Neuroendoscopy

range of happenstance selection bias. There are, of course, clinical circumstances in which the patient is so dogged by shunt complications that even a relatively low chance of success makes an attempt at secondary NTV justifiable. In general, given the recurrent tendency of shunt complications, it seems reasonable to at least consider secondary NTV in every case of shunt malfunction, as proposed by some practitioners [13]. Such a strategy, adopted by some, does have implications in terms of staff and equipment [1].

Some series have recorded a higher failure rate in the very young (Table 6.5), 16 out of 25 NTVs failing in babies aged under 6 months [10]. This has led some surgeons to regard failure as being age-related to the point that some are most reluctant to use NTV in the first year of life. Although overall success rates of 23% for those undergoing NTV in the first year of life [14], and 32% for those born prematurely [15], have been reported, more recent studies have shown that the outcome relates more to the pathology than to age [1]. For aqueductal stenosis there is no difference in outcome between those aged younger than 6 months and those that are older [16], and success rates of more than 80% for congenital aqueductal stenosis have been achieved [17]. A particularly unfavorable pathology for which primary NTV should probably not be attempted is post-meningitic hydrocephalus. However, the low success rate for this pathology, and also for the unfavorable post-hemorrhagic hydrocephalus, is less marked at a later age, and subsequent secondary NTV for shunt failure is always worth considering [16].

Other patients for whom both primary and secondary NTV is particularly successful are those with midline tumors [18] and those with myelomeningocele [19], with success rates of up to 100% and 80% respectively.

Neuroendoscopy in the Management of Shunt Complications and Complex Hydrocephalus

Apart from secondary NTV, neuroendoscopy has other contributions to make in the management of shunt malfunction. Firstly, it should not be overlooked that secondary NTV can still be used to provide ventricular drainage following treatment of shunt infections. Most neurosurgeons manage shunt infections by the technique of shunt removal, interval external drainage with antibiotics, and then shunt insertion; the last stage can often be replaced by NTV [1, 20].

Loculation of the cerebral ventricles is a serious complication of intraventricular hemorrhage and infection, which can be the cause of much morbidity and mortality and frustrated neurosurgical endeavor. Although the surgery looks seductively easy on viewing the imaging, the reality is very different - neuroendoscopic deloculation can be one of the most challenging procedures. The absence of normal anatomy, the unexpected thickness and the vascularity of the septa, and the tendency for the operative field to become rapidly like a souvenir of the Eiffel tower in a snowstorm all make for great difficulties. Pre-operative planning should always include MR, preferably with CISS or equivalent sequences. Intraoperative guidance by ultrasound may assist if there is an appropriate sonographic window. Fenestrations should be as large as possible, and certainly greater than 1 cm in diameter. Cutting/coagulating diathermy is the tool of choice. Multiple procedures may be required.

The most dangerous variant is the loculated fourth ventricle. Unfortunately a neuroendo-scopic approach is only rarely feasible as the cerebral aqueduct is usually densely occluded

Table 6.5. Success rate of NTV in infants

Series

[ref]

n

Characteristics

Success (%)

Jones, 1994

[10]

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