CENTRAL NERVOUS SYSTEM PATHOLOGY

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CENTRAL NERVOUS SYSTEM PATHOLOGY
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CONGENITAL ANOMALIES OF CNS
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Anencephaly

• Basically a complete absence of the cerebral
  hemispheres.

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Anencephaly
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• Encephalocele and Cranial Meningocele
• Consists of a protrusion of brain or meninges
  through a cranial defect.
• Most frequent in the occipital region.

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Cranial Meningocele
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Spinal Meningeocele

• Meningeocele consists of herniation of both dura
  and arachnoid ( layer containing the blood
  vessels) through a vertebral defect, with the
  spinal cord remaining in its normal position.

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Spinal Meningeocele
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Hydrocephalus

• Definition
• This is a chronic accumulation of CSF inside the
  ventricular system leading to its dilatation and
  consequently atrophy of the brain tissue

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Hydrocephus
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• Etiology
• Increased CSF production due to choroids plexus
  papilloma
• Obstruction of CSF flow due to
• Congenital causes (non-communicating type of
  obstructive hydrocephalus due to congenital
  narrowing of ventricular foramina or aqueduct
• Acquired causes
• Meningitis
• Brain tumor or brain abscess

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• 3. Decreased CSF absorption due to
• Congenital causes congenital aplasia of the
  arachnoid villi (lining the ventricles)
• Acquired causes damage of archnoid villi in case
  of meningitis
• Thrombosis of superior sagittal sinus

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Pathology

• There is ventricular dilatation with excess CSF
• In infants, hydrocephalus leads to enlargement of
  the head due to separation of skull sutures
• In adults, hydrocephalus leads to increased
  intracranial tension which may lead ? brain
  herniation ? death

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A hydrocephalus MRI scan and a normal MRI scan
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Cerbro-vascular disease of CNS
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1. Cerebral ischemia
2. Cerebral infarction
3. Cerebral hemorrhage

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Cerebral ischemia

• Definition Decrease in blood flow to the brain
• Etiology shock,
• hypotension,
• cardiac arrest
• Types
• Generalised cerebral ischemia usually causes
  irreversible damage of brain tissue
• Transient ischemic attack usually there is
  reversible symptoms

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Cerebral infarction

• Etiology
• Thrombotic occlusion due to atherosclerosis and
  it leads to anemic white infarction
• Embolic occlusion due to thrombo-emboli from
  cardiac chambers and it leads to hemorrhagic
  infarction
• Small vessel diseases related to hypertension
  and arteriosclerosis, it leads to lacunar
  infarction i.e. lacunae (multiple small
  infarctions)

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EMBOLIZATION OF CEREBRAL ARTEY
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Acute infarction of brain
Lacunar infarction
Intermediate infarction
Old infarction
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Cerebral hemorrhage

• Classified as
• Intracerberal hemorrhage
• Epidural hemorrhage
• Subdural hemorrhage
• Subarchnoid hemorrhage

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Intracerberal hemorrhage (intraparenchymal)

• Hypertension is the most frequent predisposing
  condition.
• Other causes as
• vascular malformation especially arteriovenous
  malformations, cerebral angiopathy, neoplasms,
  vasculatides, abnormal hemostasis, hematological
  malignancies and infections

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Vascular malformations
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• Clinically
• Severe headache
• Frequent nausea and vomiting and progression of
  symptoms to coma

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Intracerberal haemorrhage (intra parenchymal)
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Epidural hemorrhage

• Always traumatic
• Usually associated with skull fracture
• Tear of dural arteries most frequently occurs in
  the middle meningeal artery
• Usually leads to cerebral herniation
• Lucid interval before loss of consciousness
  (short loss of consciousness then patient is well
  then coma)

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Epidural hemorrhage
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Sub-dural hemorrhage

• Usually traumatic in old age
• Slow haemorrhage
• Gradual symptoms
• Caused by rupture of bridging veins (from
  cerebral to sagittal sinuses)
• Predisposing conditions brain atrophy and
  abnormal haemostasis
• Clinically
• Headache, drowsiness, focal neurological deficits
  and sometimes dementia

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Sub-dural hemorrhage
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Subarachnoid hemorrhage

• Most frequent cause is ruptured berry aneurysms
  as well as trauma, abnormal haemostasis (blood
  diseases) and tumours
• Clinically
• There is sudden thunderclap headache, nuchal
  rigidity, neurological deficits on one side and
  stupor

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Sub arachnoid hemorrhage
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Diffuse sub-arachnoid haemorrhage
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BERRY ANEURYSMS

• Definition
• Thin-walled saccular out-pouchings of blood
  vessels with thinning of the vessel wall
• Most frequent cause of subarchnoid haemorrhage
• Most frequent site is the anterior circle of
  Willis at the branching points

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BERRY ANEURYSMS
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• Causes of rupture
• 1-increased blood pressure
• 2-trauma
• 3-spontaneously

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• Complications
• Sub arachnoid haemorrhage due to rupture
• Thrombosis
• Pressure on the surrounding structures

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CNS TRAUMA
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CNS TRAUMA

• Trauma of cranial cavity and brain
• Brain Concusion
• Brain contusion
• Diffuse axonal injury
• Trauma of spinal cord
• Cerebral herniation
• Sub-falcine (cingulated gyrus)
• Transtentorial (uncal)
• Cerbellar tonsillar

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A- Trauma of the cranial cavity and brain

• Brain concusion
• Change in the momentum of the head (impact
  against a rigid surface)
• Loss of consciousness and reflexes, temporary
  respiratory arrest and amnesia for the event

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• Brain contusions
• Impact of parts of brain against inner calvarias
  surfaces
• Bruising of the brain resulting from tissue and
  vessels disruption
• Site of injury crests of orbital gyri in frontal
  and temporal poles

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• Pathology
• Coup (site of injury) and countercoup site
  diametrically opposite
• Coup and countercoup develop when the head is
  mobile
• Clinically
• Acute hemorrhage of brain tissue in a wedge-
  shaped area
• Subacute necrosis and liquefaction of brain
• Remote depressed area of cortex with yellow
  discoloration

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Coup and countercoup
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OLD BRAIN CONTUSION
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• Diffuse axonal injury
• Injury to the white matter due to acceleration/
  deceleration
• Damage to the axons
• Usually there is coma after the trauma

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• B- Spinal cord injury
• Injuries are usually traumatic, due to vertebral
  displacement
• Lesions of thoracic segment ? paraplegia
• Lesions to cervical segment ? quadriplegia
• Lesions above C4 ? respiratory arrest due to
  paralysis of diaphragm

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C- Cerebral herniation

• Sub-falcine (cingulated gyrus)
• Cingulated gyrus is displaced underneath the falx
  to the opposite side
• Compression of anterior cerebral artery

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Sub-falcine herniation
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• Cerebellar tonsillar
• Displacement of cerebellar tonsils through the
  foramen magnum
• Compression of medulla ? cardiorespiratory arrest

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DIFFERENT FORMS OF BRAIN HERNIATIONS
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TO BE CONTINUED.