1. Will the patient be awake during
the test?
• The patient will be given a small
amount of medication to put them to
sleep.
• Sometimes a muscle relaxing
medication will be given. This
medication usually stops working
in 30 minutes.
What does it feel like to have the
test done?
• The patient may not feel anything
or may have some discomfort, like a
slight tingling sensation at the wrist
• Some discomfort might be felt when
the electrodes are put on
• If the patient starts to feel more
discomfort during the test, pain relief
and sleep medications may be given
Potential side effects
• Burns under the electrodes (very rare)
• Infection at the site of where needle
goes in (very rare)
• Allergic reaction to materials used in the
electrodes (stainless steel)
Contact information after the test
• You can call the patient’s healthcare
provider about the test results and
diagnosis
• Nursing staff can give you more
information about the test
Further information
• If you have any questions, please
contact the patient’s healthcare
provider or nursing staff at the
patient’s bedside
Bayview Campus
2075 Bayview Avenue
Toronto, Ontario M4N 3M5
Telephone: 416.480.6100
www.sunnybrook.ca
PR 30406 (2015/03/12)
Fully affiliated with the University of Toronto
Assessing Patients with
a Brain Injury
Usage of Somatosesnsory Evoked
Potentials may help predict
outcome for patients in a coma

2. A small electrical current is given to the
nerve at the wrist. This creates a signal
that will travel along the nerve and up to
the brain. The electrical current will pass
through a number of important areas
on its way up, including:
• The spinal cord
• The brainstem, which connects the
brain and spinal cord
• A part of the surface of the brain called
the Somatosensory Cortex where the
signal is measured
Where does the signal travel? Electrode LocationsSome injuries to the brain – due to a trauma
to the head (TBI) or because the brain has
been without oxygen for a long time – may
cause someone to go into a coma.
When this happens, the patient’s brain will
need to be tested to see how well it works.
What test is used?
Somatosensory evoked potentials
(SSEP)
Somatosensory Evoked Potentials
(SSEPs) are the small electrical signals
measured on the scalp of the patient made
by the brain. These signals are the normal
response when a small electrical current is
given to a nerve on the arm at the wrist.
Why is this test needed and how
are the results used?
The testing gives the healthcare team
information on how good the connection
is between the nerve at the wrist and the
brain. This helps them understand and
see how well the brain works. By
measuring this connection, SSEP testing
can show how well the patient may do if
they were to come out of a coma.
How long will the test take?
The test will take 1-1.5 hours.
Who will do the test and where?
A neurophysiologist will do the test at the
patient’s bedside.
What will happen during the test?
• The skin of the patient is scrubbed
with a skin prep gel or alcohol swabs
in places where electrodes go
• The electrodes are single-use needles
or small round stickers
• Electrodes are put on the wrists, above
the collar bone, back of the neck
and the scalp
• A small amount of electrical current is
be given to the nerve through
electrodes at the wrists
• The electrical signal is measured from
the electrodes on the scalp
Electrical
Current Given
Measuring
Electrodes
Spinal Cord
Brain Stem
Somatosensory
Cortex
Nerve