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Picture quiz: Head injury and decreased consciousness

A 32 year old woman was hit by a car. When the ambulance arrived she was awake and talking, but she seemed confused and said she had a headache. At the emergency department she was still confused and said she had a severe headache. No focal neurological deficits were detected. Radiography of the skull showed a left parietal fracture. Shortly after admission to the ward she vomited and her level of consciousness was recorded using the Glasgow coma scale and was found to be deteriorating. A right extensor plantar response was found on examination. An emergency computed tomogram was taken (fig 1).

Fig 1 Emergency axial computed tomogram

(1) What are the radiological findings shown in fig 1?

(2) What is the most likely diagnosis?

(3) What is the name of the artery that is commonly damaged in this condition?

(4) How is this condition managed?

(1) The axial computed tomogram shows a focal area of high attenuation that is biconvex in shape and is located extracerebrally over the left frontoparietal region. The left lateral ventricle is compressed such that it is obliterated, however, there is no midline shift.

(2) Extradural haematoma. This is seen as an area of high attenuation in the scan.

(3) Middle meningeal artery.

(4) Primary survey (airway, breathing, and circulation) and resuscitation should be carried out and the patient transferred immediately to a neurosurgical unit for urgent craniotomy and evacuation of clots. Haemostasis of the bleeding middle meningeal artery is achieved through diathermy or a haemostatic clip.

Extradural haematomas occur in 1% of cases of head injury in patients admitted to hospital. They occur most commonly among younger people, accounting for two thirds of all cases of intracranial haemorrhage in people under 20 years old. Extradural haematomas are uncommon in elderly people, representing only 5% of intracranial haematomas in patients older than 50 years. This is thought to be secondary to an increased adherence of the dura to the skull with age.

Extradural haematomas occur most commonly secondary to fractures to the parietal and temporal bone, resulting in damage to the middle meningeal artery and vein (fig 2). In 95% of cases the haematoma has an overlying fracture. Blood accumulates rapidly in the extradural space in minutes to hours. The extradural space is located between the dura mater, which is the outermost layer of the meninges, and the skull (fig 3). Damage to the dural venous sinuses can also cause extradural haematomas. This occurs in 15% of patients. Dural venous sinuses are located in between the dura mater. The dura mater is actually made up of two layers that separate in certain anatomical locations—that is, the site of falx cerebri and tentorium cerebelli attachment to the inner surface of the skull (fig 3).

Fig 2 Course of the middle meningeal artery (in red) and its close association relation with the parietal and temporal bones of the skull. Adapted from www.bartleby.com

Extradural haematomas are most commonly found over the temporal region followed by the frontal lobe. They can also occur in the parasagittal area and posterior fossa, but these are uncommon.

Extradural haematomas present as a head injury with a brief period of unconsciousness. This occurs secondary to concussion or cerebral trauma. Recovery is accompanied by a lucid interval in only 25% of cases. Extradural haematoma should actually be suspected in any patient with a head injury and decreasing consciousness.

Patients with head injury are triaged on the basis of their risk of intracranial haemorrhage. As well as level of consciousness, there are several other risk predictors. Clinical guidelines from the National Institute for Health and Clinical Excellence on head injury published in 2003 cover these thoroughly and include clinical evidence.

If undetected, the patient's level of consciousness will deteriorate, increasing headache and progressive hemiparesis caused by compression of the brain by the expanding haematoma. If bleeding continues ipsilateral pupil dilatation will ensue followed by fixed bilateral dilated pupil, tetraparesis, and respiratory arrest. The symptoms of raised intracranial pressure are summarised in box 1.

The radiological investigation of choice in a patient with suspected extradural haematoma is emergency computed tomography. Extradural haematomas characteristically show as a biconvex hyperdense (white) haematoma, with compression and distortion of the underlying brain and ventricle.

Extradural haematomas require urgent neurosurgery. An infusion of mannitol, an osmotic diuretic, or furosemide, a loop diuretic, may be given to decrease the intracranial pressure temporarily during transfer to the neurosurgical unit. Early anaesthetic intervention is important and can be lifesaving. The patient should be intubated and hyperventilated during transfer. This will reduce carbon dioxide concentrations in the blood, causing cerebral vasoconstriction, helping to reduce intracranial pressure.

Craniotomy or craniectomy is carried out followed by evacuation of the haematoma. The source of the bleeding, commonly a middle meningeal artery, is identified and haemostasis is achieved through diathermy or haemostatic clip. In emergency situations burr hole or craniectomy over the haematoma can be done to relieve the pressure. But this seldom results in sufficient decompression.

The mortality in extradural haematomas can be as much as 10-30% in some neurosurgical centres around the world. Less than a third of patients who score below 8 on the Glasgow coma scale have a good outcome. Patients above the age of 65 have the worst prognosis.

In summary, the rapid diagnosis of a patient with an extradural haematoma can be lifesaving. These patients tend to exhibit classic clinical history and characteristic computed tomography. The condition should be suspected in any patient with a head injury and decreasing levels of consciousness. Prompt referral and transfer to a neurosurgical unit should be arranged to prevent permanent neurological disability or death caused by delay in the evacuation of the haematoma.

Correction


Regional anaesthesia

We double check complicated figures and send proofs for authors to check. Despite this, incorrect labels crept through in a diagram (fig 3) that accompanied an article published in May as part of Jonathan Behar and colleagues' series on anaesthesia (Student BMJ 2007;15:186-9). The original label "Posterior longitudinal ligament (ligamentum flavum)" actually pointed to the ligamentum flavum, and the original label "Anterior longitudinal ligament" in fact pointed to the posterior longitudinal ligament. A corrected figure is shown here.

Vertebral column and spinal cord membranes, showing the exact position of spinal and epidural needles

We thank Janet Warwick for reviewing the final version of the manuscript.

Competing interests: None declared.

1. Kaye AH. Essential neurosurgery. 3rd ed. Oxford: Blackwell, 2005:59-62.
2. Rowland LP. Merrit's textbook of neurology. 9th ed. London: Lippincott, Williams, and Wilkins, 1995: 426-8.
3. Lindsay KW, Bone I, Callander R. Neurology and neurosurgery illustrated. 4th ed. London: Churchill Livingstone, 2004: 228-9.
4. Ibanez J, Arikan F, Pedraza S, Sanchez E, Poca MA, Rodriguez D, et al. Reliability of clinical guidelines in the detection of patients at risk following mild head injury: results of a prospective study. J Neurosurg 2004;100:825-34.

       

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