As part of your management in the Brain and Spine Clinic, you will undoubtedly undergo one or more diagnostic investigations. These are key to providing your neurosurgeon with important information about the nature, site and size of your condition. We will be happy to review any investigations you may have already had carried out prior to being seen in the Brain and Spine Clinic, although occasionally we will need to repeat these or request complimentary further investigations.
A description of each of the investigations we use and the potential diagnostic information they provide is described below:
1. MR Scan
Magnetic Resonance (MR) imaging has become the gold standard investigation for the majority of brain disorders. It provides unparalleled anatomical definition, as well as providing superb characterisation of abnormalities such that very accurate diagnoses can be made as to the nature of your condition. It allows us to accurately identify types of tumours, as well as understand the cause of such conditions as trigeminal neuralgia and hemifacial spasm.
The MR images are generated by placing you in a very strong magnetic field. As a consequence of this, there are certain factors which preclude an MR scan being carried out, most notably the presence of metal inside your body whether this be in the form of a pacemaker or a metallic foreign body. You will be asked to fill in a safety checklist before having an MR scan. MR scans will typically last anywhere from 20 to 45 minutes depending upon what sequences need to be carried out. You will be guided through the investigation by the MR radiographers. The other things you will notice about the scanner is how noisy it is and it is also a relatively confined space. If you have concerns about claustrophobia, please do mention this to your surgeon as scans can be done with sedation to make the experience as comfortable for you.
2. CT Scan
A CT scan uses x-ray radiation to image the brain. Whilst it does not provide quite the anatomical definition of MR scans, it is undoubtedly superior in defining the bony anatomy of the skull and skull base. This can be very important both in understanding the relationship of tumours to the skull and sometimes a useful adjunct in characterising the type of a given tumour. CT scans also have the ability of providing excellent detail of the arteries and veins in the brain. Special sequences called CT angiography or CT venography are done for this, which involves injection of intravenous contrast into a vein in your arm.
In a small number of patients with skull base problems, formal angiography of the blood vessels in the brain may prove useful. This is particularly so for patients with glomus jugulare tumours. This entails injecting dye directly into the blood vessels of the brain. Access is obtained through an artery in your groin and catheters are then fed up into the large vessels in your neck from where the dye can be injected. It usually entails a day case admission and will be carried out by an expert neuroradiologist who is skilled in performing cerebral angiography and this is part of the highly skilled team with which the Brain and Spine Clinic works.
If you have a condition which affects your hearing function, it is important to obtain an objective assessment of your hearing by performing an audiogram. There can be 2 parts to an audiogram, a pure tone audiogram and a speech audiogram. Pure tone audiometry simply involves mapping the volume thresholds at which you can hear sounds of particular frequencies. Speech audiograms will give an insight as to the interpretation of sound in more complex speech patterns. If you are referred for an audiogram, this will involve you seeing an ENT member of the team that work with the Brain and Spine Clinic.
5. Visual Field Assessment
For conditions of the skull base which are close to the eye or the optic nerve (the nerve that conveys vision from the eye to the brain), it is important to obtain an objective assessment of your vision. This is done through formal visual field assessment. If required, you will be referred on to one of the ophthalmic specialists who work closely with the surgeons of the Brain and Spine Clinic for this to be carried out.