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Dear Prof. Yamada,

This is a fascinating condition and thank you for highlighting it so well. I particularly enjoyed the discussion. The pre-op images are illustrative of triventriculomegaly and the intra-operative images demonstrate a somewhat distorted and slit-like Sylvian aqueduct mouth suggestive of aqueductal stenosis.

The cause of the aqueductal stenosis is not obvious. The duration of ventriculomegaly is at least 3 years (then aged 13 years) or perhaps longer. This places this patient in the paediatric age group.


The following is noted:
1.There is the presence of both CSP (Cavum Septum Pellucidum) and CV (Cavum Vergae) and it may well be possible that the CVI (Cavum Vellum Interpositi) is also distended.
2. The Brainstem, mammillary bodies, tectum appear lower on the pre-op images compared to the post-op images on the horizontal plane drawn from the nasion.
2.a. The tectum looks particularly compressed from above and is pushed towards the midbrain tegmentum by the expanded 3rd ventricle in the pineal recess. This causes a degree of closure of the aqueduct mouth.
3. The tonsils are in the FM on the pre-op image but sit higher on the post-op
4. It is not clear on the pre-op image if the 3rd ventricle has ballooned into the pineal recess or it is the CVI lying there, but it is possible that it is the 3rd ventricle.
5. The sella looks expanded on the T2W post-op images suggesting long-standing increased CSF pressure.
6. The post-op images no longer show aqueductal stenosis, suggesting that this is not a true congenital case of aqueductal stenosis but what I call a “functional” or acquired stenosis due to pressure from the distending CSF spaces (CSP, CV, CVI, lateral ventricles from above and temporal horns from laterally)

I have the following questions:
1. What was the head circumference of this patient? Was it above the 99.8th percentile, or on the upper range? Was the HC in any way outside of the expected norm for his age or familial tendency?
2. You noted ventriculomegaly 3 years prior to presentation. It would be interesting to carefully measure what parameters had been subtly changing on the annual MRIs
3. Would you think that the pathology in this case may be one that the ventriculomegaly caused the functional aqueductal stenosis?
4. That the treatment of hydrocephalus by ETV resulted in the satisfactory CSF flow through the aqueduct (as well flow through the new ETV opening) because of the reduced pressure on the structures surrounding the aqueduct by the enlarged ventricles and the expanded cava (CSP,CV, CVI)?
5. Do we have an MRA/CTA that shows venous sinuses and venous anatomy? It would be great to see if there is venous hypertension that may explain the ventriculomegaly and the theory for exercise-induced headaches?
6. On the pre-op imaging the cine-MRI CSF flow at the CCJ did appear reduced. What is the significance of this related to his headaches?

Rationale:
Exercise-induced Headaches:
About 90% of exercise headaches have no known cause. About 13% of adolescent athletes suffer from it. Again Chiari malformation is the most common cause seen on brain imaging. Another large study in teenagers found that 13% of exercise induced headaches were located on the top of the head.
There is to my knowledge only a single case report of another intermittent headache case related to aqueductal stenosis, this being a case of thunderclap headaches, rather than exercise-induced. That case also responded to ETV. This is therefore quite a unique case.
Adult aqueductal stenosis presenting as a thunderclap headache: a case report. Mucchiut M, Valentinis L, Tuniz F, Zanotti B, Skrap M, Bergonzi P, Zanchin G, Cephalalgia. 2007;27(10):1171.

Hydrocephalus or Aqueductal Stenosis: what came first?
I am grateful if you could consider the following and let me have your thoughts and views.
In children, normally if there is Aqueductal Stenosis and Hydrocephalus we would conclude that the Hydrocephalus is caused by Aqueductal Stenosis. This is quite natural and it makes sense.
However if that was the case, then, ETV should not be capable of creating CSF flow through the aqueduct (as this is stenosed!), but merely bypass this pathway and drain CSF to the pre-pontine/mesencephalic cistern through the perforated floor of the 3rd ventricle.
On the other hand, given two related conditions, if we act to improve one (Hydrocephalus with reduction in size of CSF storage spaces such as the 3 cava) and this then results in the improvement of another condition (CSF flow through the narrowed aqueduct where there was none), then we are left to conclude that the primary condition is actually Hydrocephalus and Aqueductal Stenosis is secondary to it.

I am very grateful for your precious time and for sharing your wealth of knowledge and experience. Look forward to hearing from you.

kind regards

Guirish

Mr Guirish A. Solanki
Birmingham, UK

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