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| Top Ten Head CT Cases for Medical Students |
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The Ward Round is back! This time with 10 top C.T. cases for the budding Finals student! BasicsPresented by: Rachel Marsden - Fifth Year Medical Student, The University of Sheffield Medical School Dr Ian Bickle - Radiology SpR, Sheffield Teaching Hospitals NHS Foundation Trust Patrick Stirling - Fith Year Medical Student, Queen's University Belfast What is CT? Computed Tomography or CT uses digital processing to generate a 3-D image from a large number of 2-D X-rays taken around a single axis of rotation. A picture of a modern CT scanner is seen below. It shows the scanner in the background with the control panel in the foreground. In CT the patient lies supine on the table and the donut shaped scanner rotates taking a large number of x-rays in a single slice. Patients will then move through the scanner to allow a different number of “slices” to be taken through the anatomical area of interest. These x-rays are then re-formatted by the computer and can be viewed by the radiologist in multiple plains. Interpreting the CT Images on CT are seen as various shades of grey based on how much radiation a tissue absorbs. When reporting x-rays it is useful to know something about two key words.
Head CT: some basics It is worth knowing how you would expect tissues on CT head to appear. Keeping attenuation and HU in mind you can work out that:
Contrast IV contrast in CT highlights blood vessels or vascular areas of the brain. It is also useful for identifying areas of high cell turn over such as tumours and infection. Aneurysms, tumours and abscesses all become brighter post contrast administration on head CT. Keeping all this in mind we have ten CT heads for you to look at. Don’t panic, just say what you can see, is it higher or lower attenuation than the surrounding brain? Where in the brain is the abnormality? What shape is it? Think about your brain anatomy and remember to take clues from the history. Enjoy!
Case (1)Extra Dural Haematoma A 24 year old female fell from her horse during a cross country competition, hitting her head on a wooden fence on the way to the ground. She was taken by ambulance to A&E where on examination she had a Glasgow coma scale of 11/15. CT scan is shown below.
Learning point Difference between extradural and subdural
Case (2)Subdural Haematoma An 84 year old male nursing home resident presents with increasing drowsiness. The care assistant who attended with him informs you he has become increasingly unsteady and confused over the past two weeks since falling in the bathroom and has deteriorated rapidly over the past 24 hours. CT scan was performed and is shown below
Bleeding in the brain changes in density with time as shown in the table below Learning points
So why does acute bleeding appear more hyperdense on CT? Blood contains haematocrit and a high concentration of protein. Protein has a high electron density and therefore an evolving bleed in the brain has high attenuation. Slowly over the time the protein is reabsorbed via the CSF and the area of haemorrhage becomes isodense again.
Case (3)Subarachnoid Haemorrhage A 46 year old male with known Adult Polycystic Kidney Disease (APKD) presents to his GP with sudden onset headache associated with nausea and vomiting. His CT scan is shown below 
Learning Points By far the most common cause of SAH is trauma, although ruptured aneurysms are the most common non-traumatic cause. SAH is defined as a haemorrhage into the subarachnoid space so when looking on CT look for high attenuation in the basal cisterns, sylvian fissure, in the ventricles and the interhemispheric fissure (although this is rare).
Case (4)Hypertensive Haemorrhage A fifty five year-old smoker develops a sudden onset right sided hemi-paresis associated with nausea during a five a side football competition. He is a known hypertensive and on questioning admits to being “hit and miss” with his medication and is not usually very active. On arrival at A&E he has developed a headache and is having difficulty with his speech  Learning Point Hypertensive bleeds These bleeds commonly manifest with symptoms of sudden onset hemiparesis and hemiplegia alongside speech difficulties, headache and nausea. Symptoms often occur during periods of activity. Long periods of hypertension “wear away” at blood vessel walls. In the brain this can lead to vessels become blocked and blood leaks into the brain parenchyma. Blood collects to form a haematoma which radiologically is most often seen in the region of the basal ganglia and thalamus.
Case (5)Infarct 75 year old smoker presents to A&E with a 24 hour history of increasing right sided weakness.
Learning point Remember that stroke is a clinical diagnosis; imaging is required to confirm the diagnosis and the type of stroke. It is important to know whether or not you have a haemorrhagic stroke as a haemorrhagic stroke can not be treated with thrombolysis!!! Haemorrhagic strokes are represented by hyperdense areas within a vascular territory.
Case (6)Hydrocephalus 19 year female presents to A&E after falling down a flight of stairs after a night out. She describes a sudden onset worse ever headache associated with nausea and vomiting over the past 3 hours. A non contrast CT head was performed.  Learning Point Hydrocephalus can be classed into two categories, communicating and non communicating. Non-communicating – obstruction to CSF flow is caused by blockage within the ventricles i.e. from an intra-ventricular mass Communicating – there is free flow of CSF out of the fourth ventricle and the obstruction is due to a defect in re-absorption of CSF. This is often secondary to disease within the subarachnoid space such as meningitis or in this case subarachnoid haemorrhage.
Case (7)Skull Fracture A 20 year old pedestrian is hit by a car travelling approximately 25mph. He is thrown to the ground some distance away by the impact and sustains multiple injuries including a head injury. Upon arrival at A&E his GCS is 13/15. CT scan is shown below, using the bone window filters
Learning Points There are two main types of skull fractures Linear – by far the most common type, straight, single break in the bone, beware though, there could be more than one Comminuted or Depressed – rarer and often the result of more severe trauma. Bone breaks in multiple fragments and fragments are depressed into the skull vault. Two rarer types but vital not to miss are Diastic – fracture causes the bone to separate and widen at the skull sutures. Seen in younger patients Basilar – breaks in the bones at the base of the skull. These fractures are often the result of severe trauma. Warning signs that should lead to a suspicion of skull base fracture are blood in the sinuses, CSF leaks from nose and ears and “racoon eyes” due to bruising of orbits as blood collects.
Case (8)Brain Abscess A 24 year old builder is brought to A&E by his worried girlfriend. He has a one week history of fever associated with fatigue and headache and has deteriorated rapidly over the past 24 hours; developing vomiting and increasing confusion and drowsiness. His girlfriend informs you that he has been suffering from toothache on and off for the past fortnight but has been unable to get an appointment with his dentist.
His post contrast CT is seen below Learning Point A brain abscess should always be suspected if a patient has symptoms of infection in combination with symptoms of raised intracranial pressure (headache, vomiting, confusion and coma) and focal neurological damage (seizure, hemiparesis). Most abscesses are caused by spread from local infection such as ear infection; dental abscess and infection of the paranasal sinuses so always keep a look out for these factors in the history and imaging. Brain abscesses can also occur in immuno-comprimised patients such as those with HIV and cancer patients undergoing chemotherapy and these tend to be atypical organisms.
Case (9)Primary Brain Tumour A forty year old female teacher presents to her GP after suffering an “episode” which on description appears to be a generalized seizure. On taking a full history in addition to the seizure she has been suffering from a gradually worsening headache over the past month. Post contrast CT scan is seen below  Learning points There are over 100 different types of primary brain tumour that can be difficult to distinguish between on CT. You can however gain clues as to the type of tumour by the position in the brain. Try to determine if the lesion is:
Case (10)Cerebral Metastases A 48 year old female with a significant past history of right breast carcinoma presents with a three week history of headache, nausea and vomiting and dizziness. Her CT scan is seen below.
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| Last Updated ( Sunday, 07 December 2008 ) | |||||||||||||||||||||||||||||||||||||
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