Research & Innovation 2015-16 - Page 69

Using sound waves to see the brain
The eye is directly linked to the brain by the optic
nerve, which sits at the back of the eyeball. It delivers
the visual information collected by the retina to the
brain. The optic nerve sheath is a balloon-shaped
structure. As pressure in the brain builds up, fluid from
the brain is forced along this sheath. It dilates the
sheath in the same way that a balloon is inflated.
The optic pathway therefore allows us to extract
important information from the brain using noninvasive imaging techniques. Recent advances in
ultrasound imaging technology have made it a very
appealing tool for assessing raised pressure inside
the skull. The use of ultrasound in neurosurgery is
most appealing, because it is radiation-free, portable,
widely available and relatively cheap.
The way the technique works is that the ultrasound
probe is placed over the closed eye, allowing us to see
the deeper optic structures as they connect with the
brain. The currently used technique requires a snapshot
to be taken of the optic nerve sheath. The width of the
sheath is then compared to other clinical and imaging
markers, to infer whether or not there is increased
pressure in the brain.
How the new technique works
Our study employed several differences from the
existing static imaging technique. Aside from measuring
the changes in the diameter of the sheath as an
indication of increased pressure, we have developed
a dynamic technique that analyses the way
the sheath moves as a result of the
person’s pulse. This motion is then
compared with intracranial
pressure, and demonstrates a
remarkable consistency.
As an initial study,
we performed
the ultrasound
measurement on
a large cohort of
children. Previous
studies using the
ultrasound technique
on children have not
compared it to directly
measured pressure in
the brain. Diagnosing
neurological disease in
children is notoriously difficult,
because the symptoms are often
quite subtle. We also identified certain
shortcomings in the current ‘static imaging’ technique,
which resulted in limited accuracy – a limitation
described in many other studies. 
The static technique takes two to three minutes to
collect all the images that are needed; our technique
could significantly decrease the time required to record
the information, to around 30 seconds. It is also the first
study of its kind to be conducted on such a large group
of patients, with significant results.
The use of non-invasive techniques to measure the
pressure inside the brain in order to diagnose certain
neurological conditions has attracted much attention
recently. These techniques include measurement of
blood flow to the brain, and the pressure in the ear. But
many of these studies have been limited, because of
inconsistent accuracy.
Watch video here
Making the technique more accessible
Our goal is to refine the accuracy and improve the
simplicity of our technique. If we are successful, we
hope that assessing the pressure inside the skull using
this modified technique may be performed at primary
healthcare level. This would speed up the diagnosis
of raised pressure in the brain associated with certain
neurological disorders.
In a resource-challenged environment, such as South
Africa, where the average child with a neurological
condition is referred to the appropriate centre much
later than they should be, an accurate tool that allows
early diagnosis would make a substantial difference.
From a neurosurgical perspective, diagnosing increased
pressure in the brain earlier would be a useful marker of
underlying neurological disease. This simplified
yet effective technique has the potential
to change the way we diagnose certain
neurological conditions. But more
importantly, perhaps, this could
be done at the level of primary
healthcare facilities, such as day
hospitals and clinics.
This study is a collaboration
between UCT’s Division of
Neurosurgery and a leading
Norwegian research institute. It has
received a provisional patent. By
Dr Llewellyn Padayachy, paediatric
neurosurgeon, Department of Surgery,
Faculty of Health Sciences. This article
first appeared in The Conversation. Image
by Michael Hammond.
Listen to Dr Llewellyn Padayachy describe his
research on the US public radio daily programme
The Academic Minute.
Good health and well-being 64

Watch video hereThe ConversationThe Academic Minute

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