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Head trauma

 

Common causes of head trauma

  • Falls
  • Assault
  • Road traffic collisions (RTCs)

 

Pathophysiology of head trauma

  • Coverings and spaces:
    •  The coverings of the brain, or meninges, can be divided into three layers from superficial to deep:
      • Dura mater
      • Arachnoid mater
      • Pia mater
    • The dura is a tough fibrous layer that adheres to the internal surface of the skull; it forms the falx cerebri and tentorium cerebelli, and encloses large venous sinuses
    • Between the skull and the dura lies the extradural space; laceration of the middle meningeal artery can cause an extradural haematoma
    • The arachnoid is thin and transparent; it is not attached to the dura
    • Between the dura and the arachnoid lies the subdural space; laceration of bridging veins that travel from the brain surface to the venous sinuses can cause a subdural haematoma
    • The pia is firmly attached to the surface of the brain
    • Between the arachnoid and the pia lies the subarachnoid space, which is filled with cerebrospinal fluid (CSF) that drains from the ventricles; brain contusions can cause a subarachnoid haemorrhage
  • Intracranial pressure (ICP):
    • The skull is a rigid box with incompressible contents
    • ICP depends on the volume of intracranial contents: blood, CSF and brain tissue
    • Normal ICP = 5-12 mmHg
    • Elevated ICP can reduce cerebral perfusion and cause or exacerbate ischaemia
  • The Monro-Kellie doctrine:
    • Because the volume of the skull is fixed, any increase in volume of one of its components, such as an expanding extradural haematoma, has to be compensated for by a corresponding reduction in volume of another component
    • Initially CSF and blood are shunted out, providing a degree of buffering and preventing a rise in ICP (compensated state)
    • Once displacement of CSF and blood has been exhausted, a critical point is reached and a sharp rise in ICP occurs (decompensated state)
  • Cerebral blood flow (CBF):
    • CBF is proportional to cerebral perfusion pressure (CPP)
    • CPP = mean arterial pressure (MAP) – ICP
    • As ICP rises, MAP rises to maintain CPP; excessively high MAP leads to a reflex bradycardia and this is the basis of Cushing’s reflex
    • CPP is autoregulated at MAP = 50-150 mmHg
    • If MAP <50 mmHg, CPP falls and ischaemia and infarction may occur
    • If MAP >150 mmHg, CPP rises and cerebral oedema may occur
    • CPP also varies with changes in PaO2 and PaCO2; hypoxia and hypercapnia lead to cerebral vasodilatation whereas hypocapnia causes cerebral vasoconstriction
    • CPP should be maintain ≥70-80 mmHg and most clinicians aim for ≥90 mmHg; the critical level for ischaemia is thought to be 30-40 mmHg
  • Uncal herniation and false localising signs:
    • An expanding intracranial haematoma may cause a region of the temporal lobe known as the uncus to herniate through the tentorial notch
    • This can cause compression of the ipsilateral oculomotor nerve which runs along the edge of the tentorium
    • Compression of its parasympathetic fibres which lie on the surface of the nerve, cause pupillary dilatation due to unopposed sympathetic activity; this may be accompanied by a down and out gaze
    • In addition, compression of the corticospinal tract which decussates caudally in the medulla causes contralateral hemiparesis
    • Therefore ipsilateral pupillary dilatation and contralateral hemiparesis are the classical signs of uncal herniation from an expanding intracranial haematoma

 

Worrying clinical features in head trauma

  • Headache
  • Vomiting
  • Confusion
  • Seizures
  • Reduced Glasgow coma scale (GCS)
  • Amnesia
  • Focal neurology
  • Visual disturbance
  • Dilated/’blown’ pupil and contralateral hemiparesis
  • Scalp lacerations
  • Open or depressed skull fractures
  • Signs of basal skull fracture
    • Periorbital ecchymoses (panda eyes)
    • Postauricular ecchymoses (Battle’s sign)
    • CSF otorhinorrhoea
    • Haemotympanum
  • Cushing’s triad (very late sign)
    • Hypertension
    • Bradycardia
    • Irregular respirations
  • N.B. there is inadequate space within the cranial cavity for haemorrhage to cause shock; if the patient has sustained head trauma and is shocked, look elsewhere for the source of haemorrhage and/or consider alternative causes of shock other than haemorrhage

 

Assessment of consciousness in head trauma: Glasgow coma score (GCS)

  • Adult GCS:
    • Eye opening
      • E4 = spontaneously
      • E3 = to voice
      • E2 = to pain
      • E1 = none
    • Verbal response
      • V5 = conversation
      • V4 = confused
      • V3 = words
      • V2 = sounds
      • V1 = none
    • Motor response
      • M6 = obeys commands
      • M5 = localises
      • M4 = withdraws
      • M3 = flexes
      • M2 = extends
      • M1 = none
  • Paediatric GCS
    • Eye opening
      • E4 = spontaneously
      • E3 = to voice
      • E2 = to pain
      • E1 = none
    • Verbal response
      • V5 = normal words/sounds
      • V4 = fewer words/sounds, spontaneous cry
      • V3 = cries to pain
      • V2 = moans to pain
      • V1 = none
    • Motor response
      • M6 = obeys commands
      • M5 = localises
      • M4 = withdraws
      • M3 = flexes
      • M2 = extends
      • M1 = none

 

