CNS Injury

1
CNS Injury

• Hashmi

2
CNS Injury

• CNS injuries remain the leading cause of
  morbidity and mortality for young people in the
  world
• 148,000 Americans died from various injuries
• Traumatic brain injuries (TBIs) caused 50,000
  deaths
• The average incidence is 95 cases per 100,000
  population
• Twenty-two percent of people who have a TBI die
  from their injuries
• Approximately 10,000-20,000 spinal cord injuries
  occur each year.
• The risk of incurring a TBI is especially high
  among young adults and people older than 75 years
• Twice as high for males as for females
• Motor vehicle crashes, violence, and falls are
  the leading causes of TBI
• Nearly two thirds of firearm-related TBIs are
  classified as suicidal in intent.
• The leading causes of TBI vary according to age
• Falls are the leading cause of TBI among people
  aged 65 years and older
• Transportation accident leads among persons aged
  5-64 years
• Firearms surpassed motor vehicles as the largest
  single cause of death associated with TBI in the
  US
• The outcome of these injuries varies greatly
  depending on the cause
• Death results from 91 of firearm-related TBIs

3
Anatomy

• The brain and the spinal cord make up the CNS
• The brain
• 3 membranes (meninges), is encased in the skull
• The scalp covers the bone of the top of the skull
• The facial bones and muscles and the neck muscles
  cover the base of the skull
• A deep projection of the dura (falx cerebri)
  divides the brain into the cerebral hemispheres
• The tentorium, divides the cerebral hemispheres
  from the posterior fossa, which contains the
  cerebellum
• The brain stem
• Arises from the middle of the cerebral
  hemispheres
• Descends through an opening of the tentorium
  (tentorium hiatus)
• Continues as spinal cord after the foramen magnum
• In adults, it extends down to the level of the
  12th thoracic or first lumbar vertebra
• In children, the spinal cord terminates much
  lower, depending on the age of the child

4
Pathophysiology

• Consciousness is defined as the ability to be
  aware of oneself and one's surroundings
• The reticular formation, a very complicated and
  poorly defined collection of nerve cells in the
  brain stem, continuously maintains the activity
  of the rest of the brain and is considered
  responsible for maintaining consciousness
• Intracranial pressure (ICP) is the normally
  positive pressure present in the cranial cavity
• It ranges from 5 mm Hg in an infant to 15 mm Hg
  in an adult
• Cerebral perfusion pressure (CPP) equals mean
  arterial pressure (MAP) minus ICP
• CPP should be maintained at higher than 70 mm Hg
  in adults
• Maintaining adequate circulation in the brain is
  of vital importance
• Cerebral blood flow is kept stable under normal
  conditions due to linear changes in
  cerebrovascular resistance
• This phenomenon is called cerebral autoregulation
  and means that changes in CPP between 50 mm Hg
  and 150 mm Hg do not cause significant changes in
  the cerebral blood flow
• Under traumatic conditions, autoregulation is
  lost, resulting in a linear relationship of BP to
  cerebral blood flow
• The Kellie-Monro principle
• Implies that changes in one of the intracranial
  components will result in compensatory alteration
  in the others
• Because the cranium is a closed space, the sum of
  the intracranial volumes of brain, blood, csf,
  etc, are constant

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Herniation

• Movement of the brain across fixed dural
  structures
• Transtentorialm or uncal herniation
• medial aspect of the temporal lobe (uncus)
  migrates across the free edge of the tentorium
• pressure on the third cranial nerve, interrupting
  parasympathetic input to the eye and resulting in
  a dilated pupil
• Subfalcine herniation
• cingulate gyrus on the medial aspect of the
  frontal lobe is displaced across the midline
  under the free edge of the falx
• may compromise the blood flow through the
  anterior cerebral artery complexes
• Central herniation
• diffuse increase in ICP occurs and each of the
  cerebral hemispheres is displaced through the
  tentorium, resulting in significant pressure on
  the upper brainstem.
• Upward, or cerebellar herniation
• either a large mass or increased pressure in the
  posterior fossa is present and the cerebellum is
  displaced in an upward direction through the
  tentorial opening
• Tonsillar herniation
• increased pressure develops in the posterior
  fossa
• cerebellar tonsils are displaced in a downward
  direction through the foramen magnum

6
Head Injuries

• Head injuries can be classified according to the
  GCS score
• minor (GCS score gt14)
• moderate (GCS score lt13 and gt9)
• severe (GCS score lt8)
• Skull base fracture
• Raccoon eyes
• Battle sign (after 8-12 h)
• CSF rhinorrhea or otorrhea
• Hemotympanum
• A full neurological examination should follow
• Visual acuity in an alert patient
• Pupillary light reflexes, both direct and
  consensual
• Retinal detachment or hemorrhages or papilledema
• Spinal tenderness and, if the patient is
  cooperative, limb movements
• Motor weaknesses, if possible, and gross sensory
  deficits
• Reflexes, plantar response
• Carotids for bruit, indicating possible carotid
  dissection

