Chapter 76

#### Key Points

1. Ventriculoperitoneal shunts may require peritoneal, pleural, or vascular access and are a frequent cause for collaboration between a pediatric neurosurgeon and pediatric general surgeon.

2. Routine general surgery procedures, including laparoscopic operations, can be performed with a low risk in patients with shunts in place.

3. Myelomeningocele occurs with a frequency of 1 in 1200–1400 live births. Pediatric general surgeons may be called on to assist neurosurgeons with shunt placements, feeding access, or appendicostomies.

4. Fetal interventions may reduce the complications of myelomeningoceles.

5. Juxtaposisiton of neuroectoderm and endoderm during embryogenesis produces a number of congenital malformations involving both neural and gastrointestinal tissues that require a collaborative effort to repair.

6. Neoplasms traversing the neural foramina may require a combined surgical approach to treat. Neuroblastoma and its variants are most common.

This chapter focuses on clinical topics in which there is overlap between pediatric neurosurgeons and pediatric general surgeons. Included are discussions on hydrocephalus, congenital spine and brain malformations, and dumbbell spinal tumors.

#### Hydrocephalus

Hydrocephalus is defined as a pathologic condition in which ventricular enlargement is associated with elevated intracranial pressure (ICP) that occurs when the amount of cerebrospinal fluid (CSF) produced exceeds the amount absorbed. It is among the most common conditions that pediatric neurosurgeons treat. About 40% of the neurosurgical procedures performed at our institution are directed toward the treatment of hydrocephalus.

##### Etiology of Hydrocephalus

CSF is produced at a rate of 0.3 cc/min, regardless of age. The CSF flows from the lateral ventricles to the third ventricle via the foramen of Monro, from the third ventricle to the fourth ventricle through the aqueduct of Sylvius, and out of the fourth ventricle either through the laterally placed foramina of Luschka or through the midline foramen of Magendie. Once out of the ventricular system, the CSF flows into the spinal and cerebral subarachnoid spaces and, ultimately, becomes absorbed into the venous system. The chief site for CSF absorption into the venous system is along the superior sagittal sinus via the arachnoid granulations.

Under ordinary circumstances, CSF production and absorption are matched. Hydrocephalus represents an imbalance between the rate of production and the rate of resorption. Overproduction of CSF (usually by choroid plexus tumors) is very rare. Much more frequently, it is CSF absorption that is impaired. Impairment of CSF absorption can result from a mechanical obstruction within the ventricular system (ie, blockage of flow from 1 ventricle to another) or obstruction within the subarachnoid space at the arachnoid granulations where CSF is absorbed into the bloodstream. The former is known as noncommunicating hydrocephalus, and the latter is referred to as communicating hydrocephalus.

Noncommunicating hydrocephalus can result from obstruction anywhere within the ventricular system but usually occurs at the foramen of Monro, the aqueduct of Sylvius, or the fourth ventricle and its outlet channels. Causes of noncommunicating hydrocephalus include tumors, cysts, inflammatory scarring, ...

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