Imaging in head trauma

  • Adult NICE indications for CT scan:
    • GCS <13 initially
    • GCS <15 at 2 hours post-injury
    • Suspected open or depressed skull fracture
    • Signs of basal skull fracture
      • Periorbital ecchymoses (panda eyes)
      • Postauricular ecchymoses (Battle’s sign)
      • CSF otorhinorrhoea
      • Haemotympanum
    • Post-traumatic seizure
    • >1 episode of vomiting
    • Focal neurological deficit
    • Loss of consciousness/amnesia + one of the following
      • Age >65
      • Dangerous mechanism (pedestrian or cyclist struck by a motor vehicle; occupant ejected from motor vehicle; fall from >1 m or five stairs)
      • >30 min retrograde amnesia
    • Although not officially one of the NICE indications, many Emergency Departments consider anticoagulation an absolute indication for CT scan in the context of head trauma
  • Paediatric NICE indications for CT head:
    • GCS <14 initially for children >1 year old
    • GCS <15 initially for children <1 year old
    • GCS <15 after 2 hours post-injury
    • Suspected open or depressed skull fracture, or tense fontanelle
    • Signs of basal skull fracture
      • Periorbital ecchymoses (panda eyes)
      • Postauricular ecchymoses (Battle’s sign)
      • CSF otorhinorrhoea
      • Haemotympanum
    • Post-traumatic seizure
    • ≥3 episodes of vomiting
    • Focal neurological deficit
    • Suspicion of non-accidental injury (NAI)
    • Children <1 year old + bruising/swelling/laceration >5 cm
    • >1 of
      • Witnessed loss of consciousness > 5 min
      • Abnormal drowsiness
      • Dangerous mechanism (pedestrian or cyclist struck by a motor vehicle; occupant ejected from motor vehicle; fall from >1 m or five stairs)
      • Amnesia >5 min

 

 Initial management of head trauma: General points

  • The severity of head injury can be graded as mild (GCS 13-15), moderate (GCS 9-12) or severe (GCS 3-8)
  • Manage patients with moderate or severe head trauma, or a dangerous mechanism of injury, from an ABCDE perspective
  • Request a CT head in any patient with one or more NICE indication
  • Discuss any clinically significant CT head findings with neurosurgery
  • Have a low threshold for requesting a CT head in elderly patients with dementia and/or delirium who have fallen and sustained a head injury: It is unlikely they will be able to provide a reliable history or comply with examination and if the fall was unwitnessed there will be no collateral history about the event either
  • Consider whether imaging is required to exclude a cervical spine injury; NICE guidelines advise that if patients require a CT head and imaging is required to exclude a cervical spine injury, then CT neck is the recommended imaging modality
  • Consider what led to the head injury; if it was a fall, what was the cause and are there any other injuries?

 

Initial management of head trauma: Prevention of secondary brain injury

  • Primary brain injury occurs during the initial trauma; secondary brain injury occurs after the initial insult and is potentially preventable or treatable
  • Intubate patients with a low GCS in order to maintain and protect their airway
  • Avoid hypoxia and maintain PaO2 >13 kPa
  • Aim for PaCO2 in normal range (4.5-5 kPa) – therapeutic hypocapnoea is no longer used
  • Intubate and ventilate as required to achieve these aims
  • Tape endotracheal tube in place as opposed to tying them so as not to obstruct venous drainage
  • Avoid excessive intra-thoracic pressures
  • Avoid hypotension and maintain MAP ≥90 mmHg using vasopressors as necessary
  • Avoid hypoglycaemia and replace glucose as necessary
  • Treat seizures; paralyse if necessary
  • Nurse with 30o head-up tilt, neck inline to improve venous drainage and reduce ICP without compromising CPP
  • Avoid cervical collars if possible
  • Consider mannitol 20% 500 ml IV to reduce ICP
  • Ensure adequate analgesia to avoid rises in ICP
  • Aim for normothermia

 

Initial management of head trauma: Wound management

  • The scalp is highly vascular and wounds may need compression to achieve haemostasis
  • Explore and clean any wounds; remove any foreign bodies identified with the naked eye and request a soft tissue radiograph if glass was involved and/or further foreign bodies are suspected
  • Most scalp lacerations can be closed with glue and/or steristrips but deeper wounds will require sutures
  • Consider the need for tetanus and antibiotic prophylaxis

 

Further management of head trauma

  • Admission criteria:
    • CT head with clinically significant abnormalities
    • GCS not returned to normal
    • Awaiting CT head
    • Continued clinical concern e.g. vomiting
    • Other ongoing concern e.g. intoxication
  • Recommended frequency of neurological observations (neuro obs):
    • Half-hourly until GCS = 15
    • Then half-hourly for 2 hours
    • Then hourly for 4 hours
    • Then 2-hourly
  • Discharge advice:
    • Written and verbal advice should be given to all patients discharged following a head injury
    • Advise patients to return if any of the following develop
      • Unconsciousness
      • Confusion
      • Inappropriate drowsiness
      • Problems understanding or speaking
      • Problems with balance
      • Weakness
      • Blurred vision
      • Painful headaches that won’t go away
      • Vomiting
      • Seizures
      • Clear straw-coloured fluid coming from their nose and/or ears
      • Bleeding from one/both ears

 

Click here for medical student OSCE and PACES questions about head trauma

Common Head Trauma exam questions for medical students, finals, OSCEs and MRCP PACES

 

Click here to download free teaching notes on head trauma: Head Trauma

Perfect revision for medical students, finals, OSCEs and MRCP PACES