PATHOPHYSIOLOGY OF THE NERVOUS SYSTEM. Peerayut Sitthichaiyakul, M.D. Department of Pathology, Faculty of Medicine, Naresuan University

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1 PATHOPHYSIOLOGY OF THE NERVOUS SYSTEM Peerayut Sitthichaiyakul, M.D. Department of Pathology, Faculty of Medicine, Naresuan University NERVOUS SYSTEM Central nervous system Brain Spinal cord Peripheral nervous system Cranial nerves Spinal nerves Autonomic nervous system 1

2 CONTENTS Central nervous system Peripheral nervous system Central Nervous System Mechanism of brain injury Traumas Cerebrovascular diseases CNS infection Degenerative diseases Brain tumors 2

3 MECHANISM OF BRAIN INJURY Cellular Hypoxia and Ischemia Occur in most form of acute brain injury Oxygenated blood < metabolic demand Ischemia Inability to generate ATP Oxygen free radicals, excitary amino acids and inflammatory cells 2 injury 3

4 Cerebral Edema Vasogenic edema : damage of blood-brain barrier increase vascular permeability intercellular edema Cerebral infarction Intracerebral hemorrhage Brain tumor Infection : meningitis, encephalitis, brain abscess Trauma Lead poisoning Cytotoxic edema: intracellular accumulation Hypoxia : cardiac arrest Hyponatremia Hemodialysis Diabetic ketoacidosis Interstitial edema: periventricular edema Hydrocephalus 4

5 Increased Intracranial Pressure ICP is exerted by the contents of the cranium 1. brain tissue 2. cerebrospinal fluid (CSF) 3. blood Common cause of increased intracranial pressure Increased brain tissue volume: tumor hemorrhage infection Increased cerebrospinal fluid volume hydrocephalus Increased blood volume increased right atrial pressure 5

6 Brain Herniation Subfalcine herniation cingurate lobe of the cerebral hemisphere herniate through the space between falx cerebri and corpus callosum Compress anterior cerebral artery Uncal herniation Medial aspect of the temporal lobe herniate over the edge of the tentorium cerebelli Compress posterior cerebral artery Compress brain stem brain stem hemorrhage Tonsillar herniation Cerebellar tonsil herniate through the foramen magnum Compress medulla oblongata respiratory center 6

7 Hydrocephalus Noncommunicating hydrocephalus Congenital malformation Tumor Inflammation Hemorrhage Communicating hydrocephalus Subarachnoid hemorrhage Meningitis Metastasis to subarachnoid space TRAUMA 7

8 Skull Fracture Linear fracture Depressed fracture Comminuted fracture Diastatic fracture Compound fracture Location Fall while alert occipital region Fall whlie loss of consciousness : syncopal attack frontal region Clinical finding Asymptomatic Lower cranial nerve or cervicomedullary dysfunction CSF discharge fome nose or ear route of organisms to meninges 8

9 Traumatic Vascular Injury Epidural hematoma Subdural hematoma Subarachnoid hemorrhage 9

10 Epidural hematoma Associated with skull fracture Bleeding from middle minigeal artery Bleeding into space between periosteum and dura Clinical findings < 30 ml. asymptomatic ml. space-occupying lesion increased intracranial pressure compress venous sinus circulatory stagnation cerebral ischemia and edema brain herniation > 60 ml brain herniation Subdural hematoma Bleeding from bridging vein Bleeding between dura mater and arachnoid layer Acute subdural hematoma Chronic subdural hematoma Clinical findings Asymptomatic Stretching of the meninges headache Irritation of the cortex seizure Growth of fibroblasts and hyalinized connective tissue rebleeding chronic subdural hematoma 10

11 Subarachnoid hemorrhage Bleeding between arachnoid layer and pia mater Traumatic subarachnoid hemorrhage bleeding from bridging vein Other cause Ruptured berry aneurysm : most common cause Ruptured occur at any time ⅓ associated with acute increase in intracranial pressure Ruptured arteriovenous malformation CEREBROVASCULAR DISEASES 11

12 Third leading cause of death Leading cause of serious disability Risk factors: Hypertension Diabetes mellitus Hyperlipidemia Cigarette smoking Advancing age Family history Two process depend on pathophysiology 1. Ischemia and infarction - Global cerebral ischemia/infarction hypoxic encephalopathy - Focal cerebral ischemia/infarction obstruction of local blood supply 2. Hemorrhage 12

13 Cerebral Infarction Global cerebral ischemia (hypoxic/ischemic encephalopathy) Shock Cardiac arrest Severe hypotension Survive vegetative state Severe impaired neurologic function, coma Focal cerebral ischemia 1. thrombosis 2. embolism Thrombosis Atherosclerosis Arteritis from syphilis, TB, Toxoplasma, CMV Collagen-vascular diseases Hematologic diseases with hypercoagulable states Drug abuse 13

14 Embolism Cardiac mural thrombi: most common cause myocardial infarction valvular heart diseases atrial fibrillation Atheromatous plaque Paradoxical emboli Emboli associated with cardiac surgery Tumor emboli Fat emboli Air emboli Clinical features Neurologic deficit Depend on Site of obstruction Size of infarction Small cerebral infarction asymptomatic focal neurologic deficit Large cerebral infarction cerebral edema brain herniation 14

