CENTRAL NERVOUS SYSTEM PATHOLOGY. DEMYLEINATING AND DEGENERATIVE DISORDERS OF CNS. DEMYLEINATING DISEASES Multiple sclerosis (M.S.)_. Definition: Chronic relapsing-remitting (complete or partial recovery then another attack) disorder of an autoimmune origin
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DEMYLEINATING DISEASES Multiple sclerosis (M.S.)_ • Definition: • Chronic relapsing-remitting (complete or partial recovery then another attack) disorder of an autoimmune origin Characterized by episodes of demylination in the brain, optic nerve and spinal cord resulting in progressive neurological deficits
Pathology: Acute lesion: • Grossly: peri-ventricular well-circumscribed plaques • Microscopically: • Loss of myelin • Phagocytosis of myelin by macrophages • Preservation of axons • Chronic inflammatory cells • Chronic lesion: • No inflammation • Axon remyleination • But remyleination is defective
Pathophysiology: • During the acute stage: nerve conduction is blocked • Chronic disease: there is slow nerve conduction • Recurrent attacks → progressive neurological deficit
Clinically: • According to the site of nerve demylenation: • Vertigo (brain stem involvement) • Loss of sensation and movement in a limb (spinal nerves involvement) • Neuropsychiatry disorders
Degenerative diseases: • Parkinson’s disease • Huntington’s disease • Alzheimer disease
Parkinson disease • Definition: • Loss of pigmented neurons in substansia nigra • Grossly: • Pallor of substansia nigra in pons
Clinically: • Slowing of all voluntary movements • Tremors at rest that disappear on movement • Expressionless face • Rigidity in limbs and trunk and inability to initiate voluntary movements • Associated with increased incidence of dementia and depression
Huntington’s disease (HD) • Definition: • Autosomal dominant disorder characterized by atrophy of caudate nucleus with secondary ventricular dilatation
Atrophy of caudate nucleus Huntington disease (HD)
Microscopically: • Loss of small neurons in caudate nucleus • Clinically: • Age: 20-40 years • Chorea: sudden, unexpected and purposeless contractions of the proximal muscles • Changes in the personality with tendency to suicide and dementia
3- Alzheimer disease: • Risk factors: • Aging • Significant head trauma • Pathologically: • Accumulation of abnormal proteins intra and extra cellular • Senile plaques: core of amyloid surrounded by dendretic processes, microglial cells and astrocytes
Clinically: • Gradual onset, usually begins in the seventh or the eighth decades • Progressive memory impairment • Alteration in mood and behavior • Progressive disorientation • Aphasia (loss of language) • Within 5-10 years become mute and bedridden
CNS infectious disease are classified as: CNS INFECTIONS • Bacterial infection • Viral infection • Fungal infection • Toxoplasmosis infection • Prion infection
Acute purulent meningitis • Definition: • Purulent leptomeningeal inflammation due to bacteria • Causative bacteria: • Neonate: streptococci group-B and E-coli • Infants and children: Heamophilus infleuenzae • Young adults: Neisseria meningitides • Elderly: Streptoccocus pneumoniae
Clinical features: • Diffuse cerebral edema with increased risk of brain herniation • Headache, fever, nuchal rigidity, cloudy sensorium, coma and death • Hydrocephalus and cranial nerve impairment • Pathological features: • Neutrophilic infiltration of the meninges and extending to the cortex
Cerebral abscess • Hematogenous spread or direct spread from contiguous focci • Predisopsing conditions: • Acute bacterial endocarditis and chronic pulmonary abscess • Mastoiditis, paranasal sinusitis, acute otitis, open fractures and previous neurosurgery • Clinically: • Signs of increased intracranial pressure (headache, vomiting and papilledema) • Focal neurological deficits
BRAIN ABSCESS CT CERBERAL ABSCESS
Viralinfection of CNS Poliomyelitis: • Etiology & pathogenesis: • It is a viral infection of the nervous system by poliovirus, an entero-virus transmitted by fecal-oral route. • The virus enters the body through the intestine and multiplies in lymphoid tissues of oropharynx and intestine (incubation period) then invades the blood stream then it reach the brain and spinal cord. • Poliomyelitis is now rare because of routine immunization during childhood
c- Human Immunodeficiency Virus (HIV): • Cerebral involvement with HIV leads to AIDS dementia • Histologically : • Microglial nodules • Diagnostic giant cells • Spinal nerve involvement leads to vacuolar myelopathy
Primary manifestations of AIDS HIV encephalitis: multinucleated giant cells, gliosis and inflammation
Toxoplasmosis • Frequent in AIDS patient • Clinically: • Cerebral abscess with central necrosis and chronic inflammation
Prion disease of brain Creutzfedt-Jacob disease: • CNS disease caused by prion protein. The infectious agent has been called a prion. • A prion is defined as "small proteinaceous infectious particles". • Prion diseases are often called spongiform encephalopathies because of the post mortem appearance of the brain with large vacuoles in the cortex and cerebellum.
