensor imaging (DTI): Fractional anisotropy and mean diffusivity aids in recognition of microstructural changes in periventricular white matter not easily detected on coventional MR 2.
Radionuclide cisternography: In NPH to assess prognosis post shunting3.
Not commonly used.
Fig. 4: Role of Imaging in hydrocephalus
References: Dr Anirudh Nair