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Minor Head Injuries

• Minor head injuries (GCS score gt14), assess
  whether a skull radiograph is indicated
• Indications for skull radiographs
• History of loss of consciousness or amnesia
• Scalp laceration (to bone or gt5 cm)
• Violent mechanism of injury
• Persisting headache and/or vomiting
• Significant maxillofacial injuries
• If the radiographic findings are unremarkable,
  the patient can be discharged home with head
  injury instructions.
• The patient should be admitted if any
  difficulties in assessment occur
• Possible drug or alcohol use
• Epilepsy
• Attempted suicide
• Preexisting neurological conditions (eg,
  Parkinson disease, Alzheimer disease)
• Patient treated with warfarin or who has
  coagulation disorder
• Lack of responsible adult to supervise
• Any uncertainty in diagnosis

8
Moderate Head Injuries

• Moderate head injuries (GCS score lt13 and gt9)
• All patients with moderate head injury should
  undergo CT scan of the head and should be
  admitted to the hospital
• A patient with a moderate head injury and normal
  CT scan findings should improve within hours of
  admission
• If no improvement is noticed, the CT scan should
  be repeated
• When admitting patients with minor or moderate
  head injuries without intracranial pathology, the
  following guidelines apply
• Neurological observations should be performed
  every 2 hours
• The patient should take nothing by mouth until
  alert
• Start intravenous administration of 0.9 sodium
  chloride solution
• plus potassium chloride if the patient is
  vomiting
• Mild analgesics and antiemetics

9
Severe Head Injuries

• Severe head injuries (GCS score lt8)
• After stabilization, patients with severe head
  injuries (GCS score lt8) should undergo a CT scan
  of the head
• ICU is imperative for management of intracranial
  pathology and ICP
• Take immediate measures to lower the ICP
• The head should be elevated (30-45)
• Keep the neck straight, and avoid constriction of
  venous return
• Maintain normovolemia and normal BP (mean BP gt90
  mm Hg)
• Ventilate to normocapnia and avoid hypocapnia
• Use light sedation and analgesia
• Consider administration of mannitol

10
Emergency Surgical Treatment

• Burr holes are made primarily for diagnostic
  purposes because most acute hematomas are too
  concealed to be removed through the hole and the
  most common intracranial hematoma is subdural
  rather than extradural
• Making burr holes can help achieve modest
  decompression, and ideally, the physician should
  be prepared to proceed to a full trauma
  craniotomy
• Criteria for emergent exploratory burr holes are
  as follows
• No CT scan facilities are immediately available
• No neurosurgical referral center is immediately
  available
• The patient is deteriorating rapidly, with one
  pupil fixed and dilated, and the patient does not
  respond to mannitol
• The patient is dying from brain stem herniation
• Procedure
• Place burr holes along the possible line of a
  trauma craniotomy and on the side of the dilating
  pupil or the pupil that dilated first
• Start just in front of the ear (1-1.5 cm) and
  above the zygomatic arch
• If no hematoma is encountered, consider opening
  the dura, especially if a bluish discoloration
  suggests a subdural hematoma

11
Spinal Injuries

• The vast majority (gt70 in adults and gt60 in
  children) of spinal injuries involve the cervical
  spine, the most mobile part of the vertebral
  column
• In children, the upper cervical spine (between C2
  and the occiput) is more commonly injured
• In adults, the middle-to-lower cervical spine is
  the most common casualty
• Because of the likelihood of spinal injury, any
  patient who incurs trauma should be treated as
  having potential spinal injury until radiographic
  and clinical evidence indicates otherwise
• Immediate immobilization of the cervical spine in
  the appropriate collar and immediate
  immobilization of the rest of the spine on a
  spinal board
• Imaging of the spine should include at least
  plain x-ray films of the cervical spine
• When a spinal injury is strongly suggested, ie,
  due to the mode of injury or because of
  indicative findings on the x-ray film, a CT scan
  of the spine should be performed next

