CNS: Trauma

CNS: Trauma

 

Abrasion (scratch) Epidermis (surface) layer only All shapes
Laceration Dermis layer (deep) Jagged edges
Incised Wound Dermis layer (deep) Straight wound (stab)

 

Skull Injuries

Scalp Laceration Due to tight apposition of the scalp (skin) to the calvarium(skull),

scalp lacerations easily occur, (bleed in large amounts)

  • Scalp / Face vessels communicate freely with veins of meninges:has chance for Meningitis to occur (infection)
Brain tissue damage can occur without external / associated skull fracture (g-force)

  • Contusions
  • Laceration
  • Harmorrhage

Careful autopsy examination of the skull, palpate scalp through hair (esp. for ppl with thick hair)
Skull fracture Break in the cranial bone

  • Bleeding in ears / orbit (orbital fracture – eyes)

“Black eyes” (swollen eyelids) is caused by bleeding into eye socket :

  1. Orbital fracture
  2. CSF leak from nose fracture (ethmoid bone)

Base of skull injury-Inhalation of blood  (blocks trachea-clot)
Vertex (top-back) injury usually does not occur in a fall

  • (don’t fall on the top of head)
  • Suspicion of assault case (blow to back of head)

 

Concussion

Definition: “A transient paralytic state due to head injury which is of instantaneous onset, does not show any evidence of structural cerebral injury and is always followed by amnesia from the actual moment of the accident”

  • Temporary paralysis
  • Occurs right away
  • Amnesia (forgets either events before or after: retro or anterograde)

Common occurrence, but can be avoided.

  • Sequel to any significant mechanical insult to brain

 

Length of concussion (loss of consciousness) consciousness is a rough guide to the degree of cerebral pathology

  • Longer = more severe
  • But short ≠ not severe

Actual Cause of concussion effect is unknown: some mechanical process temporarily disrupts the function, if not necessarily the structure, of the brain

 

Brain tissue damage (without external wounds)

 

Chronic Traumatic Encephalopathy – CTE
CTE presents like parkinson’s/dementia:
Is a sports-related neurological injury due to repeated bouts of concussion, especially repetitive concussion, often mild!

  • Boxing / American football / martial arts / parachuting / soldiers
Clinical features: memory disturbances, behavioural and personality changes, Parkinsonism, speech and gait abnormalities (depends on area affected)
Pathology: atrophy of the cerebral hemispheres, medial temporal lobe, thalamus, mamillary bodies and brainstem, with ventricular dilatation
Treatment: Decrease no. of concussive episodes, limit exposure to trauma with severe penalties for deliberate blows to the head, adherence to strict return-to-play guidelines, avoid second concussive episode at all costs within weeks of the first, give up the sport completelyNote: treatment plans are based on prevention of further injury, as opposed to treatment of actual injury

 

Second Impact Syndrome
Case: Rugby player suffers concussion injury but was allowed back on the field, and dies after sustaining second concussive injury in the same match

Theory: 1st injury has affected arterioles ability to dilate and maintain pressure in brain

  • 2nd injury: >> rapid formation of oedema in brain

Hence, before 1st injury heals completely (weeks), patients should avoid another injury (skull)

 

Diffuse Axonal Injury (DAI)
Primarily a non-impact rotational acceleration-deceleration phenomenonà → RTA   (G-force)

Most significant factor is probably deformation by stretching

  • No gross pathology seen (external):
  • Examine brain histologically post 10-14 days fixation
  • See “retraction globes” due to axonal disruption on microscopy
  • Microscopy diagnosis

If there is no gross wounds → refer to neurologist for microscopic scan

DAI most common cause of long term morbidity from head injury

 

Haemorrhage

Dura Mater 2 layers
Arachnoid Vascular; Sheaths of arachnoid follow vessels into the brain
Pia Not a true membrane; a surface network of glial fibres inseparable from the underlying brain
Extradural blood between skull and dura mater.

– Common cause: fracture to temporal bone.
Subdural Blood between dura and arachnoid mater.

