HEAD INJURY
The brain and spinal cord exist within a rigid compartment defined by the skull, vertebral bodies, and dura mater. The advantage of housing as vital and delicate structure as the CNS in a protective environment is obvious. On the other hand, such rigid confines provide very little room for brain parenchymal expansion. A number of disorders may upset the delicate balance between brain parenchymal mass and the fixed boundaries of the intracranial vault. trauma was the major causeBrain edema : brain parenchymal edema indicates the presence of increased water content within the brain parenchyma categorized as vasogenic edema or cytotoxic edema. 1-Vasogenic edema : occurs when the integrity of the normal blood-brain barrier is disrupted allowing fluid to escape from the vasculature into the interstitial space of the brain (interstitial edema). the absence of significant lymphatic drainage in the brain greatly impairs the resorption of excess extracellular fluid. 2- Cytotoxic edema : increase in intracellular fluid (intracellular edema) secondary to cellular injury energy failure at the cellular level is associated with abnormalities of ion transport, which result, in turn, in the accumulation of increased amounts of water within the cell.
MORPHOLOGY The edematous brain is softer than normal and often appears to "overfill" the cranial vault. In generalized edema, the gyri are flattened, the intervening sulci narrowed, and the ventricular cavities compressed
Herniation : The open cranial sutures in infants and young children permit some accommodation of increases in intracranial pressure. In older children and adults, however, elevated intracranial pressure is poorly tolerated, owing to the rigid nature of the cranial vault. types of herniation includes : 1-Transtentorial (uncal gyral, mesial, temporal) herniation : medial aspect of the temporal lobe is compressed against the free margin of the tentorium cerebelli. the third cranial nerve and its parasympathetic fibers are compressed, resulting in pupillary dilation and impairment of ocular movements on the side of the lesion. the posterior cerebral artery is compressed, resulting in ischemic injury to the territory supplied by that vessel, including the primary visual cortex.
2- Subfalcine (cingulate gyrus) herniation : occurs when unilateral or asymmetric expansion of the cerebral hemisphere displaces the cingulate gyrus under the falx cerebri. this is often associated with compression of branches of the anterior cerebral artery, manifested by weakness and/or sensory abnormalities in the leg, caused by ischemic injury of portions of the primary motor and/or sensory cortex. 3- Tonsillar herniation : refers to displacement of the cerebellar tonsils through the foramen magnum. this pattern of herniation is life-threatening because it causes brain stem compression and compromises vital respiratory centers in the medulla oblongata. brain stem herniation is often accompanied by hemorrhagic lesions in the midbrain and pons, termed secondary brain stem, or Duret, hemorrhages caused by kinking of penetrating branches of the basilar artery with resultant necrosis and hemorrhage in the distribution of those vessels
Duret hemorrhages
Types of herniationsCENTRAL NERVOUS SYSTEM TRAUMA : Head injury the so called "silent epidemic" is the leading cause of death and long-term disability 80% of head injuries categorized as mild head injury. 20% categorized as moderate & sever head injury. Head injury account one fourth of all accidental deaths mortality rate for moderate head injury was 10% mortality rate for sever head injury was 30% Among survivors 20% suffer from severe long-term disability motor vehicle crashes remain the leading cause under 65 years falls are leading cause in elderly & pediatric age group 60% of gunshot victims die from their injuries
Clinical classification : 1- skull fractures : - with or without brain damage - not direct cause of neurological disability - includes : a- vault fractures ( linear & depressed ) b- basilar fractures 2- focal brain injuries : - 1/2 of sever brain injuries - 2/3 of death associated with brain injury - macroscopically visible damage to brain paranchyma - limited to a well-defined area - incudes : a- contusion b- subdural hemorrhage c- epidural hemorrhage d- intracerebral hemorrhage 3- diffuse brain injuries: - wide spread brain dysfunction - without macroscopically structural damage - 40% of patient with sever head injury - 1/3 of death associated with brain injury - most prevalent cause of persistent neurological disability - not necessary structural ( concussion ) - widespread damage to axons ( diffuse axonal injury )
