Ventricles

Hydrocephalus is a significant problem in the majority of patients with myelomeningocele. The pathogenesis of hydrocephalus is multifactorial and is related to aque- ductal stenosis, occlusion of the foramen of Luschka and Magendie, hindbrain herniation, obliteration of the subarachnoid spaces at the level of the posterior fossa, compression of the sigmoid sinuses with consequent venous hypertension, and fibrosis of the subarachnoid spaces (57,58).

Symptoms of hydrocephalus include those that are classic for increases in intracranial pressure—this varies based on the presence or absence of an open fontanelle. In an infant, signs of increased intracranial pressure include lethargy, decreased feeding, bulging fontanelle, increasing head circumference (greater than expected for age), poor developmental progress, and “sun downing.” In patients with a closed fonta­nelle, signs of increased intracranial pressure include headache, vomiting, drowsiness, changes in behav­ior, changes in personality, irritability, diplopia, and papilledema. With the sudden onset of increased intracranial pressure, Cushing's triad may be seen. Cushing's triad consists of progressively increasing systolic blood pressure, bradycardia, and irregular respirations.

At present, placement of a shunt is standard of care for surgical management of hydrocephalus. Shunting has many complications, including both mechani­cal and infectious. Up to 95% of adult patients with myelomeningocele have required at least one shunt revision.

Endoscopic management of hydrocephalus is being increasingly presented as an alternative to shunting. Endoscopic third ventriculostomy (ETV) provides direct communication between the third ventricle and the subarachnoid space by way of interpeduncular and prepontine cisterns. The success rates for ETV as the sole management for hydrocephalus in infants with myelomeningocele range from 12% to 53% (66-70). In most infants with myelomeningocele, ETV alone is not an effective treatment for hydrocephalus. More recently, ETV has been combined with choroid plexus cautery (CPC). This has resulted in an improved suc­cess rate for treatment of hydrocephalus in infants, with a success rate of more than 70%. If an ETV com­bined with a CPC fails, it will typically do so during the first three months (71).

Endoscopic third ventriculostomy may also be an option in the setting of a shunt malfunction in the older child. In one study reported by Teo and Jones, the majority of ETV failures were during the first six weeks postoperatively. However, failures were seen as late as five years postoperatively (70). Longevity of the ETV/CPC for treatment of hydrocephalus beyond two or three years has yet to be determined. It is not known if there is a difference in neurocognitive outcomes in patients treated with an ETV/CPC (shunt-independent) as compared with individuals who are shunt-depen­dent. Although not yet considered “standard of care,” ETV in combination with CPC holds promise for sur­gical management of hydrocephalus without creating shunt dependency and the complications associated with it (71).