19A. Traumatic brain injuries

From greek.doctor

Traumatic brain injury (TBI) means external force applied to skull which cause alteration of function and/or morphology of brain. It usually causes loss of consciousness, amnesia, and altered mental state.

It has been called a “silent epidemic”, as it’s one of the most common causes of deaths in the young and active population. In younger adults, it usually occurs due to motor vehicle accidents. In elderly, it’s usually due to falls. It may occur together with traumatic spinal cord injury.

Classification

We can distinguish primary and secondary brain injury. The primary brain injury occurs at the time of the impact and causes immediate clinical effects. These are preventable but not treatable. The secondary brain injury occurs later, due to hypoperfusion, altered autoregulation, and/or oedema. These effects cause symptoms gradually and are both preventable and treatable.

We can also distinguish between closed and open TBI:

  • Closed TBI – dura is maintained – low risk for infection
  • Penetrating TBI – dura is penetrated – high risk for infection

We can also classify the TBI according to the pathomorphology:

  • Focal TBI
    • Concussion/commotion – mild, no visible structural damage
    • Contusion – small, focal intraparenchymal haemorrhage
    • Epidural haemorrhage (bleeding from middle meningeal artery, good prognosis after surgery)
    • Subdural haemorrhage (bleeding from bridging veins, poor prognosis)
  • Diffuse TBI
    • Diffuse axonal injury
    • Diffuse neuronal somatic injury
    • Cerebral oedema

The severity of TBI can be graded based on the Glasgow coma scale:

  • Mild TBI – GCS 13 – 15
  • Moderate TBI – GCS 9 – 12
  • Severe TBI – GCS < 9

Clinical features

Patients may present with headache and vomiting, which is usually not severe and indicative of low risk for severe injury. The following are features of more severe injury:

Typical for epidural haemorrhage is that the patient experiences a lucid interval, which is a period of consciousness which occurs after they first lose their consciousness. After the lucid interval, the consciousness is lost again.

Diagnosis and evaluation

In case of no or only mild symptoms (headache, vomited once), CT is usually not needed. In everyone else, a CT should be performed. The difficulty lies in determining which patients have such a mild TBI that CT is unnecessary.

Some places use a serum biomarker called S100B to reduce the number of CTs taken. If the patient had GCS 14-15 with repeated vomiting or loss of consciousness, S100B can be measured. If levels are normal, CT is not necessary.

In epidural haemorrhage, the CT shows a lens-shaped (biconvex) hyperdense lesion. In subdural haemorrhage, the CT shows a concave or linear hyperdense lesion.

Consider concomitant spinal cord injuries. In patients with severe TBI, ICP monitoring should be performed.

Treatment

The goals of management of TBI are to prevent secondary injury, by providing proper blood flow, perfusion pressure, and oxygen supply. This is achieved by supportive treatment, ensuring normoxaemia, normocapnia, normotension, normothermia, and euglycaemia. Hypocapnia should be avoided as it decreases CBF.

In some cases we might use controlled hypothermia to protect the brain. In case of GCS < 8 the patient should be intubated.

In certain cases, haematomas can be evacuated surgically. If the ICP is high, it might be necessary to drain it. Other measures to decrease ICP include elevated head, hyperventilation, and diuresis with mannitol. Seizures are not uncommon following a TBI, and antiepileptic medication may be necessary.

Complications

Prognosis

Subdural haematoma has the worst prognosis of the different types.