Mechanism of head injury: complex mechanical loading A- static loading : - uncommon - load slowly , more than 200 ms - squeezing or slow crushing - cause vault or base fractures B- dynamic loading : - common - rapid load , less than 50 ms - two types : 1- Impulsive load : head set into motion or moving head arrested no impact or contact force called inertial force 2- impact load : ( more common ) combination of contact & inertial forces
- contact force cause group of mechanical events near & distant from point of impact - vary with size & magnitude of impact - large object cause linear fracture - small object cause depressed fracture , penetration & damage - shock waves cause brain distortion , damage & hemorrhage So end result was 3 types of strains : A- Tention B- Compression C- Shearing That affect : Bone ------------ fracture Vascular tissue -------- hemorrhage Brain tissue -------- contusion
mechanistic types of head injury: 1- Contact injuries : not cause diffuse brain injuries A- local contact effects : - linear & depressed fracture - basilar fracture - epidural hemorrhage ( vascular damage ) - coup contusion ( brain damage ) B- remote contact effects : - remote vault fracture (impact over thick bone by broad object) - remote basilar fracture ( propagation of fracture ) - countercoup contusion ( tensile load away from contact ) - intermediate coup ( shock waves cause brain injury on nonconvexity surface ) - intracerebral hemorrhage (shock waves damage vasculature)
2- Inertial injuries : acceleration & deceleration injuries cause functional & structural damage - cerebral concussion (widespread disturbance of brain function) - diffuse axonal injury (widespread disturbance of brain structure) - countercoup contusion ( tensile strain ) - intermediate coup contusion - subdural hemorrhage ( tensile strain ) - intracerebral hemorrhage ( tensile strain ) - not cause fracture & epidual hemorrhage Brain injury result from : 1- primary insult : contusion , laceration , bone fracture , diffuse axonal injury 2- secondary injury : intracranial hematomas , edema , hypoxia , ischemia
Skull fractures : open or closed fractures linear or depressed fractures vault or base fractures Linear fractures : occur distant from impact occur at site Depressed fractures : from localized force may be stellate or comminuted may lacerate dura & underlying brain Diastatic fractures : linear fractures along suture lines cause separation of cranial sutures Base fractures : through cripriform plate into paranasal sinuses (CSF rhinorrhea) through petrous part of temporal lobe into mastoid air cells or austachian tube (CSF otorrhea)
Epidural ( extradural ) hematoma ( EDH ) : majority traumatic usually acute but may be chronic caused by laceration of branches of meningeal arteries typically lens shape usually located in temporal or frontal regions association with overlying skull fracture in 65-90% compress the subjacent dura and underlying brain associated lesions ( contusion ,laceration ,SDH ) in 1/3 of patient blood typically clotted ( not liquefied as in SDH ) true encapsulation only in chronic form(common in chronic SDH) may produce uncal and tonsillar herniation, brain stem compression & death patients have a "lucid interval" immediately after injury, followed by progressive loss of consciousness hematomas expand rapidly ( bleeding is arterial in origin ) necessitating prompt surgical intervention
Subdural hematomas ( SDH ) : more common than EDH collections of blood between dura mater and arachnoid mater caused by disruption of bridging veins that extend from the surface of the brain to the dural sinuses occur mostly over the cerebral convexities subdivided into : a- acute SDH: within 3 days ( clotted blood ) b- subacute SDH: 3 days – 3 weeks ( clotted & liquefied blood ) c- chronic SDH: after 3 weeks ( liquefied blood )
