Nervous System 1

Stroke or Cerebrovascular Accident

Cause: occlusion of cerebral vessels by a thrombus or embolus (mostly ischemic), intracerebral haemorrhage due to ruptured blood vessel, issue external to the CNS

Risks: smoking, obesity, hypertension, diabetes, high cholesterol, genetic factors, transient ischaemic attack (mini stroke with quick symptoms that last for several hours, warning sign for major stroke)

Symptoms: numbness, weakness or paralysis, sensory deficit, loss of consciousness, severe headache, sudden blurred vision or blindness, slurred speech, unsteadiness, confusion

Brain Tumors

Gliomas

Cause: mostly metastatic and rarely primary tumours

Most common type: astrocytoma (cerebrum)

Types of astrocytoma: glioblasta multiforme, pilocytic astrocytoma and anaplasic astrocytoma

Astrocytoma: glioblasta multiforme

  • Poorly differentiated and fast growing
  • Most common glioma
  • No clearly defined margins
  • Invade locally and spread along white matter pathways
Age group: 40-60 years

Site: cerebral hemisphere


Characteristics: necrosis, haemorrhage and infiltrating mass

Survival: 10 months from diagnosis

Symptoms: neurologic deficit, headache, increased intracranial pressure (headaches, nausea, vomiting), seizures

Treatment: radiotherapy and chemotherapy (increase prognosis)

Astrocytoma: pilocytic astrocytoma
  • Cystic lesion with solid nodule of tumour in cyst wall
  • Benign
  • Children and young adults (most common benign brain tumour of children)
Site: cerebellum and floors and walls of 3rd ventricle, optic chiasm and nerves

Characteristics: slow growth

Prognosis: excellent

Astrocytoma: anapaestic astrocytoma

UNCOMMON

Neuronal tumours

Rare

Poorly differentiated neoplasms

Most common form: medulloblastoma

Age group: 3-8 years

Characteristics: cell retain primitive characteristics, fast growing, high-grade tumours, occlude flow of CSF (hydrocephalus), rarely spread outside of CSF

Site: cerebellum midline

Symptoms: vomiting, headaches, clumsiness, difficulty with intricate tasks, e.g. handwriting, gradual decline in school performance

Prognosis: good for complete resection

Meningioma

Origin: menigothelial cells of the arachnoid mater and outside the brain

Characteristics: usually solitary, well circumscribed (restricted in a limited area), highly vascular

Age group: middle aged to elderly

*Most common sites of metastatic tumours are lung, breast, melanoma, kidney and GI tract

Increased Intracranial Pressure

i.e. pressure exceeding 15mmHg within the cranial vault

Consequences: obstructs cerebral blood flow, destroys brain cells, displaces brain tissue and damages delicate brain structures

Symptoms: headache, visual changes (edema and papilledema), abnormal sensation/motor activity, abnormal body temperature, decreased level of consciousness, fontanels bulge (space between brain and infant skull) and bradycardia (slow heart rate)

Hematomas

i.e. solid swelling of clotted blood within the tissues resulting from vascular injury and bleeding

Epidural: between brain and meninges
  • At a site of fracture between skull and dura
  • Due to a damaged middle meningeal artery
  • Quick to develop after injury
Subdural:
  • Occur weeks or months after injuries
  • Caused by a tear in the arachnoid
  • Blood from small veins gets in between pia and dura mater
  • Slow to develop
  • Most common hematoma of traumatic injury
Intracerebral haemorrhage:
  • Bleeding occurs in the brain tissue itself

Seizures

Repeated occurrence: epilepsy

Cause: reduction in the inhibitory system, causing excessive excitation

Symptoms: prodome experienced by individual can help them predict a seizure, aura just before seizure

Partial Seizures

Characteristics: begin in a specific area of the brain (cerebral cortex)

Generalised Seizures

Characteristics: involve entire cerebral cortex and diencephalon

Causes: genetic, CNS disorder, intracranial haemorrhage, electrolyte imbalance, sudden alcohol withdrawals, anti epileptic therapy withdrawal, brain tumours, metabolic disorders

Absence seizures (petit mal): minor impairment of neural function where person is physically present although their mind is absent. Seizures disrupt intentional behaviour including consciousness and memory but only last 5-30 seconds with frequent occurrence per day.

Tonic-clonic seizures (grand mal seizures): most common motor seizures initiating with partial seizures. Divided into three phases:

  1. Tonic phase (few seconds): sharp tonic muscle contraction, person falls rigid to ground, forced expiration, bladder and bowel incontinence
  2. Clonic phase (few minutes): less rapid, violent jerking of face and limb
  3. Post-ictal phase (few minutes to an hour): deep unconsciousness with flaccid limbs and jaw, loss of corneal reflexes, headache, confusion and aching muscles

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