Describe the functions of the four major lobes of the brain.
Frontal motor functions, behavior, emotions, higher intellect.
Parietal sensory functions.
Occipital visual center.
Temporal hearing and smelling.
Compare the functions of the midbrain, pons, and medulla oblongata with that of the cerebellum.
midbrain, pons, MO = myelinated nerve bundles connecting brain to SC
visual and auditory reflex, cardiac, vasomotor, respiratory centers
cerebellum = sensory input from SC and inner ear to cortex
balance, muscle tone, mvmt coordination
Describe the function of the spinal cord.
anterior horn >> peripheral nerves
- extensions of cortical and subcortical brain neurons
- carry motor impulses
posterior horn >> spinal ganglia
- carry sensory input
Describe the circulation of the cerebral spinal fluid.
Produced by choroid plexus in 3rd ventricles. Flows at low pressure lateral ventricles >> 3rd V >> 4th V >> lateral openings + median opening >> central canal of SC
List the main cells of the nervous system.
Glial cells (support) = astrocytes, oligodendroglia, microlia, ependymal
What are the most important diseases of the nervous system.
- Developmental and genetic diseases
- Diseases caused by trauma
- Circulatory disorders
- Infectious diseases
- Autoimmune diseases
- Metabolic and nutritional diseases
- Neurodegenerative diseases
- Brain tumors
What are the sites of brain herniation caused by intracranial hypertension?
Subfalcine herniation: cingulate gyrus protrudes beneath the falx cerebri
Transtentorial herniation: uncus protrudes tentorium cerebelli
Tonsillar hernation: cerebellar tonsils protruding into the foramen magnum
List the main dysraphic disorders of the CNS and describe their pathogenesis.
Incomplete fusion of the neural tube >> dysraphic disorders
anencephaly calvaria not formed
meningocele meninges protrude through defect
myelomeningocele protrusion of meninges + SC
spina bifida absence of vertebral arches
List the most important intracranial hemorrhages and describe their causes
Epidural hematoma usually from fracture, rupture of middle meningeal artery, lethal
Subdural hematoma tearing of thin-walled veins, accumulation over lateral hemispheres
Subarachnoid hemorrhages ruptured aneurysms, typically at the base of the brain, may be preceded by HTN
Intracerebral head trauma, stroke, hematologic disease
What is stroke?
or hemorrhagic (15%)
What is global cerebral ischemia, and what are its consequences?
Widespread atherosclerotic narrowing over entire cerebrovascular system
small lacunar infarcts >> multi-infarct dementia
What is the pathogenesis of "watershed infarcts" and laminar necrosis of the brain?
Watershed infarcts: hypoperfusion of the marginal zones between arteries (carotid and basilar)
Laminar necrosis: hypoperfusion of deeper zones of gray matter that receive blood from penetrating arteries
Describe the pathology of cerebral infarcts.
Thrombotic occlusion >> infarct
ischmic brain = liquefactive necrosis = encephalomalacia
- pale or hemorrhagic (more common with arterial thrombi)
infarct becomes pseudocyst
Correlate the pathology of intracerebral hemorrhage with the clinical features of the disease.
Most common site: basal ganglia
infarct >> pseudocysts with wall of hemosider laden macrophages
Basal ganglia: hemiplegia, hemiparesis
Cerebellar: nausea, vomiting, loss of balance, HA
What are the main pathologic findings after brain injury?
Concussion: transient LOC, NO significant brain changes
Contusion: bruise, hemorrhagic coup and contercoup lesion
Laceration: open trauma, neurologic deficit
Compare hyperextension and hyperflexion injuries of the cervical spine.
hyperextension - rupture of anterior spinal ligaments, compression of posterior SC
hyperflexion - compression of anterior SC
Compare bacterial and viral infections of the CNS
Spread: sepsis, bacteremia, septic emboli, open wounds, sinus infection, inner ear infection
*Strep pneumoniae causes most cases of bacterial meningitis in adults
Spread: hematogenous spread
*herpes = most common viral cause of localized encephalitis in the US
What are prions?
Prions = small infectious particles composed of proteins
*do not contain dna/rna
List the most important protozoal and fungal causes of opportunistic diseases of the CNS.
Protozoal: toxoplasmosis (neonates, AIDs)
Fungal: candida, aspergillus, cryptococcus (AIDs)
Compare the pathology of encephalitis and meningitis.
encephalitis = localized or diffuse inflammation of brain parenchyma
usually virus invades neural or glial cells
meningitis = inflammation of the meninges
Describe the features of neurosyphilis.
- usually presents as chronic meningitis
- meninges: infiltrated with lymphocytes and plasma cells (small BV)
- perivascular inflammation >> cortical ischemia
- tabes dorsalis = atrophy of dorsal (sensory columns)
What are the most important AIDS-related CNS lesions?
HIV infects macrophages and T lymphocytes, and these cells "import" the virus to the CNS
What is MS?
An autoimmune demyelinating disease
W > M, 20-45 y/o
Correlate the pathologic features of MS with the clinical signs and symptoms of this disease.
Presence of IgG oligoclonal bands >> responding to antigen?
- Typically involves white matter >> both sensory and motor abnormalities
- Periventricular plaques (lateral hemispheres)
- early lesions = lymphocytes and foamy macrophages
- late lesions = demyelinated axons and reactive astrocytes (gliosis)
How do inborn errors of metabolism affect the CNS?
Tay-Sachs = deficiency of hexosaminidase A >> accumulation of gangliosides
Neimann-Pick = deficiency of sphingomyelinase >> accumulation of sphingomyelin >> atrophy
What is the cause and what are the signs of Wernicke-Korsakoff syndrome?
Wernicke's = ocular, gait, mental
Korsakoff's = amnesia, confabulation
hypothalamus, periaqueductal region (midbrain), mamillary bodies
How does alcohol affect the brain?
- Dementia (atrophy of gyri)
- Dilated ventricle
- Wernicke-Korsakoff syndrome
- Pontine myelinolysis (r/t vigorous Na correction)
- Subdural hematoma
- Cerebellar atrophy
What are the most important neurodegenerative diseases?
Alzheimers >> frontal/occipital cortex
Huntingtons >> frontal cortex and basal ganglia
Parkinsons >> substantia nigra
ALS >> motor neurons in anterior horn of SC, brainstem, frontal cortex
What is Alzheimer's disease, and how is it diagnosed?
Clinical diagnosis based on demonstration of progressive dementia (excluding other causes)
Describe the macroscopic and microscopic pathologic findings in Alzheimer's disease.
Chromosome's 21 &19 >> APOE4 (19) mutation >> beta amyloid= extracellular
hyperphosphorylation of tau protein >> axonal microtubule binding = intracellular
Brain is atrophic, neuritic plaques, neurofibrillary tangles, deposition of amyloid (see with silver impregnation and congo red stain)