53 Aqueductal Stenosis

Jeffrey Atkinson

Fig. 53.1 (A) midsagittal T1-weighted magnetic resonance image and (B,C) axial fluid-attenuated inversion-recovery image of the brain.

Clinical Presentation

A 15-year-old adolescent boy presents with a long history of intermittent syncopal episodes.

He was initially investigated at age 10 by a neurologist with normal cranial imaging, normal electroencephalogram (EEG), and normal physical examination.

Representative images are presented in Fig. 53.1.

Questions

Describe the findings on the imaging study.
What advice would you give the patient in terms of management?
What would be the basis for intervention in this patient?
Describe possible surgical interventions for the management of this patient.

The patient underwent a successful endoscopic third ventriculostomy (ETV) and biopsy of the third ventricular mass. The pathology was consistent with juvenile pilocytic astrocytoma.
Describe the risks associated with the above procedure.
Are there any specific technical considerations for the procedure?
What is the long-term prognosis for this patient?
What is your management strategy for the patient given the above information?

Answers

Describe the findings on the imaging study.

The MRI demonstrates ventriculomegaly at the level of the lateral ventricles with some transependymal edema.
There is also an apparent mass in the posterior part of the 3rd ventricle and tegmentum of the brainstem.

What advice would you give the patient in terms of management?

Management strategies for this patient can be divided into observational and interventional strategies.
Given the relatively minor history and lack of clear relationship between the lesion and symptoms, some may argue that the patient could be followed closely.
However, the change in lesion and ventricles from the scan 5 years previously and the transependymal cerebrospinal fluid (CSF) on MRI, all argue for treatment of hydrocephalus.

What would be the basis for intervention in this patient?

The basis for intervention is the transependymal migration of CSF seen on MRI, the clear progressive dilation of the ventricles over time, both of which suggest increasing hydrocephalus, and the probable growth of the mass over the time interval between the two imaging studies.

Describe possible surgical interventions for the management of this patient.

This patient could receive CSF diversion by means of a ventriculoperitoneal (VP) shunt.

CSF diversion could also be performed by ETV.1

Consideration could be made for biopsy of the lesion at the time of ETV given the apparent location of the lesion in the posterior 3rd ventricle.² It is not very likely that this lesion will progress and thus consideration for resection of this lesion would not be necessary absent progressive growth or unfavorable histology on biopsy.
Describe the risks associated with the above procedure.
- ETV presents risks of late or early failure, fornix injury, intracerebral hematoma, hypothalamic injury, basilar aneurysm or arterial injury, and uncontrolled bleeding.^3,4
Are there any specific technical considerations for the procedure?
- Technical considerations revolve specifically around the preferred option of ETV with lesional biopsy.
- It would be essential that the ETV be performed first to make sure that this procedure was not aborted due to bleeding from the biopsy²
- Second to perform both the ETV and the biopsy a flexible endoscope would be needed.
- Alternately, using a rigid scope, consideration must be given to placement of a single, slightly more anterior burr hole or two burr holes to allow an appropriate trajectory to both the anterior 3rd ventricle and ventriculostomy site and the posterior 3rd ventricle for the biopsy.
What is the long-term prognosis for this patient?
- Expectations for the long-term control of hydrocephalus in this patient are good, approximately 80%.
- Typically tegmental, posterior 3rd ventricle lesions of this type are benign and slow growing and cause no further problems apart from the hydrocephalus.
- If a biopsy was performed, this may further define prognosis.
What is your management strategy for the patient given the above information?
- ETV with or without biopsy would be the best option followed by serial imaging observation of the mass lesion.^2,5