15 Spontaneous Intracerebral Hemorrhage Hypertension : the most common cause arteriosclerosis of blood vessels small microaneurysm location of hematoma : basal ganglia, internal capsule, thalamus, cerebellum and pons Other cause: tumor, vascular malformation, vasculitis, coagulative disorder CNS INFECTION 15

16 Route of entry for organisms 1. Hematogenous spreading: most common route 2. Direct implantation 3. Local extension 4. Spread via peripheral nervous system Meningitis Bacteria: most common origin adult Streptococcus, Neiseria children Hemophilus newborn E.coli, Group B Streptococci Virus Fungus Parasite 16

17 Reach the CNS by hematogenous route or extension from adjacent site Headche, fever, stiff neck and signs of cerebral dysfunction Diagnosis lumbar puncture neutrophils glucose level protein level 17

18 Encephalitis An inflammation of the brain parenchyma Virus are the most often pathogen Arbovius encephalitis Japanese B encephalitis Western equine encephalitis animal normal host human accidental host Herpes simplex encephalitis type 1 adult infected by direct contact nerve ganglion encephalitis type 2 newborn acquire the organisms from birth canal encephalitis Bacteria, fungus, parasite 18

19 Brain Abscess Localized collection of pus within the brain parenchyma Most common organism bacteria streptococci staphylococci anaerobes DEGENERATIVE DISEASES 19

20 Cerebral cortex Alzheimer disease Pick disease Basal ganglia and brain stem Parkinson disease Huntington disease Motor neurons Amyotrophic lateral sclerosis (motor neuron disease) Alzheimer Disease Most common cause of dementia Aβ critical molecule in the pathogenesis of the disease Aβ peptide are derived from amyloid precursor protein (APP) on the cell surface APP are cleaved by secretase Aβ peptide endocytosis aggregate Aβ fibrils Aβ neurotoxic cellular response oxidative damage 20

21 Clinical findings Symptomatic cause running more than 10 year Forgetfullness Dementia : gradual loss of memory and cognitive function Incontinent, mute, unable to walk Bedridden Pneumonia death Parkinson Disease Second most common neurodegenerative disease Degeneration of dopaminergic neurons in substantia nigra Cause idiopathic Movement disorders voluntary movement involuntary movement 10-15% dementia 21

22 BRAIN TUMORS Incidence 10-17:100,000 Unique characteristic Distinction between benign and malignant is less evidence : benign tumor may be poor prognosis Limitation of surgical resection without neurologic deficit Anatomic site of the tumor can have lethal consequence Pathway for spread is subarachnoid space, rarely metastasize outsize the CNS 22

23 Clinical signs and symptoms Primary effect Location Size increase intracranial pressure Secondary effect Edema Disturb cerebrospinal fluid drainage hydrocephalus Herniation WHO classification 1999 Tumors of the neuroepithelial tissue Astrocytic tumors astrocytoma glioblastoma (multiforme) Oligodendroglial tumors oligodendroglioma Ependymal tumors ependymoma 23

24 Tumor of cranial and peripheral nerve Schwannoma Neurofibroma Tumors of the mininges Meningioma Tumors of the sellar region craniopharyngioma Metastasic tumor Glioblastoma (multiforme) : GBM Most severe glial cell tumor Most frequent brain tumor Peak incidence between yrs Cerebral hemispheres Seizure, headache, neurological deficit 24

25 Metastasic Tumors 50% of intracranial tumors Five most common primary site: Lung Breast Skin (maligant melanoma) Kidney Gastrointestinal tract Extensive cerebral edema increased intracranial pressure Neurocutaneous syndromes Group of inherited disease Autosomal dominant Multiple harmatomas or neoplasms, particular CNS and skin Neurofibromatosis type I, type II Tuberous sclerosis von Hippel-Lindau disease 25

26 Neurofibromatosis type I 1:3,000 Neurofibromas Gliomas of optic nerve Pigmented nodule of iris (Lisch nodules) Cutaneous hyperpigmented macules (café au lait spots) Peripheral Nervous System Inflammatory (immune-mediated) neuropathies Traumatic neuropathies Tumors of the peripheral nervous system 26

27 INFLAMMATORY NEUROPATHIES Acute inflammatory demyelinating polyradiculoneuropathy (Guillain-Barré syndrome) Acute and subacute paralytic illness Ascending paresthesia and paralysis (from leg to arm) bedridden respiratory failure Autoimmune diseases Associated with viral infection or another immunologic stimulus TRAUMATIC NEUROPATHY 27

28 Laceration Avulsion Compression neuropathy (Entrapment neuropathy) Carpal tunnel syndrome Predisposing factor Inflammatory arthritis Excessive use of wrist joint Amyloidosis Pregnancy Hypothyroidism TUMORS OF THE PNS 28

29 Neuronal origin neuroblastoma Nerve sheath origin neurofibroma schwannoma (neurilemmoma) malignant peripheral nerve sheath tumor (malignant schwannoma) Schwannoma Arise from Schwan cell Associated with neurofibromatosis II In cranial cavity cerebellopontine angle 29

30 Neurofibroma Solitary neurofibroma Peripheral nerve Skin cutaneous neurofibroma Associated with NFI Plexiform neurofibroma Associtaed with NFI 30