Acute subdural hematomas : usually associated with a clear history of trauma they may be unilateral or, particularly in infants, bilateral frequently associated with other focal traumatic brain lesions ( contusion , laceration ) high mortality rate ( 60-70% ) often associated with skull fracture In contrast to the flattened convexities seen in epidural hematomas, the gyral contours are usually preserved swelling of cerebrum on side of hematoma ----- mass effect As hematoma enlarges various forms of herniation, may occur the onset of symptoms is slower than with epidural hematomas hematomas are gradually liquefied and demarcated from brain by a reactive "neomembrane" ---- chronic subdural hematomas
Chronic subdural hematomas : less frequently associated with clear history of trauma than are acute lesions often associated with brain atrophy, renders bridging veins more susceptible to tearing traumatic episodes may be so trivial to notice they are often bilateral composed of liquefied blood separated from the inner surface of dura mater and underlying brain by "neomembranes“ ( encapsulated ) clinical symptoms include altered mental status, sometimes accompanied by focal neurologic deficits may result from nontraumatic lesion ( rupture aneurysm )
Subarachnoid hemorrhage ( SAH ) : common lesion resulting from trauma often trivial but may be massive & life-threatining always associated with cortical contusions block the exit of CSF from ventricles or impend absorption by packing arachnoid granulation --- hydrocephalus --- raised ICP --- herniation & secondary brain lesions Intraparanchymal hemorrhage : usually multiple & more common in frontal & temporal lobe deep in gray matter , but uncommon in basal ganglia / internal capsule areas majority accompanied by cortical contusions & lacerations high association with membrain hemorrhage ( SDH & SAH ) uncommon associated with EDH commonly accompanied skull fractures
Contusion : hemorrhages in the superficial brain parenchyma ( bruises ) pial – glial membrain intact caused by blunt trauma often involve crown of gyrus tend to be wedge-shaped with apex extend into parenchyma the overlying skull may contain a fracture, but it is often intact types include : a- coup : blunt force applied to an immobile head (e.g. hammer ) contusions in area immediately beneath impact b- contrecoup : mobile head hits a broader & hard surface ( head striking the floor in a fall ) contusions remote from & directly opposite to impact c- intermediate coup : midway between impact & opposite site d- fracture contusion : immediately below fracture line e- herniation contusion : contusion of medial portion of temporal lobe intranstentorial herniation
Lacerations : disruption of brain integrity at macroscopic level tearing of the superficial layers of the brain pial – glial membrane disrupted It is an important cause of traumatic subarachnoid hemorrhageconcussion : a transient loss of consciousness sometimes accompanied by seizures recovery over a period of hours to days without sequelaeDiffuse axonal injury ( DAI ) : cause of most cases of post-traumatic dementia responsible for most cases of persistent vegetative state result from sudden deceleration and/or acceleration forces stretch or tear of nerve cell processes within the white matter grossly it may produce only minimal changes in severe cases, there are areas of hemorrhage, most commonly in the corpus callosum and dorsal areas of the brain stem
Neurological examination in trauma : 1- vital signs & general examination : pulse rate : tachycardia ( shock ) , bradycardia ( raised ICP ) blood pressure : hypotension ( shock ) ,hypertension ( raised ICP ) respiration : cheyne-stokes breathing ( raised ICP ) chest & abdominal injury had priority to head injury 2- state of consciousness : GCS : A - eye opening : spontaneous ( 4 ) , to speech ( 3 ) to pain ( 2 ) , none ( 1 ) B - best motor response : obey ( 6 ) , localize ( 5 ) , withdraws ( 4 ) , flexion ( 3 ) , extension ( 2 ) , none ( 1 ) C - best verbal response : oriented ( 5 ) , confused ( 4 ) , inappropriate words ( 3 ) , incomprehensive sounds ( 2 ) none ( 1 )
3- Cranium examination : a- evidence of skull base fractures : 1- Raccoon's eyes : periorbital ecchymosis 2- Battle sign : postauricular ecchymosis 3- CSF rhinorrhea / otorhea 4- hemotympanum b- scalp contusions & lacerations c- facial fractures 4- pupils & cranial nerves examination : a- pupils : size & reaction b- vision : if unconscious reaction to light c- fundoscopic examination : papillodema , retina hemorrhage d- extraoccular muscles movement : if unconscious doll`s eye e- corneal response : 5th & 7th cranial nerves f- hearing : if unconscious caloric test for vestibular function g- 9th & 10th : gag reflex , swallowing , vocal cord function
