Pediatric Neurosurgeon

Trauma is the second leading cause of death in children less than 15 years of age and head injury is responsible for 20% of these deaths. The outcome in the children depends on the severity of the injury as well as management. Children have a large number of productive years ahead - it is imperative that these children require utmost care and attention. The mechanism of injury in children is distinct from adults with common causes being falls (35%), recreational activities (29%) and traffic accidents (24%). There is also age specific variation with child abuse seen frequently in children less than 2 years of age. Falls are a major cause of head injury in children less than 3 years. Road traffic accidents account for larger numbers as the age of the child increases.

Children as mini adults and treat them similarly. The immature skull has different mechanical properties and the child’s brain is undergoing maturation and development and. The newborn’s skull has pliable thin bones which can significantly deform.The pliability of the skull makes it more vulnerable to injury especially diffuse injury. The child’s brain is much larger in proportion to the body as compared to adults - the newborn’s brain constitutes 15% of body weight compared to 3% in the adult. The relatively larger size of the brain of a child in comparison to the body makes it more vulnerable to injury.

Head injury could be primary or secondary. The primary injury is the immediate Contact forces may result in fractures, localized contusions and hematoma ,hemorrhages and diffuse injury. Secondary injury results from an array of reactive events which follow the primary event and can worsen the initial injury or cause new injury to brain. These events include hypoxia, hypotension, metabolic alterations, fluid and electrolyte imbalance, brain edema, seizures, local and systemic infections etc The secondary injury are preventable and this constitutes an important aim in the management of the head injured child. Various pathologies may be seen in head injured patients.

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).

Skull deformities are a very common reason for referral to pediatric neurosurgery.Premature fusion of cranial suture closure is called craniosynostosis.

Incidence and Aetiology :
Isolated craniosynsostosis occurs due to the premature fusion of a single suture or multiple sutures. The overall prevalence of craniosynostosis is around 1 in 2500 live births, with ranges of 1 in 709 to 1 in 3225 of births. The wide variation seen is due to differences in the various criteria under which one labels craniosynsostosis. Isolated craniosynostosis is far more common than multiple ‘syndromic’ synostosis.Sagittal seems to be commonest, followed by coronal and metopic. True lambdoid synostosis appears rare and is difficult to distinguish from deformational posterior asymmetry, which is considered to be because of positional molding of the cranium.

Common Syndromic Craniosynostosis like Apert and Crouzon have prevalence of about 1 in 65000, each about 4-6 per cent of all craniosynostosis. There is evidence of FGFR2 mutation in Apert Syndrome, FGFR3 in Crouzon syndrome and FGFR1 in Pfeiffer syndrome. Almost all Aperts and about 50 per cent of Crouzons arise de novo and there is a correlation with increase in paternal age. The prevalence of Pfeiffer syndrome is lower than others but there is no definite percentage data.

Apart from this there are rarer types of single gene syndromes associated with other malformations, metabolic storage disorders and learning disabilities.There are chromosomal aberrations of which craniosynostosis may be a feature. There are teratogenic causes associated with anticonvulsants, (Valproate, Hydantoin)cytotoxic agents, (Methotraxate, Cyclophosphomide, Cytarabine) abortifacients, and nitrosatable drugs(Chlorpneramine,Nitrofurantoin, Chlordiazepoxide and Fluconazole).

Classification and Terminology
Over the years, the nomenclature for various craniofacial deformities has remained constant, but with the entry of molecular genetics, there have been additional terms given to the complex multi sutural synostosis. However, in simple terms these deformities can be classified into three different varieties.

1. Sagittal synostosis or Scaphocephaly or Dolichocephaly, is so called when the sagittal suture is singularly prematurely fused and the head attains a longish anteroposterior length with or without frontal bossing.
2. Unicoronal synostosis [Anterior-Plagiocephaly] when there is flattening of one side of the forehead and a mild facial scoliosis, due to premature fusion of one coronal suture.
3. Metopic synostosis or Trigonocephaly, when there is premature fusion of the metopic suture, and the forehead assumes a triangular shape like the keel of a boat.
4. Lambdoid synostosis [Posterior Plagiocephaly] when a single lambdoid suture fuses to produce asymmetric occipital flattening.
5. Bicoronal synostosis or Brachycephaly, where both coronal sutures fuse prematurely and the skull assume spherical shape.
6. Acrocephaly or Turricephaly or Oxycephaly , where both coronals and anterior Sagittal sutures fuse and the skull assumes a pointed tower like shape.