Hydrocephalus.mansfans.com

Definition  Hydrocephalus is not a specific disease; rather, it is a group of conditions that result from impaired circulation and absorption of CSF or, in the rare circumstance, from increased production CSF by a choroid plexus papilloma.

CSF Physiology Sources of CSF:  Choroid plexus (75%) in Lateral, 3rd, and 4th ventricles.  Extrachoriodal (25%) capillary endothelium within brain parenchyma.

CSF Physiology Volume of CSF Infant:

50 ml

Adult:

150 ml

Rate of secretion:

20 ml/hour

CSF Circulation  CSF flow results from the pressure gradient that exists between ventricular system (180 mm H2O) and venous channels (90 mm H2O).  CSF flows from lateral ventricle through foramina of Monro into 3rd ventricle. The through aqueduct of Sylvius to enter 4th ventricle.

CSF Circulation 

CSF exits the 4th ventricle through the paired lateral foramina of

Luschka and the midline foramen of Magendi into basal cisterns.



CSF circulates from basal cisterns posteriorly through the cisterns

system and over the convexities of the cerebral hemisphere.

 CSF is absorbed primarily by the arachinoid villi endothelium. CSF is absorbed to much lesser by the lymphatic channels directed to the paranasal sinuses, along nerve root sleeves, and by the choroid plexus itself.

CSF Circulation

Causes A- Obstructive (non Communicating): results from obliteration to CSF flow in ventricular system. * Aqueduct lesion: 1- Stenosis (mostly congenital) 2- Gliosis following neonatal meningitis or subarachinoid haemorrahge in a premature infant.

* Posterior fossa lesions: 1- Tumors. 2- Malformations: Dandy Walker, Chiari type II.

Causes B- Non obstructive (Communicating): results from obliteration of the subarachinoid cisterns or malfunction of the arachinoid villi 

Subarachinoid hamorrhage.



Tuberculous or pneumococcal meningitis.



Intrauterine infections may also destroy the pathways.



Leukaemic infiltrates in subarachinoid space.

CSF

Causes Dandy Walker: 

cystic expansion of the fourth ventricle due to mal development of its roof during embryogenesis.

Chiari malformation II: 

Hdrocepalus + myelomenigiocele.



Results from failure of pontine flexure during embryogenesis which results in elongation of the 4th ventricle and kinking of brain stem.

Clinical Manifestations Variable and depends on many factors: 1- Age of onset. 2- Nature of the etiology. 3- Duration and rate of increase of ICP.

Clinical Manifestations Infants: 1- Progressive increase in HC. 2- Wide bulging anterior fontanel. 3- Dilated veins on the scalp. 4- Down word deviated eyes (sun set appearance) due to impingement of tectum by dilated suprapineal recess.

Clinical Manifestations Infants: 5- Percussion of head gives crack pot “Mc Ewen sign”. 6- Neurologic symptoms e.g. brisk tendon reflexes and spasticity due to stretching of corticospinal fibers originating from leg motor cortex area.

Clinical Manifestations Older children: manifestations of increased ICP??

Investigations 

Plain x-ray: - Infants: Craniofacial disproportion.

- Children: Separated sutures, erosion of posterior clenoid process, increased convolutional markings (silver beaten appearance).

Investigations 

Trans Fontanelar US



CT



MRI

Plain X-ray

Differential Diagnosis 1. Thickened cranium: Chronic Hemolytic imperfecta.

anemia,

rickets,

osteogenesis

2. Chronic Subdural collections. 3. Megalocephaly due to storage disease e.g. Tay Scahes; Gangliosidosis, muccopolysaccroidosis.

4. Hydranencephaly: Absent cerebral hemispheres.

Treatment  Medical?? 

Extra cranial shunts (ventriculoperitoneal

shunts)

Prognosis  Depends on the cause of dilated ventricles and not on the size of cortical mantle at time of intervention.  Increased risk of developmental disabilities e.g. learning disability.  Accelerated pubertal development in patients with shunted hydrocephalus is relatively common due to increased gonadotrophin secretion in response to increased ICP.