Endoscopic Aqueductoplasty with and without Stent

Sir,

I read with interest the article on endoscopic aqueductoplasty (EAP) by Miki et al. [1]. They performed EAP in 6 patients with aqueduct stenosis (AS) by using a flexible neuroendoscope. They have achieved good results in all patients and have not encountered restenosis. However they did not mention the follow-up period. In 1999, Schroeder and Gaab [2] reported that EAP is an effective alternative to third ventriculostomy for the treatment of hydrocephalus caused by a short AS. In 2004, Schroeder et al. [3] reported the long-term results of their patients in whom EAP had been performed. Their patients' mean follow-up period was 40 months. EAP was performed in 39 patients and endoscopic third ventriculostomy (ETV) was also performed simultaneously in 13 patients. They observed restenosis of the aqueduct in 7 patients, after an average of 25 months, ranging from 14 days to 97 months.

Fritsch et al. [4] retrospectively analyzed the outcome of 27 patients who underwent EAP or interventriculostomy with or without stent placement. They concluded that in patients with membranous distal AS, EAP alone is sufficient enough at 2 years follow-up to provide clinical and radiographic sufficiency and in patients with tumor-associated AS, EAP alone will not suffice. If there is an indication for EAP, a stent needs to be placed. In patients with isolated fourth ventricle and a history positive for intraventricular haemorrhage or meningitis, it is very unlikely that an EAP alone will stay open. The high revision rate in this group has led to a change in treatment strategy toward initial stent placement [4].

We have performed aqueductoplasty only in 8, aqueductoplasty with ETV in 11, aqueductoplasty with stent in 5 and aqueductoplasty with stent and ETV in 7 patients. It is not possible to figure out which procedure would be effective when aqueductoplasty and ETV are done simultaneously. Therefore aqueductoplasties with or without stent should be analyzed to find out the need of stenting the aqueduct. Of the 6 adult patients with primary AS, only one needed a second endoscopic procedure following EAP. Restenosis developed 5 months after the first EAP. The patient's symptoms and signs completely improved after ETV. Aqueductoplasty failed in 2 children. A 7-month-old boy with AS and shunt infection underwent EAP at the time of shunt malfunction. He was shunted one week after aqueductoplasty. The other patient was a 5-year-old boy with isolated fourth ventricle. Unfortunately isolated fourth ventricle on MRI and ataxia and dysphagia persisted in the follow-up. MRI in the constructive, steady-state sequences disclosed a web in the aqueduct (Table [1]). Of the 6 patients in whom aqueductoplasty with stent had been performed, 4 patients had primary AS, one patient had a tectal glioma and one had a pineal tumor. In two patients with secondary AS, the brain stem was pushed toward the clivus and there was no space between the brain stem and clivus for a safe ETV. This is why EAP and stenting of the aqueduct were done in both patients. Endoscopic subtotal tumor removal was done prior to EAP with stent in the patient with a pineal tumor. The stent migrated into the third ventricle 3 months later. Aqueductoplasty with stent was performed again and he has been symptom-free for one year. Bilateral subdural fluid collection developed following aqueductoplasty with stent in two infants with marked hydrocephalus. A subdural-peritoneal shunt was implanted in both patients (Table [2]).

Table 1 Summary of the patients who underwent endoscopic aqueductoplasty Patients Gender Age Diagnosis Endoscopic procedure Complications Outcome and final procedure Follow-up (months) 1 male 7 months primary AS and shunt infection EAP failure - VP shunt 57 2 male 10 years primary AS EAP good 52 3 male 5 years isolated fourth ventricle EAP permanent dysconjugate gaze failure 47 4 female 7 years primary AS EAP good 47 5 male 19 years primary AS EAP good 42 6 female 53 years primary AS EAP transient diplopia good 40 7 female 33 years primary AS EAP vertigo and vomiting transient dysconjugate gaze failure - ETV 24 8 male 14 years primary AS and shunt malfunction EAP good 24 AS = aqueduct stenosis, EAP = endoscopic aqueductoplasty, ETV = endoscopic third ventriculostomy.

Table 2 Summary of the patients who underwent endoscopic aqueductoplasty with stent Patients Gender Age Diagnosis Endoscopic procedure Complications Outcome and final procedure Follow-up (months) 1 female 10 years tectal glioma EAP with stent good 34 2 female 3 months primary AS EAP with stent bilateral subdural fluid collection good 29 3 male 3 months primary AS EAP with stent bilateral subdural fluid collection good 27 4 male 33 years pineal tumor EAP with stent and tumor resection transient diplopia and stent migration failure - EAP with stent 12 5 female 22 years primary AS EAP with stent transient vertigo good 12 6 male 23 years primary AS EAP with stent good 6 EAP = endoscopic aqueductoplasty, AS = aqueduct stenosis.

EAP should be performed in short-segment primary and secondary AS when ETV is not feasible. In isolated fourth ventricle, aqueductoplasty should always be preferred to fourth ventricular shunting. Stenting of the aqueduct will prevent restenosis particularly in secondary AS and isolated fourth ventricle. As stated by Schroeder et al. [3] more experience and longer follow-up periods are necessary to determine the place of EAP in the treatment of aqueductal stenosis.

References

• 1 Miki T, Nakajima N, Wada J, Haraoka J. Indications for neuroendoscopic aqueductoplasty without stenting for obstructive hydrocephalus due to aqueductal stenosis.  Minim Invas Neurosurg. 2005;  48 136-141
• 2 Schroeder H W, Gaab M R. Endoscopic aqueductoplasty: technique and results.  Neurosurgery. 1999;  45 508-515
• 3 Schroeder H W, Oertel J, Gaab M R. Endoscopic aqueductoplasty in the treatment of aqueductal stenosis.  Child's Nerv Syst. 2004;  20 821-827
• 4 Fritsch M J, Kienke S, Mehdorn H M. Endoscopic aqueductoplasty: stent or not to stent?.  Child's Nerv Syst. 2004;  20 137-142