12
Management

• Full clinical examination and assessment should
  follow initial stabilization
• Beware of neck extension if intubation is needed
• Check palpable steps over the whole spine during
  the secondary survey
• Check for clinical signs of cord injury
• Bladder (catheterization may be necessary)
• Be aware of the possibility of spinal shock
• Fluid administration to correct imbalances
• Pressor agents, if necessary to maintain a mean
  arterial pressure greater than 90 mm Hg
• Plain lateral x-ray films of the cervical spine
  should be the least of the investigations
  performed
• If clinical or radiological evidence of a spinal
  injury is present, the immediate management of
  the patient following stabilization includes
  analgesia, full imaging, and consultation with
  spinal surgeons
• An absence of radiological evidence confirming a
  spinal injury should not lead to a relaxation of
  precautions until the patient is lucid and
  cooperative enough to move all limbs and report
  any areas of excessive tenderness
• Spinal cord injury without radiographic
  abnormality (ie, SCIWORA) occurs in approximately
  2-4 of spinal injuries
• Common types of injury
• Atlantooccipital dislocation These are almost
  universally fatal, but prompt recognition and
  stabilization can be very important
• Atlas fractures Depending on the type, most are
  treated conservatively
• Axis fractures These are difficult to treat due
  to high nonunion rates, but most require some
  form of internal fixation
• C3-T1 injuries Early reduction and alignment are
  important. Decompression of the spinal cord is
  advocated for patients with incomplete injuries

13
Methylprednisolone

• The National Acute Spinal Cord Injury Studies
  (NASCIS) I and II published in the 1990s
• Demonstrated significant benefit in administering
  high doses of methylprednisolone early after a
  spinal cord injury (within 8h)
• The dose is 30 mg/kg IV over 15 minutes, followed
  by 5.4 mg/kg/h via continuous intravenous
  infusion over 24 hours.
• The NASCIS I and II trials have received
  significant criticism with regards to both their
  design and the possible benefit-to-risk ratio. No
  full consensus has been reached on the use of
  methylprednisolone in persons with acute cord
  injury
• Steroids are not routinely recommended for severe
  head injury patients
• Recently it has been explored in a large,
  randomized international trial supported by the
  Medical Research Council
• This study was halted 6 months early because no
  specific benefit was noted in patients receiving
  steroids, while a slight increase in comorbidity
  was noted

14
Hypertonic Saline vs Mannitol

• Hypertonic saline (7.5) versus mannitol a
  comparison for treatment of acute head injuries
• J Trauma.  1993 35(3)344-8 (ISSN 0022-5282
• Department of Surgery, University of California,
  Davis, Sacramento 95817
• Elevated ICP (20-25 mm Hg) was produced by
  inflating an epidural balloon for 1 hour
• Bolus of 250 mL of either HS (n 7) or MAN (n
  7) and monitored for 2 hours
• No significant differences in hemodynamic
  variables were noted between groups. The ICP
  decreased to the same degree in both groups
  during the 2 hours of observation
• The 7.5 NaCl was equally effective in treating
  elevated ICP caused by a space-occupying lesion
  when compared with 20 mannitol
• Hypertonic saline has the additional benefit of
  rapid cardiovascular resuscitation of associated
  hemorrhagic shock with small-volume infusion
• Efficiency of 7.2 hypertonic saline
  hydroxyethyl starch 200/0.5 versus mannitol 15
  in the treatment of increased intracranial
  pressure in neurosurgical patients a randomized
  clinical trial ISRCTN62699180
• Crit Care. 2005 Oct 59(5)R530-40
• Department of Anesthesia and Critical Care,
  Martin-Luther-University Halle-Wittenberg, Halle,
  Germany
• Forty neurosurgical patients at risk of increased
  ICP were randomized to receive either 7.2
  NaCl/HES 200/0.5 or 15 mannitol at a defined
  infusion rate, which was stopped when ICP was lt
  15 mmHg
• Both drugs decreased ICP below 15 mmHg
• The mean arterial pressure was increased by 3.7
  during the infusion of 7.2 NaCl/HES 200/0.5 but
  was not altered by mannitol
• CPP increased by the same amount
• The mean effective dose to achieve an ICP lt15
  mmHg was 1.4 ml/kg for 7.2 NaCl/HES 200/0.5 and
  1.8 ml/kg for mannitol

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Antiseizure drugs

• A randomized, double-blind study of phenytoin
  for the prevention of post-traumatic seizures
• N Engl J Med 1990 Aug 23 323(8) 497-502
• Department of Neurological Surgery, University of
  Washington, Seattle 98104
• 404 eligible patients with serious head trauma
• phenytoin (n 208) or placebo (n 196) in a
  double-blind fashion
• An intravenous loading dose was given within 24
  hours of injury
• Serum levels of phenytoin were maintained in the
  high therapeutic range
• Follow-up was continued for two years
• Day 0-7
• 3.6 percent of the patients assigned to phenytoin
  had seizures
• 14.2 percent of patients assigned to placebo had
  seizure
• Day 8-365
• 21.5 percent of the phenytoin group had seizures
• 15.7 percent of the placebo group had seizures
• Year 1-2
• 27.5 percent of the phenytoin group had seizures
• 21.1 percent of the placebo group had seizures
• Phenytoin has a beneficial effect by reducing
  seizures during the 1st week after severe head
  injury