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NEURORADIOLOGY Table of Contents   
Year : 2005  |  Volume : 15  |  Issue : 1  |  Page : 19-20
Compensated aqueduct of sylvius obstruction by web-a case report.

The Barnard Institute of Radiology, Madras Medical College, Chennai-600 003., India

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Keywords: Aqueduct of Sylvius, Hydrocephalus

How to cite this article:
Flora N, Kulasekaran N, Mudali S K, Swaminathan T S. Compensated aqueduct of sylvius obstruction by web-a case report. Indian J Radiol Imaging 2005;15:19-20

How to cite this URL:
Flora N, Kulasekaran N, Mudali S K, Swaminathan T S. Compensated aqueduct of sylvius obstruction by web-a case report. Indian J Radiol Imaging [serial online] 2005 [cited 2021 Mar 1];15:19-20. Available from:

   Introduction Top

Congenital hydrocephalus due to aqueductal obstruction usually present inutero or in neonates. Some patients may have compensation of CSF flow dynamics during childhood and may not be symptomatic until CSF production increases during adolescence or even later typically in their late thirties. We report a patient with compensated aqueduct of sylvius obstruction by web who presented in his late


   Case report Top

A 28 year old man presented with episodes of headache on and off for three months. There was no history of nausea or vomiting or blurring of vision. There was no past history suggestive of meningitis.

MRI of the brain, T1W sagittal image [Figure - 1] and T2W sagittal image [Figure - 2] shows dilatation of third and lateral ventricles. Fourth ventricle appears normal in size. Corpus callosum shows marked upward bowing. There is flaring of the upper part of the aqueduct with a thin membrane noted in the distal part of aqueduct. The normal CSF flow void in aqueduct is also not seen. There is no evidence of interstitial edema around the ventricles. Coronal T2W image [Figure - 3] and coronal FLAIR image [Figure - 4] also show the web causing aqueductal obstruction. MRI features are consistent with compensated aqueduct of Sylvius obstruction by web.

   Discussion Top

Aqueductal obstruction constitutes three percent of adult hydrocephalus. [1]. Aqueductal obstruction is usually a malformation occurring as a sporadic developmental anomaly.

There are three main types of aqueductal obstruction.

  1. Aqueductal gliosis representing an overgrowth of fibrillary glia that constricts the lumen.
  2. Forking of aqueduct in which it is replaced by several canaliculi
  3. Aqueductal obstruction by a thin ependymal septum generally located at its caudal end.

Despite it congenital origin, the alterations of CSF dynamics can remain compensated and undiagnosed for several years [1]. Clinical features in the compensated stage include episodes of headache and nausea. Head ache and nausea is more severe in the morning because CSF is drained less in the recumbent position and may be relieved by sitting up. There may be an uneven development of cognitive function with changes in behaviour and decline in school performance.

The patient may also present with endocrine disorder due to distraction of hypothalamus and pituitary stalk by a grossly dilated third ventricle leading to growth retardation, precocious or delayed onset of puberty. The patient may also present with failure of upward gaze and accommodation due to pressure on the tectal plate.

In the late acute decompensated stage, the patient may present with vomiting drowsiness and episodes of graying out of vision due to increased intra cranial pressure. The patient may also have spastic weakness of lower limbs with gait disturbance due to stretching of pyramidal tract around dilated third ventricle.

On physical examination, head circumference may be normal or only slightly increased. Imaging with CT and MRI will show dilated third and lateral ventricles with marked upward bowing of corpus callosum. The normal aqueductal CSF flow void in MRI will not be seen, indicating obstruction to CSF flow through the aqueduct[2]. Interstitial edema around the dilated ventricles will not be seen in the compensated stage of obstruction. MRI offers better morphological definition of the ventricles and shows some causal lesion like web. MR imaging with cinephase CSF velocity study has improved the diagnosis of this type of hydrocephalus by illustrating the aqueductal stenosis [2]. The treatment option in the compensated stage is with drugs like acetazolamide and frusemide to limit the evolution of hydrocephalus by decreasing fluid secretion by choroid plexus [3]. In the late decompensated stage the treatment option is surgical.

The new alternative to traditional ventriculo peritoneal shunting is endoscopic membrane fenestration with third ventriculostomy, creating a hole between high pressure intra ventricular compartment to low pressure sub arachnoid space. MR CSF flow velocity imaging can be used in the follow up of these patients to evaluate third venticulostomy by showing the patent ostium.

In cases of shunt procedures also CSF flow velocity imaging by MR can show the patency of the shunt.

   Conclusion Top

Congenital aqueductal stenosis can present later in adult age due to compensation of CSF flow dynamics during childhood and normalization of clinical symptoms are more important in evaluating the benefits of treatment than in the decrease in ventricular size.

   References Top

1.Julian. R.Youmans. Neurological Surgery, 4th Ed. W.B.Saunder's Company, 1996:893-920.  Back to cited text no. 1    
2.David.D.Stark, William.G.Bradley, Magnetic Resonance Imaging, 3rd Ed. Mosby, 1999:1483-1508.   Back to cited text no. 2    
3.Maurice Victor, Allan. H.Ropper. Principles of Neurology, 7th Ed. Mc.Graw Hill, 2001:734-819.  Back to cited text no. 3    

Correspondence Address:
N Flora
Barnard Institute of Radiology, Madras Medical College, Chennai-600 003.
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0971-3026.28736

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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]

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