Plain Skull X-ray

Synonym: SXR

Headache and head trauma are common presenting problems in both primary care and the Accident and Emergency department.

It is now well recognised that only in a small proportion of cases are plain skull X-ray films (plain skull films) appropriate and likely to aid management decisions. In light of the amounts of unnecessary radiation to which patients are exposed by the use of inappropriate X-rays, the Ionising Radiation (Medical Exposure) Regulation (IRMER) states that practitioners must ascertain that the net clinical benefit of each film justifies the risk involved in undergoing the procedure.

The majority of plain skull films are performed following trauma to the head and, in order to aid decisions as to which patients might benefit from these X-rays, several groups have audited past results from many radiology departments.^1,2,3 From these and other studies it became clear that, whilst intracranial injury is more likely if there is a skull fracture, significant intracranial injury may also occur in the absence of a fracture,and a normal skull X-ray may give a false sense of reassurance.

There is also now useful literature on the prehospital management of head injury.^4,5 Several guidelines have been produced in an attempt to aid the decision as to when a plain skull film may be helpful in both acute and non-acute situations.^6,7

Many departments might still opt for a CT scan in cases where a head-injury is involved and it is best to discuss the individual case with senior colleagues and radiologists, especially as a normal skull X-ray does not rule out intracranial injury. Similarly, it is still worth discussing the role of skull X-ray in non-head injury cases.

Skull films are not indicated routinely for the following indications:

• Headache
• Possible pituitary problems - (CT/MRI preferred)
• Possible space-occupying lesion
• Epilepsy
• Dementia or memory loss
• Middle or inner ear problems
• Nasal trauma - coned views may be requested by appropriate specialist
• Sinus disease - mucosal thickening is a common incidental finding and not diagnostic
• Temporomandibular joint dysfunction - will not show disc abnormality which is the most common cause of dysfunction

Skull films should be interpreted wherever possible, by a doctor with specialist training and/or considerable experience in interpreting such films. In untrained hands approximately 10% of bony abnormalities are not recognised. The absence of a fracture on a skull film does not rule out the possibility of an operable intracranial haematoma in head injured patients. All such findings must be taken in the context of the clinical condition of the patient, e.g. patients with a GCS of 3-8 and no fracture still have a 1 in 27 risk of having an operable intracranial haematoma.⁹