Simple fall (often in elderly) – Repeated Minor trauma
Subarachnoid blood beneath the leptomeninges (flow of CSF)

– Trauma, ruptured berry aneurysm.
Intracerebral Blood within brain tissue

Hypertension, sometimes trauma (burst of blood vessels)

 

[ Intracerebral : in brain tissue ]

[ Intracranial : Bleeding in Cranial Vault (spaces between skull and brain) = All bleeds types ]

 

Extradural Hemorrhage

Cause Trauma to the Squamous/ Temporal bone – Blows to the temporal area
Prognosis may have no significant trauma to underlying brain; detected early = good prognosis
Clinical Presentation
  1. Trauma
  2. Concussion
  3. Lucid interval (slight regain of consciousness)
  4. Loss of consciousness
  5. Coma / Death
CT Scan Disc shape pool of blood (edge of skull)
Pathology Fracture of thin temporal bone with tearing of Middle Meningeal

Artery (not middle temporal artery)

– Arterial bleed; MMA is outside the Dura

Separation of Dura from bone – 6-12 hours

Accumulation of a large haematoma outside the dura → compression of the adjacent cerebral hemisphere

(death if accumulation is great)

 

Subdural Haemorrhage/Haematoma (SDH)

Acute vs Chronic SDH • In elderly patients often a minor head trauma, often no skull #

• In infants, may be associated with child abuse

– Shaken baby syndrome
Pathology Bridging veins: arachnoid →  sinus (between 2 dura)

  • Makes it vulnerable to tear (dura stationary while brain shifts/oscillates in trauma)
  • Slow venous bleeding

Acute SDH: (road traffic accidents)
Chronic SDH: granulation tissue grows into the haematoma &

tries to organise and remove it.

(This granulation tissue originates from the dura rather than the brain.)
Haematoma becomes encapsulated by granulation tissue forming a thin capsule (1-3 weeks)

  • The haematoma may increase in volume byre-bleeding from granulation tissue or by in-drawing of CSF from the subarachnoid space by osmosis

Reasonably frequently an incidental finding at autopsy in older

patients

  • Dating of SDHs difficult esp. > one month post injury

Gross anatomy: rust-coloured membrane beneath dura
CT scan Jelly mass over brain (without convex/concave) shape

Local spread (one area only)

 

Acute traumatic Subarachnoid Haemorrhage (SAH)

 

Cause TRAUMATIC

Trauma to Circle of Willis vessels (internal supply to brain tissue)
Most susceptible: trauma to vertebral arteries → basal subarachnoid haemorrhage. Typically caused by blunt force to the side of the neck behind the ear (“karate chop”-type blow)

  • vulnerable where they enter foramen magnum

NON-TRAUMATIC

~Rupture of berry aneurysm (congenital)

  • Berry aneurysms are saccular aneurysms, 5-10mm diameter, usually located at bifurcations of arteries

Most common locations: anterior and posterior communicating arteries, middle cerebral artery
Associations:

  1. Hypertension
  2. Kidney: adult polycystic kidney disease (strong correlation) Note: marfans not mentioned

~Vascular Malformation (cause of SAH – rare)
CT Scan Blood tracks in all sulci of brain (spread all over)
Clinical presentation Sudden onset of “worst” headache of my life

May have history of preceding, less severe,headaches: ‘herald bleed’

Intracerebral haemorrhage (AKA haemorrhagic stroke)

Causes
  1. Hypertension (non-traumatic) – most common
  2. Cerebral amyloidosis (abnormal protein accumulation)
  3. coagulopathies,
  4. anticoagulant/thrombolytic therapy, cocaine and other sympathomimetic drugs,
  5. AV malformations, vasculitis

With hypertension, intracerebral haemorrhages tend to be in the thalamus (lateral/3rd ventricles), external capsule, pons and cerebellum and are more often occipital than frontal or temporal
With trauma, intracerebral haemorrhage may be caused by “coup” or “contrecoup” mechanisms and may be situatedanywhere within the hemispheres

 

 

Summary

  • Significant trauma to the head involves lacerations,contusions and skull fractures
  • Concussion is a common clinical syndrome after any significant mechanical insult to the brain
  • Diffuse axonal injury: most common cause of long-term morbidity post-head injury
  • Intracranial haemorrhage: extradural, subdural,subarachnoid, intracerebral

 

Note the arterial locations

Artery Location Haemorrhage
Middle Meningeal Artery External to dura

(dura-skull)

 Extradural H
Veins (non-sinus) From arachnoid into sinus (dura) Subdural H
Middle Temporal artery Arachnoid space
(any large arteries)		 Subarachnoid H
Circle of Willis
Vertebral arteries
Collateral arteries (small) In brain tissue Intracerebral H