Pathological features: • Vacuolation of the gray matter in the cortex • Neuronal loss • Kuru plaques: these are deposites of amyloid • Clinically: • These cases rapidly progress to dementia and memory loss • Involuntary movments • Death within 6-12 months
Spongiform encephalopathies cause the brain tissue to become spongy and riddled with microscopic holes.
CLASSIFICATION Tumors of the CNS can be classified according to five fundamental origins: • The neuroectoderm (principally gliomas) • Mesenchymal structures (notably meningiomas and schwannomas, and primary brain lymphoma) • Tissues and cells that have been ectopically displaced intracranially during embryonic development • Retained embryonal structures • Metastases
Astrocytomas • The most common type of glioma • Accounts for 15-20% of primary brain tumors in the adult • The highly malignant form is called Glioblastoma Multiforme • Grossly: • The tumor has poorly defined margins and is infiltrative. • Most commonly found in cerebral hemispheres • Microscopically: • Uniform appearing nuclei occur in fibrillary background or matrix
Oligodendroglioma • Slowly growing tumour • Seizures and convulsions are the prominent 1st complaint
Ependymoma • Occurs most commonly in the 4th ventricle and in that location may lead to obstructive hydrocephalus. Ependymoma in 4th ventricle
II- Mesenchymal Origin Meningiomas “Tumor of the meninges" • Accounts for 20% of primary adult brain tumors • Occurs in later decades of life • Extremely slow growing and benign • Common presenting symptoms include headache, seizures and dementia
Metastatic Tumors • Account for 50% of all brain tumors in adults • In order of propensity to metastasize: lung, breast, melanoma, kidney, thyroid • Carcinomas of the GI tract, bladder, prostate, ovaries and uterus rarely go to brain • Grossly, tend to be round with well-defined borders. • Necrosis and hemorrhage are frequent. • Usually multiple
PERIPHERAL NERVE TUMORS • Schwannoma • Neurofibroma • Neurofibromatosis • Malignant schwannoma
SCHWANNOMA (NEUROLEMMOMA) • Definition: • A bengin tumor arising from Schwann (neurilemma) cells of the peripheral (cranial or spinal) nerves. • Gross: • A firm grayish capsulated mass at one side of the nerve. • The 8th cranial, acoustic nerve is one of the famous sites of schwannoma.
NEUROFIBROMA • Pathology: • Appears as rubbery expansion of the affected nerve, not demarcated from nerve • Neurofibroma has a significant risk of malignant transformation
NEUROFIBROMATOSIS(Von Recklinghausen's disease of nerves) • It is a familial disease (autosomal dominant inheritance) of two types: • Type I (NFI): It is characterized by • Multiple neurofibromatosis, mainly cutaneous • Acoustic schwannomas • Café au lait spots (hyperpigmented skin macules) • Eye lesions: • Optic nerve gliomas • Pigmented nodules of iris • Type II (NFII): • It resembles type I without eye affection
MALIGNANT SCHWANNOMA • Also called malignant peripheral nerve sheath tumor (MPNST) • It is a poorly differentiated spindle cell sarcoma of peripheral nerve. • The tumor may arise de novo or from malignant transformation of a neurofibroma or neurofibromatosis. • Occus in adults in the larger nerves of the trunk or proximal limbs as an uncapsulated fusiform enlargement of a nerve.
PERPHERAL NEURITIS • Definition: • This is inflammation and degeneration of peripheral nerves • Causes: • Diabetes mellitus is one of the most common causes of peripheral neuritis • Chronic alcoholism • Chronic lead poisoning • Beriberi
Leprosy • Toxemia as diphtheria • Acute post-infective polyneuritis; it follows infective diseases as measles and influenza or after vaccination and is thought to be allergic nature • Ischemia as in cases of polyarthritis nodosa • Traumatic as in cases of disc prolapse
Signs and symptoms • Deficits which include numbness, tremors and gait abnormality, loss of function, tiredness and heaviness. • Symptoms include tingling, pain, itching and pins and needles. • Pain can become intense enough to require use of opioid (narcotic) drugs (i.e., morphine).