5- Motor examination : if patient cooperative check all 4 limbs if patient unconscious check response to painful stimuli 6- sensory examination : if patient cooperative 7- reflexes : a- deep tendon reflexes : if present in paralysed limb indicate CNS injury not peripheral injury b- Babinski`s sign + ( up going toes ) 8 - cervical spine examination : fracture , sublaxation , dislocation , cord injury 9- examination of chest , abdomen & limbs
Radiological evaluation : A- Skull X ray : 1- linear or depressed fractures 2- penetrating missile injuries 3- pineal gland shift 4- pneumocephalus 5- air- fluid level in air sinuses 6- not detect raised ICP B- cervical spine X ray : mandatory as 1/3 of head injured patient had cervical injury C- Brain CT scan : superior to MRI in trauma & acute brain insult ( CVA ) rapid procedure better for metallic foreign body better for skull fracture assessment
CT scan used for diagnosis of : 1- hemorrhage & hematoma : a- EDH : biconvex ( lens ) shape b- SDH : crescent shape c- SAH : thin layer over convexity, filling sulci & basal cysterns d- ICH : inside brain paranchyma e- IVH : inside ventricular system 2- skull fractures : a- basal skull fractures b- orbital fractures c- facial fractures d- calvarial fractures ( linear , stellate , depressed , diastatic ) 3- ischemic infarction 4- pneumocephalus ( indicate basa skul fractures ) 5- shift of midine structures ( from hemorrhage or edema ) 6- hydrocephalus
D - Brain MRI : 1- better for visualization of brain stem injuries 2- detect small white matter changes (e.g. punctate hemorrhage in corpus callosum seen in DAI ) 3- better for localize & assess extent of contusion & hematoma ( multiplanar images ) 4- better for subacute injuries ( SDH ) Disadvantages : a- long imaging time b- not appropriate for acute hemorrhage c- bony fractures not well seen d- SAH not well seen e- small pneumocephalus may be missed
Management of head injury :Initial management : 1- ABC system is golden point 2- transport of patient ( avoid farther trauma ) 3- hypoxia & hypercapnia should be avoided 4- avoid shock & maintain adequate cerebral perfusion 5- early intubation & respiration support in severely injured patientIntracranial pressure monitoring : normal ICP in adult < 10 – 15 mm. hg. children 3 – 7 mm. hg. infant 1.5 – 6 mm. hg. ICP > 20 mm. hg. --- high ICP > 40mm. hg. --- serious & dangerous raised ICP cause Cushing`s triat a- hypertesion b- bradycardia c- respiration irregularity
Causes of traumatic intracranial hypertension : 1- cerebral edema 2- hyperemia ( vasomotor paralysis ) 3- mass : a- EDH b- SDH c- ICH d- foreign body ( bullet ) e- depressed fracture 4- hydrocephalus 5- hypoventilation ( hypercapnia ---- vasodilatation ) 6- systemic hypertension 7- increase tone & valsalva maneuver from agitation or posturing 8- sustained post – traumatic epilepsy ( status epilepticus ) Types of monitors : a- intraventricular catheter b- intraparanchymal catheter c- subarachnoid scrow d- subdural catheter e- epidural catheter f- fontanometry ( in infant )
complications of ICP monitors : 1-infection 2-hemmorrhage 3-malfunction 4-malposition 5-cost Treatment of raised ICP : 1- head up posture 2- hyperventilation ( hypocapnia --- vasoconstriction --- low cerebral volum --- decrease ICP ) 3- osmotic diuretic ( manitol ) : 0.25 – 1 g/kg 4- loop diuretic ( furosamide ) : 0.5 mg/kg 5- avoid hyperglycemia ( cause brain edema ) 6- high dose barbiturate therapy ( phenobarbital & thiopental ) in sever head injury & if no medical contraindication 7- surgical decompression SDH & EDH > 1 cm thickness hemorrhagic & ICH with progressive deterioration decompressive cranietomy if ICP not control by other ways
Nutritional support & rehabilitation nasogastric feeding total parentral nutrition may start early reduce infections & mortaity rehabilitation during 1st week , include chest physiotherapy Specific treatment : prophylaxis against epilepsy prophylaxis against cushing`s ( stress ) ulcer aggressive control of fever IVF isotonic ( N/S ) catheterazation prophylactic AB : in open skull fractures ( depressed or basal fractures )