SPECT scan investigations

This page explains about SPECT scan investigations and what to expect when your child comes to Great Ormond Street Hospital (GOSH) to have this procedure.

What is a SPECT scan investigation?

A SPECT scan is used to look at the flow of blood in the brain. When your child has a seizure, the flow of blood to the area responsible increases. In between seizures, there is a reduced flow of blood in this area. This means that these scans can give the doctors information about the location of seizures and whether they are confined to certain areas of the brain.

The scans work by injecting a substance called an isotope into your child’s veins, which then travels to the brain. There are no side effects to this injection. The isotope shows the blood flow clearly on the scan.

There are two types of SPECT scan, an Ictal SPECT scan and an Inter-Ictal SPECT scan. The word ‘ictus’ means attack or seizure, so an Ictal SPECT scan is used during an epileptic seizure, and an Inter-Ictal SPECT scan is used between seizures.

Why does my child need this investigation?

Your child needs this test to examine their seizures in more detail, to find out the location of the seizures and whether they are confined to certain areas of the brain. Your child will also be observed and recorded on video too. The results of this test will give the doctors more information so that they can treat the seizures better.

Are there any risks of this procedure?

It is sometimes necessary to reduce or stop your child’s anticonvulsant drugs while the test is happening, so that your child can have a seizure while in hospital. The doctors will decide this when you and your child come into hospital for the test. If your child has had a number of seizures recently, even though on anticonvulsant drugs, they may be able to continue taking them during the test.

There is always a risk in reducing or stopping your child’s drugs suddenly for this test. This can cause your child to have a longer or more intense seizures than usual. However, the doctors and nurses will monitor your child closely to stop this happening.

If you are pregnant or think you could be pregnant, please let us know at least two days before your child is due to come to Great Ormond Street Hospital. There is a risk that the isotope given to your child could harm your unborn baby, so we advise you to organise another adult to help look after your child for the first 24 hours after the scan. If this is not possible, we may have to reschedule your appointment.

If your daughter is 12 years old or older, we will ask her about her periods and any possibility that she could be pregnant. 

Are there any alternatives to this test?

The doctors can tell a lot from EEG monitoring, but SPECT scan investigations can help fill any gaps in their information. It can also be useful to see a seizure as it is happening on the video recording.

What happens before the test?

Your child may need to stay on the ward for up to five days, depending on which type of scan they are having. If your child is having both scans, you will probably be admitted to the ward on the Monday morning. Ward staff will then attach your child to a continuous EEG monitor, which will stay in place until the Friday.

The doctors can carry out the SPECT scans with your child under sedation, under a general anaesthetic or without either of these. The doctors will have discussed this with you at your appointment before you come into hospital. The Ictal SPECT scan will usually take place on the Wednesday with the Inter-Ictal SPECT scan on the Friday. However, if your child is having the Ictal SPECT scan under general anaesthetic, we will usually arrange the Inter-Ictal SPECT scan for another visit.

The doctors will explain about the test in more detail, discuss any worries you may have and ask you to give permission for the test by signing a consent form. The doctors can carry out the tests with your child under sedation, under a general anaesthetic or without either of these. The doctors will have discussed this with you at your appointment before you come into hospital. If your child is having the test under sedation or a general anaesthetic, another doctor (anaesthetist) will discuss this with you.

If your child has any medical problems, for instance allergies, please tell the doctors about these. If your child has had any infectious diseases like chicken pox or head lice recently, please tell the doctors.

What does the test involve?

Before the test starts the doctor or nurse will put a cannula (a small plastic tube) into a vein in your child’s hand, so that they can inject the isotope more easily. The doctor or nurse can put some local anaesthetic cream on your child’s hand an hour beforehand. This will numb the skin so the cannula does not hurt so much. If your child is apprehensive or scared, please telephone us beforehand to discuss your concerns with our play specialist.

The Ictal SPECT scan

A nurse or doctor will inject the isotope into the cannula in your child’s hand during a seizure. They will then have a scan within about four hours. As the isotope has to be injected during a seizure, a nurse or doctor will be sitting with or near your child while they wait for a seizure. They will usually put aside about five hours for this test. If your child does not have a seizure within this time, the test may be rearranged for another day.

The Inter-Ictal SPECT scan

A radiographer will inject some dye into the cannula in your child’s hand. They will then have a scan, lasting about 45 minutes, either immediately or after being sedated or given a general anaesthetic. 

What happens after the test?

If your child has had to reduce or stop taking anticonvulsant drugs, these will be started again. You will be able to take your child home once he or she has been back on full medication for 24 hours and the frequency of seizures is back to normal.

The doctors will pass on the results of the test at your next outpatient appointment.

Compiled by: 
The Epilepsy Surgery team and Radiology department in collaboration with the Child and Family Information Group.
Last review date: 
July 2012


Please note this is a generic GOSH information sheet. If you have specific questions about how this relates to your child, please ask your doctor. Please note this information may not necessarily reflect treatment at other hospitals.