Cerebral aqueduct stenosis

Case contributed by Dr Rajalakshmi Ramesh

Presentation

Three year history of global headaches. No focal neurological deficits. Initial overseas imaging investigations demonstrated dilated lateral and third ventricles, likely longstanding, and proposed these changes to be secondary to aqueductal stenosis. The patient was underwent insertion of a right frontal ICP monitor with monitoring over 48 hours revealing pressures of 10-20mmHg. Over the months to follow, the patient developed increasing dizziness, poor balance and deterioration of his vision.

Patient Data

Age: 39
Gender: Male
Modality: CT

Lateral and third ventricles are largely dilated. Some encephalomalacia in the right frontal lobe along the previous ICP monitor tract. 

The patient underwent an endoscopic third ventriculostomy and has remained under annual radiological surveillance. 

Modality: MRI

One year post third ventriculostomy. Moderate dilatation of the lateral and third ventricles and the upper portion of the cerebral aqueduct which tapers to a focal stenosis in its inferior portion. The fourth ventricle is of normal calibre. This is in keeping with the known aqueduct stenosis. Thinning of the periventricular white matter and corpus callosum is consistent with the chronic nature of the obstructive hydrocephalus.

Increased CSF flow in the pituitary fossa with flattening of the pituitary gland and a defect in the region of the tuber cinereum may relate to the third ventriculostomy. Linear CSF tract extending from right lateral ventricle through right frontal lobe is most likely the site of a previous ventricular drain.

Small focal area of CSF signal in the medial left thalamus with adjacent low MERGE signal that is low density on CT most likely represents an area of old haemorrhage with cystic encephalomalacia.

Modality: MRI

Six years post ventriculostomy. The 3rd ventriculostomy is clearly patent. Ventricular size and morphology is unchanged. Areas of susceptibility and encephalomalacia/gliosis (including the ventriculostomy tract) are also unchanged. Note is again made of the known aqueduct stenosis with dilated proximal aqueduct and minimal flow through it. No new findings.

Conclusion: Stable findings. Patent 3rd ventriculostomy.

Case Discussion

This case demonstrates the typical features of non-communicating hydrocephalus due to obstruction at the level of the aqueduct of Sylvius.

Cerebral aqueductal stenosis is the most common of which is non-communicating (obstructive) hydrocephalus 1,2 (hydrocephalus is the abnormal enlargement of the ventricles of the brain due to aberrant accumulation of CSF). Although the exact etiology of aqueduct stenosis is unknown, for diagnostic purposes, at its simplest level, it is separated into tumoral and non-tumoral (benign) causes 1. Tumoural causes include tectal plate lesions, periaqueductal tumours, pineal region tumours and posterior fossa space occupying lesions 3. Non-tumoural causes are further divided pathologically into simple stenosis, forking, septum formation and gliosis 4,5. When no cause can be identified, it is referred to as idiopathic aqueduct stenosis 1. Hereditary forms, as an X-linked recessive disorder, have been reported, in particular with Bickers-Adams-Edwards syndrome 1,2. Other cases have been attributed to viral infections like syphilis and tuberculosis 4.

Clinical presentation is dependent upon the cause, with headache, visual deterioration and gait disturbance as common presenting complaints 4

Endoscopic third ventriculostomy is the treatment of choice for benign causes of aqueduct stenosis, whilst formal shunting procedures (for example, ventriculoperitoneal shunt) are reserved for more complex cases 1.

Diagnosis of cerebral aqueduct stenosis is aided by magnetic resonance imaging technology. Common findings on MRI include 3:

  • absence of flow void sign
  • triventricular (third ventricle and both lateral ventricles) dilatation with a comparatively small fourth ventricle
  • narrowing of aqueduct in T2-weighted images
  • inferior and anterior bulging of third ventricle

However, it is important to note that these are not always specific findings for aqueduct stenosis.

 

 

 

Case courtesy of Dr. Frank Gaillard

 

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Case Information

rID: 34449
Case created: 21st Feb 2015
Last edited: 3rd Dec 2015
Inclusion in quiz mode: Included

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